Author name code: fletcher ADS astronomy entries on 2022-09-14 author:"Fletcher, Lyndsay" ------------------------------------------------------------------------ Title: Flare Kernels May be Smaller than You Think: Modelling the Radiative Response of Chromospheric Plasma Adjacent to a Solar Flare Authors: Osborne, Christopher M. J.; Fletcher, Lyndsay Bibcode: 2022arXiv220903238O Altcode: Numerical models of solar flares typically focus on the behaviour of directly-heated flare models, adopting magnetic field- aligned, plane-parallel methodologies. With high spatial- and spectral-resolution ground-based optical observations of flares, it is essential also to understand the response of the plasma surrounding these strongly heated volumes. We investigate the effects of the extreme radiation field produced by a heated column of flare plasma on an adjacent slab of chromospheric plasma, using a two-dimensional radiative transfer model and considering the time-dependent solution to the atomic level populations and electron density throughout this model. The outgoing spectra of H$\alpha$ and Ca II 854.2 nm synthesised from our slab show significant spatial-, time-, and wavelength-dependent variations (both enhancements and reductions) in the line cores, extending on order 1 Mm into the non-flaring slab due to the incident transverse radiation field from the flaring boundary. This may lead to significant overestimates of the sizes of directly-heated flare kernels, if line-core observations are used. However, the radiation field alone is insufficient to drive any significant changes in continuum intensity, due to the typical photospheric depths at which they forms, so continuum sources will not have an apparent increase in size. We show that the line formation regions near the flaring boundary can be driven upwards in altitude by over 1 Mm despite the primary thermodynamic parameters (other than electron density) being held horizontally uniform. This work shows that in simple models these effects are significant and should be considered further in future flare modelling and interpretation. Title: Fast prograde coronal flows in solar active regions Authors: Hudson, Hugh S.; Mulay, Sargam M.; Fletcher, Lyndsay; Docherty, Jennifer; Fitzpatrick, Jimmy; Pike, Eleanor; Strong, Morven; Chamberlin, Phillip C.; Woods, Thomas N. Bibcode: 2022MNRAS.515L..84H Altcode: 2022MNRAS.tmpL..75H; 2022arXiv220713461H We report the discovery and characterization of high-speed (>100 km s-1) horizontal flows in solar active regions, making use of the Sun-as-a-star spectroscopy in the range 5-105 nm provided by the EVE (Extreme Ultraviolet Variability Experiment) spectrometers on the Solar Dynamics Observatory. These apparent flows are persistent on time-scales of days, and are well observed in lines of Mg X, Si XII, and Fe XVI for example. They are prograde, as evidenced directly by blueshifts/redshifts peaking at the east/west limb passages of isolated active regions. The high-speed flow behaviour does not depend upon active-region latitude or solar cycle, with similar behaviour in Cycles 24 and 25. Title: Development of Integral Field Spectrographs to Revolutionize Spectroscopic Observations of Solar Flares and other Energetic Solar Eruptions Authors: Lin, Haosheng; Anan, Tetsu; Cauzzi, Gianna; Fletcher, Lyndsay; Huang, Pei; Kowalski, Adam; Kramar, Maxim; Qiu, Jiong; Samra, Jenna; Spittler, Constance; Sukegawa, Takashi; Wirth, Gregory Bibcode: 2022arXiv220900788L Altcode: The Sun's proximity offers us a unique opportunity to study in detail the physical processes on a star's surface; however, the highly dynamic nature of the stellar surface -- in particular, energetic eruptions such as flares and coronal mass ejections -- presents tremendous observational challenges. Spectroscopy probes the physical state of the solar atmosphere, but conventional scanning spectrographs and spectrometers are unable to capture the full evolutionary history of these dynamic events with a sufficiently wide field of view and high spatial, spectral, and temporal resolution. Resolving the physics of the dynamic sun requires gathering simultaneous spectra across a contiguous area over the full duration of these events, a goal now tantalizingly close to achievable with continued investment in developing powerful new Integral Field Spectrographs to serve as the foundation of both future ground- and space-based missions. This technology promises to revolutionize our ability to study solar flares and CMEs, addressing NASA's strategic objective to "understand the Sun, solar system, and universe." Since such events generate electromagnetic radiation and high-energy particles that disrupt terrestrial electric infrastructure, this investment not only advances humanity's scientific endeavors but also enhances our space weather forecasting capability to protect against threats to our technology-reliant civilization. Title: Ice Giant Atmospheric Structures from Spitzer and How the James Webb Space Telescope will Advance Our Understanding Authors: Rowe-Gurney, N.; Fletcher, L. N.; Orton, G. S.; Roman, M. T.; Sinclair, J. A.; Moses, J. I.; Irwin, P. G. J.; Milam, S. N.; Hammel, H. B. Bibcode: 2022LPICo2686.4045R Altcode: NASA's IRS acquired mid-infrared disc-averaged spectra of Uranus & Neptune 2004-2007. We analyze the differences in temperature & composition between the separate hemispheres to shed light on the variability of stratospheres and upper tropospheres. Title: Hazy Blue Worlds: A Holistic Aerosol Model for Uranus and Neptune, Including Dark Spots Authors: Irwin, P. G. J.; Teanby, N. A.; Fletcher, L. N.; Toledo, D.; Orton, G. S.; Wong, M. H.; Roman, M. T.; Pérez-Hoyos, S.; James, A.; Dobinson, J. Bibcode: 2022JGRE..12707189I Altcode: 2022arXiv220104516I We present a reanalysis (using the Minnaert limb-darkening approximation) of visible/near-infrared (0.3-2.5 μm) observations of Uranus and Neptune made by several instruments. We find a common model of the vertical aerosol distribution i.e., consistent with the observed reflectivity spectra of both planets, consisting of: (a) a deep aerosol layer with a base pressure >5-7 bar, assumed to be composed of a mixture of H2S ice and photochemical haze; (b) a layer of photochemical haze/ice, coincident with a layer of high static stability at the methane condensation level at 1-2 bar; and (c) an extended layer of photochemical haze, likely mostly of the same composition as the 1-2-bar layer, extending from this level up through to the stratosphere, where the photochemical haze particles are thought to be produced. For Neptune, we find that we also need to add a thin layer of micron-sized methane ice particles at ∼0.2 bar to explain the enhanced reflection at longer methane-absorbing wavelengths. We suggest that methane condensing onto the haze particles at the base of the 1-2-bar aerosol layer forms ice/haze particles that grow very quickly to large size and immediately "snow out" (as predicted by Carlson et al. (1988), https://doi.org/10.1175/1520-0469(1988)045<2066:CMOTGP>2.0.CO2), re-evaporating at deeper levels to release their core haze particles to act as condensation nuclei for H2S ice formation. In addition, we find that the spectral characteristics of "dark spots", such as the Voyager-2/ISS Great Dark Spot and the HST/WFC3 NDS-2018, are well modelled by a darkening or possibly clearing of the deep aerosol layer only. Title: First high resolution interferometric observation of a solar prominence with ALMA Authors: Labrosse, Nicolas; Rodger, Andrew S.; Radziszewski, Krzysztof; Rudawy, Paweł; Antolin, Patrick; Fletcher, Lyndsay; Levens, Peter J.; Peat, Aaron W.; Schmieder, Brigitte; Simões, Paulo J. A. Bibcode: 2022MNRAS.513L..30L Altcode: 2022arXiv220212434L; 2022MNRAS.tmpL..22L We present the first observation of a solar prominence at 84 - 116 GHz using the high resolution interferometric imaging of ALMA. Simultaneous observations in Hα from Białkaw Observatory and with SDO/AIA reveal similar prominence morphology to the ALMA observation. The contribution functions of 3 mm and Hα emission are shown to have significant overlap across a range of gas pressures. We estimate the maximum millimetre-continuum optical thickness to be τ3mm ≍ 2, and the brightness temperature from the observed Hα intensity. The brightness temperature measured by ALMA is ~6000 - 7000 K in the prominence spine, which correlates well with the estimated brightness temperature for a kinetic temperature of 8000 K. Title: Compositional Mapping of Ganymede with VLT/SPHERE Using Markov Chain Monte Carlo Spectral Analysis Authors: King, O. R. T.; Fletcher, L. N. Bibcode: 2022LPICo2678.1461K Altcode: Infrared spectral observations of Ganymede from VLT/SPHERE have been analysed using a Monte Carlo model to calculate compositional abundances and uncertainties. Title: Probing the Physics of the Solar Atmosphere with the Multi-slit Solar Explorer (MUSE). II. Flares and Eruptions Authors: Cheung, Mark C. M.; Martínez-Sykora, Juan; Testa, Paola; De Pontieu, Bart; Chintzoglou, Georgios; Rempel, Matthias; Polito, Vanessa; Kerr, Graham S.; Reeves, Katharine K.; Fletcher, Lyndsay; Jin, Meng; Nóbrega-Siverio, Daniel; Danilovic, Sanja; Antolin, Patrick; Allred, Joel; Hansteen, Viggo; Ugarte-Urra, Ignacio; DeLuca, Edward; Longcope, Dana; Takasao, Shinsuke; DeRosa, Marc L.; Boerner, Paul; Jaeggli, Sarah; Nitta, Nariaki V.; Daw, Adrian; Carlsson, Mats; Golub, Leon; The Bibcode: 2022ApJ...926...53C Altcode: 2021arXiv210615591C Current state-of-the-art spectrographs cannot resolve the fundamental spatial (subarcseconds) and temporal (less than a few tens of seconds) scales of the coronal dynamics of solar flares and eruptive phenomena. The highest-resolution coronal data to date are based on imaging, which is blind to many of the processes that drive coronal energetics and dynamics. As shown by the Interface Region Imaging Spectrograph for the low solar atmosphere, we need high-resolution spectroscopic measurements with simultaneous imaging to understand the dominant processes. In this paper: (1) we introduce the Multi-slit Solar Explorer (MUSE), a spaceborne observatory to fill this observational gap by providing high-cadence (<20 s), subarcsecond-resolution spectroscopic rasters over an active region size of the solar transition region and corona; (2) using advanced numerical models, we demonstrate the unique diagnostic capabilities of MUSE for exploring solar coronal dynamics and for constraining and discriminating models of solar flares and eruptions; (3) we discuss the key contributions MUSE would make in addressing the science objectives of the Next Generation Solar Physics Mission (NGSPM), and how MUSE, the high-throughput Extreme Ultraviolet Solar Telescope, and the Daniel K Inouye Solar Telescope (and other ground-based observatories) can operate as a distributed implementation of the NGSPM. This is a companion paper to De Pontieu et al., which focuses on investigating coronal heating with MUSE. Title: Probing the Physics of the Solar Atmosphere with the Multi-slit Solar Explorer (MUSE): II. Flares and Eruptions Authors: Cheung, Chun Ming Mark; Martinez-Sykora, Juan; Testa, Paola; De Pontieu, Bart; Chintzoglou, Georgios; Rempel, Matthias; Polito, Vanessa; Kerr, Graham; Reeves, Katharine; Fletcher, Lyndsay; Jin, Meng; Nobrega, Daniel; Danilovic, Sanja; Antolin, Patrick; Allred, Joel; Hansteen, Viggo; Ugarte-Urra, Ignacio; DeLuca, Edward; Longcope, Dana; Takasao, Shinsuke; DeRosa, Marc; Boerner, Paul; Jaeggli, Sarah; Nitta, Nariaki; Daw, Adrian; Carlsson, Mats; Golub, Leon Bibcode: 2021AGUFMSH51A..08C Altcode: Current state-of-the-art spectrographs cannot resolve the fundamental spatial (sub-arcseconds) and temporal scales (less than a few tens of seconds) of the coronal dynamics of solar flares and eruptive phenomena. The highest resolution coronal data to date are based on imaging, which is blind to many of the processes that drive coronal energetics and dynamics. As shown by IRIS for the low solar atmosphere, we need high-resolution spectroscopic measurements with simultaneous imaging to understand the dominant processes. In this paper: (1) we introduce the Multi-slit Solar Explorer (MUSE), a spaceborne observatory to fill this observational gap by providing high-cadence (<20 s), sub-arcsecond resolution spectroscopic rasters over an active region size of the solar transition region and corona; (2) using advanced numerical models, we demonstrate the unique diagnostic capabilities of MUSE for exploring solar coronal dynamics, and for constraining and discriminating models of solar flares and eruptions; (3) we discuss the key contributions MUSE would make in addressing the science objectives of the Next Generation Solar Physics Mission (NGSPM), and how MUSE, the high-throughput EUV Solar Telescope (EUVST) and the Daniel K Inouye Solar Telescope (and other ground-based observatories) can operate as a distributed implementation of the NGSPM. This is a companion paper to De Pontieu et al. (2021, also submitted to SH-17), which focuses on investigating coronal heating with MUSE. Title: Hot onsets of solar flares Authors: Hudson, Hugh; Fletcher, Lyndsay; Hannah, Iain; Hayes, Laura; Simoes, Paulo Bibcode: 2021AGUFMSH22B..02H Altcode: The GOES/XRS data show low-level soft X-ray emissions prior to a flare in a "hot onset" precursor of the main flare development (2021MNRAS.501.1273H). This phenomenon provides clear evidence for energy release not identifiable with the impulsive phase, and apparently not mediated by non-thermal particles. The hot onset phase may last for tens of seconds to minutes, characterized by gradual and roughly linear growth of emission measure at characteristic isothermal temperatures of 10-15 MK and no clear pattern of temperature increase in the sense of dT/dt > 0. The figure shows an example of this behavior, from SOL2004-02-26 (X1.1). The newer GOES-R data also show this effect, providing higher time resolution (1 s) and better noise properties, although with higher background levels. Hot onsets occur in most if not all flares, but their properties do not appear to provide any guidance towards the magnitude of the flare that follows. Title: Microwave observations reveal the deep extent and structure of Jupiter’s atmospheric vortices Authors: Bolton, S. J.; Levin, S. M.; Guillot, T.; Li, C.; Kaspi, Y.; Orton, G.; Wong, M. H.; Oyafuso, F.; Allison, M.; Arballo, J.; Atreya, S.; Becker, H. N.; Bloxham, J.; Brown, S. T.; Fletcher, L. N.; Galanti, E.; Gulkis, S.; Janssen, M.; Ingersoll, A.; Lunine, J. L.; Misra, S.; Steffes, P.; Stevenson, D.; Waite, J. H.; Yadav, R. K.; Zhang, Z. Bibcode: 2021Sci...374..968B Altcode: Jupiter’s atmosphere has a system of zones and belts punctuated by small and large vortices, the largest being the Great Red Spot. How these features change with depth is unknown, with theories of their structure ranging from shallow meteorological features to surface expressions of deep-seated convection. We present observations of atmospheric vortices using the Juno spacecraft’s Microwave Radiometer. We found vortex roots that extend deeper than the altitude at which water is expected to condense, and we identified density inversion layers. Our results constrain the three-dimensional structure of Jupiter’s vortices and their extension below the clouds. Title: The high-energy Sun - probing the origins of particle acceleration on our nearest star Authors: Matthews, S. A.; Reid, H. A. S.; Baker, D.; Bloomfield, D. S.; Browning, P. K.; Calcines, A.; Del Zanna, G.; Erdelyi, R.; Fletcher, L.; Hannah, I. G.; Jeffrey, N.; Klein, L.; Krucker, S.; Kontar, E.; Long, D. M.; MacKinnon, A.; Mann, G.; Mathioudakis, M.; Milligan, R.; Nakariakov, V. M.; Pesce-Rollins, M.; Shih, A. Y.; Smith, D.; Veronig, A.; Vilmer, N. Bibcode: 2021ExA...tmp..135M Altcode: As a frequent and energetic particle accelerator, our Sun provides us with an excellent astrophysical laboratory for understanding the fundamental process of particle acceleration. The exploitation of radiative diagnostics from electrons has shown that acceleration operates on sub-second time scales in a complex magnetic environment, where direct electric fields, wave turbulence, and shock waves all must contribute, although precise details are severely lacking. Ions were assumed to be accelerated in a similar manner to electrons, but γ-ray imaging confirmed that emission sources are spatially separated from X-ray sources, suggesting distinctly different acceleration mechanisms. Current X-ray and γ-ray spectroscopy provides only a basic understanding of accelerated particle spectra and the total energy budgets are therefore poorly constrained. Additionally, the recent detection of relativistic ion signatures lasting many hours, without an electron counterpart, is an enigma. We propose a single platform to directly measure the physical conditions present in the energy release sites and the environment in which the particles propagate and deposit their energy. To address this fundamental issue, we set out a suite of dedicated instruments that will probe both electrons and ions simultaneously to observe; high (seconds) temporal resolution photon spectra (4 keV - 150 MeV) with simultaneous imaging (1 keV - 30 MeV), polarization measurements (5-1000 keV) and high spatial and temporal resolution imaging spectroscopy in the UV/EUV/SXR (soft X-ray) regimes. These instruments will observe the broad range of radiative signatures produced in the solar atmosphere by accelerated particles. Title: On the importance of Ca II photoionization by the hydrogen lyman transitions in solar flare models Authors: Osborne, C. M. J.; Heinzel, P.; Kašparová, J.; Fletcher, L. Bibcode: 2021MNRAS.507.1972O Altcode: 2021MNRAS.tmp.1947O; 2021arXiv210711145O The forward fitting of solar flare observations with radiation-hydrodynamic simulations is a common technique for learning about energy deposition and atmospheric evolution during these explosive events. A frequent spectral line choice for this process is Ca II 854.2 nm due to its formation in the chromosphere and substantial variability. It is important to ensure that this line is accurately modelled to obtain the correct interpretation of observations. Here, we investigate the importance of photoionization of Ca II to Ca III by the hydrogen Lyman transitions, whilst the Lyman continuum is typically considered in this context in simulations, the associated bound-bound transitions are not. This investigation uses two RADYN flare simulations and reprocesses the radiative transfer using the Lightweaver framework which accounts for the overlapping of all active transitions. The Ca II 854.2 nm line profiles are found to vary significantly due to photoionization by the Lyman lines, showing notably different shapes and even reversed asymmetries. Finally, we investigate to what extent these effects modify the energy balance of the simulation and the implications on future radiation-hydrodynamic simulations. There is found to be a 10-15 per cent change in detailed optically thick radiative losses from considering these photoionization effects on the calcium lines in the two simulations presented, demonstrating the importance of considering these effects in a self-consistent way. Title: Jupiter's Temperate Belt/Zone Contrasts Revealed at Depth by Juno Microwave Observations Authors: Fletcher, L. N.; Oyafuso, F. A.; Allison, M.; Ingersoll, A.; Li, L.; Kaspi, Y.; Galanti, E.; Wong, M. H.; Orton, G. S.; Duer, K.; Zhang, Z.; Li, C.; Guillot, T.; Levin, S. M.; Bolton, S. Bibcode: 2021JGRE..12606858F Altcode: 2021arXiv211014620F Juno microwave radiometer (MWR) observations of Jupiter's midlatitudes reveal a strong correlation between brightness temperature contrasts and zonal winds, confirming that the banded structure extends throughout the troposphere. However, the microwave brightness gradient is observed to change sign with depth: the belts are microwave-bright in the p<5 bar range and microwave-dark in the p>10 bar range. The transition level (which we call the "jovicline") is evident in the MWR 11.5 cm channel, which samples the 5-14 bar range when using the limb-darkening at all emission angles. The transition is located between 4 and 10 bars, and implies that belts change with depth from being NH3-depleted to NH3-enriched, or from physically warm to physically cool, or more likely a combination of both. The change in character occurs near the statically stable layer associated with water condensation. The implications of the transition are discussed in terms of ammonia redistribution via meridional circulation cells with opposing flows above and below the water condensation layer, and in terms of the "mushball" precipitation model, which predicts steeper vertical ammonia gradients in the belts versus the zones. We show via the moist thermal wind equation that both the temperature and ammonia interpretations can lead to vertical shear on the zonal winds, but the shear is ∼50× weaker if only NH3 gradients are considered. Conversely, if MWR observations are associated with kinetic temperature gradients then it would produce zonal winds that increase in strength down to the "jovicline", consistent with Galileo probe measurements; then decay slowly at higher pressures. Title: Demonstration of an x-ray Raman spectroscopy setup to study warm dense carbon at the high energy density instrument of European XFEL Authors: Voigt, K.; Zhang, M.; Ramakrishna, K.; Amouretti, A.; Appel, K.; Brambrink, E.; Cerantola, V.; Chekrygina, D.; Döppner, T.; Falcone, R. W.; Falk, K.; Fletcher, L. B.; Gericke, D. O.; Göde, S.; Harmand, M.; Hartley, N. J.; Hau-Riege, S. P.; Huang, L. G.; Humphries, O. S.; Lokamani, M.; Makita, M.; Pelka, A.; Prescher, C.; Schuster, A. K.; Šmíd, M.; Toncian, T.; Vorberger, J.; Zastrau, U.; Preston, T. R.; Kraus, D. Bibcode: 2021PhPl...28h2701V Altcode: We present a proof-of-principle study demonstrating x-ray Raman Spectroscopy (XRS) from carbon samples at ambient conditions in conjunction with other common diagnostics to study warm dense matter, performed at the high energy density scientific instrument of the European x-ray Free Electron Laser (European XFEL). We obtain sufficient spectral resolution to identify the local structure and chemical bonding of diamond and graphite samples, using highly annealed pyrolytic graphite spectrometers. Due to the high crystal reflectivity and XFEL brightness, we obtain signal strengths that will enable accurate XRS measurements in upcoming pump-probe experiments with a high repetition-rate, where the samples will be pumped with high-power lasers. Molecular dynamics simulations based on density functional theory together with XRS simulations demonstrate the potential of this technique and show predictions for high-energy-density conditions. Our setup allows simultaneous implementation of several different diagnostic methods to reduce ambiguities in the analysis of the experimental results, which, for warm dense matter, often relies on simplifying model assumptions. The promising capabilities demonstrated here provide unprecedented insights into chemical and structural dynamics in warm dense matter states of light elements, including conditions similar to the interiors of planets, low-mass stars, and other celestial bodies. Title: VizieR Online Data Catalog: TEXES spectra of Saturn from February 03 2013 (Blake+, 2021) Authors: Blake, J. S. D.; Fletcher, L. N.; Greathouse, T. K.; Orton, G. S.; Melin, H.; Roman, M. T.; Antunano, A.; Donnelly, P. T.; Rowe-Gurney, N.; King, O. Bibcode: 2021yCat..36530066B Altcode: We observed Saturn in the N-band 8.6 m region for one night in February 2013, using the high spectral resolution of the TEXES instrument and the 3-meter diameter mirror of NASA's IRTF.

TEXES spectra of Saturn from February 03 2013.

(2 data files). Title: In Situ exploration of the giant planets Authors: Mousis, O.; Atkinson, D. H.; Ambrosi, R.; Atreya, S.; Banfield, D.; Barabash, S.; Blanc, M.; Cavalié, T.; Coustenis, A.; Deleuil, M.; Durry, G.; Ferri, F.; Fletcher, L. N.; Fouchet, T.; Guillot, T.; Hartogh, P.; Hueso, R.; Hofstadter, M.; Lebreton, J. -P.; Mandt, K. E.; Rauer, H.; Rannou, P.; Renard, J. -B.; Sánchez-Lavega, A.; Sayanagi, K. M.; Simon, A. A.; Spilker, T.; Venkatapathy, E.; Waite, J. H.; Wurz, P. Bibcode: 2021ExA...tmp...96M Altcode: Remote sensing observations suffer significant limitations when used to study the bulk atmospheric composition of the giant planets of our Solar System. This impacts our knowledge of the formation of these planets and the physics of their atmospheres. A remarkable example of the superiority of in situ probe measurements was illustrated by the exploration of Jupiter, where key measurements such as the determination of the noble gases' abundances and the precise measurement of the helium mixing ratio were only made available through in situ measurements by the Galileo probe. Here we describe the main scientific goals to be addressed by the future in situ exploration of Saturn, Uranus, and Neptune, placing the Galileo probe exploration of Jupiter in a broader context. An atmospheric entry probe targeting the 10-bar level would yield insight into two broad themes: i) the formation history of the giant planets and that of the Solar System, and ii) the processes at play in planetary atmospheres. The probe would descend under parachute to measure composition, structure, and dynamics, with data returned to Earth using a Carrier Relay Spacecraft as a relay station. An atmospheric probe could represent a significant ESA contribution to a future NASA New Frontiers or flagship mission to be launched toward Saturn, Uranus, and/or Neptune. Title: Characterizing a "Solar FRB" Authors: Hudson, H.; Briggs, M.; Chitta, L.; Fletcher, L.; Gary, D.; Monstein, C.; Nimmo, K.; Saint-Hilaire, P.; White, S. Bibcode: 2021AAS...23812716H Altcode: A remarkable solar microwave (1.4 GHz) burst, SOL2019-05-06T17:47:35.385, has been reported by the STARE2 fast cosmic transient survey (Bochenek et al., 2020). Its behavior resembles that of the Fast Radio Burst (FRB) extragalactic events in having a relatively broad spectral bandwidth and brief (19-msec) duration. It also had no measureable dispersion. The associated flare, GOES class C1, had a relatively hard X-ray spectrum as observed by Fermi/GBM, but no temporal association at the msec time scale suggested by the microwaves. Although msec variability in the microwave domain has been known to solar radio astronomy since the 1970s, the brightness and isolation of this event (both spatial and temporal) suggests novelty. Accordingly we survey the available correlative data from many sources and discuss possible interpretations in terms of type III-like behavior, electron cyclotron masering, and gyrosynchrotron emission. We note that the radio data (e-Callisto and EOVSA) revealed abundant type III activity in the vicinity, and the related flares as observed by GOES had exceptionally short time scales, suggesting burst origins in the lower solar atmosphere. Title: Evidence of chromospheric molecular hydrogen emission in a solar flare observed by the IRIS satellite Authors: Mulay, Sargam M.; Fletcher, Lyndsay Bibcode: 2021MNRAS.504.2842M Altcode: 2021arXiv210203329M; 2021MNRAS.tmp..434M We have carried out the first comprehensive investigation of enhanced line emission from molecular hydrogen, H2 at 1333.79 Å, observed at flare ribbons in SOL2014-04-18T13:03. The cool H2 emission is known to be fluorescently excited by Si IV 1402.77 Å UV radiation and provides a unique view of the temperature minimum region (TMR). Strong H2 emission was observed when the Si IV 1402.77 Å emission was bright during the flare impulsive phase and gradual decay phase, but it dimmed during the GOES peak. H2 line broadening showed non-thermal speeds in the range 7-18 $\rm {km\,s}^{-1}$, possibly corresponding to turbulent plasma flows. Small red (blue) shifts, up to 1.8 (4.9) $\rm {km\,s}^{-1}$ were measured. The intensity ratio of Si IV 1393.76 Å and Si IV 1402.77 Å confirmed that plasma was optically thin to Si IV (where the ratio = 2) during the impulsive phase of the flare in locations where strong H2 emission was observed. In contrast, the ratio differs from optically thin value of 2 in parts of ribbons, indicating a role for opacity effects. A strong spatial and temporal correlation between H2 and Si IV emission was evident supporting the notion that fluorescent excitation is responsible. Title: The science enabled by a dedicated solar system space telescope Authors: Young, Cindy; Wong, M. H.; Sayanagi, K. M.; Curry, S.; Jessup, K. L.; Becker, T.; Hendrix, A.; Chanover, N.; Milam, S.; Holler, B. J.; Holsclaw, G.; Peralta, J.; Clarke, J.; Spencer, J.; Kelley, M. S. P.; Luhmann, J.; MacDonnell, D.; Vervack, R. J., Jr.; Rutherford, K.; Fletcher, L. N.; de Pater, I.; Vilas, F.; Feaga, L.; Siegmund, O.; Bell, J.; Delory, G.; Pitman, J.; Greathouse, T.; Wishnow, E.; Schneider, N.; Lillis, R.; Colwell, J.; Bowman, L.; Lopes, R. M. C.; McGrath, M.; Marchis, F.; Cartwright, R.; Poston, M. J. Bibcode: 2021BAAS...53d.232Y Altcode: 2021psad.rept..232Y We advocate for a large/medium-class space telescope dedicated to planetary science to transform our understanding of time-dependent phenomena & enable a comprehensive survey & spectral characterization of minor bodies across the solar system. The key science questions & themes presented here cannot fully be addressed using astrophysical assets. Title: On the clouds and ammonia in Jupiter's upper troposphere from Juno JIRAM reflectivity observations Authors: Grassi, Davide; Mura, A.; Sindoni, G.; Adriani, A.; Atreya, S. K.; Filacchione, G.; Fletcher, L. N.; Lunine, J. I.; Moriconi, M. L.; Noschese, R.; Orton, G. S.; Plainaki, C.; Sordini, R.; Tosi, F.; Turrini, D.; Olivieri, A.; Eichstädt, G.; Hansen, C. J.; Melin, H.; Altieri, F.; Cicchetti, A.; Dinelli, B. M.; Migliorini, A.; Piccioni, G.; Stefani, S.; Bolton, S. J. Bibcode: 2021MNRAS.503.4892G Altcode: 2021MNRAS.tmp..746G We analyse spectra measured by the Jovian Infrared Auroral Mapper (JIRAM, a payload element of the NASA Juno mission) in the 3150-4910 cm-1 (2.0-3.2 μm) range during the perijiove passage of 2016 August. Despite modelling uncertainties, the quality and the relative uniformity of the data set allow us to determine several parameters characterizing the Jupiter's upper troposphere in the latitude range of 35°S-30°N. Ammonia relative humidity at 500 millibars varies between 5 per cent to supersaturation beyond 100 per cent for about 3 per cent of the processed spectra. Ammonia appears depleted over belts and relatively enhanced over zones. Local variations of ammonia, arguably associated with local dynamics, are found to occur in several locations on the planet (Oval BA, South Equatorial Belt). Cloud altitude, defined as the level where aerosol opacity reaches unit value at 3650 cm-1 (2.74 μm), is maximum over the Great Red Spot (>20 km above the 1 bar level) and the zones (15 km), while it decreases over the belts and towards higher latitudes. The aerosol opacity scale height suggests more compact clouds over zones and more diffuse clouds over belts. The integrated opacity of clouds above the 1.3-bar pressure level is found to be minimum in regions where thermal emission of the deeper atmosphere is maximum. The opacity of tropospheric haze above the 200-mbar level also increases over zones. Our results are consistent with a Hadley-type circulation scheme previously proposed in literature for belts and zones, with clear hemisphere asymmetries in cloud and haze. Title: The effect of a solar flare on chromospheric oscillations Authors: Millar, David C. L.; Fletcher, Lyndsay; Milligan, Ryan O. Bibcode: 2021MNRAS.503.2444M Altcode: 2021MNRAS.tmp..652M; 2020arXiv200710301M Oscillations in the solar atmosphere have long been observed both in quiet conditions and during solar flares. The chromosphere is known for its 3-min signals, which are strong over sunspot umbrae, and have periods determined by the chromosphere's acoustic cut-off frequency. A small number of observations have shown the chromospheric signals to be affected by energetic events such as solar flares, however the link between flare activity and these oscillations remains unclear. In this work, we present evidence of changes to the oscillatory structure of the chromosphere over a sunspot which occurs during the impulsive phase of an M1 flare. Using imaging data from the CRISP instrument across the H α and Ca II 8542 Å spectral lines, we employed a method of fitting models to power spectra to produce maps of where there is evidence of oscillatory signals above a red-noise background. Comparing results taken before and after the impulsive phase of the flare, we found that the oscillatory signals taken after the start of the flare differ in two ways: the locations of oscillatory signals had changed and the typical periods of the oscillations had tended to increase (in some cases increasing from <100 s to ∼200 s). Both of these results can be explained by a restructuring of the magnetic field in the chromosphere during the flare activity, which is backed up by images of coronal loops showing clear changes to magnetic connectivity. These results represent one of the many ways that active regions can be affected by solar flares. Title: Critical Science Plan for the Daniel K. Inouye Solar Telescope (DKIST) Authors: Rast, Mark P.; Bello González, Nazaret; Bellot Rubio, Luis; Cao, Wenda; Cauzzi, Gianna; Deluca, Edward; de Pontieu, Bart; Fletcher, Lyndsay; Gibson, Sarah E.; Judge, Philip G.; Katsukawa, Yukio; Kazachenko, Maria D.; Khomenko, Elena; Landi, Enrico; Martínez Pillet, Valentín; Petrie, Gordon J. D.; Qiu, Jiong; Rachmeler, Laurel A.; Rempel, Matthias; Schmidt, Wolfgang; Scullion, Eamon; Sun, Xudong; Welsch, Brian T.; Andretta, Vincenzo; Antolin, Patrick; Ayres, Thomas R.; Balasubramaniam, K. S.; Ballai, Istvan; Berger, Thomas E.; Bradshaw, Stephen J.; Campbell, Ryan J.; Carlsson, Mats; Casini, Roberto; Centeno, Rebecca; Cranmer, Steven R.; Criscuoli, Serena; Deforest, Craig; Deng, Yuanyong; Erdélyi, Robertus; Fedun, Viktor; Fischer, Catherine E.; González Manrique, Sergio J.; Hahn, Michael; Harra, Louise; Henriques, Vasco M. J.; Hurlburt, Neal E.; Jaeggli, Sarah; Jafarzadeh, Shahin; Jain, Rekha; Jefferies, Stuart M.; Keys, Peter H.; Kowalski, Adam F.; Kuckein, Christoph; Kuhn, Jeffrey R.; Kuridze, David; Liu, Jiajia; Liu, Wei; Longcope, Dana; Mathioudakis, Mihalis; McAteer, R. T. James; McIntosh, Scott W.; McKenzie, David E.; Miralles, Mari Paz; Morton, Richard J.; Muglach, Karin; Nelson, Chris J.; Panesar, Navdeep K.; Parenti, Susanna; Parnell, Clare E.; Poduval, Bala; Reardon, Kevin P.; Reep, Jeffrey W.; Schad, Thomas A.; Schmit, Donald; Sharma, Rahul; Socas-Navarro, Hector; Srivastava, Abhishek K.; Sterling, Alphonse C.; Suematsu, Yoshinori; Tarr, Lucas A.; Tiwari, Sanjiv; Tritschler, Alexandra; Verth, Gary; Vourlidas, Angelos; Wang, Haimin; Wang, Yi-Ming; NSO and DKIST Project; DKIST Instrument Scientists; DKIST Science Working Group; DKIST Critical Science Plan Community Bibcode: 2021SoPh..296...70R Altcode: 2020arXiv200808203R The National Science Foundation's Daniel K. Inouye Solar Telescope (DKIST) will revolutionize our ability to measure, understand, and model the basic physical processes that control the structure and dynamics of the Sun and its atmosphere. The first-light DKIST images, released publicly on 29 January 2020, only hint at the extraordinary capabilities that will accompany full commissioning of the five facility instruments. With this Critical Science Plan (CSP) we attempt to anticipate some of what those capabilities will enable, providing a snapshot of some of the scientific pursuits that the DKIST hopes to engage as start-of-operations nears. The work builds on the combined contributions of the DKIST Science Working Group (SWG) and CSP Community members, who generously shared their experiences, plans, knowledge, and dreams. Discussion is primarily focused on those issues to which DKIST will uniquely contribute. Title: Carrington's lost photograph Authors: Cliver, E. W.; Fletcher, Lyndsay; Hudson, H. S. Bibcode: 2021A&G....62.2.40C Altcode: Ed Cliver, Lyndsay Fletcher and Hugh Hudson are looking for a photograph of Richard Carrington. Can you help? Title: Compositional Mapping of Europa and Ganymede with VLT/SPHERE and Galileo/NIMS Using Markov Chain Monte Carlo Fitting Authors: King, O. R. T.; Fletcher, L. N. Bibcode: 2021LPI....52.1060K Altcode: Infrared spectral observations of Europa and Ganymede from VLT/SPHERE and Galileo/NIMS have been fit using a Monte Carlo model to calculate compositional abundances and uncertainties. Title: A machine-learning approach to correcting atmospheric seeing in solar flare observations Authors: Armstrong, John A.; Fletcher, Lyndsay Bibcode: 2021MNRAS.501.2647A Altcode: 2020arXiv201112814A; 2020MNRAS.tmp.3530A Current post-processing techniques for the correction of atmospheric seeing in solar observations - such as Speckle interferometry and Phase Diversity methods - have limitations when it comes to their reconstructive capabilities of solar flare observations. This, combined with the sporadic nature of flares meaning observers cannot wait until seeing conditions are optimal before taking measurements, means that many ground-based solar flare observations are marred with bad seeing. To combat this, we propose a method for dedicated flare seeing correction based on training a deep neural network to learn to correct artificial seeing from flare observations taken during good seeing conditions. This model uses transfer learning, a novel technique in solar physics, to help learn these corrections. Transfer learning is when another network already trained on similar data is used to influence the learning of the new network. Once trained, the model has been applied to two flare data sets: one from AR12157 on 2014 September 6 and one from AR12673 on 2017 September 6. The results show good corrections to images with bad seeing with a relative error assigned to the estimate based on the performance of the model. Further discussion takes place of improvements to the robustness of the error on these estimates. Title: Hot X-ray onsets of solar flares Authors: Hudson, Hugh S.; Simões, Paulo J. A.; Fletcher, Lyndsay; Hayes, Laura A.; Hannah, Iain G. Bibcode: 2021MNRAS.501.1273H Altcode: 2020MNRAS.tmp.3462H; 2020arXiv200705310H The study of the localized plasma conditions before the impulsive phase of a solar flare can help us understand the physical processes that occur leading up to the main flare energy release. Here, we present evidence of a hot X-ray 'onset' interval of enhanced isothermal plasma temperatures in the range of 10-15 MK over a period of time prior to the flare's impulsive phase. This 'hot onset' interval occurs during the initial soft X-ray increase and definitely before any detectable hard X-ray emission. The isothermal temperatures, estimated by the Geostationary Operational Environmental Satellite X-ray sensor, and confirmed with data from the Reuven Ramaty High Energy Solar Spectroscopic Imager, show no signs of gradual increase, and the 'hot onset' phenomenon occurs regardless of flare classification or configuration. In a small sample of four representative flare events, we tentatively identify this early hot onset soft X-ray emission to occur within footpoint and low-lying loop regions, rather than in coronal structures, based on images from the Atmospheric Imaging Assembly. We confirm this via limb occultation of a flaring region. These hot X-ray onsets appear before there is evidence of collisional heating by non-thermal electrons, and hence challenge the standard modelling techniques. Title: Measuring the structure and equation of state of polyethylene terephthalate at megabar pressures Authors: Lütgert, J.; Vorberger, J.; Hartley, N. J.; Voigt, K.; Rödel, M.; Schuster, A. K.; Benuzzi-Mounaix, A.; Brown, S.; Cowan, T. E.; Cunningham, E.; Döppner, T.; Falcone, R. W.; Fletcher, L. B.; Galtier, E.; Glenzer, S. H.; Laso Garcia, A.; Gericke, D. O.; Heimann, P. A.; Lee, H. J.; McBride, E. E.; Pelka, A.; Prencipe, I.; Saunders, A. M.; Schölmerich, M.; Schörner, M.; Sun, P.; Vinci, T.; Ravasio, A.; Kraus, D. Bibcode: 2021NatSR..1112883L Altcode: We present structure and equation of state (EOS) measurements of biaxially orientated polyethylene terephthalate (PET, (C10H8O4) n?, also called mylar) shock-compressed to (155 ±20 ?) GPa and (6000 ±1000 ?) K using in situ X-ray diffraction, Doppler velocimetry, and optical pyrometry. Comparing to density functional theory molecular dynamics (DFT-MD) simulations, we find a highly correlated liquid at conditions differing from predictions by some equations of state tables, which underlines the influence of complex chemical interactions in this regime. EOS calculations from ab initio DFT-MD simulations and shock Hugoniot measurements of density, pressure and temperature confirm the discrepancy to these tables and present an experimentally benchmarked correction to the description of PET as an exemplary material to represent the mixture of light elements at planetary interior conditions. Title: Constraints on the height of the CH4 homopause from an analysis of IRTF-TEXES spectra Authors: Sinclair, J. A.; Greathouse, T. K.; Giles, R.; Antuñano, A.; Moses, J. I.; Fouchet, T.; Bezard, B.; Clark, G. B.; Tao, C.; Grodent, D. C.; Orton, G.; Hue, V.; Fletcher, L. N.; Irwin, P. G. Bibcode: 2020AGUFMA076...03S Altcode: We present an analysis of high-resolution spectra of Jupiter's CH3 (methyl radical) and CH4 emission measured at mid-to-high latitudes with the goal of determining spatial and temporal variations in the altitude of the CH4 homopause. IRTF-TEXES (Texas Echelon Cross Echelle Spectrograph, Lacy et al., 2002, PASP 114, 153-168) spectra were measured on April 16th and August 20th 2019 and were inverted as follows. A family of photochemical models, based on Moses & Poppe (2017, Icarus 297, 33-58), was computed by varying the eddy diffusion coefficient in the upper stratosphere and thereby increasing the altitude of the CH4 homopause. Adopting each photochemical model in turn, the emission features of CH3 and CH4 were modeled simultaneously by allowing the vertical temperature profile to vary, and the quality of fit to the observations was used to discriminate between models. In preliminary results of August 20th 2019 spectra, we find that a CH4 homopause altitude below ~350 km (with respect to 1 bar) is required to fit the observations equatorward of the main oval. At 68°N, 180°W (planetocentric, System III), the center of the northern auroral region, a homopause altitude of ~450 km optimized the fit to the spectra. At 68°N, but sampling longitudes outside the main oval, a homopause altitude between ~336 km and ~400 km was required to fit the spectra. Our results confirm the hypothesis presented in previous work (e.g. Clark et al., 2018, JGR 123, 7554-7567) that the CH4 homopause altitude is higher in Jupiter's auroral regions compared to elsewhere on the planet. This suggests deposition of energy from the magnetosphere drives turbulence and vertical winds, which advects CH4 and its photochemical by-products to higher altitudes. We will repeat this analysis for IRTF/TEXES and SOFIA/EXES observations scheduled near-contemporaneously with Juno's 29th perijove (September 16th 2020) and search for temporal variations between measurements. Title: Modelling Optically Thick Radiation from Solar Flares with the Lightweaver Framework Authors: Osborne, C.; Fletcher, L. Bibcode: 2020AGUFMSH0500002O Altcode: Most spectral lines formed in the chromosphere present complex profiles due to their formation in optically thick regions and this is further exacerbated by the rapid variations of this layer during a flare. Whilst these lines carry a wealth of information regarding their formation conditions, this information is difficult to extract. The Lightweaver framework is flexible new software package for synthesising radiation from both plane-parallel and multi-dimensional atmospheres where the atomic populations can be out of local thermodynamic equilibrium. In addition to the more commonly solved statistical equilibrium equations, Lightweaver also provides tools to facilitate solving the problem of time-dependent level populations. This framework is an open source project designed to be used through Python and easily reconfigured to solve new problems. We have applied tools built on Lightweaver to reprocess simulations produced by the RADYN code, allowing further investigation into the effects of partial frequency redistribution, and calculation of response functions in this time dependent context. We expect that these new methods should provide additional diagnostic potential coinciding with observations from next generation telescopes such as DKIST. Lightweaver is also being used to investigate the effect of the radiation emitted from compact flare kernels on surrounding plasma, by extending this reprocessing to multi-dimensional radiative transfer. We will present the Lightweaver framework and discuss how it can easily be adapted to investigate these different phenomena as well as the initial results from these investigations. Title: SOFIA FORCAST observations of Jupiter in the JWST-era Authors: De Pater, I.; Reach, W. T.; Fletcher, L. N.; Goullaud, C.; Wong, M. H. Bibcode: 2020AGUFMP056.0005D Altcode: Jupiter, the most accessible example for the study of atmospheric circulation on a giant planet, serves as a template for our understanding of the atmospheric dynamics and chemistry of the ever-growing number of extrasolar planets. The atmospheres of giant planets are extremely active, varying on timescales ranging from decades (seasonally evolving chemistry and clouds), to months (variability of storms and banded structures) and even minutes (e.g., asteroidal/cometary impacts and localized storm systems). These evolving atmospheres serve as natural planetary-scale laboratories for studying the fundamental meteorology, chemistry and evolutionary mechanisms that shape the worlds around us. SOFIA's remote sensing in the far-IR penetrates thick upper-tropospheric hazes to explore the complex, turbulent dynamics of Jupiter's weather layer.

In 2014 we observed Jupiter with FORCAST at 17-37 micron to constrain the shape of its continuum emission (Fletcher et al., 2017, Ic. 286, 223), which can only be achieved if obscuration by telluric water vapor is minimized, i.e., from SOFIA or from space. The SOFIA data confirmed the Voyager findings in detecting an equator to pole increase in the para-H2 fraction (fp), with low fp and sub-equilibrium conditions at the equator and high fp and super-equilibrium conditions polewards of 60°latitude. The para-H2 fraction traces mean vertical mixing on timescales of years to decades, depending on the poorly-known hydrogen equilibration time in Jupiter's atmosphere. Equilibrium fp thus implies weak vertical mixing, while sub- or super-equilibrium fractions correspond to mean upwelling or subsidence, respectively (in the upper troposphere where fp is measured). Interestingly, both Voyager and SOFIA measured higher fp values at high northern latitudes than at high southern latitudes, suggesting an asymmetry between the two hemispheres where none is expected on the basis of seasonal variability. We discuss the advantages of a similar experiment simultaneously with JWST/ERS observations planned to be carried out after launch. Title: Hot Onsets of Solar Flares Authors: Hudson, H. S.; Simoes, P. J. D. A.; Fletcher, L.; Hayes, L.; Hannah, I. G. Bibcode: 2020AGUFMSH0500003H Altcode: No abstract at ADS Title: Atmospheric chemistry on Uranus and Neptune Authors: Moses, J. I.; Cavalié, T.; Fletcher, L. N.; Roman, M. T. Bibcode: 2020RSPTA.37890477M Altcode: 2020arXiv200611367M; 2020RSPTA.37800477M Comparatively little is known about atmospheric chemistry on Uranus and Neptune, because remote spectral observations of these cold, distant `Ice Giants' are challenging, and each planet has only been visited by a single spacecraft during brief flybys in the 1980s. Thermochemical equilibrium is expected to control the composition in the deeper, hotter regions of the atmosphere on both planets, but disequilibrium chemical processes such as transport-induced quenching and photochemistry alter the composition in the upper atmospheric regions that can be probed remotely. Surprising disparities in the abundance of disequilibrium chemical products between the two planets point to significant differences in atmospheric transport. The atmospheric composition of Uranus and Neptune can provide critical clues for unravelling details of planet formation and evolution, but only if it is fully understood how and why atmospheric constituents vary in a three-dimensional sense and how material coming in from outside the planet affects observed abundances. Future mission planning should take into account the key outstanding questions that remain unanswered about atmospheric chemistry on Uranus and Neptune, particularly those questions that pertain to planet formation and evolution, and those that address the complex, coupled atmospheric processes that operate on Ice Giants within our solar system and beyond.

This article is part of a discussion meeting issue `Future exploration of ice giant systems'. Title: The internal structure of Jupiter's Great Red Spot Authors: Li, C.; Fletcher, L. N.; Wong, M. H.; Allison, M. D.; Atreya, S. K.; Bjoraker, G. L.; Bolton, S. J.; Guillot, T.; Ingersoll, A. P.; Janssen, M. A.; Levin, S.; Li, L.; Orton, G.; Oyafuso, F. A.; Steffes, P. G.; Zhang, Z. Bibcode: 2020AGUFMA076...15L Altcode: Contrasts in thermal emission within and surrounding Jupiter's Great Red Spot (GRS) were mapped at six frequencies by the Juno Microwave Radiometer (MWR) during its 7th flyby (PJ7) over Jupiter. Compared to the average thermal emission at the other longitudes, the GRS appears brighter by about 22 K in the 0.6-GHz (50-cm) channel, which senses thermal emission from hundreds of bars in pressure. The brightness-temperature anomaly decreases with increasing altitude and almost vanishes at the 2.6-GHz (11.5-cm) channel, probing approximately the 10-bar pressure level. At levels shallower than 10 bars, the GRS exhibits a brightness-temperature asymmetry in latitude, with thermal emission from the northern part of the GRS being fainter and the southern part being brighter by up to 10 K compared to the average. A novel way of exploring the degenerate space of temperature and opacity is developed by progressively increasing the constraint on the temperature profile. The result suggests that the GRS has an extended upwelling branch in the north between 20oS ~ 16oS originating at depths > 100 bars (230 km down from the 1-bar level) and a narrow subsiding branch in the south near 23.5oS penetrating to about 30 bars. We did not see the bottom of the GRS in our longest wavelength channel, which means that the bottom of the GRS must be deeper than 100 bars. Title: Thermal Measurements of the Ring System of Uranus Authors: Molter, E. M.; De Pater, I.; Roman, M. T.; Fletcher, L. N. Bibcode: 2020AGUFMP017...03M Altcode: The narrow main rings of Uranus are composed of primarily centimeter- to meter-sized particles, with a very small or nonexistent dust component. This property presents a challenge to visible and near-infrared instruments observing the rings, which are largely unable to differentiate large particles from dust; thus, the thickness, mass, filling factor, and detailed particle size distribution of these rings remain poorly constrained. In this work we observed the thermal component of the Uranian ring system for the first time, making use of millimeter (1.3-3.1 mm) imaging from the Atacama Large (sub-)Millimeter Array and mid-infrared imaging from the Very Large Telescope VISIR instrument. The ε ring was readily seen by eye in the images; the other main ring groups were visible in a radial (azimuthally-averaged) profile at millimeter wavelengths. A simple thermal model similar to the Near-Earth Asteroid Thermal Model (NEATM) of near-Earth asteroids was leveraged to determine a ring particle temperature of 77.3 ± 1.8 K for the ε ring. This temperature is higher than expected for fast-rotating ring particles viewed at our observing geometry, meaning that the data favor a model in which the thermal inertia of the ring particles is low and/or their rotation rate is slow. The ε ring displayed a factor of 2-3 brightness difference between periapsis and apoapsis, and an average fractional visible area (the two-dimensional projection of the filling factor) of 49.1% ± 2.2%. These observations are consistent with optical and near-infrared reflected light observations, confirming the hypothesis that micron-sized dust is not present in Uranus's main rings. Title: Long-term Cycles of Variability of Jupiter's Atmosphere from Ground-based Infrared Observations Authors: Antuñano, A.; Fletcher, L. N.; Orton, G.; Sinclair, J. A.; Kasaba, Y. Bibcode: 2020AGUFMA076...06A Altcode: Jupiter's atmosphere displays some of the most dramatic weather of any planet in our Solar System, with cycles of activity changing the upper tropospheric and stratospheric temperatures, aerosols, and cloud structures through physical processes that are not yet well understood. Here we use almost 40 years (more than 3 jovian years) of ground-based infrared observations captured at NASA's Infrared Telescope Facility (IRTF), the Very Large Telescope (VLT) and Subaru between 1980 and 2019 in a number of filters spanning from 7.9 to 24.5 µm (sampling upper tropospheric and stratospheric temperatures and aerosols via collision-induced hydrogen and helium absorption, and emission from stratospheric hydrocarbons), to (i) understand the impact of the tropospheric activity on the periodicity of the stratospheric temperature oscillations, (ii) characterize the long-term variability of Jupiter's atmosphere at different altitudes in the upper troposphere and stratosphere, and (iii) investigate the long-term thermal, chemical and aerosol changes in Jupiter's troposphere. In particular, we generate Lomb-Scargle periodograms and apply a Wavelet Transform analysis to our dataset to look for potential periodicities on the brightness temperature variability in different filters and compare them to previously reported cyclic activity at visible wavelengths (sensing the ammonia cloud top at ~500 mbar) and 5 µm (sensing the 1-4 bar pressure level). Finally, a Principal Component Analyses (PCA) is also performed to analyse the correlation of the brightness temperature variations at different belts and zones. Title: Saturn's Seasonal Atmosphere at Northern Summer Solstice Authors: Fletcher, L. N.; Sromovsky, L.; Hue, V.; Moses, J. I.; Guerlet, S.; West, R. A.; Koskinen, T. Bibcode: 2020arXiv201209288F Altcode: The incredible longevity of Cassini's orbital mission at Saturn has provided the most comprehensive exploration of a seasonal giant planet to date. This review explores Saturn's changing global temperatures, composition, and aerosol properties between northern spring and summer solstice (2015-2017), extending our previous review of Cassini's remote sensing investigations (2004-14, Fletcher et al., 2018) to the grand finale. The result is an unprecedented record of Saturn's climate that spans almost half a Saturnian year, which can be used to test the seasonal predictions of radiative climate models, neutral and ion photochemistry models, and atmospheric circulation models. Hemispheric asymmetries in tropospheric and stratospheric temperatures were observed to reverse from northern winter to northern summer; spatial distributions of hydrocarbons and para-hydrogen shifted in response to atmospheric dynamics (e.g., seasonally-reversing Hadley cells, polar stratospheric vortex formation, equatorial stratospheric oscillations, and inter-hemispheric transport); and upper tropospheric and stratospheric aerosols exhibited changes in optical thickness that modulated Saturn's visible colours (from blue hues to a golden appearance in the north near solstice), reflectivity, and near-infrared emission. Numerical simulations of radiative balance and photochemistry do a good job in reproducing the observed seasonal change and phase lags, but discrepancies between models and observations still persist, indicating a crucial role for atmospheric dynamics and the need to couple chemical and radiative schemes to the next generation of circulation models. With Cassini's demise, an extended study of Saturn's seasons, from northern summer to autumn, will require the capabilities of ground- and space-based observatories, as we eagerly await the next orbital explorer at Saturn. Title: Determining the Global Water Abundance in Jupiter from Juno MWR Authors: Zhang, Z.; Levin, S.; Adumitroaie, V.; Allison, M. D.; Arballo, J. K.; Atreya, S. K.; Becker, H. N.; Bjoraker, G. L.; Bolton, S. J.; Brown, S. T.; Fletcher, L. N.; Guillot, T.; Gulkis, S.; Hodges, A. L.; Ingersoll, A. P.; Janssen, M. A.; Li, C.; Li, L.; Lunine, J. I.; Misra, S.; Orton, G.; Oyafuso, F. A.; Santos-Costa, D.; Sarkissian, E.; Steffes, P. G.; Waite, H., Jr.; Wong, M. H. Bibcode: 2020AGUFMP005.0005Z Altcode: The global water abundance in Jupiter is pivotal in understanding Giant-Planet formation and the delivery of volatiles throughout the solar system. The Microwave Radiometer (MWR) on board Juno provides the first measurements of Jupiter's deep atmosphere, down to ~250 bars in pressure. Li et al. (2020) reported the initial results from MWR on water abundance near Jupiter's equatorial region. The discovery by Juno that Jupiter's atmosphere is not well mixed at depth and displays significant variability with latitude suggests that water may vary with latitude even at depth. We present current plans and status for Juno's investigation of water beyond equatorial latitudes including observation plans for Juno's extended mission that will be able to observe Jupiter's north polar region at improved resolution. Title: Ice giant system exploration in the 2020s: an introduction Authors: Fletcher, L. N.; Simon, A. A.; Hofstadter, M. D.; Arridge, C. S.; Cohen, Ian J.; Masters, A.; Mandt, K.; Coustenis, A. Bibcode: 2020RSPTA.37890473F Altcode: 2020RSPTA.37800473F; 2020arXiv200812125F The international planetary science community met in London in January 2020, united in the goal of realizing the first dedicated robotic mission to the distant ice giants, Uranus and Neptune, as the only major class of solar system planet yet to be comprehensively explored. Ice-giant-sized worlds appear to be a common outcome of the planet formation process, and pose unique and extreme tests to our understanding of exotic water-rich planetary interiors, dynamic and frigid atmospheres, complex magnetospheric configurations, geologically-rich icy satellites (both natural and captured), and delicate planetary rings. This article introduces a special issue on ice giant system exploration at the start of the 2020s. We review the scientific potential and existing mission design concepts for an ambitious international partnership for exploring Uranus and/or Neptune in the coming decades.

This article is part of a discussion meeting issue `Future exploration of ice giant systems'. Title: Slowly Moving Thermal Waves in Saturn Authors: Orton, G.; Sinclair, J.; Fletcher, L.; Read, P.; Flasar, F. M.; Achterberg, R.; Yanamandra-Fisher, P.; Fujiyoshi, T.; Fisher, B.; Irwin, P. Bibcode: 2020DPS....5220104O Altcode: We surveyed the global temperature field of Saturn's atmosphere using the Cassini Composite Infrared Spectrometer (CIRS, 7-1000 µm), complemented by ground-based mid-infrared observations (7-25 µm), from 1995 to 2020. We detected and characterized properties of slowly moving zonal thermal waves and their variability during that period. The most inclusive CIRS surveys, FIRMAPs (15 cm-1 spectral resolution), covered the planet from the equator to either north or south pole, sweeping through the latitude range while the planet rotated beneath over its ~10-hour rotation. Additional measurements were made by ground-based observations at the Infrared Telescope Facility using the MIRSI instrument, the Very Large Telescope using VISIR and the Subaru Telescope using COMICS. We sampled spectral ranges dominated both by upper-tropospheric emission (80-200 mbar) and by stratospheric emission (0.5-3 mbar). Several types of slowly moving zonal thermal waves were detected: (1) meridionally broad wavenumber-1 through -3 oscillations, (2) equatorial waves, some of which extend northward to mid-latitudes, (3) prominent wavenumber-12 oscillations in the southern hemisphere, which also have components of wavenumbers 1 through 3 and extend over 15°-35°S latitude, (4) mid-latitude wavenumber > 2 oscillations in both hemispheres with variable time dependence and morphology, and (5) discrete low-latitude tropospheric features. The prominent southern-hemisphere waves appear to have distinct periods of maximum intensity around 2003-2004 from ground-based observations and 2008-2009 from CIRS FIRMAPs. These waves are easily detectable in both the stratosphere, where the other types of waves are prominent, but also in the troposphere with no detectable phase shift in longitude. These waves were also sufficiently coherent to track a mean phase speed, which is about 0.5° per day, retrograde. After 2009, wavenumber-1 oscillations in the northern hemisphere are joined by higher-wavenumber oscillations. A local temperature maximum is seen around 2010-2011, then another in 2016-2017. Further ground-based observations are required to determine whether the amplitude of northern-hemisphere waves is influenced by seasonally dependent insolation. Title: The Solar Orbiter magnetometer Authors: Horbury, T. S.; O'Brien, H.; Carrasco Blazquez, I.; Bendyk, M.; Brown, P.; Hudson, R.; Evans, V.; Oddy, T. M.; Carr, C. M.; Beek, T. J.; Cupido, E.; Bhattacharya, S.; Dominguez, J. -A.; Matthews, L.; Myklebust, V. R.; Whiteside, B.; Bale, S. D.; Baumjohann, W.; Burgess, D.; Carbone, V.; Cargill, P.; Eastwood, J.; Erdös, G.; Fletcher, L.; Forsyth, R.; Giacalone, J.; Glassmeier, K. -H.; Goldstein, M. L.; Hoeksema, T.; Lockwood, M.; Magnes, W.; Maksimovic, M.; Marsch, E.; Matthaeus, W. H.; Murphy, N.; Nakariakov, V. M.; Owen, C. J.; Owens, M.; Rodriguez-Pacheco, J.; Richter, I.; Riley, P.; Russell, C. T.; Schwartz, S.; Vainio, R.; Velli, M.; Vennerstrom, S.; Walsh, R.; Wimmer-Schweingruber, R. F.; Zank, G.; Müller, D.; Zouganelis, I.; Walsh, A. P. Bibcode: 2020A&A...642A...9H Altcode: The magnetometer instrument on the Solar Orbiter mission is designed to measure the magnetic field local to the spacecraft continuously for the entire mission duration. The need to characterise not only the background magnetic field but also its variations on scales from far above to well below the proton gyroscale result in challenging requirements on stability, precision, and noise, as well as magnetic and operational limitations on both the spacecraft and other instruments. The challenging vibration and thermal environment has led to significant development of the mechanical sensor design. The overall instrument design, performance, data products, and operational strategy are described. Title: Reflection and Shadowing from Saturn's Rings: Influence on Photochemisty and Heating Authors: Edgington, S. G.; Atreya, S.; West, R.; Baines, K.; Fletcher, L. Bibcode: 2020DPS....5220106E Altcode: Cassini orbited Saturn for over thirteen years, nearly a half Saturn year. This corresponded to a seasonal configuration where the sub-solar point was at ~24°S at the time of Saturn Orbit Insertion (July 1, 2004) and ~27°N at the time of Cassini's Grand Finale. During this period, the ring shadow moved southward from covering a substantial area of the northern hemisphere to covering a large swath of territory south of the equator as solstice approached. At equinox, the rings project a small sliver of shadow at low latitudes. At its maximum extent, the ring shadow can reach as far as 48°N/S at the meridian (~58°N/S at the terminator).

Both ultraviolet and visible sunlight penetrating into any particular latitude will vary greatly depending on both Saturn's season, the optical thickness of each ring system and its reflective properties. In essence, the rings act like both semi-transparent Venetian blinds over the atmosphere of Saturn. At the same time, the illuminated side of the rings reflect ultraviolet and visible solar photons onto the fully illuminated hemisphere of the planet. This acts to enhance both photochemistry and heating and potentially enhancing seasonal effects. Lastly, the rings, having a temperature themselves, provides a source of thermal photons impinging onto the atmosphere and a possible source of heating.

The projection of the oscillating ring shadow onto the planet has been derived as a function of season. In addition, detailed calculations of geometric parameters important for light scattering from the rings onto an oblate planet have been worked for a fine grid of latitudes and longitudes. We will focus on how these geometric parameters can be used for both photochemical (UV) and thermal balance (visible and infrared) radiative transfer calculations as a function of season.

The impact of these augmentations on production and loss rates of hydrocarbons (e.g. acetylene, ethane, and propane), ammonia, phosphine, and hazes will be examined and attempt to explain several Saturn observations conducted by Cassini. Comparison with Jupiter, where seasonal effects are known to be insignificant, will be made.

Acknowledgements: The research described in this paper was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Government sponsorship is acknowledged. Title: Solar Flare Energy Partitioning and Transport -- the Impulsive Phase (a Heliophysics 2050 White Paper) Authors: Kerr, Graham S.; Alaoui, Meriem; Allred, Joel C.; Bian, Nicholas H.; Dennis, Brian R.; Emslie, A. Gordon; Fletcher, Lyndsay; Guidoni, Silvina; Hayes, Laura A.; Holman, Gordon D.; Hudson, Hugh S.; Karpen, Judith T.; Kowalski, Adam F.; Milligan, Ryan O.; Polito, Vanessa; Qiu, Jiong; Ryan, Daniel F. Bibcode: 2020arXiv200908400K Altcode: Solar flares are a fundamental component of solar eruptive events (SEEs; along with solar energetic particles, SEPs, and coronal mass ejections, CMEs). Flares are the first component of the SEE to impact our atmosphere, which can set the stage for the arrival of the associated SEPs and CME. Magnetic reconnection drives SEEs by restructuring the solar coronal magnetic field, liberating a tremendous amount of energy which is partitioned into various physical manifestations: particle acceleration, mass and magnetic-field eruption, atmospheric heating, and the subsequent emission of radiation as solar flares. To explain and ultimately predict these geoeffective events, the heliophysics community requires a comprehensive understanding of the processes that transform and distribute stored magnetic energy into other forms, including the broadband radiative enhancement that characterises flares. This white paper, submitted to the Heliophysics 2050 Workshop, discusses the flare impulsive phase part of SEEs, setting out the questions that need addressing via a combination of theoretical, modelling, and observational research. In short, by 2050 we must determine the mechanisms of particle acceleration and propagation, and must push beyond the paradigm of energy transport via nonthermal electron beams, to also account for accelerated protons & ions and downward directed Alfven waves. Title: Solar Flare Energy Partitioning and Transport -- the Gradual Phase (a Heliophysics 2050 White Paper) Authors: Kerr, Graham S.; Alaoui, Meriem; Allred, Joel C.; Bian, Nicholas H.; Dennis, Brian R.; Emslie, A. Gordon; Fletcher, Lyndsay; Guidoni, Silvina; Hayes, Laura A.; Holman, Gordon D.; Hudson, Hugh S.; Karpen, Judith T.; Kowalski, Adam F.; Milligan, Ryan O.; Polito, Vanessa; Qiu, Jiong; Ryan, Daniel F. Bibcode: 2020arXiv200908407K Altcode: Solar flares are a fundamental component of solar eruptive events (SEEs; along with solar energetic particles, SEPs, and coronal mass ejections, CMEs). Flares are the first component of the SEE to impact our atmosphere, which can set the stage for the arrival of the associated SEPs and CME. Magnetic reconnection drives SEEs by restructuring the solar coronal magnetic field, liberating a tremendous amount of energy which is partitioned into various physical manifestations: particle acceleration, mass and magnetic-field eruption, atmospheric heating, and the subsequent emission of radiation as solar flares. To explain and ultimately predict these geoeffective events, the heliophysics community requires a comprehensive understanding of the processes that transform and distribute stored magnetic energy into other forms, including the broadband radiative enhancement that characterises flares. This white paper, submitted to the Heliophysics 2050 Workshop, discusses the flare gradual phase part of SEEs, setting out the questions that need addressing via a combination of theoretical, modelling, and observational research. In short, the flare gradual phase persists much longer than predicted so, by 2050, we must identify the characteristics of the significant energy deposition sustaining the gradual phase, and address the fundamental processes of turbulence and non-local heat flux. Title: Hot X-ray Onsets of Solar Flares Authors: Hayes, L.; Hudson, H.; Simoes, P.; Fletcher, L.; Hannah, I. Bibcode: 2020SPD....5121113H Altcode: The study of the localized plasma conditions before the impulsive phase of a solar flare can help us understand the physical processes that occur leading up to the main flare energy release. Here, we present evidence of a hot X-ray 'onset' interval of enhanced isothermal plasma temperatures in the range of 10-15 MK up to tens of seconds prior to the flare's impulsive phase. This 'hot onset' interval occurs during the pre-flare time during which elevated GOES soft X-ray flux is detected, but prior to detectable hard X-ray emission. The isothermal temperatures, estimated by the Geostationary Operational Environmental Satellite (GOES) X-ray sensor, and confirmed with data from RHESSI, show no signs of gradual increase, and occurs regardless of flare classification or configuration. In a small sample of four representative flare events we identify this early hot onset soft X-ray emission mainly within footpoint and low-lying loops, rather than with coronal structures, based on images from the Atmospheric Imaging Assembly (AIA) and the use of limb occultation. These hot X-ray onsets appear before there is evidence of collisional heating by non-thermal electrons, and hence challenges the standard flare heating modeling techniques. Title: Jupiter's Equatorial Plumes and Hot Spots: Spectral Mapping from Gemini/TEXES and Juno/MWR Authors: Fletcher, L. N.; Orton, G. S.; Greathouse, T. K.; Rogers, J. H.; Zhang, Z.; Oyafuso, F. A.; Eichstädt, G.; Melin, H.; Li, C.; Levin, S. M.; Bolton, S.; Janssen, M.; Mettig, H. -J.; Grassi, D.; Mura, A.; Adriani, A. Bibcode: 2020JGRE..12506399F Altcode: 2020arXiv200400072F We present multiwavelength measurements of the thermal, chemical, and cloud contrasts associated with the visibly dark formations (also known as 5-μm hot spots) and intervening bright plumes on the boundary between Jupiter's Equatorial Zone (EZ) and North Equatorial Belt (NEB). Observations made by the TEXES 5- to 20-μm spectrometer at the Gemini North Telescope in March 2017 reveal the upper-tropospheric properties of 12 hot spots, which are directly compared to measurements by Juno using the microwave radiometer (MWR), JIRAM at 5 μm, and JunoCam visible images. MWR and thermal-infrared spectroscopic results are consistent near 0.7 bar. Mid-infrared-derived aerosol opacity is consistent with that inferred from visible-albedo and 5-μm opacity maps. Aerosol contrasts, the defining characteristics of the cloudy plumes and aerosol-depleted hot spots, are not a good proxy for microwave brightness. The hot spots are neither uniformly warmer nor ammonia-depleted compared to their surroundings at p<1 bar. At 0.7 bar, the microwave brightness at the edges of hot spots is comparable to other features within the NEB. Conversely, hot spots are brighter at 1.5 bar, signifying either warm temperatures and/or depleted NH3 at depth. Temperatures and ammonia are spatially variable within the hot spots, so the precise location of the observations matters to their interpretation. Reflective plumes sometimes have enhanced NH3, cold temperatures, and elevated aerosol opacity, but each plume appears different. Neither plumes nor hot spots had microwave signatures in channels sensing p>10 bars, suggesting that the hot spot/plume wave is a relatively shallow feature. Title: Spatial structure in Neptune's 7.90- μm stratospheric CH4 emission, as measured by VLT-VISIR Authors: Sinclair, J. A.; Orton, G. S.; Fletcher, L. N.; Roman, M.; de Pater, I.; Encrenaz, T.; Hammel, H. B.; Giles, R. S.; Velusamy, T.; Moses, J. I.; Irwin, P. G. J.; Momary, T. W.; Rowe-Gurney, N.; Tabataba-Vakili, F. Bibcode: 2020Icar..34513748S Altcode: We present a comparison of VLT-VISIR images and Keck-NIRC2 images of Neptune, which highlight the coupling between its troposphere and stratosphere. VLT-VISIR images were obtained on September 16th 2008 (UT) at 7.90 μm and 12.27 μm, which are primarily sensitive to 1-mbar CH4 and C2H6 emission, respectively. NIRC2 images in the H band were obtained on October 5th, 6th and 9th 2008 (UT) and sense clouds and haze in the upper troposphere and lower stratosphere (from approximately 600 to 20 mbar). At 7.90 μm, we observe enhancements of CH4 emission in latitude bands centered at approximately 25∘S and 48∘S (planetocentric). Within these zonal bands, tentative detections (< 2 σ) of discrete hotspots of CH4 emission are also evident at 24∘S, 181∘W and 42∘S, 170∘W. The longitudinal-mean enhancements in the CH4 emission are also latitudinally-coincident with bands of bright (presumably CH4 ice) clouds in the upper troposphere and lower stratosphere evidenced in the H-band images. This suggests the Neptunian troposphere and stratosphere are coupled in these specific regions. This could be in the form of (1) 'overshoot' of strong, upwelling plumes and advection of CH4 ice into the lower stratosphere, which subsequently sublimates into CH4 gas and/or (2) generation of waves by plumes impinging from the tropopause below, which impart their energy and heat the lower stratosphere. We favor the former process since there is no evidence of similar smaller-scale morphology in the C2H6 emission, which probes a similar atmospheric level. However, we cannot exclude temperature variations as the source of the morphology observed in CH4 emission. Future, near-infrared imaging of Neptune performed near-simultaneously with future mid-infrared spectral observations of Neptune by the James Webb Space Telescope would allow the coupling of Neptune's troposphere and stratosphere to be confirmed and studied in greater detail. Title: Monitoring Neptune's atmosphere with a combination of small and large telescopes: The role of Spanish Telescopes in a global international campaign Authors: Hueso, R.; Sánchez-Lavega, A.; Roman, M.; Dhillon, V.; de Pater, I.; Fletcher, L.; Orton, G. S.; Simon, A.; Wong, M.; Chavez, E.; Sromovsky, L.; Fry, P.; Delcroix, M.; Hernández-Bernal, J.; Iñurrigarro, P.; Littlefair, S.; Marsh, T.; Ordonez-Etxeberria, I.; Pérez-Hoyos, S.; Redwing, E.; Rojas, J. F.; Tollefson, J. Bibcode: 2020sea..confE.102H Altcode: Neptune's atmosphere is covered by tropospheric clouds and hazes that evolve in timescales of days, months and years. Given the small apparent size of Neptune's disk (2.4"), there are outstanding difficulties in obtaining sufficient high-resolution data to trace Neptune's atmospheric dynamics and study its variability. Here we present results of an international campaign to observe Neptune and we focus in the potential of Spanish Telescopes to advance in the knowledge of its atmosphere. Title: Jupiter in the Ultraviolet: Acetylene and Ethane Abundances in the Stratosphere of Jupiter from Cassini Observations between 0.15 and 0.19 μm Authors: Melin, Henrik; Fletcher, L. N.; Irwin, P. G. J.; Edgington, S. G. Bibcode: 2020AJ....159..291M Altcode: 2020arXiv200509895M At wavelengths between 0.15 and 0.19 μm, the far-ultraviolet spectrum of Jupiter is dominated by the scattered solar spectrum, attenuated by molecular absorptions primarily by acetylene and ethane, and to a lesser extent ammonia and phosphine. We describe the development of our radiative transfer code that enables the retrieval of abundances of these molecular species from ultraviolet reflectance spectra. As a proof-of-concept we present an analysis of Cassini Ultraviolet Imaging Spectrograph (UVIS) observations of the disk of Jupiter during the 2000/2001 flyby. The ultraviolet-retrieved acetylene abundances in the upper stratosphere are lower than those predicted by models based solely on infrared thermal emission from the mid-stratosphere observed by the Composite Infrared Spectrometer (CIRS), requiring an adjustment to the vertical profiles above 1 mbar. We produce a vertical acetylene abundance profile that is compatible with both CIRS and UVIS, with reduced abundances at pressures <1 mbar: the 0.1 mbar abundances are 1.21 ± 0.07 ppm for acetylene and 20.8 ± 5.1 ppm for ethane. Finally, we perform a sensitivity study for the JUICE ultraviolet spectrograph, which has extended wavelength coverage out to 0.21 μm, enabling the retrieval of ammonia and phosphine abundances, in addition to acetylene and ethane. Title: Deep learning for the Sun Authors: Armstrong, John A.; Osborne, Christopher M. J.; Fletcher, Lyndsay Bibcode: 2020A&G....61c3.34A Altcode: John A Armstrong, Christopher M J Osborne and Lyndsay Fletcher examine how neural networks can be used to explore the nature and location of solar activity. Title: Demonstration of X-ray Thomson scattering as diagnostics for miscibility in warm dense matter Authors: Frydrych, S.; Vorberger, J.; Hartley, N. J.; Schuster, A. K.; Ramakrishna, K.; Saunders, A. M.; van Driel, T.; Falcone, R. W.; Fletcher, L. B.; Galtier, E.; Gamboa, E. J.; Glenzer, S. H.; Granados, E.; MacDonald, M. J.; MacKinnon, A. J.; McBride, E. E.; Nam, I.; Neumayer, P.; Pak, A.; Voigt, K.; Roth, M.; Sun, P.; Gericke, D. O.; Döppner, T.; Kraus, D. Bibcode: 2020NatCo..11.2620F Altcode: The gas and ice giants in our solar system can be seen as a natural laboratory for the physics of highly compressed matter at temperatures up to thousands of kelvins. In turn, our understanding of their structure and evolution depends critically on our ability to model such matter. One key aspect is the miscibility of the elements in their interiors. Here, we demonstrate the feasibility of X-ray Thomson scattering to quantify the degree of species separation in a 1:1 carbon-hydrogen mixture at a pressure of ~150 GPa and a temperature of ~5000 K. Our measurements provide absolute values of the structure factor that encodes the microscopic arrangement of the particles. From these data, we find a lower limit of 2 4-7+6?% of the carbon atoms forming isolated carbon clusters. In principle, this procedure can be employed for investigating the miscibility behaviour of any binary mixture at the high-pressure environment of planetary interiors, in particular, for non-crystalline samples where it is difficult to obtain conclusive results from X-ray diffraction. Moreover, this method will enable unprecedented measurements of mixing/demixing kinetics in dense plasma environments, e.g., induced by chemistry or hydrodynamic instabilities. Title: John Campbell Brown OBE (1947-2019) Authors: Fletcher, Lyndsay; Labrosse, Nicolas; Mackinnon, Alexander Bibcode: 2020A&G....61b2.14F Altcode: Astronomer Royal for Scotland and inspirational solar physicist, by Lyndsay Fletcher, Nicolas Labrosse and Alec MacKinnon. Title: On the Spatial Distribution of Minor Species in Jupiter's Troposphere as Inferred From Juno JIRAM Data Authors: Grassi, D.; Adriani, A.; Mura, A.; Atreya, S. K.; Fletcher, L. N.; Lunine, J. I.; Orton, G. S.; Bolton, S.; Plainaki, C.; Sindoni, G.; Altieri, F.; Cicchetti, A.; Dinelli, B. M.; Filacchione, G.; Migliorini, A.; Moriconi, M. L.; Noschese, R.; Olivieri, A.; Piccioni, G.; Sordini, R.; Stefani, S.; Tosi, F.; Turrini, D. Bibcode: 2020JGRE..12506206G Altcode: The spatial distribution of water, ammonia, phosphine, germane, and arsine in the Jupiter's troposphere has been inferred from the Jovian Infrared Auroral Mapper (JIRAM) Juno data. Measurements allow us to retrieve the vertically averaged concentration of gases between ~3 and 5 bars from infrared-bright spectra. Results were used to create latitudinal profiles. The water vapor relative humidity varies with latitude from <1% to over 15%. At intermediate latitudes (30-70°) the water vapor maxima are associated with the location of cyclonic belts, as inferred from mean zonal wind profiles (Porco et al., 2003). The high-latitude regions (beyond 60°) are drier in the north (mean relative humidity around 2-3%) than the south, where humidity reaches 15% around the pole. The ammonia volume mixing ratio varies from 1 × 10-4 to 4 × 10-4. A marked minimum exists around 10°N, while data suggest an increase over the equator. The high-latitude regions are different in the two hemispheres, with a gradual increase in the south and more constant values with latitude in the north. The phosphine volume mixing ratio varies from 4 × 10-7 to 10 × 10-7. A marked minimum exists in the North Equatorial Belt. For latitudes poleward 30°S and 30°N, the northern hemisphere appears richer in phosphine, with a decrease toward the pole, while the opposite is observed in the south. JIRAM data indicate an increase of germane volume mixing ratio from 2 × 10-10 to 8 × 10-10 from both poles to 15°S, with a depletion centered around the equator. Arsine presents the opposite trend, with maximum values of 6 × 10-10 at the two poles and minima below 1 × 10-10 around 20°S. Title: Compositional Mapping of Europa with VLT/SPHERE Authors: King, O. R. T.; Fletcher, L. N.; Ligier, N. Bibcode: 2020LPI....51.2046K Altcode: A high spatial resolution ground-based IR observation of Europa has been fit using a Monte Carlo model to calculate compositional abundances and uncertainties. Title: New Frontiers-Class Uranus Orbiter: A Case for Exploring the Feasibility of Achieving Multidisciplinary Science with a Mid-Scale Mission Authors: Cohen, I. J.; Beddingfield, C. B.; Chancia, R. O.; DiBraccio, G. A.; Hedman, M. M.; MacKenzie, S. M.; Mauk, B. H.; Sayanagi, K. M.; Soderlund, K. M.; Turtle, E. P.; Adams, E. Y.; Ahrens, C. J.; Arridge, C. S.; Brooks, S. M.; Bunce, E. J.; Charnoz, S.; Clark, G. B.; Coustenis, A.; Dillman, R. A.; Dutta, S.; Fletcher, L. N.; Harbison, R. A.; Helled, R.; Holme, R.; Jozwiak, L. M.; Kasaba, Y.; Kollmann, P.; Luszcz-Cook, S.; Mousis, O.; Mura, A.; Murakami, G.; Parisi, M.; Rymer, A. M.; Stanley, S.; Stephan, K.; Vervack, R. J.; Wong, M. H.; Wurz, P. Bibcode: 2020LPI....51.1428C Altcode: Icy Uranus / Can your system be explored / For New Frontiers cost? Title: Reappraisal and New Constraints on Europa's Surface Composition with the Near-Infrared Imaging Spectrometer SINFONI of the VLT Authors: Ligier, N.; Carter, J.; Poulet, F.; Fletcher, L.; King, O.; Brunetto, R.; Massé, M.; Snodgrass, C. Bibcode: 2020LPI....51.1964L Altcode: We present the physico-chemical properties of Europa's surface derived from two complementary datasets acquired with the ground-based instrument SINFONI (ESO/VLT). Title: CHARISMA: A Space Telescope for Planetary Science Authors: Young, C. L.; Sayanagi, K. M.; Wong, M. H.; Curry, S.; Jessup, K. L.; Becker, T.; Hendrix, A.; Chanover, N.; Milam, S.; Holler, B.; Holsclaw, G.; Peralta, J.; Clarke, J.; Spencer, J.; Kelley, M.; Luhmann, J.; MacDonnell, D.; Vervack, R.; Rutherford, K.; Fletcher, L.; de Pater, I.; Vilas, F.; Simon, A.; Siegmund, O.; Bell, J.; Delory, G.; Pitman, J.; Greathouse, T.; Wishnow, E.; Schneider, N.; Lillis, R.; Colwell, J.; Bowman, L.; Feaga, L. Bibcode: 2020LPICo2194.6012Y Altcode: No abstract at ADS Title: Measurement of diamond nucleation rates from hydrocarbons at conditions comparable to the interiors of icy giant planets Authors: Schuster, A. K.; Hartley, N. J.; Vorberger, J.; Döppner, T.; van Driel, T.; Falcone, R. W.; Fletcher, L. B.; Frydrych, S.; Galtier, E.; Gamboa, E. J.; Gericke, D. O.; Glenzer, S. H.; Granados, E.; MacDonald, M. J.; MacKinnon, A. J.; McBride, E. E.; Nam, I.; Neumayer, P.; Pak, A.; Prencipe, I.; Voigt, K.; Saunders, A. M.; Sun, P.; Kraus, D. Bibcode: 2020PhRvB.101e4301S Altcode: We present measurements of the nucleation rate into a diamond lattice in dynamically compressed polystyrene obtained in a pump-probe experiment using a high-energy laser system and in situ femtosecond x-ray diffraction. Different temperature-pressure conditions that occur in planetary interiors were probed. For a single shock reaching 70 GPa and 3000 K no diamond formation was observed, while with a double shock driving polystyrene to pressures around 150 GPa and temperatures around 5000 K nucleation rates between 1029 and 1034m-3 s-1 were recorded. These nucleation rates do not agree with predictions of the state-of-the-art theoretical models for carbon-hydrogen mixtures by many orders of magnitude. Our data suggest that there is significant diamond formation to be expected inside icy giant planets like Neptune and Uranus. Title: A Review of the in Situ Probe Designs from Recent Ice Giant Mission Concept Studies Authors: Simon, A. A.; Fletcher, L. N.; Arridge, C.; Atkinson, D.; Coustenis, A.; Ferri, F.; Hofstadter, M.; Masters, A.; Mousis, O.; Reh, K.; Turrini, D.; Witasse, O. Bibcode: 2020SSRv..216...17S Altcode: For the Ice Giants, atmospheric entry probes provide critical measurements not attainable via remote observations. Including the 2013-2022 NASA Planetary Decadal Survey, there have been at least five comprehensive atmospheric probe engineering design studies performed in recent years by NASA and ESA. International science definition teams have assessed the science requirements, and each recommended similar measurements and payloads to meet science goals with current instrument technology. The probe system concept has matured and converged on general design parameters that indicate the probe would include a 1-meter class aeroshell and have a mass around 350 to 400-kg. Probe battery sizes vary, depending on the duration of a post-release coast phase, and assumptions about heaters and instrument power needs. The various mission concepts demonstrate the need for advanced power and thermal protection system development. The many completed studies show an Ice Giant mission with an in situ probe is feasible and would be welcomed by the international science community. Title: Saturn atmospheric dynamics one year after Cassini: Long-lived features and time variations in the drift of the Hexagon Authors: Hueso, R.; Sánchez-Lavega, A.; Rojas, J. F.; Simon, A. A.; Barry, T.; Río-Gaztelurrutia, T. del; Antuñano, A.; Sayanagi, K. M.; Delcroix, M.; Fletcher, L. N.; García-Melendo, E.; Pérez-Hoyos, S.; Blalock, J.; Colas, F.; Gómez-Forrellad, J. M.; Gunnarson, J. L.; Peach, D.; Wong, M. H. Bibcode: 2020Icar..33613429H Altcode: 2019arXiv190913849H We examine Saturn's atmospheric dynamics with observations in the visible range from ground-based telescopes and Hubble Space Telescope (HST). We present a detailed analysis of observations acquired during 2018 obtaining drift rates of major meteorological systems from the equator to the north polar hexagon. A system of polar storms that appeared in the planet in March 2018 and remained active with a complex phenomenology at least until September is analyzed elsewhere (Sánchez-Lavega et al., 2019). Many of the regular cloud features visible in 2018 are long-lived and can be identified in Saturn images in 2017, and in some cases, for up to a decade using also Cassini ISS images. Without considering the polar storms, the most interesting long-lived cloud systems are:

i) A bright white spot in the Equatorial Zone that can be tracked continuously since 2014 with minimal changes in its zonal velocity, which was 444.3 ± 3.1 m s-1 in 2014 and 452.4 ± 1.7 m s-1 in 2018. This velocity is remarkably different from the zonal winds at the cloud level at its latitude during the Cassini mission, and is closer to zonal winds obtained at the time of the Voyagers flybys and to zonal winds from Cassini VIMS infrared images of the lower atmosphere.

ii) A large long-lived Anticyclone Vortex, here AV, that formed after the Great White Spot of 2010-2011. This vortex has changed significantly in visual contrast, drift rate and latitude with minor changes in size over the last years.

iii) A system of subpolar vortices at latitudes 60-65°N present at least since 2011. These vortices and additional atmospheric features here studied follow drift rates consistent with zonal winds obtained by Cassini.

We also present a study of the positions of the vertices of Saturn's north polar hexagon from 2015 to 2018. These measurements are compared with previous analyses during the Cassini mission (2007-2014), observations with HST in the 90s, and data from the Voyagers in 1980-1981 to explore the long-term variability of the hexagon's drift rate. We find variations in the drift rate of the hexagon through these epochs that can not be fit by seasonal changes in the polar area. Instead, the different drift rates reinforce the role of the North Polar Spot that was present in the Voyager epoch and in the early 90s to cause a faster drift rate of the hexagon at that time compared with the current slower one. Title: Origins Space Telescope (Origins): Solar System Science Authors: Ennico-Smith, K.; Milam, S.; Bauer, J.; Cordiner, M.; de Pater, I.; Fletcher, L.; Lis, D.; Lovell, A.; Moullet, A.; Orton, G.; Villanueva, G.; Origins Solar System Working Group Bibcode: 2020AAS...23517108E Altcode: The Origins Space Telescope (Origins) is a 2020 Decadal mission concept that will trace our cosmic history, from the formation of the first galaxies and the rise of metals and dust to the development of habitable worlds and present-day life. With more than three orders of magnitude improvement in sensitivity over prior far-infrared missions and access to a spectral range spanning nearly eight octaves (2.8-588 microns), Origins vastly expands the discovery space available to the community. Origins is also an agile observatory, capable of tracking moving objects > 60 mas/s, and executing rapid survey science. This presentation describes a sampling of Solar System science cases to illustrate the capabilities of this breakthrough mission. For example, Origins can advance our knowledge of the thermal history and present-day climate and circulation patterns of the Giant Planets, providing a ground-truth catalog of giant planet variability as a resource to the exoplanet community. Origins can deliver a survey of the sizes and thermal properties of small bodies in the outer Solar System, allowing us to probe the history and evolution of our Solar System. No survey has been done on this scale before. Origins can trace the origin of water on Earth and in our Solar System by determining the D/H ratio in hundreds of comets, providing, for the first time, a statistically-significant sample of this critical fingerprint for the origin of water on Earth. We thank NASA HQ, GSFC, JPL, and NASA-Ames for their support of the study. To learn more about Origins see our websites (https://origins.ipac.caltech.edu and https://asd.gsfc.nasa.gov/firs/) and report (https://asd.gsfc.nasa.gov/firs/docs/OriginsVolume1MissionConceptStudyReport.pdf). Title: A Multi-Spectral Analysis of Recent Perturbations to Jupiter's Great Red Spot in 2019 Authors: Orton, G. S.; Momary, T.; Sinclair, J. A.; Fujiyoshi, T.; Honda, M.; Rogers, J.; Foster, C.; Eichstädt, G.; Antuñano, A.; Fletcher, L. N.; Chowdhury, N.; Stallard, T.; Melin, H. Bibcode: 2019AGUFM.P21G3445O Altcode: In the early months of 2019, various amateur planetary observers recorded interactions between the Great Red Spot (GRS) and a series of ring-like vortices that were transported toward its northeastern side along the southern boundary of the South Equatorial Belt. Ultimately these were drawn into the Great Red Spot Hollow, a bright region surrounding the uniquely red-colored GRS itself. This resulted in their deformation and dissolution, as well as the formation of red-colored regions that became known as "flakes" within the Hollow on the western side of the GRS that appear to be as bright in "methane-band" (~890-nm) images as the interior of the GRS itself. We will report on the results of strategic imaging results on May, 27-28, 2019, from 2.3 to 24.5 µ m from the Subaru Telescope and the Infrared Telescope Facility that show surprising perturbations to the atmosphere and their aftermath. Title: Saturn's Rings: Atmsopheric Effects of Ring Shadow, Ring Shine, and Thermal Emission Authors: Edgington, S. G.; Atreya, S. K.; West, R. A.; Baines, K.; Fletcher, L. N. Bibcode: 2019AGUFM.P13B3511E Altcode: Cassini explored for nearly a half Saturnian year. During this epoch, in addition to seasonal solar inclination changes, the ring shadow moved from the northern hemisphere to covering a large region of the southern hemisphere. The intensity of both ultraviolet and visible sunlight penetrating through the rings varied depending on Saturn's axial tilt relative to the Sun and the optical thickness of each ring system, i.e. the rings act like semi-transparent venetian blinds. This effect magnifies the seasonal effect of axial tilt alone acting to reduce or even turn off photochemistry and haze generation, an effect exhibited by the presence of a bluish northern atmosphere in 2004 and color change to blue in the southern hemisphere after equinox. We report on the impact of the oscillating ring shadow, seasonal axial tilt, and solar cycle, on photochemistry of hydrocarbons, ammonia, and phosphine in Saturn's stratosphere and upper troposphere. The impact on the abundance of long-lived photochemical products leading to haze formation and on disequilibrium species is explored. Data from Cassini's CIRS, UVIS, and VIMS datasets that provide constraints for hazes and molecular abundances.

In addition to visible light reflected from the rings, UV photons have also been shown to reflect from the rings. This acts to enhance photolysis on the sunlit hemisphere. We examine the impact of ultraviolet ring-shine on the photochemistry of the upper atmosphere. Lastly, we examine the impact of thermal ring photons on the heating of the hemisphere upon which they shine.

The research described in this paper was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Copyright 2019 California Institute of Technology. Government sponsorship is acknowledged. Title: Longitudinal Variations in the Stratosphere of Uranus from the Spitzer Infrared Spectrometer Authors: Rowe-Gurney, N.; Fletcher, L. N.; Orton, G. S.; Roman, M. T.; Mainzer, A.; Moses, J. I.; De Pater, I.; Irwin, P. G. Bibcode: 2019AGUFM.P13B3504R Altcode: NASA's Spitzer Infrared Spectrometer (IRS) acquired mid-infrared (5-37 μm) disc-averaged spectra of Uranus very near its equinox over 21.7 hours on 16th to 17th of December 2007. A global-mean spectrum was constructed from observations of multiple longitudes, spaced equally around the planet, and have provided the opportunity for the most comprehensive globally-averaged characterisation of Uranus' temperature and composition ever obtained (Orton et al., 2014a,b). In this work, we analyse the disc-averaged spectra at four separate longitudes to shed light on the discovery of longitudinal variability occurring in Uranus' stratosphere during the 2007 equinox. We detect a variability of up to 15% at stratospheric altitudes sensitive to methane, ethane, and acetylene (∼ 0.1 mbar). The tropospheric hydrogen-helium continuum exhibits a negligible variation of less than 2%, constraining the phenomenon to the stratosphere. Observations from Keck II NIRCII in December 2007 (Sromovsky et al., 2009; de Pater et al., 2011) and VLT/VISIR in 2009 (Roman et al. in-prep) suggest possible links to these variations in the form of discrete meteorological features. It now seems clear that the variations are located in the bright polar cap of emission seen in the VLT observations. These variations were most obvious at the boundary between the equator and the polar cap (i.e., somewhere at mid latitudes). Building on the forward-modelling analysis of the global average study, we present full optimal estimation inversions (using the NEMESIS retrieval algorithm, Irwin et al., 2008) of the spectra at each longitude to distinguish between thermal and compositional variability. Title: IRTF-TEXES observations of stratospheric CH3 and CH4 emission at Jupiter's high latitudes Authors: Sinclair, J. A.; Greathouse, T. K.; Giles, R.; Antuñano, A.; Fouchet, T.; Bezard, B.; Clark, G. B.; Moses, J. I.; Hue, V.; Orton, G. S.; Fletcher, L. N.; Irwin, P. G. Bibcode: 2019AGUFM.P21G3444S Altcode: The neutral atmosphere, external magnetosphere and solar-wind environment of Jupiter are coupled within Jupiter's auroral regions. Energetic particles deposit their energy as deep as the 1-mbar level (or ~150 km above the 1-bar level) and modify the thermal structure and chemistry of the atmosphere (Sinclair et al., 2017, Icarus 292, 182-207, Sinclair et al., 2018, Icarus 300, 305-326). Clark et al., 2018 (JGR Space Physics 123, 7554-7567) recently performed a comparative analysis of Juno-JEDI (Jovian Electron Distribution Experiment, Mauk et al., 2017, SSR 213(1-4), 289-346) and HISAKI-EXCEED (Extreme Ultraviolet Spectroscope for Exospheric Dynamics, Yoshioka et al., 2013, P&SS 85, 250-260) ultraviolet observations of Jupiter's aurora. They found that the agreement between both datasets was optimized when CH4 and other hydrocarbons were allowed to be transported to higher altitudes in their atmospheric model. This suggests that a phenomenon within Jupiter's auroral regions is acting to increase the eddy diffusion coefficient and the height of the hydrocarbon homopause. In order to test this hypothesis, we present a retrieval analysis of IRTF-TEXES spectra of CH3 (methyl radical) and CH4 emission of Jupiter's high latitudes. Spectra were measured on February 12th (coincident with Juno's 18th perijove), April 16th and 21st 2019 (10 and 15 days after Juno's 19th perijove, respectively). A retrieval analysis was performed to derive the vertical profiles of temperature and CH3 abundance (from 20 mbar to 1 µbar) and their horizontal variation poleward of ±45º in latitude. Preliminary retrievals of spectra measured on April 16th 2019 demonstrate that the abundance of CH3 is enhanced over Jupiter's northern auroral region (60°N - pole, 150-220°W) compared to non-auroral longitudes in the same latitude band. This is suggestive that the production rate of CH3 is higher and/or the hydrocarbon homopause altitude is indeed higher in Jupiter's auroral regions. Title: Science Requirement Document (SRD) for the European Solar Telescope (EST) (2nd edition, December 2019) Authors: Schlichenmaier, R.; Bellot Rubio, L. R.; Collados, M.; Erdelyi, R.; Feller, A.; Fletcher, L.; Jurcak, J.; Khomenko, E.; Leenaarts, J.; Matthews, S.; Belluzzi, L.; Carlsson, M.; Dalmasse, K.; Danilovic, S.; Gömöry, P.; Kuckein, C.; Manso Sainz, R.; Martinez Gonzalez, M.; Mathioudakis, M.; Ortiz, A.; Riethmüller, T. L.; Rouppe van der Voort, L.; Simoes, P. J. A.; Trujillo Bueno, J.; Utz, D.; Zuccarello, F. Bibcode: 2019arXiv191208650S Altcode: The European Solar Telescope (EST) is a research infrastructure for solar physics. It is planned to be an on-axis solar telescope with an aperture of 4 m and equipped with an innovative suite of spectro-polarimetric and imaging post-focus instrumentation. The EST project was initiated and is driven by EAST, the European Association for Solar Telescopes. EAST was founded in 2006 as an association of 14 European countries. Today, as of December 2019, EAST consists of 26 European research institutes from 18 European countries. The Preliminary Design Phase of EST was accomplished between 2008 and 2011. During this phase, in 2010, the first version of the EST Science Requirement Document (SRD) was published. After EST became a project on the ESFRI roadmap 2016, the preparatory phase started. The goal of the preparatory phase is to accomplish a final design for the telescope and the legal governance structure of EST. A major milestone on this path is to revisit and update the Science Requirement Document (SRD). The EST Science Advisory Group (SAG) has been constituted by EAST and the Board of the PRE-EST EU project in November 2017 and has been charged with the task of providing with a final statement on the science requirements for EST. Based on the conceptual design, the SRD update takes into account recent technical and scientific developments, to ensure that EST provides significant advancement beyond the current state-of-the-art. The present update of the EST SRD has been developed and discussed during a series of EST SAG meetings. The SRD develops the top-level science objectives of EST into individual science cases. Identifying critical science requirements is one of its main goals. Those requirements will define the capabilities of EST and the post-focus instrument suite. The technical requirements for the final design of EST will be derived from the SRD. Title: Jupiter's Stratosphere in the Ultraviolet: inter-annual variability of acetylene and ethane Authors: Melin, H.; Fletcher, L. N. Bibcode: 2019AGUFM.P13B3503M Altcode: The ultraviolet spectrum of Jupiter between 150 and 200 nm is dominated by Rayleigh scattered sunlight, augmented by absorption from stratospheric acetylene and ethane, and tropospheric ammonia and phosphine. Acetylene and ethane are both photochemical products of methane, and their meridional distribution traces the global circulation in the stratosphere. However, they are observed to have very different distributions on the planet, attributable to their very different chemical lifetimes - ethane can persist for several Jupiter years, tracing the stratospheric circulation. Ammonia and phosphine are both tracers of vertical motions in the atmosphere, lifting these species up into the upper troposphere where they can be observed. Jupiter's Quasi Quadrennial Oscillation (QQO) is a four-year semi-regular temperature variation in the equatorial stratosphere of Jupiter, likely driven by gravity waves generated by the turbulent troposphere. Here, we analyse observations from the International Ultraviolet Explorer (IUE) space telescope and the Astro-1 & 2 Space Shuttle missions that carried the Hopkins Ultraviolet Telescope (HUT), obtained between 1978 and 1996, at a greater than yearly cadence, covering 1.5 jovian years. We examine how sensitive these observations are to the abundance of ethane, acetylene, ammonia and phosphine. Using the NEMESIS radiative transfer and retrieval code, we examine how the vertical profiles of acetylene and ethane evolve on jovian inter-annual, annual, seasonal, and QQO time-scales. We also explore retrievability of ammonia and phosphine abundance to examine how the vertical mixing changes over this period. Title: Rapid time variability of the UV spectral line profiles in a small flare - evidence of chromospheric turbulence and heating Authors: Fletcher, L.; Jeffrey, N. L. S.; Labrosse, N.; Simoes, P. J. D. A. Bibcode: 2019AGUFMSH13D3424F Altcode: We present observations of rapid variations in the spectral line profiles in the B-class flare SOL2016-12-06T10:36:58 detected by the Interface Region Imaging Spectograph (IRIS). The flare was observed at a cadence of 1.7s, a time resolution that allows us to detect variations during the flare rise and its rapid subsequent evolution, as follows: (i) For Si IV 1402.77Å, the line broadens significantly above its expected thermal width around 10 seconds prior to the flare's strong radiative signatures. Modelling shows that in this event the Si IV line is optically thin, so the evolving line broadening suggests the development of transition region turbulence, leading to flare heating; (ii) In the optically thick Mg II k line, formed deeper in the chromosphere, marked differences appear in the time profiles of the core and wing intensities, and there are also rapidly varying line asymmetries and a filling in of the pre-flare central reversal of this line. An increase in the line core width is also seen. We will discuss possible interpretations of the evolution these two lines in the context of evolving turbulence and chromospheric pressure, and opacity effects. Title: Herschel map of Saturn's stratospheric water, delivered by the plumes of Enceladus Authors: Cavalié, T.; Hue, V.; Hartogh, P.; Moreno, R.; Lellouch, E.; Feuchtgruber, H.; Jarchow, C.; Cassidy, T.; Fletcher, L. N.; Billebaud, F.; Dobrijevic, M.; Rezac, L.; Orton, G. S.; Rengel, M.; Fouchet, T.; Guerlet, S. Bibcode: 2019A&A...630A..87C Altcode: 2019arXiv190807399C Context. The origin of water in the stratospheres of giant planets has been an outstanding question ever since its first detection by the Infrared Space Observatory some 20 years ago. Water can originate from interplanetary dust particles, icy rings and satellites, and large comet impacts. Analyses of Herschel Space Observatory observations have proven that the bulk of Jupiter's stratospheric water was delivered by the Shoemaker-Levy 9 impacts in 1994. In 2006, the Cassini mission detected water plumes at the South Pole of Enceladus, which made the moon a serious candidate for Saturn's stratospheric water. Further evidence was found in 2011 when Herschel demonstrated the presence of a water torus at the orbital distance of Enceladus that was fed by the moon's plumes. Finally, water falling from the rings onto Saturn's uppermost atmospheric layers at low latitudes was detected during the final orbits of Cassini's end-of-mission plunge into the atmosphere.
Aims: In this paper, we use Herschel mapping observations of water in Saturn's stratosphere to identify its source.
Methods: We tested several empirical models against the Herschel-HIFI and -PACS observations, which were collected on December 30, 2010, and January 2, 2011, respectively.
Results: We demonstrate that Saturn's stratospheric water is not uniformly mixed as a function of latitude, but peaks at the equator and decreases poleward with a Gaussian distribution. We obtain our best fit with an equatorial mole fraction 1.1 ppb and a half width at half maximum of 25°, when accounting for a temperature increase in the two warm stratospheric vortices produced by Saturn's Great Storm of 2010-2011.
Conclusions: This work demonstrates that Enceladus is the main source of Saturn's stratospheric water.

Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. Title: Achievements of Hinode in the first eleven years Authors: Hinode Review Team; Al-Janabi, Khalid; Antolin, Patrick; Baker, Deborah; Bellot Rubio, Luis R.; Bradley, Louisa; Brooks, David H.; Centeno, Rebecca; Culhane, J. Leonard; Del Zanna, Giulio; Doschek, George A.; Fletcher, Lyndsay; Hara, Hirohisa; Harra, Louise K.; Hillier, Andrew S.; Imada, Shinsuke; Klimchuk, James A.; Mariska, John T.; Pereira, Tiago M. D.; Reeves, Katharine K.; Sakao, Taro; Sakurai, Takashi; Shimizu, Toshifumi; Shimojo, Masumi; Shiota, Daikou; Solanki, Sami K.; Sterling, Alphonse C.; Su, Yingna; Suematsu, Yoshinori; Tarbell, Theodore D.; Tiwari, Sanjiv K.; Toriumi, Shin; Ugarte-Urra, Ignacio; Warren, Harry P.; Watanabe, Tetsuya; Young, Peter R. Bibcode: 2019PASJ...71R...1H Altcode: Hinode is Japan's third solar mission following Hinotori (1981-1982) and Yohkoh (1991-2001): it was launched on 2006 September 22 and is in operation currently. Hinode carries three instruments: the Solar Optical Telescope, the X-Ray Telescope, and the EUV Imaging Spectrometer. These instruments were built under international collaboration with the National Aeronautics and Space Administration and the UK Science and Technology Facilities Council, and its operation has been contributed to by the European Space Agency and the Norwegian Space Center. After describing the satellite operations and giving a performance evaluation of the three instruments, reviews are presented on major scientific discoveries by Hinode in the first eleven years (one solar cycle long) of its operation. This review article concludes with future prospects for solar physics research based on the achievements of Hinode. Title: Jupiter's auroral-related stratospheric heating and chemistry III: Abundances of C2H4, CH3C2H, C4H2 and C6H6 from Voyager-IRIS and Cassini-CIRS Authors: Sinclair, J. A.; Moses, J. I.; Hue, V.; Greathouse, T. K.; Orton, G. S.; Fletcher, L. N.; Irwin, P. G. J. Bibcode: 2019Icar..328..176S Altcode: We present an analysis of Voyager-1-IRIS and Cassini-CIRS spectra of Jupiter's high latitudes acquired during the spacecrafts' respective flybys in November 1979 and January 2001. We performed a forward-model analysis in order to derive the abundances of ethylene (C2H4), methylacetylene (CH3C2H), diacetylene (C4H2) and benzene (C6H6) in Jupiter's northern and southern auroral regions. We also compared these abundances to: 1) lower-latitude abundances predicted by the Moses et al. (2005) 'Model A' photochemical model, henceforth 'Moses 2005A', and 2) abundances derived at non-auroral longitudes in the same latitude band. This paper serves as an extension of Sinclair et al. (2017b), where we retrieved the vertical profiles of temperature, C2H2 and C2H6 from similar datasets. We find that an enrichment of C2H4, CH3C2H and C6H6 with respect to lower-latitude abundances is required to fit the spectra of Jupiter's northern and southern auroral regions. For example, for CIRS 0.5 cm-1 spectra of Jupiter's southern auroral region, scale factor enrichments of 6.40-1.15+1.30 and 9.60-3.67+3.98 are required with respect to the Moses 2005A vertical profiles of C2H4 and C6H6, respectively, in order to fit the spectral emission features of these species at ∼950 and ∼674 cm-1. Similarly, in order to fit the CIRS 2.5 cm-1 spectra of Jupiter's northern auroral region, scale factor enrichments of 1.60-0.21+0.37, 3.40-1.69+1.89 and 15.00-4.02+4.01 with respect to the Moses 2005A vertical profiles of C2H4, CH3C2H and C6H6 were required, respectively. Outside of Jupiter's auroral region in the same latitude bands, only upper-limit abundances of C2H4, CH3C2H and C6H6 could be determined due to the limited sensitivity of the measurements, the weaker emission features combined with cooler stratospheric temperatures (and therefore decreased thermal emission) of these regions. Nevertheless, for a subset of the observations, derived abundances of C2H4 and C6H6 in Jupiter's auroral regions were higher (by 1 σ) with respect to upper-limit abundances derived outside the auroral region in the same latitude band. This is suggestive that the influx of energetic ions and electrons from the Jovian magnetosphere and external solar-wind environment into the neutral atmosphere in Jupiter's auroral regions drives enhanced ion-related chemistry, as has also been inferred from Cassini observations of Saturn's high latitudes (Fletcher et al., 2018; Guerlet et al., 2015; Koskinen et al., 2016). We were not able to constrain the abundance of C4H2 in either Jupiter's auroral regions or non-auroral regions due to its lower (predicted) abundance and weaker emission feature. Thus, only upper-limit abundances were derived in both locations. From CIRS 2.5 cm-1 spectra, the upper limit abundance of C4H2 corresponds to a scale factor enhancement of 45.6 and 23.8 with respect to the Moses 2005A vertical profile in Jupiter's non-auroral and auroral regions. Title: The Role of Energy Diffusion in the Deposition of Energetic Electron Energy in Solar and Stellar Flares Authors: Jeffrey, Natasha L. S.; Kontar, Eduard P.; Fletcher, Lyndsay Bibcode: 2019ApJ...880..136J Altcode: 2019arXiv190601887J During solar flares, a large fraction of the released magnetic energy is carried by energetic electrons that transfer and deposit energy in the Sun’s atmosphere. Electron transport is often approximated by a cold thick-target model, assuming that electron energy is much larger than the temperature of the ambient plasma, and electron energy evolution is modeled as a systematic loss. Using kinetic modeling of electrons, we reevaluate the transport and deposition of flare energy. Using a full collisional warm-target model (WTM), we account for electron thermalization and for the properties of the ambient coronal plasma such as its number density, temperature and spatial extent. We show that the deposition of nonthermal electron energy in the lower atmosphere is highly dependent on the properties of the flaring coronal plasma. In general, thermalization and a reduced WTM energy loss rate leads to an increase of nonthermal energy transferred to the chromosphere, and the deposition of nonthermal energy at greater depths. The simulations show that energy is deposited in the lower atmosphere initially by high-energy nonthermal electrons, and later by lower energy nonthermal electrons that partially or fully thermalize in the corona, over timescales of seconds, unaccounted for in previous studies. This delayed heating may act as a diagnostic of both the injected nonthermal electron distribution and the coronal plasma, vital for constraining flare energetics. Title: The plasmoid instability in a confined solar flare Authors: MacTaggart, David; Fletcher, Lyndsay Bibcode: 2019MNRAS.486L..96M Altcode: 2019MNRAS.tmpL..70M; 2019arXiv190501201M Eruptive flares (EFs) are associated with erupting filaments and, in some models, filament eruption drives flare reconnection. Recently, however, observations of a confined flare (CF) have revealed all the hallmarks of an EF (impulsive phase, flare ribbons, etc.) without the filament eruption itself. Therefore, if the filament is not primarily responsible for impulsive flare reconnection, what is? In this Letter, we argue, based on mimimal requirements, that the plasmoid instability is a strong candidate for explaining the impulsive phase in the observed CF. We present magnetohydrodynamic simulation results of the non-linear development of the plasmoid instability, in a model active region magnetic field geometry, to strengthen our claim. We also discuss how the ideas described in this Letter can be generalized to other situations, including EFs. Title: Fast Solar Image Classification Using Deep Learning and Its Importance for Automation in Solar Physics Authors: Armstrong, John A.; Fletcher, Lyndsay Bibcode: 2019SoPh..294...80A Altcode: 2019arXiv190513575A The volume of data being collected in solar physics has exponentially increased over the past decade and with the introduction of the Daniel K. Inouye Solar Telescope (DKIST) we will be entering the age of petabyte solar data. Automated feature detection will be an invaluable tool for post-processing of solar images to create catalogues of data ready for researchers to use. We propose a deep learning model to accomplish this; a deep convolutional neural network is adept at feature extraction and processing images quickly. We train our network using data from Hinode/Solar Optical Telescope (SOT) Hα images of a small subset of solar features with different geometries: filaments, prominences, flare ribbons, sunspots and the quiet Sun (i.e. the absence of any of the other four features). We achieve near perfect performance on classifying unseen images from SOT (≈ 99.9%) in 4.66 seconds. We also for the first time explore transfer learning in a solar context. Transfer learning uses pre-trained deep neural networks to help train new deep learning models i.e. it teaches a new model. We show that our network is robust to changes in resolution by degrading images from SOT resolution (≈0.33″ at λ =6563 Å) to Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) resolution (≈1.2″) without a change in performance of our network. However, we also observe where the network fails to generalise to sunspots from SDO/AIA bands 1600/1700 Å due to small-scale brightenings around the sunspots and prominences in SDO/AIA 304 Å due to coronal emission. Title: Spectral Evidence for Heating at Large Column Mass in Umbral Solar Flare Kernels. I. IRIS Near-UV Spectra of the X1 Solar Flare of 2014 October 25 Authors: Kowalski, Adam F.; Butler, Elizabeth; Daw, Adrian N.; Fletcher, Lyndsay; Allred, Joel C.; De Pontieu, Bart; Kerr, Graham S.; Cauzzi, Gianna Bibcode: 2019ApJ...878..135K Altcode: 2019arXiv190502111K The GOES X1 flare SOL2014-10-25T17:08:00 was a three-ribbon solar flare observed with the Interface Region Imaging Spectrograph (IRIS) in the near-UV (NUV) and far-UV. One of the flare ribbons crossed a sunspot umbra, producing a dramatic, ∼1000% increase in the NUV continuum radiation. We comprehensively analyze the UV spectral data of the umbral flare brightenings, which provide new challenges for radiative-hydrodynamic modeling of the chromospheric velocity field and the white-light continuum radiation. The emission line profiles in the umbral flare brightenings exhibit redshifts and profile asymmetries, but these are significantly smaller than in another, well-studied X-class solar flare. We present a ratio of the NUV continuum intensity to the Fe II λ2814.45 intensity. This continuum-to-line ratio is a new spectral diagnostic of significant heating at high column mass (log m/[g cm-2] > -2) during solar flares because the continuum and emission line radiation originate from relatively similar temperatures but moderately different optical depths. The full spectral readout of these IRIS data also allow for a comprehensive survey of the flaring NUV landscape: in addition to many lines of Fe II and Cr II, we identify a new solar flare emission line, He I λ2829.91 (as previously identified in laboratory and early-type stellar spectra). The Fermi/GBM hard X-ray data provide inputs to radiative-hydrodynamic models (which will be presented in Paper II) in order to better understand the large continuum-to-line ratios, the origin of the white-light continuum radiation, and the role of electron beam heating in the low atmosphere. Title: A brightening of Jupiter's auroral 7.8-μm CH4 emission during a solar-wind compression Authors: Sinclair, J. A.; Orton, G. S.; Fernandes, J.; Kasaba, Y.; Sato, T. M.; Fujiyoshi, T.; Tao, C.; Vogt, M. F.; Grodent, D.; Bonfond, B.; Moses, J. I.; Greathouse, T. K.; Dunn, W.; Giles, R. S.; Tabataba-Vakili, F.; Fletcher, L. N.; Irwin, P. G. J. Bibcode: 2019NatAs...3..607S Altcode: 2019NatAs.tmp..243S Enhanced mid-infrared emission from CH4 and other stratospheric hydrocarbons has been observed coincident with Jupiter's ultraviolet auroral emission1-3. This suggests that auroral processes and the neutral stratosphere of Jupiter are coupled; however, the exact nature of this coupling is unknown. Here we present a time series of Subaru-COMICS images of Jupiter measured at a wavelength of 7.80 μm on 11-14 January, 4-5 February and 17-20 May 2017. These data show that both the morphology and magnitude of the auroral CH4 emission vary on daily timescales in relation to external solar-wind conditions. The southern auroral CH4 emission increased in brightness temperature by about 3.8 K between 15:50 ut, 11 January and 12:57 ut, 12 January, during a predicted solar-wind compression. During the same compression, the northern auroral emission exhibited a duskside brightening, which mimics the morphology observed in the ultraviolet auroral emission during periods of enhanced solar-wind pressure4,5. These results suggest that changes in external solar-wind conditions perturb the Jovian magnetosphere in such a way that energetic particles are accelerated into the planet's atmosphere, deposit their energy as deep as the neutral stratosphere, and modify the thermal structure, the abundance of CH4 or the population of energy states of CH4. We also find that the northern and southern auroral CH4 emission evolved independently between the January, February and May images, as has been observed at X-ray wavelengths over shorter timescales6 and at mid-infrared wavelengths over longer timescales7. Title: First Spectral Analysis of a Solar Plasma Eruption Using ALMA Authors: Rodger, Andrew S.; Labrosse, Nicolas; Wedemeyer, Sven; Szydlarski, Mikolaj; Simões, Paulo J. A.; Fletcher, Lyndsay Bibcode: 2019ApJ...875..163R Altcode: 2019arXiv190201319R The aim of this study is to demonstrate how the logarithmic millimeter continuum gradient observed using the Atacama Large Millimeter/submillimeter Array (ALMA) may be used to estimate optical thickness in the solar atmosphere. We discuss how using multiwavelength millimeter measurements can refine plasma analysis through knowledge of the absorption mechanisms. Here we use subband observations from the publicly available science verification (SV) data, while our methodology will also be applicable to regular ALMA data. The spectral resolving capacity of ALMA SV data is tested using the enhancement coincident with an X-ray bright point and from a plasmoid ejection event near active region NOAA12470 observed in Band 3 (84-116 GHz) on 2015 December 17. We compute the interferometric brightness temperature light curve for both features at each of the four constituent subbands to find the logarithmic millimeter spectrum. We compared the observed logarithmic spectral gradient with the derived relationship with optical thickness for an isothermal plasma to estimate the structures’ optical thicknesses. We conclude, within 90% confidence, that the stationary enhancement has an optical thickness between 0.02 ≤ τ ≤ 2.78, and that the moving enhancement has 0.11 ≤ τ ≤ 2.78, thus both lie near to the transition between optically thin and thick plasma at 100 GHz. From these estimates, isothermal plasmas with typical Band 3 background brightness temperatures would be expected to have electron temperatures of ∼7370-15300 K for the stationary enhancement and between ∼7440 and 9560 K for the moving enhancement, thus demonstrating the benefit of subband ALMA spectral analysis. Title: RADYNVERSION: Learning to Invert a Solar Flare Atmosphere with Invertible Neural Networks Authors: Osborne, Christopher M. J.; Armstrong, John A.; Fletcher, Lyndsay Bibcode: 2019ApJ...873..128O Altcode: 2019arXiv190108626O During a solar flare, it is believed that reconnection takes place in the corona followed by fast energy transport to the chromosphere. The resulting intense heating strongly disturbs the chromospheric structure and induces complex radiation hydrodynamic effects. Interpreting the physics of the flaring solar atmosphere is one of the most challenging tasks in solar physics. Here we present a novel deep-learning approach, an invertible neural network, to understanding the chromospheric physics of a flaring solar atmosphere via the inversion of observed solar line profiles in Hα and Ca II λ8542. Our network is trained using flare simulations from the 1D radiation hydrodynamic code RADYN as the expected atmosphere and line profile. This model is then applied to single pixels from an observation of an M1.1 solar flare taken with the Swedish 1 m Solar Telescope/CRisp Imaging SpectroPolarimeter instrument just after the flare onset. The inverted atmospheres obtained from observations provide physical information on the electron number density, temperature, and bulk velocity flow of the plasma throughout the solar atmosphere ranging from 0 to 10 Mm in height. The density and temperature profiles appear consistent with the expected atmospheric response, and the bulk plasma velocity provides the gradients needed to produce the broad spectral lines while also predicting the expected chromospheric evaporation from flare heating. We conclude that we have taught our novel algorithm the physics of a solar flare according to RADYN and that this can be confidently used for the analysis of flare data taken in these two wavelengths. This algorithm can also be adapted for a menagerie of inverse problems providing extremely fast (∼10 μs) inversion samples. Title: Photochemistry in Saturn's Atmosphere: Ring Shadow and Ring Reflection Authors: Edgington, S. G.; Atreya, S. K.; Wilson, E. H.; Baines, K. H.; West, R. A.; Bjoraker, G. L.; Fletcher, L. N.; Momary, T. W. Bibcode: 2019LPI....50.3053E Altcode: This work studies the generation and variation of haze in Saturn's atmosphere and the chemistry and solar-seasonal insolation that modulates it. Title: The Europa Imaging System (EIS): High-Resolution, 3-D Insight into Europa's Geology, Ice Shell, and Potential for Current Activity Authors: Turtle, E. P.; McEwen, A. S.; Collins, G. C.; Daubar, I. J.; Ernst, C. M.; Fletcher, L.; Hansen, C. J.; Hawkins, S. E.; Hayes, A. G.; Humm, D.; Hurford, T. A.; Kirk, R. L.; Kutsop, N.; Barr Mlinar, A. C.; Nimmo, F.; Patterson, G. W.; Phillips, C. B.; Pommerol, A.; Prockter, L.; Quick, L. C.; Reynolds, E. L.; Slack, K. A.; Soderblom, J. M.; Sutton, S.; Thomas, N.; Bland, M. Bibcode: 2019LPI....50.3065T Altcode: Cameras to observe / Europa's fractured landscapes / Ice shell mysteries. Title: Radynversion: Solar atmospheric properties during a solar flare Authors: Osborne, Christopher M. J.; Armstrong, John A.; Fletcher, Lyndsay Bibcode: 2019ascl.soft02008O Altcode: Radynversion infers solar atmospheric properties during a solar flare. The code is based on an Invertible Neural Network (INN) that is trained to learn an approximate bijective mapping between the atmospheric properties of electron density, temperature, and bulk velocity (all as a function of altitude), and the observed Hα and Ca II λ8542 line profiles. As information is lost in the forward process of radiation transfer, this information is injected back into the model during the inverse process by means of a latent space; the training allows this latent space to be filled using an n-dimensional unit Gaussian distribution, where n is the dimensionality of the latent space. The code is based on a model trained by simulations made by RADYN, a 1D non-equilibrium radiation hydrodynamic model with good optically thick radiation treatment that does not consider magnetic effects. Title: The Spectral Content of SDO/AIA 1600 and 1700 Å Filters from Flare and Plage Observations Authors: Simões, Paulo J. A.; Reid, Hamish A. S.; Milligan, Ryan O.; Fletcher, Lyndsay Bibcode: 2019ApJ...870..114S Altcode: 2018arXiv180801488S The strong enhancement of the ultraviolet emission during solar flares is usually taken as an indication of plasma heating in the lower solar atmosphere caused by the deposition of the energy released during these events. Images taken with broadband ultraviolet filters by the Transition Region and Coronal Explorer and Atmospheric Imaging Assembly (AIA; 1600 and 1700 Å) have revealed the morphology and evolution of flare ribbons in great detail. However, the spectral content of these images is still largely unknown. Without knowledge of the spectral contribution to these UV filters, the use of these rich imaging data sets is severely limited. Aiming to solve this issue, we estimate the spectral contributions of the AIA UV flare and plage images using high-resolution spectra in the range 1300-1900 Å from the Skylab NRL SO82B spectrograph. We find that the flare excess emission in AIA 1600 Å is dominated by the C IV 1550 Å doublet (26%), Si I continua (20%), with smaller contributions from many other chromospheric lines such as C I 1561 and 1656 Å multiplets, He II 1640 Å, and Si II 1526 and 1533 Å. For the AIA 1700 Å band, the C I 1656 Å multiplet is the main contributor (38%), followed by He II 1640 (17%), and accompanied by a multitude of other, weaker chromospheric lines, with minimal contribution from the continuum. Our results can be generalized to state that the AIA UV flare excess emission is of chromospheric origin, while plage emission is dominated by photospheric continuum emission in both channels. Title: Water and Volatiles in the Outer Solar System Authors: Grasset, O.; Castillo-Rogez, J.; Guillot, T.; Fletcher, L. N.; Tosi, F. Bibcode: 2019dwpp.book..191G Altcode: No abstract at ADS Title: Continuum emission enhancements and penumbral changes observed during flares by IRIS, ROSA, and Hinode Authors: Zuccarello, F.; Guglielmino, S. L.; Capparelli, V.; Mathioudakis, M.; Keys, P.; Fletcher, L.; Criscuoli, S.; Falco, M.; Murabito, M. Bibcode: 2019NCimC..42...13Z Altcode: 2019arXiv190101732Z In this paper we describe observations acquired by satellite instruments ( Hinode/SOT and IRIS) and ground-based telescopes (ROSA@DST) during two consecutive C7.0 and X1.6 flares occurred in active region NOAA 12205 on 2014 November 7. The analysis of these data show the presence of continuum enhancements during the evolution of the events, observed both in ROSA images and in IRIS spectra. Moreover, we analyze the role played by the evolution of the δ sunspots of the active region in the flare triggering, indicating the disappearance of a large portion of penumbra around these sunspots. Title: Contemporaneous VLA and ALMA observations of Jupiter during the Juno mission Authors: De Pater, I.; Sault, R. J.; Mockel, C.; Moullet, A.; Butler, B. J.; Fletcher, L. N.; deBoer, D.; Wong, M. H.; Orton, G.; Janssen, M. A.; Cosentino, R.; Villard, E.; Bjoraker, G. L. Bibcode: 2018AGUFM.P33F3897D Altcode: In early January 2017, between Juno's perijoves PJ3 and PJ4 (near its originally planned PJ8) we imaged Jupiter with the Very Large Array (VLA) at 8-12 GHz and with ALMA at 100 and 230 GHz. We will inter-compare these datasets, and compare them with VLA data obtained in 2014, and the Juno Microwave Radiometer (MWR) data obtained during PJ1. We will further compare these data with contemporaneous HST, Gemini 5-micron, near-IR IRTF, and mid-IR VLT and Subaru data. The prior VLA maps of Jupiter, obtained in 2014 at frequencies between 3 and 37 GHz, were analyzed in detail to derive the ammonia abundance as a function of depth and latitude for our longitude-smeared maps. With these ammonia profiles, we can match the nadir brightness temperatures as measured by Juno/MWR during PJ1 very well. Although our VLA ammonia profiles match the NH3 profiles derived from the Juno data by the Juno team reasonably well in the Equatorial Zone and North Equatorial Belt, there are noticeable differences at other latitudes.

References:

de Pater et al., 2016. Science, 352, 1198-1201.

de Pater et al., 2018. Icarus, submitted.

Li et al., 2017. GRL, 10.1002/2017GL073159. Title: Meeting contribution: Exploring the weather of the giant planets via professional-amateur collaboration Authors: Fletcher, L. Bibcode: 2018JBAA..128..374F Altcode: No abstract at ADS Title: Mid-infrared spectra and images of Jupiter's auroral regions during perijoves 11 - 15 Authors: Sinclair, J. A.; Orton, G.; Greathouse, T. K.; Giles, R.; Kasaba, Y.; Sato, T. M.; Watanabe, H.; Tao, C.; Gladstone, R.; Clark, G. B.; Fletcher, L. N.; Moses, J. I.; Irwin, P. G.; Tabataba-Vakili, F. Bibcode: 2018AGUFM.P33F3892S Altcode: Energetic charged particles from the Jovianmagnetosphere penetrate the atmosphere in the polar regions and deposit their energy into the neutral atmosphere to pressures as deep as the 1-mbar level (or approximately 150 km above the 1 bar level). The resulting precipitation, ion drag and joule heating warms the neutral stratosphere and modifies the hydrocarbon chemistry (e.g. Sinclair et al., 2017a, Icarus 292, 182-207, Sinclair et al., 2018, Icarus 300, 305-326). This coupling of the neutral stratosphere and the magnetosphere can be sensed by the mid-infrared emission of stratospheric CH4, C2H2, C2H4and further hydrocarbon species. Mid-infrared measurements of Jupiter's auroral regions were performed near-contemporaneously with perijoves (PJ) 11-15 in order to sense the atmosphere-magnetosphere coupling at stratospheric altitudes, a region poorly sampled by Juno's instrumentation. High-spatial resolution 7.8-μm images of Jupiter's stratospheric CH4emission were measured by Subaru-COMICS (Kataza et al., 2000, Optical and IR Telescope Instrumentation and Detectors, 4008 1144-1152) on March 31-April 1st(PJ12), May 24-25th(PJ13). The morphology of CH4auroral emission will be compared with Juno and HST measurements of the ultraviolet auroral emission to explore the correlation of high UV color ratios, inferred to be driven by lateral Pedersen currents, with heating of the neutrals. High-spectral resolution IRTF-TEXES (Lacy et al., 2002, PASP 114, 153-168) measurements of CH4, C2H2, C2H4emission were acquired on February 9-12 (PJ11) and July 11-16 (PJ14). A retrieval analysis will be conducted to derive three-dimensional maps (altitude, latitude, longitude) of temperature and hydrocarbon abundances at Jupiter's high latitudes. New constraints on the vertical profile of CH4in Jupiter's auroral region (Clark et al., 2018, under review) will be adopted in this analysis to explore the effects on retrieved parameters. Both datasets will be compared with measurements supporting previous perijoves and the approach phase of Juno to Jupiter to explore the longer-term variability of the auroral stratosphere. Title: Notes and News: 'New Views of Jupiter': Pro-Am collaborations during and beyond the NASA Juno mission Authors: Rogers, J. H.; Fletcher, L. Bibcode: 2018JBAA..128..321R Altcode: An illustrated report of a pro-am workshop hosted by the Royal Astronomical Society in Burlington House, London, on 2018 May 10-11 and on the second day in the equally handsome and historic rooms of the Linnean Society next door. It was organised by Dr John Rogers (BAA) and Dr Leigh Fletcher (University of Leicester), as a follow-up to the workshop in Nice two years earlier [BAA Journal vol.126 p.199, 2016]. The workshop was principally funded by EuroPlanet with funding from the European Union, with a contribution from the European Research Council, and the RAS provided the venue and staff free of charge. Title: Photochemistry in Saturn's Atmosphere: Ring Shadow and Ring Reflection Authors: Edgington, S. G.; Atreya, S. K.; Wilson, E. H.; Baines, K. H.; West, R. A.; Bjoraker, G. L.; Fletcher, L. N.; Momary, T. Bibcode: 2018AGUFM.P43E3814E Altcode: After over thirteen years in Saturn orbit, Cassini observed for half a Saturnian year. During this epoch, the ring shadow moved from its northernmost extent to its southernmost. Acting like Venetian blinds, the rings would modulate both ultraviolet and visible sunlight penetrating through the rings. At the same time, both visible and ultraviolet light would be reflected from the sunlit side of the rings on the already sunlit hemisphere. Total insolation at any particular latitude would vary depending on Saturn's axis relative to the Sun, the optical thickness of each ring system, and ring reflectivity. These factors effectively magnify seasonal effects due to axial tilt alone, further influencing photochemical cycles and haze generation. This effect was observed with the transformation of the northern hemisphere from a relatively clear, blue Rayleigh-scattering atmosphere in 2004 to a smoggy, salmon color over the mission. We report on insolation over Saturn's disk accounting for axis tilt, ring transmission and reflectance, and solar cycle over Voyager and Cassini epochs. Impact on photolysis of key hydrocarbons in Saturn's thermosphere, stratosphere, and troposphere are explored and limits on production-loss rates and abundance of long-lived photochemical products leading to haze formation are placed. We assess the impact of insolation on a disequilibrium species (e.g. phosphine) whose presence in the upper troposphere can be used as a tracer of convective processes in the deeper atmosphere. Analysis of Cassini's CIRS, UVIS, and VIMS datasets are used to provide constrains on evolving haze content. Comparison of hazes at mid-latitudes will be contrasted to those within Saturn's hexagonal jet stream to understand evolution from a hazeless atmosphere to a hazy one. We explore how this jet stream acts like a barrier to transport, isolating the north polar region from photochemical hazes generate outside of it.

The research described in this paper was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Copyright 2018 California Institute of Technology. Government sponsorship is acknowledged. Title: The development of lower-atmosphere turbulence early in a solar flare Authors: Jeffrey, N. L. S.; Fletcher, L.; Labrosse, N.; Simões, P. J. A. Bibcode: 2018SciA....4.2794J Altcode: 2018arXiv181209906J We present the first observational study of the onset and evolution of solar flare turbulence in the lower solar atmosphere on an unprecedented time scale of 1.7 s using the Interface Region Imaging Spectrograph observing plasma at a temperature of 80,000 K. At this time resolution, nonthermal spectral line broadening, indicating turbulent velocity fluctuations, precedes the flare onset at this temperature and is coincident with net blue-shifts. The broadening decreases as the flare brightens and then oscillates with a period of 10 s. These observations are consistent with turbulence in the lower solar atmosphere at the flare onset, heating that region as it dissipates. This challenges the current view of energy release and transport in the standard solar flare model, suggesting that turbulence partly heats the lower atmosphere. Title: Spatially-Resolved Spectroscopy of the Ice Giants Atmospheres: Clouds, Seasonal Changes, and the Future in IR with JWST MIRI Authors: Roman, M. T.; Fletcher, L. N.; Banfield, D. J.; Gierasch, P. J. Bibcode: 2018AGUFM.P31B..05R Altcode: We present results from an analysis of spatially-resolved near-IR spectra of Uranus and Neptune and compare aerosol distributions and observed changes over a period of six years. Data were acquired from 2001 to 2007 using the 200-inch ( 5.1m) Hale Telescope and the Palomar High Angular Resolution Observer (PHARO) near-infrared adaptive optics (AO) camera system. Latitudinal variations in aerosols are interpreted in context of notional circulation models, while temporal changes suggest potential seasonal effects. We infer significant reduction in aerosol scattering optical thickness in southern latitudes between 2001 and 2007 on Uranus, in agreement with trends reported in studies covering part of the same period using different data and retrieval algorithms. For Neptune, latitudinal variations in the higher aerosols are consistent with upwelling at mid-latitudes, consistent with circulation inferred from IR spectra, with the greatest aerosol abundances in peaking in 2002 before reaching a minimum in 2006/2007. Best fits to both planets are consistent with polar depletion of methane in the tropopause (>2 bar). Stratospheric methane abundances are poorly constrained in the near IR, but generally consistent with lower values on Uranus and values near saturation Neptune.

A far greater understanding of the cloud level and stratosphere will come with observations from the James Webb Space Telescope (JWST). We look ahead to how the JWST MIRI instrument will provide global, spatially resolved 5-30 μm spectroscopy of Uranus and Neptune, thus providing an unprecedented picture of atmospheric temperatures, winds, and composition from the troposphere to the stratosphere. MIRI spectra will offer unique constraints for radiative, dynamical, and chemical models of the ice giant atmospheres and lead the way for future spacecraft missions. Title: Cyclone-related lightning near Juno's 6th orbit Authors: Wong, M. H.; Brown, S. T.; Fletcher, L. N.; Bjoraker, G. L.; De Pater, I.; Simon, A. A. Bibcode: 2018AGUFM.P33F3891W Altcode: The densest cluster of Juno MWR lightning strikes on perijove 6 (PJ6) occurred near 49 N planetographic latitude (Brown et al. 2018; DOI:10.1038/s41586-018-0156-5). Hubble imaging reveals a cyclonic vortex at this location.

Assuming the results of Romps et al. (2014; DOI:10.1126/science.1259100) apply to Jupiter as well as the Earth, Jupiter's cyclones are likely to be heavily-precipitating systems, explaining observations of depleted volatiles in microwave spectral imaging data (de Pater et al. 2016; DOI:10.1126/science.aaf2210). Ground-based thermal infrared imaging and spectra show that anomalies in temperature, composition, and cloud structure are common in low-latitude cyclonic vortices of different types. These infrared data were acquired in early 2017 using VLT/VISIR, Gemini NIRI, Keck NIRSPEC, and IRTF iSHELL. Hubble imaging data constrain some clouds to be deeper than 4 bar (presumably water clouds), particularly in the PJ6 cyclone with strong lightning activity. Large cyclones feature differences in high-altitude particle properties relative to their surroundings, consistent with downwelling and sublimation of haze particles in the upper troposphere. Warm, dry, and less-hazy conditions in the upper part of cyclones are consistent with downwelling aloft, while deep water clouds and lightning are consistent with upwelling at depth, precisely the inverse of the circulation within anticyclonic vortices according to Marcus et al. (2013; DOI:10.1115/1.4007666). This vortex structure suggests that midplanes of cyclones with lightning activity lie between the upper troposphere and the water cloud layer. Cyclones without water clouds and lightning may exist if their midplanes lie deeper than the water cloud layer. Title: Detection of Three-minute Oscillations in Full-disk Lyman-alpha Emission during a Solar Flare Authors: Milligan, Ryan O.; Fleck, Bernhard; Ireland, Jack; Fletcher, Lyndsay; Dennis, Brian R. Bibcode: 2018csc..confE..36M Altcode: In a recent study of spatially-integrated Lyman-alpha line emission (Lya, 1216A) from GOES/EUVS, we detected the presence of acoustic 3-minute oscillations during an X-class solar flare. Similar periodicities were also found - in phase - in Lyman continuum data from SDO/EVE, and the 1600A and 1700A channels on SDO/AIA. The implication is that the chromosphere responds dynamically at its acoustic cutoff frequency to an impulsive injection of energy. Since the 3-minute period was not detected at hard X-ray energies in RHESSI data we can state that this 3-minute oscillation does not depend on the rate of energisation of non-thermal electrons. This finding suggests that chromospheric mechanical energy should be included in the flare energy budget, and that fluctuations in Lya emission may influence the composition and dynamics of planetary atmospheres during periods of high activity. Knowledge of the behaviour of this emission during flares could be important when interpreting future science results from the EUI instrument on Solar Orbiter which will obtain high cadence images in Lya. Title: The spectral content of SDO/AIA 1600 and 1700 A filters from flare and plage observations Authors: Simoes, Paulo; Reid, Hamish; Milligan, Ryan; Fletcher, Lyndsay Bibcode: 2018csc..confE.125S Altcode: The strong enhancement of the ultraviolet emission during solar flares is usually taken as an indication of plasma heating in the low solar atmosphere caused by the deposition of the energy released during these events. Images taken with broadband ultraviolet filters by the Transition Region and Coronal Explorer (TRACE) and Atmospheric Imaging Assembly (AIA 1600 and 1700 Å) have revealed the morphology and evolution of flare ribbons in great detail. However, the spectral content of these images is still largely unknown. Without the knowledge of the spectral contribution to these UV filters, the use of these rich imaging datasets is severely limited. Aiming to solve this issue, we estimate the spectral contributions of the AIA UV flare and plage images using high-resolution spectra in the range 1300 to 1900 Å from the Skylab NRL SO82B spectrograph. We find that the flare excess emission in AIA 1600 Å is composed of the C IV 1550 Å doublet (26%), Si I continua (20%), with smaller contributions from many other chromospheric lines such as C I 1561 and 1656 Å multiplets, He II 1640 Å, Si II 1526 and 1533 Å. For the AIA 1700 Å band, C I 1656 Å multiplet is the main contributor (38%), followed by He II 1640 (17%), and accompanied by a multitude of other chromospheric lines, with minimal contribution from the continuum. Our results can be generalized to state that the AIA UV flare excess emission is of chromospheric origin, while plage emission is dominated by photospheric continuum emission in both channels. Title: Characterization of Mesoscale Waves in the Jupiter NEB by Jupiter InfraRed Auroral Mapper on board Juno Authors: Adriani, A.; Moriconi, M. L.; Altieri, F.; Sindoni, G.; Ingersoll, A. P.; Grassi, D.; Mura, A.; Atreya, S. K.; Orton, G.; Lunine, J. I.; Fletcher, L. N.; Simon, A. A.; Melin, H.; Tosi, F.; Cicchetti, A.; Noschese, R.; Sordini, R.; Levin, S.; Bolton, J.; Plainaki, C.; Olivieri, A. Bibcode: 2018AJ....156..246A Altcode: In 2017, the Jupiter InfraRed Auroral Mapper (JIRAM), on board the NASA-ASI Juno mission, observed a wide longitude region (50° W-80° E in System III) that was perturbed by a wave pattern centered at 15° N in the Jupiter’s North Equatorial Belt (NEB). We analyzed JIRAM data acquired on 2017 July 10 using the M-channel and on 2017 February 2 with the spectrometer. The two observations occurred at different times and at slightly different latitudes. The waves appear as clouds blocking the deeper thermal emission. The wave crests are oriented north-south, and the typical wave packet contains 10 crests and 10 troughs. We used Fourier analysis to rigorously determine the wavenumbers associated with the observed patterns at a confidence level of 90%. Wavelet analysis was also used to constrain the spatial localization of the largest energies involved in the process and determine the wavelengths carrying the major contribution. We found wavelengths ranging from 1400 to 1900 km, and generally decreasing toward the west. Where possible, we also computed a vertical location of the cloud pressure levels from the inversion of the spectral radiances measured by the JIRAM spectrometer. The waves were detected at pressure levels consistent with the NH3 as well as NH4SH clouds. Phase velocities could not be determined with sufficient confidence to discriminate whether the alternating crests and troughs are a propagating wave or a manifestation of a fluid dynamical instability. Title: A hexagon in Saturn's northern stratosphere surrounding the emerging summertime polar vortex Authors: Fletcher, L. N.; Orton, G. S.; Sinclair, J. A.; Guerlet, S.; Read, P. L.; Antuñano, A.; Achterberg, R. K.; Flasar, F. M.; Irwin, P. G. J.; Bjoraker, G. L.; Hurley, J.; Hesman, B. E.; Segura, M.; Gorius, N.; Mamoutkine, A.; Calcutt, S. B. Bibcode: 2018NatCo...9.3564F Altcode: 2018arXiv180900572F Saturn's polar stratosphere exhibits the seasonal growth and dissipation of broad, warm vortices poleward of 75° latitude, which are strongest in the summer and absent in winter. The longevity of the exploration of the Saturn system by Cassini allows the use of infrared spectroscopy to trace the formation of the North Polar Stratospheric Vortex (NPSV), a region of enhanced temperatures and elevated hydrocarbon abundances at millibar pressures. We constrain the timescales of stratospheric vortex formation and dissipation in both hemispheres. Although the NPSV formed during late northern spring, by the end of Cassini's reconnaissance (shortly after northern summer solstice), it still did not display the contrasts in temperature and composition that were evident at the south pole during southern summer. The newly formed NPSV was bounded by a strengthening stratospheric thermal gradient near 78°N. The emergent boundary was hexagonal, suggesting that the Rossby wave responsible for Saturn's long-lived polar hexagon—which was previously expected to be trapped in the troposphere—can influence the stratospheric temperatures some 300 km above Saturn's clouds. Title: Modeling of the Hydrogen Lyman Lines in Solar Flares Authors: Brown, Stephen A.; Fletcher, Lyndsay; Kerr, Graham S.; Labrosse, Nicolas; Kowalski, Adam F.; De La Cruz Rodríguez, Jaime Bibcode: 2018ApJ...862...59B Altcode: 2018arXiv180703373B The hydrogen Lyman lines (91.2 nm < λ < 121.6 nm) are significant contributors to the radiative losses of the solar chromosphere, and they are enhanced during flares. We have shown previously that the Lyman lines observed by the Extreme Ultraviolet Variability instrument onboard the Solar Dynamics Observatory exhibit Doppler motions equivalent to speeds on the order of 30 km s-1. However, contrary to expectations, both redshifts and blueshifts were present and no dominant flow direction was observed. To understand the formation of the Lyman lines, particularly their Doppler motions, we have used the radiative hydrodynamic code, RADYN, along with the radiative transfer code, RH, to simulate the evolution of the flaring chromosphere and the response of the Lyman lines during solar flares. We find that upflows in the simulated atmospheres lead to blueshifts in the line cores, which exhibit central reversals. We then model the effects of the instrument on the profiles, using the Extreme Ultraviolet Variability Experiment (EVE) instrument's properties. What may be interpreted as downflows (redshifted emission) in the lines, after they have been convolved with the instrumental line profile, may not necessarily correspond to actual downflows. Dynamic features in the atmosphere can introduce complex features in the line profiles that will not be detected by instruments with the spectral resolution of EVE, but which leave more of a signature at the resolution of the Spectral Investigation of the Coronal Environment instrument onboard the Solar Orbiter. Title: Observing turbulence early in a solar flare with the high time resolution of IRIS Authors: Jeffrey, Natasha; Simões, Paulo; Fletcher, Lyndsay; Labrosse, Nicolas Bibcode: 2018cosp...42E1609J Altcode: Wave and turbulent dissipation play a key role in the transfer of energy in magnetized plasmas. Here we report the first high time-resolution, <2 s, spectroscopic study of flare turbulence in the lower solar atmosphere, using the Interface Region Imaging Spectrograph (IRIS). We observe the line Si IV 1402.77 Å, formed at a transition region temperature of 80000 K, at the eastern flare footpoint, over a region of <0.3'' during the flare duration. The non-thermal broadening indicates turbulent motions with velocities of 60-70 km/s. The line broadening rises sharply, and precedes the flare onset as indicated by its impulsive radiation signatures in Si IV intensity, extreme ultraviolet (EUV) and X-rays. The <2 s cadence shows that the line broadening oscillates with a period of ∼10 s before its decay, coinciding with motions in the Si IV line centroid position. The results are consistent with the dissipation of turbulent energy in the lower atmosphere, early in the solar flare, and before the flare brightening. Title: Spectroscopic measurements of the ion velocity distribution at the base of the fast solar wind Authors: Jeffrey, Natasha; Savin, Daniel W.; Hahn, Michael; Fletcher, Lyndsay Bibcode: 2018cosp...42E1608J Altcode: In situ measurements of the fast solar wind reveal non-thermal distributions of electrons, protons and, minor ions extending from 0.3 AU to the heliopause. The physical mechanisms responsible for these non-thermal properties and the location where these properties originate remain open questions. Here we present spectroscopic evidence, from extreme ultraviolet spectroscopy, that the velocity distribution functions (VDFs) of minor ions are already non-Gaussian at the base of the fast solar wind in a coronal hole, at altitudes of < 1.1 R_{⊙}. Analysis of Fe, Si, and Mg spectral lines reveal a peaked line-shape core and broad wings that can be characteristed by a kappa VDF. A kappa distribution fit gives very small kappa indices off-limb of κ≈ 1.9-2.5, indicating either (a) ion populations far from thermal equilibrium, (b) fluid motions such as non-Gaussian turbulent fluctuations or non-uniform wave motions, or (c) some combination of both. These observations provide important empirical constraints for the source region of the fast solar wind and for the theoretical models of the different acceleration, heating, and energy deposition processes therein. To the best of our knowledge, this is the first time that the ion VDF in the fast solar wind has been probed so close to its source region. The findings are also a timely precursor to the upcoming 2018 launch of the Parker Solar Probe, which will provide the closest in situ measurements of the solar wind at approximately 0.04 AU (8.5 solar radii). Title: Thermal Emission From Saturn's Polar Cyclones Authors: Achterberg, R. K.; Flasar, F. M.; Bjoraker, G. L.; Hesman, B. E.; Gorius, N. J. P.; Mamoutkine, A. A.; Fletcher, L. N.; Segura, M. E.; Edgington, S. G.; Brooks, S. M. Bibcode: 2018GeoRL..45.5312A Altcode: We have used data from the Cassini Composite Infrared Spectrometer to map the temperatures in Saturn's polar cyclones at the highest spatial resolution obtained during the Cassini mission. We find temperature contrasts of 7 K in the upper troposphere within 1.4° of both poles, roughly 50 percent larger than earlier measurements at lower spatial resolution. The polar hot spots weaken with depth, disappearing near 500 mbar. In the stratosphere, the polar hot spot becomes broader, extending 4° from the poles, and weakens with altitude disappearing near 1 mbar. A thermal relaxation model shows that the tropospheric hot spot is consistent with adiabatic heating from subsidence with a vertical velocity of about -0.05 mm/s above 500 mbar. The observed temperature gradients imply that the winds in the polar cyclone decay with increasing altitude over roughly three pressure scale heights above the 200-mbar level. Title: Scientific rationale for Uranus and Neptune in situ explorations Authors: Mousis, O.; Atkinson, D. H.; Cavalié, T.; Fletcher, L. N.; Amato, M. J.; Aslam, S.; Ferri, F.; Renard, J. -B.; Spilker, T.; Venkatapathy, E.; Wurz, P.; Aplin, K.; Coustenis, A.; Deleuil, M.; Dobrijevic, M.; Fouchet, T.; Guillot, T.; Hartogh, P.; Hewagama, T.; Hofstadter, M. D.; Hue, V.; Hueso, R.; Lebreton, J. -P.; Lellouch, E.; Moses, J.; Orton, G. S.; Pearl, J. C.; Sánchez-Lavega, A.; Simon, A.; Venot, O.; Waite, J. H.; Achterberg, R. K.; Atreya, S.; Billebaud, F.; Blanc, M.; Borget, F.; Brugger, B.; Charnoz, S.; Chiavassa, T.; Cottini, V.; d'Hendecourt, L.; Danger, G.; Encrenaz, T.; Gorius, N. J. P.; Jorda, L.; Marty, B.; Moreno, R.; Morse, A.; Nixon, C.; Reh, K.; Ronnet, T.; Schmider, F. -X.; Sheridan, S.; Sotin, C.; Vernazza, P.; Villanueva, G. L. Bibcode: 2018P&SS..155...12M Altcode: 2017arXiv170800235M The ice giants Uranus and Neptune are the least understood class of planets in our solar system but the most frequently observed type of exoplanets. Presumed to have a small rocky core, a deep interior comprising ∼70% heavy elements surrounded by a more dilute outer envelope of H2 and He, Uranus and Neptune are fundamentally different from the better-explored gas giants Jupiter and Saturn. Because of the lack of dedicated exploration missions, our knowledge of the composition and atmospheric processes of these distant worlds is primarily derived from remote sensing from Earth-based observatories and space telescopes. As a result, Uranus's and Neptune's physical and atmospheric properties remain poorly constrained and their roles in the evolution of the Solar System not well understood. Exploration of an ice giant system is therefore a high-priority science objective as these systems (including the magnetosphere, satellites, rings, atmosphere, and interior) challenge our understanding of planetary formation and evolution. Here we describe the main scientific goals to be addressed by a future in situ exploration of an ice giant. An atmospheric entry probe targeting the 10-bar level, about 5 scale heights beneath the tropopause, would yield insight into two broad themes: i) the formation history of the ice giants and, in a broader extent, that of the Solar System, and ii) the processes at play in planetary atmospheres. The probe would descend under parachute to measure composition, structure, and dynamics, with data returned to Earth using a Carrier Relay Spacecraft as a relay station. In addition, possible mission concepts and partnerships are presented, and a strawman ice-giant probe payload is described. An ice-giant atmospheric probe could represent a significant ESA contribution to a future NASA ice-giant flagship mission. Title: The Origin of White Light Flares: A parameter study of standard model solar flare RHD Simulations Authors: Kerr, Graham Stewart; de Aguiar Simoes, Paulo Jose; Fletcher, Lyndsay; Allred, Joel C.; Kowalski, Adam F. Bibcode: 2018tess.conf30490K Altcode: The bulk of the enhanced radiation emitted during solar flares originates from the lower atmosphere, making it a crucial region for understanding energy and radiation transport during flares. Of the radiation emitted from the lower atmosphere a significant contribution is from enhancements to the optical continuum (white light flares; WLFs). There is still no consensus regarding the emission mechanism responsible for WLFs, in part due to the paucity of broadband WLF spectra, leading to ambiguity. Two commonly proposed mechanisms are optically thin recombination radiation in the chromosphere resulting from overionisation during the flare or optically thick radiation from the photosphere/upper photosphere resulting from enhanced H- opacity (an enhanced blackbody spectrum). Each mechanism can impose strong constraints on models of energy transport. Of course a combination of mechanisms is also possible. In the standard flare model, energy is transported to the chromosphere via a beam of non-thermal electrons. To address how WLFs would be produced in this standard model we performed a parameter study, simulating 43 flares using RADYN, a radiation hydrodynamics flare code. This study covered a range of typical non-thermal electron beam distributions and energy fluxes. It was found that in all cases the peak flare contribution to WLFs originated in the upper chromosphere as a result of recombinations. For harder non-thermal electron distributions there was also a non-negligible contribution of H- emission from the lower chromosphere and upper photosphere owing to an extended region of increased electron density (itself resulting from stronger, more deeply penetrating, non-thermal collisional ionisation rates). From this we predict that flares with a harder non-thermal electron distribution may exhibit a larger vertical extent when viewed on the limb. We were unable to simulate solely optically thick sources of WLFs. Our simulated WLF spectra are in good agreement with recent observations. Not all of our simulations resulted in an observable WLF. In lower energy simulations, flare energy input resulted in an enhanced opacity in the upper atmosphere but without sufficient ionization/recombination to produce a strong enough emissivity to counter the opacity. Thus we find that not all flares are white light flares. Title: Unambiguous Evidence of Coronal Implosions during Solar Eruptions and Flares Authors: Wang, Juntao; Simões, P. J. A.; Fletcher, L. Bibcode: 2018ApJ...859...25W Altcode: 2018arXiv180402354W In the implosion conjecture, coronal loops contract as the result of magnetic energy release in solar eruptions and flares. However, after almost two decades, observations of this phenomenon are still rare and most previous reports are plagued by projection effects so that loop contraction could be either true implosion or just a change in loop inclination. In this paper, to demonstrate the reality of loop contractions in the global coronal dynamics, we present four events with the continuously contracting loops in an almost edge-on geometry from the perspective of SDO/AIA, which are free from the ambiguity caused by the projection effects, also supplemented by contemporary observations from STEREO for examination. In the wider context of observations, simulations and theories, we argue that the implosion conjecture is valid in interpreting these events. Furthermore, distinct properties of the events allow us to identify two physical categories of implosion. One type demonstrates a rapid contraction at the beginning of the flare impulsive phase, as magnetic free energy is removed rapidly by a filament eruption. The other type, which has no visible eruption, shows a continuous loop shrinkage during the entire flare impulsive phase, which we suggest shows the ongoing conversion of magnetic free energy in a coronal volume. Corresponding scenarios are described that can provide reasonable explanations for the observations. We also point out that implosions may be suppressed in cases when a heavily mass-loaded filament is involved, possibly serving as an alternative account for their observational rarity. Title: Assessing the long-term variability of acetylene and ethane in the stratosphere of Jupiter Authors: Melin, Henrik; Fletcher, L. N.; Donnelly, P. T.; Greathouse, T. K.; Lacy, J. H.; Orton, G. S.; Giles, R. S.; Sinclair, J. A.; Irwin, P. G. J. Bibcode: 2018Icar..305..301M Altcode: 2018arXiv180100652M Acetylene (C2H2) and ethane (C2H6) are both produced in the stratosphere of Jupiter via photolysis of methane (CH4). Despite this common source, the latitudinal distribution of the two species is radically different, with acetylene decreasing in abundance towards the pole, and ethane increasing towards the pole. We present six years of NASA IRTF TEXES mid-infrared observations of the zonally-averaged emission of methane, acetylene and ethane. We confirm that the latitudinal distributions of ethane and acetylene are decoupled, and that this is a persistent feature over multiple years. The acetylene distribution falls off towards the pole, peaking at ∼ 30°N with a volume mixing ratio (VMR) of ∼ 0.8 parts per million (ppm) at 1 mbar and still falling off at ± 70° with a VMR of ∼ 0.3 ppm. The acetylene distributions are asymmetric on average, but as we move from 2013 to 2017, the zonally-averaged abundance becomes more symmetric about the equator. We suggest that both the short term changes in acetylene and its latitudinal asymmetry is driven by changes to the vertical stratospheric mixing, potentially related to propagating wave phenomena. Unlike acetylene, ethane has a symmetric distribution about the equator that increases toward the pole, with a peak mole fraction of ∼ 18 ppm at about ± 50° latitude, with a minimum at the equator of ∼ 10 ppm at 1 mbar. The ethane distribution does not appear to respond to mid-latitude stratospheric mixing in the same way as acetylene, potentially as a result of the vertical gradient of ethane being much shallower than that of acetylene. The equator-to-pole distributions of acetylene and ethane are consistent with acetylene having a shorter lifetime than ethane that is not sensitive to longer advective timescales, but is augmented by short-term dynamics, such as vertical mixing. Conversely, the long lifetime of ethane allows it to be transported to higher latitudes faster than it can be chemically depleted. Title: Spectroscopic Measurements of the Ion Velocity Distribution at the Base of the Fast Solar Wind Authors: Jeffrey, Natasha L. S.; Hahn, Michael; Savin, Daniel W.; Fletcher, Lyndsay Bibcode: 2018EGUGA..20.1620J Altcode: In situ measurements of the fast solar wind reveal non-thermal distributions of electrons, protons and, minor ions extending from 0.3 AU to the heliopause. The physical mechanisms responsible for these non-thermal properties and the location where these properties originate remain open questions. Here we present spectroscopic evidence, from extreme ultraviolet spectroscopy, that the velocity distribution functions (VDFs) of minor ions are already non-Gaussian at the base of the fast solar wind in a coronal hole, at altitudes of < 1.1R⊙. Analysis of Fe, Si, and Mg spectral lines reveal a peaked line-shape core and broad wings that can be characteristed by a kappa VDF. A kappa distribution fit gives very small kappa indices off-limb of κ ≈ 1.9 - 2.5, indicating either (a) ion populations far from thermal equilibrium, (b) fluid motions such as non-Gaussian turbulent fluctuations or non-uniform wave motions, or (c) some combination of both. These observations provide important empirical constraints for the source region of the fast solar wind and for the theoretical models of the different acceleration, heating, and energy deposition processes therein. To the best of our knowledge, this is the first time that the ion VDF in the fast solar wind has been probed so close to its source region. The findings are also a timely precursor to the upcoming 2018 launch of the Parker Solar Probe, which will provide the closest in situ measurements of the solar wind at approximately 0.04 AU (8.5 solar radii). Title: The quest for H_3^+ at Neptune: deep burn observations with NASA IRTF iSHELL Authors: Melin, H.; Fletcher, L. N.; Stallard, T. S.; Johnson, R. E.; O'Donoghue, J.; Moore, L.; Donnelly, P. T. Bibcode: 2018MNRAS.474.3714M Altcode: 2017arXiv171108978M Emission from the molecular ion H_3^+ is a powerful diagnostic of the upper atmosphere of Jupiter, Saturn, and Uranus, but it remains undetected at Neptune. In search of this emission, we present near-infrared spectral observations of Neptune between 3.93 and 4.00 μm taken with the newly commissioned iSHELL instrument on the NASA Infrared Telescope Facility in Hawaii, obtained 2017 August 17-20. We spent 15.4 h integrating across the disc of the planet, yet were unable to unambiguously identify any H_3^+ line emissions. Assuming a temperature of 550 K, we derive an upper limit on the column integrated density of 1.0^{+1.2}_{-0.8}× 10^{13} m-2, which is an improvement of 30 per cent on the best previous observational constraint. This result means that models are overestimating the density by at least a factor of 5, highlighting the need for renewed modelling efforts. A potential solution is strong vertical mixing of polyatomic neutral species from Neptune's upper stratosphere to the thermosphere, reacting with H_3^+, thus greatly reducing the column integrated H_3^+ densities. This upper limit also provide constraints on future attempts at detecting H_3^+ using the James Webb Space Telescope. Title: Spectroscopic Measurements of the Ion Velocity Distribution at the Base of the Fast Solar Wind Authors: Jeffrey, Natasha L. S.; Hahn, Michael; Savin, Daniel W.; Fletcher, Lyndsay Bibcode: 2018ApJ...855L..13J Altcode: 2018arXiv180207104J In situ measurements of the fast solar wind reveal non-thermal distributions of electrons, protons, and minor ions extending from 0.3 au to the heliopause. The physical mechanisms responsible for these non-thermal properties and the location where these properties originate remain open questions. Here, we present spectroscopic evidence, from extreme ultraviolet spectroscopy, that the velocity distribution functions (VDFs) of minor ions are already non-Gaussian at the base of the fast solar wind in a coronal hole, at altitudes of <1.1 R ⊙. Analysis of Fe, Si, and Mg spectral lines reveals a peaked line-shape core and broad wings that can be characterized by a kappa VDF. A kappa distribution fit gives very small kappa indices off-limb of κ ≈ 1.9-2.5, indicating either (a) ion populations far from thermal equilibrium, (b) fluid motions such as non-Gaussian turbulent fluctuations or non-uniform wave motions, or (c) some combination of both. These observations provide important empirical constraints for the source region of the fast solar wind and for the theoretical models of the different acceleration, heating, and energy deposition processes therein. To the best of our knowledge, this is the first time that the ion VDF in the fast solar wind has been probed so close to its source region. The findings are also a timely precursor to the upcoming 2018 launch of the Parker Solar Probe, which will provide the closest in situ measurements of the solar wind at approximately 0.04 au (8.5 solar radii). Title: Equatorial Oscillation and Planetary Wave Activity in Saturn's Stratosphere Through the Cassini Epoch Authors: Guerlet, S.; Fouchet, T.; Spiga, A.; Flasar, F. M.; Fletcher, L. N.; Hesman, B. E.; Gorius, N. Bibcode: 2018JGRE..123..246G Altcode: Thermal infrared spectra acquired by Cassini/Composite InfraRed Spectrometer (CIRS) in limb-viewing geometry in 2015 are used to derive 2-D latitude-pressure temperature and thermal wind maps. These maps are used to study the vertical structure and evolution of Saturn's equatorial oscillation (SEO), a dynamical phenomenon presenting similarities with the Earth's quasi-biennal oscillation (QBO) and semi-annual oscillation (SAO). We report that a new local wind maximum has appeared in 2015 in the upper stratosphere and derive the descent rates of other wind extrema through time. The phase of the oscillation observed in 2015, as compared to 2005 and 2010, remains consistent with a ∼15 year period. The SEO does not propagate downward at a regular rate but exhibits faster descent rate in the upper stratosphere, combined with a greater vertical wind shear, compared to the lower stratosphere. Within the framework of a QBO-type oscillation, we estimate the absorbed wave momentum flux in the stratosphere to be on the order of ∼7 × 10-6 N m-2. On Earth, interactions between vertically propagating waves (both planetary and mesoscale) and the mean zonal flow drive the QBO and SAO. To broaden our knowledge on waves potentially driving Saturn's equatorial oscillation, we searched for thermal signatures of planetary waves in the tropical stratosphere using CIRS nadir spectra. Temperature anomalies of amplitude 1-4 K and zonal wave numbers 1 to 9 are frequently observed, and an equatorial Rossby (n = 1) wave of zonal wave number 3 is tentatively identified in November 2009. Title: Jupiter's auroral-related stratospheric heating and chemistry II: Analysis of IRTF-TEXES spectra measured in December 2014 Authors: Sinclair, J. A.; Orton, G. S.; Greathouse, T. K.; Fletcher, L. N.; Moses, J. I.; Hue, V.; Irwin, P. G. J. Bibcode: 2018Icar..300..305S Altcode: We present a retrieval analysis of TEXES (Texas Echelon Cross Echelle Spectrograph (Lacy et al., 2002)) spectra of Jupiter's high latitudes obtained on NASA's Infrared Telescope Facility on December 10 and 11th 2014. The vertical temperature profile and vertical profiles of C2H2, C2H4 and C2H6 were retrieved at both high-northern and high-southern latitudes and results were compared in 'quiescent' regions and regions known to be affected by Jupiter's aurora in order to highlight how auroral processes modify the thermal structure and hydrocarbon chemistry of the stratosphere. In qualitative agreement with Sinclair et al. (2017a), we find temperatures in auroral regions to be elevated with respect to quiescent regions at two discrete pressures levels at approximately 1 mbar and 0.01 mbar. For example, in comparing retrieved temperatures at 70°N, 60°W (a representative quiescent region) and 70°N, 180°W (centred on the northern auroral oval), temperatures increase by 19.0 ± 4.2 K at 0.98 mbar, 20.8 ± 3.9 K at 0.01 mbar but only by 8.3 ± 4.9 K at the intermediate level of 0.1 mbar. We conclude that elevated temperatures at 0.01 mbar result from heating by joule resistance of the atmosphere and the energy imparted by electron and ion precipitation. However, temperatures at 1 mbar are considered to result either from heating by shortwave radiation of aurorally-produced haze particulates or precipitation of higher energy population of charged particles. Our former conclusion would be consistent with results of auroral-chemistry models, that predict the highest number densities of aurorally-produced haze particles at this pressure level (Wong et al., 2000, 2003). C2H2 and C2H4 exhibit enrichments but C2H6 remains constant within uncertainty when comparing retrieved concentrations in the northern auroral region with quiescent longitudes in the same latitude band. At 1 mbar, C2H2 increases from 278.4 ± 40.3 ppbv at 70°N, 60°W to 564.4 ± 72.0 ppbv at 70°N, 180°W and at 0.01 mbar, over the same longitude range at 70°N, C2H4 increases from 0.669 ± 0.129 ppmv to 6.509 ± 0.811 ppmv. However, we note that non-LTE (local thermodynamic equilibrium) emission may affect the cores of the strongest C2H2 and C2H4 lines on the northern auroral region, which may be a possible source of error in our derived concentrations. We retrieved concentrations of C2H6 at 1 mbar of 9.03 ± 0.98 ppmv at 70°N, 60°W and 7.66 ± 0.70 ppmv at 70°N, 180°W. Thus, C2H6's concentration appears constant (within uncertainty) as a function of longitude at 70°N. Title: Detection of 3-Minute Oscillations in Full-Disk Lyman-alpha Emission During A Solar Flare Authors: Milligan, R. O.; Ireland, J.; Fleck, B.; Hudson, H. S.; Fletcher, L.; Dennis, B. R. Bibcode: 2017AGUFMSH41A2739M Altcode: We report the detection of chromospheric 3-minute oscillations in disk-integrated EUV irradiance observations during a solar flare. A wavelet analysis of detrended Lyman-alpha (from GOES/EUVS) and Lyman continuum (from SDO/EVE) emission from the 2011 February 15 X-class flare revealed a 3-minute period present during the flare's main phase. The formation temperature of this emission locates this radiation to the flare's chromospheric footpoints, and similar behaviour is found in the SDO/AIA 1600A and 1700A channels, which are dominated by chromospheric continuum. The implication is that the chromosphere responds dynamically at its acoustic cutoff frequency to an impulsive injection of energy. Since the 3-minute period was not found at hard X-ray energies (50-100 keV) in RHESSI data we can state that this 3-minute oscillation does not depend on the rate of energization of, or energy deposition by, non-thermal electrons. However, a second period of 120 s found in both hard X-ray and chromospheric emission is consistent with episodic electron energization on 2-minute timescales. Our finding on the 3-minute oscillation suggests that chromospheric mechanical energy should be included in the flare energy budget, and the fluctuations in the Lyman-alpha line may influence the composition and dynamics of planetary atmospheres during periods of high activity. Title: Hα and Hβ emission in a C3.3 solar flare: comparison between observations and simulations Authors: Zuccarello, F.; Simoes, P. J. D. A.; Capparelli, V.; Fletcher, L.; Romano, P.; Mathioudakis, M.; Cauzzi, G.; Carlsson, M.; Kuridze, D.; Keys, P. Bibcode: 2017AGUFMSH41A2742Z Altcode: This work is based on the analysis of an extremely rare set of simultaneous observations of a C3.3 solar flare in the Hα and Hβ lines at high spatial and temporal resolution, which were acquired at the Dunn Solar Telescope. Images of the C3.3 flare (SOL2014-04-22T15:22) made at various wavelengths along the Hα line profile by the Interferometric Bidimensional Spectrometer (IBIS) and in the Hβ with the Rapid Oscillations in the Solar Atmosphere (ROSA) broadband imager are analyzed to obtain the intensity evolution. The analysis shows that Hα and Hβ intensity excesses in three identified flare footpoints are well correlated in time. In the stronger footpoints, the typical value of the the Hα/Hβ intensity ratio observed is ∼ 0.4 - 0.5, in broad agreement with values obtained from a RADYN non-LTE simulation driven by an electron beam with parameters constrained by observations. The weaker footpoint has a larger Hα/Hβ ratio, again consistent with a RADYN simulation but with a smaller energy flux. Title: Dynamical and Chemical Tracers in Jupiter's Troposphere and Stratosphere from the Earth-Based Infrared Juno Support Campaign Authors: Melin, H.; Fletcher, L. N.; Donnelly, P. T.; Greathouse, T.; Lacy, J.; Orton, G.; Giles, R.; Sinclair, J. A.; Irwin, P. G. Bibcode: 2017AGUFM.P31C2841M Altcode: The three-dimensional distribution of temperatures, chemical tracers and aerosol opacity in Jupiter's troposphere and stratosphere can be characterised by inverting spectra and images taken the mid-infrared. We present NASA IRTF TEXES, Gemini TEXES and VLT VISIR 5-25 µm spectral maps of Jupiter obtained in the run-up, and during the Juno mission at Jupiter, providing crucial observations in the mid-infrared, a wavelength region not covered by Juno's suite of instruments. The NASA IRTF TEXES observations form a long baseline of spectroscopic maps between 2012 and 2017, providing temporal context for Juno's observations. Using this dataset we investigate the zonal abundance distribution of acetylene and ethane, and how these change over time. Using the methane channel, we can retrieve the vertical temperature profile between 1 and 10 mbar and track a full cycle of Jupiter's equatorial stratospheric oscillation. We confirm that the acetylene abundance decreases towards the pole, whilst ethane increases towards the pole. We find that the data supports the hypothesis that acetylene is asymmetric about the equator, and varies with time in response to short-lived dynamical changes. We suggest that this asymmetry, which changes over time, is driven by stratospheric wave activity. Conversely, ethane appears to be symmetric about the equator, and does not vary with time. The stark difference between acetylene and ethane is likely linked to the two species having very different chemical life-times and vertical abundance gradients. Gemini TEXES spectral mapping in March 2017 reveals - in addition to temperatures - the spatial distribution of ammonia, phosphine and upper tropospheric aerosols at high spatial resolution. We confirm the equatorial NH3 enhancement observed by Juno, and investigate the distribution of these dynamical tracers in the vicinity of NEB hotspots, an SEB plume outbreak, and the Great Red Spot. Title: Ammonia in Jupiter's troposphere: a comparison of ground-based 5-μm high-resolution spectroscopy and Juno MWR observations Authors: Giles, R.; Orton, G.; Fletcher, L. N.; Irwin, P. G.; Sinclair, J. A. Bibcode: 2017AGUFM.P31C2812G Altcode: Latitudinally-resolved 5-micron observations of Jupiter from the CRIRES instrument at the Very Large Telescope are used to measure the spatial variability in Jupiter's tropospheric ammonia (NH3) abundance and these results are compared to the results from Juno's Microwave Radiometer (MWR). The 5-micron spectral region is an atmospheric window, allowing us to probe down to Jupiter's middle troposphere. The high-resolution 2012 CRIRES observations include several spectrally-resolved NH3 absorption features; these features probe slightly different pressure levels, allowing the NH3 vertical profile at 1-4 bar to be constrained. We find that in regions of low cloud opacity, the NH3 abundance must decrease with altitude within this pressure range. The CRIRES observations do not provide evidence for any significant belt-zone variability in NH3, as any difference in the spectral shape can be accounted for by the large differences in cloud opacity between the cloudy zones and the cloud-free belts. However, we do find evidence for a strong localised enhancement in NH3 on the southern edge of the North Equatorial Belt (4-6°N). These results can be directly compared with observations from the Juno mission's MWR experiment. Li et al. (2017, doi 10.1002/2017GL073159) have used MWR data to retrieve NH3 abundances at pressure levels of 1-100 bar. In bright, cloud-free regions of the planet, the two datasets are broadly consistent, including the asymmetrical enhancement on the southern edge of the NEB. However, in the cool, cloudy Equatorial Zone, the MWR retrieved abundances are significantly higher than those from CRIRES and forward modeling shows that the MWR vertical distributions are unable to fit the CRIRES data. We will investigate possible explanations for this discrepancy, including the role of tropospheric clouds and temperature variations. Title: Non-thermal Power-Law Distributions in Solar and Space Plasmas Authors: Oka, M.; Battaglia, M.; Birn, J.; Chaston, C. C.; Effenberger, F.; Eriksson, E.; Fletcher, L.; Hatch, S.; Imada, S.; Khotyaintsev, Y. V.; Kuhar, M.; Livadiotis, G.; Miyoshi, Y.; Retino, A. Bibcode: 2017AGUFMSH51C2518O Altcode: Particles are accelerated to very high, non-thermal energies in solar and space plasma environments. While energy spectra of accelerated particles often exhibit a power-law and are characterized by the power-law index δ, it remains unclear how particles are accelerated to high energies and how δ is determined. Here, we review previous observations of the power-law index δ in a variety of different plasma environments with a particular focus on sub-relativistic electrons. It appears that in regions more closely related to magnetic reconnection (such as the "above-the-looptop" solar hard X-ray source and the plasma sheet in Earth's magnetotail), the spectra are typically soft (δ> 4). This is in contrast to the typically hard spectra (δ< 4) that are observed in coincidence with shocks. The difference implies that shocks are more efficient in producing a larger fraction of non-thermal electron energies than magnetic reconnection. A caveat is that during active times in Earth's magnetotail, δ values seem spatially uniform in the plasma sheet, while power-law distributions still exist even in quiet times. The role of magnetotail reconnection in the electron power-law formation could therefore be confounded with these background conditions. Because different regions have been studied with different instrumentations and methodologies, we point out a need for more systematic and coordinated studies of power-law distributions for a better understanding of possible scaling laws in particle acceleration as well as their universality. Title: High spatial and spectral resolution measurements of Jupiter's auroral regions using Gemini-North-TEXES Authors: Sinclair, J. A.; Orton, G. S.; Greathouse, T. K.; Lacy, J.; Giles, R.; Fletcher, L. N.; Vogt, M.; Irwin, P. G. Bibcode: 2017AGUFM.P24A..08S Altcode: Jupiter exhibits auroral emission at a multitude of wavelengths. Auroral emission at X-ray, ultraviolet and near-infrared wavelengths demonstrate the precipitation of ion and electrons in Jupiter's upper atmosphere, at altitudes exceeding 250 km above the 1-bar level. Enhanced mid-infrared emission of CH4, C2H2, C2H4 and further hydrocarbons is also observed coincident with Jupiter's auroral regions. Retrieval analyses of infrared spectra from IRTF-TEXES (Texas Echelon Cross Echelle Spectrograph on NASA's Infrared Telescope Facility) indicate strong heating at the 1-mbar level and evidence of ion-neutral chemistry, which enriches the abundances of unsaturated hydrocarbons (Sinclair et al., 2017b, doi:10.1002/2017GL073529, Sinclair et al., 2017c (under review)). The extent to which these phenomena in the stratosphere are correlated and coupled physically with the shorter-wavelength auroral emission originating from higher altitudes has been a challenge due to the limited spatial resolution available on the IRTF. Smaller-scale features observed in the near-infrared and ultraviolet emission, such as the main `oval', transient `swirls' and dusk-active regions within the main oval (e.g. Stallard et al., 2014, doi:10.1016/j/Icarus.2015.12.044, Nichols et al., 2017, doi: 10.1002/2017GL073029) are potentially being blurred in the mid-infrared by the diffraction-limited resolution (0.7") of IRTF's 3-metre primary aperture. However, on March 17-19th 2017, we obtained spectral measurements of H2 S(1), CH4, C2H2, C2H4 and C2H6 emission of Jupiter's high latitudes using TEXES on Gemini-North, which has a 8-metre primary aperture. This rare opportunity combines the superior spectral resolving power of TEXES and the high spatial resolution provided by Gemini-North's 8-metre aperture. We will perform a retrieval analyses to determine the 3D distributions of temperature, C2H2, C2H4 and C2H6. The morphology will be compared with near-contemporaneous measurements of H3+ emission from IRTF-SpeX and Juno-JIRAM/UVS to assess the extent of coupling between the stratosphere and ionosphere. In addition, a magnetospheric mapping tool (Vogt et al. 2011, doi:10.1029/2010JA016148) will be used to determine whether small-scale features are likely linked to the solar wind or the magnetosphere. Title: Characterization of Jupiter's Atmosphere from Observation of Thermal Emission by Juno and Ground-Based Supporting Observations Authors: Orton, G. S.; Momary, T.; Tabataba-Vakili, F.; Janssen, M. A.; Hansen, C. J.; Bolton, S. J.; Li, C.; Adriani, A.; Mura, A.; Grassi, D.; Fletcher, L. N.; Brown, S. T.; Fujiyoshi, T.; Greathouse, T. K.; Kasaba, Y.; Sato, T. M.; Stephens, A.; Donnelly, P.; Eichstädt, G.; Rogers, J. Bibcode: 2017AGUFM.P23E..02O Altcode: Ground-breaking measurements of thermal emission at very long wavelengths have been made by the Juno mission's Microwave Radiometer (MWR). We examine the relationship between these and other thermal emission measurements by the Jupiter Infrared Auroral Mapper (JIRAM) at 5 µm and ground-based supporting observations in the thermal infrared that cover the 5-25 µm range. The relevant ground-based observations of thermal emission are constituted from imaging and scanning spectroscopy obtained at the NASA Infrared Telescope Facility (IRTF), the Gemini North Telescope, the Subaru Telescope and the Very Large Telescope. A comparison of these results clarifies the physical properties responsible for the observed emissions, i.e. variability of the temperature field, the cloud field or the distribution of gaseous ammonia. Cross-references to the visible cloud field from Juno's JunoCam experiment and Earth-based images are also useful. This work continues an initial comparison by Orton et al. (2017, GRL 44, doi: 10.1002/2017GL073019) between MWR and JIRAM results, together with ancillary 5-µm IRTF imaging and with JunoCam and ground-based visible imaging. These showed a general agreement between MWR and JIRAM results for the 5-bar NH3 abundance in specific regions of low cloud opacity but only a partial correlation between MWR and 5-µm radiances emerging from the 0.5-5 bar levels of the atmosphere in general. Similar to the latter, there appears to be an inconsistent correlation between MWR channels sensitive to 0.5-10 bars and shorter-wavelength radiances in the "tails" of 5-µm hot spots , which may be the result of the greater sensitivity of the latter to particulate opacity that could depend on the evolution history of the particular features sampled. Of great importance is the interpretation of MWR radiances in terms of the variability of temperature vs. NH3 abundances in the 0.5-5 bar pressure range. This is particularly important to understand MWR results in Jupiter's Great Red Spot. It may also be important to understand apparent differences between MWR and high-resolution spectroscopic observations around Jupiter's equator. Title: D/H Ratios on Saturn and Jupiter from Cassini CIRS Authors: Pierel, J. D. R.; Nixon, C. A.; Lellouch, E.; Fletcher, L. N.; Bjoraker, G. L.; Achterberg, R. K.; Bézard, B.; Hesman, B. E.; Irwin, P. G. J.; Flasar, F. M. Bibcode: 2017AJ....154..178P Altcode: We present new measurements of the deuterium abundance on Jupiter and Saturn, showing evidence that Saturn's atmosphere contains less deuterium than Jupiter's. We analyzed far-infrared spectra from the Cassini Composite Infrared Spectrometer to measure the abundance of HD on both giant planets. Our estimate of the Jovian D/H = (2.95 ± 0.55) × 10-5 is in agreement with previous measurements by ISO/SWS: (2.25 ± 0.35) × 10-5, and the Galileo probe: (2.6 ± 0.7) × 10-5. In contrast, our estimate of the Saturn value of (2.10 ± 0.13) × 10-5 is somewhat lower than on Jupiter (by a factor of 0.71-0.15+0.22), contrary to model predictions of a higher ratio: Saturn/Jupiter = 1.05-1.20. The Saturn D/H value is consistent with estimates for hydrogen in the protosolar nebula (2.1 ± 0.5) × 10-5, but its apparent divergence from the Jovian value suggests that our understanding of planetary formation and evolution is incomplete, which is in agreement with previous work. Title: Hα and Hβ Emission in a C3.3 Solar Flare: Comparison between Observations and Simulations Authors: Capparelli, Vincenzo; Zuccarello, Francesca; Romano, Paolo; Simões, Paulo J. A.; Fletcher, Lyndsay; Kuridze, David; Mathioudakis, Mihalis; Keys, Peter H.; Cauzzi, Gianna; Carlsson, Mats Bibcode: 2017ApJ...850...36C Altcode: 2017arXiv171004067C The hydrogen Balmer series is a basic radiative loss channel from the flaring solar chromosphere. We report here on the analysis of an extremely rare set of simultaneous observations of a solar flare in the {{H}}α and {{H}}β lines, at high spatial and temporal resolutions, that were acquired at the Dunn Solar Telescope. Images of the C3.3 flare (SOL2014-04-22T15:22) made at various wavelengths along the {{H}}α line profile by the Interferometric Bidimensional Spectrometer (IBIS) and in the {{H}}β with the Rapid Oscillations in the Solar Atmosphere (ROSA) broadband imager are analyzed to obtain the intensity evolution. The {{H}}α and {{H}}β intensity excesses in three identified flare footpoints are well-correlated in time. We examine the ratio of {{H}}α to {{H}}β flare excess, which was proposed by previous authors as a possible diagnostic of the level of electron-beam energy input. In the stronger footpoints, the typical value of the the {{H}}α /H β intensity ratio observed is ∼0.4-0.5, in broad agreement with values obtained from a RADYN non-LTE simulation driven by an electron beam with parameters constrained (as far as possible) by observation. The weaker footpoint has a larger {{H}}α /H β ratio, again consistent with a RADYN simulation, but with a smaller energy flux. The {{H}}α line profiles observed have a less prominent central reversal than is predicted by the RADYN results, but can be brought into agreement if the {{H}}α -emitting material has a filling factor of around 0.2-0.3. Title: Can Substorm Particle Acceleration Be Applied to Solar Flares? Authors: Birn, J.; Battaglia, M.; Fletcher, L.; Hesse, M.; Neukirch, T. Bibcode: 2017ApJ...848..116B Altcode: Using test particle studies in the electromagnetic fields of three-dimensional magnetohydrodynamic (MHD) simulations of magnetic reconnection, we study the energization of charged particles in the context of the standard two-ribbon flare picture in analogy to the standard magnetospheric substorm paradigm. In particular, we investigate the effects of the collapsing field (“collapsing magnetic trap”) below a reconnection site, which has been demonstrated to be the major acceleration mechanism that causes energetic particle acceleration and injections observed in Earth’s magnetotail associated with substorms and other impulsive events. We contrast an initially force-free, high-shear field (low beta) with low and moderate shear, finite-pressure (high-beta) arcade structures, where beta represents the ratio between gas (plasma) and magnetic pressure. We demonstrate that the energization affects large numbers of particles, but the acceleration is modest in the presence of a significant shear field. Without incorporating loss mechanisms, the effect on particles at different energies is similar, akin to adiabatic heating, and thus is not a likely mechanism to generate a power-law tail onto a (heated or not heated) Maxwellian velocity distribution. Title: Comparing UV/EUV line parameters and magnetic field in a quiescent prominence with tornadoes Authors: Levens, P. J.; Labrosse, N.; Schmieder, B.; López Ariste, A.; Fletcher, L. Bibcode: 2017A&A...607A..16L Altcode: 2017arXiv170804606L Context. Understanding the relationship between plasma and the magnetic field is important for describing and explaining the observed dynamics of solar prominences.
Aims: We determine if a close relationship can be found between plasma and magnetic field parameters, measured at high resolution in a well-observed prominence.
Methods: A prominence observed on 15 July 2014 by the Interface Region Imaging Spectrograph (IRIS), Hinode, the Solar Dynamics Observatory (SDO), and the Télescope Héliographique pour l'Étude du Magnétisme et des Instabilités Solaires (THEMIS) is selected. We perform a robust co-alignment of data sets using a 2D cross-correlation technique. Magnetic field parameters are derived from spectropolarimetric measurements of the He I D3 line from THEMIS. Line ratios and line-of-sight velocities from the Mg II h and k lines observed by IRIS are compared with magnetic field strength, inclination, and azimuth. Electron densities are calculated using Fe xii line ratios from the Hinode Extreme-ultraviolet Imaging Spectrometer, which are compared to THEMIS and IRIS data.
Results: We find Mg II k/h ratios of around 1.4 everywhere, similar to values found previously in prominences. Also, the magnetic field is strongest ( 30 G) and predominantly horizontal in the tornado-like legs of the prominence. The k3 Doppler shift is found to be between ±10 km s-1 everywhere. Electron densities at a temperature of 1.5 × 106 K are found to be around 109 cm-3. No significant correlations are found between the magnetic field parameters and any of the other plasma parameters inferred from spectroscopy, which may be explained by the large differences in the temperatures of the lines used in this study.
Conclusions: This is the first time that a detailed statistical study of plasma and magnetic field parameters has been performed at high spatial resolution in a prominence. Our results provide important constraints on future models of the plasma and magnetic field in these structures. Title: Detection of Three-minute Oscillations in Full-disk Lyα Emission during a Solar Flare Authors: Milligan, Ryan O.; Fleck, Bernhard; Ireland, Jack; Fletcher, Lyndsay; Dennis, Brian R. Bibcode: 2017ApJ...848L...8M Altcode: 2017arXiv170909037M In this Letter we report the detection of chromospheric 3-minute oscillations in disk-integrated EUV irradiance observations during a solar flare. A wavelet analysis of detrended Lyα (from GOES/EUVS) and Lyman continuum (from Solar Dynamics Observatory (SDO)/EVE) emission from the 2011 February 15 X-class flare (SOL2011-02-15T01:56) revealed a ∼3 minute period present during the flare’s main phase. The formation temperature of this emission locates this radiation at the flare’s chromospheric footpoints, and similar behavior is found in the SDO/Atmospheric Imaging Assembly 1600 and 1700 Å channels, which are dominated by chromospheric continuum. The implication is that the chromosphere responds dynamically at its acoustic cutoff frequency to an impulsive injection of energy. Since the 3-minute period was not found at hard X-ray (HXR) energies (50-100 keV) in Reuven Ramaty High Energy Solar Spectroscopic Imager data we can state that this 3-minute oscillation does not depend on the rate of energization of non-thermal electrons. However, a second period of 120 s found in both HXR and chromospheric lightcurves is consistent with episodic electron energization on 2-minute timescales. Our finding on the 3-minute oscillation suggests that chromospheric mechanical energy should be included in the flare energy budget, and the fluctuations in the Lyα line may influence the composition and dynamics of planetary atmospheres during periods of high activity. Title: Water and Volatiles in the Outer Solar System Authors: Grasset, O.; Castillo-Rogez, J.; Guillot, T.; Fletcher, L. N.; Tosi, F. Bibcode: 2017SSRv..212..835G Altcode: 2017SSRv..tmp..135G Space exploration and ground-based observations have provided outstanding evidence of the diversity and the complexity of the outer solar system. This work presents our current understanding of the nature and distribution of water and water-rich materials from the water snow line to the Kuiper Belt. This synthesis is timely, since a thorough exploration of at least one object in each region of the outer solar system has now been achieved. Next steps, starting with the Juno mission now in orbit around Jupiter, will be more focused on understanding the processes at work than on describing the general characteristics of each giant planet systems.

This review is organized in three parts. First, the nature and the distribution of water and volatiles in giant and intermediary planets are described from their inner core to their outer envelopes. A special focus is given to Jupiter and Saturn, which are much better understood than the two ice giants (Uranus and Neptune) thanks to the Galileo and Cassini missions. Second, the icy moons will be discussed. Space missions and ground-based observations have revealed the variety of icy surfaces in the outer system. While Europa, Enceladus, and maybe Titan present past or even active tectonic and volcanic activities, many other moons have been dead worlds for more than 3 billion years. Ice compositions found at these bodies are also complex and it is now commonly admitted that icy surfaces are never composed of pure ices. A detailed review of the distribution of non-ice materials on the surfaces and in the tenuous atmospheres of the moons is proposed, followed by a more focused discussion on the nature and the characteristics of the liquid layers trapped below the cold icy crusts that have been suggested in the icy Galilean moons, and in Enceladus, Dione, and Titan at Saturn. Finally, the recent observations collected by Dawn at Ceres and New Horizons at Pluto, as well as the state of knowledge of other transneptunian objects, are summarized, and complete this overview of the nature and distribution of ice-rich material in the outer solar system. Title: Seismology of contracting and expanding coronal loops using damping of kink oscillations by mode coupling Authors: Pascoe, D. J.; Russell, A. J. B.; Anfinogentov, S. A.; Simões, P. J. A.; Goddard, C. R.; Nakariakov, V. M.; Fletcher, L. Bibcode: 2017A&A...607A...8P Altcode:
Aims: We extend recently developed seismological methods to analyse oscillating loops which feature a large initial shift in the equilibrium position and investigate additional observational signatures related to the loop environment and oscillation driver.
Methods: We model the motion of coronal loops as a kink oscillation damped by mode coupling, accounting for any change in loop length and the possible presence of parallel harmonics in addition to the fundamental mode. We apply our model to a loop which rapidly contracts due to a post-flare implosion (SOL2012-03-09) and a loop with a large lateral displacement (SOL2012-10-20).
Results: The seismological method is used to calculate plasma parameters of the oscillating loops including the transverse density profile, magnetic field strength, and phase mixing timescale. For SOL2012-03-09 the period of oscillation has a linear correlation with the contracting motion and suggests the kink speed remains constant during the oscillation. The implosion excitation mechanism is found to be associated with an absence of additional parallel harmonics.
Conclusions: The improved Bayesian analysis of the coronal loop motion allows for accurate seismology of plasma parameters, and the evolution of the period of oscillation compared with the background trend can be used to distinguish between loop motions in the plane of the loop and those perpendicular to it. The seismologically inferred kink speed and density contrast imply sub-Alfvénic (MA = 0.16 ± 0.03) propagation of the magnetic reconfiguration associated with the implosion, as opposed to triggering by a wave propagating at the Alfvén speed. Title: Observations of Reconnection Flows in a Flare on the Solar Disk Authors: Wang, Juntao; Simões, P. J. A.; Jeffrey, N. L. S.; Fletcher, L.; Wright, P. J.; Hannah, I. G. Bibcode: 2017ApJ...847L...1W Altcode: 2017arXiv170808706W Magnetic reconnection is a well-accepted part of the theory of solar eruptive events, though the evidence is still circumstantial. Intrinsic to the reconnection picture of a solar eruptive event, particularly in the standard model for two-ribbon flares (CSHKP model), are an advective flow of magnetized plasma into the reconnection region, expansion of field above the reconnection region as a flux rope erupts, retraction of heated post-reconnection loops, and downflows of cooling plasma along those loops. We report on a unique set of Solar Dynamics Observatory/Atmospheric Imaging Assembly imaging and Hinode/EUV Imaging Spectrometer spectroscopic observations of the disk flare SOL2016-03-23T03:54 in which all four flows are present simultaneously. This includes spectroscopic evidence for a plasma upflow in association with large-scale expanding closed inflow field. The reconnection inflows are symmetric, and consistent with fast reconnection, and the post-reconnection loops show a clear cooling and deceleration as they retract. Observations of coronal reconnection flows are still rare, and most events are observed at the solar limb, obscured by complex foregrounds, making their relationship to the flare ribbons, cusp field, and arcades formed in the lower atmosphere difficult to interpret. The disk location and favorable perspective of this event have removed these ambiguities giving a clear picture of the reconnection dynamics. Title: Identifying the source of colour and featural changes in Jupiter's atmosphere from MUSE/VLT Authors: Braude, A. S.; Irwin, P. G. J.; Orton, G. S.; Fletcher, L. N. Bibcode: 2017EPSC...11..806B Altcode: We use ground-based observations from the MUSE/VLT instrument to characterise changes in cloud structure and colour in Jupiter's atmosphere between 2014-2017, and providing global context to observations of Jupiter from the Juno spacecraft. We witness significant changes in Jupiter's banded structure in the northern hemisphere in 2017, and we also confirm that the colour in Jupiter's red regions can be well-modelled using a red substance produced through the photochemical reaction of ammonia with acetylene. This implies a high-altitude source of colour in Jupiter's atmosphere. Title: Exploration of Jupiter's atmosphere and magnetosphere with the European Jupiter Icy Moons Explorer (JUICE) Authors: Cavalié, T.; Fletcher, L.; Krupp, N.; Masters, A.; Witasse, O. Bibcode: 2017EPSC...11..420C Altcode: JUICE - JUpiter ICy moons Explorer - is the first large mission in ESA's Cosmic Vision 2015-2025 programme. The mission was selected in May 2012 and adopted in November 2014. The implementation phase started in July 2015. Planned for launch in June 2022 and arrival at Jupiter in October 2029, it will spend at least three years making detailed observations of Jupiter and three of its largest moons, Ganymede, Callisto and Europa. JUICE will then orbit Ganymede for almost a year. JUICE will perform a varied and extensive orbital tour with access to high latitudes to provide a comprehensive study of the unique environmental conditions at Jupiter's poles. The overarching theme for JUICE is: The emergence of habitable worlds around gas giants. JUICE will also perform a multidisciplinary investigation of the Jupiter as an archetype for gas giants. In this paper, we will present the science objectives and key measurements performed by the instrument suite, relevant to the study of the atmosphere and magnetosphere of Jupiter. We will also present the first steps of the science implementation, as performed by the ESA Working Groups and Science Working Team. Title: Detection of Compact Baroclinic Waves in Jupiter's Deep Clouds at 5-microns from the VLT Authors: Fletcher, L. N.; Donnelly, P.; Melin, H.; Orton, G. S.; Greathouse, T. K.; Sinclair, J. A.; Giles, R. S.; Simon, A. A.; de Pater, I.; Wong, M. Bibcode: 2017EPSC...11..454F Altcode: A campaign of Earth-based supporting observations is providing spatial, temporal and spectral context to the close-in orbital exploration of Jupiter by the Juno mission. This campaign, utilising 8-m observatories on Earth, is providing some of the highest resolution mid-infrared observations of Jupiter ever obtained, allowing us to probe the scale of compact wave patterns for the first time. We report the detection of a compact (1-degree longitude) wave in the deep clouds of the North Equatorial Belt at 5-microns, coincident with a structure observed by Hubble in reflected sunlight at higher altitudes. Title: The Hera Saturn Entry Probe Mission: a Proposal in Response to the ESA M5 Call Authors: Mousis, O.; Atkinson, D.; Amato, M.; Aslam, S.; Atreya, S.; Blanc, M.; Bolton, S.; Brugger, B.; Calcutt, S.; Cavalié, T.; Charnoz, S.; Coustenis, A.; Deleuil, M.; Dobrijevic, M.; Ferri, F.; Fletcher, L.; Gautier, D.; Guillot, T.; Hartogh, P.; Holland, A. Bibcode: 2017EPSC...11..305M Altcode: The Hera Saturn entry probe mission is proposed as an ESA M-class mission to be piggybacked on a NASA spacecraft sent to or past the Saturn system. Hera consists of an atmospheric probe built by ESA and released into the atmosphere of Saturn by its NASA companion Saturn Carrier-Relay spacecraft. Hera will perform in situ measurements of the chemical and isotopic composition as well as the structure and dynamics of Saturn's atmosphere using a single probe, with the goal of improving our understanding of the origin, formation, and evolution of Saturn, the giant planets and their satellite systems, with extrapolation to extrasolar planets. Hera will probe well into and possibly beneath the cloud-forming region of the troposphere, below the region accessible to remote sensing, to locations where certain cosmogenically abundant species are expected to be well mixed. Title: Formation of the thermal infrared continuum in solar flares Authors: Simões, Paulo J. A.; Kerr, Graham S.; Fletcher, Lyndsay; Hudson, Hugh S.; Giménez de Castro, C. Guillermo; Penn, Matt Bibcode: 2017A&A...605A.125S Altcode: 2017arXiv170609867S
Aims: Observations of the Sun with the Atacama Large Millimeter Array have now started, and the thermal infrared will regularly be accessible from the NSF's Daniel K. Inouye Solar Telescope. Motivated by the prospect of these new data, and by recent flare observations in the mid infrared, we set out here to model and understand the source of the infrared continuum in flares, and to explore its diagnostic capability for the physical conditions in the flare atmosphere.
Methods: We use the one-dimensional (1D) radiation hydrodynamics code RADYN to calculate mid-infrared continuum emission from model atmospheres undergoing sudden deposition of energy by non-thermal electrons.
Results: We identify and characterise the main continuum thermal emission processes relevant to flare intensity enhancement in the mid- to far-infrared (2-200 μm) spectral range as free-free emission on neutrals and ions. We find that the infrared intensity evolution tracks the energy input to within a second, albeit with a lingering intensity enhancement, and provides a very direct indication of the evolution of the atmospheric ionisation. The prediction of highly impulsive emission means that, on these timescales, the atmospheric hydrodynamics need not be considered in analysing the mid-IR signatures. Title: Characterising Jupiter's Temperatures, Aerosols and Ammonia via VLT/VISIR Spatial Mapping 2016-17 Authors: Donnelly, P. T.; Fletcher, L. N.; Orton, G. S.; Melin, H. Bibcode: 2017EPSC...11..581D Altcode: The VISIR mid-IR imager (5-25 µm) on the Very Large Telescope (VLT) has been providing infrared spatial and temporal support for NASA's Juno spacecraft, constraining atmospheric thermal conditions in the upper troposphere (100-700 mbar) and stratosphere (1-10 mbar). Our pre-Juno-arrival dataset (January-August 2016) demonstrated that Jupiter's North Equatorial Belt (NEB) began a northward expansion in late 2015, consistent with the 3-5 year cycle of NEB activity. VISIR detected two new thermal waves during this period; an upper tropospheric wave in the mid-NEB and a stratospheric wave centred on the eastward jet at 23.9°N. The latter was quasi-stationary and both waves are morphologically similar to those observed during the 2000 expansion event by Cassini. We now extend this analysis to coincide with Juno's perijove encounters, once every 53.5 days. We report (i) the continued existence of the mid-NEB wave; (ii) evolution of Jupiter's North Temperate Belt (NTB) following the October 2016 outbreak; and (iii) complex thermal variability associated with a mid-SEB outbreak during 2017. We discuss zonally-averaged temperatures, aerosols and ammonia distributions derived from VLT data (taking centre-to-limb variations into account), comparing the upper-tropospheric aerosols and ammonia to the findings of Juno's near-infrared and microwave observations. Title: The New Frontiers Saturn PRobe Interior and aTmosphere Explorer (SPRITE) Mission Proposal Authors: Atkinson, D. H.; Simon, A. A.; Banfield, D.; Atreya, S.; Blacksberg, J.; Brinckerhoff, W.; Colaprete, A.; Coustenis, A.; Fletcher, L.; Guillot, T.; Hofstadter, M.; Lunine, J.; Mahaffy, P.; Marley, M.; Mousis, O.; Spilker, T.; Trainer, M.; Webster, C. Bibcode: 2017EPSC...11..356A Altcode: SPRITE is a Saturn Probe mission proposal submitted to NASA under the New Frontiers 4 program. Title: Scientific rationale and concepts for in situ probe exploration of Uranus and Neptune Authors: Mousis, O.; Atkinson, D.; Amato, M.; Aslam, S.; Atreya, S.; Blanc, M.; Brugger, B.; Calcutt, S.; Cavalié, T.; Charnoz, S.; Coustenis, A.; Deleuil, M.; Dobrijevic, M.; Encrenaz, T.; Ferri, F.; Fletcher, L.; Guillot, T.; Hartogh, P.; Hofstadter, M.; Hueso, R. Bibcode: 2017EPSC...11..299M Altcode: Uranus and Neptune, referred to as ice giants, are fundamentally different from the better-known gas giants (Jupiter and Saturn). Exploration of an ice giant system is a high-priority science objective, as these systems (including the magnetosphere, satellites, rings, atmosphere, and interior) challenge our understanding of planetary formation and evolution. The importance of the ice giants is reflected in NASA's 2011 Decadal Survey, comments from ESA's SSC in response to L2/L3 mission proposals and results of the 2017 NASA/ESA Ice Giants study. A crucial part of exploration of the ice giants is in situ sampling of the atmosphere via an atmospheric probe. A probe would bring insights in two broad themes: the formation history of our Solar System and the processes at play in planetary atmospheres. Here we summarize the science driver for in situ measurements at these two planets and discuss possible mission concepts that would be consistent with the constraints of ESA M-class missions. Title: Saturn at Northern Summer Solstice: Thermal Structure during the Finale of the Cassini Mission Authors: Fletcher, L. N.; Guelet, S.; Orton, G. S.; Sinclair, J. A.; Fouchet, T.; Irwin, P.; Li, L.; Flasar, F. M. Bibcode: 2017EPSC...11..450F Altcode: With the culmination of 13 years of orbital exploration of Saturn by the Cassini spacecraft, we now have the most comprehensive characterisation of a seasonal giant planet ever obtained. The longevity of Cassini has meant that we can explore atmospheric processes from solstice to solstice using infrared remote sensing, including: the formation and dissipation of stratospheric polar vortices; the evolution of Saturn's equatorial oscillation; and the aftermath of the 2010-11 springtime storm. Title: Saturn's stratospheric equatorial oscillation and wave activity through the Cassini epoch Authors: Guerlet, S.; Fouchet, T.; Spiga, A.; Hesman, B.; Gorius, N.; Fletcher, L.; Flasar, F. M. Bibcode: 2017EPSC...11..172G Altcode: We study the evolution of Saturn's Quasi-Periodic Oscillation, a dynamical phenomenon observed in Saturn's stratosphere that has counterparts in Jupiter and the Earth stratospheres as well. Thermal infrared spectra acquired by Cassini/CIRS in limb viewing geometry in 2015 are used to derive 2-D latitude-pressure temperature and thermal wind maps in Saturn's stratosphere. These maps are compared to previous observations from 2005 and 2010 to characterize and study the evolution of the vertical structure of Saturn's equatorial oscillation. This phenomenon is thought to result from the interaction between upward-propagating waves and the mean zonal flow, but little is known on Saturn's stratospheric wave activity. CIRS nadir spectra are then used to map stratospheric temperatures with longitude and characterize planetary waves in the tropical region (20N-20S). Title: Saturn's Atmospheric Photochemistry: Haze Production in Ring-Shadowed Atmosphere and within the Hexagon Authors: Edgington, S. G.; Atreya, S. K.; Wilson, E. H.; Baines, K. H.; West, R. A.; Bjoraker, G. L.; Fletcher, L. N.; Momary, T. Bibcode: 2017EPSC...11..386E Altcode: This research explores the impact of seasonal changes within Saturn's atmosphere and the evolution of hazes within it. Title: The thermal infrared continuum in solar flares Authors: Fletcher, Lyndsay; Simoes, Paulo; Kerr, Graham Stewart; Hudson, Hugh S.; Gimenez de Castro, C. Guillermo; Penn, Matthew J. Bibcode: 2017SPD....4810821F Altcode: Observations of the Sun with the Atacama Large Millimeter Array have now started, and the thermal infrared will regularly be accessible from the NSF’s Daniel K. Inouye Solar Telescope. Motivated by the prospect of these new observations, and by recent flare detections in the mid infrared, we set out here to model and understand the source of the infrared continuum in flares, and to explore its diagnostic capability for the physical conditions in the flare atmosphere. We use the 1D radiation hydrodynamics code RADYN to calculate mid-infrared continuum emission from model atmospheres undergoing sudden deposition of energy by non-thermal electrons. We identify and characterise the main continuum thermal emission processes relevant to flare intensity enhancement in the mid- to far-infrared (2-200 micron) spectral range as free-free emission on neutrals and ions. We find that the infrared intensity evolution tracks the energy input to within a second, albeit with a lingering intensity enhancement, and provides a very direct indication of the evolution of the atmospheric ionization. The prediction of highly impulsive emission means that, on these timescales, the atmospheric hydrodynamics need not be considered in analysing the mid-IR signatures. Title: Jupiter's auroral-related stratospheric heating and chemistry I: Analysis of Voyager-IRIS and Cassini-CIRS spectra Authors: Sinclair, J. A.; Orton, G. S.; Greathouse, T. K.; Fletcher, L. N.; Moses, J. I.; Hue, V.; Irwin, P. G. J. Bibcode: 2017Icar..292..182S Altcode: Auroral processes are evident in Jupiter's polar atmosphere over a large range in wavelength (X-ray to radio). In particular, previous observations in the mid-infrared (5-15 μm) have shown enhanced emission from CH4, C2H2 and C2H4 and further stratospheric hydrocarbon species in spatial regions coincident with auroral processes observed at other wavelengths. These regions, described as auroral-related hotspots, observed at approximately 160°W to 200°W (System III) at high-northern latitudes and 330°W to 80°W at high-southern latitudes, indicate that auroral processes modify the thermal structure and composition of the neutral atmosphere. However, previous studies have struggled to differentiate whether the aforementioned enhanced emission is a result of either temperature changes and/or changes in the concentration of the emitting species. We attempt to address this degeneracy in this work by performing a retrieval analysis of Voyager 1-IRIS spectra (acquired in 1979) and Cassini-CIRS spectra (acquired in 2000/2001) of Jupiter. Retrievals of the vertical temperature profile in Cassini-CIRS spectra covering the auroral-related hotspots indicate the presence of two discrete vertical regions of heating at the 1-mbar level and at pressures of 10-μbar and lower. For example, in Cassini-CIRS 2.5 cm-1 'MIRMAP' spectra at 70°N (planetographic) 180°W (centred on the auroral oval), we find temperatures at the 1-mbar level and 10-μbar levels are enhanced by 15.3 ± 5.2 K and 29.6 ± 15.0 K respectively, in comparison to results at 70°N, 60°W in the same dataset. High temperatures at 10 μbar and lower pressures were considered indicative of joule heating, ion and/or electron precipitation, ion-drag and energy released form exothermic ion-chemistry. However, we conclude that the heating at the 1-mbar level is the result of either a layer of aurorally-produced haze particles, which are heated by incident sunlight and/or adiabatic heating by downwelling within the auroral hot-spot region. The former mechanism would be consistent with the vertical profiles of polycyclic aromatic hydrocarbons (PAHs) and haze particles predicted in auroral-chemistry models (Wong et al., 2000; 2003). Retrievals of C2H2 and C2H6 were also performed and indicate C2H2 is enriched but C2H6 is depleted in auroral regions relative to quiescent regions. For example, using CIRS Δν∼ = 2.5 cm-1 spectra, we determined that C2H2 at 0.98 mbar increases by 175.3 ± 89.3 ppbv while C2H6 at 4.7 mbar decreases by 0.86 ± 0.59 ppmv in comparing results at 70°N, 180°W and 70°N, 60°W. These results represent a mean of values retrieved from different initial assumptions and thus we believe they are robust. We believe these contrasts in C2H2 and C2H6 between auroral and quiescent regions can be explained by a coupling of auroral-driven chemistry and horizontal advection. Ion-neutral and electron recombination chemistry in the auroral region enriches all C2 hydrocarbons but in particular, the unsaturated C2H2 and C2H4 hydrocarbons. Once advected outside of the auroral region, the unsaturated C2 hydrocarbons are converted into C2H6 by neutral photochemistry thereby enriching C2H6 in quiescent regions, which gives the impression it is depleted inside the auroral region. Title: Modelling of the hydrogen Lyman lines during solar flares Authors: Brown, Stephen Alistair; Fletcher, Lyndsay; Labrosse, Nicolas Bibcode: 2017SPD....4810303B Altcode: The hydrogen Lyman series and continuum are both observed with high cadence and spectral resolution by the EVE instrument on NASA’s solar dynamics observatory. The Lyman lines, some of which will also be observed by the SPICE spectrometer on Solar Orbiter, can provide useful information about the dynamics of the solar chromosphere during a flare, where most of the event’s energy is deposited. In Brown et al (2016), we measured line shifts in the Lyman lines using the EVE instrument and calculated corresponding plasma flow speeds of around 30 kilometres per second. However, the observed signs of these shifts varied. We have also modelled Lyman line profiles output from the radiative hydrodynamic code RADYN (Carlsson & Stein 1997, Allred et al 2015) and the radiative transfer code RH (Uitenbroek 2001) and present our initial findings. We show that the dynamics of the plasma are reflected in complex features in the true line profile, but that the detection of a line shift in a particular direction from EVE observations may not be indicative of the true plasma flow, particularly when these model profiles are passed through the EVE instrumental response. We present several cases of atmospheric responses for differing amounts of energy input, and outline interesting features in the Lyman line profiles which are thought to be linked to the response of the dynamic atmosphere. Title: Formation of diamonds in laser-compressed hydrocarbons at planetary interior conditions Authors: Kraus, D.; Vorberger, J.; Pak, A.; Hartley, N. J.; Fletcher, L. B.; Frydrych, S.; Galtier, E.; Gamboa, E. J.; Gericke, D. O.; Glenzer, S. H.; Granados, E.; MacDonald, M. J.; MacKinnon, A. J.; McBride, E. E.; Nam, I.; Neumayer, P.; Roth, M.; Saunders, A. M.; Schuster, A. K.; Sun, P.; van Driel, T.; Döppner, T.; Falcone, R. W. Bibcode: 2017NatAs...1..606K Altcode: The effects of hydrocarbon reactions and diamond precipitation on the internal structure and evolution of icy giant planets such as Neptune and Uranus have been discussed for more than three decades1. Inside these celestial bodies, simple hydrocarbons such as methane, which are highly abundant in the atmospheres2, are believed to undergo structural transitions3,4 that release hydrogen from deeper layers and may lead to compact stratified cores5-7. Indeed, from the surface towards the core, the isentropes of Uranus and Neptune intersect a temperature-pressure regime in which methane first transforms into a mixture of hydrocarbon polymers8, whereas, in deeper layers, a phase separation into diamond and hydrogen may be possible. Here we show experimental evidence for this phase separation process obtained by in situ X-ray diffraction from polystyrene (C8H8)n samples dynamically compressed to conditions around 150 GPa and 5,000 K; these conditions resemble the environment around 10,000 km below the surfaces of Neptune and Uranus9. Our findings demonstrate the necessity of high pressures for initiating carbon-hydrogen separation3 and imply that diamond precipitation may require pressures about ten times as high as previously indicated by static compression experiments4,8,10. Our results will inform mass-radius relationships of carbon-bearing exoplanets11, provide constraints for their internal layer structure and improve evolutionary models of Uranus and Neptune, in which carbon-hydrogen separation could influence the convective heat transport7. Title: Jupiter's North Equatorial Belt expansion and thermal wave activity ahead of Juno's arrival Authors: Fletcher, L. N.; Orton, G. S.; Sinclair, J. A.; Donnelly, P.; Melin, H.; Rogers, J. H.; Greathouse, T. K.; Kasaba, Y.; Fujiyoshi, T.; Sato, T. M.; Fernandes, J.; Irwin, P. G. J.; Giles, R. S.; Simon, A. A.; Wong, M. H.; Vedovato, M. Bibcode: 2017GeoRL..44.7140F Altcode: 2017arXiv170805179F The dark colors of Jupiter's North Equatorial Belt (NEB, 7-17°N) appeared to expand northward into the neighboring zone in 2015, consistent with a 3-5 year cycle. Inversions of thermal-IR imaging from the Very Large Telescope revealed a moderate warming and reduction of aerosol opacity at the cloud tops at 17-20°N, suggesting subsidence and drying in the expanded sector. Two new thermal waves were identified during this period: (i) an upper tropospheric thermal wave (wave number 16-17, amplitude 2.5 K at 170 mbar) in the mid-NEB that was anticorrelated with haze reflectivity; and (ii) a stratospheric wave (wave number 13-14, amplitude 7.3 K at 5 mbar) at 20-30°N. Both were quasi-stationary, confined to regions of eastward zonal flow, and are morphologically similar to waves observed during previous expansion events. Title: Independent evolution of stratospheric temperatures in Jupiter's northern and southern auroral regions from 2014 to 2016 Authors: Sinclair, J. A.; Orton, G. S.; Greathouse, T. K.; Fletcher, L. N.; Tao, C.; Gladstone, G. R.; Adriani, A.; Dunn, W.; Moses, J. I.; Hue, V.; Irwin, P. G. J.; Melin, H.; Giles, R. S. Bibcode: 2017GeoRL..44.5345S Altcode: We present retrievals of the vertical temperature profile of Jupiter's high latitudes from Infrared Telescope Facility-Texas Echelon Cross Echelle Spectrograph measurements acquired on 10-11 December 2014 and 30 April to 1 May 2016. Over this time range, 1 mbar temperature in Jupiter's northern and southern auroral regions exhibited independent evolution. The northern auroral hot spot exhibited negligible net change in temperature at 1 mbar and its longitudinal position remained fixed at 180°W (System III), whereas the southern auroral hot spot exhibited a net increase in temperature of 11.1 ± 5.2 K at 0.98 mbar and its longitudinal orientation moved west by approximately 30°. This southern auroral stratospheric temperature increase might be related to (1) near-contemporaneous brightening of the southern auroral ultraviolet/near-infrared H3+ emission measured by the Juno spacecraft and (2) an increase in the solar dynamical pressure in the preceding 3 days. We therefore suggest that 1 mbar temperature in the southern auroral region might be modified by higher-energy charged particle precipitation. Title: Latitudinal variability in Jupiter's tropospheric disequilibrium species: GeH4, AsH3 and PH3 Authors: Giles, R. S.; Fletcher, L. N.; Irwin, P. G. J. Bibcode: 2017Icar..289..254G Altcode: 2016arXiv161009073G Jupiter's tropospheric composition is studied using high-resolution, spatially-resolved 5-μm observations from the CRIRES instrument at the Very Large Telescope. The high resolving power (R = 96,000) allows us to spectrally resolve the line shapes of individual molecular species in Jupiter's troposphere and, by aligning the slit north-south along Jupiter's central meridian, we are able to search for any latitudinal variability. Despite the high spectral resolution, we find that there are significant degeneracies between the cloud structure and aerosol scattering properties that complicate the retrievals of tropospheric gaseous abundances and limit conclusions on any belt-zone variability. However, we do find evidence for variability between the equatorial regions of the planet and the polar regions. Arsine (AsH3) and phosphine (PH3) both show an enhancement at high latitudes, while the abundance of germane (GeH4) remains approximately constant. These observations contrast with the theoretical predictions from Wang et al. (2016) and we discuss the possible explanations for this difference. Title: Cycles of activity in the Jovian atmosphere Authors: Fletcher, L. N. Bibcode: 2017GeoRL..44.4725F Altcode: 2017arXiv170805180F Jupiter's banded appearance may appear unchanging to the casual observer, but closer inspection reveals a dynamic, ever-changing system of belts and zones with distinct cycles of activity. Identification of these long-term cycles requires access to data sets spanning multiple Jovian years, but explaining them requires multispectral characterization of the thermal, chemical, and aerosol changes associated with visible color variations. The Earth-based support campaign for Juno's exploration of Jupiter has already characterized two upheaval events in the equatorial and temperate belts that are part of long-term Jovian cycles, whose underlying sources could be revealed by Juno's exploration of Jupiter's deep atmosphere. Title: Non-Gaussian Velocity Distributions in Solar Flares from Extreme Ultraviolet Lines: A Possible Diagnostic of Ion Acceleration Authors: Jeffrey, Natasha L. S.; Fletcher, Lyndsay; Labrosse, Nicolas Bibcode: 2017ApJ...836...35J Altcode: 2017arXiv170102196J In a solar flare, a large fraction of the magnetic energy released is converted rapidly to the kinetic energy of non-thermal particles and bulk plasma motion. This will likely result in non-equilibrium particle distributions and turbulent plasma conditions. We investigate this by analyzing the profiles of high temperature extreme ultraviolet emission lines from a major flare (SOL2014-03-29T17:44) observed by the EUV Imaging Spectrometer (EIS) on Hinode. We find that in many locations the line profiles are non-Gaussian, consistent with a kappa distribution of emitting ions with properties that vary in space and time. At the flare footpoints, close to sites of hard X-ray emission from non-thermal electrons, the κ index for the Fe xvi 262.976 Å line at 3 MK takes values of 3-5. In the corona, close to a low-energy HXR source, the Fe xxiii 263.760 Å line at 15 MK shows κ values of typically 4-7. The observed trends in the κ parameter show that we are most likely detecting the properties of the ion population rather than any instrumental effects. We calculate that a non-thermal ion population could exist if locally accelerated on timescales ≤0.1 s. However, observations of net redshifts in the lines also imply the presence of plasma downflows, which could lead to bulk turbulence, with increased non-Gaussianity in cooler regions. Both interpretations have important implications for theories of solar flare particle acceleration. Title: Summer at Saturn's North Pole: Seasonal Changes Seen by ISS & CIRS on Cassini, and VLT on the Ground Authors: Sayanagi, K. M.; Blalock, J.; Fletcher, L. N.; Ingersoll, A. P.; Dyudina, U.; Ewald, S. P. Bibcode: 2016AGUFM.P33B2137S Altcode: We report seasonal changes in Saturn's north polar vortex seen by Cassini ISS, Cassini CIRS, and ground-based VLT VISIR thermal infrared observations. ISS observation of Saturn's northern high latitudes show that a reflective, bright polar spot has formed over the north pole, seen first in images captured in 2016. This coincides with the warm cyclonic north polar vortex that has been steadily warming since it was first discovered in 2007 by Cassini CIRS. The reflective spot was not present when the north pole was observed during the previous period of Cassini spacecraft's high-inclination orbits in 2012. In 2012, the concentration of light-scattering aerosols within 2-degree latitude of the north pole appeared to be less than that of the surrounding region, and appeared dark in all ISS filters. The new bright spot over the north pole is similar to that over the south pole seen in 2007. In 2007, Saturn was approaching the equinox of 2009 and south pole had been continuously illuminated since the previous equinox in 1995. The bright spot over the summer south pole in 2007 was hypothesized to consist of aerosols produced by ultraviolet photodissociation of hydrocarbon molecules; we follow this hypothesis to propose that the new bright spot over the north pole is also produced by the same mechanism. We argue that, in 2012 (3 years after equinox), the north polar bright spot hadn't formed because the ultraviolet insolation was not sufficient to produce enough photochemical aerosols. The new polar bright cloud formation is consistent with the rising abundances of stratospheric hydrocarbons (potential precursors to aerosol formation) over the north polar region as tracked by CIRS (Fletcher et al., 2015). In addition to ISS images, we also present CIRS and VLT-VISIR thermal maps of the northern high latitudes as the new north polar bright spot is expected to have implications on radiative energy balance. Our research has been supported by the Cassini Project, NASA grants OPR NNX11AM45G, CDAPS NNX15AD33G, PATM NNX14AK07G, and NSF grant AAG 1212216. Title: The strength and evolution of stratospheric-auroral processes on Jupiter, as observed by IRTF-TEXES Authors: Sinclair, J. A.; Orton, G. S.; Greathouse, T. K.; Fletcher, L. N.; Moses, J. I.; Hue, V.; Irwin, P. G.; Melin, H.; Giles, R. Bibcode: 2016AGUFM.P33C2149S Altcode: Auroral processes on Jupiter are evident over a large range of wavelengths. Juno's JIRAM (Jovian Infrared Auroral Mapper) and UVS (Ultraviolet Spectrometer) instruments will observe Jupiter's auroral emission at near-infrared and ultraviolet wavelengths, highlighting the precipitation of charged particles in Jupiter's thermosphere. These observations can then be related to measurements by Juno's MAG (magnetometer), JADE (Jovian Auroral Distributions Experiment) and JEDI instruments (Jovian Energetic Particle Detector Instrument), which will prove a powerful tool in studying the interaction of Jupiter's atmosphere with the external magnetosphere. However, Juno's scientific payload does not include a mid-infrared instrument (5 - 15 microns) capable of sounding Jupiter's stratosphere in which a significant amount of energy associated with auroral processes is deposited. As demonstrated by Sinclair et al., 2016a (under review) from a retrieval analysis of Voyager-IRIS (Infrared Interferometer Spectrometer) observations in 1979, Cassini-CIRS (Composite Infrared Spectrometer) observations in 2001 and IRTF-TEXES (Texas Echelon Cross Echelle Spectrograph) observations in 2014, temperatures in the northern auroral region at 70°N, 180°W are elevated by up to approximately 20 K and 35 K at the 1-mbar and 10-ubar levels respectively, in comparison to quiescent longitudes (see attached Figure). However, the physical mechanisms responsible for modifications of the thermal structure and composition of the stratosphere in auroral regions are still not well understood. We hope to better understand the processes driving the auroral-stratosphere interaction on Jupiter by characterizing whether and by what magnitude the thermal structure and composition of the stratosphere evolve at Jupiter's high latitudes. In April 2016, we obtained IRTF-TEXES measurements of Jupiter's high-latitudes under similar conditions to those obtained in December 2014. We will perform a retrieval analysis to determine the vertical profiles of temperature, C2H2, C2H4 and C2H6. Results will be compared with those in December 2014 to determine the 3D evolution of the thermal structure and composition in proximity to the auroral regions: the attached Figure shows preliminary temperature results. Title: Arcade Implosion Caused by a Filament Eruption in a Flare Authors: Wang, Juntao; Simões, P. J. A.; Fletcher, L.; Thalmann, J. K.; Hudson, H. S.; Hannah, I. G. Bibcode: 2016ApJ...833..221W Altcode: 2016arXiv161005931W Coronal implosions—the convergence motion of plasmas and entrained magnetic field in the corona due to a reduction in magnetic pressure—can help to locate and track sites of magnetic energy release or redistribution during solar flares and eruptions. We report here on the analysis of a well-observed implosion in the form of an arcade contraction associated with a filament eruption, during the C3.5 flare SOL2013-06-19T07:29. A sequence of events including the magnetic flux-rope instability and distortion, followed by a filament eruption and arcade implosion, lead us to conclude that the implosion arises from the transfer of magnetic energy from beneath the arcade as part of the global magnetic instability, rather than due to local magnetic energy dissipation in the flare. The observed net contraction of the imploding loops, which is found also in nonlinear force-free field extrapolations, reflects a permanent reduction of magnetic energy underneath the arcade. This event shows that, in addition to resulting in the expansion or eruption of an overlying field, flux-rope instability can also simultaneously implode an unopened field due to magnetic energy transfer. It demonstrates the “partial opening of the field” scenario, which is one of the ways in 3D to produce a magnetic eruption without violating the Aly-Sturrock hypothesis. In the framework of this observation, we also propose a unification of three main concepts for active region magnetic evolution, namely the metastable eruption model, the implosion conjecture, and the standard “CSHKP” flare model. Title: SPRITE - The Saturn PRobe Interior and aTmosphere Explorer Mission. Authors: Atkinson, D. H.; Simon, A. A.; Banfield, D. J.; Atreya, S. K.; Blacksberg, J.; Brinckerhoff, W. B.; Colaprete, A.; Coustenis, A.; Danner, R. M.; Fletcher, L. N.; Guillot, T.; Hofstadter, M. D.; Keithly, D.; Lobbia, M. A.; Lunine, J. I.; Mahaffy, P. R.; Marley, M. S.; Mousis, O.; Spilker, T. R.; Trainer, M. G.; Webster, C. R.; Youmans, T. A. Bibcode: 2016AGUFM.P33B2132A Altcode: The 2013-2022 Planetary Science Decadal Survey (PSDS) Vision and Voyages Planetary identified a Saturn Probe mission as a high priority mission target for the NASA New Frontiers program. Fundamental measurements of noble gas abundances and isotope ratios of hydrogen, carbon, oxygen, and nitrogen, as well as the interior structure of Saturn are needed to help constrain Solar System formation models and to provide an improved context for understanding exoplanet systems. The SPRITE mission would fulfill the PSDS scientific goals for in situ exploration of Saturn, and would additionally provide ground truth for remote sensing that would improve the understanding of the composition and interior structure of Saturn and, by proxy, extrasolar giant planets. In Situ measurements are the only means to address many key questions regarding the structure and composition of Saturn's atmosphere including the abundance of noble gases and key isotopes, the abundance of helium needed to understand the formation history and thermal evolution of Saturn, and the abundance of water in the deep atmosphere, a key diagnostic of Saturn's formation since it is thought that the heavy elements were delivered by water-bearing planetesimals. The SPRITE atmospheric entry probe mission including remote sensing from a carrier-relay spacecraft would measure many of these key atmospheric constituents as well as the atmospheric structure of Saturn including temperature, pressure and wind speeds along the probe descent path thereby providing interior science not accessible to remote sensing measurements. Additionally, the SPRITE carrier-relay spacecraft would make remote sensing measurements to support probe measurements in the upper troposphere of Saturn. Title: Analysis of Saturn's Hexagon between 2012 and 2016: Dynamical and Morphological Changes Authors: Blalock, J.; Sayanagi, K. M.; Fletcher, L. N.; Ingersoll, A. P.; Dyudina, U.; Ewald, S. P. Bibcode: 2016AGUFM.P31D..06B Altcode: We present analyses of Saturn's wind fields and cloud morphology in the northern Hexagon region, combining visible-light imaging from the Cassini ISS instrument with measurements of Saturn's thermal structure and zonal wind shear from the Cassini CIRS instrument and ground-based VLT/VISIR imaging. Our study focuses on temporal changes occurring in the region around 77 degree N planetocentric latitude, which has been illuminated by sunlight since 2008, and captured by ISS with good observation geometries in 2012-2013 and 2016. The goal of our analysis is to detect any change in the cloud morphology, atmospheric dynamics and thermal structure. To measure the wind field in the Hexagon region, we utilize the two-dimensional correlation imaging velocimetry (CIV) technique. We also calculate the relative vorticity and divergence from the wind field. To detect changes in the dynamics of the Hexagon, we compare measurements of the wind, relative vorticity, and divergence in 2012 with those from 2016, as well as evaluating changes in the zonal mean temperature gradient across the Hexagon boundaries. We compare cloud reflectivity between 2012 and 2016 in images that show the Hexagon under similar illumination conditions, calculating the zonal mean reflectivity as a function of latitude. Furthermore, we assess the winds and cloud reflectivity at several wavelengths in order to look for changes occurring at different altitudes, and relate this to temperature variations in the 100-700 mbar region assessed from Cassini and ground-based VLT imaging. Specifically, we focus on the CB2 continuum filter which senses thick tropospheric clouds and the MT2 and MT3 methane filters which sense the upper tropospheric and stratospheric haze layers. Our work has been supported by NASA PATM NNX14AK07G, CDAPS NNX15AD33G, NSF AAG 1212216, and NASA NESSF NNX15AQ70H. Title: Photochemistry in Saturn's Ring-Shadowed Atmosphere: Modulation of Hydrocarbons and Observations of Dust Content Authors: Edgington, S. G.; Atreya, S. K.; Wilson, E. H.; Baines, K. H.; West, R. A.; Bjoraker, G. L.; Fletcher, L. N.; Momary, T. Bibcode: 2016AGUFM.P33B2133E Altcode: Cassini has been orbiting Saturn for over twelve years now. During this epoch, the ring shadow has moved from covering much of the northern hemisphere with solar inclination of 24 degrees to covering a large swath south of the equator and it continues to move southward. At Saturn Orbit Insertion in 2004, the projection of the A-ring onto Saturn reached as far as 40N along the central meridian (52N at the terminator). At its maximum extent, the ring shadow can reach as far as 48N/S (58N/S at the terminator). The net effect is that the intensity of both ultraviolet and visible sunlight penetrating through the rings to any particular latitude will vary depending on both Saturn's axis relative to the Sun and the optical thickness of each ring system. In essence, the rings act like semi-transparent venetian blinds.Previous work examined the variation of the solar flux as a function of solar inclination, i.e. for each 7.25-year season at Saturn. Here, we report on the impact of the oscillating ring shadow on the photolysis and production rates of hydrocarbons (acetylene, ethane, propane, and benzene) and phosphine in Saturn's stratosphere and upper troposphere. The impact of these production and loss rates on the abundance of long-lived photochemical products leading to haze formation are explored. We assess their impact on phosphine abundance, a disequilibrium species whose presence in the upper troposphere can be used as a tracer of convective processes in the deeper atmosphere.We will also present our ongoing analysis of Cassini's CIRS, UVIS, and VIMS datasets that provide an estimate of the evolving haze content of the northern hemisphere and we will begin to assess the implications for dynamical mixing. In particular, we will examine how the now famous hexagonal jet stream acts like a barrier to transport, isolating Saturn's north polar region from outside transport of photochemically-generated molecules and haze.The research described in this paper was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Copyright 2016 California Institute of Technology. Government sponsorship is acknowledged. Title: Evidence for kappa distributions of ions in the flaring solar atmosphere from extreme ultraviolet spectroscopy Authors: Fletcher, L.; Jeffrey, N. L. S.; Labrosse, N. Bibcode: 2016AGUFMSH13D..02F Altcode: We present new evidence for ion kappa distributions in the lower solar atmosphere, and in the solar corona, during the impulsive energy release phase of solar flares. The existence of non-Maxwellian electron distributions during flares is well established from X-ray spectroscopy, but ion populations are harder to diagnose. By careful fitting of the spectral line profiles from highly ionised states of iron observed during flares by the Extreme Ultraviolet Imaging Spectrometer (EIS) on the Hinode spacecraft, and taking into account the spectrometer's known instrumental characteristics, we establish that the physical line profile is consistent with that emitted by a kappa distribution of ions. Kappa distributions provide a far better fit than Maxwellian distributions in many cases, and are detected both at the chromospheric footpoints and in the corona during flares, but with different parameters. We discuss the possible origins of these ion distributions, and their implications for solar flare ion acceleration. Title: Tapping the Core - a study of Alfvénic energy flow in an erupting flux-rope configuration Authors: Fletcher, L.; Dalmasse, K.; Gibson, S. E.; Fan, Y. Bibcode: 2016AGUFMSH31B2564F Altcode: We analyze the evolution of reconnecting magnetic field in a 3-D numerical simulation of a partially-ejected solar flux rope, with a focus on understanding how the flux rope dynamics is linked to the flow of energy through the field and the solar atmosphere as Alfvénic Poynting flux. The magnetic flux rope splits in two during its eruption, with reconnection taking place between the erupting rope and surrounding fields, and internally in the strong field of the rope. We track the Poynting flux entering and leaving the simulation current sheets, and by mapping this down to the solar surface we identify locations of weak and strong energy deposition in the lower atmosphere. Our tracking method enables us to link the lower atmosphere signatures to different stages of the coronal reconnection. We find a predominantly two-ribbon morphology in the locations of Poynting flux deposition in the lower atmosphere, in which the transition from reconnection involving weaker field external to the flux rope, to reconnection involving the flux rope core field, is accompanied by rapid ribbon spreading. In the core-field reconnection phase, ribbons move into strong field regions on the solar surface, and locations of highly concentrated downward-directed Poynting flux are found, which may be linked to the most energetic flare `footpoints' seen in optical and hard X-ray emission. Title: Recruiting flare hunters for citizen science Authors: Fletcher, Lyndsay; Berlicki, Arkadiusz; Awasthi, Arun Kumar; Gronkiewicz, Dominik Bibcode: 2016A&G....57f6.21F Altcode: Lyndsay Fletcher, Arkadiusz Berlicki, Arun Kumar Awasthi and Dominik Gronkiewicz describe how they established F-HUNTERS, a pro-am solar flare observing campaign. Title: Doppler speeds of the hydrogen Lyman lines in solar flares from EVE Authors: Brown, Stephen A.; Fletcher, Lyndsay; Labrosse, Nicolas Bibcode: 2016A&A...596A..51B Altcode: 2016arXiv161004007B
Aims: The hydrogen Lyman lines provide important diagnostic information about the dynamics of the chromosphere, but there have been few systematic studies of their variability during flares. We investigate Doppler shifts in these lines in several flares, and use these to calculate plasma speeds.
Methods: We use spectral data from the Multiple EUV Grating Spectrograph B (MEGS-B) detector of the Extreme-Ultraviolet Variability Experiment (EVE) instrument on the Solar Dynamics Observatory. MEGS-B obtains full-disk spectra of the Sun at a resolution of 0.1 nm in the range 37-105 nm, which we analyse using three independent methods. The first method performs Gaussian fits to the lines, and compares the quiet-Sun centroids with the flaring ones to obtain the Doppler shifts. The second method uses cross-correlation to detect wavelength shifts between the quiet-Sun and flaring line profiles. The final method calculates the "center-of-mass" of the line profile, and compares the quiet-Sun and flaring centroids to obtain the shift.
Results: In a study of 6 flares we find strong signatures of both upflow and downflow in the Lyman lines, with speeds measured in Sun-as-a-Star data of around 10 km s-1, and speeds in the flare excess signal of around 30 km s-1.
Conclusions: All events showing upflows in Lyman lines are associated with some kind of eruption or coronal flow in imaging data, which may be responsible for the net blueshifts. Events showing downflows in the Lyman lines may be associated with loop contraction or faint downflows, but it is likely that chromospheric condensation flows are also contributing. Title: Doppler speeds of the hydrogen Lyman lines in solar flares from EVE Authors: Brown, Stephen; Fletcher, Lyndsay; Labrosse, Nicolas Bibcode: 2016usc..confE...7B Altcode: The hydrogen Lyman lines provide important diagnostic information about the dynamics of the chromosphere, but until recently there have been few systematic studies of their variability during flares. We investigate Doppler shifts in these lines in several flares, and use these to calculate plasma speeds. We use spectral data from the Multiple EUV Grating Spectrograph B (MEGS-B) detector on board the Extreme-Ultraviolet Variability Experiment (EVE) instrument on the Solar Dynamics Observatory. MEGS-B obtains full-disk spectra of the Sun at a resolution of 0.1nm in the range 37-105nm, which we analyse using three independent methods. The first method performs Gaussian fits to the lines, and compares the quiet-Sun centroids with the flaring ones to obtain the Doppler shifts. The second method uses cross-correlation to detect wavelength shifts between the quiet-Sun and flaring line profiles. The final method calculates the "center-of-mass" of the line profile, and compares the quiet-Sun and flaring centroids to obtain the shift. In a study of 6 flares we find signatures of both upflow and downflow in the Lyman lines, with speeds of around 10 km s^-1 in the line profiles that have not undergone pre-flare subtraction, and speeds in the flare-excess profiles of around 30 km s^-1 . We include analysis of AIA images of these events in order to understand potential contributions from material ejections, and find that not all upflows can be explained by ejecta. We discuss current and future attempts at modelling these line profiles. Title: The Hera Saturn entry probe mission Authors: Mousis, O.; Atkinson, D. H.; Spilker, T.; Venkatapathy, E.; Poncy, J.; Frampton, R.; Coustenis, A.; Reh, K.; Lebreton, J. -P.; Fletcher, L. N.; Hueso, R.; Amato, M. J.; Colaprete, A.; Ferri, F.; Stam, D.; Wurz, P.; Atreya, S.; Aslam, S.; Banfield, D. J.; Calcutt, S.; Fischer, G.; Holland, A.; Keller, C.; Kessler, E.; Leese, M.; Levacher, P.; Morse, A.; Muñoz, O.; Renard, J. -B.; Sheridan, S.; Schmider, F. -X.; Snik, F.; Waite, J. H.; Bird, M.; Cavalié, T.; Deleuil, M.; Fortney, J.; Gautier, D.; Guillot, T.; Lunine, J. I.; Marty, B.; Nixon, C.; Orton, G. S.; Sánchez-Lavega, A. Bibcode: 2016P&SS..130...80M Altcode: 2015arXiv151007685M The Hera Saturn entry probe mission is proposed as an M-class mission led by ESA with a contribution from NASA. It consists of one atmospheric probe to be sent into the atmosphere of Saturn, and a Carrier-Relay spacecraft. In this concept, the Hera probe is composed of ESA and NASA elements, and the Carrier-Relay Spacecraft is delivered by ESA. The probe is powered by batteries, and the Carrier-Relay Spacecraft is powered by solar panels and batteries. We anticipate two major subsystems to be supplied by the United States, either by direct procurement by ESA or by contribution from NASA: the solar electric power system (including solar arrays and the power management and distribution system), and the probe entry system (including the thermal protection shield and aeroshell). Hera is designed to perform in situ measurements of the chemical and isotopic compositions as well as the dynamics of Saturn's atmosphere using a single probe, with the goal of improving our understanding of the origin, formation, and evolution of Saturn, the giant planets and their satellite systems, with extrapolation to extrasolar planets. Hera's aim is to probe well into the cloud-forming region of the troposphere, below the region accessible to remote sensing, to the locations where certain cosmogenically abundant species are expected to be well mixed. By leading to an improved understanding of the processes by which giant planets formed, including the composition and properties of the local solar nebula at the time and location of giant planet formation, Hera will extend the legacy of the Galileo and Cassini missions by further addressing the creation, formation, and chemical, dynamical, and thermal evolution of the giant planets, the entire solar system including Earth and the other terrestrial planets, and formation of other planetary systems. Title: A dispersive wave pattern on Jupiter's fastest retrograde jet at 20°S Authors: Rogers, J. H.; Fletcher, L. N.; Adamoli, G.; Jacquesson, M.; Vedovato, M.; Orton, G. S. Bibcode: 2016Icar..277..354R Altcode: 2016arXiv160507883R A compact wave pattern has been identified on Jupiter's fastest retrograding jet at 20°S (the SEBs) on the southern edge of the South Equatorial Belt. The wave has been identified in both reflected sunlight from amateur observations between 2010 and 2015, thermal infrared imaging from the Very Large Telescope and near infrared imaging from the Infrared Telescope Facility. The wave pattern is present when the SEB is relatively quiescent and lacking large-scale disturbances, and is particularly notable when the belt has undergone a fade (whitening). It is generally not present when the SEB exhibits its usual large-scale convective activity ('rifts'). Tracking of the wave pattern and associated white ovals on its southern edge over several epochs have permitted a measure of the dispersion relationship, showing a strong correlation between the phase speed (-43.2 to -21.2 m/s) and the longitudinal wavelength, which varied from 4.4 to 10.0° longitude over the course of the observations. Infrared imaging sensing low pressures in the upper troposphere suggest that the wave is confined to near the cloud tops. The wave is moving westward at a phase speed slower (i.e., less negative) than the peak retrograde wind speed (-62 m/s), and is therefore moving east with respect to the SEBs jet peak. Unlike the retrograde NEBn jet near °N, which is a location of strong vertical wind shear that sometimes hosts Rossby wave activity, the SEBs jet remains retrograde throughout the upper troposphere, suggesting the SEBs pattern cannot be interpreted as a classical Rossby wave. 2D windspeeds and thermal gradients measured by Cassini in 2000 are used to estimate the quasi-geostrophic potential vorticity gradient as a means of understanding the origin of the a wave. We find that the vorticity gradient is dominated by the baroclinic term and becomes negative (changes sign) in a region near the cloud-top level (400-700 mbar) associated with the SEBs. Such a sign reversal is a necessary (but not sufficient) condition for the growth of baroclinic instabilities, which is a potential source of the meandering wave pattern. Title: A pioneer of solar astronomy Authors: Dalla, Silvia; Fletcher, Lyndsay Bibcode: 2016A&G....57e5.21D Altcode: Silvia Dalla and Lyndsay Fletcher assess the work of Annie Maunder, an outstanding observer and interpreter of observations, who argued for her innovative ideas with power and eloquence. Title: Simulations of the Mg II k and Ca II 8542 lines from an AlfvÉn Wave-heated Flare Chromosphere Authors: Kerr, Graham S.; Fletcher, Lyndsay.; Russell, Alexander J. B.; Allred, Joel C. Bibcode: 2016ApJ...827..101K Altcode: 2016arXiv160505888K We use radiation hydrodynamic simulations to examine two models of solar flare chromospheric heating: Alfvén wave dissipation and electron beam collisional losses. Both mechanisms are capable of strong chromospheric heating, and we show that the distinctive atmospheric evolution in the mid-to-upper chromosphere results in Mg II k-line emission that should be observably different between wave-heated and beam-heated simulations. We also present Ca II 8542 Å profiles that are formed slightly deeper in the chromosphere. The Mg II k-line profiles from our wave-heated simulation are quite different from those from a beam-heated model and are more consistent with Interface Region Imaging Spectrograph observations. The predicted differences between the Ca II 8542 Å in the two models are small. We conclude that careful observational and theoretical study of lines formed in the mid-to-upper chromosphere holds genuine promise for distinguishing between competing models for chromospheric heating in flares. Title: Flares In Time-Domain Surveys Authors: Kowalski, Adam; Hawley, Suzanne; Davenport, James; Berlicki, Arkadiusz; Cauzzi, Gianna; Fletcher, Lyndsay; Heinzel, Petr; Notsu, Yuta; Loyd, Parke; Martinez Oliveros, Juan Carlos; Pugh, Chloe; Schmidt, Sarah Jane; Karmakar, Subhajeet; Pye, John; Flaccomio, Ettore Bibcode: 2016csss.confE.126K Altcode: Proceedings for the splinter session "Flares in Time-Domain Surveys" convened at Cool Stars 19 on June 07, 2016 in Uppsala, Sweden. Contains a two page summary of the splinter session, links to YouTube talks, and a PDF copy of the slides from the presenters. Title: Probing Saturn's tropospheric cloud with Cassini/VIMS Authors: Barstow, J. K.; Irwin, P. G. J.; Fletcher, L. N.; Giles, R. S.; Merlet, C. Bibcode: 2016Icar..271..400B Altcode: 2016arXiv160102978B In its decade of operation the Cassini mission has allowed us to look deep into Saturn's atmosphere and investigate the processes occurring below its enshrouding haze. We use Visual and Infrared Mapping Spectrometer (VIMS) 4.6-5.2 μm data from early in the mission to investigate the location and properties of Saturn's cloud structure between 0.6 and 5 bar. We average nightside spectra from 2006 over latitude circles and model the spectral limb darkening using the NEMESIS radiative transfer and retrieval tool. We present our best-fit deep cloud model for latitudes -40∘ < λ <50∘ , along with retrieved abundances for NH3, PH3 and AsH3. We find an increase in NH3 abundance at the equator, a cloud base at ∼2.3 bar and no evidence for cloud particles with strong absorption features in the 4.6-5.2 μm wavelength range, all of which are consistent with previous work. Non-scattering cloud models assuming a composition of either NH3 or NH4SH, with a scattering haze overlying, fit limb darkening curves and spectra at all latitudes well; the retrieved optical depth for the tropospheric haze is decreased in the northern (winter) hemisphere, implying that the haze has a photochemical origin. Our ability to test this hypothesis by examining spectra at different seasons is restricted by the varying geometry of VIMS observations over the life of the mission, and the appearance of the Saturn storm towards the end of 2010. Title: Time variability of Neptune's horizontal and vertical cloud structure revealed by VLT/SINFONI and Gemini/NIFS from 2009 to 2013 Authors: Irwin, P. G. J.; Fletcher, L. N.; Tice, D.; Owen, S. J.; Orton, G. S.; Teanby, N. A.; Davis, G. R. Bibcode: 2016Icar..271..418I Altcode: New observations of Neptune's clouds in the near infrared were acquired in October 2013 with SINFONI on ESO's Very Large Telescope (VLT) in Chile. SINFONI is an Integral Field Unit spectrometer returning a 64 × 64 pixel image with 2048 wavelengths. Image cubes in the J-band (1.09-1.41 μm) and H-band (1.43-1.87 μm) were obtained at spatial resolutions of 0.1″and 0.025″per pixel, while SINFONI's adaptive optics provided an effective resolution of approximately 0.1″. Image cubes were obtained at the start and end of three successive nights to monitor the temporal development of discrete clouds both at short timescales (i.e. during a single night) as well as over the longer period of the three-day observing run. These observations were compared with similar H-band observations obtained in September 2009 with the NIFS Integral Field Unit spectrometer on the Gemini-North telescope in Hawaii, previously reported by Irwin et al. (2011) [Icarus, 216, 141-158], and previously unreported Gemini/NIFS observations at lower spatial resolution made in 2011.

We find both similarities and differences between these observations, spaced over four years. The same overall cloud structure is seen with high, bright clouds visible at mid-latitudes (30-40°N,S), with slightly lower clouds observed at lower latitudes, together with small discrete clouds seen circling the pole at a latitude of approximately 60°S. However, while discrete clouds were visible at this latitude at both the main cloud deck level (at 2-3 bar) and in the upper troposphere (100-500 mb) in 2009, no distinct deep (2-3 bar), discrete circumpolar clouds were visible in 2013, although some deep clouds were seen at the southern edge of the main cloud belt at 30-40°S, which have not been observed before. The nature of the deep sub-polar discrete clouds observed in 2009 is intriguing. While it is possible that in 2013 these deeper clouds were masked by faster moving, overlying features, we consider that it is unlikely that this should have happened in 2013, but not in 2009 when the upper-cloud activity was generally similar. Meanwhile, the deep clouds seen at the southern edge of the main cloud belt at 30-40°S in 2013, should also have been detectable in 2009, but were not seen. Hence, these observations may have detected a real temporal variation in the occurrence of Neptune's deep clouds, pointing to underlying variability in the convective activity at the pressure of the main cloud deck at 2-3 bar near Neptune's south pole and also in the main observable cloud belt at 30-40°S. Title: First evidence of non-Gaussian solar flare EUV spectral line profiles and accelerated non-thermal ion motion Authors: Jeffrey, Natasha L. S.; Fletcher, Lyndsay; Labrosse, Nicolas Bibcode: 2016A&A...590A..99J Altcode: 2016arXiv160107308J Context. The properties of solar flare plasma can be determined from the observation of optically thin lines. The emitting ion distribution determines the shape of the spectral line profile, with an isothermal Maxwellian ion distribution producing a Gaussian profile. Non-Gaussian line profiles may indicate more complex ion distributions.
Aims: We investigate the possibility of determining flare-accelerated non-thermal ion and/or plasma velocity distributions.
Methods: We study EUV spectral lines produced during a flare SOL2013-05-15T01:45 using the Hinode EUV Imaging Spectrometer (EIS). The flare is located close to the eastern solar limb with an extended loop structure, allowing the different flare features: ribbons, hard X-ray (HXR) footpoints and the loop-top source to be clearly observed in UV, EUV and X-rays. EUV line spectroscopy is performed in seven different regions covering the flare. We study the line profiles of the isolated and unblended Fe XVI lines (λ262.9760 Å ) mainly formed at temperatures of ~2 to 4 MK. Suitable Fe XVI line profiles at one time close to the peak soft X-ray emission and free of directed mass motions are examined using: 1. a higher moments analysis, 2. Gaussian fitting, and 3. by fitting a kappa distribution line profile convolved with a Gaussian to account for the EIS instrumental profile.
Results: Fe XVI line profiles in the flaring loop-top, HXR footpoint and ribbon regions can be confidently fitted with a kappa line profile with an extra variable κ, giving low, non-thermal κ values between 2 and 3.3. An independent higher moments analysis also finds that many of the spectral line kurtosis values are higher than the Gaussian value of 3, even with the presence of a broad Gaussian instrumental profile.
Conclusions: A flare-accelerated non-thermal ion population could account for both the observed non-Gaussian line profiles, and for the Fe XVI "excess" broadening found from Gaussian fitting, if the emitting ions are interacting with a thermalised ~4 MK electron population, and the instrumental profile is well-approximated by a Gaussian profile. Title: Detection of H3+ auroral emission in Jupiter's 5-micron window Authors: Giles, R. S.; Fletcher, L. N.; Irwin, P. G. J.; Melin, H.; Stallard, T. S. Bibcode: 2016A&A...589A..67G Altcode: 2016arXiv160303646G We use high-resolution ground-based observations from the VLT CRIRES instrument in November 2012 to identify sixteen previously undetected H3+ emission lines from Jupiter's ionosphere. These emission lines are located in Jupiter's 5-micron window (4.5-5.2 μm), an optically-thin region of the planet's spectrum where the radiation mostly originates from the deep troposphere. The H3+ emission lines are so strong that they are visible even against this bright background. We measure the Doppler broadening of the H3+ emission lines in order to evaluate the kinetic temperature of the molecules, and we obtain a value of 1390 ± 160 K. We also measure the relative intensities of lines in the ν2 fundamental in order to calculate the rotational temperature, obtaining a value of 960 ± 40 K. Finally, we use the detection of an emission line from the 2ν2(2)-ν2 overtone to measure a vibrational temperature of 925 ± 25 K. We use these three independent temperature estimates to discuss the thermodynamic equilibrium of Jupiter's ionosphere. Title: Telling twins apart: exo-Earths and Venuses with transit spectroscopy Authors: Barstow, J. K.; Aigrain, S.; Irwin, P. G. J.; Kendrew, S.; Fletcher, L. N. Bibcode: 2016MNRAS.458.2657B Altcode: 2016arXiv160208277B; 2016MNRAS.tmp..271B The planned launch of the James Webb Space Telescope (JWST) in 2018 will herald a new era of exoplanet spectroscopy. JWST will be the first telescope sensitive enough to potentially characterize terrestrial planets from their transmission spectra. In this work, we explore the possibility that terrestrial planets with Venus-type and Earth-type atmospheres could be distinguished from each other using spectra obtained by JWST. If we find a terrestrial planet close to the liquid water habitable zone of an M5 star within a distance of 10 parsec, it would be possible to detect atmospheric ozone if present in large enough quantities, which would enable an oxygen-rich atmosphere to be identified. However, the cloudiness of a Venus-type atmosphere would inhibit our ability to draw firm conclusions about the atmospheric composition, making any result ambiguous. Observing small, temperate planets with JWST requires significant investment of resources, with single targets requiring of the order of 100 transits to achieve sufficient signal to noise. The possibility of detecting a crucial feature such as the ozone signature would need to be carefully weighed against the likelihood of clouds obscuring gas absorption in the spectrum. Title: Observations and Modelling of Helium Lines in Solar Flares Authors: Simões, P. J. A.; Fletcher, L.; Labrosse, N.; Kerr, G. S. Bibcode: 2016ASPC..504..197S Altcode: 2015arXiv151203477S We explore the response of the He <small>II</small> 304 Å and He <small>I</small> 584 Å line intensities to electron beam heating in solar flares using radiative hydrodynamic simulations. Comparing different electron beams parameters, we found that the intensities of both He lines are very sensitive to the energy flux deposited in the chromosphere, or more specifically to the heating rate, with He <font size=2>II 304 Å being more sensitive to the heating than He <small>I</small> 584 Å. Therefore, the He line ratio increases for larger heating rates in the chromosphere. A similar trend is found in observations, using SDO/EVE He irradiance ratios and estimates of the electron beam energy rate obtained from hard X-ray data. From the simulations, we also found that spectral index of the electrons can affect the He ratio but a similar effect was not found in the observations. Title: Division E Commission 10: Solar Activity Authors: Schrijver, Carolus J.; Fletcher, Lyndsay; van Driel-Gesztelyi, Lidia; Asai, Ayumi; Cally, Paul S.; Charbonneau, Paul; Gibson, Sarah E.; Gomez, Daniel; Hasan, Siraj S.; Veronig, Astrid M.; Yan, Yihua Bibcode: 2016IAUTA..29..245S Altcode: 2015arXiv151003348S After more than half a century of community support related to the science of ``solar activity'', IAU's Commission 10 was formally discontinued in 2015, to be succeeded by C.E2 with the same area of responsibility. On this occasion, we look back at the growth of the scientific disciplines involved around the world over almost a full century. Solar activity and fields of research looking into the related physics of the heliosphere continue to be vibrant and growing, with currently over 2,000 refereed publications appearing per year from over 4,000 unique authors, publishing in dozens of distinct journals and meeting in dozens of workshops and conferences each year. The size of the rapidly growing community and of the observational and computational data volumes, along with the multitude of connections into other branches of astrophysics, pose significant challenges; aspects of these challenges are beginning to be addressed through, among others, the development of new systems of literature reviews, machine-searchable archives for data and publications, and virtual observatories. As customary in these reports, we highlight some of the research topics that have seen particular interest over the most recent triennium, specifically active-region magnetic fields, coronal thermal structure, coronal seismology, flares and eruptions, and the variability of solar activity on long time scales. We close with a collection of developments, discoveries, and surprises that illustrate the range and dynamics of the discipline. Title: The Europa Imaging System (EIS): High-Resolution Imaging and Topography to Investigate Europa's Geology, Ice Shell, and Potential for Current Activity Authors: Turtle, E. P.; McEwen, A. S.; Collins, G. C.; Fletcher, L.; Hansen, C. J.; Hayes, A. G.; Hurford, T. A.; Kirk, R. L.; Barr Mlinar, A. C.; Nimmo, F.; Patterson, G. W.; Quick, L. C.; Soderblom, J. M.; Thomas, N.; Ernst, C. M. Bibcode: 2016LPI....47.1626T Altcode: Cameras to reveal / Europa's fractured landscapes / Ice shell mysteries. Title: Structures in the Outer Solar Atmosphere Authors: Fletcher, L.; Cargill, P. J.; Antiochos, S. K.; Gudiksen, B. V. Bibcode: 2016mssf.book..231F Altcode: No abstract at ADS Title: Spectral analysis of Uranus' 2014 bright storm with VLT/SINFONI Authors: Irwin, P. G. J.; Fletcher, L. N.; Read, P. L.; Tice, D.; de Pater, I.; Orton, G. S.; Teanby, N. A.; Davis, G. R. Bibcode: 2016Icar..264...72I Altcode: 2015arXiv151002274I An extremely bright storm system observed in Uranus' atmosphere by amateur observers in September 2014 triggered an international campaign to observe this feature with many telescopes across the world. Observations of the storm system in the near infrared were acquired in October and November 2014 with SINFONI on ESO's Very Large Telescope (VLT) in Chile. SINFONI is an Integral Field Unit spectrometer returning 64 × 64 pixel images with 2048 wavelengths and uses adaptive optics. Image cubes in the H-band (1.43-1.87 μm) were obtained at spatial resolutions of ∼ 0.1″ per pixel.

The observations show that the centre of the storm feature shifts markedly with increasing altitude, moving in the retrograde direction and slightly poleward with increasing altitude. We also see a faint 'tail' of more reflective material to the immediate south of the storm, which again trails in the retrograde direction. The observed spectra were analysed with the radiative transfer and retrieval code, NEMESIS (Irwin et al. [2008]. J. Quant. Spec. Radiat. Transfer, 109, 1136-1150). We find that the storm is well-modelled using either two main cloud layers of a 5-layer aerosol model based on Sromovsky et al. (Sromovsky et al. [2011]. Icarus, 215, 292-312) or by the simpler two-cloud-layer model of Tice et al. (Tice et al. [2013]. Icarus, 223, 684-698). The deep component appears to be due to a brightening (i.e. an increase in reflectivity) and increase in altitude of the main tropospheric cloud deck at 2-3 bars for both models, while the upper component of the feature was modelled as being due to either a thickening of the tropospheric haze of the 2-layer model or a vertical extension of the upper tropospheric cloud of the 5-layer model, assumed to be composed of methane ice and based at the methane condensation level of our assumed vertical temperature and abundance profile at 1.23 bar. We also found this methane ice cloud to be responsible for the faint 'tail' seen to the feature's south and the brighter polar 'hood' seen in all observations polewards of ∼45°N for the 5-layer model.

During the twelve days between our sets of observations the higher-altitude component of the feature was observed to have brightened significantly and extended to even higher altitudes, while the deeper component faded. Title: Electric Current Circuits in Astrophysics Authors: Kuijpers, Jan; Frey, Harald U.; Fletcher, Lyndsay Bibcode: 2016mssf.book....3K Altcode: No abstract at ADS Title: Properties of Discrete and Axisymmetric Features in Jupiter's Atmosphere from Observations of Thermal Emission: Recent Updates on the Eve of the Juno Mission Arrival at Jupiter Authors: Orton, G. S.; Fletcher, L. N.; Giles, R.; Sinclair, J.; Greathouse, T. K.; Momary, T.; Yanamandra-Fisher, P. A.; Fujiyoshi, T.; Fisher, B.; Payne, A.; Seede, R.; Simon, J.; Lai, M.; Nguyen, M.; Fernandez, J.; Baines, K. H. Bibcode: 2015AGUFM.P41B2067O Altcode: We have derived the spatial distribution and evolution of key properties of Jupiter's atmosphere through the analysis of imaging and spatially resolved spectroscopy of its thermal emission. These observations and their analysis represent a source of data we plan to acquire as a key component of support for the Juno mission's atmospheric investigation. From thermal imaging and spectroscopy in the 7-25 µm region, we can derive temperatures between 10 and 500 mbar atmospheric pressure, cloud opacities between 500 mbar and 5 bars, the para-H2 fraction near 300 mbar, the 100-400 mbar distributions of ammonia and phosphine, and the distribution of hydrocarbons in the stratosphere (~1 µbar - 10 mbar). Earlier work determined atmospheric properties of Jupiter's Great Red Spot (Fletcher et al. 2010, Icarus 208, 306) and the evolution of the South Equatorial Belt (SEB) fade (whitening) in 2009-2010 (Fletcher et al. 2011 Icarus, 213, 564). We will illustrate recent results from an examination of (1) the revival (re-darkening) of the SEB in 2010-2011, (2) discovery of uniquely dry regions of the atmosphere that are identified with visible "brown barges" typically located at the northern edge of Jupiter's North Equatorial Belt (NEB), (3) vertical structure of stratospheric waves constituting Jupiter's Quadrennial Oscillation (QQO) (Leovy et al. 1991, Nature 354, 380), and (4) previously unsuspected long-term tropospheric thermal waves uncovered in our multi-year program covering well over a Jovian year. Efforts are underway to provide mission-supporting observations using mid-infrared facility and guest instruments at several observatories during the 14-day orbits of the Juno mission, particularly - but not exclusively - the early orbits dedicated to remote sensing observations. Title: The Europa Imaging System (EIS): High-Resolution, 3-D Insight into Europa's Geology, Ice Shell, and Potential for Current Activity Authors: Turtle, E. P.; McEwen, A. S.; Collins, G. C.; Fletcher, L. N.; Hansen, C. J.; Hayes, A.; Hurford, T., Jr.; Kirk, R. L.; Barr, A.; Nimmo, F.; Patterson, G.; Quick, L. C.; Soderblom, J. M.; Thomas, N. Bibcode: 2015AGUFM.P13E..03T Altcode: The Europa Imaging System will transform our understanding of Europa through global decameter-scale coverage, three-dimensional maps, and unprecedented meter-scale imaging. EIS combines narrow-angle and wide-angle cameras (NAC and WAC) designed to address high-priority Europa science and reconnaissance goals. It will: (A) Characterize the ice shell by constraining its thickness and correlating surface features with subsurface structures detected by ice penetrating radar; (B) Constrain formation processes of surface features and the potential for current activity by characterizing endogenic structures, surface units, global cross-cutting relationships, and relationships to Europa's subsurface structure, and by searching for evidence of recent activity, including potential plumes; and (C) Characterize scientifically compelling landing sites and hazards by determining the nature of the surface at scales relevant to a potential lander. The NAC provides very high-resolution, stereo reconnaissance, generating 2-km-wide swaths at 0.5-m pixel scale from 50-km altitude, and uses a gimbal to enable independent targeting. NAC observations also include: near-global (>95%) mapping of Europa at ≤50-m pixel scale (to date, only ~14% of Europa has been imaged at ≤500 m/pixel, with best pixel scale 6 m); regional and high-resolution stereo imaging at <1-m/pixel; and high-phase-angle observations for plume searches. The WAC is designed to acquire pushbroom stereo swaths along flyby ground-tracks, generating digital topographic models with 32-m spatial scale and 4-m vertical precision from 50-km altitude. These data support characterization of cross-track clutter for radar sounding. The WAC also performs pushbroom color imaging with 6 broadband filters (350-1050 nm) to map surface units and correlations with geologic features and topography. EIS will provide comprehensive data sets essential to fulfilling the goal of exploring Europa to investigate its habitability and perform collaborative science with other investigations, including cartographic and geologic maps, regional and high-resolution digital topography, GIS products, color and photometric data products, a geodetic control network tied to radar altimetry, and a database of plume-search observations. Title: Preface Authors: Fletcher, L.; Heinzel, P.; van Driel-Gesztelyi, L.; Mandrini, C. H.; Fárník, F. Bibcode: 2015SoPh..290.3379F Altcode: 2015SoPh..tmp..168F No abstract at ADS Title: Impulsive Heating of Solar Flare Ribbons Above 10 MK Authors: Simões, P. J. A.; Graham, D. R.; Fletcher, L. Bibcode: 2015SoPh..290.3573S Altcode: 2015arXiv150503384S; 2015SoPh..tmp...62S The chromospheric response to the input of flare energy is marked by extended extreme ultraviolet (EUV) ribbons and hard X-ray (HXR) footpoints. These are usually explained as the result of heating and bremsstrahlung emission from accelerated electrons colliding in the dense chromospheric plasma. We present evidence of impulsive heating of flare ribbons above 10 MK in a two-ribbon flare. We analyse the impulsive phase of SOL2013-11-09T06:38, a C2.6 class event using data from Atmospheric Imaging Assembly (AIA) on board of the Solar Dynamics Observatory (SDO) and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) to derive the temperature, emission measure and differential emission measure of the flaring regions and investigate the evolution of the plasma in the flaring ribbons. The ribbons were visible at all SDO/AIA EUV/UV wavelengths, in particular, at 94 and 131 Å filters, sensitive to temperatures of 8 MK and 12 MK. The time evolution of the emission measure of the plasma above 10 MK at the ribbons has a peak near the HXR peak time. The presence of hot plasma in the lower atmosphere is further confirmed by a RHESSI imaging spectroscopy analysis, which shows resolved sources at 11 - 13 MK that are associated with at least one ribbon. We found that collisional beam-heating can only marginally explain the power necessary to heat the 10 MK plasma at the ribbons. Title: The EChO science case Authors: Tinetti, Giovanna; Drossart, Pierre; Eccleston, Paul; Hartogh, Paul; Isaak, Kate; Linder, Martin; Lovis, Christophe; Micela, Giusi; Ollivier, Marc; Puig, Ludovic; Ribas, Ignasi; Snellen, Ignas; Swinyard, Bruce; Allard, France; Barstow, Joanna; Cho, James; Coustenis, Athena; Cockell, Charles; Correia, Alexandre; Decin, Leen; de Kok, Remco; Deroo, Pieter; Encrenaz, Therese; Forget, Francois; Glasse, Alistair; Griffith, Caitlin; Guillot, Tristan; Koskinen, Tommi; Lammer, Helmut; Leconte, Jeremy; Maxted, Pierre; Mueller-Wodarg, Ingo; Nelson, Richard; North, Chris; Pallé, Enric; Pagano, Isabella; Piccioni, Guseppe; Pinfield, David; Selsis, Franck; Sozzetti, Alessandro; Stixrude, Lars; Tennyson, Jonathan; Turrini, Diego; Zapatero-Osorio, Mariarosa; Beaulieu, Jean-Philippe; Grodent, Denis; Guedel, Manuel; Luz, David; Nørgaard-Nielsen, Hans Ulrik; Ray, Tom; Rickman, Hans; Selig, Avri; Swain, Mark; Banaszkiewicz, Marek; Barlow, Mike; Bowles, Neil; Branduardi-Raymont, Graziella; du Foresto, Vincent Coudé; Gerard, Jean-Claude; Gizon, Laurent; Hornstrup, Allan; Jarchow, Christopher; Kerschbaum, Franz; Kovacs, Géza; Lagage, Pierre-Olivier; Lim, Tanya; Lopez-Morales, Mercedes; Malaguti, Giuseppe; Pace, Emanuele; Pascale, Enzo; Vandenbussche, Bart; Wright, Gillian; Ramos Zapata, Gonzalo; Adriani, Alberto; Azzollini, Ruymán; Balado, Ana; Bryson, Ian; Burston, Raymond; Colomé, Josep; Crook, Martin; Di Giorgio, Anna; Griffin, Matt; Hoogeveen, Ruud; Ottensamer, Roland; Irshad, Ranah; Middleton, Kevin; Morgante, Gianluca; Pinsard, Frederic; Rataj, Mirek; Reess, Jean-Michel; Savini, Giorgio; Schrader, Jan-Rutger; Stamper, Richard; Winter, Berend; Abe, L.; Abreu, M.; Achilleos, N.; Ade, P.; Adybekian, V.; Affer, L.; Agnor, C.; Agundez, M.; Alard, C.; Alcala, J.; Allende Prieto, C.; Alonso Floriano, F. J.; Altieri, F.; Alvarez Iglesias, C. A.; Amado, P.; Andersen, A.; Aylward, A.; Baffa, C.; Bakos, G.; Ballerini, P.; Banaszkiewicz, M.; Barber, R. J.; Barrado, D.; Barton, E. J.; Batista, V.; Bellucci, G.; Belmonte Avilés, J. A.; Berry, D.; Bézard, B.; Biondi, D.; Błęcka, M.; Boisse, I.; Bonfond, B.; Bordé, P.; Börner, P.; Bouy, H.; Brown, L.; Buchhave, L.; Budaj, J.; Bulgarelli, A.; Burleigh, M.; Cabral, A.; Capria, M. T.; Cassan, A.; Cavarroc, C.; Cecchi-Pestellini, C.; Cerulli, R.; Chadney, J.; Chamberlain, S.; Charnoz, S.; Christian Jessen, N.; Ciaravella, A.; Claret, A.; Claudi, R.; Coates, A.; Cole, R.; Collura, A.; Cordier, D.; Covino, E.; Danielski, C.; Damasso, M.; Deeg, H. J.; Delgado-Mena, E.; Del Vecchio, C.; Demangeon, O.; De Sio, A.; De Wit, J.; Dobrijévic, M.; Doel, P.; Dominic, C.; Dorfi, E.; Eales, S.; Eiroa, C.; Espinoza Contreras, M.; Esposito, M.; Eymet, V.; Fabrizio, N.; Fernández, M.; Femenía Castella, B.; Figueira, P.; Filacchione, G.; Fletcher, L.; Focardi, M.; Fossey, S.; Fouqué, P.; Frith, J.; Galand, M.; Gambicorti, L.; Gaulme, P.; García López, R. J.; Garcia-Piquer, A.; Gear, W.; Gerard, J. -C.; Gesa, L.; Giani, E.; Gianotti, F.; Gillon, M.; Giro, E.; Giuranna, M.; Gomez, H.; Gomez-Leal, I.; Gonzalez Hernandez, J.; González Merino, B.; Graczyk, R.; Grassi, D.; Guardia, J.; Guio, P.; Gustin, J.; Hargrave, P.; Haigh, J.; Hébrard, E.; Heiter, U.; Heredero, R. L.; Herrero, E.; Hersant, F.; Heyrovsky, D.; Hollis, M.; Hubert, B.; Hueso, R.; Israelian, G.; Iro, N.; Irwin, P.; Jacquemoud, S.; Jones, G.; Jones, H.; Justtanont, K.; Kehoe, T.; Kerschbaum, F.; Kerins, E.; Kervella, P.; Kipping, D.; Koskinen, T.; Krupp, N.; Lahav, O.; Laken, B.; Lanza, N.; Lellouch, E.; Leto, G.; Licandro Goldaracena, J.; Lithgow-Bertelloni, C.; Liu, S. J.; Lo Cicero, U.; Lodieu, N.; Lognonné, P.; Lopez-Puertas, M.; Lopez-Valverde, M. A.; Lundgaard Rasmussen, I.; Luntzer, A.; Machado, P.; MacTavish, C.; Maggio, A.; Maillard, J. -P.; Magnes, W.; Maldonado, J.; Mall, U.; Marquette, J. -B.; Mauskopf, P.; Massi, F.; Maurin, A. -S.; Medvedev, A.; Michaut, C.; Miles-Paez, P.; Montalto, M.; Montañés Rodríguez, P.; Monteiro, M.; Montes, D.; Morais, H.; Morales, J. C.; Morales-Calderón, M.; Morello, G.; Moro Martín, A.; Moses, J.; Moya Bedon, A.; Murgas Alcaino, F.; Oliva, E.; Orton, G.; Palla, F.; Pancrazzi, M.; Pantin, E.; Parmentier, V.; Parviainen, H.; Peña Ramírez, K. Y.; Peralta, J.; Perez-Hoyos, S.; Petrov, R.; Pezzuto, S.; Pietrzak, R.; Pilat-Lohinger, E.; Piskunov, N.; Prinja, R.; Prisinzano, L.; Polichtchouk, I.; Poretti, E.; Radioti, A.; Ramos, A. A.; Rank-Lüftinger, T.; Read, P.; Readorn, K.; Rebolo López, R.; Rebordão, J.; Rengel, M.; Rezac, L.; Rocchetto, M.; Rodler, F.; Sánchez Béjar, V. J.; Sanchez Lavega, A.; Sanromá, E.; Santos, N.; Sanz Forcada, J.; Scandariato, G.; Schmider, F. -X.; Scholz, A.; Scuderi, S.; Sethenadh, J.; Shore, S.; Showman, A.; Sicardy, B.; Sitek, P.; Smith, A.; Soret, L.; Sousa, S.; Stiepen, A.; Stolarski, M.; Strazzulla, G.; Tabernero, H. M.; Tanga, P.; Tecsa, M.; Temple, J.; Terenzi, L.; Tessenyi, M.; Testi, L.; Thompson, S.; Thrastarson, H.; Tingley, B. W.; Trifoglio, M.; Martín Torres, J.; Tozzi, A.; Turrini, D.; Varley, R.; Vakili, F.; de Val-Borro, M.; Valdivieso, M. L.; Venot, O.; Villaver, E.; Vinatier, S.; Viti, S.; Waldmann, I.; Waltham, D.; Ward-Thompson, D.; Waters, R.; Watkins, C.; Watson, D.; Wawer, P.; Wawrzaszk, A.; White, G.; Widemann, T.; Winek, W.; Wiśniowski, T.; Yelle, R.; Yung, Y.; Yurchenko, S. N. Bibcode: 2015ExA....40..329T Altcode: 2015ExA...tmp...67T; 2015arXiv150205747T The discovery of almost two thousand exoplanets has revealed an unexpectedly diverse planet population. We see gas giants in few-day orbits, whole multi-planet systems within the orbit of Mercury, and new populations of planets with masses between that of the Earth and Neptune—all unknown in the Solar System. Observations to date have shown that our Solar System is certainly not representative of the general population of planets in our Milky Way. The key science questions that urgently need addressing are therefore: What are exoplanets made of? Why are planets as they are? How do planetary systems work and what causes the exceptional diversity observed as compared to the Solar System? The EChO (Exoplanet Characterisation Observatory) space mission was conceived to take up the challenge to explain this diversity in terms of formation, evolution, internal structure and planet and atmospheric composition. This requires in-depth spectroscopic knowledge of the atmospheres of a large and well-defined planet sample for which precise physical, chemical and dynamical information can be obtained. In order to fulfil this ambitious scientific program, EChO was designed as a dedicated survey mission for transit and eclipse spectroscopy capable of observing a large, diverse and well-defined planet sample within its 4-year mission lifetime. The transit and eclipse spectroscopy method, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allows us to measure atmospheric signals from the planet at levels of at least 10-4 relative to the star. This can only be achieved in conjunction with a carefully designed stable payload and satellite platform. It is also necessary to provide broad instantaneous wavelength coverage to detect as many molecular species as possible, to probe the thermal structure of the planetary atmospheres and to correct for the contaminating effects of the stellar photosphere. This requires wavelength coverage of at least 0.55 to 11 μm with a goal of covering from 0.4 to 16 μm. Only modest spectral resolving power is needed, with R ~ 300 for wavelengths less than 5 μm and R ~ 30 for wavelengths greater than this. The transit spectroscopy technique means that no spatial resolution is required. A telescope collecting area of about 1 m2 is sufficiently large to achieve the necessary spectro-photometric precision: for the Phase A study a 1.13 m2 telescope, diffraction limited at 3 μm has been adopted. Placing the satellite at L2 provides a cold and stable thermal environment as well as a large field of regard to allow efficient time-critical observation of targets randomly distributed over the sky. EChO has been conceived to achieve a single goal: exoplanet spectroscopy. The spectral coverage and signal-to-noise to be achieved by EChO, thanks to its high stability and dedicated design, would be a game changer by allowing atmospheric composition to be measured with unparalleled exactness: at least a factor 10 more precise and a factor 10 to 1000 more accurate than current observations. This would enable the detection of molecular abundances three orders of magnitude lower than currently possible and a fourfold increase from the handful of molecules detected to date. Combining these data with estimates of planetary bulk compositions from accurate measurements of their radii and masses would allow degeneracies associated with planetary interior modelling to be broken, giving unique insight into the interior structure and elemental abundances of these alien worlds. EChO would allow scientists to study exoplanets both as a population and as individuals. The mission can target super-Earths, Neptune-like, and Jupiter-like planets, in the very hot to temperate zones (planet temperatures of 300-3000 K) of F to M-type host stars. The EChO core science would be delivered by a three-tier survey. The EChO Chemical Census: This is a broad survey of a few-hundred exoplanets, which allows us to explore the spectroscopic and chemical diversity of the exoplanet population as a whole. The EChO Origin: This is a deep survey of a subsample of tens of exoplanets for which significantly higher signal to noise and spectral resolution spectra can be obtained to explain the origin of the exoplanet diversity (such as formation mechanisms, chemical processes, atmospheric escape). The EChO Rosetta Stones: This is an ultra-high accuracy survey targeting a subsample of select exoplanets. These will be the bright "benchmark" cases for which a large number of measurements would be taken to explore temporal variations, and to obtain two and three dimensional spatial information on the atmospheric conditions through eclipse-mapping techniques. If EChO were launched today, the exoplanets currently observed are sufficient to provide a large and diverse sample. The Chemical Census survey would consist of > 160 exoplanets with a range of planetary sizes, temperatures, orbital parameters and stellar host properties. Additionally, over the next 10 years, several new ground- and space-based transit photometric surveys and missions will come on-line (e.g. NGTS, CHEOPS, TESS, PLATO), which will specifically focus on finding bright, nearby systems. The current rapid rate of discovery would allow the target list to be further optimised in the years prior to EChO's launch and enable the atmospheric characterisation of hundreds of planets. Title: Determining energy balance in the flaring chromosphere from oxygen V line ratios Authors: Graham, D. R.; Fletcher, L.; Labrosse, N. Bibcode: 2015A&A...584A...6G Altcode: 2014arXiv1411.4603G Context. The impulsive phase of solar flares is a time of rapid energy deposition and heating in the lower solar atmosphere, leading to changes in the temperature and density structure of the region.
Aims: We use an O v density diagnostic formed from the λ192 /λ248 line ratio, provided by the Hinode/EIS instrument, to determine the density of flare footpoint plasma at O v formation temperatures of ~2.5 × 105 K, giving a constraint on the properties of the heated transition region.
Methods: Hinode/EIS rasters from 2 small flare events in December 2007 were used. Raster images were co-aligned to identify and establish the footpoint pixels, multiple-component Gaussian line fitting of the spectra was carried out to isolate the density diagnostic pair, and the density was calculated for several footpoint areas. The assumptions of equilibrium ionisation and optically-thin radiation for the O v lines used were assessed and found to be acceptable. For one of the events, properties of the electron distribution were deduced from earlier RHESSI hard X-ray observations. These were used to calculate the plasma heating rate delivered by an electron beam for 2 semi-empirical atmospheres under collisional thick-target assumptions. The radiative loss rate for this plasma was also calculated for comparison with possible energy input mechanisms.
Results: Electron number densities of up to 1011.9 cm-3 were measured during the flare impulsive phase using the O v λ192 /λ248 diagnostic ratio. The heating rate delivered by an electron beam was found to exceed the radiative losses at this density, corresponding to a height of 450 km, and when assuming a completely ionised target atmosphere far exceed the losses but at a height of 1450-1600 km. A chromospheric thickness of 70-700 km was found to be required to balance a conductive input to the O v-emitting region with radiative losses.
Conclusions: Electron densities have been observed in footpoint sources at transition region temperatures, comparable to previous results but with improved spatial information. The observed densities can be explained by heating of the chromosphere by collisional electrons, with O v formed at heights of 450-1600 km above the photosphere, depending on the atmospheric ionisation fraction. Title: Photochemistry in Saturn's Ring-Shadowed Atmosphere: Modulation of Hydrocarbons and Observations of Dust Content Authors: Edgington, S. G.; Atreya, S. K.; Wilson, E. H.; Baines, K. H.; West, R. A.; Bjoraker, G. L.; Fletcher, L. N.; Momary, T. Bibcode: 2015AGUFM.P41B2056E Altcode: Cassini has been orbiting Saturn for over eleven years now. During this epoch, the ring shadow has moved from covering much of the northern hemisphere (the solar inclination was 24 degrees) to covering a large swath south of the equator and it continues to move southward. At Saturn Orbit Insertion in 2004, the projection of the A-ring onto Saturn reached as far as 40N along the central meridian (52N at the terminator). At its maximum extent, the ring shadow can reach as far as 48N/S (58N/S at the terminator). The net effect is that the intensity of both ultraviolet and visible sunlight penetrating through the rings to any particular latitude will vary depending on both Saturn's axis relative to the Sun and the optical thickness of each ring system. In essence, the rings act like semi-transparent venetian blinds. Our previous work examined the variation of the solar flux as a function of solar inclination, i.e. for each 7.25-year season at Saturn. Here, we report on the impact of the oscillating ring shadow on the photolysis and production rates of hydrocarbons (acetylene, ethane, propane, and benzene) and phosphine in Saturn's stratosphere and upper troposphere. The impact of these production and loss rates on the abundance of long-lived photochemical products leading to haze formation are explored. Similarly, we assess their impact on phosphine abundance, a disequilibrium species whose presence in the upper troposphere can be used as a tracer of convective processes in the deeper atmosphere. We will also present our ongoing analysis of Cassini's CIRS, UVIS, and VIMS datasets that provide an estimate of the evolving haze content of the northern hemisphere and we will begin to assess the implications for dynamical mixing. In particular, we will examine how the now famous hexagonal jet stream acts like a barrier to transport, isolating Saturn's north polar region from outside transport of photochemically-generated molecules and haze. The research described in this paper was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Copyright 2015 California Institute of Technology. Government sponsorship is acknowledged. Title: The Long wave (11-16 μm) spectrograph for the EChO M3 Mission Candidate study Authors: Bowles, N. E.; Tecza, M.; Barstow, J. K.; Temple, J. M.; Irwin, P. G. J.; Fletcher, L. N.; Calcutt, S.; Hurley, J.; Ferlet, M.; Freeman, D. Bibcode: 2015ExA....40..801B Altcode: 2015ExA...tmp...58B The results for the design study of the Long Wave Infrared Module (LWIR), a goal spectroscopic channel for the EChO ESA medium class candidate mission, are presented. The requirements for the LWIR module were to provide coverage of the 11-16 μm spectral range at a moderate resolving power of at least R = 30, whilst minimising noise contributions above photon due to the thermal background of the EChO instrument and telescope, and astrophysical sources such as the zodiacal light. The study output module design is a KRS-6 prism spectrograph with aluminium mirror beam expander and coated germanium lenses for the final focusing elements. Thermal background considerations led to enclosing the beam in a baffle cooled to approximately 25-29 K. To minimise diffuse astrophysical background contributions due to the zodiacal light, anamorphic designs were considered in addition to the elliptical input beam provided by the EChO telescope. Given the requirement that measurements in this waveband place on the performance of the infrared detector array, an additional study on the likely scientific return with lower resolving power ( R < 30) is included. If specific high priority molecules on moderately warm giant planets (e.g. CO2, H2O) are targeted, the LWIR channel can still provide improvements in determining the atmospheric temperature structure and molecular abundances. Thus, the inclusion of even a coarse-resolution (R≈10) LWIR module would still make an important contribution to measurements of exoplanet atmospheres made by EChO. Title: Soft X-Ray Pulsations in Solar Flares Authors: Simões, P. J. A.; Hudson, H. S.; Fletcher, L. Bibcode: 2015SoPh..290.3625S Altcode: 2014arXiv1412.3045S; 2015SoPh..tmp...50S The soft X-ray emissions (hν>1.5 keV) of solar flares mainly come from the bright coronal loops at the highest temperatures normally achieved in the flare process. Their ubiquity has led to their use as a standard measure of flare occurrence and energy, although the overwhelming bulk of the total flare energy goes elsewhere. Recently Dolla et al. (Astrophys. J. Lett.749, L16, 2012) noted quasi-periodic pulsations (QPP) in the soft X-ray signature of the X-class flare SOL2011-02-15, as observed by the standard photometric data from the GOES (Geostationary Operational Environmental Satellite) spacecraft. In this article we analyse the suitability of the GOES data for this type of analysis and find them to be generally valuable after September, 2010 (GOES-15). We then extend the result of Dolla et al. to a complete list of X-class flares from Cycle 24 and show that most of them (80 %) display QPPs in the impulsive phase. The pulsations show up cleanly in both channels of the GOES data, making use of time-series of irradiance differences (the digital time derivative on the 2-s sampling). We deploy different techniques to characterise the periodicity of GOES pulsations, considering the red-noise properties of the flare signals, finding a range of characteristic time scales of the QPPs for each event, but usually with no strong signature of a single period dominating in the power spectrum. The QPP may also appear on somewhat longer time scales during the later gradual phase, possibly with a greater tendency towards coherence, but the sampling noise in GOES difference data for high irradiance values (X-class flares) makes these more uncertain. We show that there is minimal phase difference between the differenced GOES energy channels, or between them and the hard X-ray variations on short time scales. During the impulsive phase, the footpoints of the newly forming flare loops may also contribute to the observed soft X-ray variations. Title: Hα Line Profile Asymmetries and the Chromospheric Flare Velocity Field Authors: Kuridze, D.; Mathioudakis, M.; Simões, P. J. A.; Rouppe van der Voort, L.; Carlsson, M.; Jafarzadeh, S.; Allred, J. C.; Kowalski, A. F.; Kennedy, M.; Fletcher, L.; Graham, D.; Keenan, F. P. Bibcode: 2015ApJ...813..125K Altcode: 2015arXiv151001877K The asymmetries observed in the line profiles of solar flares can provide important diagnostics of the properties and dynamics of the flaring atmosphere. In this paper the evolution of the Hα and Ca ii λ8542 lines are studied using high spatial, temporal, and spectral resolution ground-based observations of an M1.1 flare obtained with the Swedish 1 m Solar Telescope. The temporal evolution of the Hα line profiles from the flare kernel shows excess emission in the red wing (red asymmetry) before flare maximum and excess in the blue wing (blue asymmetry) after maximum. However, the Ca ii λ8542 line does not follow the same pattern, showing only a weak red asymmetry during the flare. RADYN simulations are used to synthesize spectral line profiles for the flaring atmosphere, and good agreement is found with the observations. We show that the red asymmetry observed in Hα is not necessarily associated with plasma downflows, and the blue asymmetry may not be related to plasma upflows. Indeed, we conclude that the steep velocity gradients in the flaring chromosphere modify the wavelength of the central reversal in the Hα line profile. The shift in the wavelength of maximum opacity to shorter and longer wavelengths generates the red and blue asymmetries, respectively. Title: Photochemistry in Saturn's Ring-Shadowed Atmosphere: Hydrocarbon Modulation & Observations of Dust Content Authors: Edgington, S. G.; Atreya, S. K.; Wilson, E. H.; West, R. A.; Bjoraker, G. L.; Fletcher, L. N.; Baines, K. H.; Momary, T. Bibcode: 2015EPSC...10..399E Altcode: Cassini has been orbiting Saturn for eleven years. During this epoch, the ring shadow has moved from covering a relatively large portion of the northern hemisphere (Figure 1) to covering a large swath south of the equator and continues to move southward. At Saturn Orbit Insertion on July 1, 2004, the ring plane was inclined by ~24 degrees relative to the Sun -Saturn vector. At this time, the projection of the B-ring onto Saturn reached as far as 40ºN along the central meridian (~52ºN at the terminator). At its maximum extent, the ring shadow can reach as far as 48ºN (~58ºN at the terminator). The net effect is that the intensity of both ultraviolet and visible sunlight penetrating into any particular latitude will vary depending on both Saturn's axis relative to the Sun and the optical thickness of each ring system. In essence, the rings act like venetian blinds. Title: A solar tornado observed by EIS. Plasma diagnostics Authors: Levens, P. J.; Labrosse, N.; Fletcher, L.; Schmieder, B. Bibcode: 2015A&A...582A..27L Altcode: 2015arXiv150801377L Context. The term "solar tornadoes" has been used to describe apparently rotating magnetic structures above the solar limb, as seen in high resolution images and movies from the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO). These often form part of the larger magnetic structure of a prominence, however the links between them remain unclear. Here we present plasma diagnostics on a tornado-like structure and its surroundings, seen above the limb by the Extreme-ultraviolet Imaging Spectrometer (EIS) aboard the Hinode satellite.
Aims: We aim to extend our view of the velocity patterns seen in tornado-like structures with EIS to a wider range of temperatures and to use density diagnostics, non-thermal line widths, and differential emission measures to provide insight into the physical characteristics of the plasma.
Methods: Using Gaussian fitting to fit and de-blend the spectral lines seen by EIS, we calculated line-of-sight velocities and non-thermal line widths. Along with information from the CHIANTI database, we used line intensity ratios to calculate electron densities at each pixel. Using a regularised inversion code we also calculated the differential emission measure (DEM) at different locations in the prominence.
Results: The split Doppler-shift pattern is found to be visible down to a temperature of around log T = 6.0. At temperatures lower than this, the pattern is unclear in this data set. We obtain an electron density of log ne = 8.5 when looking towards the centre of the tornado structure at a plasma temperature of log T = 6.2, as compared to the surroundings of the tornado structure where we find log ne to be nearer 9. Non-thermal line widths show broader profiles at the tornado location when compared to the surrounding corona. We discuss the differential emission measure in both the tornado and the prominence body, which suggests that there is more contribution in the tornado at temperatures below log T = 6.0 than in the prominence.

A movie is available in electronic form at http://www.aanda.org Title: IRIS observations of the Mg ii h and k lines during a solar flare Authors: Kerr, G. S.; Simões, P. J. A.; Qiu, J.; Fletcher, L. Bibcode: 2015A&A...582A..50K Altcode: 2015arXiv150803813K The bulk of the radiative output of a solar flare is emitted from the chromosphere, which produces enhancements in the optical and UV continuum, and in many lines, both optically thick and thin. We have, until very recently, lacked observations of two of the strongest of these lines: the Mg ii h and k resonance lines. We present a detailed study of the response of these lines to a solar flare. The spatial and temporal behaviour of the integrated intensities, k/h line ratios, line of sight velocities, line widths and line asymmetries were investigated during an M class flare (SOL2014-02-13T01:40). Very intense, spatially localised energy input at the outer edge of the ribbon is observed, resulting in redshifts equivalent to velocities of ~15-26 km s-1, line broadenings, and a blue asymmetry in the most intense sources. The characteristic central reversal feature that is ubiquitous in quiet Sun observations is absent in flaring profiles, indicating that the source function increases with height during the flare. Despite the absence of the central reversal feature, the k/h line ratio indicates that the lines remain optically thick during the flare. Subordinate lines in the Mg ii passband are observed to be in emission in flaring sources, brightening and cooling with similar timescales to the resonance lines. This work represents a first analysis of potential diagnostic information of the flaring atmosphere using these lines, and provides observations to which synthetic spectra from advanced radiative transfer codes can be compared. Title: Observations of Jupiter at 5 micron from IRTF/TEXES : latitudinal variability of disequilibrium species Authors: Drossart, P.; Encrenaz, T.; Greathouse, T. K.; DeWitt, C.; Fouchet, T.; Janssen, M.; Gulkis, S.; Orton, G. S.; Fletcher, L.; Giles, R.; Atreya, S. K.; Boudon, V. Bibcode: 2015EPSC...10..194D Altcode: Observations of Jupiter in the 5 μm spectral window,obtained in March/April 2015 at IRTF are presented, in preparation of the arrival of the NASA/JUNO mission in 2016. Sounding of the troposphere of Jupiter below 2 bars is obtained from the observations, to search for the variability of disequilibrium species, related to deep atmospheric circulation. Title: Stratospheric temperature and composition of Jupiter's polar aurora from IRTF-TEXES Authors: Sinclair, J.; Orton, G. S.; Greathouse, T. K.; Fletcher, L. N.; Irwin, P. G. J. Bibcode: 2015EPSC...10..374S Altcode: We perform an analysis of TEXES (Texas Echelon Cross Echelle Spectrograph, 5- to 25- μm,[1]) spectra of Jupiter's high latitudes observed in December 2014 in order to study the jovian polar aurora. The high resolving power (R∼85000) of TEXES allows a large altitude range (10 mbar to 0.01 mbar) in Jupiter's stratosphere to be sounded. Retrievals of temperature and stratospheric composition of these measurements therefore: 1) allow the vertical deposition of auroral energy to be determined and 2) quantify how the auro-ral processes modify the thermal structure and composition of the jovian stratosphere. Title: JUICE: A European Mission to Jupiter and its Icy Moons Authors: Witasse, O.; Altobelli, N.; Barabash, S.; Bruzzone, L.; Dougherty, M.; Erd, C.; Fletcher, L.; Gladstone, R.; Grasset, O.; Gurvits, L.; Hartogh, P.; Hussmann, H.; Iess, I.; Langevin, Y.; Palumbo, P.; Piccioni, G.; Sarri, G.; Titov, D.; Wahlund, J. -E. Bibcode: 2015EPSC...10..564W Altcode: JUICE -JUpiter ICy moons Explorer -is the first large mission in the ESA Cosmic Vision 2015-2025 programme[1]. The mission was selected in May 2012 and adopted in November 2014. The implementation phase starts in July 2015, following the selection of the prime industrial contractor. Planned for launch in June 2022 and arrival at Jupiter in October 2029, it will spend at least three years making detailed observations of Jupiter and three of its largest moons, Ganymede, Callisto and Europa. Title: A unified view of coronal loop contraction and oscillation in flares Authors: Russell, A. J. B.; Simões, P. J. A.; Fletcher, L. Bibcode: 2015A&A...581A...8R Altcode: 2015arXiv150607716R Context. Transverse loop oscillations and loop contractions are commonly associated with solar flares, but the two types of motion have traditionally been regarded as separate phenomena.
Aims: We present an observation of coronal loops that contract and oscillate following the onset of a flare. We aim to explain why both behaviours are seen together and why only some of the loops oscillate.
Methods: A time sequence of SDO/AIA 171 Å images is analysed to identify the positions of coronal loops following the onset of the M6.4 flare SOL2012-03-09T03:53. We focus on five loops in particular, all of which contract during the flare, with three of them oscillating as well. A simple model is then developed for the contraction and oscillation of a coronal loop.
Results: We propose that coronal loop contractions and oscillations can occur in a single response to removal of magnetic energy from the corona. Our model reproduces the various types of loop motion observed and explains why the highest loops oscillate during their contraction, while no oscillation is detected for the shortest contracting loops. The proposed framework suggests that loop motions can be used as a diagnostic for the removal of coronal magnetic energy by flares, while rapid decrease in coronal magnetic energy is a newly identified excitation mechanism for transverse loop oscillations.

Appendices are available in electronic form at http://www.aanda.org Title: Cloud structure and composition of Jupiter's troposphere from 5- μ m Cassini VIMS spectroscopy Authors: Giles, R. S.; Fletcher, L. N.; Irwin, P. G. J. Bibcode: 2015Icar..257..457G Altcode: 2015arXiv150601608G Jupiter's tropospheric composition and cloud structure are studied using Cassini VIMS 4.5-5.1 μ m thermal emission spectra from the 2000-2001 flyby. We make use of both nadir and limb darkening observations on the planet's nightside, and compare these with dayside observations. Although there is significant spatial variability in the 5- μ m brightness temperatures, the shape of the spectra remain very similar across the planet, suggesting the presence of a spectrally-flat, spatially inhomogeneous cloud deck. We find that a simple cloud model consisting of a single, compact cloud is able to reproduce both nightside and dayside spectra, subject to the following constraints: (i) the cloud base is located at pressures of 1.2 bar or lower; (ii) the cloud particles are highly scattering; and (iii) the cloud is sufficiently spectrally flat. Using this cloud model, we search for global variability in the cloud opacity and the phosphine deep volume mixing ratio. We find that the vast majority of the 5- μ m inhomogeneity can be accounted for by variations in the thickness of the cloud decks, with huge differences between the cloudy zones and the relatively cloud-free belts. The relatively low spectral resolution of VIMS limits reliable retrievals of gaseous species, but some evidence is found for an enhancement in the abundance of phosphine at high latitudes. Title: Photochemical response to the variation of temperature in the 2011-2012 stratospheric vortex of Saturn Authors: Cavalié, T.; Dobrijevic, M.; Fletcher, L. N.; Loison, J. -C.; Hickson, K. M.; Hue, V.; Hartogh, P. Bibcode: 2015A&A...580A..55C Altcode: Context. A hot vortex formed in the stratosphere of Saturn following the 2010-2011 Northern Storm. Huge temperature increases have been measured in the vortex around the millibar level. Enhancements in hydrocarbon abundances have been observed at the millibar level in 2011-2012 inside this vortex.
Aims: We model the time-dependent photochemistry inside the vortex by accounting for the temperature variability over the period from January 2011 to March 2012 to assess whether photochemistry alone can explain the enhancements seen in the hydrocarbon abundances.
Methods: We used a 1D time-dependent photochemical model of Saturn and adapted it to the perturbed conditions of the vortex after validating it in quiescent conditions.
Results: Our model predicts non-variability for ethane (C2H6) and acetylene (C2H2) and an increase in ethylene (C2H4) by a factor of 3 in the mbar region. Heavier hydrocarbons show a stronger variability than the lighter ones. We are unable to reproduce the increase seen in C2H2 , and we significantly underestimate the increase seen in C2H4.
Conclusions: Pure photochemistry does not explain the variability seen in the abundance of most hydrocarbons. This means that dynamics (eddy diffusion and/or advection) must have played a significant role in shaping the vertical profiles of the main hydrocarbons. Title: Erratum: Transit spectroscopy with JWST: systematics, star-spots and stitching Authors: Barstow, J. K.; Aigrain, S.; Irwin, P. G. J.; Kendrew, S.; Fletcher, L. N. Bibcode: 2015MNRAS.451.1306B Altcode: No abstract at ADS Title: Division II: Commission 10: Solar Activity Authors: van Driel-Gesztelyi, Lidia; Scrijver, Karel J.; Klimchuk, James A.; Charbonneau, Paul; Fletcher, Lyndsay; Hasan, S. Sirajul; Hudson, Hugh S.; Kusano, Kanya; Mandrini, Cristina H.; Peter, Hardi; Vršnak, Bojan; Yan, Yihua Bibcode: 2015IAUTB..28..106V Altcode: The Business Meeting of Commission 10 was held as part of the Business Meeting of Division II (Sun and Heliosphere), chaired by Valentin Martínez-Pillet, the President of the Division. The President of Commission 10 (C10; Solar activity), Lidia van Driel-Gesztelyi, took the chair for the business meeting of C10. She summarised the activities of C10 over the triennium and the election of the incoming OC. Title: Solar Flares and the Chromosphere Authors: Fletcher, Lyndsay Bibcode: 2015IAUGA..2286134F Altcode: During a solar flare, the chromosphere emits across a large fraction of the electromagnetic spectrum, providing diagnostic information on heating, dynamics and flare energy transport by both thermal and non-thermal means. The evolution of chromospheric ribbons and footpoints also traces the progress of coronal reconnection, and links radiation output with magnetic evolution. Since the chromosphere emits the majority of a flare's radiation, the current emphasis on chromospheric observations by missions such as IRIS, and future large facilities such as the DKIST, is very beneficial to flare research. In this talk I will overview recent developments in observations and theory of flaring chromospheres and make some suggestions about profitable future avenues for research. Title: Meandering Shallow Atmospheric Jet as a Model of Saturn's North-polar Hexagon Authors: Morales-Juberías, R.; Sayanagi, K. M.; Simon, A. A.; Fletcher, L. N.; Cosentino, R. G. Bibcode: 2015ApJ...806L..18M Altcode: The Voyager flybys of Saturn in 1980-1981 revealed a circumpolar Hexagon at ∼78° north planetographic latitude that has persisted for over 30 Earth years, more than one Saturn year, and has been observed by ground-based telescopes, Hubble Space Telescope and multiple instruments on board the Cassini orbiter. Its average phase speed is very slow with respect to the System III rotation rate, defined by the primary periodicity in the Saturn Kilometric Radiation during the Voyager era. Cloud tracking wind measurements reveal the presence of a prograde jet-stream whose path traces the Hexagon’s shape. Previous numerical models have produced large-amplitude, n = 6, wavy structures with westward intrinsic phase propagation (relative to the jet). However, the observed net phase speed has proven to be more difficult to achieve. Here we present numerical simulations showing that instabilities in shallow jets can equilibrate as meanders closely resembling the observed morphology and phase speed of Saturn’s northern Hexagon. We also find that the winds at the bottom of the model are as important as the winds at the cloud level in matching the observed Hexagon’s characteristics. Title: Structures in the Outer Solar Atmosphere Authors: Fletcher, L.; Cargill, P. J.; Antiochos, S. K.; Gudiksen, B. V. Bibcode: 2015SSRv..188..211F Altcode: 2014SSRv..tmp...52F; 2014arXiv1412.7378F The structure and dynamics of the outer solar atmosphere are reviewed with emphasis on the role played by the magnetic field. Contemporary observations that focus on high resolution imaging over a range of temperatures, as well as UV, EUV and hard X-ray spectroscopy, demonstrate the presence of a vast range of temporal and spatial scales, mass motions, and particle energies present. By focusing on recent developments in the chromosphere, corona and solar wind, it is shown that small scale processes, in particular magnetic reconnection, play a central role in determining the large-scale structure and properties of all regions. This coupling of scales is central to understanding the atmosphere, yet poses formidable challenges for theoretical models. Title: VizieR Online Data Catalog: Bayesian method for detecting stellar flares (Pitkin+, 2014) Authors: Pitkin, M.; Williams, D.; Fletcher, L.; Grant, S. D. T. Bibcode: 2015yCat..74452268P Altcode: We present a Bayesian-odds-ratio-based algorithm for detecting stellar flares in light-curve data. We assume flares are described by a model in which there is a rapid rise with a half-Gaussian profile, followed by an exponential decay. Our signal model also contains a polynomial background model required to fit underlying light-curve variations in the data, which could otherwise partially mimic a flare. We characterize the false alarm probability and efficiency of this method under the assumption that any unmodelled noise in the data is Gaussian, and compare it with a simpler thresholding method based on that used in Walkowicz et al. We find our method has a significant increase in detection efficiency for low signal-to-noise ratio (S/N) flares. For a conservative false alarm probability our method can detect 95 per cent of flares with S/N less than 20, as compared to S/N of 25 for the simpler method. We also test how well the assumption of Gaussian noise holds by applying the method to a selection of 'quiet' Kepler stars. As an example we have applied our method to a selection of stars in Kepler Quarter 1 data. The method finds 687 flaring stars with a total of 1873 flares after vetos have been applied. For these flares we have made preliminary characterizations of their durations and and S/N.

(1 data file). Title: Direct observation of the energy release site in a solar flare by SDO/AIA, Hinode/EIS, and RHESSI Authors: Simões, P. J. A.; Graham, D. R.; Fletcher, L. Bibcode: 2015A&A...577A..68S Altcode: 2015arXiv150301491S
Aims: We present direct evidence of the detection of the main energy release site in a non-eruptive solar flare, SOL2013-11-09T06:38 UT. This GOES class C2.6 event was characterised by two flaring ribbons and a compact, bright coronal source located between them, which is the focus of our study.
Methods: We use imaging from SDO/AIA, and imaging spectroscopy from RHESSI to characterise the thermal and non-thermal emission from the coronal source, and EUV spectroscopy from the Hinode/Extreme ultraviolet Imaging Spectrometer, which scanned the coronal source during the impulsive peak, to analyse Doppler shifts in Fe xii (log T = 6.2) and Fe xxiv (log T = 7.2) emission lines, and determine the source density.
Results: The coronal source exhibited an impulsive emission lightcurve in all SDO/AIA filters during the impulsive phase. RHESSI hard X-ray images indicate both thermal and non-thermal emission at the coronal source, and its plasma temperature derived from RHESSI imaging spectroscopy shows an impulsive rise, reaching a maximum at 12-13 MK about 10 s prior to the hard X-ray peak. High red-shifts associated with this bright source indicate downflows of 40-250 km s-1 at a broad range of temperatures, interpreted as loop shrinkage and/or outflows along the magnetic field. Outflows from the coronal source towards each ribbon are also observed by SDO/AIA images at 171, 193, 211, 304, and 1600 Å. The electron density of the source obtained from a Fe xiv line pair is 1011.50 cm-3 which is collisionally thick to electrons with energy up to 45-65 keV, responsible for the source's non-thermal X-ray emission.
Conclusions: Given the rich observational evidence, we conclude that the bright coronal source is the location of the main release of magnetic energy in this flare, with a geometry consistent with component reconnection between crossing, current-carrying loops. We argue that the energy that can be released via reconnection, based on observational estimates, can plausibly account for the non-thermal energetics of the flare. Title: Electric Current Circuits in Astrophysics Authors: Kuijpers, Jan; Frey, Harald U.; Fletcher, Lyndsay Bibcode: 2015SSRv..188....3K Altcode: 2014arXiv1403.0795K; 2014SSRv..tmp...19K Cosmic magnetic structures have in common that they are anchored in a dynamo, that an external driver converts kinetic energy into internal magnetic energy, that this magnetic energy is transported as Poynting flux across the magnetically dominated structure, and that the magnetic energy is released in the form of particle acceleration, heating, bulk motion, MHD waves, and radiation. The investigation of the electric current system is particularly illuminating as to the course of events and the physics involved. We demonstrate this for the radio pulsar wind, the solar flare, and terrestrial magnetic storms. Title: Reanalysis of Uranus' cloud scattering properties from IRTF/SpeX observations using a self-consistent scattering cloud retrieval scheme Authors: Irwin, P. G. J.; Tice, D. S.; Fletcher, L. N.; Barstow, J. K.; Teanby, N. A.; Orton, G. S.; Davis, G. R. Bibcode: 2015Icar..250..462I Altcode: 2016arXiv160102814I We have developed a new retrieval approach to modelling near-infrared spectra of Uranus that represents a significant improvement over previous modelling methods. We reanalysed IRTF/SpeX observations of Uranus observed in 2009 covering the wavelength range 0.8-1.8 μm and reported by Tice et al. (Tice, D.S., Irwin, P.G.J., Fletcher, L.N., Teanby, N.A., Hurley, J., Orton, G.S., Davis, G.R. [2013]. Icarus 223, 684-698). By retrieving the imaginary refractive index spectra of cloud particles we are able to consistently define the real part of the refractive index spectra, through a Kramers-Kronig analysis, and thus determine self-consistent extinction cross-section, single-scattering and phase-function spectra for the clouds and hazes in Uranus' atmosphere. We tested two different cloud-modelling schemes used in conjunction with the temperature/methane profile of Baines et al. (Baines, K.H., Mickelson, M.E., Larson, L.E., Ferguson, D.W. [1995]. Icarus 114, 328-340), a reanalysis of the Voyager-2 radio-occultation observations performed by Sromovsky, Fry and Kim (Sromovsky, L.A., Fry, P.M., Kim, J.H. [2011]. Icarus 215, 292-312), and a recent determination from Spitzer (Orton, G.S., Fletcher, L.N., Moses, J.I., Mainzer, A.K., Hines, D., Hammel, H.B., Martin-Torres, F.J., Burgdorf, M., Merlet, C., Line, M.R. [2014]. Icarus 243, 494-513). We find that both cloud-modelling schemes represent the observed centre-of-disc spectrum of Uranus well, and both require similar cloud scattering properties of the main cloud residing at ∼2 bars. However, a modified version of the Sromovsky, Fry and Kim (2011) model, with revised spectral properties of the lowest cloud layer, fits slightly better at shorter wavelengths and is more consistent with the expected vertical position of Uranus' methane cloud.

We find that the bulk of the reflected radiance from Uranus arises from a thick cloud at approximately the 2 bar level, composed of particles that are significantly more absorbing at wavelengths λ > 1.0 μm than they are at shorter wavelengths λ < 1.0 μm. This spectral information provides a possible constraint on the identity of the main particle type, although we find that the scattering properties required are not consistent with any of the available laboratory data for pure NH3, NH4SH, or CH4 ice (all suspected of condensing in the upper troposphere). It is possible that the observed clouds are mixtures of tropospheric condensate mixed with photochemical products diffusing down from above, which masks their pure scattering features. Because there is no available laboratory data for pure H2S or PH3 ice (both of which might be present as well), they cannot be excluded as the cloud-forming species. We note, however, that their absorptive properties would have to be two orders of magnitude greater than the other measured ices at wavelengths greater than 1 μm to be consistent with our retrieval, which suggests that mixing with photochemical products may still be important. Title: IRIS Observations of the Mg II h & k Lines During a Solar Flare Authors: Kerr, Graham Stewart; Simões, Paulo J. A.; Qiu, Jiong; Fletcher, Lyndsay Bibcode: 2015TESS....130702K Altcode: The bulk of the radiative output of a solar flare is radiated from the chromosphere. We have, until very recently, lacked routine observations of one of the strongest chromospheric lines: the MgII h&k resonance lines. These optically thick lines sample the atmosphere from the upper photosphere to the upper chromosphere and have been shown to be important diagnostics of the atmosphere in the non flaring features (quiet Sun, plage, network, sunspots, and prominences). However, only one flare observation of these lines has been reported (Lemaire et al 1984). With the launch of the IRIS solar telescope we are in a position to routinely observe the MgII h&k lines during flares, and we present a detailed study of the response of these lines to a solar flare. The spatial and temporal behaviour of the integrated intensities, k/h line ratios, line of sight velocities, line widths and line asymmetries were investigated during an M class flare, using a nonparametric quartiles approach. Redshifts of ~20km/s and line broadenings are observed at times of significant intensity enhancements, at the outer edge of the flare ribbons. The lines show blue asymmetry in only the most intense sources. Interestingly the characteristic central reversal feature that is ubiquitous in quiet Sun observations is absent in flaring profiles. Subordinate lines in the MgII passband are observed to be in emission within flaring sources, brightening and cooling in sync with the resonance lines. Additionally, we present the results of initial experiments with advanced numerical models to aid in the physical interpretation of these observed properties. This was achieved using the radiation hydrodynamic code RADYN that simulates the response of the solar atmosphere to flare energy input (we used a range of beam parameters to investigate energy injection to the atmosphere). RADYN provides both the hydrodynamic response of the atmosphere and the radiative response in energetically important lines and continua. The hydrodynamic output from RADYN was used as input to the radiative transfer code RH that solves the MgII resonance lines using partial redistributon. Title: The Radiated Energy Budget Of Chromospheric Plasma In A Major Solar Flare Deduced From Multi-Wavelength Observations Authors: Milligan, Ryan; Kerr, Graham Stewart; Dennis, Brian; Hudson, Hugh; Fletcher, Lyndsay; Allred, Joel; Chamberlin, Phillip; Ireland, Jack; Mathioudakis, Mihalis; Keenan, Francis Bibcode: 2015TESS....130209M Altcode: The response of the lower solar atmosphere is an important diagnostic tool for understanding energy transport during solar flares. The 15 February 2011 X-class flare was fortuitously observed by a host of space-based instruments that sampled the chromospheric response over a range of lines and continua at <20s cadence. These include the free-bound EUV continua of H I (Lyman), He I, and He II, plus the emission lines of He II at 304Å and H I (Lyα) at 1216Å by SDO/EVE, the UV continua at 1600Å and 1700Å by SDO/AIA, and the white light continuum at 4504Å, 5550Å, and 6684Å, along with the Ca II H line at 3968Å using Hinode/SOT. RHESSI also observed the entire event at energies up to ~100keV, making it possible to determine the properties of the nonthermal electrons deemed to be responsible for driving the enhanced chromospheric emission under the assumption of thick-target collisions. Integrating over the duration of the impulsive phase, the total energy contained in the nonthermal electrons was found to be >2×1031 erg. By comparison, the summed energy detected by instruments onboard SDO and Hinode amounted to ~3×1030 erg; about 15% of the total nonthermal energy. The Lyα line was found to dominate the measured radiative losses in contrast to the predictions of numerical simulations. Parameters of both the driving electron distribution and the resulting chromospheric response are presented in detail to encourage the numerical modeling of flare heating for this event to determine the depth of the solar atmosphere at which these line and continuum processes originate, and the mechanism(s) responsible for their generation. Title: Transit spectroscopy with James Webb Space Telescope: systematics, starspots and stitching Authors: Barstow, J. K.; Aigrain, S.; Irwin, P. G. J.; Kendrew, S.; Fletcher, L. N. Bibcode: 2015MNRAS.448.2546B Altcode: 2015arXiv150106349B The James Webb Space Telescope (JWST) is predicted to make great advances in the field of exoplanet atmospheres. Its 25 m2 mirror means that it can reach unprecedented levels of precision in observations of transit spectra, and can thus characterize the atmospheres of planets orbiting stars several hundred pc away. Its coverage of the infrared spectral region between 0.6 and 28 μm allows the abundances of key molecules to be probed during the transit of a planet in front of the host star, and when the same planet is eclipsed constraints can be placed on its temperature structure. In this work, we explore the possibility of using low-spectral-resolution observations by JWST/Near-Infrared Spectrograph and JWST/Mid-Infrared Instrumen-Low Resolution Spectrometer together to optimize wavelength coverage and break degeneracies in the atmospheric retrieval problem for a range of exoplanets from hot Jupiters to super-Earths. This approach involves stitching together non-simultaneous observations in different wavelength regions, rendering it necessary to consider the effect of time-varying instrumental and astrophysical systematics. We present the results of a series of retrieval feasibility tests examining the effects of instrument systematics and starspots on the recoverability of the true atmospheric state, and demonstrate that correcting for these systematics is key for successful exoplanet science with JWST. Title: Microflares to megaflares: Solar observations and modeling Authors: Fletcher, Lyndsay Bibcode: 2015HiA....16...97F Altcode: The observationally determined properties of solar flares such as overall energy budget and distribution in space, time and energy of flare radiation, have improved enormously over the last cycle. This has enabled precision diagnostics of flare plasmas and nonthermal particles in large and small events, informing and driving new theoretical models. The theoretical challenges in understanding flare are considerable, involving MHD and kinetic processes operating in an environment far from equilibrium. New observations have also provided some challenges to long-standing models of flare energy release and transport. This talk overviewed recent observational and theoretical developments, and highlighted some important questions for the future Title: Stratospheric Chemistry in Saturn's Atmosphere During the Beacon Storm Authors: Armstrong, E. S.; Moses, J. L.; Fletcher, L. N.; Irwin, P. G. J.; Hesman, B. E.; Romani, P. N. Bibcode: 2015LPI....46.1188A Altcode: 2015LPICo1832.1188A Stratospheric chemistry is investigated to try to reconcile photochemical model outputs with Cassini/CIRS observations during the Beacon Storm (2010-12). Title: Optical Spectral Observations of a Flickering White-light Kernel in a C1 Solar Flare Authors: Kowalski, Adam F.; Cauzzi, Gianna; Fletcher, Lyndsay Bibcode: 2015ApJ...798..107K Altcode: 2014arXiv1411.0770K We analyze optical spectra of a two-ribbon, long-duration C1.1 flare that occurred on 2011 August 18 within AR 11271 (SOL2011-08-18T15:15). The impulsive phase of the flare was observed with a comprehensive set of space-borne and ground-based instruments, which provide a range of unique diagnostics of the lower flaring atmosphere. Here we report the detection of enhanced continuum emission, observed in low-resolution spectra from 3600 Å to 4550 Å acquired with the Horizontal Spectrograph at the Dunn Solar Telescope. A small, <=0.''5 (1015 cm2) penumbral/umbral kernel brightens repeatedly in the optical continuum and chromospheric emission lines, similar to the temporal characteristics of the hard X-ray variation as detected by the Gamma-ray Burst Monitor on the Fermi spacecraft. Radiative-hydrodynamic flare models that employ a nonthermal electron beam energy flux high enough to produce the optical contrast in our flare spectra would predict a large Balmer jump in emission, indicative of hydrogen recombination radiation from the upper flare chromosphere. However, we find no evidence of such a Balmer jump in the bluemost spectral region of the continuum excess. Just redward of the expected Balmer jump, we find evidence of a "blue continuum bump" in the excess emission which may be indicative of the merging of the higher order Balmer lines. The large number of observational constraints provides a springboard for modeling the blue/optical emission for this particular flare with radiative-hydrodynamic codes, which are necessary to understand the opacity effects for the continuum and emission line radiation at these wavelengths. Title: A Bayesian method for detecting stellar flares Authors: Pitkin, M.; Williams, D.; Fletcher, L.; Grant, S. D. T. Bibcode: 2014MNRAS.445.2268P Altcode: 2014arXiv1406.1712P We present a Bayesian-odds-ratio-based algorithm for detecting stellar flares in light-curve data. We assume flares are described by a model in which there is a rapid rise with a half-Gaussian profile, followed by an exponential decay. Our signal model also contains a polynomial background model required to fit underlying light-curve variations in the data, which could otherwise partially mimic a flare. We characterize the false alarm probability and efficiency of this method under the assumption that any unmodelled noise in the data is Gaussian, and compare it with a simpler thresholding method based on that used in Walkowicz et al. We find our method has a significant increase in detection efficiency for low signal-to-noise ratio (S/N) flares. For a conservative false alarm probability our method can detect 95 per cent of flares with S/N less than 20, as compared to S/N of 25 for the simpler method. We also test how well the assumption of Gaussian noise holds by applying the method to a selection of `quiet' Kepler stars. As an example we have applied our method to a selection of stars in Kepler Quarter 1 data. The method finds 687 flaring stars with a total of 1873 flares after vetos have been applied. For these flares we have made preliminary characterizations of their durations and and S/N. Title: Neptune and Triton: Essential pieces of the Solar System puzzle Authors: Masters, A.; Achilleos, N.; Agnor, C. B.; Campagnola, S.; Charnoz, S.; Christophe, B.; Coates, A. J.; Fletcher, L. N.; Jones, G. H.; Lamy, L.; Marzari, F.; Nettelmann, N.; Ruiz, J.; Ambrosi, R.; Andre, N.; Bhardwaj, A.; Fortney, J. J.; Hansen, C. J.; Helled, R.; Moragas-Klostermeyer, G.; Orton, G.; Ray, L.; Reynaud, S.; Sergis, N.; Srama, R.; Volwerk, M. Bibcode: 2014P&SS..104..108M Altcode: The planet Neptune and its largest moon Triton hold the keys to major advances across multiple fields of Solar System science. The ice giant Neptune played a unique and important role in the process of Solar System formation, has the most meteorologically active atmosphere in the Solar System (despite its great distance from the Sun), and may be the best Solar System analogue of the dominant class of exoplanets detected to date. Neptune's moon Triton is very likely a captured Kuiper Belt object, holding the answers to questions about the icy dwarf planets that formed in the outer Solar System. Triton is geologically active, has a tenuous nitrogen atmosphere, and is predicted to have a subsurface ocean. However, our exploration of the Neptune system remains limited to a single spacecraft flyby, made by Voyager 2 in 1989. Here, we present the high-level science case for further exploration of this outermost planetary system, based on a white paper submitted to the European Space Agency (ESA) for the definition of the second and third large missions in the ESA Cosmic Vision Programme 2015-2025. We discuss all the major science themes that are relevant for further spacecraft exploration of the Neptune system, and identify key scientific questions in each area. We present an overview of the results of a European-led Neptune orbiter mission analysis. Such a mission has significant scope for international collaboration, and is essential to achieve our aim of understanding how the Solar System formed, and how it works today. Title: The science case for an orbital mission to Uranus: Exploring the origins and evolution of ice giant planets Authors: Arridge, C. S.; Achilleos, N.; Agarwal, J.; Agnor, C. B.; Ambrosi, R.; André, N.; Badman, S. V.; Baines, K.; Banfield, D.; Barthélémy, M.; Bisi, M. M.; Blum, J.; Bocanegra-Bahamon, T.; Bonfond, B.; Bracken, C.; Brandt, P.; Briand, C.; Briois, C.; Brooks, S.; Castillo-Rogez, J.; Cavalié, T.; Christophe, B.; Coates, A. J.; Collinson, G.; Cooper, J. F.; Costa-Sitja, M.; Courtin, R.; Daglis, I. A.; de Pater, I.; Desai, M.; Dirkx, D.; Dougherty, M. K.; Ebert, R. W.; Filacchione, G.; Fletcher, L. N.; Fortney, J.; Gerth, I.; Grassi, D.; Grodent, D.; Grün, E.; Gustin, J.; Hedman, M.; Helled, R.; Henri, P.; Hess, S.; Hillier, J. K.; Hofstadter, M. H.; Holme, R.; Horanyi, M.; Hospodarsky, G.; Hsu, S.; Irwin, P.; Jackman, C. M.; Karatekin, O.; Kempf, S.; Khalisi, E.; Konstantinidis, K.; Krüger, H.; Kurth, W. S.; Labrianidis, C.; Lainey, V.; Lamy, L. L.; Laneuville, M.; Lucchesi, D.; Luntzer, A.; MacArthur, J.; Maier, A.; Masters, A.; McKenna-Lawlor, S.; Melin, H.; Milillo, A.; Moragas-Klostermeyer, G.; Morschhauser, A.; Moses, J. I.; Mousis, O.; Nettelmann, N.; Neubauer, F. M.; Nordheim, T.; Noyelles, B.; Orton, G. S.; Owens, M.; Peron, R.; Plainaki, C.; Postberg, F.; Rambaux, N.; Retherford, K.; Reynaud, S.; Roussos, E.; Russell, C. T.; Rymer, A. M.; Sallantin, R.; Sánchez-Lavega, A.; Santolik, O.; Saur, J.; Sayanagi, K. M.; Schenk, P.; Schubert, J.; Sergis, N.; Sittler, E. C.; Smith, A.; Spahn, F.; Srama, R.; Stallard, T.; Sterken, V.; Sternovsky, Z.; Tiscareno, M.; Tobie, G.; Tosi, F.; Trieloff, M.; Turrini, D.; Turtle, E. P.; Vinatier, S.; Wilson, R.; Zarka, P. Bibcode: 2014P&SS..104..122A Altcode: Giant planets helped to shape the conditions we see in the Solar System today and they account for more than 99% of the mass of the Sun's planetary system. They can be subdivided into the Ice Giants (Uranus and Neptune) and the Gas Giants (Jupiter and Saturn), which differ from each other in a number of fundamental ways. Uranus, in particular is the most challenging to our understanding of planetary formation and evolution, with its large obliquity, low self-luminosity, highly asymmetrical internal field, and puzzling internal structure. Uranus also has a rich planetary system consisting of a system of inner natural satellites and complex ring system, five major natural icy satellites, a system of irregular moons with varied dynamical histories, and a highly asymmetrical magnetosphere. Voyager 2 is the only spacecraft to have explored Uranus, with a flyby in 1986, and no mission is currently planned to this enigmatic system. However, a mission to the uranian system would open a new window on the origin and evolution of the Solar System and would provide crucial information on a wide variety of physicochemical processes in our Solar System. These have clear implications for understanding exoplanetary systems. In this paper we describe the science case for an orbital mission to Uranus with an atmospheric entry probe to sample the composition and atmospheric physics in Uranus' atmosphere. The characteristics of such an orbiter and a strawman scientific payload are described and we discuss the technical challenges for such a mission. This paper is based on a white paper submitted to the European Space Agency's call for science themes for its large-class mission programme in 2013. Title: Scientific rationale for Saturn's in situ exploration Authors: Mousis, O.; Fletcher, L. N.; Lebreton, J. -P.; Wurz, P.; Cavalié, T.; Coustenis, A.; Courtin, R.; Gautier, D.; Helled, R.; Irwin, P. G. J.; Morse, A. D.; Nettelmann, N.; Marty, B.; Rousselot, P.; Venot, O.; Atkinson, D. H.; Waite, J. H.; Reh, K. R.; Simon, A. A.; Atreya, S.; André, N.; Blanc, M.; Daglis, I. A.; Fischer, G.; Geppert, W. D.; Guillot, T.; Hedman, M. M.; Hueso, R.; Lellouch, E.; Lunine, J. I.; Murray, C. D.; O`Donoghue, J.; Rengel, M.; Sánchez-Lavega, A.; Schmider, F. -X.; Spiga, A.; Spilker, T.; Petit, J. -M.; Tiscareno, M. S.; Ali-Dib, M.; Altwegg, K.; Bolton, S. J.; Bouquet, A.; Briois, C.; Fouchet, T.; Guerlet, S.; Kostiuk, T.; Lebleu, D.; Moreno, R.; Orton, G. S.; Poncy, J. Bibcode: 2014P&SS..104...29M Altcode: 2014arXiv1404.4811M Remote sensing observations meet some limitations when used to study the bulk atmospheric composition of the giant planets of our solar system. A remarkable example of the superiority of in situ probe measurements is illustrated by the exploration of Jupiter, where key measurements such as the determination of the noble gases' abundances and the precise measurement of the helium mixing ratio have only been made available through in situ measurements by the Galileo probe. This paper describes the main scientific goals to be addressed by the future in situ exploration of Saturn placing the Galileo probe exploration of Jupiter in a broader context and before the future probe exploration of the more remote ice giants. In situ exploration of Saturn's atmosphere addresses two broad themes that are discussed throughout this paper: first, the formation history of our solar system and second, the processes at play in planetary atmospheres. In this context, we detail the reasons why measurements of Saturn's bulk elemental and isotopic composition would place important constraints on the volatile reservoirs in the protosolar nebula. We also show that the in situ measurement of CO (or any other disequilibrium species that is depleted by reaction with water) in Saturn's upper troposphere may help constraining its bulk O/H ratio. We compare predictions of Jupiter and Saturn's bulk compositions from different formation scenarios, and highlight the key measurements required to distinguish competing theories to shed light on giant planet formation as a common process in planetary systems with potential applications to most extrasolar systems. In situ measurements of Saturn's stratospheric and tropospheric dynamics, chemistry and cloud-forming processes will provide access to phenomena unreachable to remote sensing studies. Different mission architectures are envisaged, which would benefit from strong international collaborations, all based on an entry probe that would descend through Saturn's stratosphere and troposphere under parachute down to a minimum of 10 bar of atmospheric pressure. We finally discuss the science payload required on a Saturn probe to match the measurement requirements. Title: Long-Term Time Variability of Temperature, Gas Abundance and Cloud Fields in Jupiter from Thermal Emission Observations Authors: Orton, G. S.; Fletcher, L. N.; Yanamandra-Fisher, P. A.; Fisher, B.; Greathouse, T. K.; Liu, J.; Schneider, T.; Kim, S. Bibcode: 2014AGUFM.P23A3973O Altcode: Mid-infrared raster-scans and 2D images of Jupiter's thermal emission in discrete filters between 4.8 and 24.5 μm have been have covered nearly 2 Jovian years, enabling time-domain studies of its temperature field, minor-constituent distribution and cloud properties. The behavior of stratospheric (~10-mbar) and tropospheric (~100-400 mbar) temperatures is generally consistent with predictions of seasonal variability. These also appear to be long-term periodicities of tropospheric temperatures, with meridionally dependent amplitudes, phases and periods. Temperatures near and south of the equator vary least. There were no variations of zonal mean temperatures associated with any of the "global upheaval" or the corresponding "revival" events that have produced dramatic changes of Jupiter's visible appearance and cloud cover, although there are colder discrete regions associated with the updraft events that marked the early stages of revivals. Changes visible albedo are accompanied by increases in cloudiness at 700 mbar and higher pressures, together with the mixing ratio of NH3 gas. In contrast to all these changes, the meridional distribution of the 240-mbar para-H2 fraction appears to be time-invariant. Jupiter also exhibits prominent temperature waves in both the upper troposphere and stratosphere that move slowly retrograde in System III. Unlike Saturn's slowly moving waves, these waves are ubiquitous at certain latitudes and at all longitudes therein. The time scale for coherence of these waves is somewhere between a few days and 4 weeks. These waves are consistent with convectively generated Rossby waves. Title: The Europa Imaging System (EIS): High-Resolution, 3-D Insight into Europa's Geology, Ice Shell, and Potential for Current Activity Authors: Turtle, E. P.; McEwen, A. S.; Collins, G. C.; Fletcher, L. N.; Hansen, C. J.; Hayes, A.; Hurford, T., Jr.; Kirk, R. L.; Barr, A.; Nimmo, F.; Patterson, G.; Quick, L. C.; Soderblom, J. M.; Thomas, N. Bibcode: 2014AGUFM.P13E..03T Altcode: The Europa Imaging System will transform our understanding of Europa through global decameter-scale coverage, three-dimensional maps, and unprecedented meter-scale imaging. EIS combines narrow-angle and wide-angle cameras (NAC and WAC) designed to address high-priority Europa science and reconnaissance goals. It will: (A) Characterize the ice shell by constraining its thickness and correlating surface features with subsurface structures detected by ice penetrating radar; (B) Constrain formation processes of surface features and the potential for current activity by characterizing endogenic structures, surface units, global cross-cutting relationships, and relationships to Europa's subsurface structure, and by searching for evidence of recent activity, including potential plumes; and (C) Characterize scientifically compelling landing sites and hazards by determining the nature of the surface at scales relevant to a potential lander. The NAC provides very high-resolution, stereo reconnaissance, generating 2-km-wide swaths at 0.5-m pixel scale from 50-km altitude, and uses a gimbal to enable independent targeting. NAC observations also include: near-global (>95%) mapping of Europa at ≤50-m pixel scale (to date, only ~14% of Europa has been imaged at ≤500 m/pixel, with best pixel scale 6 m); regional and high-resolution stereo imaging at <1-m/pixel; and high-phase-angle observations for plume searches. The WAC is designed to acquire pushbroom stereo swaths along flyby ground-tracks, generating digital topographic models with 32-m spatial scale and 4-m vertical precision from 50-km altitude. These data support characterization of cross-track clutter for radar sounding. The WAC also performs pushbroom color imaging with 6 broadband filters (350-1050 nm) to map surface units and correlations with geologic features and topography. EIS will provide comprehensive data sets essential to fulfilling the goal of exploring Europa to investigate its habitability and perform collaborative science with other investigations, including cartographic and geologic maps, regional and high-resolution digital topography, GIS products, color and photometric data products, a geodetic control network tied to radar altimetry, and a database of plume-search observations. Title: Photochemistry in Saturn's Ring-Shadowed Atmosphere: Modeling of Key Molecules and Observations of Dust Content Authors: Edgington, S. G.; Atreya, S. K.; Wilson, E. H.; West, R. A.; Fletcher, L. N.; Baines, K. H.; Bjoraker, G. L.; Momary, T. Bibcode: 2014AGUFM.P23A3975E Altcode: Cassini has been orbiting Saturn for over ten years now. During this epoch, the ring shadow has moved from covering a large portion of the northern hemisphere to covering a large swath south of the equator and continues to move southward. At Saturn Orbit Insertion in 2004, the ring plane was inclined by ~24 degrees relative to the Sun-Saturn vector. The projection of the B-ring onto Saturn reached as far as 40N along the central meridian (~52N at the terminator). At its maximum extent, the ring shadow can reach as far as 48N/S (~58N/S at the terminator). The net effect is that the intensity of both ultraviolet and visible sunlight penetrating into any particular latitude will vary depending on both Saturn's axis relative to the Sun and the optical thickness of each ring system. In essence, the rings act like venetian blinds. Our previous work [1] examined the variation of the solar flux as a function of solar inclination, i.e. ~7.25 year season at Saturn. Here, we report on the impact of the oscillating ring shadow on the photolysis and production rates of hydrocarbons in Saturn's stratosphere and upper troposphere, including acetylene, ethane, propane, and benzene. Beginning with methane, we investigate the impact on production and loss rates of the long-lived photochemical products leading to haze formation are examined at several latitudes over a Saturn year. Similarly, we assess its impact on phosphine abundance, a disequilibrium species whose presence in the upper troposphere is a tracer of convective processes in the deep atmosphere. We will also present our ongoing analysis of Cassini's CIRS, UVIS, and VIMS datasets that provide an estimate of the evolving haze content of the northern hemisphere and we will begin to assess the implications for dynamical mixing. In particular, we will examine how the now famous hexagonal jet stream acts like a barrier to transport, isolating Saturn's north polar region from outside transport of photochemically-generated molecules and haze. [1] Edgington, S.G., et al., 2012. Photochemistry in Saturn's Ring Shadowed Atmosphere: Modeling, Observations, and Preliminary Analysis. Bull. American. Astron. Soc., 38, 499 (#11.23). Title: On the Origin of a Sunquake during the 2014 March 29 X1 Flare Authors: Judge, Philip G.; Kleint, Lucia; Donea, Alina; Sainz Dalda, Alberto; Fletcher, Lyndsay Bibcode: 2014ApJ...796...85J Altcode: 2014arXiv1409.6268J Helioseismic data from the Helioseismic Magnetic Imager instrument have revealed a sunquake associated with the X1 flare SOL2014-03-29T17:48 in active region NOAA 12017. We try to discover if acoustic-like impulses or actions of the Lorentz force caused the sunquake. We analyze spectropolarimetric data obtained with the Facility Infrared Spectrometer (FIRS) at the Dunn Solar Telescope (DST). Fortunately, the FIRS slit crossed the flare kernel close to the acoustic source during the impulsive phase. The infrared FIRS data remain unsaturated throughout the flare. Stokes profiles of lines of Si I 1082.7 nm and He I 1083.0 nm are analyzed. At the flare footpoint, the Si I 1082.7 nm core intensity increases by a factor of several, and the IR continuum increases by 4% ± 1%. Remarkably, the Si I core resembles the classical Ca II K line's self-reversed profile. With nLTE radiative models of H, C, Si, and Fe, these properties set the penetration depth of flare heating to 100 ± 100 km (i.e., photospheric layers). Estimates of the non-magnetic energy flux are at least a factor of two less than the sunquake energy flux. Milne-Eddington inversions of the Si I line show that the local magnetic energy changes are also too small to drive the acoustic pulse. Our work raises several questions. Have we missed the signature of downward energy propagation? Is it intermittent in time and/or non-local? Does the 1-2 s photospheric radiative damping time discount compressive modes?

The National Center for Atmospheric Research is sponsored by the National Science Foundation. Title: Constraints on Jupiter's stratospheric HCl abundance and chlorine cycle from Herschel/HIFI Authors: Teanby, N. A.; Showman, A. P.; Fletcher, L. N.; Irwin, P. G. J. Bibcode: 2014P&SS..103..250T Altcode: Detection of HCl on Jupiter would provide insight into the chlorine cycle and external elemental fluxes on giant planets, yet so far has not been possible. Here we present the most sensitive search for Jupiter's stratospheric HCl to date using observations of the 625.907 and 1876.221 GHz spectral lines with Herschel's HIFI instrument. HCl was not detected, but we determined the most stringent upper limits so far, improving on previous studies by two orders of magnitude. If HCl is assumed to be uniformly mixed, with a constant volume mixing ratio above the 1 mbar pressure level and has zero abundance below, we obtain a 3-σ upper limit of 0.061 ppb; in contrast, if we assume uniform mixing above the 1 mbar level and allow a non-zero but downward-decreasing abundance from 1 mbar to the troposphere based on eddy diffusion, we obtain a 3-σ upper limit of 0.027 ppb. This is below the abundance expected for a solar composition cometary source and implies that upper stratospheric HCl loss processes are required for consistency with observations of the external oxygen flux. We investigated loss via aerosol scavenging using a simple diffusion model and conclude that it could be a very effective mechanism for HCl removal. Transient scavenging by stratospheric NH3 from impacts is another potentially important loss mechanism. This suggests that it is extremely unlikely that HCl is present in sufficient quantities to be detectable in the near future. An alternative explanation for our very low upper limits could be that HCl is sub-solar in comets or that cometary chlorine exists in inactive reservoirs that are not readily converted to HCl during the impact process. Title: The transit spectra of Earth and Jupiter Authors: Irwin, P. G. J.; Barstow, J. K.; Bowles, N. E.; Fletcher, L. N.; Aigrain, S.; Lee, J. -M. Bibcode: 2014Icar..242..172I Altcode: 2014arXiv1408.3914I In recent years, an increasing number of observations have been made of the transits of 'Hot Jupiters', such as HD 189733b, about their parent stars from the visible through to mid-infrared wavelengths, which have been modelled to derive the likely atmospheric structure and composition of these planets. As measurement techniques improve, the measured transit spectra of 'Super-Earths' such as GJ 1214b are becoming better constrained, allowing model atmospheric states to be fitted for this class of planet also. While it is not yet possible to constrain the atmospheric states of small planets such as the Earth or cold planets like Jupiter, it is hoped that this might become practical in the coming decades and if so, it is of interest to determine what we might infer from such measurements. In this work we have constructed atmospheric models of the Solar System planets from 0.4 to 15.5 μm that are consistent with ground-based and satellite observations and from these calculate the primary transit and secondary eclipse spectra (with respect to the Sun and typical M-dwarfs) that would be observed by a 'remote observer', many light years away. From these spectra we test what current retrieval models might infer about their atmospheric states and compare these with the 'ground truths' in order to assess: (a) the inherent uncertainties in transit spectra observations; (b) the relative merits of primary transit and secondary eclipse spectra; and (c) the advantages of acquiring directly imaged spectra of these planets. We find that observing secondary eclipses of the Solar System would not give sufficient information for determining atmospheric properties with 10 m-diameter telescopes from a distance of 10 light years, but that primary transits give much better information. We find that a single transit of Jupiter in front of the Sun could potentially be used to determine temperature and stratospheric composition, but for the Earth the mean atmospheric composition could only be determined if it were orbiting a much smaller M-dwarf. For both Jupiter and Earth we note that direct imaging with sufficient nulling of the light from the parent star theoretically provides the best method of determining the atmospheric properties of such planets. Title: Instrumental methods for professional and amateur collaborations in planetary astronomy Authors: Mousis, O.; Hueso, R.; Beaulieu, J. -P.; Bouley, S.; Carry, B.; Colas, F.; Klotz, A.; Pellier, C.; Petit, J. -M.; Rousselot, P.; Ali-Dib, M.; Beisker, W.; Birlan, M.; Buil, C.; Delsanti, A.; Frappa, E.; Hammel, H. B.; Levasseur-Regourd, A. C.; Orton, G. S.; Sánchez-Lavega, A.; Santerne, A.; Tanga, P.; Vaubaillon, J.; Zanda, B.; Baratoux, D.; Böhm, T.; Boudon, V.; Bouquet, A.; Buzzi, L.; Dauvergne, J. -L.; Decock, A.; Delcroix, M.; Drossart, P.; Esseiva, N.; Fischer, G.; Fletcher, L. N.; Foglia, S.; Gómez-Forrellad, J. M.; Guarro-Fló, J.; Herald, D.; Jehin, E.; Kugel, F.; Lebreton, J. -P.; Lecacheux, J.; Leroy, A.; Maquet, L.; Masi, G.; Maury, A.; Meyer, F.; Pérez-Hoyos, S.; Rajpurohit, A. S.; Rinner, C.; Rogers, J. H.; Roques, F.; Schmude, R. W.; Sicardy, B.; Tregon, B.; Vanhuysse, M.; Wesley, A.; Widemann, T. Bibcode: 2014ExA....38...91M Altcode: 2013arXiv1305.3647M; 2014ExA...tmp...35M Amateur contributions to professional publications have increased exponentially over the last decades in the field of planetary astronomy. Here we review the different domains of the field in which collaborations between professional and amateur astronomers are effective and regularly lead to scientific publications.We discuss the instruments, detectors, software and methodologies typically used by amateur astronomers to collect the scientific data in the different domains of interest. Amateur contributions to the monitoring of planets and interplanetary matter, characterization of asteroids and comets, as well as the determination of the physical properties of Kuiper Belt Objects and exoplanets are discussed. Title: The Radiated Energy Budget of Chromospheric Plasma in a Major Solar Flare Deduced from Multi-wavelength Observations Authors: Milligan, Ryan O.; Kerr, Graham S.; Dennis, Brian R.; Hudson, Hugh S.; Fletcher, Lyndsay; Allred, Joel C.; Chamberlin, Phillip C.; Ireland, Jack; Mathioudakis, Mihalis; Keenan, Francis P. Bibcode: 2014ApJ...793...70M Altcode: 2014arXiv1406.7657M This paper presents measurements of the energy radiated by the lower solar atmosphere, at optical, UV, and EUV wavelengths, during an X-class solar flare (SOL2011-02-15T01:56) in response to an injection of energy assumed to be in the form of nonthermal electrons. Hard X-ray observations from RHESSI were used to track the evolution of the parameters of the nonthermal electron distribution to reveal the total power contained in flare accelerated electrons. By integrating over the duration of the impulsive phase, the total energy contained in the nonthermal electrons was found to be >2 × 1031 erg. The response of the lower solar atmosphere was measured in the free-bound EUV continua of H I (Lyman), He I, and He II, plus the emission lines of He II at 304 Å and H I (Lyα) at 1216 Å by SDO/EVE, the UV continua at 1600 Å and 1700 Å by SDO/AIA, and the white light continuum at 4504 Å, 5550 Å, and 6684 Å, along with the Ca II H line at 3968 Å using Hinode/SOT. The summed energy detected by these instruments amounted to ~3 × 1030 erg about 15% of the total nonthermal energy. The Lyα line was found to dominate the measured radiative losses. Parameters of both the driving electron distribution and the resulting chromospheric response are presented in detail to encourage the numerical modeling of flare heating for this event, to determine the depth of the solar atmosphere at which these line and continuum processes originate, and the mechanism(s) responsible for their generation. Title: Onset of Electron Acceleration in a Flare Loop Authors: Sharykin, Ivan; Liu, Siming; Fletcher, Lyndsay Bibcode: 2014ApJ...793...25S Altcode: 2014arXiv1408.1413S We carried out a detailed analysis of X-ray and radio observations of a simple flare loop that occurred on 2002 August 12, with the impulsive hard X-ray (HXR) light curves dominated by a single pulse. The emission spectra of the early impulsive phase are consistent with an isothermal model in the coronal loop with a temperature reaching several keV. A power-law high-energy spectral tail is evident near the HXR peak time, in accordance with the appearance of footpoints at high energies, and is well correlated with the radio emission. The energy content of the thermal component keeps increasing gradually after the disappearance of this nonthermal component. These results suggest that electron acceleration only covers the central period of a longer and more gradual energy dissipation process and that the electron transport within the loop plays a crucial role in the formation of the inferred power-law electron distribution. The spectral index of power-law photons shows a very gradual evolution, indicating that the electron accelerator is in a quasi-steady state, which is confirmed by radio observations. These results are consistent with the theory of stochastic electron acceleration from a thermal background. Advanced modeling with coupled electron acceleration and spatial transport processes is needed to explain these observations more quantitatively, which may reveal the dependence of the electron acceleration on the spatial structure of the acceleration region. Title: BayesFlare: Bayesian method for detecting stellar flares Authors: Pitkin, M.; Williams, D.; Fletcher, L.; Grant, S. D. T. Bibcode: 2014ascl.soft07015P Altcode: BayesFlare identifies flaring events in light curves released by the Kepler mission; it identifies even weak events by making use of the flare signal shape. The package contains functions to perform Bayesian hypothesis testing comparing the probability of light curves containing flares to that of them containing noise (or non-flare-like) artifacts. BayesFlare includes functions in its amplitude-marginalizer suite to account for underlying sinusoidal variations in light curve data; it includes such variations in the signal model, and then analytically marginalizes over them. Title: Thermal Emission Constraints on the Atmospheres of Uranus and Neptune Authors: Orton, G. S.; Fletcher, L. N.; Moses, J. I.; Lellouch, E.; Moreno, R.; Swinyard, B. M.; Hofstadter, M. D.; Greathouse, T. K. Bibcode: 2014LPICo1798.2002O Altcode: Photometric and spectroscopic observations of Uranus and Neptune have been analyzed from both spacecraft and Earth-based platforms, in order to create self-consistent models of their temperature fields and the distribution of trace gases. Title: Where is the Chromospheric Response to Conductive Energy Input from a Hot Pre-flare Coronal Loop? Authors: Battaglia, Marina; Fletcher, Lyndsay; Simões, Paulo J. A. Bibcode: 2014ApJ...789...47B Altcode: 2014arXiv1405.4621B Before the onset of a flare is observed in hard X-rays, there is often a prolonged pre-flare or pre-heating phase with no detectable hard X-ray emission but pronounced soft X-ray emission, which suggests that energy is already being released and deposited into the corona and chromosphere at this stage. This work analyzes the temporal evolution of coronal source heating and the chromospheric response during this pre-heating phase to investigate the origin and nature of early energy release and transport during a solar flare. Simultaneous X-ray, EUV, and microwave observations of a well-observed flare with a prolonged pre-heating phase are analyzed to study the time evolution of the thermal emission and to determine the onset of particle acceleration. During the 20 minute duration of the pre-heating phase we find no hint of accelerated electrons in either hard X-rays or microwave emission. However, the total energy budget during the pre-heating phase suggests that energy must be supplied to the flaring loop to sustain the observed temperature and emission measure. Under the assumption of this energy being transported toward the chromosphere via thermal conduction, significant energy deposition at the chromosphere is expected. However, no detectable increase of the emission in the AIA wavelength channels sensitive to chromospheric temperatures is observed. The observations suggest energy release and deposition in the flaring loop before the onset of particle acceleration, yet a model in which energy is conducted to the chromosphere and subsequent heating of the chromosphere is not supported by the observations. Title: Scientific Rationale and Concepts for an In Situ Saturn Probe Authors: Mousis, O.; Coustenis, A.; Lebreton, J. -P.; Atkinson, D. H.; Lunine, J. I.; Rey, K.; Fletcher, L. N.; Simon-Miller, A.; Atreya, S.; Brinckerhoff, W.; Cavalié, T.; Colaprete, A.; Gautier, D.; Guillot, T.; Hueso, R.; Mahaffy, P.; Marty, B.; Morse, A. D.; Sims, J.; Spilker, T.; Spilker, L.; Webster, C.; Waite, J. H.; Wurz, P. Bibcode: 2014LPICo1795.8094M Altcode: We summarize the science case for in situ measurements at Saturn and discuss the possible mission concepts that would be consistent with the constraints of ESA M-class missions. Title: F-CHROMA.Flare Chromospheres: Observations, Models and Archives Authors: Cauzzi, Gianna; Fletcher, Lyndsay; Mathioudakis, Mihalis; Carlsson, Mats; Heinzel, Petr; Berlicki, Arek; Zuccarello, Francesca Bibcode: 2014AAS...22412339C Altcode: F-CHROMA is a collaborative project newly funded under the EU-Framework Programme 7 "FP7-SPACE-2013-1", involving seven different European research Institutes and Universities. The goal of F-CHROMA is to substantially advance our understanding of the physics of energy dissipation and radiation in the flaring solar atmosphere, with a particular focus on the flares' chromosphere. A major outcome of the F-CHROMA project will be the creation of an archive of chromospheric flare observations and models to be made available to the community for further research.In this poster we describe the structure and milestones of the project, the different activities planned, as well as early results. Emphasis will be given to the dissemination efforts of the project to make results of these activities available to and usable by the community. Title: In Situ Probe Science at Saturn Authors: Atkinson, D. H.; Lunine, J. I.; Simon-Miller, A. A.; Atreya, S. K.; Brinckerhoff, W.; Colaprete, A.; Coustenis, A.; Fletcher, L. N.; Guillot, T.; Lebreton, J. -P.; Mahaffy, P.; Mousis, O.; Orton, G. S.; Reh, K.; Spilker, L. J.; Spilker, T. R.; Webster, C. Bibcode: 2014LPICo1795.8005A Altcode: Key to understanding solar system formation and evolution is the origin and evolution of the giant planets. A small shallow Saturn probe can serve to test competing theories of solar system and giant planet origin, chemical, and dynamical evolution. Title: From Voyager-IRIS to Cassini-CIRS: Interannual variability in Saturn’s stratosphere? Authors: Sinclair, J. A.; Irwin, P. G. J.; Fletcher, L. N.; Greathouse, T.; Guerlet, S.; Hurley, J.; Merlet, C. Bibcode: 2014Icar..233..281S Altcode: We present an intercomparison of Saturn’s stratosphere between Voyager 1-IRIS observations in 1980 and Cassini-CIRS observations in 2009 and 2010. Over a saturnian year (∼29.5 years) has now passed since the Voyager flybys of Saturn in 1980/1981. Cassini observations in 2009/2010 capture Saturn in the same season as Voyager observations (just after the vernal equinox) but one year later. Any differences in Saturn’s atmospheric properties implied by a comparison of these two datasets could therefore reveal the extent of interannual variability. We retrieve temperature and stratospheric acetylene and ethane concentrations from Voyager 1-IRIS (Δν∼=4.3 cm-1) observations in 1980 and Cassini-CIRS (Δν∼=15.5 cm-1) ‘FIRMAP’ observations in 2009 and 2010. We observe a difference in temperature at the equator of 7.1 ± 1.2 K at the 2.1-mbar level that implies that the two datasets have captured Saturn’s semiannual oscillation (SSAO) in a slightly different phase suggesting that its period is more quasi-semiannual. Elevated concentrations of acetylene at 25°S in 1980 with respect to 2010 imply stronger downwelling at the former date which may also be explained by a difference in the phase of the SSAO and its dynamical forcing at low latitudes. At high-southern and high-northern latitudes, stratospheric temperatures and hydrocarbon concentrations appear elevated in 1980 with respect to 2009/2010. This could be an artefact of the low signal-to-noise ratio of the corresponding observations but might also be explained by increased auroral activity during solar maximum in 1980. Title: Changes to Saturn's Zonal-mean Tropospheric Thermal Structure after the 2010-2011 Northern Hemisphere Storm Authors: Achterberg, R. K.; Gierasch, P. J.; Conrath, B. J.; Fletcher, L. N.; Hesman, B. E.; Bjoraker, G. L.; Flasar, F. M. Bibcode: 2014ApJ...786...92A Altcode: We use far-infrared (20-200 μm) data from the Composite Infrared Spectrometer on the Cassini spacecraft to determine the zonal-mean temperature and hydrogen para-fraction in Saturn's upper troposphere from observations taken before and after the large northern hemisphere storm in 2010-2011. During the storm, zonal mean temperatures in the latitude band between approximately 25°N and 45°N (planetographic latitude) increased by about 3 K, while the zonal mean hydrogen para-fraction decreased by about 0.04 over the same latitudes, at pressures greater than about 300 mbar. These changes occurred over the same latitude range as the disturbed cloud band seen in visible images. The observations are consistent with low para-fraction gas being brought up from the level of the water cloud by the strong convective plume associated with the storm, while being heated by condensation of water vapor, and then advected zonally by the winds near the plume tops in the upper troposphere. Title: Clouds on the Hot Jupiter HD189733b: Constraints from the Reflection Spectrum Authors: Barstow, J. K.; Aigrain, S.; Irwin, P. G. J.; Hackler, T.; Fletcher, L. N.; Lee, J. M.; Gibson, N. P. Bibcode: 2014ApJ...786..154B Altcode: 2014arXiv1403.6664B The hot Jupiter HD 189733b is probably the best studied of the known extrasolar planets, with published transit and eclipse spectra covering the near UV to mid-IR range. Recent work on the transmission spectrum has shown clear evidence for the presence of clouds in its atmosphere, which significantly increases the model atmosphere parameter space that must be explored in order to fully characterize this planet. In this work, we apply the NEMESIS atmospheric retrieval code to the recently published HST/STIS reflection spectrum, and also to the dayside thermal emission spectrum in light of new Spitzer/IRAC measurements, as well as our own re-analysis of the HST/NICMOS data. We first use the STIS data to place some constraints on the nature of clouds on HD 189733b and explore solution degeneracy between different cloud properties and the abundance of Na in the atmosphere; as already noted in previous work, absorption due to Na plays a significant role in determining the shape of the reflection spectrum. We then perform a new retrieval of the temperature profile and abundances of H2O, CO2, CO, and CH4 from the dayside thermal emission spectrum. Finally, we investigate the effect of including cloud in the model on this retrieval process. We find that the current quality of data does not warrant the extra complexity introduced by including cloud in the model; however, future data are likely to be of sufficient resolution and signal-to-noise that a more complete model, including scattering particles, will be required. Title: In situ Probe Science at Saturn Authors: Atkinson, D. H.; Mousis, O.; Lunine, J. I.; Simon-Miller, A. A.; Atreya, S. K.; Brinckerhoff, W.; Colaprete, A.; Coustenis, A.; Fletcher, L. N.; Guillot, T.; Lebreton, J. -P.; Mahaffy, P.; Orton, G. S.; Reh, K.; Spilker, L. J.; Spilker, T. R.; Webster, C. Bibcode: 2014EPSC....9...12A Altcode: A fundamental goal of solar system exploration is to understand the origin of the solar system, the initial stages, conditions, and processes by which the solar system formed, how the formation process was initiated, and the nature of the interstellar seed material from which the solar system was born. Key to understanding solar system formation and subsequent dynamical and chemical evolution is the origin and evolution of the giant planets and their atmospheres. Several theories have been put forward to explain the process of solar system formation, and the origin and evolution of the giant planets and their atmospheres. Each theory offers quantifiable predictions of the abundances of noble gases He, Ne, Ar, Kr, and Xe, and abundances of key isotopic ratios 4He/3He, D/H, 15N/14N, 18O/16O, and 13C/12C. Detection of certain disequilibrium species, diagnostic of deeper internal processes and dynamics of the atmosphere, would also help discriminate between competing theories. Measurements of the critical abundance profiles of these key constituents into the deeper well-mixed atmosphere must be complemented by measurements of the profiles of atmospheric structure and dynamics at high vertical resolution and also require in situ exploration. The atmospheres of the giant planets can also serve as laboratories to better understand the atmospheric chemistries, dynamics, processes, and climates on all planets including Earth, and offer a context and provide a ground truth for exoplanets and exoplanetary systems. Additionally, Giant planets have long been thought to play a critical role in the development of potentially habitable planetary systems. In the context of giant planet science provided by the Galileo, Juno, and Cassini missions to Jupiter and Saturn, a small, relatively shallow Saturn probe capable of measuring abundances and isotopic ratios of key atmospheric constituents, and atmospheric structure including pressures, temperatures, dynamics, and cloud locations and properties not accessible by remote sensing can serve to test competing theories of solar system and giant planet origin, chemical, and dynamical evolution. Title: Cycle 23 Variation in Solar Flare Productivity Authors: Hudson, Hugh; Fletcher, Lyndsay; McTiernan, Jim Bibcode: 2014SoPh..289.1341H Altcode: 2014arXiv1401.6474H The NOAA listings of solar flares in cycles 21 - 24, including the GOES soft X-ray magnitudes, enable a simple determination of the number of flares each flaring active region produces over its lifetime. We have studied this measure of flare productivity over the interval 1975 - 2012. The annual averages of flare productivity remained approximately constant during cycles 21 and 22, at about two reported M- or X-flares per region, but then increased significantly in the declining phase of cycle 23 (the years 2004 - 2005). We have confirmed this by using the independent RHESSI flare catalog to check the NOAA events listings where possible. We note that this measure of solar activity does not correlate with the solar cycle. The anomalous peak in flare productivity immediately preceded the long solar minimum between cycles 23 and 24. Title: Monitoring Jovian Dynamics Using Maps of NH3 and PH3 Authors: Encrenaz, T.; Greathouse, T.; Drossart, P.; Fouchet, T.; Janssen, M.; Gulkis, S.; Orton, G.; Fletcher, L.; Giles, R. Bibcode: 2014EPSC....9..240E Altcode: Phosphine and ammonia are important tracers of Jovian tropospheric dynamics, but their vertical distributions are still poorly known. This information will be needed for the analysis of the radio and infrared data of the JUNO mission in 2016. We have started an observing campaign to obtain 3D maps of NH3 and PH3 in the 0.1-5 bar pressure range, by using TEXES/IRTF and selecting 3 spectral ranges (at 4.65, 8.9 and 10.5 microns) that probe 3 different pressure levels. The first data (Feb. 2014) allow us to map NH3 and PH3 at low latitudes. We plan to continue this campaign to obtain a full latitude and longitude coverage and to improve the sensitivity. Title: Seasonal Evolution of Saturn's Polar Atmosphere from a Decade of Cassini/CIRS Observations Authors: Fletcher, L. N.; Sinclair, J. A.; Irwin, P. G. J.; Giles, R. S.; Orton, G. S.; Hesman, B. E.; Hurley, J.; Bjoraker, G. L.; Simon, A. A. Bibcode: 2014EPSC....9...62F Altcode: Saturn's polar regions are subjected to extreme insolation variations over its 29.5 year orbit due to the gas giant's 26-degree axial tilt, causing seasonal changes to the thermal structure, chemistry, dynamics and cloud properties of the polar environments. Cassini's high inclination orbits permit detailed scrutiny of Saturn's high latitudes in a dataset that now spans a decade (a third of a Saturn year, 2004-2014), five years either side of the northern spring equinox in 2009. Thermal infrared Cassini/CIRS spectra (7-16 μm) from all mission phases are inverted to determine the rate of change of polar temperatures, wind shears, tropospheric phosphine (as a tracer of vertical mixing) and stratospheric hydrocarbons (tracers of middle atmospheric circulation and chemistry). Cassini's unique vantage point allows us to track these parameters as the summer southern pole receded into autumn and the winter northern pole emerged into spring sunlight. Results show the most rapid changes to temperature and composition occurring poleward of 70o in each hemisphere, in excess of expectations from simple radiative climate models. Small cyclonic vortices persist at both poles throughout theCassini mission, while the broad stratospheric vortices are seasonally variable. The signature of the northern hexagon is still present in the tropospheric thermal structure. At the time of writing, an infraredbright polar vortex is beginning to emerge at the northern spring pole, consistent with the historical record of Saturn observations from the 1980s (previous northern spring, [4]). Title: Long-term variability of temperatures and clouds in Saturn from ground-based observations of thermal emission Authors: Orton, G.; Fletcher, L.; Sinclair, J.; Yanamandra-Fisher, P.; Greathouse, T.; Momary, T.; Fujiyoshi, T.; Aguilar, I. Bibcode: 2014EPSC....9..681O Altcode: We report the results of long-term studies of thermal emission from the atmosphere of Saturn using ground-based imaging covering 1990 to the present. Both seasonal and non-seasonal effects have been detected in its atmosphere. Seasonal effects are most pronounced and indicate a variance from radiative climate model results that is consistent with an additional source of stratospheric heating other than gaseous absorption of sunlight. Associated with the seasonal variations is the establishment of warm polar vortices in the stratosphere toward late spring and early summer, with the anticipation of such a vortex appearing imminently in Saturn's north polar region. Non-seasonal effects include a variation of low-latitude thermal waves, initially identified as consistent with a semi-annual oscillation, although recent observations indicate a variation from that behavior. Slowly moving zonal thermal waves have been detected irregularly; they have been most prominent in Saturn's southern mid-latitudes. Deep atmospheric cloud structure has shown consistent zonal-mean structure from 1995 to the present; however it has been marked by substantial discrete opaque ("cold") features. The great springtime storm of 2010-2011 produced substantial perturbations of both atmospheric temperatures and deep cloud structure. Title: Interpretation of the 14N/15N ratio measured in Saturn's ammonia Authors: Mousis, O.; Lunine, J. I.; Fletcher, L. N.; Mandt, K. E.; Gautier, D.; Atreya, S. Bibcode: 2014EPSC....9..425M Altcode: The recent derivation of a 1-sigma lower limit for the 14N/15N ratio in Saturn's ammonia, which is found to be ~500 [1], prompts us to revise models of Saturn's formation using as constraints the abundances of heavy elements inferred in its atmosphere. This lower limit is found consistent with the 14N/15N ratio (~435) measured by the Galileo probe at Jupiter and implies that the two giant planets were essentially formed from the same nitrogen reservoir in the nebula, which is N2 [1]. However, in contrast with Jupiter whose C and N enrichments are uniform, carbon is more than twice enriched in Saturn's atmosphere compared to nitrogen. This non-uniform enrichment at Saturn, considered with the recent derivation of a lower limit for the 14N/15N ratio, challenges the formation models elaborated so far. Here we propose an alternative formation scenario that may explain all these properties together Title: Scientific Rationale and Concepts for an In Situ Saturn Probe Authors: Mousis, O.; Atkinson, D.; Atreya, S.; Coustenis, A.; Fletcher, L. N.; Gautier, D.; Guillot, T.; Hueso, R.; Lebreton, J. -P.; Lunine, J. I.; Marty, B.; Reh, K.; Venkatapathy, E.; Waite, J. H.; Wurz, P. Bibcode: 2014EPSC....9..437M Altcode: We summarize the science case for in situ measurements at Saturn and discuss the possible mission concepts that would be consistent with the constraints of ESA M-class missions. Title: Possible Concepts for an In Situ Saturn Probe Mission Authors: Coustenis, A.; Lebreton, J. -P.; Mousis, O.; Atkinson, D. H.; Lunine, J. I.; Reh, K.; Fletcher, L.; Simon-Miller, A.; Atreya, S. K.; Brinckerhoff, W.; Cavalié, T.; Colaprete, A.; Gautier, D.; Guillot, T.; Mahaffy, P.; Marty, B.; Morse, A. D.; Sims, J.; Spilker, T.; Spilker, L.; Webster, C.; Waite, J. H.; Wurz, P. Bibcode: 2014LPI....45.1244C Altcode: We present Saturn entry probe concepts for in situ exploration informing us on the formation history of our solar system and the planet's atmosphere processes. Title: Europa's Water Vapor Plumes: Discovery with HST and Plans for JUICE-UVS Observations Authors: Retherford, K. D.; Roth, L.; Saur, J.; Gladstone, G. R.; Nimmo, F.; McGrath, M. A.; Feldman, P. D.; Strobel, D. F.; Greathouse, T. K.; Davis, M. W.; Steffl, A. J.; Spencer, J. R.; Bagenal, F.; Fletcher, L.; Juice-UVS Team Bibcode: 2014LPI....45.1639R Altcode: Discovery of water vapor plumes on Europa obtained with HST, and updated plans for JUICE Ultraviolet Spectrograph (UVS) observations. Title: Physical Properties of White-light Sources in the 2011 February 15 Solar Flare Authors: Kerr, G. S.; Fletcher, L. Bibcode: 2014ApJ...783...98K Altcode: 2014arXiv1401.4877K White-light flares (WLFs) are observational rarities, making them understudied events. However, optical emission is a significant contribution to flare energy budgets and the emission mechanisms responsible could have important implications for flare models. Using Hinode SOT optical continuum data taken in broadband red, green, and blue filters, we investigate WL emission from the X2.2 flare SOL2011-02-15T01:56:00. We develop a technique to robustly identify enhanced flare pixels and, using a knowledge of the RGB filter transmissions, determined the source color temperature and effective temperature. We investigated two idealized models of WL emission—an optically thick photospheric source, and an optically thin chromospheric slab. Under the optically thick assumption, the color temperature and effective temperature of flare sources in sunspot umbra and penumbra were determined as a function of time and position. Values in the range of 5000-6000 K were found, corresponding to a blackbody temperature increase of a few hundred kelvin. The power emitted in the optical was estimated at ~1026 erg s-1. In some of the WL sources the color and blackbody temperatures are the same within uncertainties, consistent with a blackbody emitter. In other regions this is not the case, suggesting that some other continuum emission process is contributing. An optically thin slab model producing hydrogen recombination radiation is also discussed as a potential source of WL emission; it requires temperatures in the range 5500-25,000 K, and total energies of ~1027 erg s-1. Title: Exploring the diversity of Jupiter-class planets Authors: Fletcher, L. N.; Irwin, P. G. J.; Barstow, J. K.; de Kok, R. J.; Lee, J. -M.; Aigrain, S. Bibcode: 2014RSPTA.37230064F Altcode: No abstract at ADS Title: Scientific Rationale of a Saturn Probe Mission Authors: Mousis, O.; Fletcher, L. N.; Lebreton, J. -P.; Wurz, P.; Cavalié, T.; Coustenis, A.; Atkinson, D. H.; Atreya, S.; Gautier, D.; Guillot, T.; Lunine, J. I.; Marty, B.; Morse, A. D.; Rey, K. R.; Simon-Miller, A.; Spilker, T.; Waite, J. H. Bibcode: 2014LPI....45.1261M Altcode: We describe the main scientific goals to be addressed by future in situ exploration of Saturn. Title: Jupiter Icy Moons Explorer (JUICE): Science Objectives, Mission and Instruments Authors: Plaut, J. J.; Barabash, S.; Bruzzone, L.; Dougherty, M.; Erd, C.; Fletcher, L.; Gladstone, R.; Grasset, O.; Gurvits, L.; Hartogh, P.; Hussmann, H.; Iess, L.; Jaumann, R.; Langevin, Y.; Palumbo, P.; Piccioni, G.; Titov, D.; Wahlund, J. -E. Bibcode: 2014LPI....45.2717P Altcode: The JUpiter ICy Moons Explorer (JUICE) is an ESA mission that will fly by and observe the icy moons Europa, Ganymede, and Callisto, and finally orbit Ganymede. Title: In Situ Probe Science at Saturn Authors: Atkinson, D. H.; Lunine, J. I.; Simon-Miller, A. A.; Atreya, S. K.; Brinckerhoff, W.; Colaprete, A.; Coustenis, A.; Fletcher, L. N.; Guillot, T.; Lebreton, J. -P.; Mahaffy, P.; Mousis, O.; Orton, G. S.; Reh, K.; Spilker, L. J.; Spilker, T. R.; Webster, C. Bibcode: 2014LPI....45.1377A Altcode: A shallow Saturn probe measuring key atmospheric abundances and isotope ratios can test competing theories of solar system and giant planet formation. Title: Europa's Water Vapor Plumes: The Potential for Discovery with JUICE-UVS Observations Authors: Retherford, K. D.; Roth, L.; Saur, J.; Gladstone, G. R.; Nimmo, F.; McGrath, M. A.; Feldman, P. D.; Strobel, D. F.; Steffl, A. J.; Greathouse, T. K.; Spencer, J. R.; Bagenal, F.; Fletcher, L. N. Bibcode: 2014LPICo1774.4033R Altcode: Far-UV auroral imaging and stellar occultation techniques are able to identify whether water vapor plumes exist on Europa. Detailed observation plans for the JUICE Ultraviolet Spectrograph (UVS) are reported along with recent HST auroral imaging. Title: The first submillimeter observation of CO in the stratosphere of Uranus Authors: Cavalié, T.; Moreno, R.; Lellouch, E.; Hartogh, P.; Venot, O.; Orton, G. S.; Jarchow, C.; Encrenaz, T.; Selsis, F.; Hersant, F.; Fletcher, L. N. Bibcode: 2014A&A...562A..33C Altcode: 2013arXiv1311.2458C Context. Carbon monoxide (CO) has been detected in all giant planets and its origin is both internal and external in Jupiter and Neptune. Despite its first detection in Uranus a decade ago, the magnitude of its internal and external sources remains unconstrained.
Aims: We targeted CO lines in Uranus in the submillimeter range to constrain its origin.
Methods: We recorded the disk-averaged spectrum of Uranus with very high spectral resolution at the frequencies of CO rotational lines in the submillimeter range in 2011-2012. We used empirical and diffusion models of the atmosphere of Uranus to constrain the origin of CO. We also used a thermochemical model of its troposphere to derive an upper limit on the oxygen-to-hydrogen (O/H) ratio in the deep atmosphere of Uranus.
Results: We have detected the CO(8-7) rotational line for the first time with Herschel-HIFI. Both empirical and diffusion models results show that CO has an external origin. An empirical profile in which CO is constant above the 100 mbar level with a mole fraction of 7.1-9.0 × 10-9, depending on the adopted stratospheric thermal structure, reproduces the data. Sporadic and steady source models cannot be differentiated with our data. Taking the internal source model upper limit of a mole fraction of 2.1 × 10-9 we find, based on our thermochemical computations, that the deep O/H ratio of Uranus is less than 500 times solar.
Conclusions: Our work shows that the average mole fraction of CO decreases from the stratosphere to the troposphere and thus strongly advocates for an external source of CO in Uranus. Photochemical modeling of oxygen species in the atmosphere of Uranus and more sensitive observations are needed to reveal the nature of the external source.

Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. Title: JUICE: The ESA Mission to Study Habitability of the Jovian Icy Moons Authors: Titov, D.; Barabash, S.; Bruzzone, L.; Dougherty, M.; Duvet, L.; Erd, C.; Fletcher, L.; Gladstone, R.; Grasset, O.; Gurvits, L.; Hartogh, P.; Hussmann, H.; Iess, L.; Jaumann, R.; Langevin, Y.; Palumbo, P.; Piccioni, G.; Wahlund, J. -E. Bibcode: 2014LPICo1774.4035T Altcode: The presentation will give an overview of the ESA's JUICE (JUpiter ICy moons Explorer) mission to the Jovian system, its science scenario, observation strategy, and the newly selected payload. Title: Line-by-line analysis of Neptune's near-IR spectrum observed with Gemini/NIFS and VLT/CRIRES Authors: Irwin, P. G. J.; Lellouch, E.; de Bergh, C.; Courtin, R.; Bézard, B.; Fletcher, L. N.; Orton, G. S.; Teanby, N. A.; Calcutt, S. B.; Tice, D.; Hurley, J.; Davis, G. R. Bibcode: 2014Icar..227...37I Altcode: New line data describing the absorption of CH4 and CH3D from 1.26 to 1.71 μm (WKMC-80K, Campargue, A., Wang, L., Mondelain, D., Kassi, S., Bézard, B., Lellouch, E., Coustenis, A., de Bergh, C., Hirtzig, M., Drossart, P. [2012]. Icarus 219, 110-128) have been applied to the analysis of Gemini-N/NIFS observations of Neptune made in 2009 and VLT/CRIRES observations made in 2010. The new line data are found to greatly improve the fit to the observed spectra and present a considerable advance over previous methane datasets. The improved fits lead to an empirically derived wavelength-dependent correction to the scattering properties of the main observable cloud deck at 2-3 bars that is very similar to the correction determined for Uranus' lower cloud using the same line dataset by Irwin et al. (Irwin, P.G.J., de Bergh, C., Courtin, R., Bézard, B., Teanby, N.A., Davis, G.R., Fletcher, L.N., Orton, G.S., Calcutt, S.B., Tice, D., Hurley, J. [2012]. Icarus 220, 369-382). By varying the abundance of CH3D in our simulations, analysis of the Gemini/NIFS observations leads to a new determination of the CH3D/CH4 ratio for Neptune of 3.0-0.9+1.0×10-4, which is smaller than previous determinations, but is identical (to within error) with the CH3D/CH4 ratio of 2.9-0.5+0.9×10-4 derived by a similar analysis of Gemini/NIFS observations of Uranus made in the same year. Thus it appears that the atmospheres of Uranus and Neptune have an almost identical D/H ratio, which suggests that the icy planetisimals forming these planets came from the same source reservoir, or a reservoir that was well-mixed at the locations of ice giant formation, assuming complete mixing between the atmosphere and interior of both these planets. VLT/CRIRES observations of Neptune have also been analysed with the WKMC-80K methane line database, yielding very good fits, with little evidence for missing absorption features. The CRIRES spectra indicate that the mole fraction of CO at the 2-3 bar level must be substantially less than its estimated stratospheric value of 1 × 10-6, which suggests that the predominant source of CO in Neptune's atmosphere is external, through the influx of micrometeorites and comets, although these data cannot rule out an additional internal source. Title: Colors of Jupiter's large anticyclones and the interaction of a Tropical Red Oval with the Great Red Spot in 2008 Authors: Sánchez-Lavega, A.; Legarreta, J.; García-Melendo, E.; Hueso, R.; Pérez-Hoyos, S.; Gómez-Forrellad, J. M.; Fletcher, L. N.; Orton, G. S.; Simon-Miller, A.; Chanover, N.; Irwin, P.; Tanga, P.; Cecconi, M. Bibcode: 2013JGRE..118.2537S Altcode: nature and mechanisms producing the chromophore agents that provide color to the upper clouds and hazes of the atmospheres of the giant planets are largely unknown. In recent times, the changes in red coloration that have occurred in large- and medium-scale Jovian anticyclones have been particularly interesting. In late June and early July 2008, a particularly color intense tropical red oval interacted with the Great Red Spot (GRS) leading to the destruction of the tropical red oval and cloud dispersion. We present a detailed study of the tropical vortices, usually white but sometimes red, and a characterization of their color spectral signatures and dynamics. From the spectral reflectivity in methane bands we study their vertical cloud structure compared to that of the GRS and BA. Using two spectral indices we found a near correlation between anticyclones cloud top altitudes and red color. We present detailed observations of the interaction of the red oval with the GRS and model simulations of the phenomena that allow us to constrain the relative vertical extent of the vortices. We conclude that the vertical cloud structure, vertical extent, and dynamics of Jovian anticyclones are not the causes of their coloration. We propose that the red chromophore forms when background material (a compound or particles) is entrained by the vortex, transforming into red once inside the vortex due to internal conditions, exposure to ultraviolet radiation, or to the mixing of two chemical compounds that react inside the vortex, confined by a potential vorticity ring barrier. Title: Variation of solar oscillation frequencies in solar cycle 23 and their relation to sunspot area and number (Corrigendum) Authors: Jain, R.; Tripathy, S. C.; Watson, F. T.; Fletcher, L.; Jain, K.; Hill, F. Bibcode: 2013A&A...560C...1J Altcode: No abstract at ADS Title: Constraining the Depth of Saturn's Zonal Winds by Measuring Thermal and Gravitational Signals Authors: Liu, J.; Schneider, T.; Fletcher, L. N. Bibcode: 2013AGUFM.P21C1748L Altcode: In 2016, NASA's Cassini spacecraft will orbit Saturn in highly elliptical orbits and will measure Saturn's gravitational and thermal signals at the end of its mission. This provides an opportunity to constrain the structure of the zonal winds on the planet. Here we make predictions of what Cassini will measure based on dynamical arguments that constrain the flow and on already available observations. There are strong dynamical constraints on the zonal winds and the associated entropy and density distributions on Saturn. Due to Saturn's strong internal heat flux, rapid rotation and negligible atmospheric viscosity, convective motions are constrained to be primarily along surfaces of constant angular momentum; they approximately homogenize entropy along the spin axis. Using the assumption that in the interior, entropy is homogenized in the direction of the spin axis, but not perpendicular to it, we determine the zonal winds and the associated thermal and gravitational signals by combing the equation of state of the atmosphere, the observed zonal winds at the cloud level, and plausible assumptions about the strength of the magnetohydrodynamic (MHD) drag that zonal winds experience in the deep interior. A difficulty arises because Saturn's observed zonal winds are not well defined because the planetary rotation rate is uncertain. Using a range of plausible estimates of the rotation rate, we find the observed zonal winds on Saturn likely extend deeply into Saturn (to a depth between about 0.65 RS and 0.85 RS, with Saturn's radius RS, corresponding to 1 Mbar and 0.2 Mbar). Material properties of Saturn (the equation of state) constrain zonal winds with strengths similar to the cloud levels winds to be confined only within the outer few percent of Saturn's radius, irrespective of Saturn's rotation rate and the depth of MHD drag. The theoretically derived meridional equator-to-pole temperature contrasts in thermal wind balance with the zonal winds increase with depth and reach 1~2 K at 1 bar and 2~4 K at 5 bar. They would be much larger if the zonal winds were shallow, but already available thermal observations by Cassini CIRS rule out very shallow flows: zonal winds relative to System III rotation rate have to extend deeper than 5000 bar (0.97 RS). Otherwise the associated equator-to-pole contrast (O(10K) at 1 bar) would exceed the observed values. The gravitational signal corresponding to deeply penetrating zonal winds are much larger than those that would be associated with shallow zonal winds. Combining the thermal signals with the gravitational signals of the zonal winds, the penetration depths of the zonal winds relative to different rotation rates can be determined by Cassini at the end of its mission. Title: Impact flux on Jupiter: From superbolides to large-scale collisions Authors: Hueso, R.; Pérez-Hoyos, S.; Sánchez-Lavega, A.; Wesley, A.; Hall, G.; Go, C.; Tachikawa, M.; Aoki, K.; Ichimaru, M.; Pond, J. W. T.; Korycansky, D. G.; Palotai, C.; Chappell, G.; Rebeli, N.; Harrington, J.; Delcroix, M.; Wong, M.; de Pater, I.; Fletcher, L. N.; Hammel, H.; Orton, G. S.; Tabe, I.; Watanabe, J.; Moreno, J. C. Bibcode: 2013A&A...560A..55H Altcode: Context. Regular observations of Jupiter by a large number of amateur astronomers have resulted in the serendipitous discovery of short bright flashes in its atmosphere, which have been proposed as being caused by impacts of small objects. Three flashes were detected: one on June 3, 2010, one on August 20, 2010, and one on September 10, 2012.
Aims: We show that the flashes are caused by impacting objects that we characterize in terms of their size, and we study the flux of small impacts on Jupiter.
Methods: We measured the light curves of these atmospheric airbursts to extract their luminous energy and computed the masses and sizes of the objects. We ran simulations of impacts and compared them with the light curves. We analyzed the statistical significance of these events in the large pool of Jupiter observations.
Results: All three objects are in the 5-20 m size category depending on their density, and they released energy comparable to the recent Chelyabinsk airburst. Model simulations approximately agree with the interpretation of the limited observations. Biases in observations of Jupiter suggest a rate of 12-60 similar impacts per year and we provide software tools for amateurs to examine the faint signature of impacts in their data to increase the number of detected collisions.
Conclusions: The impact rate agrees with dynamical models of comets. More massive objects (a few 100 m) should impact with Jupiter every few years leaving atmospheric dark debris features that could be detectable about once per decade. Title: Models for Temperature and Composition in Uranus from Spitzer, Herschel and Ground-Based Infrared through Millimeter Observations Authors: Orton, G. S.; Fletcher, L. N.; Feuchtgruber, H.; Lellouch, E.; Moreno, R.; Encrenaz, T.; Hartogh, P.; Jarchow, C.; Swinyard, B.; Moses, J. I.; Burgdorf, M. J.; Hammel, H. B.; Line, M. R.; Sandell, G.; Dowell, C. D. Bibcode: 2013AGUFM.P21B1729O Altcode: Photometric and spectroscopic observations of Uranus were combined to create self-consistent models of its global-mean temperature profile, bulk composition, and vertical distribution of gases. These were derived from a suite of spacecraft and ground-based observations that includes the Spitzer IRS, and the Herschel HIFI, PACS and SPIRE instruments, together with ground-based observations from UKIRT and CSO. Observations of the collision-induced absorption of H2 have constrained the temperature structure in the troposphere; this was possible up to atmospheric pressures of ~2 bars. Temperatures in the stratosphere were constrained by H2 quadrupole line emission. We coupled the vertical distribution of CH4 in the stratosphere of Uranus with models for the vertical mixing in a way that is consistent with the mixing ratios of hydrocarbons whose abundances are influenced primarily by mixing rather than chemistry. Spitzer and Herschel data constrain the abundances of CH3, CH4, C2H2, C2H6, C3H4, C4H2, H2O and CO2. At millimeter wavelengths, there is evidence that an additional opacity source is required besides the H2 collision-induced absorption and the NH3 absorption needed to match the microwave spectrum; this can reasonably (but not uniquely) be attributed to H2S. These models will be made more mature by consideration of spatial variability from Voyager IRIS and more recent spatially resolved imaging and mapping from ground-based observatories. The model is of ';programmatic' interest because it serves as a calibration source for Herschel instruments, and it provides a starting point for planning future spacecraft investigations of the atmosphere of Uranus. Title: The Evolution of Hydrocarbon Compounds in Saturn's Stratosphere During the 2010 Northern Storm Authors: Hesman, B. E.; Bjoraker, G. L.; Achterberg, R. K.; Sada, P. V.; Jennings, D. E.; Lunsford, A. W.; Sinclair, J.; Romani, P. N.; Boyle, R.; Fletcher, L. N.; Irwin, P. Bibcode: 2013AGUFMSM21C2205H Altcode: The massive eruption at 40N (planetographic latitude) in December 2010 has produced significant and long-lived changes in temperature and species abundances in Saturn's northern hemisphere (Hesman et al. 2012a, Fletcher et al. 2012). The northern storm region has been observed on many occasions between January 2011 and June of 2012 by Cassini's Composite Infrared Spectrometer (CIRS). In this time period, temperatures in regions referred to as 'beacons' (warm regions in the stratosphere at certain longitudes in the storm latitude) became significantly warmer than pre-storm values of 140K. In this period hydrocarbon emission greatly increased; however, this increased emission could not be attributed due to the temperature changes alone for many of these species (Hesman et al. 2012b, Bjoraker et al 2012). The unique nature of the stratospheric beacons also resulted in the detection of ethylene (C2H4) using CIRS. These beacon regions have also led to the identification of rare hydrocarbon species such as C4H2 and C3H4 in the stratosphere. These species are all expected from photochemical processes in the stratosphere, however high temperatures, unusual chemistry, or dynamics are enhancing these species. The exact cause of these enhancements is still under investigation. Ground-based observations were performed using the high-resolution spectrometer Celeste in May 2011 to confirm the CIRS detection of C2H4 and to study its spectral signatures at higher spectral resolution. In order to follow the evolution of its emission further observations were performed in July 2011 and March 2012. These observations are being used in conjunction with the CIRS observations to investigate the source of the approximately 100-fold increase of ethylene in the stratospheric beacon. The time evolution of hydrocarbon emission from C2H2, C2H4, C2H6, C3H4, and C4H2 in Saturn's Northern Storm beacon regions will be discussed. References: Bjoraker, G., B.E. Hesman, R.K. Achterberg, P.N. Romani. 2012, 'The Evolution of Hydrocarbons in Saturn's Northern Storm Region,' AAS DPS Conference, Vol. 44, #403.05. Fletcher, L.N. et al. 2012, 'The Origin and Evolution of Saturn's 2011-2012 Stratospheric Vortex,' Icarus, 221, 560-586. Hesman, B.E. et al. 2012a, 'Elusive Ethylene Detected in Saturn's Northern Storm Region,' The Astrophysical Journal, 760, 24-30. Hesman, B.E. et al. 2012b, 'Ethylene Emission in the Aftermath of Saturn's 2010 Northern Storm,' AAS DPS Conference, Vol. 44, #403.06. Title: The optical transmission spectrum of the hot Jupiter HAT-P-32b: clouds explain the absence of broad spectral features? Authors: Gibson, N. P.; Aigrain, S.; Barstow, J. K.; Evans, T. M.; Fletcher, L. N.; Irwin, P. G. J. Bibcode: 2013MNRAS.436.2974G Altcode: 2013MNRAS.tmp.2486G; 2013arXiv1309.6998G We report Gemini-North Gemini Multi-Object Spectrograph observations of the inflated hot Jupiter HAT-P-32b during two primary transits. We simultaneously observed two comparison stars and used differential spectrophotometry to produce multiwavelength light curves. `White' light curves and 29 `spectral' light curves were extracted for each transit and analysed to refine the system parameters and produce transmission spectra from 520 to 930 nm in ≈14 nm bins. The light curves contain time-varying white noise as well as time-correlated noise, and we used a Gaussian process model to fit this complex noise model. Common mode corrections derived from the white light-curve fits were applied to the spectral light curves which significantly improved our precision, reaching typical uncertainties in the transit depth of ∼2 × 10-4, corresponding to about half a pressure scale height. The low-resolution transmission spectra are consistent with a featureless model, and we can confidently rule out broad features larger than about one scale height. The absence of Na/K wings or prominent TiO/VO features is most easily explained by grey absorption from clouds in the upper atmosphere, masking the spectral features. However, we cannot confidently rule out clear atmosphere models with low abundances (∼10-3 solar) of TiO, VO or even metal hydrides masking the Na and K wings. A smaller scale height or ionization could also contribute to muted spectral features, but alone are unable to account for the absence of features reported here. Title: Europa's Atmosphere and Aurora: Recent Advances from HST-STIS and Plans for Plume Searches with JUICE-UVS Authors: Retherford, K. D.; Gladstone, R.; Roth, L.; McGrath, M. A.; Saur, J.; Feldman, P. D.; Steffl, A. J.; Strobel, D. F.; Greathouse, T. K.; Spencer, J. R.; Bagenal, F.; Fletcher, L. N.; Eterno, J. S. Bibcode: 2013AGUFM.P53A1838R Altcode: Space Telescope Imaging System (STIS) images of Europa's neutral oxygen 130.4 nm and 135.6 nm emissions contain a wealth of information about the molecular oxygen atmosphere, discovered using previous Hubble far-UV observations. Europa's magnetospheric plasma interaction generates auroral emissions, which exhibit a morphology that has been difficult to interpret. Recent observations in Nov. & Dec. 2012 allow a new understanding of how Jupiter's magnetic field orientation and relation to the plasma sheet control the emission variability, yet explanations for this general behavior, including the likely role of ocean-induced magnetic fields and possible local atmospheric density enhancements, remain incomplete (cf. Roth et al. this meeting). NASA's Ultraviolet Spectrograph (UVS) instrument contribution to the ESA-led Jupiter Icy Moons Explorer (JUICE) mission will obtain excellent imaging of these atmospheric and auroral emissions from Europa during two flybys currently planned, with the objective of investigating these and other unanswered questions. UVS's stellar occultation technique will be used to characterize Europa's atmosphere structure and composition and to also search for local enhancements created by plumes. This stellar occultation technique, demonstrated by Cassini-UVIS at Enceladus, has the benefit of being useful at relatively large distances (several 10's of Jupiter radii) as well as during the Europa flyby sequences (several 10's of Europa radii). A robust search for plumes is planned in JUICE's first year at Jupiter to provide a roughly 30-degree grid of global coverage, followed by focused targeting of likely plumes/active-regions during early and late stages of the flyby sequences. High spatial resolution limb imaging is also planned near closest approaches, which could directly image plume gases in a manner analogous with plume aurora imaging of Io. A UV spectrograph on the planned Europa Clipper mission could perform an even more robust search for such currently active geological sites with connectivity to subsurface liquid water. Title: Photochemistry in Saturn's Ring-Shadowed Atmosphere: Of Venetian Blinds, Atmospheric Molecules and Observations Authors: Edgington, S. G.; Atreya, S. K.; Wilson, E. H.; Baines, K. H.; West, R. A.; Bjoraker, G. L.; Fletcher, L. N.; Momary, T. Bibcode: 2013AGUFMSM21C2204E Altcode: Cassini has been orbiting Saturn for over nine years. During this epoch, the ring shadow has moved from covering a relatively large portion of the northern hemisphere to covering a large swath south of the equator and continues to move southward. At Saturn Orbit Insertion in 2004, the ring plane was inclined by ~24 degrees relative to the Sun-Saturn vector. The projection of the B-ring onto Saturn reached as far as 40N along the central meridian (~52N at the terminator). At its maximum extent, the ring shadow can reach as far as 48N/S (~58N/S at the terminator). The net effect is that the intensity of both ultraviolet and visible sunlight penetrating into any particular latitude will vary depending on both Saturn's axis relative to the Sun and the optical thickness of each ring system. In essence, the rings act like venetian blinds. Our previous work [1] examined the variation of the solar flux as a function of solar inclination, i.e. ~8 year season at Saturn. Here, we report on the impact of the oscillating ring shadow on the photolysis and production rates of hydrocarbons in Saturn's stratosphere and upper troposphere, including acetylene, ethane, propane, and benzene. Beginning with methane, we investigate the impact on production and loss rates of the long-lived photochemical products leading to haze formation are examined at several latitudes over a Saturn year. Similarly, we assess its impact on phosphine abundance, a disequilibrium species whose presence in the upper troposphere is a tracer of convection processes in the deep atmosphere. Comparison to the corresponding rates for the clear atmosphere and for the case of Jupiter, where the variation of solar insolation due to tilt is known to be insignificant (~3 degree inclination), will be presented. We will present our ongoing analysis of Cassini's CIRS, UVIS, and VIMS datasets that provide an estimate of the evolving haze content of the northern hemisphere and we will begin to assess the implications for dynamical mixing. [1] Edgington, S.G., et al., 2012. Photochemistry in Saturn's Ring Shadowed Atmosphere: Modeling, Observations, and Preliminary Analysis. Bull. American. Astron. Soc., 38, 499 (#11.23). Title: Changes in Saturn's Zonal-Mean Tropospheric Structure After the 2010-2011 Northern Storm Authors: Achterberg, R. K.; Gierasch, P. J.; Conrath, B. J.; Fletcher, L. N.; Hesman, B. E.; Bjoraker, G. L.; Flasar, F. Bibcode: 2013AGUFMSM21C2203A Altcode: In early December 2010, a large convective storm erupted at approximately 40°N planetographic latitude on Saturn, lasting until early July 2011 (Sánchez-Lavega et al. 2012, Icarus, 220, 561-576). We use far-infrared (20μm - 200μm) data from the Composite Infrared Spectrometer (CIRS) on the Cassini spacecraft to determine the zonal-mean temperature and hydrogen para-fraction in Saturn's upper troposphere between approximately 200 and 800 mbar from observations taken before and after the large northern hemisphere storm in 2010-2011. During the storm, the latitude band between approximately 25°N and 45°N (planetographic latitude) warmed by about 3 K, while the hydrogen para-fraction decreased by about 0.04 over the same latitudes, at pressures greater than about 300 mbar. These changes occurred over the same latitude range as the disturbed cloud band seen in visible images. The decrease in hydrogen para-fraction is consistent with a strong convective plume advecting low para-fraction hydrogen upward from the several bar level, where the equilibrium para-fraction is 0.25, and the subsequent mixing of the low para-fraction hydrogen with the ambient atmosphere. Heat released from water condensation in the plume, or the conversion of ortho-hydrogen to para-hydrogen may then explain the observed temperature increase. The changes observed in the zonal-mean temperatures are roughly consistent with the changes in zonal winds seen by Sayanagi et al. (2013, Icarus, 223, 460-478) assuming geostrophic balance. Title: Oxygen Compounds in Saturn's Stratosphere During the 2010 Northern Storm Authors: Bjoraker, G. L.; Hesman, B. E.; Achterberg, R. K.; Jennings, D. E.; Romani, P. N.; Fletcher, L. N.; Irwin, P. Bibcode: 2013AGUFMSM21C2206B Altcode: The massive storm at 40N on Saturn that began in December 2010 has produced significant and long-lived changes in temperature and species abundances in the stratosphere throughout the northern hemisphere (Hesman et al. 2012a, Fletcher et al. 2012). The northern storm region has been observed on many occasions between January 2011 and January 2013 by Cassini's Composite Infrared Spectrometer (CIRS). In this time period, temperatures in regions referred to as 'beacons' (warm regions in the stratosphere at certain longitudes in the storm latitude) became significantly warmer than pre-storm values of 140K, peaking at 220K in May 2011 followed by gradual cooling. Hydrocarbon emission greatly increased over pre-storm values and then slowly decayed as the beacon cooled. Radiative transfer modeling has revealed that this increased emission is due to enhanced gas abundances for many of these species, rather than simply due to the temperature changes alone (Hesman et al. 2012b, Bjoraker et al 2012). In order to build a comprehensive picture of the changes to the stratosphere due to the 2010 northern storm we are now investigating the oxygen compounds in Saturn's stratosphere to determine if similar changes in these species were measured. The time evolution of stratospheric CO2 and H2O abundances in the beacon regions throughout 2011 and 2012 will be presented and compared with pre-storm measurements made in 2010. Title: Ground-Based Observations of the Aftermath of the 2010-2011 Great Northern Springtime Storm in Saturn (Invited) Authors: Orton, G. S.; Fletcher, L. N.; Fouchet, T.; Fujiyoshi, T.; Greathouse, T. K.; Momary, T.; Yanamandra-Fisher, P. A. Bibcode: 2013AGUFMSM14A..06O Altcode: For the first time, a suite of ground-based and spacecraft instruments were available to detect and characterize one of the rare giant convective storms erupting in Saturn's atmosphere. The storm that erupted on 2010 December 5 created an immense thermal and chemical perturbation of the atmosphere. Most of the perturbation of the visible cloud system had abated within a year of the initial eruption, but changes to the atmosphere were evident at thermal infrared wavelengths, and they continue to the present. Here we review the observations from ground-based stations that include NASA's Infrared Telescope Facility (IRTF) and the Subaru Telescope, both at the summit of Mauna Kea, as well as observations from ESO's Very Large Telescope. Evident in the 5-μm spectral window was the clearing of nearly all clouds around and above the 3-bar level of the atmosphere at the latitude of the primary storm. In the intervening two years, imaging in the same window by the IRTF NSFCam2 instrument shows that the cleared region remains prominent and is filling in with a pre-storm cloud cover only very slowly. Most unexpected was the generation of a stratospheric vortex of high temperatures, 'the beacon' (Fletcher et al. 2011 Science 332, 1413). This phenomenon also continues more than two years later and has been tracked using several mid-infrared imaging instruments: VISIR at the VLT, COMICS at Subaru, and MIRSI at the IRTF using moderate-band filters. More precise determination of its vertical distribution was made using the University of Texas Echelon Cross Echelle Spectrograph (TEXES) at the IRTF, targeting specific lines of CH4 and the H2 quadrupole. All of these measurements, taken in concert, show that the heated region of the stratosphere is diminishing in amplitude, expanding in longitude and slowly sinking in altitude. Title: The Impulsive Phase in Solar Flares: Recent Multi-wavelength Results and their Implications for Microwave Modeling and Observations Authors: Fletcher, Lyndsay; Simoes, Paulo J. A. Bibcode: 2013arXiv1311.7175F Altcode: This short paper reviews several recent key observations of the processes occurring in the lower atmosphere (chromosphere and photosphere) during flares. These are: evidence for compact and fragmentary structure in the flare chromosphere, the conditions in optical flare footpoints, step-like variations in the magnetic field during the flare impulsive phase, and hot, dense 'chromospheric' footpoints. The implications of these observations for microwaves are also discussed. Title: Implosion of Coronal Loops during the Impulsive Phase of a Solar Flare Authors: Simões, P. J. A.; Fletcher, L.; Hudson, H. S.; Russell, A. J. B. Bibcode: 2013ApJ...777..152S Altcode: 2013arXiv1309.7090S We study the relationship between implosive motions in a solar flare, and the energy redistribution in the form of oscillatory structures and particle acceleration. The flare SOL2012-03-09T03:53 (M6.4) shows clear evidence for an irreversible (stepwise) coronal implosion. Extreme-ultraviolet (EUV) images show at least four groups of coronal loops at different heights overlying the flaring core undergoing fast contraction during the impulsive phase of the flare. These contractions start around a minute after the flare onset, and the rate of contraction is closely associated with the intensity of the hard X-ray and microwave emissions. They also seem to have a close relationship with the dimming associated with the formation of the coronal mass ejection and a global EUV wave. Several studies now have detected contracting motions in the corona during solar flares that can be interpreted as the implosion necessary to release energy. Our results confirm this, and tighten the association with the flare impulsive phase. We add to the phenomenology by noting the presence of oscillatory variations revealed by Geostationary Operational Environmental Satellite soft X-rays (SXR) and spatially integrated EUV emission at 94 and 335 Å. We identify pulsations of ≈60 s in SXR and EUV data, which we interpret as persistent, semi-regular compressions of the flaring core region which modulate the plasma temperature and emission measure. The loop oscillations, observed over a large region, also allow us to provide rough estimates of the energy temporarily stored in the eigenmodes of the active-region structure as it approaches its new equilibrium. Title: Science goals and concepts of a Saturn probe for the future L2/L3 ESA call Authors: Schmider, F. -X.; Mousis, O.; Fletcher, L. N.; Altwegg, K.; André, N.; Blanc, M.; Coustenis, A.; Gautier, D.; Geppert, W. D.; Guillot, T.; Irwin, P.; Lebreton, J. -P.; Marty, B.; Sánchez-Lavega, A.; Waite, J. H.; Wurz, P. Bibcode: 2013sf2a.conf...65S Altcode: Comparative studies of the elemental enrichments and isotopic abundances measured on Saturn can provide unique insights into the processes at work within our planetary system and are related to the time and location of giant planet formation. In situ measurements via entry probes remain the only reliable, unambiguous method for determining the atmospheric composition from the thermosphere to the deep cloud-forming regions of their complex weather layers. Furthermore, in situ experiments can reveal the meteorological properties of planetary atmospheres to provide ``ground truth'' for orbital remote sensing. Following the orbital reconnaissance of the Galileo and Cassini spacecraft, and the single-point in situ measurement of the Galileo probe to Jupiter, we believe that an in situ measurement of Saturn's atmospheric composition should be an essential element of ESA's future cornerstone missions, providing the much-needed comparative planetology to reveal the origins of our outer planets. This quest for understanding the origins of our solar system and the nature of planetary atmospheres is in the heart of ESA's Cosmic Vision, and has vast implications for the origins of planetary systems around other stars. Title: The Ultraviolet Spectrograph (UVS) on ESA’s JUICE Mission Authors: Gladstone, Randy; Retherford, K.; Steffl, A.; Eterno, J.; Davis, M.; Versteeg, M.; Greathouse, T.; Araujo, M.; Walther, B.; Persson, K.; Persyn, S.; Dirks, G.; McGrath, M.; Feldman, P.; Bagenal, F.; Spencer, J.; Schindhelm, R.; Fletcher, L. Bibcode: 2013DPS....4521104G Altcode: The Jupiter Icy Moons Explorer (JUICE) was selected in May 2012 as the first L-class mission of ESA’s Cosmic Vision Program. JUICE will launch in 2022 on a 7.6-year journey to the Jovian system, including a Venus and multiple Earth gravity assists, before entering Jupiter orbit in January 2030. JUICE will study the entire Jovian system for 3.5 years, concentrating on Europa, Ganymede, and Callisto, with the last 10 months spent in Ganymede orbit. The Ultraviolet Spectrograph (UVS) on JUICE was jointly selected by NASA and ESA as part of its ~130 kg payload of 11 scientific instruments. UVS is the fifth in a series of successful ultraviolet imaging spectrographs (Rosetta-Alice, New Horizons Pluto-Alice, LRO-LAMP) and is largely based on the most recent of these, Juno-UVS. It observes photons in the 55-210 nm wavelength range, at moderate spectral and spatial resolution along a 7.5-degree slit. A main entrance “airglow port” (AP) is used for most observations (e.g., airglow, aurora, surface mapping, and stellar occultations), while a separate “solar port” (SP) allows for solar occultations. Another aperture door, with a small hole through the centre, is used as a “high-spatial-resolution port” (HP) for detailed observations of bright targets. Time-tagging (pixel list mode) and programmable spectral imaging (histogram mode) allow for observational flexibility and optimal data management. As on Juno-UVS, the effects of penetrating electron radiation on electronic parts and data quality are substantially mitigated through contiguous shielding, filtering of pulse height amplitudes, management of high voltage settings, and careful use of radiation-hard, flight-tested parts. The science goals of UVS are to: 1) explore the atmospheres, plasma interactions, and surfaces of the Galilean satellites; 2) determine the dynamics, chemistry, and vertical structure of Jupiter’s upper atmosphere from equator to pole; and 3) investigate the Jupiter-Io connection by quantifying energy and mass flow in the Io atmosphere, neutral clouds, and torus. Here we present the salient features of the UVS instrument and describe the science we plan to address. Title: Properties of Slowly Moving Thermal Waves in Saturn from Cassini CIRS and Ground-Based Thermal Observations from 2003 to 2009 Authors: Orton, Glenn S.; Fletcher, L. N.; Flasar, F.; Achterberg, R. K.; Yanamandra-Fisher, P. A.; Lewis, M.; Fujiyoshi, T.; Bell, J.; Christian, J.; Brown, S. K. Bibcode: 2013DPS....4531207O Altcode: Hemispherical maps of Saturn’s atmosphere made both by Cassini’s Composite Infrared Spectrometer (CIRS, 7-1000 µm) and ground-based mid-infrared observations (7-25 µm) were surveyed for the presence and properties of zonal thermal waves and their variability in time. The most inclusive CIRS surveys, FIRMAPs (15 cm-1 spectral resolution), covered the planet from the equator to either north or south pole, sweeping through the latitude range while the planet rotated beneath over its ~10-hour rotation. Ground-based observations were made at the Infrared Telescope Facility using the MIRSI instrument, the Very Large Telescope using VISIR and the Subaru Telescope using COMICS. We sampled spectral ranges dominated both by upper-tropospheric emission (80-200 mbar) and by stratospheric emission (0.5-3 mbar). We examined data that were taken between 2003 and Saturn’s spring equinox in 2009. During this time, the strongest waves were found between planetographic latitudes of 30° - 45°S and 0° - 30°N. Some low-wavelength components cover all 360° in longitude, similar to the slowly moving thermal waves in Jupiter’s atmosphere, but the strongest waves were found in “trains” that covered less than 180°. In 2005, tropospheric waves had a mean peak-to-peak variance that was the equivalent of temperature variability of about 1 K. Between 2005 and 2007, they had subsided to about 0.5 K. During and after 2008, they soared to over 3 K. During this entire period, similar waves in the northern hemisphere were never larger than 0.8 K. In the stratosphere, waves followed a similar time sequence, with southern hemisphere waves in 2005 reaching amplitudes as high as 3.5 K in brightness temperature, subsequently decreasing, then growing in 2008-2009 to over 5 K. Stratospheric waves in the northern hemisphere were nearly constant ~2 K, but with an instance of 6 K at one epoch in 2008. We were able to track the phase of some of the waves in the southern hemisphere, which moved about 0.5° of longitude per day retrograde with respect to System III. The phase of tropospheric and stratospheric waves appeared to be highly correlated with one another with little offset in longitudes but not with positions of atmospheric storms. Title: IRTF/TEXES observations of Saturn’s stratospheric beacon Authors: Fouchet, Thierry; Greathouse, T. K.; Richter, M. J.; Lacy, J.; Fletcher, L.; Spiga, A. Bibcode: 2013DPS....4550907F Altcode: On December 5th, 2010, a giant convective storm erupted in Saturn’s Northern Hemisphere as each Saturnian year at least since 1876. For the first time, a huge thermal and chemical stratospheric disturbance associated with this large convective event was detected from ground-based and Cassini observations (Fletcher et al. 2011). This stratospheric disturbance is named the beacon. Here, we present high spectral resolution observations of the beacon obtained by the Texas Echelon Cross Echelle Spectrograph (TEXES) mounted on the IRTF during 6 nights from July 15th, 2011 to July 20th, 2011. We targeted several different CH4 lines between 1230 and 1280 cm-1, probing the stratospheric temperature between 5 hPa and 0.05 hPa, and the H2 S(1) quadrupolar and collision-induced lines at 587 cm-1, probing the stratospheric temperature between 150 hPa and 5 hPa. The stratospheric temperatures are retrieved from the dataset using a forward radiative model coupled with a constrained linear inverse method. Within the core of the beacon the maximum temperature inferred from the data is 178K at 40°N, hence about 50K warmer than the mean temperature measured before the occurrence of the storm. However, the TEXES data unambiguously demonstrate that this warming is not vertically homogeneous but rather confined in a specific pressure range between 1-5 hPa, overhung by a cold layer between 0.1 and 1 hPa. This vertical behavior is evident from the CH4 line spectral profiles with the core of the lines in absorption and the wings in emission. Moreover, our data demonstrate that the altitude of the local temperature maximum increases northwards. We will present how this thermal structure can help deciphering the stratospheric heating sources. On the western side of the beacon, the stratospheric heating is concentrated at lower pressures, hence higher altitudes, than within the beacon, between 0.1 and 0.01 hPa. We interpret this structure as being caused by convective motions within the beacon, and westward advection associated with a vertical shear of stratospheric zonal winds. Title: Multi-wavelength Observations of Neptune’s Atmosphere Authors: de Pater, Imke; Fletcher, L.; Luszcz-Cook, S.; deBoer, D.; Butler, B.; Orton, G.; Sitko, M.; Hammel, H. Bibcode: 2013DPS....4531220D Altcode: We conducted a multi-wavelength observing campaign on Neptune between June and October, 2003. We used the 10-m Keck telescope at near- and mid-infrared wavelengths and the VLA at radio wavelengths. Near infrared images were taken in October 2003 in broad- and narrow-band filters between 1 and 2.5 micron, using the infrared camera NIRC2 coupled to the Keck Adaptive Optics system. At these wavelengths we detect sunlight reflected off clouds in the upper troposphere and lower stratosphere. As shown by various authors before, bright bands of discrete cloud features are visible between 20°S and 50°S and near 30°N, as well as several distinct bright cloud features near 70°S, and the south polar “dot”. Mid-infrared images were taken on September 5 and 6 (2003) using the Keck LWS system in atmospheric windows at 8, 8.9, 10.7, 11.7, 12.5, 17.65, 18.75 and 22 micron. At these wavelengths we detect thermal emission from Neptune’s stratosphere due to the presence of hydrocarbons, and from near the tropopause due to collision induced opacity by hydrogen. At all wavelengths the South polar region stands out as a bright spot. At 17 - 22 micron also the equatorial region is slightly enhanced in intensity. These characteristics are consistent with later imaging at similar wavelengths (Hammel et al. 2007; Orton et al. 2007). Microwave images were constructed from NRAO VLA data between 0.7 and 6.0 cm. At these wavelengths depths of several up to >50 bar are probed. An increase in brightness indicates decreased opacity of absorbers (e.g., NH3, H2S), since under such circumstances deep, and hence warm levels (adiabatic temperature-pressure profile), will be probed. The multi-wavelength observing campaign in 2003 was focused on obtaining images that probe different altitudes in Neptune’s atmosphere. Indeed, this set of data probes altitudes from about 0.1 mbar down to ~50 bar, and hence can be used to constrain the global atmospheric circulation in Neptune’s atmosphere. At the meeting we will show our results and interpretation of the findings. Title: Hydrocarbon and oxygen photochemistry on Uranus as revealed from Spitzer/IRS observations Authors: Moses, Julianne I.; Orton, G. S.; Fletcher, L. N.; Mainzer, A. K.; Hines, D. C.; Hammel, H. B.; Martin-Torres, J.; Burgdorf, M.; Merlet, C.; Line, M. R.; Poppe, A. Bibcode: 2013DPS....4531213M Altcode: Due to the very low atmospheric temperatures and hydrocarbon column abundances on Uranus, the planet appears very faint at mid-infrared wavelengths, making determinations of atmospheric composition difficult. The Spitzer Space Telescope Infrared Spectrometer (IRS) is two orders of magnitude more sensitive than previous space-based instruments, favoring the detection of faint molecular emission features from Uranus’ atmosphere (e.g., Burgdorf et al. 2006, Icarus 184, 634). Global-average Spitzer/IRS spectra acquired just days after the planet’s 2007 northern vernal equinox (Orton et al. 2013, manuscript submitted to Icarus) exhibit molecular emission features from CH4, C2H2, C2H6, C3H4, C4H2, and CO2 in Uranus’ stratosphere. We use these Spitzer/IRS observations to constrain new 1-D photochemical models for Uranus. Although the upper-stratospheric methane abundance is well determined from the observations, there is a range of model parameter space in terms of eddy diffusion coefficients Kzz and tropopause methane relative humidities that can reproduce the observed methane emission. However, all such models possess Kzz values that are considerably smaller than those on the other giant planets; the observations show no convincing evidence for significant changes in low-latitude Kzz values with time since the Voyager era. We highlight the differences in atmospheric chemistry and mixing between Uranus and the other giant planets (including the reasons behind the lower C2H6/C2H2 ratio on Uranus), discuss the implications of the observed C4H2 emission with respect to the vapor pressure of C4H2 over diacetylene ice at low temperatures, and summarize the implications with respect to the influx of external oxygen compounds and their corresponding upper-atmospheric haze components. This research was supported by the NASA Planetary Atmospheres program. Title: The origin of CO in the stratosphere of Uranus Authors: Cavalié, Thibault; Moreno, R.; Lellouch, E.; Hartogh, P.; Venot, O.; Orton, G. S.; Jarchow, C.; Encrenaz, T.; Selsis, F.; Hersant, F.; Fletcher, L. N. Bibcode: 2013DPS....4531214C Altcode: Oxygen-rich deep interiors of the Giant Planets cannot explain the discovery of H2O and CO2 in the stratospheres of the Giant Planets by Feuchtgruber et al. (1997) because these species are trapped by condensation around their tropopause levels (except CO2 in Jupiter and Saturn). Therefore, several sources in the direct or far environment of the Giant Planets have been proposed: icy rings and/or satellites, interplanetary dust particles and large comet impacts. CO does not condense at the tropopauses of Giant Planets, so that oxygen-rich interiors are a valid source. An internal component has indeed been observed in the vertical profile of CO in Jupiter (Bézard et al., 2002) and in Neptune (Lellouch et al., 2005), while an upper limit has been set on its magnitude by for Saturn (Cavalié et al., 2009). In addition to interiors, large comets seem to be the dominant external source, as shown by various studies: Bézard et al. (2002) for Jupiter, Cavalié et al. (2010) for Saturn and Lellouch et al. (2005) for Neptune. The first detection of CO in Uranus was obtained by Encrenaz et al. (2004) from fluorescent emission at 4.7 microns. Assuming a uniform distribution, a mixing ratio of 2x10-8 was derived. Despite this first detection almost a decade ago, the situation has remained unclear ever since. In this paper, we will present the first submillimeter detection of CO in Uranus, carried out with Herschel in 2011-2012. Using a simple diffusion model, we review the various possible sources of CO (internal and external). We show that CO is mostly external. We also derive an upper limit for the internal source. And with the thermochemical model of Venot et al. (2012), adapted to the interior of Uranus, we derive an upper limit on its deep O/H ratio from it. Acknowledgments T. Cavalié acknowledges support from CNES and the European Research Council (Starting Grant 209622: E3ARTHs). References Bézard et al., 2002. Icarus, 159, 95-111. Cavalié et al., 2009. Icarus, 203, 531-540. Cavalié et al., 2010. A&A, 510, A88. Encrenaz et al., 2004. A&A, 413, L5-L9. Feuchtgruber et al., 1997. Nature, 389, 159-162. Lellouch et al., 2005. A&A, 430, L37-L40. Venot et al., 2012. A&A, 546, A43. Title: Oxygen Compounds in Saturn’s Stratosphere During the 2010 Northern Storm Authors: Hesman, Brigette E.; Bjoraker, G. L.; Achterberg, R. K.; Jennings, D. E.; Romani, P. N.; Fletcher, L. N.; Irwin, P. G. Bibcode: 2013DPS....4531212H Altcode: The massive eruption at 40N (planetographic latitude) in December 2010 has produced significant and long-lived changes in temperature and species abundances in Saturn’s northern hemisphere (Hesman et al. 2012a, Fletcher et al. 2012). The northern storm region has been observed on many occasions between January 2011 and June of 2012 by Cassini’s Composite Infrared Spectrometer (CIRS). In this time period, temperatures in regions referred to as “beacons” (warm regions in the stratosphere at certain longitudes in the storm latitude) became significantly warmer than pre-storm values of 140K. In this period hydrocarbon emission greatly increased however this increased emission could not be attributed due to the temperature changes alone for many of these species (Hesman et al. 2012b, Bjoraker et al 2012). In order to build a comprehensive picture of the changes to the stratosphere due to the 2010 northern storm we are now investigating the oxygen compounds in Saturn’s stratosphere to determine if similar changes in these species were measured. The time evolution of stratospheric CO2 and H2O abundances in the beacon regions throughout 2011 and 2012 will be presented. References: Bjoraker, G., B.E. Hesman, R.K. Achterberg, P.N. Romani. 2012, “The Evolution of Hydrocarbons in Saturn’s Northern Storm Region,” AAS DPS Conference, Vol. 44, #403.05. Fletcher, L.N. et al. 2012, “The Origin and Evolution of Saturn’s 2011-2012 Stratospheric Vortex,” Icarus, 221, 560-586. Hesman, B.E. et al. 2012a, “Elusive Ethylene Detected in Saturn’s Northern Storm Region,” The Astrophysical Journal, 760, 24-30. Hesman, B.E. et al. 2012b, “Ethylene Emission in the Aftermath of Saturn’s 2010 Northern Storm,” AAS DPS Conference, Vol. 44, #403.06. Title: Photochemistry in Saturn’s Ring-Shadowed Atmosphere: Venetian Blinds, Atmospheric Molecules and Observations Authors: Edgington, Scott G.; Atreya, S. K.; Wilson, E. H.; Baines, K. H.; West, R. A.; Bjoraker, G. L.; Fletcher, L. N.; Momary, T. Bibcode: 2013DPS....4531215E Altcode: Cassini has been orbiting Saturn for over nine years. During this epoch, the ring shadow has moved from covering a relatively large portion of the northern hemisphere to covering a large swath south of the equator and continues to move southward. At Saturn Orbit Insertion in 2004, the ring plane was inclined by ~24 degrees relative to the Sun-Saturn vector. The projection of the B-ring onto Saturn reached as far as 40N along the central meridian 52N at the terminator). At its maximum extent, the ring shadow can reach as far as 48N/S 58N/S at the terminator). The net effect is that the intensity of both ultraviolet and visible sunlight penetrating into any particular latitude will vary depending on both Saturn’s axis relative to the Sun and the optical thickness of each ring system. In essence, the rings act like venetian blinds. Our previous work [1] examined the variation of the solar flux as a function of solar inclination, i.e. ~8 year season at Saturn. Here, we report on the impact of the oscillating ring shadow on the photolysis and production rates of hydrocarbons in Saturn’s stratosphere and upper troposphere, including acetylene, ethane, propane, and benzene. Beginning with methane, we investigate the impact on production and loss rates of the long-lived photochemical products leading to haze formation are examined at several latitudes over a Saturn year. Similarly, we assess its impact on phosphine abundance, a disequilibrium species whose presence in the upper troposphere is a tracer of convection processes in the deep atmosphere. Comparison to the corresponding rates for the clear atmosphere and for the case of Jupiter, where the variation of solar insolation due to tilt is known to be insignificant 3 degree inclination), will be presented. We will present our ongoing analysis of Cassini’s CIRS, UVIS, and VIMS datasets that provide an estimate of the evolving haze content of the northern hemisphere and we will begin to assess the implications for dynamical mixing. [1] Edgington, S.G., et al., 2012. Photochemistry in Saturn’s Ring Shadowed Atmosphere: Modeling, Observations, and Preliminary Analysis. Bull. American. Astron. Soc., 38, 499 (#11.23). Title: Neptune Clouds and Methane, from Ground-Based Visible and Near-Infrared Spectroscopy with Adaptive Optics Authors: Tice, D. S.; Irwin, P. G. J.; Houghton, R. W. C.; Fletcher, L. N.; Clarke, F.; Hurley, J.; Thatte, N.; Tecza, M. Bibcode: 2013EPSC....8..549T Altcode: Observations of Neptune were made in June/July 2012 with the SWIFT integral field spectrometer at the Palomar Observatory's 200-inch Hale Telescope. Spectral resolutions for observations between 0.65 μm and 1.0 μm were R ≥ 3250. Palomar's PALM-3000 adaptive optics system enabled images of the full Neptunian disc to be recorded at a spatial scale of 0.08"·pixel^-1 with a seeing of approximately 0.30" - 0.40". Retrievals of cloud properties and methane abundance in the highly dynamic atmosphere were obtained with the general-purpose retrieval tool, NEMESIS. The short wavelengths of the observations allowed for good characterisation of the scattering particles' optical properties in the many cloud and haze layers of the upper Neptunian atmosphere. A region of relatively low methane absorption and high collision-induced hydrogen quadrupole absorption at 825 nm further constrains spectral properties of clouds as distinguished from those of methane absorption. Title: The thermal structure of the 2011 Saturn's stratospheric beacon mapped with TEXES/IRTF Authors: Fouchet, T.; Greathouse, T.; Richter, M.; Lacy, J.; Fletcher, L.; Guerlet, S.; Spiga, A. Bibcode: 2013EPSC....8..381F Altcode: We present spectral observations of Saturn's stratosphere obtained in 2011 by the TEXES imaging spectrometer mounted on the IRTF. These observations allowed us to determine the thermal structure of the stratospheric disturbance induced by the 2010 Great White Storm. Title: Saturn northern hemisphere's atmosphere and polar hexagon in 2013 Authors: Delcroix, M.; Yanamandra-Fisher, P.; Fischer, G.; Fletcher, L. N.; Sayanagi, K. M.; Barry, T. Bibcode: 2013EPSC....8.1067D Altcode: In 2013, two years after the dramatic events of the Great White Spot (GWS), amateur astronomers continued to follow the evolution of the "GWS zone" centered around 41° planetographic on Saturn. They could also detect the hexagonal wave surrounding Saturn's north pole with a spot at its edge. Title: TEXES Spectral Mapping of Jupiter and Saturn and the Origins of Giant Planet Nitrogen Authors: Fletcher, L. N.; Greathouse, T. K.; Orton, G. S.; Irwin, P. G. J.; Sinclair, J. A. Bibcode: 2013EPSC....8...28F Altcode: We report spectral mapping of the atmospheres of Jupiter and Saturn in February 2013 using the Texas Echelon cross Echelle Spectrograph (TEXES, [1]) mounted on NASA's Infrared Telescope Facility (IRTF). The purpose of these observations was (i) to study jovian meteorology via measurements of temperature, wind shear, humidity (i.e., ammonia content) and cloud coverage; (ii) to assess the aftermath of Saturn's northern 2010-2011 storm, including the continued existence of the stratospheric anticyclonic vortex [2]; and (iii) to determine precise estimates of the 15N/14N ratio on both planets to constrain the origins of nitrogen to the gas giants. Mid-infrared observations of this nature complement spacecraft observations from Cassini, Juno and, ultimately, JUICE. Title: Cassini Returns to Saturn's Poles: Seasonal Change in the Polar Vortices Authors: Fletcher, L. N.; Orton, G. S.; Irwin, P. G. J.; Sinclair, J. A.; Hesman, B. E.; Hurley, J.; Bjoraker, G. L.; Simon-Miller, A. A. Bibcode: 2013EPSC....8...29F Altcode: High inclination orbits during Cassini's solstice mission (2012-2013) are providing us with our first observations of Saturn's high latitudes since the previous high inclination phase in 2007 (during the prime mission). Since that time, the northern spring pole has emerged into sunlight and the southern autumn pole has disappeared into winter darkness, allowing us to study the seasonal changes occurring within the polar vortices in response to these dramatic insolation changes. Observations from the Cassini Composite Infrared Spectrometer [1] have revealed (i) the continued presence of small, cyclonic polar hotspots at both spring and autumn poles [2]; and (ii) the emergence of an infrared-bright polar vortex at the north pole, consistent with the historical record of Saturn observations from the 1980s (previous northern spring, [3]). Title: First submillimeter observation of CO in the stratosphere of Uranus with Herschel-HIFI Authors: Cavalié, T.; Moreno, R.; Lellouch, E.; Hartogh, P.; Jarchow, C.; Venot, O.; Hersant, F.; Selsis, F.; Orton, G.; Encrenaz, T.; Fletcher, L. Bibcode: 2013EPSC....8...72C Altcode: Oxygen-rich deep interiors of the Giant Planets [1] cannot explain the discovery of water vapor and carbon dioxide in the stratospheres of the Giant Planets by [2] because these species are trapped by condensation around their tropopause levels (except CO2 in Jupiter and Saturn). Therefore, several sources in the direct or far environment of the Giant Planets have been proposed: icy rings and/or satellites [3], interplanetary dust particles [4] and large comet impacts [5]. Infrared Space Observatory (ISO), Cassini, Odin and Herschel observations have proven that the Jovian stratospheric water and carbon dioxide originate from the Shoemaker-Levy 9 comet impacts in July 1994 [6, 7], while Herschel has recently shown the external flux of water at Saturn and Titan is most likely due to the Enceladus geysers and the water torus they feed [8, 9].

As for carbon monoxide (CO), the emerging picture seems to show more uniformity for its sources. Because CO does not condense at the tropopauses of Giant Planets, oxygen-rich interiors are a valid source. An internal component has indeed been observed in the vertical profile of CO in Jupiter by [10] and in Neptune by [11], while an upper limit has been set on its magnitude by [12] for Saturn. In addition to interiors, large comets seem to be the dominant external source of CO in the Giant Planets, as shown by various studies: [10] and [13] for Jupiter, [14] for Saturn and [15] for Neptune.

Despite its first detection almost a decade ago by [16], the situation has remained unclear for Uranus ever since. The (sub)millimeter domain with the use of heterodyne spectroscopy has long been considered as promising to determine the vertical profile of CO, and thus its origin, in Uranus (e.g., [17]). However, attempts made to detect the molecule have failed so far in this spectral range, leading only to upper limits [18]. In this paper, we present the first submillimeter detection of CO in Uranus carried out with the HIFI instrument [19] onboard the Herschel Space Observatory [20] in 2011-2012. Using a simple transport model, we review the various possible sources of CO (internal and external) and constrain their magnitude. For instance, we derive an upper limit for the internal source of CO. And with the thermochemical model of [21], adapted to the interior of Uranus, we derive an upper limit on its deep O/H ratio from it. Title: Constraining the atmosphere of GJ 1214b using an optimal estimation technique Authors: Barstow, J. K.; Aigrain, S.; Irwin, P. G. J.; Fletcher, L. N.; Lee, J. -M. Bibcode: 2013MNRAS.434.2616B Altcode: 2013MNRAS.tmp.1887B; 2013arXiv1306.6567B We explore cloudy, extended H2-He atmosphere scenarios for the warm super-Earth GJ 1214b using an optimal estimation retrieval technique. This planet, orbiting an M4.5 star only 13 pc from the Earth, is of particular interest because it lies between the Earth and Neptune in size and may be a member of a new class of planet that is neither terrestrial nor gas giant. Its relatively flat transmission spectrum has so far made atmospheric characterization difficult. The Non-linear optimal Estimator for MultivariateE spectral analySIS (NEMESIS) algorithm is used to explore the degenerate model parameter space for a cloudy, H2-He-dominated atmosphere scenario. Optimal estimation is a data-led approach that allows solutions beyond the range permitted by ab initio equilibrium model atmosphere calculations, and as such prevents restriction from prior expectations. We show that optimal estimation retrieval is a powerful tool for this kind of study, and present an exploration of the degenerate atmospheric scenarios for GJ 1214b. Whilst we find a family of solutions that provide a very good fit to the data, the quality and coverage of these data are insufficient for us to more precisely determine the abundances of cloud and trace gases given an H2-He atmosphere, and we also cannot rule out the possibility of a high molecular weight atmosphere. Future ground- and space-based observations will provide the opportunity to confirm or rule out an extended H2-He atmosphere, but more precise constraints will be limited by intrinsic degeneracies in the retrieval problem, such as variations in cloud top pressure and temperature. Title: The 2010-2011 revival of Jupiter's South Equatorial Belt Authors: Giles, R. S.; Fletcher, L. N.; Irwin, P. G. J.; Orton, G. S.; Rogers, J. H. Bibcode: 2013EPSC....8...33G Altcode: In 2009-2010, Jupiter's South Equatorial Belt (SEB) faded to a very pale colour before the 2010-2011 revival restored the belt to its ordinary dark appearance. Mid-infrared images of the revival were taken using VISIR (VLT) across a range of wavelengths from 7 to 25 μm. These were used to retrieve changes in temperature and aerosol optical depth as the revival proceeded between November 2010 and September 2011. Title: Science goals and concepts of a Saturn probe for the future L2/L3 ESA call Authors: Mousis, O.; Fletcher, L. N.; André, N.; Blanc, M.; Coustenis, A.; Gautier, D.; Geppert, W. D.; Guillot, T.; Irwin, P.; Lebreton, J. -P.; Marty, B.; Morse, A.; Murray, C.; Petit, J. -M.; Sanchez-Lavega, A.; Schmider, F. -X.; Waite, J. H.; Wurz, P. Bibcode: 2013EPSC....8..232M Altcode: A Saturn probe is the next natural step beyond Galileo's in situ exploration of Jupiter, and the Cassini spacecraft's orbital reconnaissance of Saturn in order to understand the origin of giant planets. Here we describe the science goals and concepts of a Saturn probe that could be submitted to the future L2/L3 ESA call. Title: From Voyager-IRIS to Cassini-CIRS: Interannual Variability in Saturn's Stratosphere Authors: Sinclair, J. A.; Irwin, P. G. J.; Fletcher, L. N.; Hurley, J.; Merlet, C. Bibcode: 2013EPSC....8...35S Altcode: We present an intercomparison of Saturn's atmosphere from Voyager-IRIS observations in 1980 with Cassini-CIRS observations in 2009/2010. Over a Saturn year (∼29.5 years) has now passed since the Voyager flyby of Saturn in 1980/1981. Cassini observations in 2009/2010 and those from Voyager therefore capture Saturn in the same season (at approximately the vernal equinox, solar longitude, Ls~∼0°). Any differences in Saturn's stratospheric properties implied by a comparison of these two datasets will therefore highlight interannual variability. We retrieve temperature and stratospheric acetylene and ethane concentrations from Voyager 1-IRIS (FWHM = 4.3 cm-1) in 1980 and Cassini-CIRS 'FIRMAP' (FWHM = 15.5 cm-1) observations in 2009/2010. Preliminary results show the equator to be warmer by 7.3 ± 1.6 K at ∼2.1 mbar in 2009 than in 1980 implying a differing phase of the SSAO (Saturn's semi-annual oscillation). Ethane's meridional distribution at 2.1 mbar appears consistent between 1980 and 2009/2010. However, the concentrations of acetylene at the same altitude appear enhanced at ∼25°S and ∼25°N in 1980 when compared to 2009/2010. A global-circulation model shows cells of downwelling at these latitudes [3]: the richer concentrations of acetylene at these latitudes in 1980 suggests that there was stronger downwelling at this time than in 2009. Title: The flux of impacts in Jupiter: From superbolides to large-scale collisions Authors: Hueso, R.; Pérez-Hoyos, S.; Sánchez-Lavega, A.; . Wesley, A.; Hall, G.; Go, C.; Tachikawa, M.; Aoki, K.; Ichimaru, M.; Delcroix, M.; Wong, M.; Pond, J. W. T.; Korycansky, D. G.; Palotai, C.; Rebeli, N.; Harrington, J.; de Pater, I.; Fletcher, L. N.; Hammel, H.; Orton, G. S.; Tabe, I.; Watanabe, J.; Moreno, J. C. Bibcode: 2013EPSC....8..228H Altcode: Observations of Jupiter by a large number of amateurs have resulted in the discovery of three fireballs in its atmosphere produced by the impacts of small objects. The fireballs were detected on June 3, 2010, August 20, 2010 and September 10, 2012. The light-curves of these atmospheric airbursts provide a measure of the masses and sizes of the impacting objects and the statistical significance of the three events can be examined from knowledge of the large pool of Jupiter observations by the global community of amateur astronomers. These objects are in the category of 5-20 m sizes depending on their density and release energies comparable to the recent Chelyabinsk airburst. Current biases in observations of Jupiter suggest a rate of similar impacts of 18-160 per year. Title: Clouds on hot Jupiters: implications for transit spectroscopy Authors: Barstow, J. K.; Aigrain, S.; Irwin, P. G. J.; Fletcher, L. N.; Lee, J. -M. Bibcode: 2013EPSC....8..255B Altcode: Since the first detection of a planet orbiting another main sequence star, hundreds of extrasolar planets have been confirmed and more than 2000 candidates have been identified. To date, the best-characterised class of planets using this method are the 'hot Jupiters', and evidence is now emerging that these hot planets have cloudy atmospheres. Clouds and aerosols have a large impact on the spectroscopic signatures and radiation balance of the planets in our own solar system; this is also true for brown dwarfs, which exist at similar temperatures to the hottest of the giant exoplanets. We investigate the effect of different types of cloud on the transmission and eclipse spectra of hot Jupiters, and will thereby explore ways of breaking degeneracies between different model atmosphere scenarios. Title: The Ultraviolet Spectrograph on the JUICE Mission (JUICE-UVS) Authors: Gladstone, R.; Retherford, K.; Eterno, J.; Persyn, S.; Davis, M.; Versteeg, M.; Greathouse, T.; Persson, K.; Dirks, G.; Walther, B.; Araujo, M.; Steffl, A.; Schindhelm, R.; Spencer, J.; McGrath, M.; Bagenal, F.; Feldman, P.; Fletcher, L. Bibcode: 2013EPSC....8..394G Altcode: The ultraviolet spectrograph instrument for the JUICE mission (JUICE-UVS) has been selected to provide a variety of ultraviolet science observations during the mission's survey of the Jovian system. The goals of our investigation are to explore the atmospheres, plasma interactions, and surfaces of the Galilean satellites; to determine the dynamics, chemistry, and vertical structure of Jupiter's upper atmosphere, from equator to pole, as a template for giant planets everywhere; and to investigate the Jupiter-Io connection by quantifying energy and mass flow in the Io atmosphere, neutral clouds, and torus. In this talk we describe the science objectives for JUICE-UVS, along with an overview of its design and expected performance. Title: The transit spectra of the Solar System planets Authors: Irwin, P. G. J.; Fletcher, L. N.; Barstow, J.; Aigrain, S.; Lee, J. -M. Bibcode: 2013EPSC....8...92I Altcode: In recent years, an increasing number of observations have been made of the transits of 'Hot Jupiters', such as HD 189733b, from the visible through to midinfrared wavelengths, which have been modelled to derive the likely atmospheric structure and composition of these planets. As measurement techniques improve, the measured transit spectra of 'Super-Earths' such as GJ 1214b are becoming better constrained, allowing model atmospheric states to be fitted for this class of planet also. While it is not yet possible to constrain the atmospheric states of small planets like the Earth or cold planets like Jupiter, it is hoped that this might become practical in the coming decades and if so, it is of interest to determine what we might infer from such measurements. In this work we have constructed atmospheric models of the Solar System planets from 0.2 - 15 μm that are consistent with groundbased and satellite observations and from these calculate the primary and secondary transit spectra (with respect to the Sun) that would be observed by a 'remote observer', many light years away. From these spectra we test what current retrieval models might infer about their atmospheric states and compare these with the 'ground truths' in order to assess: a) the inherent uncertainties in transit spectra observations; b) the relative merits of primary versus secondary transit spectra; and c) assess the optimal wavelength coverage and sensitivities required to retrieve atmospheric states that reasonably match the Solar System planet atmospheres. Title: Hot ribbon plasma during the rise phase of a flare Authors: Fletcher, Lyndsay; Hannah, I. Bibcode: 2013SPD....44...66F Altcode: Strong heating of the chromosphere and transition region during flares results in ribbons containing plasma at temperatures ranging from a few thousand K to 10 million K. We have used SDO to construct emission measure maps in the extended rise phase of the M1.0 event SOL2010-08-07T17:55 using the method of Hannah & Kontar (2012), allowing a pixel-by-pixel examination of the development of thermal plasma in the ribbons, and detailed comparison with the ribbons' magnetic environment. Using RHESSI hard X-ray observations we set limits on the non-thermal emission from the ribbons, and examine the contribution of energy loss by non-thermal electrons to the ribbon heating in this phase. Title: Seasonal variations of temperature, acetylene and ethane in Saturn's atmosphere from 2005 to 2010, as observed by Cassini-CIRS Authors: Sinclair, J. A.; Irwin, P. G. J.; Fletcher, L. N.; Moses, J. I.; Greathouse, T. K.; Friedson, A. J.; Hesman, B.; Hurley, J.; Merlet, C. Bibcode: 2013Icar..225..257S Altcode: Acetylene (C2H2) and ethane (C2H6) are by-products of complex photochemistry in the stratosphere of Saturn. Both hydrocarbons are important to the thermal balance of Saturn's stratosphere and serve as tracers of vertical motion in the lower stratosphere. Earlier studies of Saturn's hydrocarbons using Cassini-CIRS observations have provided only a snapshot of their behaviour. Following the vernal equinox in August 2009, Saturn's northern and southern hemispheres have entered spring and autumn, respectively, however the response of Saturn's hydrocarbons to this seasonal shift remains to be determined. In this paper, we investigate how the thermal structure and concentrations of acetylene and ethane have evolved with the changing season on Saturn. We retrieve the vertical temperature profiles and acetylene and ethane volume mixing ratios from Δν∼=15.5cm-1 Cassini-CIRS observations. In comparing 2005 (solar longitude, Ls ∼ 308°), 2009 (Ls ∼ 3°) and 2010 (Ls ∼ 15°) results, we observe the disappearance of Saturn's warm southern polar hood with cooling of up to 17.1 K ± 0.8 K at 1.1 mbar at high-southern latitudes. Comparison of the derived temperature trend in this region with a radiative climate model (Section 4 of Fletcher et al., 2010 and Greathouse et al. (2013, in preparation)) indicates that this cooling is radiative although dynamical changes in this region cannot be ruled out. We observe a 21 ± 12% enrichment of acetylene and a 29 ± 11% enrichment of ethane at 25°N from 2005 to 2009, suggesting downwelling at this latitude. At 15°S, both acetylene and ethane exhibit a decrease in concentration of 6 ± 11% and 17 ± 9% from 2005 to 2010, respectively, which suggests upwelling at this latitude (though a statistically significant change is only exhibited by ethane). These implied vertical motions at 15°S and 25°N are consistent with a recently-developed global circulation model of Saturn's tropopause and stratosphere(Friedson and Moses, 2012), which predicts this pattern of upwelling and downwelling as a result of a seasonally-reversing Hadley circulation. Ethane exhibits a general enrichment at mid-northern latitudes from 2005 to 2009. As the northern hemisphere approaches summer solstice in 2017, this feature might indicate an onset of a meridional enrichment of ethane, as has been observed in the southern hemisphere during/after southern summer solstice. Title: Flare Science with the ATST Authors: Fletcher, Lyndsay Bibcode: 2013SPD....4440102F Altcode: A flare's radiation appears mostly in the near-UV, optical and near infrared, emitted by the dense chromosphere where most of the flare energy is ultimately dissipated. Catching flares with a small field-of-view imager or a slit-rastering spectrometer is challenging, but observations with the ATST will lead to tremendous advances in our knowledge of a flare's magnetic environment and its variations, the structure and evolution of the flare chromosphere, and the temporal and spatial scales of energy transport and dissipation. This talk will review in brief our understanding of flares in the ATST's wavelength range, and describe some observational goals for flare science with the ATST first light instruments. Title: Flare Ribbon Energetics in the Early Phase of an SDO Flare Authors: Fletcher, L.; Hannah, I. G.; Hudson, H. S.; Innes, D. E. Bibcode: 2013ApJ...771..104F Altcode: 2014arXiv1401.6538F The sites of chromospheric excitation during solar flares are marked by extended extreme ultraviolet ribbons and hard X-ray (HXR) footpoints. The standard interpretation is that these are the result of heating and bremsstrahlung emission from non-thermal electrons precipitating from the corona. We examine this picture using multi-wavelength observations of the early phase of an M-class flare SOL2010-08-07T18:24. We aim to determine the properties of the heated plasma in the flare ribbons, and to understand the partition of the power input into radiative and conductive losses. Using GOES, SDO/EVE, SDO/AIA, and RHESSI, we measure the temperature, emission measure (EM), and differential emission measure of the flare ribbons, and deduce approximate density values. The non-thermal EM, and the collisional thick target energy input to the ribbons are obtained from RHESSI using standard methods. We deduce the existence of a substantial amount of plasma at 10 MK in the flare ribbons, during the pre-impulsive and early-impulsive phase of the flare. The average column EM of this hot component is a few times 1028 cm-5, and we can calculate that its predicted conductive losses dominate its measured radiative losses. If the power input to the hot ribbon plasma is due to collisional energy deposition by an electron beam from the corona then a low-energy cutoff of ~5 keV is necessary to balance the conductive losses, implying a very large electron energy content. Independent of the standard collisional thick-target electron beam interpretation, the observed non-thermal X-rays can be provided if one electron in 103-104 in the 10 MK (1 keV) ribbon plasma has an energy above 10 keV. We speculate that this could arise if a non-thermal tail is generated in the ribbon plasma which is being heated by other means, for example, by waves or turbulence. Title: Stochastic Simulations of the Pitch-angle Scattering of High Energy Electrons Authors: Dickson, Ewan C.; Kontar, E.; Fletcher, L. Bibcode: 2013SPD....44...56D Altcode: The angular variation of high energy electrons during a solar flare is key to understanding the acceleration mechanism. Regularised inversion of RHESSI X-ray spectra, using the effect of photospheric albedo, allows us to estimate the angular distributions of the emitting electrons. The results for all flares studied are consistent with an isotropic pitch-angle distribution, and inconsistent with a ratio of downward to upward going electron flux greater than 3:1. To attempt to understand these results, I have performed stochastic simulations of electron pitch-angle scattering by Coulomb collisions, including the effects of collisional energy loss, and of magnetic field convergence. This allows us to estimate what constraints these observations put on the parameters of the electron beam, such as initial directionality, and of the characteristics of the loop itself. These simulations suggest that Coulomb collisions cannot sufficiently isotropise the distribution to be consistent with the observations, even for an initially isotropic injected distribution. Title: The properties of flare kernels observed by the Dunn Solar Telescope Authors: Fletcher, Lyndsay; Kowalski, A.; Cauzzi, G.; Hawley, S. L.; Hudson, H. S. Bibcode: 2013SPD....44...67F Altcode: We report on a campaign at the Dunn Solar Telescope which resulted in successful imaging and spectroscopic observations of a C1.1 solar flare on 18th August 2011. This flare exhibited ribbons with complicated fine structure at the resolution of the DST/IBIS instrument, and a number of bright kernels with sizes comparable to the smallest scales sampled by IBIS, around 2-4 pixels (0."3-0."6) FWHM. We focus on these bright kernels, describing their spatial characteristics in the core and wing of H alpha and Ca II 8542, and in the UV and EUV with SDO. We also show preliminary broad-band spectroscopy of the kernels which may demonstrate the presence of an optical continuum in this small flare. Title: A new approach to model particle acceleration and energy transfer in solar flares Authors: Rubio Da Costa, Fatima; Zuccarello, F.; Fletcher, L.; Labrosse, N.; Kasparova, J.; Prosecký, T.; Carlsson, M.; Petrosian, V.; Liu, W. Bibcode: 2013SPD....4440401R Altcode: Motivated by available observations of two different flares in Lyα and Hα, we model the conditions of the solar atmosphere using a radiation hydrodynamics code (RADYN, Carlsson & Stein, 1992) and analyze the energy transport carried by a beam of non-thermal electrons injected at the top of a 1D coronal loop. The numerical Lyα and Hα intensities match with the observations. The electron energy distribution is assumed to follow a power law of the form (E/Ec )-δ for energies greater than a cutoff value of Ec. Abbett & Hawley (1999) and Allred et al. (2005) assumed that the non-thermal electrons flux injected at the top of a flaring loop, the cut-off energy and the power law index are constant over time. An improvement was achieved by Allred & Hawley (2006), who modified the RADYN code in such a way that the input parameters were time dependent. Their inputs were based on observations of a flare obtained with RHESSI. By combining RADYN with the “flare” code from Stanford University which models the acceleration and transport of particles and radiation of solar flares in non-LTE regime, we can calculate the non-thermal electrons flux, the cut-off energy and the power law index at every simulated time step. The atmospheric parameters calculated by RADYN could in turn be used as updated inputs for "flare", providing several advantages over the results from Liu et al. (2009), who combined the particle acceleration code with a 1-D hydrodynamic code, improving the atmospheric conditions. Title: Impulsive Thermal X-Ray Emission from a Low-lying Coronal Loop Authors: Liu, Siming; Li, Youping; Fletcher, Lyndsay Bibcode: 2013ApJ...769..135L Altcode: 2013arXiv1304.5584L Understanding the relationship among different emission components plays an essential role in the study of particle acceleration and energy conversion in solar flares. In flares where gradual and impulsive emission components can be readily identified, the impulsive emission has been attributed to non-thermal particles. We carry out detailed analysis of Hα and X-ray observations of a GOES class B microflare loop on the solar disk. The impulsive hard X-ray emission, however, is found to be consistent with a hot, quasi-thermal origin, and there is little evidence of emission from chromospheric footpoints, which challenges conventional models of flares and reveals a class of microflares associated with dense loops. Hα observations indicate that the loop lies very low in the solar corona or even in the chromosphere and both emission and absorption materials evolve during the flare. The enhanced Hα emission may very well originate from the photosphere when the low-lying flare loop heats up the underlying chromosphere and reduces the corresponding Hα opacity. These observations may be compared with detailed modeling of flare loops with the internal kink instability, where the mode remains confined in space without apparent change in the global field shape, to uncover the underlying physical processes and to probe the structure of solar atmosphere. Title: JUpiter ICy moons Explorer (JUICE): An ESA mission to orbit Ganymede and to characterise the Jupiter system Authors: Grasset, O.; Dougherty, M. K.; Coustenis, A.; Bunce, E. J.; Erd, C.; Titov, D.; Blanc, M.; Coates, A.; Drossart, P.; Fletcher, L. N.; Hussmann, H.; Jaumann, R.; Krupp, N.; Lebreton, J. -P.; Prieto-Ballesteros, O.; Tortora, P.; Tosi, F.; Van Hoolst, T. Bibcode: 2013P&SS...78....1G Altcode: Past exploration of Jupiter's diverse satellite system has forever changed our understanding of the unique environments to be found around gas giants, both in our solar system and beyond. The detailed investigation of three of Jupiter's Galilean satellites (Ganymede, Europa, and Callisto), which are believed to harbour subsurface water oceans, is central to elucidating the conditions for habitability of icy worlds in planetary systems in general. The study of the Jupiter system and the possible existence of habitable environments offer the best opportunity for understanding the origins and formation of the gas giants and their satellite systems. The JUpiter ICy moons Explorer (JUICE) mission, selected by ESA in May 2012 to be the first large mission within the Cosmic Vision Program 2015-2025, will perform detailed investigations of Jupiter and its system in all their inter-relations and complexity with particular emphasis on Ganymede as a planetary body and potential habitat. The investigations of the neighbouring moons, Europa and Callisto, will complete a comparative picture of the Galilean moons and their potential habitability. Here we describe the scientific motivation for this exciting new European-led exploration of the Jupiter system in the context of our current knowledge and future aspirations for exploration, and the paradigm it will bring in the study of giant (exo) planets in general. Title: On the potential of the EChO mission to characterize gas giant atmospheres Authors: Barstow, J. K.; Aigrain, S.; Irwin, P. G. J.; Bowles, N.; Fletcher, L. N.; Lee, J. -M. Bibcode: 2013MNRAS.430.1188B Altcode: 2013MNRAS.tmp..637B; 2013MNRAS.tmp..679B Space telescopes such as Exoplanet Characterisation Observatory (EChO) and James Webb Space Telescope (JWST) will be important for the future study of extrasolar planet atmospheres. Both of these missions are capable of performing high sensitivity spectroscopic measurements at moderate resolutions in the visible and infrared, which will allow the characterization of atmospheric properties using primary and secondary transit spectroscopy. We use the Non-linear optimal Estimator for MultivariateE spectral analysis (NEMESIS) radiative transfer and retrieval tool, as developed by Irwin et al. and Lee et al., to explore the potential of the proposed EChO mission to solve the retrieval problem for a range of H2-He planets orbiting different stars. We find that EChO should be capable of retrieving temperature structure to ∼200 K precision and detecting H2O, CO2 and CH4 from a single eclipse measurement for a hot Jupiter orbiting a Sun-like star and a hot Neptune orbiting an M star, also providing upper limits on CO and NH3. We provide a table of retrieval precisions for these quantities in each test case. We expect around 30 Jupiter-sized planets to be observable by EChO; hot Neptunes orbiting M dwarfs are rarer, but we anticipate observations of at least one similar planet. Title: The Emission Measure Distribution of Impulsive Phase Flare Footpoints Authors: Graham, D. R.; Hannah, I. G.; Fletcher, L.; Milligan, R. O. Bibcode: 2013ApJ...767...83G Altcode: 2013arXiv1302.2514G The temperature distribution of the emitting plasma is a crucial constraint when studying the heating of solar flare footpoints. However, determining this for impulsive phase footpoints has been difficult in the past due to insufficient spatial resolution to resolve the footpoints from the loop structures, and a lack of spectral and temporal coverage. We use the capabilities of Hinode/Extreme Ultraviolet Imaging Spectrometer to obtain the first emission measure distributions (EMDs) from impulsive phase footpoints in six flares. Observations with good spectral coverage were analyzed using a regularized inversion method to recover the EMDs. We find that the EMDs all share a peak temperature of around 8 MK, with lines formed around this temperature having emission measures (EMs) peaking between 1028 and 1029 cm-5, indicating a substantial presence of plasma at very high temperatures within the footpoints. An EMD gradient of EM(T) ~ T is found in all events. Previous theoretical work on EM gradients shows this to be consistent with a scenario in which the deposited flare energy directly heats only the top layer of the flare chromosphere, while deeper layers are heated by conduction. Title: Propagation of Alfvénic Waves from Corona to Chromosphere and Consequences for Solar Flares Authors: Russell, A. J. B.; Fletcher, L. Bibcode: 2013ApJ...765...81R Altcode: 2013arXiv1302.2458R How do magnetohydrodynamic waves travel from the fully ionized corona, into and through the underlying partially ionized chromosphere, and what are the consequences for solar flares? To address these questions, we have developed a two-fluid model (of plasma and neutrals) and used it to perform one-dimensional simulations of Alfvén waves in a solar atmosphere with realistic density and temperature structure. Studies of a range of solar features (faculae, plage, penumbra, and umbra) show that energy transmission from corona to chromosphere can exceed 20% of incident energy for wave periods of 1 s or less. Damping of waves in the chromosphere depends strongly on wave frequency: waves with periods 10 s or longer pass through the chromosphere with relatively little damping, however, for periods of 1 s or less, a substantial fraction (37%-100%) of wave energy entering the chromosphere is damped by ion-neutral friction in the mid- and upper chromosphere, with electron resistivity playing some role in the lower chromosphere and in umbras. We therefore conclude that Alfvénic waves with periods of a few seconds or less are capable of heating the chromosphere during solar flares, and speculate that they could also contribute to electron acceleration or exciting sunquakes. Title: A Gemini ground-based transmission spectrum of WASP-29b: a featureless spectrum from 515 to 720 nm Authors: Gibson, N. P.; Aigrain, S.; Barstow, J. K.; Evans, T. M.; Fletcher, L. N.; Irwin, P. G. J. Bibcode: 2013MNRAS.428.3680G Altcode: 2012arXiv1210.7798G We report Gemini-South Gemini Multi-Object Spectrograph observations of the exoplanet system WASP-29 during primary transit as a test case for differential spectrophotometry. We use the multi-object spectrograph to observe the target star and a comparison star simultaneously to produce multiple light curves at varying wavelengths. The `white' light curve and 15 `spectral' light curves are analysed to refine the system parameters and produce a transmission spectrum from ∼515 to 720 nm. All light curves exhibit time-correlated noise, which we model using a variety of techniques. These include a simple noise rescaling, a Gaussian process model and a wavelet-based method. These methods all produce consistent results, although with different uncertainties. The precision of the transmission spectrum is improved by subtracting a common signal from all the spectral light curves, reaching a typical precision of ∼1 × 10-4 in transit depth. The transmission spectrum is free of spectral features, and given the non-detection of a pressure broadened Na feature, we can rule out the presence of a Na-rich atmosphere free of clouds or hazes, although we cannot rule out a narrow Na core. This indicates that Na is not present in the atmosphere, and/or that clouds/hazes play a significant role in the atmosphere and mask the broad wings of the Na feature, although the former is a more likely explanation given WASP-29b's equilibrium temperature of ∼970 K, at which Na can form various compounds. We also briefly discuss the use of Gaussian process and wavelet methods to account for time-correlated noise in transit light curves. Title: Particle acceleration and dynamical heating in Cycle 24 flares Authors: Hannah, I. G.; Fletcher, L.; Kontar, E. P. Bibcode: 2012AGUFMSH51C..07H Altcode: The current wealth of solar observations presents a unique opportunity to study energy release in solar flares, particularly particle acceleration and plasma heating. The spatial and temporal resolution of SDO/AIA EUV data give an unprecedented view of dynamical heating in solar flares yet to fully exploit this resource the underlying thermal properties of the emitting plasma needs to be recovered. This is difficult as it is an ill-posed inverse problem and there is copious data. Our recently implemented regularized inversion method (Hannah & Kontar A&A 2012a,b) can quickly and robustly find the Differential Emission Measure (DEM) solution (and its uncertainties), with the resulting EM maps allowing the temperature and density evolution to be studied both spatially and temporally. Combing this with the hard X-ray imaging and spectroscopy of RHESSI, we present a study of the non-thermal energy input and thermal response in some flares of the rising phase of cycle 24. We also look at the relationship between the energetics of flares and the underlying magnetic field configurations. Title: Latitudinal variation of upper tropospheric NH3 on Saturn derived from Cassini/CIRS far-infrared measurements Authors: Hurley, J.; Fletcher, L. N.; Irwin, P. G. J.; Calcutt, S. B.; Sinclair, J. A.; Merlet, C. Bibcode: 2012P&SS...73..347H Altcode: Ammonia (NH3) has been detected both on Saturn and Jupiter, and although its concentration and distribution has been well-studied on Jupiter, it has proven more difficult to do so on Saturn due to higher sensitivity requirements resulting from Saturn's lower atmospheric temperatures and the dominance of Saturn's phosphine which masks the ammonia signal. Using far-infrared measurements of Saturn taken by Cassini/CIRS between February 2005 and December 2010, the latitudinal variations of upper tropospheric ammonia on Saturn are studied. Sensitivity to NH3 in the far-infrared is explored to provide estimates of temperature, para-H2 and PH3, from 2.5 cm-1 spectral resolution measurements alone, 0.5 cm-1 spectral-resolution measurements alone, and 0.5 cm-1 measurements degraded to 2.5 cm-1 spectral resolution. The estimates of NH3 from these three different datasets largely agree, although there are notable differences using the high emission angle 0.5 cm-1 data, which are asserted to result from a reduction in sensitivity at higher emission angles. For low emission angles, the 0.5 cm-1-retrieved values of NH3 can be used to reproduce the 2.5 cm-1 spectra with similar efficacy as those derived directly from the 2.5 cm-1 resolution data itself, and vice versa. Using low emission angle data, NH3 is observed to have broad peak abundances at ±25° latitude, attributed to result from condensation and/or photolytic processes. Lack of data coverage at equatorial latitudes precludes analysis of NH3 abundance at less than about 10° latitude. Noise levels are not sufficient to distinguish fine zonal features, although it seems that NH3 cannot trace the zonal belt/zone structure in the upper troposphere of Saturn. Title: Photochemistry in Saturn's Ring Shadowed Atmosphere: Production Rates of Key Atmospheric Molecules and Preliminary Analysis of Observations Authors: Edgington, S. G.; Atreya, S. K.; Wilson, E. H.; West, R. A.; Baines, K. H.; Bjoraker, G. L.; Fletcher, L. N.; Momary, T. Bibcode: 2012AGUFM.P13B1946E Altcode: Cassini has been orbiting Saturn for over eight years. During this epoch, the ring shadow has moved from shading a large portion of the northern hemisphere (the ring plane was inclined by ~24 degrees relative to the Sun-Saturn vector) to shading mid-latitudes south of the equator and continues southward. At its maximum extent, the projection of the ring plane shadow onto Saturn can reach as far as 48N (~58N at the terminator). The net result, is that the intensity of both ultraviolet and visible sunlight penetrating onto any particular northern/southern latitude will vary depending on Saturn's tilt relative to the Sun and the optical thickness of each ring system. Our previous work has examined the variation of the solar flux as a function of solar inclination, i.e. season on Saturn. Here we report on the impact of the oscillating ring shadow on the photolysis and production rates of key hydrocarbons in Saturn's stratosphere and upper troposphere, including ethane, acetylene, propane, benzene. We investigate the impact on production and loss rates of the long-lived, photochemical hydrocarbons leading to haze formation at several latitudes over one Saturn year. Similarly, we assess the impact on the abundance of phosphine, a disequilibrium species whose presence in the upper troposphere is a tracer of convection processes in the deep atmosphere. Along with the above, we present preliminary analysis of Cassini's UVIS and VIMS datasets that provide an estimate of the evolving haze content of the northern hemisphere. We will also compare our model results to abundances determined from previously released CIRS observations. The research described in this paper was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Title: Properties of Slowly Moving Thermal Waves in Saturn from Cassini CIRS Observations from 2004 to 2009 Authors: Orton, G. S.; Fletcher, L. N.; Flasar, F. M.; Achterberg, R. K.; Brown, S. K. Bibcode: 2012AGUFM.P13B1928O Altcode: Hemispherical maps of Saturn's atmosphere made by the Cassini Composite Infrared Spectrometer (CIRS) were surveyed for the presence and properties of zonal thermal waves and their variability in time. The most inclusive surveys in latitude, FIRMAPs (15 cm-1 spectral resolution), covered the planet from the equator to either the north or south pole, sweeping through the latitude range while the planet rotated beneath over its ~10-hour rotation. Four spectral ranges were sampled: two in a region dominated by upper-tropospheric emission (80-200 mbar) from collision-induced H2 opacity and two in regions dominated by stratospheric emission (0.5-3 mbar) from ethane (12.3 μm) and methane (7.7 μm), respectively. We examined maps that were taken between 2004 and Saturn's spring equinox in 2009. During this time, the strongest waves were found between planetographic latitudes of 30° and 45° S; in the northern hemisphere, they were found between the equator and 30°N. Some low-wavenumber components cover all 360° in longitude, similar to the slowly moving thermal waves in Jupiter's atmosphere, but the strongest waves were found in "trains" that covered only one hemisphere or less. In 2005, tropospheric waves had a mean peak-to-peak variance that was the equivalent of temperature variability of about 1 K. Between 2005 and 2007, they had subsided to about 0.5 K. During and after 2008 they soared to over 3 K. During this entire period, similar waves in the northern hemisphere were never larger than 0.8 K. In the stratosphere, waves followed a similar time sequence, with southern hemisphere waves in 2005 reaching as much as 3.5 K in brightness temperature, subsequently decreasing, then growing in 2008-2009 to over 5 K. Stratospheric waves in the northern hemisphere were nearly constant around 2 K, but with an instance of 6 K at one epoch in 2008. The phase of the waves moved about 0.5° of longitude per day retrograde with respect to System III. The phase of tropospheric and stratospheric waves appeared to be highly correlated with one another, with little offset in longitude. Title: Elusive Ethylene Detected in Saturn's Northern Storm Region Authors: Hesman, B. E.; Bjoraker, G. L.; Sada, P. V.; Achterberg, R. K.; Jennings, D. E.; Romani, P. N.; Lunsford, A. W.; Fletcher, L. N.; Boyle, R. J.; Simon-Miller, A. A.; Nixon, C. A.; Irwin, P. G. J. Bibcode: 2012ApJ...760...24H Altcode: The massive eruption at 40°N (planetographic latitude) on Saturn in 2010 December has produced significant and lasting effects in the northern hemisphere on temperature and species abundances. The northern storm region was observed on many occasions in 2011 by Cassini's Composite Infrared Spectrometer (CIRS). In 2011 May, temperatures in the stratosphere greater than 200 K were derived from CIRS spectra in the regions referred to as "beacons" (warm regions in the stratosphere). Ethylene has been detected in the beacon region in Saturn's northern storm region using CIRS. Ground-based observations using the high-resolution spectrometer Celeste on the McMath-Pierce Telescope on 2011 May 15 were used to confirm the detection and improve the altitude resolution in the retrieved profile. The derived ethylene profile from the CIRS data gives a C2H4 mole fraction of 5.9 ± 4.5 × 10-7 at 0.5 mbar, and from Celeste data it gives 2.7 ± 0.45 × 10-6 at 0.1 mbar. This is two orders of magnitude higher than the amount measured in the ultraviolet at other latitudes prior to the storm. It is also much higher than predicted by photochemical models, indicating that perhaps another production mechanism is required or a loss mechanism is being inhibited. Title: Unusual Stokes V profiles during flaring activity of a delta sunspot Authors: Fischer, C. E.; Keller, C. U.; Snik, F.; Fletcher, L.; Socas-Navarro, H. Bibcode: 2012A&A...547A..34F Altcode: 2012arXiv1209.0983F
Aims: We analyze a set of full Stokes profile observations of the flaring active region NOAA 10808. The region was recorded with the Vector-Spectromagnetograph of the Synoptic Optical Long-term Investigations of the Sun facility. The active region produced several successive X-class flares between 19:00 UT and 24:00 UT on September 13, 2005 and we aim to quantify transient and permanent changes in the magnetic field and velocity field during one of the flares, which has been fully captured.
Methods: The Stokes profiles were inverted using the height-dependent inversion code LILIA to analyze magnetic field vector changes at the flaring site. We report multilobed asymmetric Stokes V profiles found in the δ-sunspot umbra. We fit the asymmetric Stokes V profiles assuming an atmosphere consisting of two components (SIR inversions) to interpret the profile shape. The results are put in context with Michelson Doppler Imager (MDI) magnetograms and reconstructed X-ray images from the Reuven Ramaty High Energy Solar Spectroscopic Imager.
Results: We obtain the magnetic field vector and find signs of restructuring of the photospheric magnetic field during the flare close to the polarity inversion line at the flaring site. At two locations in the umbra we encounter strong fields (~3 kG), as inferred from the Stokes I profiles, which, however, exhibit a low polarization signal. During the flare we observe in addition asymmetric Stokes V profiles at one of these sites. The asymmetric Stokes V profiles appear co-spatial and co-temporal with a strong apparent polarity reversal observed in MDI-magnetograms and a chromospheric hard X-ray source. The two-component atmosphere fits of the asymmetric Stokes profiles result in line-of-sight velocity differences in the range of ~12 km s-1 to 14 km s-1 between the two components in the photosphere. Another possibility is that local atmospheric heating is causing the observed asymmetric Stokes V profile shape. In either case our analysis shows that a very localized patch of ~5″ in the photospheric umbra, co-spatial with a flare footpoint, exhibits a subresolution fine structure. Title: Ethylene Emission in the Aftermath of Saturn’s 2010 Northern Storm Authors: Hesman, Brigette E.; Bjoraker, G. L.; Sada, P. V.; Achterberg, R. K.; Jennings, D. E.; Lunsford, A. W.; Romani, P. N.; Fletcher, L. N.; Boyle, R. J.; Kerr, T.; Sinclair, J. A.; Nixon, C. A.; Davis, G. R.; Irwin, P. G. J. Bibcode: 2012DPS....4440306H Altcode: The massive eruption at 40N (planetographic latitude) in December 2010 has produced significant and long-lived changes in temperature and species abundances in Saturn’s northern hemisphere (Fletcher et al. 2011). The northern storm region has been observed on many occasions between January 2011 and June of 2012 by Cassini’s Composite Infrared Spectrometer (CIRS). In this time period, temperatures in regions referred to as “beacons” (warm regions in the stratosphere at certain longitudes in the storm latitude) became significantly warmer than pre-storm values of 140K. A significant finding in the beacon region has been ethylene emission; a molecule that has been challenging to detect on Saturn but is an important species in Saturn’s photochemistry. The derived ethylene profile from the CIRS data gives a C2H4 mole fraction of 5.9 ± 4.5x10-7 at 0.5 mbar. Ground-based observations were performed using the high-resolution spectrometer Celeste to study ethylene’s spectral signatures at higher spectral resolution than available with CIRS. Analysis of the May 2011 Celeste data finds a C2H4 mole fraction of 2.7 ± 0.45x10-6 at 0.1 mbar. The ethylene abundances derived from CIRS and Celeste observations are two orders of magnitude higher than predicted by photochemical models, indicating that perhaps another production mechanism is required or a loss mechanism is being inhibited. To investigate the source of ethylene in the beacon region the temporal evolution of this molecule will be presented based on data collected by CIRS, between January 2011 and June 2012, together with ground-based Celeste observations from the McMath-Pierce Telescope (May 2011), the United Kingdom Infrared Telescope (July 2011), and the NASA Infrared Telescope Facility (April 2012). References: Fletcher, L. N. et al., 2011. Thermal Structure and Dynamics of Saturn’s Northern Springtime Disturbance. Science 332, 1413-1417. Title: OSS (Outer Solar System): a fundamental and planetary physics mission to Neptune, Triton and the Kuiper Belt Authors: Christophe, B.; Spilker, L. J.; Anderson, J. D.; André, N.; Asmar, S. W.; Aurnou, J.; Banfield, D.; Barucci, A.; Bertolami, O.; Bingham, R.; Brown, P.; Cecconi, B.; Courty, J. -M.; Dittus, H.; Fletcher, L. N.; Foulon, B.; Francisco, F.; Gil, P. J. S.; Glassmeier, K. H.; Grundy, W.; Hansen, C.; Helbert, J.; Helled, R.; Hussmann, H.; Lamine, B.; Lämmerzahl, C.; Lamy, L.; Lehoucq, R.; Lenoir, B.; Levy, A.; Orton, G.; Páramos, J.; Poncy, J.; Postberg, F.; Progrebenko, S. V.; Reh, K. R.; Reynaud, S.; Robert, C.; Samain, E.; Saur, J.; Sayanagi, K. M.; Schmitz, N.; Selig, H.; Sohl, F.; Spilker, T. R.; Srama, R.; Stephan, K.; Touboul, P.; Wolf, P. Bibcode: 2012ExA....34..203C Altcode: 2011arXiv1106.0132C; 2012ExA...tmp...32C The present OSS (Outer Solar System) mission continues a long and bright tradition by associating the communities of fundamental physics and planetary sciences in a single mission with ambitious goals in both domains. OSS is an M-class mission to explore the Neptune system almost half a century after the flyby of the Voyager 2 spacecraft. Several discoveries were made by Voyager 2, including the Great Dark Spot (which has now disappeared) and Triton's geysers. Voyager 2 revealed the dynamics of Neptune's atmosphere and found four rings and evidence of ring arcs above Neptune. Benefiting from a greatly improved instrumentation, a mission as OSS would result in a striking advance in the study of the farthest planet of the solar system. Furthermore, OSS would provide a unique opportunity to visit a selected Kuiper Belt object subsequent to the passage of the Neptunian system. OSS would help consolidate the hypothesis of the origin of Triton as a Kuiper Belt object captured by Neptune, and to improve our knowledge on the formation of the solar system. The OSS probe would carry instruments allowing precise tracking of the spacecraft during the cruise. It would facilitate the best possible tests of the laws of gravity in deep space. These objectives are important for fundamental physics, as they test General Relativity, our current theoretical description of gravitation, but also for cosmology, astrophysics and planetary science, as General Relativity is used as a tool in all these domains. In particular, the models of solar system formation uses General Relativity to describe the crucial role of gravity. OSS is proposed as an international cooperation between ESA and NASA, giving the capability for ESA to launch an M-class mission towards the farthest planet of the solar system, and to a Kuiper Belt object. The proposed mission profile would allow to deliver a 500 kg class spacecraft. The design of the probe is mainly constrained by the deep space gravity test in order to minimize the perturbation of the accelerometer measurement. Title: EChO. Exoplanet characterisation observatory Authors: Tinetti, G.; Beaulieu, J. P.; Henning, T.; Meyer, M.; Micela, G.; Ribas, I.; Stam, D.; Swain, M.; Krause, O.; Ollivier, M.; Pace, E.; Swinyard, B.; Aylward, A.; van Boekel, R.; Coradini, A.; Encrenaz, T.; Snellen, I.; Zapatero-Osorio, M. R.; Bouwman, J.; Cho, J. Y. -K.; Coudé de Foresto, V.; Guillot, T.; Lopez-Morales, M.; Mueller-Wodarg, I.; Palle, E.; Selsis, F.; Sozzetti, A.; Ade, P. A. R.; Achilleos, N.; Adriani, A.; Agnor, C. B.; Afonso, C.; Allende Prieto, C.; Bakos, G.; Barber, R. J.; Barlow, M.; Batista, V.; Bernath, P.; Bézard, B.; Bordé, P.; Brown, L. R.; Cassan, A.; Cavarroc, C.; Ciaravella, A.; Cockell, C.; Coustenis, A.; Danielski, C.; Decin, L.; De Kok, R.; Demangeon, O.; Deroo, P.; Doel, P.; Drossart, P.; Fletcher, L. N.; Focardi, M.; Forget, F.; Fossey, S.; Fouqué, P.; Frith, J.; Galand, M.; Gaulme, P.; González Hernández, J. I.; Grasset, O.; Grassi, D.; Grenfell, J. L.; Griffin, M. J.; Griffith, C. A.; Grözinger, U.; Guedel, M.; Guio, P.; Hainaut, O.; Hargreaves, R.; Hauschildt, P. H.; Heng, K.; Heyrovsky, D.; Hueso, R.; Irwin, P.; Kaltenegger, L.; Kervella, P.; Kipping, D.; Koskinen, T. T.; Kovács, G.; La Barbera, A.; Lammer, H.; Lellouch, E.; Leto, G.; Lopez Morales, M.; Lopez Valverde, M. A.; Lopez-Puertas, M.; Lovis, C.; Maggio, A.; Maillard, J. P.; Maldonado Prado, J.; Marquette, J. B.; Martin-Torres, F. J.; Maxted, P.; Miller, S.; Molinari, S.; Montes, D.; Moro-Martin, A.; Moses, J. I.; Mousis, O.; Nguyen Tuong, N.; Nelson, R.; Orton, G. S.; Pantin, E.; Pascale, E.; Pezzuto, S.; Pinfield, D.; Poretti, E.; Prinja, R.; Prisinzano, L.; Rees, J. M.; Reiners, A.; Samuel, B.; Sánchez-Lavega, A.; Forcada, J. Sanz; Sasselov, D.; Savini, G.; Sicardy, B.; Smith, A.; Stixrude, L.; Strazzulla, G.; Tennyson, J.; Tessenyi, M.; Vasisht, G.; Vinatier, S.; Viti, S.; Waldmann, I.; White, G. J.; Widemann, T.; Wordsworth, R.; Yelle, R.; Yung, Y.; Yurchenko, S. N. Bibcode: 2012ExA....34..311T Altcode: 2012ExA...tmp...35T; 2011arXiv1112.2728T A dedicated mission to investigate exoplanetary atmospheres represents a major milestone in our quest to understand our place in the universe by placing our Solar System in context and by addressing the suitability of planets for the presence of life. EChO—the Exoplanet Characterisation Observatory—is a mission concept specifically geared for this purpose. EChO will provide simultaneous, multi-wavelength spectroscopic observations on a stable platform that will allow very long exposures. The use of passive cooling, few moving parts and well established technology gives a low-risk and potentially long-lived mission. EChO will build on observations by Hubble, Spitzer and ground-based telescopes, which discovered the first molecules and atoms in exoplanetary atmospheres. However, EChO's configuration and specifications are designed to study a number of systems in a consistent manner that will eliminate the ambiguities affecting prior observations. EChO will simultaneously observe a broad enough spectral region—from the visible to the mid-infrared—to constrain from one single spectrum the temperature structure of the atmosphere, the abundances of the major carbon and oxygen bearing species, the expected photochemically-produced species and magnetospheric signatures. The spectral range and resolution are tailored to separate bands belonging to up to 30 molecules and retrieve the composition and temperature structure of planetary atmospheres. The target list for EChO includes planets ranging from Jupiter-sized with equilibrium temperatures T eq up to 2,000 K, to those of a few Earth masses, with T eq u223c 300 K. The list will include planets with no Solar System analog, such as the recently discovered planets GJ1214b, whose density lies between that of terrestrial and gaseous planets, or the rocky-iron planet 55 Cnc e, with day-side temperature close to 3,000 K. As the number of detected exoplanets is growing rapidly each year, and the mass and radius of those detected steadily decreases, the target list will be constantly adjusted to include the most interesting systems. We have baselined a dispersive spectrograph design covering continuously the 0.4-16 μm spectral range in 6 channels (1 in the visible, 5 in the InfraRed), which allows the spectral resolution to be adapted from several tens to several hundreds, depending on the target brightness. The instrument will be mounted behind a 1.5 m class telescope, passively cooled to 50 K, with the instrument structure and optics passively cooled to u223c45 K. EChO will be placed in a grand halo orbit around L2. This orbit, in combination with an optimised thermal shield design, provides a highly stable thermal environment and a high degree of visibility of the sky to observe repeatedly several tens of targets over the year. Both the baseline and alternative designs have been evaluated and no critical items with Technology Readiness Level (TRL) less than 4-5 have been identified. We have also undertaken a first-order cost and development plan analysis and find that EChO is easily compatible with the ESA M-class mission framework. Title: JUpiter ICy Moons Explorer (JUICE): The ESA L1 Mission to the Jupiter System Authors: Dougherty, M. K.; Grasset, O.; Erd, C.; Titov, D.; Bunce, E.; Coustenis, A.; Blanc, M.; Coates, A.; Drossart, P.; Fletcher, L.; Hussmann, H.; Jaumann, R.; Krupp, N.; Prieto-Ballesteros, O.; Tortora, P.; Tosi, F.; Van Hoolst, T. Bibcode: 2012LPICo1683.1039D Altcode: The Jupiter Icy Moons Explorer (JUICE) mission has recently been selected by ESA as the first large mission within the Cosmic Visions 2015-2025 plan. We will introduce the mission that is being developed to thoroughly explore the Jupiter system with focus on the largest satellite, Ganymede. Title: Clouds and Hazes in Saturn's Troposphere and Stratosphere Authors: Merlet, Cecile; Irwin, P.; Fletcher, L. Bibcode: 2012DPS....4441215M Altcode: We present new results from the analysis of Saturn's near-infrared spectra measured with the Visual and Infrared Mapping Spectrometer (VIMS) instrument on the Cassini orbiter. VIMS near-infrared data are particularly relevant for the study of clouds and hazes in the troposphere and stratosphere of Saturn. Thermal emission in the 4.5-5.1 wavelength range is absorbed and scattered mainly by tropospheric clouds and radiatively active gases. The vertical structure as well as the optical and physical properties of tropospheric aerosols are obtained from Saturn's thermal emission spectra by using the retrieval algorithm Nemesis. The distribution of tropospheric phosphine and ammonia in gas phase will also be presented here. We managed to break the degeneracies inherent to the retrieval problem by analysing Saturn's thermal emission simultaneously at various viewing geometries. By using this method, we found that VIMS spectra at 4.5-5.1 microns are also sensitive to the hazes formed above the cloud layers. Saturn's reflected sunlight spectra at 0.8-3.5 microns measured with VIMS were also analysed in order to constrain the haze properties in the upper troposphere and lower stratosphere of the planet. Results from both the 0.8-3.5 and 4.5-5.1 wavelength ranges were combined to determine the cloud and haze model most consistent with VIMS spectroscopy over a wide range of viewing geometries and lighting conditions. An increase of temperature below the tropopause, often referred to as the temperature knee, was retrieved from Cassini/CIRS spectra. Seasonal variations of the knee and haze structure are compared, and as a result the assumption of local heating by the hazes to explain this feature will be discussed. Title: Analysis Of Irtf Spex Near-infrared Observations Of Uranus: Aerosol Optical Properties And Latitudinally Variable Methane Authors: Tice, Dane; Irwin, P. G. J.; Fletcher, L. N.; Teanby, N. A.; Hurley, J.; Orton, G. S.; Davis, G. R. Bibcode: 2012DPS....4441219T Altcode: We present results from the analysis of near-infrared spectra of Uranus observed in August 2009 with the SpeX spectrograph at the NASA Infrared Telescope Facility (IRTF). Spectra range from 0.8 to 1.8 μm at a spatial resolution of 0.5” and a spectral resolution of R = 1,200. This data is particularly well-suited to characterize the optical properties of aerosols in the Uranian stratosphere and upper troposphere. This is in part due to its coverage shortward of 1.0 μm where methane absorption, which dominates the features in the Uranian near-infrared spectrum, weakens slightly. Another particularly useful aspect of the data is it’s specific, highly spectrally resolved (R > 4,000) coverage of the collision-induced hydrogen quadrupole absorption band at 825 nm, enabling us to differentiate between methane abundance and cloud opacity. An optimal-estimation retrieval code, NEMESIS, is used to analyze the spectra, and atmospheric models are developed that represent good agreement with data in the full spectral range analyzed. Aerosol single-scattering albedos that reveal a strong wavelength dependence will be discussed. Additionally, an analysis of latitudinal methane variability is undertaken, utilizing two methods of analysis. First, a reflectance study from locations along the central meridian is undertaken. The spectra from these locations are centered around 825 nm, where the collision-induced absorption feature of hydrogen is utilized to distinguish between latitudinal changes in the spectrum due to aerosol opacity and those due to methane variability. Secondly, high resolution retrievals from 0.8 - 0.9 μm portion of the spectrum and spectral resolutions between R = 4,000 and 4,500 are used to make the same distinction. Both methods will be compared and discussed, as will their indications supporting a methane enrichment in the equatorial region of the planet. Title: Seasonal Variations of Temperature, Acetylene and Ethane in Saturn's Stratosphere from 2005 to 2010 Authors: Sinclair, James; Irwin, P. G. J.; Fletcher, L. N.; Moses, J. I.; Greathouse, T. K.; Friedson, A. J.; Hesman, B.; Hurley, J.; Merlet, C. Bibcode: 2012DPS....4450003S Altcode: Acetylene (C2H2) and ethane (C2H6) exemplify by-products of complex photochemistry in Saturn’s stratosphere. Their relative stability together with their strong vertical gradients in concentration allow for their use as tracers of vertical motion in Saturn’s lower stratosphere. Earlier studies of Saturn's hydrocarbons have provided only a snapshot of their behaviour with temporal variations remaining to be determined. In this study, we investigate how the thermal structure and concentrations of acetylene and ethane have evolved on Saturn with the changing season. We use FIRMAP (15.5 cm-1 spectral resolution) Cassini-CIRS observations, initially retrieve temperature and subsequently retrieve the abundances of acetylene and ethane. In comparing 2005, 2009 and 2010 results, we observe the disappearance of Saturn's southern warm polar hood with cooling of up to 18.6 K ± 0.9 K at 1.1 mbar south of 75°S (planetographic). This suggests dissipation of Saturn's south polar vortex in addition to an autumnal cooling. We observe a 20% ± 9% enrichment of acetylene and a 30% ± 10% enrichment of ethane at 2.1 mbar at 25°N, together with a 14% ± 9% depletion of acetylene and an 18% ± 7% depletion of ethane at the same altitude at 15°S. This suggests the presence of localised downwelling and upwelling at these latitudes, respectively. These vertical motions are consistent with a recently-developed GCM (global circulation model) of Saturn's tropopause and stratosphere, which predicts this pattern of upwelling and downwelling as a result of seasonally-reversing Hadley circulation. Title: Saturn’s Equatorial Plumes At Depth Observed By Cassini/VIMS and Radar: Some Ammonia-wet, Some Dry Authors: Baines, Kevin H.; Momary, T. W.; Janssen, M. A.; Ingersoll, A. P.; Fletcher, L. N.; Brown, R. H.; Buratti, B. J.; Clark, R. N.; Nicholson, P. D.; Sotin, C. Bibcode: 2012DPS....4450004B Altcode: Large (> 3000 km), discrete clouds and ammonia vapor features buried under Saturn’s ubiquotous equatorial haze have been mapped contemporaneously in Cassini/VIMS 5-micron spectra and 2-cm raster-scan imagery by the Cassini/RADAR used in passive mode. Since 2008 these features have been clearly observed on four occasions - October 14-15, 2009, December 8-10, 2009, July 24-25, 2010, and March 19-21, 2011 - from a vantage point close to the knife-edge of the rings, which reduced the ring obscuration to just ± 3 degrees of latitude about the equator. Spectral modeling indicates that the cloud features are primarily located in the 2-3 bar region, and thus are likely to be comprised of ammonia hydrosulfide (NH4SH) with perhaps an admixture of water, but not of pure ammonia condensate. RADAR imagery reveals variations of the local ammonia humidity in the same 2-3 bar region, assuming constant temperatures at depth to within a few degrees. Observations acquired March 19-21, 2011 clearly show correlations of ammonia-humid air with NH4SH cloud features, consistent with the idea that NH4SH clouds form from updrafts of ammonia-humid air, akin to the formation of convective water clouds on Earth in regions of high humidity. However, observations acquired December 8-10, 2009 show the opposite behavior, with localized cloud features largely coinciding with regions of low ammonia humidity. One possible explanation is that in the case of weaker updrafts, the rising NH3 is significantly depleted as it creates the NH4SH clouds, leaving ammonia-depleted holes in the background ammonia vapor. Alternatively, the supply of H2S in updrafts may vary relative to NH3, thus regulating the formation of both NH4SH aerosols and the left-over NH3 vapor. Finally, clouds in ammonia-dry regions may just indicate mature clouds no longer undergoing formation, as observed in the downwind “comet tail” clouds of the major northern storm of 2010-2011. Title: Line Positions, Intensities And Line Shape Parameters Of PH3 Near 4.4 µm Authors: Venkataraman, Malathy; Benner, D. C.; Kleiner, I.; Brown, L. R.; Sams, R. L.; Fletcher, L. N. Bibcode: 2012DPS....4441227V Altcode: Accurate knowledge of spectral line parameters in the 2000 to 2400 cm-1 region of PH3 is important for the CASSINI/VIMS exploration of dynamics and chemistry of Saturn and for the correct interpretation of future Jovian observations by JUNO and ESA’s newly-selected mission JUICE. Since the available intensity information for phosphine is inconsistent, we measured line positions and intensities for over 4000 individual transitions in the 2ν2, ν2+ν4, 2ν4, ν1 and the ν3 bands from analyzing high-resolution, high S/N spectra recorded at room temperature using two Fourier transform spectrometers (FTS); the Bruker IFS 125 HR FTS at PNNL and the Kitt Peak FTS at the National Solar Observatory in Arizona. In addition to line positions and intensities, self-broadened half width and self-induced pressure-shift coefficients were also measured for about 800 transitions for the various bands. The strong Coriolis and other types of interactions occurring among the various vibrational levels result in a large number of forbidden transitions as well as cause A+A- splittings in transitions with K″ that are multiples of 3. Line mixing was detected between several A+A- pairs of transitions; and self- line mixing coefficients were measured for several such pairs of transitions by applying the off-diagonal relaxation matrix formalism of Levy et al.1 A multispectrum nonlinear least squares technique2 employing a non-Voigt line shape including line mixing and speed dependence was used in fitting all the spectra simultaneously. Present results are compared with other reported values. This research is supported by NASA’s Outer Planets Research Program. References [1] A. Lévy et al., In “Spectroscopy of the Earth’s Atmosphere and Interstellar Medium”, Ed. K, Narahari Rao and A. Weber, Boston, Academic Press; p, 261-337 (1992). [2] D. C. Benner et al., J Quant. Spectrosc. Radiat. Transfer 53, 705, 1995. Title: Latitudinal Variation Of Upper Tropospheric NH3 On Saturn Derived From Cassini/cirs Far-infrared Measurements Authors: Hurley, Jane; Fletcher, L. N.; Irwin, P. G. J.; Calcutt, S. B.; Sinclair, J. A.; Merlet, C. Bibcode: 2012DPS....4441212H Altcode: Ammonia (NH3) has been detected both on Saturn and Jupiter, and although its concentration and distribution has been well-studied on Jupiter, it has proven more difficult to do so on Saturn due to higher sensitivity requirements resulting from Saturn’s lower atmospheric temperatures and the dominance of Saturn’s phosphine (PH3) which masks the NH3 signal. Using far-infrared measurements of Saturn taken by Cassini/CIRS between February 2005 and December 2010, the latitudinal variations of upper tropospheric NH3 on Saturn are studied. Sensitivity to NH3 in the far-infrared is explored to provide estimates of temperature, para-H2 and PH3, from 2.5 cm-1 spectral resolution measurements alone, 0.5 cm-1 spectral-resolution measurements alone, and 0.5 cm-1 measurements degraded to 2.5 cm-1 spectral resolution. The estimates of NH3 from these three different datasets largely agree, although there are notable differences using the high emission angle 0.5 cm-1 data, which are asserted to result from a reduction in sensitivity at higher emission angles. For low emission angles, the 0.5 cm-1-retrieved values of NH3 can be used to reproduce the 2.5 cm-1 spectra with similar efficacy as those derived directly from the 2.5 cm-1 resolution data itself, and vice versa. Using low emission angle data, NH3 is observed to have broad peak abundances at ±25° latitude, attributed to result from condensation and/or photolytic processes. Lack of data coverage at equatorial latitudes precludes analysis of NH3 abundance at less than about 10° latitude. Noise levels are not sufficient to distinguish fine zonal features, although it seems that NH3 cannot trace the zonal belt/zone structure in the upper troposphere of Saturn. Title: Photochemistry in Saturn’s Ring Shadowed Atmosphere: Production Rates of Key Atmospheric Molecules and Haze Observations Authors: Edgington, Scott G.; Atreya, S. K.; Wilson, E. H.; West, R. A.; Baines, K. H.; Bjoracker, G. L.; Fletcher, L. N.; Momary, T. W. Bibcode: 2012DPS....4441214E Altcode: Cassini has been orbiting Saturn for over eight years. During this epoch, the ring shadow has moved from shading a large portion of the northern hemisphere (the ring plane was inclined by 24 degrees relative to the Sun-Saturn vector) to shading mid-latitudes south of the equator and continues southward. At its maximum extent, the projection of the ring plane shadow onto Saturn can reach as far as 48N ( 58N at the terminator). The net result, is that the intensity of both ultraviolet and visible sunlight penetrating onto any particular northern/southern latitude will vary depending on Saturn’s tilt relative to the Sun and the optical thickness of each ring system. Our previous work has examined the variation of the solar flux as a function of solar inclination, i.e. season on Saturn. Here we report on the impact of the oscillating ring shadow on the photolysis and production rates of key hydrocarbons in Saturn’s stratosphere and upper troposphere, including ethane, acetylene, propane, benzene. We investigate the impact on production and loss rates of the long-lived, photochemical hydrocarbons leading to haze formation at several latitudes over one Saturn year. Similarly, we assess the impact on the abundance of phosphine, a disequilibrium species whose presence in the upper troposphere is a tracer of convection processes in the deep atmosphere. Along with the above, we present preliminary analysis of Cassini’s UVIS and VIMS datasets that provide an estimate of the evolving haze content of the northern hemisphere. The research described in this paper was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Title: Seasonal And Non-seasonal Variations Of Jupiter’s Atmosphere From Observations Of Thermal Emission, 1994-2011 Authors: Orton, Glenn S.; Fletcher, L.; Yanamandra-Fisher, P.; Greathouse, T.; Fisher, B.; Greco, J.; Wakefield, L.; Snead, E.; Boydstun, K.; Arzumanyan, G.; Christian, J. Bibcode: 2012DPS....4450001O Altcode: We analyzed mid-infrared images of Jupiter’s thermal emission, covering 1.5 Jovian years, acquired in discrete filters between 7.8 and 24.5 μm. The behavior of stratospheric ( 10-mbar) and tropospheric ( 100-400 mbar) temperatures is generally consistent with predictions of seasonal variability, with differences between 100-mbar temperatures ±50-60° from the equator on the order of ±2 K. Removing this effect, there appear to be long-term periodicities of tropospheric temperatures, with amplitude, phase and period dependent on latitude. Temperatures near and south of the equator vary least (< ±1 K). At some higher latitudes, the amplitudes vary by as much as ±2.5 K with peak periodicities still showing a 12-year signature with other periods ranging from 3 to 8 years. The 4-year variation of stratospheric temperatures known as the quasi-quadrennial oscillation or “QQO” (Leovy et al. 1991, Nature 354, 380) continued during this period. There were no variations of zonal mean temperatures associated with any of the “global upheaval” events that have produced dramatic changes of Jupiter’s visible appearance and cloud cover, although there are colder discrete regions associated with updrafts, e.g. the early stages of the re-darkening (“revival”) of the South Equatorial Belt (SEB) in late 2010. On the other hand increases in the visible albedos (“fades”) of belts are accompanied by increases in cloudiness at 700 mbar (most likely an NH3 ice cloud layer) and higher pressures, together with the mixing ratio of NH3 gas near 400 mbar (above its condensation level). These quantities decrease during re-darkening (“revival”) episodes, during which we note exceptions to the general correlation between dark albedos and minimal cloudiness. In contrast to all these changes, the meridional distribution of the 240-mbar para-H2 fraction appears to be time-invariant. Title: Variation of solar oscillation frequencies in solar cycle 23 and their relation to sunspot area and number Authors: Jain, R.; Tripathy, S. C.; Watson, F. T.; Fletcher, L.; Jain, K.; Hill, F. Bibcode: 2012A&A...545A..73J Altcode:
Aims: Studying the long term evolution of the solar acoustic oscillations is necessary for understanding how the large-scale solar dynamo operates. In particular, an understanding of the solar cycle variation in the frequencies of solar oscillations can provide a powerful diagnostic tool for constraining various dynamo models. In this work, we report the temporal evolution of solar oscillations for the solar cycle 23, and correlate with solar magnetic activity indices.
Methods: We use solar oscillation frequencies obtained from the Michelson Doppler Imager on board the Solar and Heliospheric Observatory, correlate them with the sunspot number provided by the international sunspot number, RI, and compare them with the sunspot number calculated with the Sunspot Tracking And Recognition Algorithm (STARA).
Results: We find that the mean frequency shifts correlate very well with the sunspot numbers obtained from two different datasets. We also find a hysteresis-type behaviour for the STARA sunspot area and mean magnetic field strength for the different phases of the solar cycle. The increase in solar oscillation frequencies precedes slightly the increase in total sunspot area and the mean magnetic field strength for the solar cycle 23. We briefly discuss the cyclic behaviour in the context of p-mode frequencies. Title: Habitability of the giant icy moons: current knowledge and future insights from the JUICE mission Authors: Grasset, O.; Prieto-Ballesteros, O.; Titov, D.; Erd, C.; Bunce, E.; Coustenis, A.; Blanc, M.; Coates, A.; Fletcher, L.; van Hoolst, T.; Hussmann, H.; Jaumann, R.; Krupp, N.; Tortora, P.; Tosi, F.; Wielders, A. Bibcode: 2012epsc.conf..925G Altcode: 2012espc.conf..925G Large satellites of gas giants, at orbits beyond the snow-line, such as Jupiter or Saturn, can contain a large amount of water (almost 45% in mass). Hydrospheres are extremely thick, ~600 km for Ganymede and Callisto, and may possess liquid layers below the icy crust. Thus, the Galilean satellites provide a conceptual basis within which new theories for understanding habitability can be constructed. Measurements from the Voyager and Galileo spacecraft revealed the potential of these satellites in this context. The JUpiter Icy moons Explorer (JUICE) will greatly enhance our understanding of their potential habitability. It is known, even at Earth where life mostly depends on solar energy, that habitats exist deep in the oceans in eternal darkness feeding on chemical energy. Aqueous layers are suspected below the icy crusts of the moons, which possess similar physical characteristics than Earth's deep oceans. Since they are certainly very stable through time, and because complex chemistry and energy sources may be available, life may have originated within such subsurface habitats despite the hostile surface conditions. Liquid water reservoirs have been proposed on Ganymede, Europa and Callisto from geophysical models, based on Galileo observations. These oceans that are covered by ice shells exist independently of the input of stellar energy, and are located well outside the conventional habitable zone of the Sun. Considering the pressure range encountered within the icy moons, four different scenarios can be defined. These result from varying thicknesses of the water ice layers and the liquid ocean with respect to the silicate floor (Figure 1). Case 2 in Figure 1 is highly probable for the largest moons (Ganymede and Callisto), while case 3 is more probable for Europa and smaller icy moons if they host liquid reservoirs such as has been discovered at Enceladus. Europa's ocean is unique because it may be in contact with the rock layer. This substrate may be geologically active and affected by hydrothermal processes, similar to the terrestrial sea floor. This may enhance habitability conditions since the rock layer could release chemical elements and energy to the surrounding water ocean. Differentiation of the rock could be responsible for the presence of salts and other essential elements in the ocean, and produce the low albedo terrains seen on the surface. An estimation of the minimal thickness of the icy crust over the most active regions of Europa is among the measurement goals of JUICE and this will provide important constraints on the subsurface structure of the moon. On the larger icy moons, Ganymede and Callisto, where internal pressures are sufficient to allow for the formation of high pressure ice phases, the existence of an ocean suggests that it should be enclosed between thick ice layers. Chemical and energy exchanges between the rocky layer and the ocean, which are so important for habitability, cannot be ruled out but would imply efficient transport processes through the thick high pressure icy layer. Such processes are indeed possible but not as clearcut as the exchanges that can be envisaged for Europa. Icy and liquid layers are probably not solely constituted of pure H2O. Many other compounds such as salts, or CO2 have been observed on the surfaces and may emerge from the deep interiors of the moons. Volatiles, organics and minerals solidified from the aqueous cryo-magmas, could be detected remotely from an orbiting spacecraft. Analysis of these materials will give great insight to the physico-chemistry and composition of the deep environments. But such organic matter and other surface compounds will experience a different radiation environment at Europa than at Ganymede (due to the difference in radial distance from Jupiter) and thus may suffer different alteration processes, influencing their detection on the surface. Measurements from terrains on both Europa and Ganymede will allow a comparison of different radiation doses and terrain ages from similar materials. JUICE will address key areas that emerge in the study of habitable worlds around gas giants including constraints on the volume of liquid water in the Jovian system. The mission will also establish the inventory of biologically essential elements on the surfaces of the icy moons, and determine the magnitude of their transport among the moons which exchange material as a result of volcanism, sputtering, and impacts. The mission may also allow us to infer environmental properties such as the pH, salinity, and water activity of the oceans and will investigate the effects of radiation on the detectability of surface organics. Title: Temperature Structure and Composition of Uranus Derived from Observations by ISO, Spitzer, Herschel, and Ground-Based Telescopes Coupled with Photochemical Models Authors: Orton, G.; Fletcher, L.; Feuchtgruber, H.; Lellouch, E.; Moreno, R.; Encrenaz, T.; Hartogh, P.; Jarchow, C.; Moses, J.; Burgdorg, M.; Hammel, H.; Line, M.; Mainzer, A.; Hofstadter, M.; Sandell, G.; Dowell, D. Bibcode: 2012epsc.conf..289O Altcode: 2012espc.conf..289O The combined power of absolutely calibrated photometry and spectroscopy of Uranus has been combined to create self-consistent models of its global-mean temperature profile, bulk composition, and vertical distribution of gases. Title: The Evolution of Saturn's Stratospheric Beacon 2011-2012 Authors: Fletcher, L. N.; Hesman, B. E.; Achterberg, R. K.; Bjoraker, G.; Gorius, N.; Irwin, P. G. J.; Hurley, J.; Sinclair, J.; Orton, G. S.; Read, P. L.; Flasar, F. M.; Legarreta, J.; Garcia-Melendo, E.; Sanchez-Lavega, A. Bibcode: 2012epsc.conf..313F Altcode: 2012espc.conf..313F The slow warming of Saturn's springtime stratosphere was spectacularly disrupted in 2010 by the eruption of a planetary-scale tropospheric storm system [1-3]. The roiling, convective motions of the tropospheric cloud decks had a dramatic influence on the atmospheric temperatures and composition many hundreds of kilometers higher up, in Saturn's stably stratified middle atmosphere. Energy transported from the tropospheric storm was deposited in two warm stratospheric airmasses, known as beacons B1 and B2 because of their brightness in thermal infrared imaging. These features were observed throughout 2011 and 2012 using a combination of 7- 1000 μm spectroscopic mapping from the Cassini Composite Infrared Spectrometer (CIRS, [1]) and filtered 7-25 μm imaging from the VLT/VISIR and IRTF/MIRSI thermal-infrared instruments. These infrared observations are used to discuss the motions, temperatures, composition, winds and stability of these newly discovered phenomena in Saturn's stratosphere. Title: Examining Rotational Variability in the Upper Tropospheres and Lower Stratospheres of Uranus and Neptune from Herschel PACS OT1 Observations Authors: Orton, G.; Feuchtgruber, H.; Fletcher, L.; Lellouch, E.; Moreno, R.; Encrenaz, T.; Billebaud, F.; Cavalie, T.; Dobreijevcic, M.; Decin, L.; Hartogh, P.; Jarchow, C.; Lara, L. M.; Liu, J. Bibcode: 2012epsc.conf..867O Altcode: 2012espc.conf..867O The power of high-resolution submillimeter spectroscopy of Uranus and Neptune was put to use to survey the rotational variability of stratospheric and tropospheric constituents of their atmospheres. Title: Exploring the Atmospheres of the Ice Giants Authors: Fletcher, L. N.; Orton, G. S.; Hofstadter, M.; Irwin, P. G. J.; de Pater, I. Bibcode: 2012epsc.conf..862F Altcode: 2012espc.conf..862F Of all the planets in our solar system, the two ice giants Uranus and Neptune remain the least explored and poorly understood because of their great distance from Earth. And yet they occupy a unique position in the hierarchy of planetary types, being intermediate between gas giants with their enormous hydrogen-helium envelopes, and terrestrial-sized worlds and Super Earths. These ice giants, so-called because their bulk compositions are dominated by heavier elements, are a true frontier of our exploration of planetary atmospheres, having been visited only once by Voyager 2 in 1986 and 1989, and may be representative of a whole class of planetary objects throughout our galaxy. Even though Earth-based observations (ISO, Spitzer, Herschel, ground-based) have improved dramatically in the decades since Voyager 2, many questions about this unexplored region of our Solar System remain unanswered. Voyager revealed unexpected differences in the appearance, composition, dynamics and chemistry between these two worlds, which could ultimately help us to understand how planetary atmospheres form and evolve as a function of distance from their host stars. This talk will review our present understanding of ice giant atmospheres, and assess the key questions to be answered by future exploration. Title: The application of new methane line absorption data to Gemini-N/NIFS and KPNO/FTS observations of Uranus' near-infrared spectrum Authors: Irwin, P. G. J.; de Bergh, C.; Courtin, R.; Bézard, B.; Teanby, N. A.; Davis, G. R.; Fletcher, L. N.; Orton, G. S.; Calcutt, S. B.; Tice, D.; Hurley, J. Bibcode: 2012Icar..220..369I Altcode: New line data describing the absorption of CH4 and CH3D from 1.26 to 1.71 μm (Campargue, A., Wang, L., Mondelain, D., Kassi, S., Bézard, B., Lellouch, E., Coustenis, A., de Bergh, C., Hirtzig, M., Drossart, P. [2012]. Icarus 219, 110-128), building upon previous papers by Campargue et al. (Campargue, A., Wang, L., Kassi, S., Masat, M., Votava, O. [2010]. J. Quant. Spectrosc. Radiat. Transfer 111, 1141-1151; Wang, L., Kassi, S., Campargue, A. [2010]. J. Quant. Spectrosc. Radiat. Transfer 111, 1130-1140; Wang, L., Kassi, S., Liu, A.W., Hu, S.M., Campargue, A. [2011]. J. Quant. Spectrosc. Radiat. Transfer 112, 937-951)) have been applied to the analysis of Gemini-N/NIFS observations of Uranus made in 2010 and compared with earlier disc-averaged observations made by KPNO/FTS in 1982. The new line data are found to improve greatly the fit to the observed spectra and present a huge advance over previous methane absorption tables by allowing us to determine the CH3D/CH4 ratio and also start to break the degeneracy between methane abundance and cloud top height. The best fits are obtained if the cloud particles in the main cloud deck at the 2-3 bar level become less scattering with wavelength across the 1.4-1.6 μm region and we have modelled this variation here by varying the extinction cross-section and single-scattering albedo of the particles. Applying the new line data to the NIFS spectra of Uranus, we determine a new estimate of the CH3D/CH4 ratio of 2.9-0.5+0.9×10-4, which is consistent with the estimate of de Bergh et al. (de Bergh, C., Lutz, B.L., Owen, T., Brault, J., Chauville, J. [1986]. Astrophys. J. 311, 501-510) of 3.6-2.8+3.6×10-4, made by fitting a disc-averaged KPNO/FTS spectrum measured in 1982, but much better constrained. The NIFS observations made in 2010 have been disc-averaged and compared with the 1982 KPNO/FTS spectrum and found to be in excellent agreement. Using k-tables fitted to the new line data, the central meridian observations of Uranus' H-band spectrum (1.49-1.64 μm) made by Gemini-N/NIFS in 2010 have been reanalyzed. The use of the new methane absorption coefficients and the modified scattering properties of the cloud particles in the main cloud deck appears to break the degeneracy between cloud height and methane abundance immediately above it in this spectral region and we find that both vary with latitude across Uranus' disc. Overall, we find that the main cloud deck becomes higher, but thinner from equator to poles, with a local maximum in cloud top height in the circumpolar zones at 45°N and 45°S. At the same time, using the 'D' temperature pressure profile of Lindal et al. (Lindal, G.F., Lyons, J.R., Sweetnam, D.N., Eshleman, V.R., Hinson, D.P. [1987]. J. Geophys. Res. 92, 14987-15001) and a deep methane abundance of 1.6% (Baines, K.H., Mickelson, M.E., Larson, L.E., Ferguson, D.W. [1995]. Icarus 144, 328-340) we find that the relative humidity of methane is high near the equator (∼60%) and decreases sharply towards the poles, except near the circumpolar zone at 45°N, which has brightened steadily since 2007, and where there is a local maximum in methane relative humidity. In tests conducted with the warmer 'F1' profile of Sromovsky et al. (2011) we find a similar variation of methane abundance above the main cloud, although for this warmer temperature profile this abundance is dependent mostly on the fitted deep methane mole fraction. Title: Charge-exchange Limits on Low-energy α-particle Fluxes in Solar Flares Authors: Hudson, H. S.; Fletcher, L.; MacKinnon, A. L.; Woods, T. N. Bibcode: 2012ApJ...752...84H Altcode: 2014arXiv1401.6477H This paper reports on a search for flare emission via charge-exchange radiation in the wings of the Lyα line of He II at 304 Å, as originally suggested for hydrogen by Orrall & Zirker. Via this mechanism a primary α particle that penetrates into the neutral chromosphere can pick up an atomic electron and emit in the He II bound-bound spectrum before it stops. The Extreme-ultraviolet Variability Experiment on board the Solar Dynamics Observatory gives us our first chance to search for this effect systematically. The Orrall-Zirker mechanism has great importance for flare physics because of the essential roles that particle acceleration plays; this mechanism is one of the few proposed that would allow remote sensing of primary accelerated particles below a few MeV nucleon-1. We study 10 events in total, including the γ-ray events SOL2010-06-12 (M2.0) and SOL2011-02-24 (M3.5) (the latter a limb flare), seven X-class flares, and one prominent M-class event that produced solar energetic particles. The absence of charge-exchange line wings may point to a need for more complete theoretical work. Some of the events do have broadband signatures, which could correspond to continua from other origins, but these do not have the spectral signatures expected from the Orrall-Zirker mechanism. Title: Line Parameters of the PH_3 Pentad in the 4-5 μm Region Authors: Devi, V. Malathy; Benner, D. Chris; Kleiner, I.; Sams, R. L.; Blake, T. A.; Brown, Linda R.; Fletcher, L. N. Bibcode: 2012mss..confEFA08D Altcode: Line positions, intensities and line shape parameters are reported for four bands of phosphine between 2150 and 2400 cm-1 in order to improve the spectroscopic database for remote sensing of the giant planets. Knowledge of PH_3 in this spectral region is important for Cassini/VIMS exploration of dynamics and chemistry on Saturn, as well as for interpreting the near-IR data from Juno and ESA's proposed Jupiter mission. For this study, five high-resolution (0.0023 cm-1), high signal-to-noise (>2000) spectra of pure PH_3 were recorded at room temperature (298.2 K) with the Bruker IFS 125HR Fourier transform spectrometer at Pacific Northwest National Laboratory. Individual line parameters were retrieved by multispectrum fitting of all five spectra simultaneously. Positions and intensities were measured for over 3100 transitions. The rotational quantum numbers of measured lines go as high as J''=16 and K''=15 in the ν_3 and ν_1 bands; some lines of the weaker bands 2ν_4 and ν_2+ν_4 are also reported. The measured positions and intensities are compared to new theoretical calculations of the pentad. Lorentz self-broadened width and pressure-induced shift coefficients of many transitions were also obtained, along with speed dependence parameters. Line mixing coefficients were determined for several A+A- pairs of transitions for K''=3, 6, and 9.

Research described in this paper was performed at the College of William and Mary and the Jet Propulsion Laboratory, California Institute of Technology, under contracts and cooperative agreements with the National Aeronautics and Space Administration. L. Fletcher acknowledges support from a Glasstone Science Fellowship.

D. C. Benner, C. P. Rinsland, V. Malathy Devi, M. A. H. Smith and D. A. Atkins, JQSRT 53 (1995) 705-721. Title: Numerical Simulations of Chromospheric Hard X-Ray Source Sizes in Solar Flares Authors: Battaglia, M.; Kontar, E. P.; Fletcher, L.; MacKinnon, A. L. Bibcode: 2012ApJ...752....4B Altcode: 2012arXiv1204.1151B X-ray observations are a powerful diagnostic tool for transport, acceleration, and heating of electrons in solar flares. Height and size measurements of X-ray footpoint sources can be used to determine the chromospheric density and constrain the parameters of magnetic field convergence and electron pitch-angle evolution. We investigate the influence of the chromospheric density, magnetic mirroring, and collisional pitch-angle scattering on the size of X-ray sources. The time-independent Fokker-Planck equation for electron transport is solved numerically and analytically to find the electron distribution as a function of height above the photosphere. From this distribution, the expected X-ray flux as a function of height, its peak height, and full width at half-maximum are calculated and compared with RHESSI observations. A purely instrumental explanation for the observed source size was ruled out by using simulated RHESSI images. We find that magnetic mirroring and collisional pitch-angle scattering tend to change the electron flux such that electrons are stopped higher in the atmosphere compared with the simple case with collisional energy loss only. However, the resulting X-ray flux is dominated by the density structure in the chromosphere and only marginal increases in source width are found. Very high loop densities (>1011 cm-3) could explain the observed sizes at higher energies, but are unrealistic and would result in no footpoint emission below about 40 keV, contrary to observations. We conclude that within a monolithic density model the vertical sizes are given mostly by the density scale height and are predicted smaller than the RHESSI results show. Title: Flare Ribbons In The Early Phase Of An SDO Flare: Emission Measure And Energetics Authors: Fletcher, Lyndsay; Hannah, I. G.; Hudson, H. S.; Innes, D. E. Bibcode: 2012AAS...22050902F Altcode: We report on the M1.0 flare of 7th August 2010, which displayed extended early phase chromospheric ribbons, well observed by SDO/AIA and RHESSI. Most large flares saturate rapidly in the high-temperature AIA channels, however this event could be followed in unsaturated AIA images for ten minutes in the build-up to and first few minutes of the impulsive phase. Analysis of GOES, RHESSI and SDO/AIA demonstrates the presence of high temperature ( 10MK), compact plasma volumes in the chromospheric flare ribbons, with a column emission measure of on average 3-7 x 1028 cm-5. We construct a time-resolved energy budget for the ribbon plasma, including also SDO/EVE data, and discuss the implications of the observed ribbon properties for flare energisation.

This work was supported by the UK’s Science and Technology Facilities Council (ST/1001801), and by the European Commission through the FP7 HESPE project (FP7-2010-SPACE-263086). Title: Solar Flare Observations of the EUV Continua Authors: Milligan, Ryan O.; Chamberlin, P.; Hudson, H.; Woods, T.; Mathioudakis, M.; Fletcher, L.; Kowalski, A.; Keenan, F. Bibcode: 2012AAS...22052105M Altcode: Recent solar flare simulations suggest that the energy deposited in the chromosphere by nonthermal electrons during a flare's impulsive phase is re-emitted in the form of recombination (free-bound) continua, in particular, the Lyman, Balmer, and Paschen continua of hydrogen, and the He I and He II continua (Allred et al. 2005). However, definitive observations of free-bound emission during solar flares have been scarce in recent years as many modern, space-based instruments do not have the required sensitivity, wavelength coverage, or duty cycle. With the launch of SDO, these observations are now routinely available thanks to the EUV Variability Experiment (EVE) instrument. Here we present unambiguous, spectrally and temporally resolved detections of enhanced free-free and free-bound continua during the first X-class solar flare of Solar Cycle 24. While we find that the flare energy in the EVE spectral range amounts to at most a few percent of the total flare energy, these findings highlight the capability of EVE in giving us the first comprehensive look at these diagnostically important continuum components. Title: Solar Chromospheric Flares: Energy Release, Transport and Radiation Authors: Fletcher, L. Bibcode: 2012ASPC..456..183F Altcode: 2012arXiv1207.0384F This paper presents an overview of some recent observational and theoretical results on solar flares, with an emphasis on flare impulsive-phase chromospheric properties, including: electron diagnostics, optical and UV emission, and discoveries made by the Hinode mission, especially in the EUV. A brief perspective on future observations and theoretical requirements is also given. Title: Dynamical Heating In Flares Observed With SDO/AIA & RHESSI Authors: Hannah, Iain; Fletcher, L.; Kontar, E. P. Bibcode: 2012AAS...22032202H Altcode: The spatial and temporal resolution of SDO/AIA data presents an unprecedented view of the dynamics of heating during solar flares. This combined with the non-thermal energetics from RHESSI hard X-ray imaging and spectroscopy provides constraints on the flaring energy release. The recently implemented regularized inversion method (Hannah & Kontar A&A 2012) robustly recovers the underlying thermal distribution (the Differential Emission Measure, DEM) of the coronal plasma from SDO/AIA images. Crucially it is not limited to the isothermal or Gaussian-model approximation that some other approaches depend upon. Our method provides the uncertainties in the DEM and is computationally quick, producing DEMs per pixel for a series of SDO/AIA images allowing temperature maps and movies to be created. We use the regularized inversion method to study the temporal and spatial evolution of the plasma heating in flares and show how the non-thermal energy relates to this. We also investigate how the calibration errors/uncertainties affect the inferred DEMs and errors. Title: Observations of upper tropospheric acetylene on Saturn: No apparent correlation with 2000 km-sized thunderstorms Authors: Hurley, J.; Irwin, P. G. J.; Fletcher, L. N.; Moses, J. I.; Hesman, B.; Sinclair, J.; Merlet, C. Bibcode: 2012P&SS...65...21H Altcode: Thunderstorm activity has been observed on Saturn via radio emissions from lightning discharges and optical detections of the lightning flashes on the planet's nightside. Thunderstorms provide extreme environments in which specific atmospheric chemistry can be induced-namely through energy release via lightning discharges, and fast vertical transport resulting in rapid advection of tropospheric species. It is thus theorised that certain atmospheric trace species - such as C2H2, HCN, and CO - can be generated in the troposphere by large bursts of energy in the form of lightning, and transported upward towards the upper troposphere by the extreme dynamics of thunderstorms, where they should be observable by satellite instruments. In this work, high-spectral-resolution Cassini/CIRS observations from October 2005 through April 2009 are used to study whether there is an observable increase in upper tropospheric acetylene in regions of known normal thunderstorm activity. Using both individual measurements in which there is known thunderstorm activity, as well as large coadditions of data to study latitudinal-dependencies over the full disc, no systematic enhancement in upper tropospheric (100 mbar) C2H2 was detected around regions in which there are known occurrences of normally sized (2000 km) thunderstorms, or in normally sized thunderstorm-prone regions such as 40°S. It is likely that the magnitude of the enhancement theorised is too generous or that enhancements are not advected into the upper troposphere as vertical mixing rates in models would suggest, since Cassini/CIRS can only detect C2H2 above the 200 mbar level-although the massive northern hemisphere thunderstorm of 2010/2011 seems able to decrease stratospheric concentrations of C2H2. From this, it can be asserted that lightning from normal thunderstorm activity cannot be the key source for upper tropospheric C2H2 on Saturn, since the upper-tropospheric concentrations retrieved agree with the concentrations stemming from the photolysis of CH4 (2-3 ppbv) from solar radiation penetrating through the Saturnian atmosphere, with an upper limit for lightning-induced C2H2 volume mixing ratio of 10-9. Title: Investigating the Structure of Impulsive Phase Footpoints Authors: Graham, David; Hannah, I.; Fletcher, L.; Milligan, R. Bibcode: 2012AAS...22050903G Altcode: The location of flare heating in the solar atmosphere is imperative to understanding the heating mechanism. The differential emission measure is an important tool in understanding the properties of flaring plasma. However, determining the DEM of impulsive phase footpoints has been difficult in the past without sufficient spatial resolution to resolve footpoints from loop structures, and a lack of spectral and temporal coverage. We use the capabilities of Hinode/EIS to present the first DEMs from the impulsive phase of a number of flare footpoints. Observations were chosen from a period when EIS telemetry was at its best and analysed using a new regularised inversion method (Hannah & Kontar 2012). We find a peak temperature in the DEM of around 7 MK with emission measures peaking between 10^28 and 10^29 cm-5, indicating a substantial presence of plasma at 'coronal' temperatures within the footpoint. In addition to the DEM, we perform a wide range of density diagnostics from transition region to coronal temperatures, allowing us estimate where in the atmosphere the EUV emission originates. Title: Break up of returning plasma after the 7 June 2011 filament eruption by Rayleigh-Taylor instabilities Authors: Innes, D. E.; Cameron, R. H.; Fletcher, L.; Inhester, B.; Solanki, S. K. Bibcode: 2012A&A...540L..10I Altcode: 2012arXiv1202.4981I Context. A prominence eruption on 7 June 2011 produced spectacular curtains of plasma falling through the lower corona. At the solar surface they created an incredible display of extreme ultraviolet brightenings.
Aims: To identify and analyze some of the local instabilities which produce structure in the falling plasma.
Methods: The structures were investigated using SDO/AIA 171 Å and 193 Å images in which the falling plasma appeared dark against the bright coronal emission.
Results: Several instances of the Rayleigh-Taylor instability were investigated. In two cases the Alfvén velocity associated with the dense plasma could be estimated from the separation of the Rayleigh-Taylor fingers. A second type of feature, which has the appearance of self-similar branching horns was discussed.

Appendix A and two movies are available in electronic form at http://www.aanda.org Title: Commission 10: Solar Activity Authors: van Driel-Gesztelyi, Lidia; Schrijver, Carolus J.; Klimchuk, James A.; Charbonneau, Paul; Fletcher, Lyndsay; Hasan, S. Sirajul; Hudson, Hugh S.; Kusano, Kanya; Mandrini, Cristina H.; Peter, Hardi; Vršnak, Bojan; Yan, Yihua Bibcode: 2012IAUTA..28...69V Altcode: Commission 10 of the International Astronomical Union has more than 650 members who study a wide range of activity phenomena produced by our nearest star, the Sun. Solar activity is intrinsically related to solar magnetic fields and encompasses events from the smallest energy releases (nano- or even picoflares) to the largest eruptions in the Solar System, coronal mass ejections (CMEs), which propagate into the Heliosphere reaching the Earth and beyond. Solar activity is manifested in the appearance of sunspot groups or active regions, which are the principal sources of activity phenomena from the emergence of their magnetic flux through their dispersion and decay. The period 2008-2009 saw an unanticipated extended solar cycle minimum and unprecedentedly weak polar-cap and heliospheric field. Associated with that was the 2009 historical maximum in galactic cosmic rays flux since measurements begun in the middle of the 20th Century. Since then Cycle 24 has re-started solar activity producing some spectacular eruptions observed with a fleet of spacecraft and ground-based facilities. In the last triennium major advances in our knowledge and understanding of solar activity were due to continuing success of space missions as SOHO, Hinode, RHESSI and the twin STEREO spacecraft, further enriched by the breathtaking images of the solar atmosphere produced by the Solar Dynamic Observatory (SDO) launched on 11 February 2010 in the framework of NASA's Living with a Star program. In August 2012, at the time of the IAU General Assembly in Beijing when the mandate of this Commission ends, we will be in the unique position to have for the first time a full 3-D view of the Sun and solar activity phenomena provided by the twin STEREO missions about 120 degrees behind and ahead of Earth and other spacecraft around the Earth and ground-based observatories. These new observational insights are continuously posing new questions, inspiring and advancing theoretical analysis and modelling, improving our understanding of the physics underlying magnetic activity phenomena. Commission 10 reports on a vigorously evolving field of research produced by a large community. The number of refereed publications containing `Sun', `heliosphere', or a synonym in their abstracts continued the steady growth seen over the preceding decades, reaching about 2000 in the years 2008-2010, with a total of close to 4000 unique authors. This report, however, has its limitations and it is inherently incomplete, as it was prepared jointly by the members of the Organising Committee of Commission 10 (see the names of the primary contributors to the sections indicated in parentheses) reflecting their fields of expertise and interest. Nevertheless, we believe that it is a representative sample of significant new results obtained during the last triennium in the field of solar activity. Title: Solar Particle Acceleration Radiation and Kinetics (SPARK). A mission to understand the nature of particle acceleration Authors: Matthews, Sarah A.; Williams, David R.; Klein, Karl-Ludwig; Kontar, Eduard P.; Smith, David M.; Lagg, Andreas; Krucker, Sam; Hurford, Gordon J.; Vilmer, Nicole; MacKinnon, Alexander L.; Zharkova, Valentina V.; Fletcher, Lyndsay; Hannah, Iain G.; Browning, Philippa K.; Innes, Davina E.; Trottet, Gerard; Foullon, Clare; Nakariakov, Valery M.; Green, Lucie M.; Lamoureux, Herve; Forsyth, Colin; Walton, David M.; Mathioudakis, Mihalis; Gandorfer, Achim; Martinez-Pillet, Valentin; Limousin, Olivier; Verwichte, Erwin; Dalla, Silvia; Mann, Gottfried; Aurass, Henri; Neukirch, Thomas Bibcode: 2012ExA....33..237M Altcode: 2011ExA...tmp..124M Energetic particles are critical components of plasma populations found throughout the universe. In many cases particles are accelerated to relativistic energies and represent a substantial fraction of the total energy of the system, thus requiring extremely efficient acceleration processes. The production of accelerated particles also appears coupled to magnetic field evolution in astrophysical plasmas through the turbulent magnetic fields produced by diffusive shock acceleration. Particle acceleration is thus a key component in helping to understand the origin and evolution of magnetic structures in, e.g. galaxies. The proximity of the Sun and the range of high-resolution diagnostics available within the solar atmosphere offers unique opportunities to study the processes involved in particle acceleration through the use of a combination of remote sensing observations of the radiative signatures of accelerated particles, and of their plasma and magnetic environment. The SPARK concept targets the broad range of energy, spatial and temporal scales over which particle acceleration occurs in the solar atmosphere, in order to determine how and where energetic particles are accelerated. SPARK combines highly complementary imaging and spectroscopic observations of radiation from energetic electrons, protons and ions set in their plasma and magnetic context. The payload comprises focusing-optics X-ray imaging covering the range from 1 to 60 keV; indirect HXR imaging and spectroscopy from 5 to 200 keV, γ-ray spectroscopic imaging with high-resolution LaBr3 scintillators, and photometry and source localisation at far-infrared wavelengths. The plasma environment of the regions of acceleration and interaction will be probed using soft X-ray imaging of the corona and vector magnetography of the photosphere and chromosphere. SPARK is designed for solar research. However, in addition it will be able to provide exciting new insights into the origin of particle acceleration in other regimes, including terrestrial gamma-ray flashes (TGF), the origin of γ-ray bursts, and the possible existence of axions. Title: Examining Rotational Variability in the Upper Tropospheres and Lower Stratospheres of Uranus and Neptune from Herschel PACS OT1 Observations: Implications for the Stability of Temperature and Compositional Structure Authors: Orton, G.; Feuchtgruber, H.; Fletcher, L.; Lellouch, E.; Moreno, R.; Billebaud, F.; Cavalie, T.; Decin, L.; Dobreijecvic, M.; Encrenaz, T.; Hartogh, P.; Jarchow, C.; Lara, L. M.; Liu, J. Bibcode: 2012EGUGA..14.3434O Altcode: The power of high-resolution submillimeter spectroscopy of Uranus and Neptune was put to use to survey the rotational variability of stratospheric and tropospheric constituents of their atmospheres. These observations were motivated by the surprising discovery of as much as 12% rotational variability of emission from stratospheric constituents in the atmosphere of Uranus by the Spitzer Infrared Spectrometer and the detection of spatial variability in thermal images of Neptune's stratospheric emission (Orton et al. 2007, Astron. & Astrophys 473, L3). Our observing program consisted of three separate sequences of observations to look at the strongest lines of H2O in the high-resolution PACS spectra of both planets, whose upwelling radiance emerges from the same vertical region as the Spitzer IRS observations of Uranus and ground-based images of Neptune, and the strongest line of CH4 in the PACS spectrum of Neptune. We omitted measurements of CH4 lines in Uranus, which are almost non-detectable. We added the strongest HD line in Uranus to measure variability of tropospheric temperatures that could modulate stratospheric CH4 abundances through local cold-trapping and the strongest two HD lines in Neptune (Lellouch et al. 2010, Astron. & Astrophys. 518, L152) that determine both the tropopause temperature to limit local cold-trapping efficacy and the lower stratospheric temperature, to help differentiate between longitudinal variability of stratospheric H2O and CH4 abundances vs. temperatures. These were repeated over the 17-hour interval that is common to the equatorial rotation periods of both Uranus and Neptune. Although these lines had already been observed in Uranus and Neptune by PACS, no repeat measurements had ever been made to determine longitudinal variability. The observations were consistent with previous measurements, but no significant rotational variability was detected. It is possible that the absence of rotational variability in the HD and CH4 lines is because variability is confined to very low pressures, e.g. much lower than a microbar. However, the absence of variable emission from high-altitude exogenic H2O vapor is harder to explain, unless the variability seen in Uranus by Spitzer and in Neptune from the VLT, is not the result of variations in temperature by in the hydrocarbon abundances. Alternatively, the stratospheres of both planets are variable in time. The cause of such variability is unknown, but spatially confined outbursts have been detected in the visible and near infrared, and they may have as much influence on the stratosphere of Uranus as the great springtime storm in Saturn's northern hemisphere, creating a strong, localized "beacon" of thermal radiation (cf. Fletcher et al. 2011, Science, 332,1413) that could dominate the emission observed over the hemisphere. Title: Observations of Enhanced Extreme Ultraviolet Continua during an X-Class Solar Flare Using SDO/EVE Authors: Milligan, Ryan O.; Chamberlin, Phillip C.; Hudson, Hugh S.; Woods, Thomas N.; Mathioudakis, Mihalis; Fletcher, Lyndsay; Kowalski, Adam F.; Keenan, Francis P. Bibcode: 2012ApJ...748L..14M Altcode: 2012arXiv1202.1731M Observations of extreme ultraviolet (EUV) emission from an X-class solar flare that occurred on 2011 February 15 at 01:44 UT are presented, obtained using the EUV Variability Experiment (EVE) on board the Solar Dynamics Observatory. The complete EVE spectral range covers the free-bound continua of H I (Lyman continuum), He I, and He II, with recombination edges at 91.2, 50.4, and 22.8 nm, respectively. By fitting the wavelength ranges blueward of each recombination edge with an exponential function, light curves of each of the integrated continua were generated over the course of the flare, as was emission from the free-free continuum (6.5-37 nm). The He II 30.4 nm and Lyα 121.6 nm lines, and soft X-ray (SXR; 0.1-0.8 nm) emission from GOES are also included for comparison. Each free-bound continuum was found to have a rapid rise phase at the flare onset similar to that seen in the 25-50 keV light curves from RHESSI, suggesting that they were formed by recombination with free electrons in the chromosphere. However, the free-free emission exhibited a slower rise phase seen also in the SXR emission from GOES, implying a predominantly coronal origin. By integrating over the entire flare the total energy emitted via each process was determined. We find that the flare energy in the EVE spectral range amounts to at most a few percent of the total flare energy, but EVE gives us a first comprehensive look at these diagnostically important continuum components. Title: Momentum Distribution in Solar Flare Processes Authors: Hudson, H. S.; Fletcher, L.; Fisher, G. H.; Abbett, W. P.; Russell, A. Bibcode: 2012SoPh..277...77H Altcode: We discuss the consequences of momentum conservation in processes related to solar flares and coronal mass ejections (CMEs), in particular describing the relative importance of vertical impulses that could contribute to the excitation of seismic waves ("sunquakes"). The initial impulse associated with the primary flare energy transport in the impulsive phase contains sufficient momentum, as do the impulses associated with the acceleration of the evaporation flow (the chromospheric shock) or the CME itself. We note that the deceleration of the evaporative flow, as coronal closed fields arrest it, will tend to produce an opposite impulse, reducing the energy coupling into the interior. The actual mechanism of the coupling remains unclear at present. Title: The role of filament activation in a solar eruption Authors: Rubio da Costa, F.; Zuccarello, F.; Fletcher, L.; Romano, P.; Labrosse, N. Bibcode: 2012A&A...539A..27R Altcode: 2014arXiv1412.1858R Context. Observations show that the mutual relationship between filament eruptions and solar flares cannot be described in terms of an unique scenario. In some cases, the eruption of a filament appears to trigger a flare, while in others the observations are more consistent with magnetic reconnection that produces both the flare observational signatures (e.g., ribbons, plasma jets, post-flare loops, etc.) and later the destabilization and eruption of a filament.
Aims: Contributing to a better comprehension of the role played by filament eruptions in solar flares, we study an event which occurred in NOAA 8471, where a flare and the activation of (at least) two filaments were observed on 28 February 1999.
Methods: By using imaging data acquired in the 1216, 1600, 171 and 195 Å TRACE channels and by BBSO in the continnum and in the Hα line, a morphological study of the event is carried out. Moreover, using TRACE 1216 and 1600 Å data, an estimate of the "pure" Lyα power is obtained. The extrapolation of the magnetic field lines is done using the SOHO/MDI magnetograms and assuming a potential field.
Results: Initially an area hosting a filament located over a δ spot becomes brighter than the surroundings, both in the chromosphere and in the corona. This area increases in brightness and extension, eventually assuming a two-ribbon morphology, until it reaches the eastern part of the active region. Here a second filament becomes activated and the brightening propagates to the south, passing over a large supergranular cell. The potential magnetic field extrapolation indicates that the field line connectivity changes after the flare.
Conclusions: The event is triggered by the destabilization of a filament located between the two polarities of a δ spot. This destabilization involves the magnetic arcades of the active region and causes the eruption of a second filament, that gives rise to a CME and to plasma motions over a supergranular cell. We conclude that in this event the two filaments play an active and decisive role, albeit in different stages of the phenomenon, in fact the destabilization of one filament causes brightenings, reconnection and ribbons, while the second one, whose eruption is caused by the field reconfiguration resulting from the previous reconnection, undergoes the greatest changes and causes the CME. Title: JUpiter ICy moons Explorer (JUICE): An ESA L-Class Mission Candidate to the Jupiter System Authors: Dougherty, M.; Grasset, O.; Erd, C.; Titov, D.; Bunce, E.; Coustenis, A.; Blanc, M.; Coates, A.; Drossart, P.; Fletcher, L.; Hussmann, H.; Jaumann, R.; Krupp, N.; Prieto-Ballesteros, O.; Tortora, P.; Tosi, F.; van Hoolst, T. Bibcode: 2012LPI....43.1806D Altcode: JUICE is the next step for an in-depth exploration of the geophysical and environmental characteristics of Ganymede and exploration of Callisto and Europa, and will provide an in-depth understanding of Jupiter’s atmosphere and magnetosphere. Title: Further seasonal changes in Uranus’ cloud structure observed by Gemini-North and UKIRT Authors: Irwin, P. G. J.; Teanby, N. A.; Davis, G. R.; Fletcher, L. N.; Orton, G. S.; Calcutt, S. B.; Tice, D. S.; Hurley, J. Bibcode: 2012Icar..218...47I Altcode: Near-infrared observations of Uranus were made in October/November 2010 with the Gemini-North telescope in Hawaii, using NIFS, an integral field spectrograph, and the NIRI instrument in imaging mode. Observations were acquired using adaptive optics and have a spatial resolution of approximately 0.1-0.2″.

The observed spectra along Uranus’ central meridian were analysed using a multiple-scattering retrieval algorithm to infer the vertical/latitudinal variation in cloud optical depth, which we compare with previous observations made by Gemini-North/NIFS in 2009 and UKIRT/UIST observations made between 2006 and 2008. Assuming a continuous distribution of small particles (r ∼ 1 μm, and refractive index of 1.4 + 0i) with the single scattering albedo set to 0.75 and using a Henyey-Greenstein phase function with asymmetry parameter set to 0.7 at all wavelengths and latitudes, the retrieved cloud density profiles show that the north polar zone at 45°N has continued to steadily brighten while the south polar zone at 45°S has continued to fade. As with our previous analyses we find that, assuming that the methane vertical profile is the same at all latitudes, the clouds forming these polar zones at 45°N and 45°S lie at slightly lower pressures than the clouds at more equatorial latitudes. However, we also find that the Gemini data can be reproduced by assuming that the main cloud remains fixed at ∼2 bar at all latitudes and adjusting the relative humidity of methane instead. In this case we find that the deep cloud is still more opaque at the equator and at the zones at 45°N and 45°S and shows the same seasonal trends as when the methane humidity remain fixed. However, with this approach the relative humidity of methane is seen to rise sharply from approximately 20% at polar latitudes to values closer to 80% for latitudes equatorward of 45°S and 45°N, consistent with the analysis of 2002 HST observations by Karkoschka and Tomasko (Karkoschka, E., Tomasko, M. [2009]. Icarus 202, 287-302), with a possible indication of seasonal variability. Overall, Uranus appeared to be less convectively active in 2010 than in the previous 4 years, supporting the conclusion that now the northern spring equinox (which occurred in 2007) has passed, the atmosphere is settling back into the more quiescent state seen by Voyager 2 in 1986. Title: Sub-millimetre spectroscopy of Saturn's trace gases from Herschel/SPIRE Authors: Fletcher, L. N.; Swinyard, B.; Salji, C.; Polehampton, E.; Fulton, T.; Sidher, S.; Lellouch, E.; Moreno, R.; Orton, G.; Cavalié, T.; Courtin, R.; Rengel, M.; Sagawa, H.; Davis, G. R.; Hartogh, P.; Naylor, D.; Walker, H.; Lim, T. Bibcode: 2012A&A...539A..44F Altcode:
Aims: We provide an extensive new sub-millimetre survey of the trace gas composition of Saturn's atmosphere using the broad spectral range (15-51 cm-1) and high spectral resolution (0.048 cm-1) offered by Fourier transform spectroscopy by the Herschel/SPIRE instrument (Spectral and Photometric Imaging REceiver). Observations were acquired in June 2010, shortly after equinox, with negligible contribution from Saturn's ring emission.
Methods: Tropospheric temperatures and the vertical distributions of phosphine and ammonia are derived using an optimal estimation retrieval algorithm to reproduce the sub-millimetre data. The abundance of methane, water and upper limits on a range of different species are estimated using a line-by-line forward model.
Results: Saturn's disc-averaged temperature profile is found to be quasi-isothermal between 60 and 300 mbar, with uncertainties of 7 K due to the absolute calibration of SPIRE. Modelling of PH3 rotational lines confirms the vertical profile derived in previous studies and shows that negligible PH3 is present above the 10- to 20-mbar level. The upper tropospheric abundance of NH3 appears to follow a vapour pressure distribution throughout the region of sensitivity in the SPIRE data, but the degree of saturation is highly uncertain. The tropospheric CH4 abundance and Saturn's bulk C/H ratio are consistent with Cassini studies. We improve the upper limits on several species (H2S, HCN, HCP and HI); provide the first observational constraints on others (SO2, CS, methanol, formaldehyde, CH3Cl); and confirm previous upper limits on HF, HCl and HBr. Stratospheric emission from H2O is suggested at 36.6 and 38.8 cm-1 with a 1σ significance level, and these lines are used to derive mole fractions and column abundances consistent with ISO and SWAS estimations a decade earlier. Title: Optimal estimation retrievals of the atmospheric structure and composition of HD 189733b from secondary eclipse spectroscopy Authors: Lee, J. -M.; Fletcher, L. N.; Irwin, P. G. J. Bibcode: 2012MNRAS.420..170L Altcode: 2011arXiv1110.2934L; 2011MNRAS.tmp.1983L Recent spectroscopic observations of transiting hot Jupiters have permitted the derivation of the thermal structure and molecular abundances of H2O, CO2, CO and CH4 in these extreme atmospheres. Here, for the first time, we apply the technique of optimal estimation to determine the thermal structure and composition of an exoplanet by solving the inverse problem. The development of a suite of radiative transfer and retrieval tools for exoplanet atmospheres is described, building upon a retrieval algorithm which is extensively used in the study of our own Solar system. First, we discuss the plausibility of detection of different molecules in the dayside atmosphere of HD 189733b and the best-fitting spectrum retrieved from all publicly available sets of secondary eclipse observations between 1.45 and 24 μm. Additionally, we use contribution functions to assess the vertical sensitivity of the emission spectrum to temperatures and molecular composition. Over the altitudes probed by the contribution functions, the retrieved thermal structure shows an isothermal upper atmosphere overlying a deeper adiabatic layer (temperature decreasing with altitude), which is consistent with previously reported dynamical and observational results. The formal uncertainties on retrieved parameters are estimated conservatively using an analysis of the cross-correlation functions and the degeneracy between different atmospheric properties. The formal solution of the inverse problem suggests that the uncertainties on retrieved parameters are larger than suggested in previous studies, and that the presence of CO and CH4 is only marginally supported by the available data. Nevertheless, by including as broad a wavelength range as possible in the retrieval, we demonstrate that available spectra of HD 189733b can constrain a family of potential solutions for the atmospheric structure. Title: Retrieval of Atmosphere Structure and Composition of Exoplanets from Transit Spectroscopy Authors: Lee, Jae-Min; Fletcher, L. N.; Irwin, P. G. J. Bibcode: 2012AAS...21940502L Altcode: Recent spectroscopic observations of transiting exoplanets of HD 189733b, HD 209458b, GJ 436b and GJ 1214b provide the best chance of characterizing the thermal structure and composition of their atmospheres. Here we have applied an optimal estimation retrieval architecture to fit exoplanet spectra to determine the thermal structure and composition by solving the inverse problem. The development of a suite of radiative transfer and retrieval tools for exoplanet atmospheres is explained, building upon a rapid correlated-k approximation and a retrieval algorithm extensively used in our own solar system. With these tools we discuss the best-fitting spectrum to the measurements with the best-estimated solution (i.e. the maximum a posteriori solution) for the vertical temperature structure and molecular abundances. Additionally, the contribution functions and the vertical sensitivity to the molecules are fully utilized to interpret transmission and emission spectra, probing the structure and composition of the atmosphere. Furthermore, the analysis of the cross-correlation functions permits us to quantify the uncertainties in the degeneracy between the retrieved atmospheric properties based on the current quality of the data. This sheds light on the range of diverse interpretations offered by other studies so far. It also allows us to scrutinize further atmospheric features by maximizing the capability of the current retrieval algorithm and to demonstrate the benefit of using as broad a spectral range as possible, with clear implications for the next generation of exoplanetary missions. Title: Relationship between an M6.6 solar flare and subsequent filament activations. Authors: Rubio da Costa, F.; Zuccarello, F.; Romano, P.; Fletcher, L.; Labrosse, N. Bibcode: 2012MSAIS..19..113R Altcode: We study an event which occurred in NOAA 8471, where an M6.6 flare and the activation of two filaments were observed on 28 February 1999. A multi-wavelength study allows us to investigate the behavior of the several features observed at different atmospheric levels, that might be used to answer to the question whether and in what conditions the eruption of filaments can play an active or a passive role in the flare occurrence. Imaging data were acquired by BBSO in the Halpha line and by TRACE in the 1216, 1600, 171 and 195 Å channels, allowing us to deduce the morphology and temporal evolution of the event and to estimate the Ly-alpha power. Moreover, in order to study the magnetic topology, the extrapolation of the photospheric magnetic field lines was done assuming potential field and using SOHO/MDI magnetograms. Title: Solar flares in Halpha and Ly-alpha : observations vs simulations. Authors: Rubio da Costa, F.; Zuccarello, F.; Fletcher, L.; Labrosse, N.; Prosecký, T.; Kašparová, J. Bibcode: 2012MSAIS..19..117R Altcode: In order to study the properties of faint, moderate and bright flares, we simulate the conditions of the solar atmosphere using a radiative hydrodynamic model \citep{2005ApJ...630..573A}. A constant beam of non-thermal electrons is injected at the apex of a 1D coronal loop and heating from thermal soft X-ray and UV emission is included. We study the contribution of different processes to the total intensity of different lines at different atmospheric layers. We obtain the total integrated intensity of different lines and we compare those of the Ly-alpha and Halpha lines with the observational values for Ly-alpha (using TRACE 1216 and 1600 Å data and estimating the ``pure'' Ly-alpha emission) and Halpha (using data from the Ondřejov Observatory). We inferred from the analysis of the values obtained by simulation that the X-ray energy of the different kind of flares does not strongly affect the Ly-alpha results; the Halpha results are comparable to the observed ones, concluding that the simulated solar atmosphere fits better at lower layers of the chromosphere than at upper layers. Title: Saturn's Great White Storm (2010): Correlations between Clouds and Thermal Fields? Authors: Momary, T.; Yanamandra-Fisher, P. A.; Orton, G. S.; Baines, K. H.; Fletcher, L.; Trinh, S.; Delcroix, M. Bibcode: 2011AGUFM.P13C1683M Altcode: It is well known that convective storms occur regularly in Saturn's atmosphere, but giant storm outbreaks, known as Great White Spot (GWS) outbreaks, occur approximately every 29 years or once per Saturnian year, just past northern solstice. Including the recent GWS outbreak of December 2010, a total of six have occurred, and are considered to be related to the changing seasonal insolation, though their triggers are not yet known or what occurs below the clouds on smaller temporal and spatial timelines. Although not predictable, as evidenced by the current Northern Storm and observed by Cassini, the great storms start out with a violent outbreak, dredging up material from the deep atmosphere, which then is dispersed by the prevailing winds. The recent 2010 December GWS outbreak is an outlier, occurring at northern latitudes of approximately 35°N (the northern "Tornado Alley"), just past vernal equinox, almost a season early. It has rapidly encircled the planet in two months and is now in its mature phase, with discrete structure obvious at all longitudes at both mid-infrared and deep atmosphere (or 5-microns). Recent amateur observations indicate a link between lightning strikes, convective storm activity, GWS and spoke activity in the morning ansa (Delacroix et al., 2011). We shall explore correlations between the many visible/CCD observations from the amateur community, the albedo and thermal maps produced with data acquired from NASA/InfraRed Telescope Facility (IRTF)/NSFCAM2, a 1 - 5-micron imager, during the various phases of the 2010 - 2011 GWS. We will characterize changes in the local environs of the outbreak site at various epochs and compare with other locations on the planet. Delacroix, M., E. Kraaikamp and P. Yanamandra-Fisher,2011. First Ground Observations of Saturn's Spokes Around 2009 Equinox. EPSC/DPS, Nantes, France. Title: A Sensitive Search for Traces of Stratospheric NH3, PH3, C2H5D, and CH2C2H2 within Saturn's Beacon Authors: Greathouse, T. K.; Irons, W.; Fouchet, T.; Fletcher, L.; Orton, G. S.; Bézard, B.; Tokunaga, A. T.; Lacy, J. H. Bibcode: 2011AGUFM.P13C1682G Altcode: The development of a hot region in Saturn's stratosphere, the Beacon, coincided with observations of a massive storm outbreak in Saturn's deeper atmosphere. It is thought that these disturbances in the troposphere and stratosphere are related. The severity and size of the deep convective storm along with the increased stratospheric temperatures of the Beacon suggested the possibility that the tropospheric convection was strong enough to inject chemical constituents from the troposphere into the stratosphere by convective overshoot. Using the high spectral resolution capabilities of TEXES, the Texas Echelon cross Echelle Spectrograph, mounted on the NASA Infrared Telescope Facility, IRTF, we performed a sensitive search for NH3 and PH3 emission lines that would indicate the presence of NH3 and PH3 in the stratospheric region of the Beacon. We will present upper limits to the NH3 and PH3 abundances as initial reductions of the data retrieved between July 14th and 19th, 2011 showed no obvious emission features from either gas. The high temperatures within the Beacon also allowed for a detailed search for molecules as yet undetected in the stratospheres of the Outer Planets, but predicted to exist at low abundance levels. Observations centered at 800 cm-1 and 845 cm-1 were retrieved to search for C2H5D and CH2C2H2 emission, respectively. Like the search for NH3 and PH3, initial reductions show no trace of these molecules. We will present a more thorough analysis with an upper limit to the CH2C2H2 abundance within the Beacon. Only a model to data comparison will be made for the C2H5D spectral setting, since a full set of line parameters for this molecule have yet to be recorded. Title: High Energy Solar Physics Data in Europe (HESPE): a European project for the exploitation of hard X-ray data in solar flare physics Authors: Piana, M.; Csillaghy, A.; Kontar, E. P.; Fletcher, L.; Veronig, A. M.; Vilmer, N.; Hurford, G. J.; Dennis, B. R.; Schwartz, R. A.; Massone, A.; Krucker, S.; Benvenuto, F.; Etesi, L. I.; Guo, J.; Hochmuth, N.; Reid, H. Bibcode: 2011AGUFMSH33B2068P Altcode: It has been recognized since the early days of the space program that high-energy observations play a crucial role in understanding the basic mechanisms of solar eruptions. Unfortunately, the peculiar nature of this radiation makes it so difficult to extract useful information from it that non-conventional observational techniques together with complex data analysis procedures must be adopted. HESPE is a European project funded within the seventh Framework Program, with the aim of realizing computational methods for solar high-energy data analysis and technological tools for the intelligent exploitation of science-ready products. Such products and methods are put at disposal of the solar, heliospheric and space weather communities, who will exploit them in order to build flare prediction models and to integrate the information extracted from hard X-rays and gamma rays data, with the one extracted from other wavelengths data. Title: Non-Observation of the He II 304 A Charge-Exchange Continuum in Major Solar Flares Authors: Hudson, H. S.; Fletcher, L.; MacKinnon, A.; Woods, T. N. Bibcode: 2011AGUFMSH41A1909H Altcode: We report on a search for flare emission via charge-exchange continuum radiation in the wings of the Lyman-alpha line of He ii at 304 A, as originally suggested for hydrogen by Orrall and Zirker (1976). Via this mechanism a primary alpha particle that penetrates into the neutral chromosphere can pick up an atomic electron and radiate recombination continuum before it stops. The Extreme-ultraviolet Variability Experiment (EVE) on board the Solar Dynamics Observatory (SDO) gives us our first chance to search for this effect systematically. The Orrall-Zirker charge-exchange mechanism has great importance for flare physics because of the essential roles that particle acceleration plays; this mechanism is one of the few proposed that would allow remote sensing of primary accelerated particles below a few MeV/nucleon. We study four EVE events: the gamma-ray events SOL2010-06-12 (M2.0) and SOL20 11-02-24 (M3.5), the latter a limb flare, and the X-class flares SOL2010-02-15 (X2.2) and SOL2011-03-09 (X1.2). No clear signature of the charge-exchange continuum appears, but SOL2010-02-15 (X2.2) does reveal a gradual broad-band signature that we tentatively interpret as due to unresolved emission lines or instrumental scattering. Title: Splinter Session "Solar and Stellar Flares" Authors: Fletcher, L.; Hudson, H.; Cauzzi, G.; Getman, K. V.; Giampapa, M.; Hawley, S. L.; Heinzel, P.; Johnstone, C.; Kowalski, A. F.; Osten, R. A.; Pye, J. Bibcode: 2011ASPC..448..441F Altcode: 2011csss...16..441F; 2012arXiv1206.3997F This summary reports on papers presented at the Cool Stars-16 meeting in the splinter session "Solar and Stellar flares." Although many topics were discussed, the main themes were the commonality of interests, and of physics, between the solar and stellar flare communities, and the opportunities for important new observations in the near future. Title: Investigation of the Photochemistry in Saturn's Ring Shadowed Atmosphere: Production Rates of Key Atmospheric Molecules Authors: Edgington, S. G.; Atreya, S. K.; Wilson, E. H.; Baines, K. H.; West, R. A.; Bjoraker, G. L.; Fletcher, L. Bibcode: 2011AGUFM.P13C1685E Altcode: Cassini has been orbiting Saturn for well over seven years. During this epoch, the ring shadow has changed from shading a large portion of the northern hemisphere to shading a small region just south of the equator and is continuing southward. At Saturn Orbit Insertion (July 1, 2004), the ring plane was inclined by ~24 degrees relative to the Sun-Saturn vector. The projection of the B-ring onto Saturn reached as far as 40N along the central meridian (~52N at the terminator). At its maximum extent, the ring shadow can reach as far as 48N (~58N at the terminator). The net result, is that the intensity of both ultraviolet and visible sunlight penetrating into any particular northern/southern latitude will vary depending on Saturn's tilt relative to the Sun and the optical thickness of each ring system. Previous work [1] looked at the variation of the solar flux as a function of solar inclination, i.e. season (see Figure 1). The current work looks at the impact of the oscillating ring shadow on the photodissociation and production rates of key molecules in Saturn's stratosphere and upper troposphere over time. Beginning with methane, the impact on production and loss rates of the long-lived photochemical hydrocarbons leading to haze formation are examined at several latitudes over a Saturn year. We also look at the impacts on phosphine abundance, a disequilibrium species whose presence in the upper troposphere is a tracer of convection processes in the deep atmosphere. Comparison to the corresponding photodissociation rates for a clear atmosphere and the effect of dynamical mixing will be presented. [1] Edgington,S.G., et al., 2006. Adaptation of a 2-D Photochemical Model to Improve Our Understanding of Saturn's Atmosphere. B.A.A.S., 38, 499 (#11.23). The research described in this paper was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Title: The Evolution of Trace Species and Temperature in Saturn's Northern Storm Region Authors: Hesman, B. E.; Fletcher, L.; Bjoraker, G. L.; Sada, P. V.; Achterberg, R. K.; Jennings, D. E.; Lunsford, A. W.; Boyle, R. J.; Kerr, T.; Romani, P. N.; Simon-Miller, A. A.; Nixon, C. A.; Davis, G. R.; Irwin, P. G. Bibcode: 2011AGUFM.P11H..04H Altcode: The massive eruption at 40°N (planetographic latitude) in December 2010 has produced significant and long-lived changes in temperature and species abundances in Saturn's northern hemisphere (Fletcher et al., 2011). The northern storm region has been observed on many occasions in between January and August of 2011 by Cassini's Composite Infrared Spectrometer (CIRS). In this time period, temperatures in regions referred to as "beacons" (warm regions in the stratosphere at certain longitudes in the storm latitude) became significantly warmer than pre-storm values of 140K. These temperatures reached a peak of 220K near the 2-mbar region in May 2011 following the merger of two beacons. These are the highest temperatures ever observed at this altitude on Saturn. The temperatures in the storm region vary longitudinally by ~70K which is the largest variation in temperature ever seen on Saturn. These warm temperatures resulted in the detection of ethylene (C2H4) using CIRS. Early analysis of the May data indicates ethylene volume mixing ratios of 3x10-8 at 2 mbar. These beacon regions have also led to the identification of rare species such as diacetylene (C4H2), methylacetylene (CH3C2H), and carbon dioxide (CO2) in the stratosphere. These species were previously measured by the Infrared Space Observatory (de Graauw et al., 1997) and CIRS (Guerlet et al., 2010). However, mapping these species in longitude and latitude over the storm region using CIRS provides insight into the changes in the photochemistry induced by the storm. Ground-based observations were performed using the high-resolution spectrometer Celeste in May and July to confirm the CIRS detection of ethylene and to study its spectral signatures at higher spectral resolution than available with CIRS, and investigate the evolution of its abundance profile as the storm progresses. The time evolution of ethylene abundance in Saturn's northern storm region using CIRS and ground-based data from the McMath-Pierce Telescope (May 2011) and the United Kingdom Infrared Telescope (July 2011) will be presented. In addition, the abundance profiles, as measured by CIRS, of C4H2, CH3C2H, and CO2 will also be discussed including how their abundance profiles have changed throughout the storm period. Title: TEXES observations of Saturn's stratospheric thermal structure after the 2010 convective event Authors: Fouchet, T.; Greathouse, T. K.; Fletcher, L. N.; Richter, M. J.; Lacy, J. H.; Irons, W.; Guerlet, S.; Bézard, B.; Lellouch, E.; Hesman, B. E.; Achterberg, R. K.; Tokunaga, A. T. Bibcode: 2011AGUFM.P13C1681F Altcode: In December 2010, a huge convective event distorted the cloud layer at 40 N in Saturn's springtime hemisphere. These large convective events are observed regularly in Saturn's atmosphere, about one event per saturnian year, and may play a central role in the transport of the internal heat flux to the radiative layer. However, this event occured at a season (Ls=16) different from that of the previous events (Ls= 110-170). Another unexpected aspect of the 2010 event was its stratospheric signature. As shown by Fletcher et al. (2011) from Cassini/CIRS and VLT/VISIR, in the 40N latitude band, the 1-mbar pressure level warmed by several tens of K at some longitudes and cooled by several K at other longitudes. In order to assess the vertical thermal structure in the disturbed latitudinal band, we performed five half-nights of observations with TEXES mounted on the NASA Infrared Telescope Facility (IRTF) from July 14th, 2011 to July 19th, 2011. The high spectral resolution (R=100,000) provided by TEXES allowed us to resolve several lines of methane in the range 1245-1250 cm-1, and the H2 S(1) quadrupole line and collision-induced continuum to measure the temperature structure between 100~mbar and 0.01~mbar. We will present the results of the observations in terms of stratospheric temperature structure. Title: Cassini/CIRS Observations of Temperatures in Saturn's Northern Storm Region Authors: Achterberg, R. K.; Hesman, B. E.; Bjoraker, G. L.; Fletcher, L.; Conrath, B. J.; Gierasch, P. J.; Flasar, F. M. Bibcode: 2011AGUFM.P13C1680A Altcode: In early December 2010, a large convective storm appeared in Saturn's northern hemisphere, centered near 40°N planetographic at the center of a westward jet (Sanchez-Lavega et al., 2011; Fisher et al. 2011). Storms of the observed magnitude, referred to as Great White Spots (GWS), are rare on Saturn, historically occurring once per Saturn year (30 Earth years), at equatorial or mid-northern latitudes during northern summer; the current storm is unusual in occurring during northern spring, roughly one season earlier than previous GWS outbursts. Thermal infrared observations, both groundbased and from the Cassini Composite Infrared Spectrometer (CIRS) orbiting Saturn, taken six weeks after the appearance of the storm, revealed significant changes to the thermal structure of Saturn's northern hemisphere (Fletcher et al., 2011). Cold temperatures were measured at the location of the disturbance in both the upper troposphere and stratosphere, and, surprisingly, hot spots to the east and west of the disturbance longitude with temperature contrasts of 16K, much larger than usual zonal temperature contrasts on Saturn. CIRS has continued to observe the latitude of the storm at one to two month intervals. These observations typically cover an approximately 10° wide latitude strip over one or two rotations of Saturn at a spatial resolution of 2° of arc in the CIRS mid-IR focal planes (600-1400 cm-1, 7-16μm). From these observations, we can retrieve temperatures in the upper troposphere between 50 and 200 mbar, and in the middle stratosphere between ~0.2 and 10 mbar. These observations show that temperatures in the stratospheric hot spots continued to increase through May 2011, when temperatures reached a peak of over 220 K, following the merger of two hot spots into one, with zonal temperature contrasts of 70 K. By mid-July, the maximum temperature in the hot spot had decreased to just under 200K. Furthermore, in May and July, the peak temperatures were at a pressure roughly two scale heights larger (lower in altitude) than in earlier observations - 2 mbar compared to 0.4 mbar. In the upper troposphere, temperature perturbations associated with the storm are around 5 to 10 K, larger than seen on Saturn prior to the storm, but much smaller than the temperature variations seen in the stratosphere. Title: Thermal Evolution of Saturn's 2010-2011 Disturbance Authors: Orton, G. S.; Fletcher, L.; Yanamandra-Fisher, P.; Mason, C.; Greco, J.; Valkov, S.; Baines, K. H.; Nanu, R.; Villar, G.; Trinh, S.; Pacheco, J.; Sola, M.; Momary, T.; Greathouse, T. K.; Fouchet, T. Bibcode: 2011AGUFM.P13C1679O Altcode: The remarkable disturbance that began in Saturn's northern hemisphere late in 2010 was initiated by a single discrete outburst of bright white cloud material, which spread with the prevailing zonal winds to completely encircle the planet within a matter of weeks. We report here the results of studies of the influence of the storm on thermal emission. These were obtained from thermal imaging observations between 5 and 25 μm, combining high-resolution imaging from ESO's Very Large Telescope (VLT) using the VISIR instrument and more frequent imaging from NASA's Infrared Telescope Facility (IRTF) using the MIRSI and NSFCam2 instruments. These observations were used to document the evolution of the spatial distributions of temperatures, gas composition and cloud opacity to trace the atmospheric circulation associated with the storm, which is consistent with a single convective plume in the deep clouds, sheared by the zonal winds and triggering widespread planetary wave activity. The disturbance generated the largest stratospheric thermal anomalies ever detected on Saturn (infrared 'beacons' that dominate the planetary emission), revealing dynamical coupling over hundreds of kilometers from the troposphere to the stratosphere. Observations made between January and March of 2011 revealed the presence of two stratospheric 'beacons' and only tropospheric cooling associated with the upwelling regions of the disturbance. Observations in April and thereafter showed that these 'beacons' had merged into a single feature, and that temperatures in the upper troposphere were increasing with time around the disturbance. Coincident with the disturbance, there appeared a major increase in the amplitude of zonal thermal waves in the northern hemisphere at longitudes distant from the disturbance. We note that the amplitude of zonal thermal waves in the southern hemisphere also increased. We will continue to track the evolution of this phenomenon, providing support for ground-based and Cassini spectroscopic observations. Title: The Evolution of Saturn's Northern Storm of 2010-2011 and Environs as Viewed by Cassini/VIMS Authors: Baines, K. H.; Momary, T.; Fletcher, L.; Showman, A. P.; Delitsky, M.; Brown, R. H.; Buratti, B. J.; Clark, R. N.; Nicholson, P. D.; Sotin, C. Bibcode: 2011AGUFM.P11H..06B Altcode: Images and spectra acquired by the Visual Infrared Mapping Spectrometer on board the Cassini Orbiter reveal that the current northern storm on Saturn is remarkable for (1) its location - the first significant storm seen in northern mid-latitudes since 1906, (2) its duration - presently approaching 8 months, and (3) its power, as indicated by the relatively massive ammonia-laden clouds it produces that reveal significant, persistent transport of materials over at least one bar of depth (> 30 km of altitude). Situated near 35 degrees north latitude (planetocentric) near the maximum of a westward jet, the storm head moves westward at ~ 2.7 degrees per day, or ~ 27 m/s. Multi-spectral images of the feature and its environs in 352 colors spanning nearly all longitudes were acquired by VIMS on February 24, May 11 and July 12, 2011. In all imagery, the head of the storm appears atypically dark in ammonia-ice sensitive wavelengths 2.73-3.1 micron, indicating significant amounts of ammonia ice. Simultaneously, the feature appears bright at pseudo-continuum near-infrared wavelengths, particularly at 4.08 micron, indicating an atypically massive cloud of large particles. Some 3-5 degree of latitude to the north and south of the cloudhead, streamers of such large-particle ammonia clouds extend more than 150 degrees of longitude to the east. While these streamers appear nearly equivalent in brightness in diagnostic wavelengths in the February 24, 2011 observations, the northern streamer clearly dominates in the May 11, 2011 map. As well, a new dark spot, the first observed associated with this storm, appears more than 250 degrees of longitude downstream of the cloudhead in the May 11, 2011 images and persists through the July 12, 2011 observations. Its appearance may be associated with the dissipation of overlying cloud features as the dark spot wandered eastward, Similar in size (> 3000 km) and spectral appearance to the dark spots associated with the 2008 southern storm (Baines et al, Planetary and Space Sci., 57, 1650-1658,2009), this feature suggests upwelling of materials from the ~10-bar level, as previously proposed for the southern storm. New imagery expected in August 2011 as well as additional analysis of the July, 2011 images will be discussed and dynamical implications presented, including possible relationships of the northern storm with the String of Pearls feature observed for 5 years in the same latitude and longitude range but which has not been observed since the advent of the storm in December 2010. Title: Multispectral imaging observations of Neptune's cloud structure with Gemini-North Authors: Irwin, P. G. J.; Teanby, N. A.; Davis, G. R.; Fletcher, L. N.; Orton, G. S.; Tice, D.; Hurley, J.; Calcutt, S. B. Bibcode: 2011Icar..216..141I Altcode: Observations of Neptune were made in September 2009 with the Gemini-North Telescope in Hawaii, using the NIFS instrument in the H-band covering the wavelength range 1.477-1.803 μm. Observations were acquired in adaptive optics mode and have a spatial resolution of approximately 0.15-0.25″. The observations were analysed with a multiple-scattering retrieval algorithm to determine the opacity of clouds at different levels in Neptune's atmosphere. We find that the observed spectra at all locations are very well fit with a model that has two thin cloud layers, one at a pressure level of ∼2 bar all over the planet and an upper cloud whose pressure level varies from 0.02 to 0.08 bar in the bright mid-latitude region at 20-40°S to as deep as 0.2 bar near the equator. The opacity of the upper cloud is found to vary greatly with position, but the opacity of the lower cloud deck appears remarkably uniform, except for localised bright spots near 60°S and a possible slight clearing near the equator. A limb-darkening analysis of the observations suggests that the single-scattering albedo of the upper cloud particles varies from ∼0.4 in regions of low overall albedo to close to 1.0 in bright regions, while the lower cloud is consistent with particles that have a single-scattering albedo of ∼0.75 at this wavelength, similar to the value determined for the main cloud deck in Uranus' atmosphere. The Henyey-Greenstein scattering particle asymmetry of particles in the upper cloud deck are found to be in the range g ∼ 0.6-0.7 (i.e. reasonably strongly forward scattering). Numerous bright clouds are seen near Neptune's south pole at a range of pressure levels and at latitudes between 60 and 70°S. Discrete clouds were seen at the pressure level of the main cloud deck (∼2 bar) at 60°S on three of the six nights observed. Assuming they are the same feature we estimate the rotation rate at this latitude and pressure to be 13.2 ± 0.1 h. However, the observations are not entirely consistent with a single non-evolving cloud feature, which suggests that the cloud opacity or albedo may vary very rapidly at this level at a rate not seen in any other giant-planet atmosphere. Title: Thermal Evolution of Saturn's Springtime Disturbance Authors: Fletcher, L. N.; Orton, G. S.; Irwin, P. G. J.; Sanchez-Lavega, A.; Baines, K. H.; Hesman, B. E.; Read, P. L.; Flasar, F. M.; Momary, T. W.; Simon-Miller, A. A.; Hueso, R.; Bjoraker, G. L.; Yanamandra-Fisher, P. Bibcode: 2011epsc.conf..713F Altcode: 2011DPS....43..713F Saturn's slow seasonal warming was spectacularly disrupted in December 2010 by the eruption of an enormous storm system in its springtime hemisphere. This storm, which is still evolving at the time of writing, is only the sixth known example of a planetwide storm system on Saturn, and the first to occur at this latitude (near 40oN) in over a century [1,2]. A combined analysis of thermal infrared imaging from ESO's Very Large Telescope VISIR instrument and 5-200 μm spectroscopy from instruments onboard Cassini revealed the substantial atmospheric perturbations related to the storm complex over a wide range of altitudes [1]. Since that time the storm complex has continued to evolve through the mature phase. In particular Saturn's newly-identified stratospheric beacons (a high-altitude response to mechanical forcing from the troposphere) have been observed to move in the stratospheric wind field, merge and strengthen to generate thermal differences considerably larger than those reported in our initial study (Fig. 1, from IRTF/MIRSI, May 22 2011). Title: The December 2010 outbreak of a major storm in Saturn's atmosphere: Observations and models Authors: Sanchez-Lavega, A.; Del Río-Gaztelurrutia, T.; Hueso, R.; Gómez-Forrellad, J. M.; Sanz-Requena, J. F.; Legarreta, J.; García-Melendo, E.; Colas, F.; Lecacheux, J.; Fletcher, L. N.; Barrado-Navascués, D.; Parker, D. Bibcode: 2011epsc.conf..400S Altcode: 2011DPS....43..400S On December 5, 2010, a major storm erupted in Saturn's northern hemisphere at a planetographic latitude of 37.7 deg [1]. These phenomena are known as "Great White Spots" (GWS) and they have been observed once per Saturn year since the first case confidently reported in 1876. The last event occurred at Saturn's Equator in 1990 [2]. A GWS differs from similar smaller-scale storms in that it generates a planetary-scale disturbance that spreads zonally spanning the whole latitude band. Studies of the 1990 case indicated that the storm produced a long-term substantial change in the cloud and haze structure around the tropopause level, and in the equatorial winds. We report on the evolution and motions of the new GWS and its associated disturbance during the months following the outbreak, based mainly on high quality images obtained in the visual range submitted to the International Outer Planet Watch PVOL database [3], with the 1m telescope at Pic-du-Midi Observatory and 2.2 m telescope at Calar Alto Observatory. The high temporal sampling and coverage allowed us to study the dynamics of the GWS in detail and the multi-wavelength observations provide information on its cloud top structure. We present non-linear simulations using the EPIC code of the evolution of the potential vorticity generated by an impulsive and localized Gaussian heat pulse that compare extraordinary well to the observed cloud field evolution. Title: Uranus' cloud structure and scattering particle properties from IRTF SpeX observations Authors: Tice, D. S.; Irwin, P. G. J.; Fletcher, L. N.; Teanby, N. A.; Orton, G. S.; Davis, G. R. Bibcode: 2011epsc.conf..143T Altcode: 2011DPS....43..143T Observations of Uranus were made in August 2009 with the SpeX spectrograph at the NASA Infrared Telescope Facility (IRTF). Analysed spectra range from 0.8 to 1.8 μm at a spatial resolution of 0.5" and a spectral resolution of R = 1,200. Spectra from 0.818 to 0.834 μm, a region characterised by both strong hydrogen quadrupole and methane absorptions are considered to determine methane content. Evidence indicates that methane abundance varies with latitude. NEMESIS, an optimal estimation retrieval code with full-scattering capability, is employed to analyse the full range of data. Cloud and haze properties in the upper troposphere and stratosphere are characterised, and are consistent with other current literature. New information on single scattering albedos and particle size distributions are inferred. Title: The EVE Doppler Sensitivity and Flare Observations Authors: Hudson, H. S.; Woods, T. N.; Chamberlin, P. C.; Fletcher, L.; Del Zanna, G.; Didkovsky, L.; Labrosse, N.; Graham, D. Bibcode: 2011SoPh..273...69H Altcode: 2011SoPh..tmp..362H The Extreme-ultraviolet Variability Experiment (EVE; see Woods et al., 2009) obtains continuous EUV spectra of the Sun viewed as a star. Its primary objective is the characterization of solar spectral irradiance, but its sensitivity and stability make it extremely interesting for observations of variability on time scales down to the limit imposed by its basic 10 s sample interval. In this paper we characterize the Doppler sensitivity of the EVE data. We find that the 30.4 nm line of He II has a random Doppler error below 0.001 nm (1 pm, better than 10 km s−1 as a redshift), with ample stability to detect the orbital motion of its satellite, the Solar Dynamics Observatory (SDO). Solar flares also displace the spectrum, both because of Doppler shifts and because of EVE's optical layout, which (as with a slitless spectrograph) confuses position and wavelength. As a flare develops, the centroid of the line displays variations that reflect Doppler shifts and therefore flare dynamics. For the impulsive phase of the flare SOL2010-06-12, we find the line centroid to have a redshift of 16.8 ± 5.9 km s−1 relative to that of the flare gradual phase (statistical errors only). We find also that high-temperature lines, such as Fe XXIV 19.2 nm, have well-determined Doppler components for major flares, with decreasing apparent blueshifts as expected from chromospheric evaporation flows. Title: Elusive Ethylene Detected in Saturn's Northern Storm Region Authors: Hesman, B. E.; Bjoraker, G. L.; Sada, P. V.; Achterberg, R. K.; Jennings, D. E.; Lunsford, A. W.; Boyle, R. J.; Romani, P. N.; Simon-Miller, A. A.; Nixon, C. A.; Fletcher, L. N.; Irwin, P. G. J. Bibcode: 2011epsc.conf.1222H Altcode: 2011DPS....43.1222H The massive eruption at 40°N (planetographic latitude) in December 2010 has produced significant and lasting effects in the northern hemisphere on temperature and species abundances [1]. The northern storm region has been observed on many occasions in between January and May of 2011 by Cassini's Composite Infrared Spectrometer (CIRS). In May 2011 temperatures in the stratosphere greater than 220K were derived from CIRS spectra in the regions referred to as "beacons" (warm regions in the stratosphere). Ethylene (C2H4) has been detected in a beacon in Saturn's northern storm region using CIRS. Ground-based observations using the high-resolution spectrometer Celeste on the McMath-Pierce Telescope on May 15, 2011 were used to confirm the detection. Early analysis indicate ethylene volume mixing ratios of 3x10-8 at 2 mbar. Title: JUICE (JUpiter ICy moon Explorer): a European-led mission to the Jupiter system Authors: Dougherty, M. K.; Grasset, O.; Bunce, E.; Coustenis, A.; Titov, D. V.; Erd, C.; Blanc, M.; Coates, A. J.; Coradini, A.; Drossart, P.; Fletcher, L.; Hussmann, H.; Jaumann, R.; Krupp, N.; Prieto-Ballesteros, O.; Tortora, P.; Tosi, F.; van Hoolst, T.; Lebreton, J. -P. Bibcode: 2011epsc.conf.1343D Altcode: 2011DPS....43.1343D The former ESA-NASA EJSM-Laplace mission is being reformulated by ESA as a European-led single spacecraft mission to the Jovian system. The concept has been recently renamed JUICE (JUpiter ICy moon Explorer). The new mission is based on the design of the Jupiter Ganymede Orbiter (JGO) - the ESA flight element of EJSM-Laplace. Title: Seasonal Variations of Hydrocarbons in Saturn's Stratosphere Authors: Sinclair, J. A.; Irwin, P. G. J.; Fletcher, L. N.; Hurley, J.; Merlet, C. Bibcode: 2011epsc.conf..511S Altcode: 2011DPS....43..511S We present a study of the seasonal variations of hydrocarbons in the stratosphere of Saturn. Meridional variations of the abundances of hydrocarbons such as acetylene (C2H2) and ethane (C2H6) have previously been determined, in particular using observations from the Cassini/CIRS (Composite Infrared Spectrometer) instrument. Such studies have used Cassini data obtained during the prime mission (2004 - 2008) therefore studying Saturn from shortly after summer solstice to 'autumn' in the Southern Hemisphere. With the occurence of the vernal equinox in August 2009, Saturn's northern hemisphere is now approaching summer solstice. We aim to determine the response of the hydrocarbon photochemistry as a result of seasonal changes. Title: Saturn's Enigmatic "String of Pearls" and Northern Storm of 2010-2011: Manifestations of a Common Dynamical Mechanism? Authors: Baines, K.; Momary, T.; Fletcher, L.; Showman, A.; Brown, R.; Buratti, B.; Clark, R.; Nicholson, P.; Go, C.; Wesley, A. Bibcode: 2011epsc.conf.1658B Altcode: 2011DPS....43.1658B The "String of Pearls" (SoP) and the Northern Storm on Saturn near 34o north latitude may both be manifestations of convective processes at depth. As one possibility, the SoP may be a set of von Kármán vortex street features with convectively-driven updrafts as the driving obstacles. VIMS observations show marked increases in the size and latitudinal separation of the pearls (vortices) during the year prior to storm eruption, indicative of a growing convective system that may have subsequently erupted as a major thunderstorm. Other common convective mechanisms (uplift-driven Rossby waves, vortex-shedding from rising updrafts) may be possible. New VIMS images and spectra of the thunderstorm and SoP are presented. Title: The 2010-2011 Revival of Jupiter's South Equatorial Belt: Perturbations of Temperatures, Clouds and Composition from Infrared Observations Authors: Orton, G.; Fletcher, L.; Yanamandra-Fisher, P.; Sanchez-Lavega, A.; Perez-Hoyos, S.; de Pater, I.; Wong, M.; Goetz, R.; Valkov, S.; Greco, J.; Edwards, M.; Rogers, J.; Baines, K. Bibcode: 2011epsc.conf..673O Altcode: 2011DPS....43..673O On 2010 November 9, a perturbation appeared in Jupiter's South Equatorial Belt (SEB), which began a classical "revival" of the SEB, returning the entire axisymmetric region to its normal dark color from its anomalous, light, "faded" state. The early revival is marked by strong upwelling gas at the outbreak location, to the west of which appear alternating clear and cloudy regions. Clear regions are correlated with dark clouds near the outbreak and in a southern retrograding branch but less so in a northern prograding branch. A 5-μm image from 2010 March 1 shows much of the SEB closer to a pre-faded state. Title: Investigation of the Photochemistry in Saturn's Ring Shadowed Atmosphere: Production Rates of Key Atmospheric Molecules Authors: Edgington, S. G.; Atreya, S. K.; Wilson, E. H.; Baines, K. H.; West, R. A.; Bjoraker, G. L.; Fletcher, L. N. Bibcode: 2011epsc.conf.1710E Altcode: 2011DPS....43.1710E Cassini has been orbiting Saturn for well over six years. During this epoch, the ring shadow has moved from covering a relatively large portion of the northern hemisphere to covering a small region just south of the equator (see Figure 1). For example, at Saturn Orbit Insertion (SOI; July 1, 2004), the ring plane was inclined by ~24 degrees relative to the Sun-Saturn vector. At this time, the projection of the B-ring onto Saturn reached as far as 40ºN along the central meridian (~52ºN at the terminator). At its maximum extent, the ring shadow can reach as far as 48ºN (~58ºN at the terminator). The net result, is that the intensity of both ultraviolet and visible sunlight penetrating into any particular northern/southern latitude will vary depending on Saturn's tilt relative to the Sun and the optical thickness of each ring system (see Figure 2). Previous work [1] looked at the variation of the solar flux as a function of solar inclination, i.e. season (see Figure 3). The current work looks at the impact of the oscillating ring shadow on the photodissociation and production rates of key molecules in Saturn's stratosphere and upper troposphere over time. Beginning with methane, the impact on production and loss rates of the long-lived photochemical products leading to haze formation are examined at several latitudes over a Saturn year. We also look at the impacts on phosphine abundance, a disequilibrium species whose presence in the upper troposphere is a tracer of convection processes in the deep atmosphere. Comparison to the corresponding rates for the clear atmosphere and the effect of dynamical mixing will be presented. Title: An Observational Overview of Solar Flares Authors: Fletcher, L.; Dennis, B. R.; Hudson, H. S.; Krucker, S.; Phillips, K.; Veronig, A.; Battaglia, M.; Bone, L.; Caspi, A.; Chen, Q.; Gallagher, P.; Grigis, P. T.; Ji, H.; Liu, W.; Milligan, R. O.; Temmer, M. Bibcode: 2011SSRv..159...19F Altcode: 2011SSRv..tmp..261F; 2011arXiv1109.5932F We present an overview of solar flares and associated phenomena, drawing upon a wide range of observational data primarily from the RHESSI era. Following an introductory discussion and overview of the status of observational capabilities, the article is split into topical sections which deal with different areas of flare phenomena (footpoints and ribbons, coronal sources, relationship to coronal mass ejections) and their interconnections. We also discuss flare soft X-ray spectroscopy and the energetics of the process. The emphasis is to describe the observations from multiple points of view, while bearing in mind the models that link them to each other and to theory. The present theoretical and observational understanding of solar flares is far from complete, so we conclude with a brief discussion of models, and a list of missing but important observations. Title: Evolution of sunspot properties during solar cycle 23 Authors: Watson, F. T.; Fletcher, L.; Marshall, S. Bibcode: 2011A&A...533A..14W Altcode: 2011arXiv1108.4285W Context. The long term study of the Sun is necessary if we are to determine the evolution of sunspot properties and thereby inform modeling of the solar dynamo, particularly on scales of a solar cycle.
Aims: We aim to determine a number of sunspot properties over cycle 23 using the uniform database provided by the SOHO Michelson Doppler Imager data. We focus in particular on their distribution on the solar disk, maximum magnetic field and umbral/penumbral areas. We investigate whether the secular decrease in sunspot maximum magnetic field reported in Kitt Peak data is present also in MDI data.
Methods: We have used the Sunspot Tracking And Recognition Algorithm (STARA) to detect all sunspots present in the SOHO Michelson Doppler Imager continuum data giving us 30 084 separate detections. We record information on the sunspot locations, area and magnetic field properties as well as corresponding information for the umbral areas detected within the sunspots, and track them through their evolution.
Results: We find that the total visible umbral area is 20-40% of the total visible sunspot area regardless of the stage of the solar cycle. We also find that the number of sunspots observed follows the Solar Influences Data Centre international sunspot number with some interesting deviations. Finally, we use the magnetic information in our catalogue to study the long term variation of magnetic field strength within sunspot umbrae and find that it increases and decreases along with the sunspot number. However, if we were to assume a secular decrease as was reported in the Kitt Peak data and take into account sunspots throughout the whole solar cycle we would find the maximum umbral magnetic fields to be decreasing by 23.6 ± 3.9 Gauss per year, which is far less than has previously been observed by other studies (although measurements are only available for solar cycle 23). If we only look at the declining phase of cycle 23 we find the decrease in sunspot magnetic fields to be 70 Gauss per year. Title: Recent Advances in Understanding Particle Acceleration Processes in Solar Flares Authors: Zharkova, V. V.; Arzner, K.; Benz, A. O.; Browning, P.; Dauphin, C.; Emslie, A. G.; Fletcher, L.; Kontar, E. P.; Mann, G.; Onofri, M.; Petrosian, V.; Turkmani, R.; Vilmer, N.; Vlahos, L. Bibcode: 2011SSRv..159..357Z Altcode: 2011SSRv..tmp..156Z; 2011SSRv..tmp..249Z; 2011SSRv..tmp..232Z; 2011arXiv1110.2359Z; 2011SSRv..tmp..278Z We review basic theoretical concepts in particle acceleration, with particular emphasis on processes likely to occur in regions of magnetic reconnection. Several new developments are discussed, including detailed studies of reconnection in three-dimensional magnetic field configurations (e.g., current sheets, collapsing traps, separatrix regions) and stochastic acceleration in a turbulent environment. Fluid, test-particle, and particle-in-cell approaches are used and results compared. While these studies show considerable promise in accounting for the various observational manifestations of solar flares, they are limited by a number of factors, mostly relating to available computational power. Not the least of these issues is the need to explicitly incorporate the electrodynamic feedback of the accelerated particles themselves on the environment in which they are accelerated. A brief prognosis for future advancement is offered. Title: Long-term evolution of the aerosol debris cloud produced by the 2009 impact on Jupiter Authors: Sánchez-Lavega, A.; Orton, G. S.; Hueso, R.; Pérez-Hoyos, S.; Fletcher, L. N.; García-Melendo, E.; Gomez-Forrellad, J. M.; de Pater, I.; Wong, M.; Hammel, H. B.; Yanamandra-Fisher, P.; Simon-Miller, A.; Barrado-Izagirre, N.; Marchis, F.; Mousis, O.; Ortiz, J. L.; García-Rojas, J.; Cecconi, M.; Clarke, J. T.; Noll, K.; Pedraz, S.; Wesley, A.; Kalas, P.; McConnell, N.; Golisch, W.; Griep, D.; Sears, P.; Volquardsen, E.; Reddy, V.; Shara, M.; Binzel, R.; Grundy, W.; Emery, J.; Rivkin, A.; Thomas, C.; Trilling, D.; Bjorkman, K.; Burgasser, A. J.; Campins, H.; Sato, T. M.; Kasaba, Y.; Ziffer, J.; Mirzoyan, R.; Fitzgerald, M.; Bouy, H.; International Outer Planet Watch Team (IOPW-PVOL) Bibcode: 2011Icar..214..462S Altcode: 2011Icar..214..462I We present a study of the long-term evolution of the cloud of aerosols produced in the atmosphere of Jupiter by the impact of an object on 19 July 2009 (Sánchez-Lavega, A. et al. [2010]. Astrophys. J. 715, L155-L159). The work is based on images obtained during 5 months from the impact to 31 December 2009 taken in visible continuum wavelengths and from 20 July 2009 to 28 May 2010 taken in near-infrared deep hydrogen-methane absorption bands at 2.1-2.3 μm. The impact cloud expanded zonally from ∼5000 km (July 19) to 225,000 km (29 October, about 180° in longitude), remaining meridionally localized within a latitude band from 53.5°S to 61.5°S planetographic latitude. During the first two months after its formation the site showed heterogeneous structure with 500-1000 km sized embedded spots. Later the reflectivity of the debris field became more homogeneous due to clump mergers. The cloud was mainly dispersed in longitude by the dominant zonal winds and their meridional shear, during the initial stages, localized motions may have been induced by thermal perturbation caused by the impact's energy deposition. The tracking of individual spots within the impact cloud shows that the westward jet at 56.5°S latitude increases its eastward velocity with altitude above the tropopause by 5-10 m s -1. The corresponding vertical wind shear is low, about 1 m s -1 per scale height in agreement with previous thermal wind estimations. We found evidence for discrete localized meridional motions with speeds of 1-2 m s -1. Two numerical models are used to simulate the observed cloud dispersion. One is a pure advection of the aerosols by the winds and their shears. The other uses the EPIC code, a nonlinear calculation of the evolution of the potential vorticity field generated by a heat pulse that simulates the impact. Both models reproduce the observed global structure of the cloud and the dominant zonal dispersion of the aerosols, but not the details of the cloud morphology. The reflectivity of the impact cloud decreased exponentially with a characteristic timescale of 15 days; we can explain this behavior with a radiative transfer model of the cloud optical depth coupled to an advection model of the cloud dispersion by the wind shears. The expected sedimentation time in the stratosphere (altitude levels 5-100 mbar) for the small aerosol particles forming the cloud is 45-200 days, thus aerosols were removed vertically over the long term following their zonal dispersion. No evidence of the cloud was detected 10 months after the impact. Title: Hinode/EIS plasma diagnostics in the flaring solar chromosphere Authors: Graham, D. R.; Fletcher, L.; Hannah, I. G. Bibcode: 2011A&A...532A..27G Altcode: Context. The impulsive phase of solar flares is a time of rapid energy deposition and heating in the lower solar atmosphere, leading to changes in the temperature, density, ionisation and velocity structure of this region.
Aims: We aim to study the lower atmosphere during the impulsive phase of a flare using imaging and spectroscopic data from Hinode/EIS, RHESSI and TRACE. We place these observations in context by using a wide range of temperature observations from each instrument.
Methods: We analyse sparse raster data from the Hinode/EIS spectrometer to derive the density and line-of-sight velocity in flare footpoints, in a GOES C6.6 flare observed on 05-June-2007. The raster duration was 150s across the centre of a small active region, allowing multiple exposures of the flare ribbons and footpoints. Using RHESSI and Hinode/XRT we test both non-thermal and thermal models for the HXR emission.
Results: During the flare impulsive phase, we find evidence from XRT for flare footpoints at temperatures exceeding 7 MK. We measure the electron number density increasing up to a few ×1010 cm-3 in the footpoints, at temperatures of ~1.5-2 MK, accompanied by small downflows at temperatures below Fe XIII and upflows of up to ~140 km s-1 at temperatures above. This is reasonable in the context of HXR diagnostics of the flare electron beam. The electrons inferred have sufficient energy to affect the chromospheric ionisation structure.
Conclusions: EIS sparse raster data coupled with RHESSI imaging and spectroscopy prove useful here in studying the lower atmosphere of solar flares, and in this event suggest heat deposition relatively high in the chromosphere drives chromospheric evaporation while increasing the observed electron densities at footpoints. However, from RHESSI spectral fitting it is not possible to say whether the data are more consistent with a model including a non-thermal beam, or purely thermal model. Title: Automated sunspot detection and the evolution of sunspot magnetic fields during solar cycle 23 Authors: Watson, Fraser; Fletcher, Lyndsay Bibcode: 2011IAUS..273...51W Altcode: 2010arXiv1009.5884W The automated detection of solar features is a technique which is relatively underused but if we are to keep up with the flow of data from spacecraft such as the recently launched Solar Dynamics Observatory, then such techniques will be very valuable to the solar community. Automated detection techniques allow us to examine a large set of data in a consistent way and in relatively short periods of time allowing for improved statistics to be carried out on any results obtained. This is particularly useful in the field of sunspot study as catalogues can be built with sunspots detected and tracked without any human intervention and this provides us with a detailed account of how various sunspot properties evolve over time. This article details the use of the Sunspot Tracking And Recognition Algorithm (STARA) to create a sunspot catalogue. This catalogue is then used to analyse the magnetic fields in sunspot umbrae from 1996-2010, taking in the whole of solar cycle 23. Title: Deep winds beneath Saturn's upper clouds from a seasonal long-lived planetary-scale storm Authors: Sánchez-Lavega, A.; del Río-Gaztelurrutia, T.; Hueso, R.; Gómez-Forrellad, J. M.; Sanz-Requena, J. F.; Legarreta, J.; García-Melendo, E.; Colas, F.; Lecacheux, J.; Fletcher, L. N.; Barrado y Navascués, D.; Parker, D.; International Outer Planet Watch Team; Akutsu, T.; Barry, T.; Beltran, J.; Buda, S.; Combs, B.; Carvalho, F.; Casquinha, P.; Delcroix, M.; Ghomizadeh, S.; Go, C.; Hotershall, J.; Ikemura, T.; Jolly, G.; Kazemoto, A.; Kumamori, T.; Lecompte, M.; Maxson, P.; Melillo, F. J.; Milika, D. P.; Morales, E.; Peach, D.; Phillips, J.; Poupeau, J. J.; Sussenbach, J.; Walker, G.; Walker, S.; Tranter, T.; Wesley, A.; Wilson, T.; Yunoki, K. Bibcode: 2011Natur.475...71S Altcode: Convective storms occur regularly in Saturn's atmosphere. Huge storms known as Great White Spots, which are ten times larger than the regular storms, are rarer and occur about once per Saturnian year (29.5 Earth years). Current models propose that the outbreak of a Great White Spot is due to moist convection induced by water. However, the generation of the global disturbance and its effect on Saturn's permanent winds have hitherto been unconstrained by data, because there was insufficient spatial resolution and temporal sampling to infer the dynamics of Saturn's weather layer (the layer in the troposphere where the cloud forms). Theoretically, it has been suggested that this phenomenon is seasonally controlled. Here we report observations of a storm at northern latitudes in the peak of a weak westward jet during the beginning of northern springtime, in accord with the seasonal cycle but earlier than expected. The storm head moved faster than the jet, was active during the two-month observation period, and triggered a planetary-scale disturbance that circled Saturn but did not significantly alter the ambient zonal winds. Numerical simulations of the phenomenon show that, as on Jupiter, Saturn's winds extend without decay deep down into the weather layer, at least to the water-cloud base at pressures of 10-12bar, which is much deeper than solar radiation penetrates. Title: Solar flares: observations vs simulations Authors: Rubio da Costa, Fatima; Zuccarello, Francesca; Labrosse, Nicolas; Fletcher, Lyndsay; Prosecký, Tomáš; Kašparová, Jana Bibcode: 2011IAUS..274..182R Altcode: In order to study the properties of faint, moderate and bright flares, we simulate the conditions of the solar atmosphere using a radiative hydrodynamic model (Abbett & Hawley, 1999). A constant beam of non-thermal electrons is injected at the apex of a 1D coronal loop and heating from thermal soft X-ray emission is included. We compare the results with some observational data in Ly-α (using TRACE 1216 and 1600 Å data and estimating the ``pure'' Ly-α emission) and in Hα (data taken with a Multichannel Flare Spectrograph, at the Ondrejov Observatory). Title: The Magnetic and Dynamic Properties of Flaring Active Regions Authors: Watson, Fraser; Fletcher, L. Bibcode: 2011SPD....42.1201W Altcode: 2011BAAS..43S.1201W As solar cycle 24 begins, the return of active regions and solar flares provides new opportunities for the study of the sun, particularly with the recently launched Solar Dynamics Orbiter. This allows these regions to be studied in more detail than has previously been possible. We have developed a magnetic segmentation algorithm that allows us to examine magnetic structures within active region magnetograms and track their evolution in space and time. With this, we can build up a picture of the photospheric properties of the active region before and after solar flares. We can then examine the structures for changes that occur around the time of flaring and compare these with changes seen in other active regions at times of emergence, flaring and decay. We present the findings of a study of flaring active regions, most of which come from SOHO/MDI data and two use data from SDO/HMI. These two regions observed by HMI include two of the strongest flares seen during the beginning of solar cycle 24 whilst the MDI regions are very active regions from the peak of solar cycle 23. In this way we can also compare any changes observed between the two cycles. Title: Doppler Signatures In EVE Spectra Authors: Hudson, Hugh S.; Chamberlin, P.; Woods, T.; Fletcher, L.; Graham, D. Bibcode: 2011SPD....42.2124H Altcode: 2011BAAS..43S.2124H The Extreme-ultraviolet Variability Experiment (EVE) on SDO is providing a comprehensive set of EUV spectra of the Sun as a star. The routine sampling is with 10 s integrations at a resolution of 0.1 nm. Although this resolution corresponds to only some 1000 km/s in velocity space, we demonstrate that the instrument is stable enough to detect the SDO orbital motion of a few km/s readily in the bright He II line at 30.4 nm. We find the random error in the centroid location of this line to be less than one pm (less than 1 km/s) per 10 s integration. We also note systematic effects from a variety of causes. For flare observations, the line centroid position depends on the flare position. We discuss the calibration of this effect and show that EVE can nonetheless provide clear Doppler signatures that may be interpreted in terms of flare dynamics. This information has some value in and of itself, because of EVE's sensitivity, but we feel that it will be of greatest importance when combined with imagery (e.g., via AIA) a modeling. We discuss flare signatures in several events, e.g. the gamma-ray flare SOL2010-06-12 and SOL2011-02-16T:07:44, taking advantage of AIA image comparisons. Title: Uranus’ cloud structure and seasonal variability from Gemini-North and UKIRT observations Authors: Irwin, P. G. J.; Teanby, N. A.; Davis, G. R.; Fletcher, L. N.; Orton, G. S.; Tice, D.; Kyffin, A. Bibcode: 2011Icar..212..339I Altcode: Observations of Uranus were made in September 2009 with the Gemini-North telescope in Hawaii, using both the NIFS and NIRI instruments. Observations were acquired in Adaptive Optics mode and have a spatial resolution of approximately 0.1″.

NIRI images were recorded with three spectral filters to constrain the overall appearance of the planet: J, H-continuum and CH4(long), and long slit spectroscopy measurements were also made (1.49-1.79 μm) with the entrance slit aligned on Uranus’ central meridian. To acquire spectra from other points on the planet, the NIFS instrument was used and its 3″ × 3″ field of view stepped across Uranus’ disc. These observations were combined to yield complete images of Uranus at 2040 wavelengths between 1.476 and 1.803 μm.

The observed spectra along Uranus central meridian were analysed with the NEMESIS retrieval tool and used to infer the vertical/latitudinal variation in cloud optical depth. We find that the 2009 Gemini data perfectly complement our observations/conclusions from UKIRT/UIST observations made in 2006-2008 and show that the north polar zone at 45°N has continued to steadily brighten while that at 45°S has continued to fade. The improved spatial resolution of the Gemini observations compared with the non-AO UKIRT/UIST data removes some of the earlier ambiguities with our previous analyses and shows that the opacity of clouds deeper than the 2-bar level does indeed diminish towards the poles and also reveals a darkening of the deeper cloud deck near the equator, perhaps coinciding with a region of subduction. We find that the clouds at 45°N,S lie at slightly lower pressures than the clouds at more equatorial latitudes, which suggests that they might possibly be composed of a different condensate, presumably CH4 ice, rather than H2S or NH3 ice, which is assumed for the deeper cloud. In addition, analysis of the centre-to-limb curves of both the Gemini/NIFS and earlier UKIRT/UIST IFU observations shows that the main cloud deck has a well-defined top, and also allows us to better constrain the particle scattering properties.

Overall, Uranus appeared to be less convectively active in 2009 than in the previous 3 years, which suggests that now the northern spring equinox (which occurred in 2007) is passed the atmosphere is settling back into the quiescent state seen by Voyager 2 in 1986. However, a number of discrete clouds were still observed, with one at 15°N found to lie near the 500 mb level, while another at 30°N, was seen to be much higher at near the 200 mb level. Such high clouds are assumed to be composed of CH4 ice. Title: Relationship Between Hard and Soft X-ray Emission Components of a Solar Flare Authors: Guo, Jingnan; Liu, Siming; Fletcher, Lyndsay; Kontar, Eduard P. Bibcode: 2011ApJ...728....4G Altcode: 2010arXiv1012.4346G X-ray observations of solar flares routinely reveal an impulsive high-energy and a gradual low-energy emission component, whose relationship is one of the key issues of solar flare study. The gradual and impulsive emission components are believed to be associated with, respectively, the thermal and nonthermal components identified in spectral fitting. In this paper, a prominent ~50 s hard X-ray (HXR) pulse of a simple GOES class C7.5 flare on 2002 February 20 is used to study the association between high-energy, non-thermal, and impulsive evolution, and low-energy, thermal, and gradual evolution. We use regularized methods to obtain time derivatives of photon fluxes to quantify the time evolution as a function of photon energy, obtaining a break energy between impulsive and gradual behavior. These break energies are consistent with a constant value of ~11 keV in agreement with those found spectroscopically between thermal and non-thermal components, but the relative errors of the former are greater than 15% and much greater than the few percent errors found from the spectral fitting. These errors only weakly depend on assuming an underlying spectral model for the photons, pointing to the current data being inadequate to reduce the uncertainties rather than there being a problem associated with an assumed model. The time derivative method is used to test for the presence of a "pivot energy" in this flare. Although these pivot energies are marginally consistent with a constant value of ~9 keV, its values in the HXR rise phase appear to be lower than those in the decay phase. Assuming that electrons producing the high-energy component have a power-law distribution and are accelerated from relatively hot regions of a background plasma responsible for the observed thermal component, a low limit is obtained for the low-energy cutoff. This limit is always lower than the break and pivot energies and is located in the tail of the Maxwellian distribution of the thermal component. Title: Jupiter In The Crosshairs: Recent Impacts And Their Implications Authors: Hammel, Heidi B.; de Pater, I.; Simon-Miller, A. A.; Fletcher, L.; Boslough, M. B.; Orton, G. S.; Djorgovski, G.; Yanamandra-Fisher, P.; Wong, M. H.; Hueso, R.; Sánchez-Lavega, A.; Go, C.; Wesley, A.; Pérez-Hoyos, S.; Edwards, M.; Clarke, J. T.; Noll, K. S. Bibcode: 2011AAS...21715608H Altcode: 2011BAAS...4315608H No abstract at ADS Title: The atmospheric influence, size and possible asteroidal nature of the July 2009 Jupiter impactor Authors: Orton, G. S.; Fletcher, L. N.; Lisse, C. M.; Chodas, P. W.; Cheng, A.; Yanamandra-Fisher, P. A.; Baines, K. H.; Fisher, B. M.; Wesley, A.; Perez-Hoyos, S.; de Pater, I.; Hammel, H. B.; Edwards, M. L.; Ingersoll, A. P.; Mousis, O.; Marchis, F.; Golisch, W.; Sanchez-Lavega, A.; Simon-Miller, A. A.; Hueso, R.; Momary, T. W.; Greene, Z.; Reshetnikov, N.; Otto, E.; Villar, G.; Lai, S.; Wong, M. H. Bibcode: 2011Icar..211..587O Altcode: Near-infrared and mid-infrared observations of the site of the 2009 July 19 impact of an unknown object with Jupiter were obtained within days of the event. The observations were used to assess the properties of a particulate debris field, elevated temperatures, and the extent of ammonia gas redistributed from the troposphere into Jupiter's stratosphere. The impact strongly influenced the atmosphere in a central region, as well as having weaker effects in a separate field to its west, similar to the Comet Shoemaker-Levy 9 (SL9) impact sites in 1994. Temperatures were elevated by as much as 6 K at pressures of about 50-70 mbar in Jupiter's lower stratosphere near the center of the impact site, but no changes above the noise level (1 K) were observed in the upper stratosphere at atmospheric pressures less than ∼1 mbar. The impact transported at least ∼2 × 10 15 g of gas from the troposphere to the stratosphere, an amount less than derived for the SL9 C fragment impact. From thermal heating and mass-transport considerations, the diameter of the impactor was roughly in the range of 200-500 m, assuming a mean density of 2.5 g/cm 3. Models with temperature perturbations and ammonia redistribution alone are unable to fit the observed thermal emission; non-gray emission from particulate emission is needed. Mid-infrared spectroscopy of material delivered by the impacting body implies that, in addition to a silicate component, it contains a strong signature that is consistent with silica, distinguishing it from SL9, which contained no evidence for silica. Because no comet has a significant abundance of silica, this result is more consistent with a "rocky" or "asteroidal" origin for the impactor than an "icy" or "cometary" one. This is surprising because the only objects generally considered likely to collide with Jupiter and its satellites are Jupiter-Family Comets, whose populations appear to be orders of magnitude larger than the Jupiter-encountering asteroids. Nonetheless, our conclusion that there is good evidence for at least a major asteroidal component of the impactor composition is also consistent both with constraints on the geometry of the impactor and with results of contemporaneous Hubble Space Telescope observations. If the impact was not simply a statistical fluke, then our conclusion that the impactor contained more rocky material than was the case for the desiccated Comet SL9 implies a larger population of Jupiter-crossing asteroidal bodies than previously estimated, an asteroidal component within the Jupiter-Family Comet population, or compositional differentiation within these bodies. Title: Jupiter's stratospheric hydrocarbons and temperatures after the July 2009 impact from VLT infrared spectroscopy Authors: Fletcher, L. N.; Orton, G. S.; de Pater, I.; Mousis, O. Bibcode: 2010A&A...524A..46F Altcode:
Aims: Thermal infrared imaging and spectroscopy of the July 19, 2009 Jupiter impact site has been used to identify unique features of the physical and chemical atmospheric response to this unexpected collision.
Methods: Images and high-resolution spectra of methane, ethane and acetylene emission (7-13 μm) from the 2009 impact site were obtained by the Very Large Telescope (VLT) mid-infrared camera/spectrometer instrument, VISIR. An optimal estimation retrieval algorithm was used to determine the atmospheric temperatures and hydrocarbon distribution in the month following the impact.
Results: Ethane spectra at 12.25 μm could not be explained by a rise in temperature alone. Ethane was enhanced by 1.7-3.2 times the background abundance on July 26, implying production as the result of shock chemistry in a high C/O ratio environment, favouring an asteroidal origin for the 2009 impactor. Small enhancements in acetylene emission were also observed over the impact site. However, no excess methane emission was found over the impact longitude, either with broadband 7.9-μm imaging 21 h after the impact, or with center-to-limb scans of strong and weak methane lines between 7.9 and 8.1 μm in the ensuing days, indicating either extremely rapid cooling in the initial stages, or an absence of heating in the upper stratosphere (p < 10 mbar) due to the near-horizontal orientation of the impact. Models of 12.3-μm spectra are consistent with a ≈ 3 K rise in the lower stratosphere (p > 10 mbar), though this solution is highly dependent on the spectral properties of stratospheric debris. The enhanced ethane emission was localised over the impact streak, and was diluted in the ensuing weeks by redistribution of heated gases by zonal flow and mixing with the unperturbed jovian air.
Conclusions: The different thermal energy deposition profiles, in addition to the highly reducing (C/O > 1) environment and shallow impactor angle, suggest that (a) the 2009 plume and shock-fronts did not reach the sub-microbar altitudes of the Shoemaker-Levy 9 plumes; and (b) models of a cometary impact are not directly applicable to the unique impact circumstances of July 2009. Title: Compositional Constraints on the Atmospheres of Uranus and Neptune from Herschel and Spitzer Spectroscopic Observations Authors: Orton, G. S.; Moreno, R.; Lellouch, E.; Fletcher, L. N.; Hartogh, P.; Jarchow, C.; Feuchtgruber, H.; Line, M. R.; Herschel Key Project On Water; Related Chemistry in Solar System Team Bibcode: 2010AGUFM.P14A..07O Altcode: Key elements of planetary compositions provide one of the most fundamental constraints on the origins and evolution of major bodies in the solar system. For the icy giants, Uranus and Neptune, acquiring compositional information has been a challenge because of their faintness. Great strides have been made with the advent of cryogenically cooled space-borne telescopes, however, and we report here the most recent of these results from Spitzer and Herschel telescopes, the latter including data taken within the framework of the Key Project "Water and Related Chemistry in the Solar system". Our interpretation of these results is set in the context of earlier results obtained by the ISO LWS and SWS spectrometers, together with relevant Earth-based observations. We will specifically discuss the chemical inventory and abundances stratospheric hydrocarbons, the implications of thermal structure for deep atmospheric composition, and improved constraints on the D/H ratio in Neptune. Title: Solar Flares and the Chromosphere Authors: Fletcher, L.; Turkmani, R.; Hudson, H. S.; Hawley, S. L.; Kowalski, A.; Berlicki, A.; Heinzel, P. Bibcode: 2010arXiv1011.4650F Altcode: A white paper prepared for the Space Studies Board, National Academy of Sciences (USA), for its Decadal Survey of Solar and Space Physics (Heliophysics), reviewing and encouraging studies of flare physics in the chromosphere. Title: Unveiling Uranus' Clouds: New Observations From Gemini-North NIFS And NIRI Authors: Irwin, Patrick G. J.; Teanby, N. A.; Davis, G. R.; Fletcher, L. N.; Orton, G.; Tice, D. Bibcode: 2010DPS....42.4404I Altcode: 2010BAAS...42.1045I Observations of Uranus were made in September 2009 with the Gemini-North telescope in Hawaii, using both the NIFS and NIRI instruments. Adaptive optics were used to achieve a spatial resolution of approximately 0.1 arcsec.

NIRI images were recorded with three spectral filters to constrain the overall appearance of the planet: J, H-continuum and CH4(long), and long slit spectra (1.49 to 1.79 microns) were obtained with the slit aligned on Uranus’ central meridian. In addition, the NIFS instrument was used to acquire spectra from other points on the planet, stepping the NIFS 3 x 3 arcsec field of view across Uranus’ disc. These observations were combined to yield complete images of Uranus at 2040 wavelengths between 1.476 and 1.803 microns with a spectral resolution of 5000.

The observed spectra along Uranus central meridian were analyzed with the NEMESIS retrieval tool and used to infer the vertical/latitudinal variation in cloud optical depth. We find that the 2009 Gemini data perfectly complement our observations/conclusions from UKIRT/UIST observations made in 2006-2008 and show that the north polar zone at 45N has continued to steadily brighten while that at 45S has continued to fade. The improved spatial resolution of the Gemini observations compared with the non-AO UKIRT/UIST data remove many of the earlier ambiguities inherent in the previous analysis.

Overall, Uranus appeared to be less convectively active in 2009 than in the previous 3 years, which suggests that now the equinox (which occurred in 2007) is over the atmosphere is settling back into the quiescent state seen by Voyager 2 in 1986. However, one discrete cloud was captured in the NIFS observations and was estimated to lie at a pressure level of 300-400 mbar. Title: The Optical Depth of White-light Flare Continuum Authors: Potts, Hugh; Hudson, Hugh; Fletcher, Lyndsay; Diver, Declan Bibcode: 2010ApJ...722.1514P Altcode: 2010arXiv1004.1039P The white-light continuum emission of a solar flare remains a puzzle as regards its height of formation and its emission mechanism(s). This continuum and its extension into the near-UV contain the bulk of the energy radiated by a flare, and so its explanation is a high priority. We describe a method to determine the optical depth of the emitting layer and apply it to the well-studied flare of 2002 July 15, making use of MDI pseudo-continuum intensity images. We find the optical depth of the visible continuum in all flare images, including an impulsive ribbon to be small, consistent with the observation of Balmer and Paschen edges in other events. Title: First Earth-based Detection of a Superbolide on Jupiter Authors: Hueso, R.; Wesley, A.; Go, C.; Pérez-Hoyos, S.; Wong, M. H.; Fletcher, L. N.; Sánchez-Lavega, A.; Boslough, M. B. E.; de Pater, I.; Orton, G. S.; Simon-Miller, A. A.; Djorgovski, S. G.; Edwards, M. L.; Hammel, H. B.; Clarke, J. T.; Noll, K. S.; Yanamandra-Fisher, P. A. Bibcode: 2010ApJ...721L.129H Altcode: 2010arXiv1009.1824H Cosmic collisions on planets cause detectable optical flashes that range from terrestrial shooting stars to bright fireballs. On 2010 June 3 a bolide in Jupiter's atmosphere was simultaneously observed from the Earth by two amateur astronomers observing Jupiter in red and blue wavelengths. The bolide appeared as a flash of 2 s duration in video recording data of the planet. The analysis of the light curve of the observations results in an estimated energy of the impact of (0.9-4.0) × 1015 J which corresponds to a colliding body of 8-13 m diameter assuming a mean density of 2 g cm-3. Images acquired a few days later by the Hubble Space Telescope and other large ground-based facilities did not show any signature of aerosol debris, temperature, or chemical composition anomaly, confirming that the body was small and destroyed in Jupiter's upper atmosphere. Several collisions of this size may happen on Jupiter on a yearly basis. A systematic study of the impact rate and size of these bolides can enable an empirical determination of the flux of meteoroids in Jupiter with implications for the populations of small bodies in the outer solar system and may allow a better quantification of the threat of impacting bodies to Earth. The serendipitous recording of this optical flash opens a new window in the observation of Jupiter with small telescopes. Title: Vertical Cloud Structure Of The 2009 Jupiter Impact Based On HST/WFC3 Observations Authors: Perez-Hoyos, Santiago; Sanz-Requena, J. F.; Sanchez-Lavega, A.; Wong, M.; Hueso, R.; Hammel, H. B.; Orton, G. S.; Fletcher, L. N.; de Pater, I.; Simon-Miller, A. A.; Clarke, J. T.; Noll, K.; Yanamandra-Fisher, P. A. Bibcode: 2010DPS....42.1107P Altcode: 2010BAAS...42R1018P The impact of a body of unknown origin with Jupiter in July 2009 (Sánchez-Lavega et al., Astrophys. J. Lett, Vol. 715, L155. 2010) produced an intense perturbation of the planet's atmosphere at the visible levels. The perturbation was caused by dense aerosol material; this strongly absorbing material expanded steadily as it was advected by the local winds. This phenomenon was observed at high spatial resolution by the Hubble Space Telescope in July, August, September and November 2009 with recently installed Wide Field Camera 3. In this work, we present radiative transfer modeling of the observed reflectivity in the near UV (200nm) to near IR (950nm) range. The geometrical and spectral variations of reflectivity elucidate the main particle properties (optical thickness, size, imaginary refractive index) and their temporal evolution. The aerosol particles that formed during the impact have a mean radius of about 1 micron and are located high in the atmosphere (above 10 mbar), in good agreement ith ground-based observations in deep methane absorption bands in the near infrared. The density of this particle layer decreases with time until it approaches that of the pre-impact atmosphere. These results are also discussed in terms of what we know from other impacts in Jupiter (1994's SL9 event and 2010's bolide). Acknowledgements: SPH, ASL and RH are supported by the Spanish MICIIN AYA2009-10701 with FEDER and Grupos Gobierno Vasco IT-464-07. Title: Long-term Evolution of the Aerosol Debris Cloud Produced by the 2009 Impact of an Object with Jupiter Authors: Sanchez-Lavega, Agustin; Orton, G. S.; Hueso, R.; Pérez-Hoyos, S.; Fletcher, L. N.; Garcia-Melendo, E.; Gomez, J. M.; de Pater, I.; Wong, M.; Hammel, H. B.; Yanamandra-Fisher, P.; Simon-Miller, M.; Barrado-Izagirre, N.; Marchis, F.; Mousis, O.; Ortiz, J. L.; Garcia, J.; Cecconi, M.; Clarke, J. T.; Noll, K.; Pedraz, S.; Wesley, A.; McConnel, N.; Kalas, P.; Graham, J.; McKenzie, L.; Reddy, V.; Golisch, W.; Griep, D.; Sears, P.; International Outer PLanet Watch (IOPW) Bibcode: 2010DPS....42.3101S Altcode: 2010BAAS...42Q1009S We report the evolution of the cloud of aerosols produced in the atmosphere of Jupiter by the impact of an object in 19 July 2009 (Sánchez-Lavega et al., Astrophys. J. Lett, Vol. 715, L155. 2010). This study is based on images obtained with a battery of ground-based telescopes and the Hubble Space Telescope in the visible and in the deep near infrared absorption bands at 2.1-2.3 microns from the impact date to 31 December 2009. The impact cloud expanded zonally from 5000 km (July 19) to 225,000 km (about 180 deg in longitude by 29 October) and it was meridionally localized within a latitude band from -53.5 deg to -61.5 deg. During the first two months it showed a heterogeneous structure with embedded spots of a size of 500 - 1000 km. The cloud was mainly dispersed in longitude by the dominant zonal winds and their meridional shear and, during the initial stages, by the action of local motions perhaps originated by the thermal perturbation produced at the impact site. The tracking of individual spots within the impact cloud showed that the winds increase their eastward velocity with altitude above the tropopause by 5-10 m/s. We found evidence of discrete localized meridional motions in the equatorward direction with speeds of 1 - 2 m/s. Measurements of the cloud reflectivity evolution during the whole period showed that it followed an exponential decrease with a characteristic time of 15 days, shorter than the 45 - 200 days sedimentation time for the small aerosol particles in the stratosphere. A radiative transfer model of the cloud optical depth coupled to an advection model of the cloud dispersion by the wind shears, reproduces this behavior. Acknowledgements: ASL, RH, SPH, NBI are supported by the Spanish MICIIN AYA2009-10701 with FEDER and Grupos Gobierno Vasco IT-464-07. Title: Seasonal and Temporal Changes on Jupiter and Saturn: A Review of Ground-based Observations Authors: Yanamandra-Fisher, Padma A.; Orton, G. S.; Fisher, B. M.; Fletcher, L. N.; Miller, A. S. Bibcode: 2010DPS....42.1102Y Altcode: 2010BAAS...42.1017Y We report on the seasonal and temporal changes observed on Jupiter and Saturn, based on near- and mid-infrared data acquired from several observatories (NASA/InfraRed Telescope Facility, NAOJ/Subaru, ESO/Very Large Telescope) and provide compelling rationale for a coordinated network of large telescopes for continued ground-based observations. Jupiter has been experiencing an era of atmospheric global upheaval since 2005, the observed atmospheric changes being manifestations of changes in local meteorology and latent physical parameters of the system, and occur on various timescales and latitudes. The discrete storms in Jupiter's atmosphere have undergone significant changes over the past decade. The merger of the three white ovals into Oval BA and its subsequent color change in 2006 appear to be correlated to periodic interactions with the Great Red Spot (GRS). Subsequent episodes of GRS-Oval BA interactions in 2006 and 2008 and the upcoming interaction in 2010 provide snapshots of changes in the local meteorology. We identify relationships between latent physical variables of the spatially and temporally changing systems in terms of cloud opacities, aerosol distribution and thermal fields. Ground-based near- and mid-infrared observations of Saturn from 1995 - 2009, covering half a Saturnian year, provide a rich data set to model seasonal changes in Saturn's atmosphere from autumnal equinox (1995) to vernal equinox (2009). Since 1995, as Saturn's south pole received increasing solar insolation, its albedo exhibits an increase in reflectivity at mid-latitudes in the southern hemisphere, decreasing towards the equator, anti-correlated with the thermal field. Similar to equatorial oscillations of temperatures on Earth and Jupiter, Saturn displays stratospheric temperature oscillations, with a period of half a Saturnian year, suggesting the influence of seasonal forcing. We anticipate development of similar phenomena in the next few years, as Saturn approaches northern solstice. Title: Mid-IR Atmospheric Tracers of Jupiter's Storm Oval BA Authors: Shannon, Matthew J.; Orton, G.; Fletcher, L. Bibcode: 2010DPS....42.1103S Altcode: 2010BAAS...42R1017S The 2005-2006 reddening of a major anticyclonic storm, known as Oval BA, in Jupiter's turbulent atmosphere may well be a paradigm for the formation of red-colored vortices on the giant planets, including Jupiters Great Red Spot. Mid-infrared observations can be effectively used to determine physical and chemical properties of the atmosphere, and we present the results of mid-infrared thermal imaging observations, collected from NASAs Infrared Telescope Facility (IRTF) in Hawaii, ESOs Very Large Telescope (VLT) in Chile and the NAOJ Subaru Telescope in Hawaii between spring of 2005 and summer of 2006. These address the role of atmospheric tracers, including cloud opacity, the ammonia gas content, and the variation of the fraction of para- to ortho-hydrogen from local thermal equilibrium in assessing the rate of upwelling. These properties were retrieved with the Oxford-developed code, Nemesis, with the purpose of providing constraints on dynamical models in an effort to identify the mechanism for the color change. The most obvious change is that the temperature gradient from the inner to the outer part of Oval BA increased over the time of the color change, indicating a strengthening of the intensity of the vortex. Title: Saturn's "String of Pearls” After Five Years: Still There, Moving Backwards Faster in the Voyager System Authors: Baines, Kevin H.; Momary, T. W.; Fletcher, L. N.; Buratti, B. J.; Brown, R. H.; Clark, R. N.; Nicholson, P. D. Bibcode: 2010DPS....42.4103B Altcode: 2010BAAS...42.1039B Since July 2005, the Visual Infrared Mapping Spectrometer (VIMS) onboard the Cassini Orbiter has been following an enigmatic feature centered at 33.9 degrees (planetocentric ) north latitude. Observed in detail on 14 occasions between July 2005 and July 2010, the feature is seen only in the 5-micron thermal window which probes large-particle clouds down to the ∼ 4-bar level. This feature is comprised of a main cloud layer near 1.5-3 bar which has 21-25 regularly spaced, near- uniformly-sized, circularly-shaped clearings which together span, on average, 94 degrees of longitude. In VIMS 5-micron imagery, which observes the warm glow of Saturn generated at depth, these regularly spaced and shaped clearings appear bright while the surrounding cloud, observed in silhouette, appears dark- hence the colloquial name "String of Pearls". Each clearing is about 1 degree of longitude (∼900 km) wide, and is, on average over the five-years period, 4.3 degrees of longitude from its neighbor. In latitude, adjacent pearls are typically 0.4 degrees - or about 1 pearl radius - apart. At various times over the past five years of observations, the longitudinal length has varied from 76 to 104 degrees and the mean separation between clearings has varied from 3.6 to 5.0 degrees, while the mean latitude of the structure has ranged from 32.9 to 34.8 degrees - or by 2 mean diameters of the pearls. The pearl structure moves retrograde in the Voyager system (Desch and Kaiser, Geophys. Res. Lett 8, 253-256, 1981) with an average speed over five years of 21.84 ± 0.02 m/s. Since late 2007, the mean latitude increased from 34.0 ± 0.2 to 34.5 ± 0.2 deg as the retrograde speed increased from 21.73 ± 0.09 m/s to 22.02 ± 0.08 m/s, making it the fastest moving retrograde feature observed by Cassini/VIMS in non-polar regions. Title: Saturn's Equatorial Plumes after Five Years: Still Lurking under the Haze Authors: Momary, Thomas W.; Baines, K. H.; Fletcher, L. N.; Buratti, B. J.; Brown, R. H.; Clark, R. N.; Nicholson, P. D. Bibcode: 2010DPS....42.1119M Altcode: 2010BAAS...42.1021M Numerous large, discrete cloud features have been observed for five years underneath Saturn's equatorial haze. They were clearly observed on three occasions - June 28, 2005, April 21, 2006 and May 1, 2010 - from a vantage point directly over the knife-edge of the rings, which reduced the ring obscuration of the disk to just ± 1 degrees of latitude centered at the equator. These features are seen only in the 5-micron thermal window which probes large-particle clouds down to the ∼ 4-bar level. In VIMS 5-micron imagery, which observes the warm glow of Saturn generated at depth, these deep clouds are observed in silhouette, appearing as dark features against the background glow. Spectral modeling indicates that they are primarily located in the 2-3 bar region. However, smaller particles of ammonia may be present overhead as a relatively small component of the 5-micron extinction. Indeed, the correlation of these features with the exceedingly high and thick equatorial haze layer indicates a plausible link: That these features involve vertical transport of gaseous condensibles to the upper troposphere forming the thick haze that is observed in images taken in reflected sunlight. The features are concentrated in two narrow, symmetrical cloudy zones between 4 and 8 degrees planetocentric latitude in both hemispheres, where they cover significant fractions, although varying, amounts of the total area of these latitudinal bands: ∼ 55% in 2005-2006 vs ∼ 28% in 2010. The mean area of the average feature was roughly constant over all three observations, with the longitudinal extent of the average feature in 2005-2006 decreasing ∼10% from 8 degrees ( 8000 km) to 7.1 degrees in 2010 while the mean latitudinal extent increased by ∼10% from 3.05 in 2005 vs 3.4 degrees in 2010. Title: Solar Flares and the Chromosphere: A white paper for the Decadal Survey Authors: Hudson, H. S.; Fletcher, L.; Turkmani, R.; Hawley, S. L.; Kowalski, A. F.; Berlicki, A.; Heinzel, P. Bibcode: 2010helio2010....1H Altcode: No abstract at ADS Title: The Physical Structure and Chemical Composition of Neptune's Atmosphere from Combined Herschel and Spitzer Spectral Observations Authors: Orton, Glenn S.; Moreno, R.; Lellouch, E.; Fletcher, L. N.; Hartogh, P.; Feuchtgruber, H.; Jarchow, C.; Cavalie, T.; Lara, L.; Rengel, M.; Gonzalez, A.; Line, M.; Herschel HssO Key Project Team Bibcode: 2010DPS....42.4409O Altcode: 2010BAAS...42.1047O We report the analysis of thermal-infrared observations of Neptune's disk by experiments on the Spitzer and Herschel Space Telescopes. The Spitzer data were obtained by the IRS instrument at wavelengths between 5.2 and 21.5 microns at a spectral resolving power, R 70, and at wavelengths between 10 and 21.5 microns at R 600. The Herschel observations were made by the PACS instrument's integral field spectrometer between 51 and 220 microns at R 3000, within the framework of the Key Project, ``Water and Related Chemistry in the Solar System''. Our analysis is set in the context of lower-resolution spectra obtained by the ISO LWS and SWS spectrometers covering wavelengths between 28 and 185 microns and the Akari IRC spectrometer covering wavelengths between 5.8 and 13.3 microns at R 40, together with spatially resolved ground-based studies of thermal emission. Our results indicate that that global-mean tropospheric temperatures are lower than those derived from the Voyager radio-occultation experiment, and consistent with the ISO results. Preliminary results (Lellouch et al. 2010 Astron. & Astrophys. In press) indicate that the D/H ratio is 4.5±1.0 x 10-5, consistent with enrichment of deuterium over the protosolar value, and the stratospheric column of H2O is 2.1±0.5 x 1014 cm-2. The peak CH4 abundance in the stratosphere is orders of magnitude larger than if it were cold-trapped below the mean 54-Kelvin tropopause minimum temperature - but consistent with injection from Neptune's warmer south polar region. Good fits to a variety of other stratospheric emission features are obtained: CO, CH3, CO2, C2H2, C2H4, C2H6, C3H8, C4H2. It is also possible to obtain a better fit to a spectral region dominated by C2H6 emission by adding 50-100 ppt of C6H6. Title: First Earth-based Detection of a Superbolide on Jupiter Authors: Hueso, Ricardo; Wesley, A.; Go, C.; Perez-Hoyos, S.; Wong, M. H.; Fletcher, L. N.; Sanchez-Lavega, A.; Boslough, M. B. E.; de Pater, I.; Orton, G. S.; Simon-Miller, A. A.; Djorgovski, S. G.; Edwards, M. L.; Hammel, H. B.; Clarke, J. T.; Noll, K. S.; Yanamandra-Fisher, P. A. Bibcode: 2010DPS....42.3102H Altcode: 2010BAAS...42.1009H On June 3, 2010 a bolide in Jupiter's atmosphere was observed from the Earth for the first time. The flash was detected by amateur astronomers A. Wesley and C. Go observing in two wavelength ranges. We present an analysis of the light curve of those observations that allow estimating the size of the object to be significantly smaller than the SL9 and the July 2009 Jupiter impact. Observations obtained a few days later by large telescopes including HST, VLT, Keck and Gemini showed no signature of the impact in Jupiter atmosphere confirming the small size of the impact body. A nearly continuous observation campaign based on several small telescopes by amateurs astronomers might allow an empirical determination of the flux of meteoroids in Jupiter with implications for the populations of small bodies in the outer solar system and may allow a better quantification of the threat of impacting bodies to Earth.

Acknowledgements: RH, ASL and SPH are supported by the Spanish MICIIN AYA2009-10701 with FEDER and Grupos Gobierno Vasco IT-464-07. LNF is supported by a Glasstone Science Fellowship at the University of Oxford. Title: Thermal Imaging of Jupiter's Giaht Vortices: the Great Red Spot and Oval BA Authors: Orton, G.; Fletcher, L.; Yanamandra-Fisher, P.; Mousis, O.; Fisher, B.; Irwin, P.; Vanzi, L.; Fujiyoshi, T.; Fuse, T.; Simon-Miller, A. Bibcode: 2010epsc.conf..674O Altcode: No abstract at ADS Title: Recovery of Neptune's Near-Polar Stratospheric Hot Spot Authors: Orton, G.; Fletcher, L.; Yanamandra-Fisher, P.; Encrenaz, T.; Leyrat, C.; Hammel, H. Bibcode: 2010epsc.conf..678O Altcode: No abstract at ADS Title: Jupiter 2010: A Busy Year Authors: Go, C. Y.; Wesley, A.; Wong, M.; de Pater, I.; Sanchez-Lavega, A.; Marcus, P.; Huesco, R.; Rogers, J.; Simon-Miller, A.; Orton, G. S.; Yanamandra-Fisher, P.; Fletcher, L. Bibcode: 2010epsc.conf..915G Altcode: No abstract at ADS Title: Potential for stratospheric Doppler windspeed measurements of Jupiter by sub-millimetre spectroscopy Authors: Hurley, J.; Irwin, P. G. J.; Ellison, B. N.; de Kok, R.; Calcutt, S. B.; Teanby, N. A.; Fletcher, L. N.; Irshad, R. Bibcode: 2010P&SS...58.1489H Altcode: The sub-millimetre/microwave range of the spectrum has been exploited in the field of Earth observation by many instruments over the years and has provided a plethora of information on atmospheric chemistry and dynamics - however, this spectral range has not been fully explored in planetary science, having been exclusively employed to carry out ground-based measurements. To this end, a sub-millimetre instrument, the Orbiter Terahertz Infrared Spectrometer (ORTIS), is studied by the University of Oxford and the Rutherford Appleton Laboratory, to meet the requirements of the European Space Agency's Cosmic Visions 2015-2025 programme - in particular, the Europa Jupiter System Mission (EJSM), which has the European Space Agency and the National Aeronautics and Space Administration as partners. ORTIS is designed to measure atmospheric temperature, the abundance of stratospheric water vapour and other jovian gases, and is intended to be capable of retrieving vertical profiles of horizontal windspeed in the stratosphere for the first time, from Doppler-shifted emission lines measured at high spectral resolution. In this work, a preliminary study and implementation of the estimation of windspeed profiles on simulated spectra representative of Jupiter is presented, detailing the development of the retrieval algorithm, showing that a sub-millimetre instrument such as ORTIS should be able to retrieve windspeed profiles to an accuracy of about 15 m/s between 70 and 200 km/0.1-10 mb using a single near-limb measurement, for expected noise amplitudes. Title: From Large-scale Loops to the Sites of Dense Flaring Loops: Preferential Conditions for Long-period Pulsations in Solar Flares Authors: Foullon, C.; Fletcher, L.; Hannah, I. G.; Verwichte, E.; Cecconi, B.; Nakariakov, V. M.; Phillips, K. J. H.; Tan, B. L. Bibcode: 2010ApJ...719..151F Altcode: Long-period quasi-periodic pulsations (QPPs) of solar flares are a class apart from shorter period events. By involving an external resonator, the mechanism they call upon differs from traditional QPP models, but has wider applications. We present a multi-wavelength analysis of spatially resolved QPPs, with periods around 10 minutes, observed in the X-ray spectrum primarily at energies between 3 and 25 keV. Complementary observations obtained in Hα and radio emission in the kHz to GHz frequency range, together with an analysis of the X-ray plasma properties provide a comprehensive picture that is consistent with a dense flaring loop subject to periodic energization and thermalization. The QPPs obtained in Hα and type III radio bursts, with similar periods as the QPPs in soft X-rays, have the longest periods ever reported for those types of data sets. We also report 1-2 GHz radio emission, concurrent with but unrestricted to the QPP time intervals, which is multi-structured at regularly separated narrowband frequencies and modulated with ~18 minute periods. This radio emission can be attributed to the presence of multiple "quiet" large-scale loops in the background corona. Large scale but shorter inner loops below may act as preferential resonators for the QPPs. The observations support interpretations consistent with both inner and outer loops subject to fast kink magnetohydrodynamic waves. Finally, X-ray imaging indicates the presence of double coronal sources in the flaring sites, which could be the particular signatures of the magnetically linked inner loops. We discuss the preferential conditions and the driving mechanisms causing the repeated flaring. Title: Lepton models for TeV emission from SNR RX J1713.7-3946 Authors: Fan, Z. H.; Liu, S. M.; Yuan, Q.; Fletcher, L. Bibcode: 2010A&A...517L...4F Altcode: 2010arXiv1007.0796F
Aims: SNR RX J1713.7-3946 is perhaps one of the best observed shell-type supernova remnants with emissions dominated by energetic particles accelerated near the shock front. The nature of the TeV emission, however, is an issue still open to investigation.
Methods: We carried out a systematic study of four lepton models for the TeV emission with the Markov chain Monte Carlo method.
Results: It is shown that current data already give good constraints on the model parameters. Two commonly used parametric models do not appear to fit the observed radio, X-ray, and γ-ray spectra. Models motivated by diffusive shock acceleration and by stochastic acceleration by compressive waves in the shock downstream give comparably good fits. The former has a sharper spectral cutoff in the hard X-ray band than the latter. Future observations with the HXMT and NuSTAR may distinguish these two models. Title: OT1_lfletche_1: Nitrogen, Phosphorus and Sulphur Chemistry in Saturn's Atmosphere: Internal and External Origins for HCN, HCP and CS Authors: Fletcher, L. N. Bibcode: 2010hers.prop..978F Altcode: Our understanding of some of the fundamental physiochemical processes at work within Saturns gaseous atmosphere is presently limited by the difficulties associated with detection of a number of atmospheric species. Based on our new understanding of Saturns bulk composition and chemistry from the Cassini mission, Herschel/HIFI offers an unprecedented opportunity to detect these species for the first time, and to place constraints on their origins. Radiative transfer calculations have been used in tandem with chemical modelling to select optimal transitions of HCN, HCP and CS for study by HIFI. These species have never been detected before, but are expected to be important secondary repositories for nitrogen, phosphorus and sulphur in Saturns atmosphere. Furthermore, the superb spectral resolution of heterodyne spectroscopy is ideal for distinguishing between broad tropospheric absorptions and narrow stratospheric emissions, allowing us to distinguish between internal and external origins for each species. Tropospheric abundances will be compared to expectations from state of the art thermochemical and photochemical models, in addition to predictions of lightning-induced shock chemistry. Stratospheric abundances will be interpreted in terms of external supply of N, P and S-bearing materials, either from large asteroidal/cometary impacts (where shock chemistry in impact plumes is also important) or influx of material from Enceladus, the rings or interplanetary dust particles. As a result, the HIFI search for the first signatures of Saturns HCN, HCP and CS abundances will serve as vital constraints on internal chemistry and the coupling between Saturns cold atmosphere and external environment, revealing the fundamental processes at work in the cold outer reaches of our Solar System. Title: Jupiter After the 2009 Impact: Hubble Space Telescope Imaging of the Impact-generated Debris and its Temporal Evolution Authors: Hammel, H. B.; Wong, M. H.; Clarke, J. T.; de Pater, I.; Fletcher, L. N.; Hueso, R.; Noll, K.; Orton, G. S.; Pérez-Hoyos, S.; Sánchez-Lavega, A.; Simon-Miller, A. A.; Yanamandra-Fisher, P. A. Bibcode: 2010ApJ...715L.150H Altcode: We report Hubble Space Telescope images of Jupiter during the aftermath of an impact by an unknown object in 2009 July. The 2009 impact-created debris field evolved more slowly than those created in 1994 by the collision of the tidally disrupted comet D/Shoemaker-Levy 9 (SL9). The slower evolution, in conjunction with the isolated nature of this single impact, permits a more detailed assessment of the altitudes and meridional motion of the debris than was possible with SL9. The color of the 2009 debris was markedly similar to that seen in 1994, thus this dark debris is likely to be Jovian material that is highly thermally processed. The 2009 impact site differed from the 1994 SL9 sites in UV morphology and contrast lifetime; both are suggestive of the impacting body being asteroidal rather than cometary. Transport of the 2009 Jovian debris as imaged by Hubble shared similarities with transport of volcanic aerosols in Earth's atmosphere after major eruptions. Title: The Impact of a Large Object on Jupiter in 2009 July Authors: Sánchez-Lavega, A.; Wesley, A.; Orton, G.; Hueso, R.; Perez-Hoyos, S.; Fletcher, L. N.; Yanamandra-Fisher, P.; Legarreta, J.; de Pater, I.; Hammel, H.; Simon-Miller, A.; Gomez-Forrellad, J. M.; Ortiz, J. L.; García-Melendo, E.; Puetter, R. C.; Chodas, P. Bibcode: 2010ApJ...715L.155S Altcode: 2010arXiv1005.2312S On 2009 July 19, we observed a single, large impact on Jupiter at a planetocentric latitude of 55°S. This and the Shoemaker-Levy 9 (SL9) impacts on Jupiter in 1994 are the only planetary-scale impacts ever observed. The 2009 impact had an entry trajectory in the opposite direction and with a lower incidence angle than that of SL9. Comparison of the initial aerosol cloud debris properties, spanning 4800 km east-west and 2500 km north-south, with those produced by the SL9 fragments and dynamical calculations of pre-impact orbit indicates that the impactor was most probably an icy body with a size of 0.5-1 km. The collision rate of events of this magnitude may be five to ten times more frequent than previously thought. The search for unpredicted impacts, such as the current one, could be best performed in 890 nm and K (2.03-2.36 μm) filters in strong gaseous absorption, where the high-altitude aerosols are more reflective than Jupiter's primary clouds. Title: The Impact of a Large Object with Jupiter in July 2009 Authors: Sanchez-Lavega, Agustin; Wesley, A.; Orton, G.; Chodas, P.; Hueso, R.; Perez-Hoyos, S.; Fletcher, L.; Yanamandra-Fisher, P.; Legarreta, J.; Gomez-Forrellad, J. M. Bibcode: 2010EGUGA..1215311S Altcode: The only major impact ever observed directly in the Solar System was that of a large fragmented comet with Jupiter in July (1994) (Comet Shoemaker-Levy 9; SL9). We report here the observation of a second, single, large impact on Jupiter that occurred on 19 July 2009 at a latitude of -55° with an orthogonal entry trajectory and a lower incidence angle compared to those of SL9. The size of the initial aerosol cloud debris was 4,800 km East-West and 2,500 km North-South. Comparison its properties with those produced by the SL9 fragments, coupled with dynamical calculations of possible pre-impact orbits, indicates that the impactor was most probably an icy body with a size of 0.5-1 km. We calculate that the rate of collisions of this magnitude may be five to ten times more frequent than previously thought. The search for unpredicted impacts, such as the current one, could be best performed in the near-infrared methane absorption bands at 890 nm and in the 2.12 to 2.3 μm K methane-hydrogen absorption band, where the high-altitude aerosols detach by their brightness relative to Jupiter's primary clouds. We present measurements of the debris dispersion by Jovian winds from a long-term imaging campaign with ground-based telescopes. Ackowledgements: Work was supported by the Spanish MICIIN AYA2009-10701 with FEDER and Grupos Gobierno Vasco IT-464-07, by NASA funds to JPL, Caltech, by the NASA Postdoctoral Program at JPL, and by the Glasstone Fellowship program at Oxford. Title: Radio Observations And Modeling Of A Post-flare Arcade Authors: Bain, Hazel; Fletcher, L. Bibcode: 2010AAS...21632105B Altcode: 2010BAAS...41..912B We present observations of a flaring arcade which was observed by RHESSI, TRACE and the Nobeyama Radioheliograph (NoRH). The event occurred on the west limb of the Sun and whilst EUV observations reveal an arcade structure, the radio emission appears as a single loop. NoRH observations at 17 GHz and 34 GHz show that the spatial distribution of brightness varies along the loop and the relative brightness of looptop and footpoint sources varies over time. We concentrate our investigation on the decay phase of the flare and using estimates of relevant plasma parameters obtained from observations, we attempt to reproduce the observed radio emission. We compare the gyrosynchrotron emission from both a simple dipole and an arcade magnetic field model to investigate line of sight enhancements from optically thin plasma. Using a continuous thermal/nonthermal electron distribution we investigate the contribution from hot thermal plasma. This work was funded by an STFC studentship. Title: Neptune's atmospheric composition from AKARI infrared spectroscopy Authors: Fletcher, L. N.; Drossart, P.; Burgdorf, M.; Orton, G. S.; Encrenaz, T. Bibcode: 2010A&A...514A..17F Altcode: 2010arXiv1003.5571F
Aims: Disk-averaged infrared spectra of Neptune between 1.8 and 13 μm, obtained by the AKARI infrared camera (IRC) in May 2007, have been analysed to (a) determine the globally-averaged stratospheric temperature structure; (b) derive the abundances of stratospheric hydrocarbons; and (c) detect fluorescent emission from CO at 4.7 μm.
Methods: Mid-infrared spectra (SG1 and SG2 channels of AKARI/IRC), with spectral resolutions of 47 and 34 respectively, were modelled using a line-by-line radiative transfer code to determine the temperature structure between 1-1000 μbar and the abundances of CH4, CH3D and higher-order hydrocarbons. A full non-LTE radiative model was then used to determine the best fitting CO profile to reproduce the fluorescent emission observed at 4.7 μm in the NG channel (with a spectral resolution of 135).
Results: The globally-averaged stratospheric temperature structure is quasi-isothermal between 1-1000 μbar, which suggests little variation in global stratospheric conditions since studies by the Infrared Space Observatory a decade earlier. The derived CH4 mole fraction of (9.0 ± 3.0)× 10-4 at 50 mbar, decreasing to (0.9 ± 0.3)× 10-4 at 1 μbar, is larger than that expected if the tropopause at 56 K acts as an efficient cold trap, but consistent with the hypothesis that CH4 leaking through the warm south polar tropopause (62-66 K) is globally redistributed by stratospheric motion. The ratio of D/H in CH4 of 3.0 ± 1.0 × 10-4 supports the conclusion that Neptune is enriched in deuterium relative to the other giant planets. We determine a mole fraction of ethane of (8.5 ± 2.1)× 10-7 at 0.3 mbar, consistent with previous studies, and a mole fraction of ethylene of 5.0-2.1+1.8 × 10-7 at 2.8 μbar. An emission peak at 4.7 μm is interpreted as a fluorescent emission of CO, and requires a vertical distribution with both external and internal sources of CO. Finally, comparisons to previous L-band studies indicate significant variability of Neptune's flux densities in the 3.5-4.1 μm range, related to changes in solar energy deposition. Title: Using Active Contours for Semi-Automated Tracking of UV and EUV Solar Flare Ribbons Authors: Gill, C. D.; Fletcher, L.; Marshall, S. Bibcode: 2010SoPh..262..355G Altcode: 2010SoPh..tmp...20G Solar-flare UV and EUV images show elongated bright "ribbons" that move over time. If these ribbons are assumed to locate the footpoints of magnetic-field lines reconnecting in the corona, then it is clear that studying their evolution can provide important insight into the reconnection process. An image-processing method based on active contours (commonly referred to as "snakes") is proposed as a method for tracking UV and EUV flare ribbons and is tested on images from the Transition Region and Coronal Explorer (TRACE). This paper introduces the basic concepts of such an approach with a brief overview of the history and theory behind active contours. It then details the specifics of the snake algorithm developed for this work and shows the results of running the algorithm on test images. The results from the application of the developed algorithm are reported for six different TRACE flares (five in UV and one in EUV). The discussion of these results uses the output from an expert tracking the same ribbons by eye as a benchmark, and against these the snake algorithm is shown to compare favourably in certain conditions, but less so in others. The applicability of the automated snake algorithm to the general problem of ribbon tracking is discussed and suggestions for ways to improve the snake algorithm are proposed. Title: Possible liquid water origin for Atacama Desert mudflow and recent gully deposits on Mars Authors: Heldmann, J. L.; Conley, C. A.; Brown, A. J.; Fletcher, L.; Bishop, J. L.; McKay, C. P. Bibcode: 2010Icar..206..685H Altcode: Evidence of recent gully activity on Mars has been reported based on the formation of new light toned deposits within the past decade, the origin of which remains controversial. Analogous recent light toned gully features have formed by liquid water activity in the Atacama Desert on Earth. These terrestrial deposits leave no mineralogical trace of water activity but rather show an albedo difference due to particle size sorting within a fine-grained mudflow. Therefore, spectral differences indicating varying mineralogy between a recent gully deposit and the surrounding terrain may not be the most relevant criteria for detecting water flow in arid environments. Instead, variation in particle size between the deposit and surrounding terrain is a possible discriminator to identify a water-based flow. We show that the Atacama deposit is similar to the observed Mars gully deposits, and both are consistent with liquid water activity. The light-toned Mars gully deposits could have formed from dry debris flows, but a liquid water origin cannot be ruled out because not all liquid water flows leave hydrated minerals behind on the surface. Therefore, the Mars deposits could be remnant mudflows that formed on Mars within the last decade. Title: Silica Debris Star Systems — Spitzer Evidence for Lunar Formation Events & Crustal Stripping or Magma Oceans & Late Heavy Bombardments? Authors: Lisse, C. M.; Chen, C. H.; Wyatt, M. C.; Morlok, A.; Thebault, P.; Orton, G. S.; Fletcher, L. N.; Fujiwara, H.; Bridges, J. C.; Elkins-Tanton, L. T.; Gaidos, E. J.; Trang, D. Bibcode: 2010LPI....41.2390L Altcode: Recent work (Lisse et al., 2009) has detected amorphous silica and SiO gas around 12-m.y.-old HD172555, at the right age to form rocky planets. Here we discuss the location, lifetime, and source of the material, using inferences gleaned from HD172555 and three new silica systems. Title: The white-light continuum in the impulsive phase of a solar flare. Authors: Hudson, H. S.; Fletcher, L.; Krucker, S. Bibcode: 2010MmSAI..81..637H Altcode: 2010arXiv1001.1005H We discuss the IR/visible/VUV continuum emission of the impulsive phase of a solar flare, using TRACE UV and EUV images to characterize the spectral energy distribution. This continuum has been poorly observed but energetically dominates the radiant energy output . Recent bolometric observations of solar flares furthermore point to the impulsive phase as the source of a major fraction of the radiant energy. This component appears to exhibit a Balmer jump and thus must originate in an optically thin region above the quiet photosphere, with an elevated temperature and strong ionization. Title: The chromosphere during solar flares . Authors: Fletcher, L. Bibcode: 2010MmSAI..81..616F Altcode: 2010arXiv1001.0739F The emphasis of observational and theoretical flare studies in the last decade or two has been on the flare corona, and attention has shifted substantially away from the flare's chromospheric aspects. However, although the pre-flare energy is stored in the corona, the radiative flare is primarily a chromospheric phenomenon, and its chromospheric emission presents a wealth of diagnostics for the thermal and non-thermal components of the flare. I will here review the chromospheric signatures of flare energy release and the problems thrown up by the application of these diagnostics in the context of the standard flare model. I will present some ideas about the transport of energy to the chromosphere by other means, and calculations of the electron acceleration that one might expect in one such model. Title: Integrated Ly-alpha intensity emission in ribbon flares Authors: Rubio da Costa, F.; Fletcher, L.; Labrosse, N.; Zuccarello, F. Bibcode: 2010MSAIS..14..193R Altcode: We have analyzed two flares observed by TRACE in Ly alpha (on 8th September 1999 and 28th February 1999) in order to deduce their morphology, temporal evolution, radiative outputs and compare these results with data obtained in the X-range (SXT and HXT on Yohkoh) and with magnetograms (MDI/SOHO). These observational data and the results obtained by a theoretical study of the intensity of the radiation emitted by hydrogen lines, contribute to construct semi-empirical and theoretical models of the chromospheric emission during flares. Future observations by the planned Extreme Ultraviolet Imager selected for the Solar Orbiter mission -which will have a Lyman alpha channel- and this work, can help in designing observational flare studies. Title: Hubble Imaging of Jupiter after the 2009 Impact Authors: Hammel, Heidi B.; Clarke, J. T.; de Pater, I.; Fletcher, L. N.; Hueso, R.; Noll, K. S.; Orton, G. S.; Perez-Hoyos, S.; Sanchez-Lavega, A.; Simon-Miller, A. A.; Wong, M. H.; Yanamandra-Fisher, P. A. Bibcode: 2010AAS...21533407H Altcode: 2010BAAS...42..434H On 19 July 2009, amateur astronomer Anthony Wesley discovered an anomalous dark feature near Jupiter's south pole (planetographic latitude -58° system III west longitude 305°). Additional observations confirmed the new feature was an impact site created by an unknown object (the only other observed collision with Jupiter occurred 15 years earlier, when the shattered remains of Comet Shoemaker-Levy 9 created huge atmospheric disturbances). A world-wide observing campaign was initiated in response to this 2009 collision. We were awarded Directors Discretionary Time to use the newly-installed Wide-Field Camera 3 (WFC3) on Hubble Space Telescope. Observations were successfully obtained with WFC3 on July 23, August 3, and August 8, and with the Advanced Camera for Surveys' Solar Blind Channel in the UV on September 8. In this talk, we will present a summary of the HST images. The evolution of the impact debris field at UV, visible, near-IR wavelengths will be discussed, along with a comparison to Hubble observations of the Shoemaker-Levy 9 impact in 1994. Title: Elementary Energy Release Events in Flaring Loops: Effects of Chromospheric Evaporation on X-Rays Authors: Liu, Siming; Han, Feiran; Fletcher, Lyndsay Bibcode: 2010ApJ...709...58L Altcode: 2009arXiv0912.0402L With the elementary energy release events introduced in a previous paper, we model the chromospheric evaporation in flaring loops. The thick-target hard X-ray (HXR) emission produced by electrons escaping from the acceleration region dominates the impulsive phase, and the thin-target emission from the acceleration region dominates the low-energy thermal component in the gradual phase, as observed in early impulsive flares. Quantitative details depend on properties of the thermal background, which leads to variations in the correlation between HXR flux and spectral index. For lower temperature and/or higher density of the background electrons, the HXRs both rise and decay more quickly with a plateau near the peak. The plateau is less prominent at higher energies. Given the complexity of transport of mass, momentum, and energy along loops in the impulsive phase, we propose a strategy to apply this single-zone energy release and electron acceleration model to observations of flares associated with single loops so that the energy release, electron acceleration, and evaporation processes may be studied quantitatively. Title: Non-LTE analysis of Uranus Observations from Spitzer Authors: Zhang, X.; Martin-Torres, F.; Yung, Y. L.; Orton, G. S.; Fletcher, L. N. Bibcode: 2009AGUFM.P32C..01Z Altcode: Spitzer Infrared Spectrometer (IRS) observations of the disk of Uranus between 5.2 and 32 microns (1920 cm-1-270 cm-1) contain a wealth of information about the its cold atmosphere. In particular, they enable the retrieval of temperature and the abundances of several gaseous species as a function of pressure. They can also be used to study the energetics of radiatively active species in regions of Uranus’ atmosphere where Local Thermodynamic Equilibrium (LTE) is expected to break down. Care must be taken in atmospheric sounding not to assume that the atmospheric compounds emit according to the Planck function at the local kinetic temperature. Many of the ro-vibrational states of atmospheric constituents responsible for infrared emissions have excitation temperatures that differ from the local kinetic temperature. While non-LTE emission has been extensively considered for remote sensing of the Earth, only one study by Appleby (Icarus, 85, p355-379, 1990), who examined the radiative equilibrium temperatures of methane (CH4) in the upper atmospheres of Jupiter, Saturn, Uranus, and Neptune, has estimated the influence of non-LTE effects in Uranus' upper atmosphere. Uranus is composed mainly of hydrogen and helium. Helium is radiatively inactive, and hydrogen is active only in its weak collision-induced absorption, and its quadrupole lines. At low pressures, non-LTE processes involve the quantum levels of the more abundant minor constituents become important. In the case of Uranus the most important gas in the latter category is CH4, which has a role rather analogous to that of carbon dioxide in the Earth’s atmosphere. Since the work by Appleby, the spectroscopic and kinetics information of methane and other hydrocarbons has greatly improved and computer capabilities allow avoiding previous simplifications. For example, the full coupling between CH4 v4 and the higher-energy vibrational states emitting/absorbing in the near-IR is now possible. In this presentation we analyze the non-LTE effects in Spitzer data using a new non-local thermodynamic equilibrium radiative transfer for the infrared emissions of CH4, C2H2, and C2H6 which are observed in its spectrum. Title: HST Observations of the July 2009 Impact on Jupiter Authors: de Pater, I.; Hammel, H. B.; Simon-Miller, A. A.; Clarke, J. T.; Noll, K. S.; Orton, G. S.; Fletcher, L. N.; Yanamandra-Fisher, P. A.; Sanchez-Lavega, A.; Hueso, R.; Perez-Hoyos, S.; Wong, M. H. Bibcode: 2009AGUFM.P14D..01D Altcode: On UT 19 July 2009 amateur astronomer Anthony Wesley announced that Jupiter might have been hit by an object, as evidenced from an anomalous feature near Jupiter’s south pole (at a southern planetgraphic latitude of 58 deg, and W. longitude III of 305 deg). A world-wide observing campaign was initiated in response, including Hubble Space Telescope Director Discretionary Time on the newly-installed WFC3 camera. Observations were made on July 23, August 3 and 8. In this talk we will present a summary of the HST images at wavelengths between 400 and 900 nm. In particular, we will compare the initial HST observations with contemporaneous data over a wide spectral range from the near-IR (Keck) and mid-IR (Gemini-North, VLT, Gemini-South). The evolution of the impact debris field at visible, near- and mid-IR wavelengths will be discussed, along with a comparison to the Shoemaker-Levy 9 impact in 1994. Title: A Mission Concept Study of a Dilute Aperture Visible Nulling Coronagraph Imager (DAViNCI) for the Detection and Spectroscopy of Exo-planets Authors: Shao, Michael; Bairstow, S.; Deems, E.; Fletcher, L.; Levine, B.; Orton, G.; Vasisht, G.; Wayne, L.; Zhao, F.; Clampin, M.; Lyon, R.; Guyon, O.; Lane, B.; Havey, K.; Wynn, J.; Samuele, R.; Vasudevan, G.; Woodruff, R.; Tolls, V.; Malbet, F.; Leger, A. Bibcode: 2009AAS...21460603S Altcode: DAViNCI is a mission concept for the imaging and spectroscopy of exo-planets from nearby stars. It is capable of surveying and characterizing over 100 stars at an inner working angle of 35mas at its maximum baseline. DAViNCI is a 4 aperture telescope imaging system separated by a variable baseline whose light is combined interfermometrically into a nulling coronagraph instrument coupled to an imaging camera and spectrometer. We will describe the science potential and configuration of DAViNCI, its architecture, its instruments, and the results of mission and instrument studies in terms of capability and cost.

This work was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract to the National Aeronautics and Space Administration. Title: Mapping potential vorticity dynamics on saturn: Zonal mean circulation from Cassini and Voyager data Authors: Read, P. L.; Conrath, B. J.; Fletcher, L. N.; Gierasch, P. J.; Simon-Miller, A. A.; Zuchowski, L. C. Bibcode: 2009P&SS...57.1682R Altcode: Maps of Ertel potential vorticity on isentropic surfaces (IPV) and quasi-geostrophic potential vorticity (QGPV) are well established in dynamical meteorology as powerful sources of insight into dynamical processes involving 'balanced' flow (i.e. geostrophic or similar). Here we derive maps of zonal mean IPV and QGPV in Saturn's upper troposphere and lower stratosphere by making use of a combination of velocity measurements, derived from the combined tracking of cloud features in images from the Voyager and Cassini missions, and thermal measurements from the Cassini Composite Infrared Spectrometer (CIRS) instrument. IPV and QGPV are mapped and compared for the entire globe between latitudes 89∘S-82∘N. As on Jupiter, profiles of zonally averaged PV show evidence for a step-like "stair-case" pattern suggestive of local PV homogenisation, separated by strong PV gradients in association with eastward jets. The northward gradient of PV (IPV or QGPV) is found to change sign in several places in each hemisphere, however, even when baroclinic contributions are taken into account. The stability criterion with respect to Arnol'd's second stability theorem may be violated near the peaks of westward jets. Visible, near-IR and thermal-IR Cassini observations have shown that these regions exhibit many prominent, large-scale eddies and waves, e.g. including 'storm alley'. This suggests the possibility that at least some of these features originate from instabilities of the background zonal flow. Title: Thermal Evolution and Composition of the July 2009 Jupiter Impact Site from 7-25 Micron Imaging and Spectroscopy Authors: Fletcher, L. N.; Orton, G. S.; Mousis, O.; de Pater, I.; Hammel, H. B.; Golisch, W.; Edwards, M.; Yanamandra-Fisher, P. A.; Fisher, B.; Greene, Z.; Lai, S.; Otto, E.; Reshetnikov, N.; Sanchez-Lavega, A.; Simon-Miller, A. A.; Hueso, R.; Perez-Hoyos, S. Bibcode: 2009AGUFM.P14D..03F Altcode: We present analysis of thermal-infrared imaging and spectroscopy of the impact site near the south polar region of Jupiter (see Orton et al., AGU 2009). Enhanced thermal emission was first detected on July 20 2009 in 7-25 micron imaging from the MIRSI instrument on NASA’s IRTF. These observations, just two rotations after the impact, indicated the localised, high-temperature thermal signature of the ejecta field, coincident with the location of high-altitude particulate debris observed in the near-IR and visible. The impact feature was most visible in the 9-11 micron range, suggestive of enhanced emission from hydrocarbons and ammonia gas in the lower stratosphere. Subsequent thermal imaging of the impact region reveals the radiative cooling of the impact site and the changing morphology due to the redistribution of material by Jupiter’s zonal and meridional wind field. We acquired Gemini-N/Michelle imaging on July 22, Gemini-S/TReCS imaging on July 24 and August 5 and 9, and an extensive campaign of VLT/VISIR imaging on July 24, 26 and August 5, 10, 15, 16, at which point (4 weeks after the impact) the thermal signature could no longer be reliably distinguished, even with sub-arcsecond diffraction-limited angular resolution. Tropospheric and stratospheric temperatures and aerosol opacity are derived via optimal estimation retrievals (Fletcher et al. 2009, Icarus, 200, p154). Enhancement of hydrocarbons and gaseous ammonia are determined via iterative forward modelling, aided by spectral observations obtained with the slit aligned east-west through the impact feature from Gemini-S/TReCS (July 24) and VLT/VISIR (July 26, August 12-13). Low-resolution N-band (8-13 microns) Gemini-S/TReCS spectra confirm the enhanced emission over a broad range of wavelengths; Q-band (17-25 micron) spectra are used to study upper tropospheric temperatures in the aftermath of the collision and the rate of radiative cooling. VLT/VISIR spectra provide higher spectral resolutions in narrow wavelength ranges near 8.02, 10.49, 11.31, 11.60, 12.24 and 13.36 microns, sensitive to NH3, CH4 and hydrocarbon emission features. Iterative forward modelling of these spectra will be used to deduce the unique chemical composition and the three-dimensional thermal structure of the impact site, compared with the ‘unperturbed’ atmosphere at the same latitude. * Fletcher is supported by an appointment to the NASA Postdoctoral Program at the Jet Propulsion Laboratory/California Institute of Technology, administered by Oak Ridge Associated Universities through a contract with NASA. We wish to acknowledge the invaluable contributions of the support staff at IRTF, VLT and Gemini. Title: Hard X-ray emission from a flare-related jet Authors: Bain, H. M.; Fletcher, L. Bibcode: 2009A&A...508.1443B Altcode: Aims. We aim to understand the physical conditions in a jet event which occurred on the 22nd of August 2002, paying particular attention to evidence for non-thermal electrons in the jet material.
Methods: We investigate the flare impulsive phase using multiwavelength observations from the Transition Region and Coronal Explorer (TRACE) and the Reuven Ramaty High Energy Spectroscopic Imager (RHESSI) satellite missions, and the ground-based Nobeyama Radioheliograph (NoRH) and Radio Polarimeters (NoRP).
Results: We report what we believe to be the first observation of hard X-ray emission formed in a coronal jet. We present radio observations which confirm the presence of non-thermal electrons present in the jet at this time. The evolution of the event is best compared with the magnetic reconnection jet model in which emerging magnetic field interacts with the pre-existing coronal field. We calculate an apparent jet velocity of ~500 km s-1 which is consistent with model predictions for jet material accelerated by the J×B force resulting in a jet velocity of the order of the Alfvén speed (~100-1000 km s-1).
Title: Emitted Power of Saturn Based on Cassini/CIRS Observations Authors: Li, L.; Conrath, B. J.; Gierasch, P. J.; Achterberg, R. K.; Nixon, C. A.; Flasar, F. M.; Simon-Miller, A. A.; Fletcher, L. N.; Read, P. L.; Baines, K. H.; West, R. A.; Ingersoll, A. P.; Vasavada, A. R.; Orton, G. S. Bibcode: 2009AGUFM.P32C..03L Altcode: We are evaluating the energy balance of Saturn through Cassini observations, utilizing in particular CIRS observations from 7 to 500 micron and ISS/VIMS observations from 0.25 to 5.1 micron. The CIRS observations are utilized to compute the emitted power of Saturn between 2004 and 2009. Compared with the Voyagers' results, Cassini’s observations display significant variations in the global emitted power between the Voyager epoch (1979-1982) and the current Cassini time period (2004-2009). In addition, the meridional distribution of emitted power measured by Cassini shows that the emitted power is ~20% higher in the southern hemisphere than in the northern hemisphere. This is different from the Voyager results, which showed the two hemispheres to be roughly equal in emitted power. It is unclear whether the differences between the Voyager and Cassini epochs are due to the seasonal or inter-annual variations or both, but the time variations from 2004 to 2009 suggest that seasonal variations are at least part of the reason. The Cassini Equinox and Solstice Extended missions will continue to provide more knowledge of the seasonal/inter-annual variations of the emitted power. The computation of the reflected solar power by fitting Minnaert coefficient/Barkstrom model for each latitude bin or by directly utilizing the observed reflected radiance at each pixel of the globe is still in process. Combining the emitted power and the reflected solar power, we will estimate the energy balance of Saturn and its meridional distribution and seasonal/inter- annual variability. Title: Near-Infrared Spectroscopy and Imaging of the 2009 Jupiter impact debris field: Constraints on particle composition, size and vertical distribution Authors: Yanamandra-Fisher, P. A.; Orton, G. S.; Fletcher, L. N.; Fisher, B.; Greene, Z.; Otto, E.; Reshetnikov, N.; Golisch, W.; Lystrup, M. B.; Shara, M.; Moskovitz, N. A.; Trilling, D.; Reddy, V.; Rivkin, A.; Grundy, W. M.; Emery, J. P.; Kim, J.; Baines, K. H.; Griep, D.; Sears, P. Bibcode: 2009AGUFM.P31A1228Y Altcode: We present results of near-infrared imaging and spectroscopy of the 2009 Jupiter impact site and its associated debris field during the time period from 20 July 2009 (approximately 20 hours after impact) to 31 August 2009 (nearly six weeks post-impact). Our data were acquired with NASA/InfraRed Telescope Facility (IRTF) facility instruments, SpeX, 1- to 5-micron spectrometer and its guide camera, and NSFCam2, 1- to 5-micron multi-spectral camera. On 20 July, the impact site appeared as a localized region, close to and brighter than Jupiter's south polar haze. The impact site then expanded longitudinally in both directions. Nearly five weeks later, the debris field continues to spread, characterized by a few localized structures or cores near the original impact longitude, surrounded by material which is extended by about 7 degrees in latitude and 80 degrees in longitude. Early multi-spectral images and spectra of the debris identify ammonia as a constituent. Spectra and images of the debris material in subsequent weeks, redistributed by the zonal and meridional wind field of Jupiter, indicates the debris continues to be very prominent at 2 microns; comparable in reflectivity to the south polar haze and high in the atmosphere, implying small particles. The cores of the debris field were the only components of the neutral atmosphere detectable in the strong methane-absorbing 3.2- to 3.4-micron region as late as 6 August, but they were no longer detectable as of 18 August. In the 2-micron region, the debris reflectivity also diminished with time, mostly likely as a result of downward sedimentation. Our results will be compared to the those from SL9 fragment impacts and the "undisturbed" Jovian atmosphere, constraining the vertical distribution of the perturbation, composition and particle sizes of the debris. Title: Debris Field of the July 19, 2009, Impact in Jupiter and Its Long-term Evolution Authors: Orton, G. S.; Wesley, A.; Mousis, O.; Fletcher, L. N.; Yanamandra-Fisher, P. A.; Fisher, B.; Simon-Miller, A. A.; Greene, Z. S.; de Pater, I.; Hammel, H. B.; Reshetnikov, N.; Otto, E.; Lai, S.; Rogers, J.; Sanchez-Lavega, A.; Perez-Hoyos, S.; Hueso, R.; Golisch, W.; Griep, D.; Sears, P.; Lystrup, M. B.; Shara, M.; Young, L.; Grundy, W. M.; Moskovitz, N. A.; Rivkin, A. S.; Reddy, V.; Emery, J. P.; Trilling, D.; Ziffer, J. Bibcode: 2009AGUFM.P14D..04O Altcode: A multi-platform suite of imaging and spectroscopic observations of Jupiter's atmosphere tracked the evolution of the debris field of an unknown impactor on 2009 July 19. The initial debris field is similar to those of intermediate Shoemaker-Levy 9 fragments, suggesting a body hundreds of meters in size, if icy, entering from the west and slightly north. The field is detectable in the visible as dark material and in the near-IR by high-altitude particulate reflectivity; it was quickly redistributed by different zonal flows across its latitudinal range. At first, the particulate field was highly correlated with areas of enhanced temperatures and enhanced ammonia and ethane emission, but this was no longer true by mid-August. As of Sept. 2, the debris field was undetectable in the thermal, detectable in the visible with good seeing, and still prominent near 2 microns wavelength. Visibly, the impact "scar" consists of two dark regions along the same latitude, ostensibly different from the central bright region associated with the near-IR debris pattern. Both morphologies show eastern and western extensions propagating away from the original impact site, which appear to be influenced by flows around vortices previously undetected in Jupiter atmosphere. These observations define the flow field just north of Jupiter's southern polar vortex at higher altitudes than tracked in Jupiter's main cloud deck. Title: Thermal and Near-Infrared Structural Evolution of the 2009 Wesley Jupiter Impact from 1.5-24.5 Micron Imaging Authors: Greene, Z. S.; Orton, G. S.; Fletcher, L. N.; Yanamandra-Fisher, P. A.; Mousis, O.; Fisher, B.; Reshetnikov, N.; Lai, S.; Otto, E.; Hammel, H. B.; de Pater, I.; Edwards, M. Bibcode: 2009AGUFM.P33B1282G Altcode: We show the morphological evolution of the remnant scar from the Jupiter impact (July 19, 2009) at mid- and near-infrared wavelengths. Data taken less than 24 hours after the impact using NASA’s IRTF capture the initial structure at a wide range of wavelengths from 1.5-24.5 microns. Furthermore, images obtained from NASA’s Infrared Telescope Facility, Gemini North and South, and the Very Large Telescope in the subsequent weeks allow us to monitor the evolving morphology of the feature as zonal and meridional winds redistributed the impact debris through Jupiter’s atmosphere. Our observations indicate that the feature expanded primarily in the longitudinal direction in both the mid- and near-infrared, but underwent separation in the latitudinal direction much earlier in the thermal. The impact feature also became indistinguishable from its Jovian background in the thermal as of mid-August, whereas the scar remains distinct in the near-infrared. Timelines and images at various thermal and near-infrared wavelengths will be used to show the rapid evolution of the debris from July 20 to late August. *This work was performed at the Jet Propulsion Laboratory, California Institute of Technology, sponsored by the Summer Undergraduate Research Fellowship (SURF) program. Title: Modelling the Longitudinal Asymmetry in Sunspot Emergence: The Role of the Wilson Depression Authors: Watson, F.; Fletcher, L.; Dalla, S.; Marshall, S. Bibcode: 2009SoPh..260....5W Altcode: 2009arXiv0909.0914W The distributions of sunspot longitude at first appearance and at disappearance display an east-west asymmetry that results from a reduction in visibility as one moves from disk centre to the limb. To first order, this is explicable in terms of simple geometrical foreshortening. However, the centre-to-limb visibility variation is much larger than that predicted by foreshortening. Sunspot visibility is also known to be affected by the Wilson effect: the apparent `dish' shape of the sunspot photosphere caused by the temperature-dependent variation of the geometrical position of the τ=1 layer. In this article we investigate the role of the Wilson effect on the sunspot appearance distributions, deducing a mean depth for the umbral τ=1 layer of 500 - 1500 km. This is based on the comparison of observations of sunspot longitude distribution and Monte Carlo simulations of sunspot appearance using different models for spot growth rate, growth time and depth of Wilson depression. Title: Observations of a solar flare and filament eruption in Lyman α and X-rays Authors: Rubio da Costa, F.; Fletcher, L.; Labrosse, N.; Zuccarello, F. Bibcode: 2009A&A...507.1005R Altcode: 2009arXiv0909.4705R Context: Lα is a strong chromospheric emission line, which has been relatively rarely observed in flares. The Transition Region and Coronal Explorer (TRACE) has a broad “Lyman α” channel centered at 1216 Å used primarily at the beginning of the mission. A small number of flares were observed in this channel.
Aims: We aim to characterise the appearance and behaviour of a flare and filament ejection which occurred on 8th September 1999 and was observed by TRACE in Lα, as well as by the Yohkoh Soft and Hard X-ray telescopes. We explore the flare energetics and its spatial and temporal evolution. We have in mind the fact that the Lα line is a target for the Extreme Ultraviolet Imaging telescope (EUI) which has been selected for the Solar Orbiter mission, as well as the LYOT telescope on the proposed SMESE mission.
Methods: We use imaging data from the TRACE 1216 Å, 1600 Å and 171 Å channels, and the Yohkoh hard and soft X-ray telescopes. A correction is applied to the TRACE data to obtain a better estimate of the pure Lα signature. The Lα power is obtained from a knowledge of the TRACE response function, and the flare electron energy budget is estimated by interpreting Yohkoh/HXT emission in the context of the collisional thick target model.
Results: We find that the Lα flare is characterised by strong, compact footpoints (smaller than the UV ribbons) which correlate well with HXR footpoints. The Lα power radiated by the flare footpoints can be estimated, and is found to be on the order of 1026 erg s-1 at the peak. This is less than 10% of the power inferred for the electrons which generate the co-spatial HXR emission, and can thus readily be provided by them. The early stages of the filament eruption that accompany the flare are also visible, and show a diffuse, roughly circular spreading sheet-like morphology, with embedded denser blobs.
Conclusions: On the basis of this observation, we conclude that flare and filament observations in the Lα line with the planned EUI and LYOT telescopes will provide valuable insight into solar flare evolution and energetics, especially when accompanied by HXR imaging and spectroscopy. Title: Infrared and Microwave Observations of Uranus: Implications for Temperature, Composition, Circulation and a Standard Calibration Model for Herschel Authors: Hofstadter, Mark D.; Orton, G.; Fletcher, L.; Mainzer, A.; Merlet, C.; Hines, D.; Hammel, H.; Burgdorf, M.; Moses, J.; Butler, B.; Gurwell, M. Bibcode: 2009DPS....41.2803H Altcode: The Spitzer Infrared Spectrometer observed Uranus in December 2007 between 5 and 21.5 microns. Disk-averaged temperatures are retrieved between 2 bars and the microbar level, yielding a profile warmer than found by Voyager 2. A substantial rise in temperature near 8 microbars is also found - consistent with Voyager results. The methane mixing ratio, constrained by 7-micron emission, is between 5% and 60% of saturation at the Tropopause. The presence of both absorption and emission by CH4 and CH3D will allow us to constrain the D/H ratio and the mixing ratio of methane in the 2-bar region. The abundance of stratospheric hydrocarbons varies strongly with longitude, while temperature does not. Minimal longitudinal and latitudinal variability of tropospheric temperatures indicates that Uranus may be adequate as a calibration source in the far-infrared through the submillimeter, which is useful to the Herschel Space Telescope. Strong latitudinal gradients in composition, however, as revealed by imaging at 1 mm to 20 cm, do need to be accounted for. The Submillimeter Array imaged Uranus in 2006 at 1.4 mm, and the Very Large Array imaged Uranus between 2005 and 2009 at wavelengths from 7 mm to 20 cm. These data indicate there is a latitudinally varying abundance of a microwave absorber near the 1-bar level, with H2S being a likely candidate. The disk-averaged IR data confirms the presence of an opacity source besides that of H2 in this altitude region. The VLA data also imply an unexpected vertical distribution of opacity at pressures of tens-of-bars in the equatorial region, believed to be related to the liquid-water cloud. Much of this work was carried out at JPL/Caltech, under contract with NASA. We acknowledge the support of NASA's Planetary Astronomy and Atmospheres programs, and the Spitzer, SMA, VLA, and VLT observatories. Title: First Observations of the 2009 Collision in Jupiter's Atmosphere Authors: Orton, Glenn S.; Fletcher, L.; Wesley, A.; Yanamandra-Fisher, P.; Fisher, B.; Mousis, O.; Golisch, W.; de Pater, I.; Marchis, F.; Kalas, P.; Fitzgerald, M.; Graham, J.; Wong, M.; Rogers, J.; Momary, T.; Sanchez-Lavega, A.; Hammel, H.; Simon-Miller, A. Bibcode: 2009DPS....41.1001O Altcode: We report initial observations of the debris from the first documented impact of a body with Jupiter since the collisions of Comet Shoemaker-Levy 9 fragments 15 years ago. Visible observations by AW at 14:01 UT on 2009 July 19 recorded an unusual blackened region with fainter ejecta near the edge of Jupiter's South Polar Region. 0.89-micron CH4 band imaging (A. Cidadao, D. Peach) on the subsequent rotation showed this site to be bright. Two rotations later at NASA's IRTF, a series of near-IR (1.58-4.78 micron) images with SpeX and NSFCam2 were recorded which verified the unmistakable signature of high-altitude particulate debris in even stronger CH4 and H2 absorption. Spectra were also recorded in the 0.8-2.5 micron region. Images of thermal emission between 7 and 25 microns with MIRSI instrument recorded enhanced emission associated with ammonia gas and an increase of temperatures in the upper troposphere at the site of the impact and debris field. No enhancement of temperatures was detected near the 10-mbar level of the stratosphere. During the same rotation, Keck-II NIRC2 images at 2.124 microns detected an impact site, centered at 305±1.5°W longitude and 57±1.5°S planetographic latitude, with two prominent features and an ejecta field annulus which extends toward the west by 10° in longitude. The distinct detail of the initial images and references to existing images suggest that the impact may have occurred within a 10-hour period before its initial detection in the visible. Comparisons with published analyses of the Shoemaker-Levy 9 impacts suggest an impactor on the order of hundreds of meters in size, something unlikely to have been detected in advance. There is no evidence at any wavelength for additional impacts. As of this writing, a vigorous campaign to characterize the impact site is being mounted at several observatories, and more details will inevitably follow. Title: The Case for Uranus and Neptune Authors: Hofstadter, Mark D.; Sotin, C.; Brooks, S.; Fletcher, L.; Friedson, A.; Moeller, R.; Murphy, N.; Orton, G.; Spilker, T.; Wenkert, D. Bibcode: 2009DPS....41.1606H Altcode: Uranus and Neptune are composed mostly of ices, such as H2O, making them fundamentally different from Jupiter or Saturn. These ice giants, and their unique satellites and rings, have an important story to tell us about the formation, evolution, and structure of planets in our Solar System and beyond. To understand that story, we must learn the basic properties of their interiors. We do not know if they have extensive solid- or liquid-water layers (making them almost overgrown icy satellites) or if the H2O-H2 phase diagram allows structures unlike any other planet in our solar system. How internal heat is transported through the interior and atmosphere is also important to learn. We wish to know the nature of atmospheric convection and circulation and how they relate to internal and solar forcing. We also wish to know the composition and temperature of the atmosphere as a function of latitude, altitude, and time. One of the great surprises of the Voyager encounters was the discovery of strongly tilted dipole magnetic fields, offset from the planet's centers. How and where is the field generated? How does its unique geometry affect the transfer of energy from the solar wind to the magnetosphere? A mission to Uranus or Neptune, supported by healthy ground-based observing and laboratory campaigns, should be a priority for the next decade. Either planet can serve as the archetypal ice giant, but cross-disciplinary priorities can be used to choose one over the other. A recent JPL study identified trajectories that could deliver significant science payloads into orbit around either planet, and found that it may be possible to do so at Uranus for under the New Frontiers cost cap and using solar-power. This research was carried out at JPL/Caltech under contract with NASA. Title: Saturn Atmospheric Science in the Next Decade Authors: Orton, Glenn S.; Fletcher, L.; Stallard, T.; Baines, K.; Sayanagi, K.; Huestis, D.; Yung, Y.; Edgington, S.; Gulkis, S.; Moses, J.; Martin-Torres, F. Bibcode: 2009DPS....41.1603O Altcode: Although observed from the Earth, Pioneer 11, Voyagers 1 and 2, and now Cassini in its primary and 2-year extended mission, the characterization of fundamental atmospheric properties and processes in Saturn remains incomplete. Many open questions about the atmosphere could be addressed in the next decade:

- SEASONS: How do seasons affect (a) the global distribution of gaseous constituents and aerosols; and (b) temperatures and the stability against convection and large scale-atmospheric transport? Will a warm polar vortex appear at the northern pole with greater radiative input?

- HEXAGON: What is the vertical structure of the hexagon, what is driving and maintaining it; and why is there no feature of similar longevity at the south pole?

- COMPOSITION AND CHEMISRY: What are the noble gas and oxygen abundances? What is the relation of stratospheric hydrocarbon distributions to radiative climate influences and photochemistry? What is the rate of influx of ring and other exogenic materials into the atmosphere?

- CLOUDS AND HAZES: What is the tropospheric cloud inventory, and what are the different cloud compositions and optical properties? What is producing the haze material? What is the relation between observable clouds and lightning discharges? What is the relation between the fine-scale cloud structure identified at 5 microns and the

distribution of condensates, such as ammonia? Do 5-micron clouds have counterparts at other altitude levels?

- DYNAMICS: What is the source of the strong equatorial upwelling and strong prograde jet? What changes when we see the emergence of Great White Storms? How is energy transported by waves between atmospheric levels, via the SAO and by vertical waves observed in stellar occultations and RSS profiles? What effect does the ephemeral nature of Saturn's slowly-moving thermal waves have on the atmosphere? Will the tropospheric hotspots at each pole persist? Title: Meridional Distributions of Methylacetylene and Diacetylene in Saturn's Stratosphere from CIRS/Cassini Observations. Authors: Guerlet, Sandrine; Fouchet, T.; Moses, J. I.; Fletcher, L. N.; Bézard, B.; Simon-Miller, A. A.; Flasar, F. M. Bibcode: 2009DPS....41.2804G Altcode: The Composite InfraRed Spectrometer (CIRS) aboard the Cassini spacecraft provides a unique opportunity to perform limb observations of Saturn's stratosphere. This viewing geometry favors the detection of minor species and allows the retrieval of their abundance profile with a larger vertical extent and higher vertical resolution than nadir observations.

Following our work on acetylene, ethane and propane (Guerlet et al. 2009), we will present the first maps of the volume mixing ratio of methylacetylene (CH3C2H) and diacetylene (C4H2), from 45°N to 80°S and 3 mbar to 0.05 mbar. These results were obtained from an analysis of CIRS limb observations using a line-by-line radiative transfer model coupled to an inversion algorithm. We have also analyzed sets of nadir CIRS spectra, which are sensitive to C4H2 around 0.5 mbar, extending the meridional coverage up to 88°S and 65°N at this pressure level.

These molecules are minor by-products of the methane photochemistry, but their abundances give important insights on the main chemical pathways, as we will show their distributions compare with our previously derived C2H2 variations. C4H2 and CH3C2H have also rather short lifetimes (25-80 years at 1 mbar) compared to the main hydrocarbons' lifetimes (ethane and acetylene, resp. 700 and 100 years at 1 mbar) making them good tracers of seasonal stratospheric dynamics. They display some small-scale variations in their meridional distribution which could be symptomatic of vertical and/or meridional dynamics. We will compare the distribution of C3H4 and C4H2 we derived with the predictions of the photochemical seasonal model of Julie Moses (Moses and Greathouse, 2005). Title: Changing Seasons on Saturn: If Winter's Here, Can Spring be Far Behind? Authors: Yanamandra-Fisher, Padma A.; Orton, G. S.; Fisher, B. M.; Baines, K.; Fletcher, L.; Fujiyoshi, T.; Fuse, T. Bibcode: 2009DPS....41.2805Y Altcode: Ground-based near- and mid-infrared observations of Saturn from 1995 - 2009, covering half a Saturnian year, provide a rich data set to model seasonal changes in both Saturn's atmosphere and its rings as a function of solar elevation. We acquired near-infrared data from NASA/Infrared Telescope Facility (IRTF); and mid-infrared data from NASA/IRTF and NAOJ/Subaru Facility. Our data set covers the period from autumnal equinox (1995) to the upcoming vernal equinox (2009); and provides a bridge between Voyager encounters and Cassini prime mission, with temporal and spatial context for spacecraft observations. We shall present results illustrating: (1) changes in thermal fields on the planet; (2) evolution/distribution of various chemical species; (3) development of clouds and other discrete features; (4) thermal properties of the main rings and (5) models for these trends. Title: Unsteady signatures from solar flares: reconnection, acceleration or transport? Authors: Fletcher, Lyndsay; Liu, Siming Bibcode: 2009shin.confE.195F Altcode: The energy for solar flares is liberated from coronal stored energy via the process of reconnection. Observationally, solar flares are inherently bursty, in time and in space. The primary signatures of flare energy release are produced by accelerated electrons and ions, i.e. hard X-rays and gamma-rays, and radio. White light and ultraviolet chromospheric emission are also closely related to the primary energy release. All of these signatures demonstrate intermittency, on timescales from tens of milliseconds up to some tens of seconds. However, it is not clear from the outset how much of this intermittency is due to the energy release process, how much to the acceleration process, and how much to the energy transport process. I will review the flare main observations and discuss what each observable timescale might tell us about the basic processes associated with flare energisation. Title: Elementary Energy Release Events in Solar Flares Authors: Liu, Siming; Fletcher, Lyndsay Bibcode: 2009ApJ...701L..34L Altcode: 2009arXiv0907.1874L Most theoretical investigations of particle acceleration during solar flares cannot be applied to observations for detailed study of the time evolution. We propose a phenomenological model for turbulence evolution and stochastic particle acceleration that links observations to the energy release and particle acceleration through two coefficients characterizing particle interactions with turbulent electromagnetic fields. In the linear regime the particle distribution does not affect the turbulence energy cascade. It is shown that electron acceleration critically depends on the intensity of small-scale turbulence and an impulsive nonthermal component only appears near the peak of the gradually evolving turbulence intensity. The model naturally reproduces the soft-hard-soft pattern of hard X-ray pulses, and we attribute the observed change in flux and spectral index correlation from the rise to decay phase of some pulses to changes in the background plasma. Detailed modeling of well observed individual events will probe the energy release processes. Title: Phosphine on Jupiter and Saturn from Cassini/CIRS Authors: Fletcher, L. N.; Orton, G. S.; Teanby, N. A.; Irwin, P. G. J. Bibcode: 2009Icar..202..543F Altcode: The global distribution of phosphine (PH 3) on Jupiter and Saturn is derived using 2.5 cm -1 spectral resolution Cassini/CIRS observations. We extend the preliminary PH 3 analyses on the gas giants [Irwin, P.G.J., and 6 colleagues, 2004. Icarus 172, 37-49; Fletcher, L.N., and 9 colleagues, 2007a. Icarus 188, 72-88] by (a) incorporating a wider range of Cassini/CIRS datasets and by considering a broader spectral range; (b) direct incorporation of thermal infrared opacities due to tropospheric aerosols and (c) using a common retrieval algorithm and spectroscopic line database to allow direct comparison between these two gas giants. The results suggest striking similarities between the tropospheric dynamics in the 100-1000 mbar regions of the giant planets: both demonstrate enhanced PH 3 at the equator, depletion over neighbouring equatorial belts and mid-latitude belt/zone structures. Saturn's polar PH 3 shows depletion within the hot cyclonic polar vortices. Jovian aerosol distributions are consistent with previous independent studies, and on Saturn we demonstrate that CIRS spectra are most consistent with a haze in the 100-400 mbar range with a mean optical depth of 0.1 at 10 μm. Unlike Jupiter, Saturn's tropospheric haze shows a hemispherical asymmetry, being more opaque in the southern summer hemisphere than in the north. Thermal-IR haze opacity is not enhanced at Saturn's equator as it is on Jupiter. Small-scale perturbations to the mean PH 3 abundance are discussed both in terms of a model of meridional overturning and parameterisation as eddy mixing. The large-scale structure of the PH 3 distributions is likely to be related to changes in the photochemical lifetimes and the shielding due to aerosol opacities. On Saturn, the enhanced summer opacity results in shielding and extended photochemical lifetimes for PH 3, permitting elevated PH 3 levels over Saturn's summer hemisphere. Title: Signatures of spatially extended reconnection in solar flares Authors: Fletcher, Lyndsay Bibcode: 2009shin.confE.162F Altcode: Solar flare ribbons, visible in H alpha and ultraviolet, suggest strongly that flare reconnection happens not just in one or two spots in the corona but over an extended region. X-ray and white light footpoints on the other hand usually only occur in a couple of locations. What can we say about the spatial extent and distribution of coronal reconnection sites from such observations? In this talk I will discuss some recent observations and simulations of 3D reconnection, and whether they together provide evidence for large-scale (i.e. active-region scale) current sheets. Title: Jupiter Authors: Marchis, F.; Hueso Alonso, R.; Mousis, O.; Orton, G.; Fletcher, L.; Perez-Hoyos, S.; Keck, W. M., II Bibcode: 2009IAUC.9060....3M Altcode: 2009IAUC.9060C...1M F. Marchis, University of California at Berkeley and SETI Institute; and R. Hueso Alonso, University of the Basque Country, further report on a preliminary analysis of observations of Jupiter's atmosphere collected by O. Mousis, Observatoire de Besancon; G. Orton and L. Fletcher, Jet Propulsion Laboratory; and S. Perez-Hoyos, University of the Basque Country, recorded with the Very Large Telescope (Yepun) and its adaptive-optics system NACO during July 26.311-26.370. Images taken with the IB248 filter (centered at 2.48 microns; width 0.06 microns) revealed that the feature located between 295 deg and 315 deg west longitude (in System III) and centered at 55 deg south latitude has a significantly evolved shape by comparison with the Keck telescope K_p (2.12 microns) data taken on July 20.468 (noted above). Six days after this observation, the two maxima are now barely distinguishable, separated by 8 deg in latitude. The brightest peak is centered at 312 deg west. The continued longitudinal shearing is consistent with several amateur observations of the site and with the behavior of the impact sites associated with the impacts of D/1993 F2 in 1994. Title: Observations of conduction driven evaporation in the early rise phase of solar flares Authors: Battaglia, M.; Fletcher, L.; Benz, A. O. Bibcode: 2009A&A...498..891B Altcode: 2009arXiv0903.2754B Context: The classical flare picture features a beam of electrons, which were accelerated in a site in the corona, hitting the chromosphere. The electrons are stopped in the dense chromospheric plasma, emitting bremsstrahlung in hard X-rays. The ambient material is heated by the deposited energy and expands into the magnetic flare loops, a process termed chromospheric evaporation. In this view hard X-ray emission from the chromosphere is succeeded by soft-X-ray emission from the hot plasma in the flare loop, the soft X-ray emission being a direct consequence of the impact of the non-thermal particle beam. However, observations of events exist in which a pronounced increase in soft X-ray emission is observed minutes before the onset of the hard X-ray emission. Such pre-flare emission clearly contradicts the classical flare picture.
Aims: For the first time, the pre-flare phase of such solar flares is studied in detail. The aim is to understand the early rise phase of these events. We want to explain the time evolution of the observed emission by means of alternative energy transport mechanisms such as heat conduction.
Methods: RHESSI events displaying pronounced pre-flare emission were analyzed in imaging and spectroscopy. The time evolution of images and full sun spectra was investigated and compared to the theoretical expectations from conduction driven chromospheric evaporation.
Results: The pre-flare phase is characterized by purely thermal emission from a coronal source with increasing emission measure and density. After this earliest phase, a small non-thermal tail to higher energies appears in the spectra, becoming more and more pronounced. However, images still only display one X-ray source, implying that this non-thermal emission is coronal. The increase of emission measure and density indicates that material is added to the coronal region. The most plausible origin is evaporated material from the chromosphere. Energy provided by a heat flux is capable of driving chromospheric evaporation. We show that the often used classical Spitzer treatment of the conductive flux is not applicable. The conductive flux is saturated. During the preflare-phase, the temperature of the coronal source remains constant or increases. Continuous heating in the corona is necessary to explain this observation.
Conclusions: The observations of the pre-flare phase of four solar flares are consistent with chromospheric evaporation driven by a saturated heat flux. Additionally, continuous heating in the corona is necessary to sustain the observed temperature. Title: Hard X-ray Emission From A Flare-related Jet Authors: Bain, Hazel; Fletcher, L. Bibcode: 2009SPD....40.3606B Altcode: Solar X-ray jets were first observed by Yohkoh (Shibata 1992, Strong 1992). During these events, collimated flows of plasma are accelerated in the corona. Previous observations have detected jet-related electrons directly in space as well as via radio signatures (type III bursts). However the major diagnostic of fast electrons is bremsstrahlung X-ray emission, but until now we have never seen any evidence of hard X-ray emission directly from the jet in the corona. This could be because it is rare to find a coronal jet dense enough to provide a bremsstrahlung target for the electrons, or hot enough to generate high energy thermal emission. We report what we believe to be the first observation of hard X-ray emission formed in a coronal jet. The event occurred on the 22nd of August 2002 and its evolution was observed by a number of instruments. In particular we study the pre-impulsive and impulsive phase of the flare using data from RHESSI, TRACE and the Nobeyama Radioheliograph. During this period RHESSI observed significant hard X-ray emission to energies as high as 50 keV in the jet. Radio observations from the Nobeyama Radioheliograph show a positive spectral index for the ejected material, which may be explained by optically-thick gyrosynchrotron emission from non-thermal electrons in the jet.

HMB gratefully acknowledges the support of an SPD and STFC studentship. LF gratefully acknowledges the support of an STFC Rolling Grant, and financial support by the European Commission through the SOLAIRE Network (MTRN-CT_2006-035484) Title: Flares and the chromosphere Authors: Hudson, Hugh S.; Fletcher, Lyndsay Bibcode: 2009EP&S...61..577H Altcode: 2009EP&S...61L.577H The chromosphere (the link between the photosphere and the corona) plays a crucial role in flare and CME development. In analogies between flares and magnetic substorms, it is normally identified with the ionosphere, but we argue that the correspondence is not exact. Much of the important physics of this interesting region remains to be explored. We discuss chromospheric flares in the context of recent observations of white-light flares and hard X-rays as observed by TRACE and RHESSI, respectively. We interpret key features of these observations as results of the stepwise changes a flare produces in the photospheric magnetic field. Title: A ``perfect'' Late Phase Flare Loop: X-ray And Radio Studies Authors: Bain, Hazel; Fletcher, L. Bibcode: 2009SPD....40.1917B Altcode: We present observations of a GOES X3.1 class flare which occurred on the 24th August 2002. The event was observed by a number of instruments including RHESSI, TRACE and NoRH. This flare is particularly interesting due to its position and orientation on the west limb of the Sun. The flare appears to be perpendicular to the line of sight making it possible to ascertain the geometrical parameters of the post flare arcade loops. We investigate the decay phase of the flare by comparing X-ray and radio observations of the post flare arcade loops with models of soft x-ray and thermal gyrosynchrotron emission to characterise the electron distribution present within the loop.

HMB gratefully acknowledges the support of an SPD and STFC studentship. LF gratefully acknowledges the support of an STFC Rolling Grant, and financial support by the European Commission through the SOLAIRE Network (MTRN-CT_2006-035484) Title: Change of Seasons on Jovian Planets: Ground-based High Spatial Thermal Observations Authors: Yanamandra-Fisher, Padma A.; Orton, G.; Fletcher, L. N.; Fisher, B. M.; Fujiyoshi, T.; Fuse, T.; Hayward, T.; de Buizer, J. Bibcode: 2009AAS...21430504Y Altcode: We report on the seasonal changes observed on all four of the solar system jovian planets, based on mid-infrared data acquired from several observatories (NASA/IRTF, NAOJ/Subaru, ESO/VLT) from 2005 to present. Jupiter's atmosphere underwent a global upheaval, from color transformation of discrete and axisymmetric features to interaction of giant vortices; Saturn is approaching its vernal equinox in August 2009 and its cold northern hemisphere is emerging into sunlight after years of obscuration; Saturn rings are closing towards their edge-on apparition; Uranus underwent its equinox in 2007, where seasons last 20 years and its north pole is warming up; and Neptune demonstrated a warm south pole, with a possible mechanism for escape of methane into the stratosphere. Although each planet is at a different stage of its seasonal cycle, taken together, our observations illustrate several overarching science investigations of the local meteorology on Jovian planets: What are the circulation patterns? What explains the warm south poles? What are the variations in the distribution of key chemical species such as ammonia, phosphine, and other hydrocarbons? Title: Evolution of an eruptive flare loop system Authors: Romano, P.; Zuccarello, F.; Fletcher, L.; Rubio da Costa, F.; Bain, H. M.; Contarino, L. Bibcode: 2009A&A...498..901R Altcode: Context: Flares, eruptive prominences and coronal mass ejections are phenomena where magnetic reconnection plays an important role. However, the location and the rate of the reconnection, as well as the mechanisms of particle interaction with ambient and chromospheric plasma are still unclear.
Aims: In order to contribute to the comprehension of the above mentioned processes we studied the evolution of the eruptive flare loop system in an active region where a flare, a prominence eruption and a CME occurred on August 24, 2002.
Methods: We measured the rate of expansion of the flare loop arcade using TRACE 195 Å images and determined the rising velocity and the evolution of the low and high energy hard X-ray sources using RHESSI data. We also fitted HXR spectra and considered the radio emission at 17 and 34 GHZ.
Results: We observed that the top of the eruptive flare loop system initially rises with a linear behavior and then, after 120 mn from the start of the event registered by GOES at 1-8 Å, it slows down. We also observed that the heating source (low energy X-ray) rises faster than the top of the loops at 195 Å and that the high energy X-ray emission (30-40 keV) changes in time, changing from footpoint emission at the very onset of the flare to being coincident during the flare peak with the whole flare loop arcade.
Conclusions: The evolution of the loop system and of the X-ray sources allowed us to interpret this event in the framework of the Lin & Forbes model (2000), where the absolute rate of reconnection decreases when the current sheet is located at an altitude where the Alfvén speed decreases with height. We estimated that the lower limit for the altitude of the current sheet is 6 × 104 km. Moreover, we interpreted the unusual variation of the high energy HXR emission as a manifestation of the non thermal coronal thick-target process which appears during the flare in a manner consistent with the inferred increase in coronal column density. Title: Saturn's north polar region at depth: The North Polar Hexagon and North Polar Cyclone observed over two years by Cassini/VIMS Authors: Baines, K. H.; Momary, T. W.; Fletcher, L. N.; Kim, J. H.; Showman, A. P.; Atreya, S. K.; Brown, R. H.; Buratti, B. J.; Clark, R. N.; Nicholson, P. D. Bibcode: 2009EGUGA..11.3375B Altcode: For over two years beginning in October, 2006, Saturn's north polar region has been observed periodically from clear vantage points over high northern latitudes by the Visual Infrared Mapping Spectrometer onboard the Cassini/Huygens orbiter, The latest observations, acquired on June 15 and December 16, 2008, are especially clear, as they were obtained from sub-spacecraft latitudes poleward of 70 degrees N and at close range (< 450,000 altitude for June; < 510,000 for December). With much of the polar region under nighttime conditions, we used Saturn's thermal glow as a source of light to map clouds in silhouette, monitoring their movement with time to determine the polar wind structure. We find a cyclone at the north pole, with winds exceeding 135 m/s near 88.3 degrees N. latitude (planetocentric, pc). The center of the cyclone, at the exact pole, is covered by a small (< 500 km in diameter) cloud. Equatorward, winds fall off to ~10 m/s near the poleward edge of the hexagon near 78 degrees pc. Within the hexagon itself, clouds move at ~ 125 m/s. The hexagon itself stays nearly fixed in the rotational system of Saturn established by Voyager. However, while the hexagonal feature stayed fixed to high accuracy from late 2006 through early 2008 (<0.5 deg of movement over 16 months), we find that since February, 2008, the hexagon has rotated 8.9 degrees in longitude in the retrograde direction. Between the detailed June and December 2008 observations, the feature rotated 1.2 degrees, retrograde, corresponding to 0.0065 degree/day or 2 cm/s, retrograde. Beginning in June, 2008, sunlight is seen reaching cloud features within the hexagon as polar winter wanes. New results of cloudtop altitude are presented based on the reflected sunlight observed in various methane and hydrogen atmospheric absorption bands. These are compared to the cloud bottom pressures which we have determined to be near the 2-bar level based on analysis of 5-micron thermal spectra. Clouds observed in sunlight and at 5-micron are coherent, indicating little vertical shear in zonal winds in the north polar region. Title: Problems and Solutions in the Analysis of Spitzer IRS Observations of Uranus and Neptune: Results for Temperature Structure and Composition Authors: Orton, G.; Fletcher, L.; Mainzer, A.; Line, M.; Merlet, C.; Hines, D.; Hammel, H.; Burgdorf, M.; Moses, J. Bibcode: 2009EGUGA..11.3525O Altcode: Mid-infrared spectra of the disks of Uranus and Neptune were obtained with Spitzer's very sensitive Infrared Spectrometer (IRS). The IRS covered the wavelength range of 5 to 21.5 μm with a resolving power of ~90 and of 10 to 36.5 μm with a resolving power of ~600, although there were problems with the high-resolution modes at the longest wavelengths. The spectra do not resolve the disks of either planet, but they are nonetheless replete with information about the global-mean temperature structure and composition of both planets. This presentation will concentrate on the approaches used to derive temperatures and compositions. Derivation of an average temperature profile will be demonstrated principally using spectra of Uranus, using the collision-induced absorption "continuum" and quadrupole lines of molecular hydrogen. Derivation of composition will be demonstrated princially using spectra of Neptune, covering features arising from methyl, methane, acetylene, ethyene, ethane, diacetylene, methylacetylene, and carbon dioxide. The benefits of recent improvements in spectroscopic parameters will be demonstrated, and the need for improvements in others outlined. Title: Partially-erupting prominences: a comparison between observations and model-predicted observables Authors: Tripathi, D.; Gibson, S. E.; Qiu, J.; Fletcher, L.; Liu, R.; Gilbert, H.; Mason, H. E. Bibcode: 2009A&A...498..295T Altcode: 2009arXiv0902.1228T Aims: We investigate several partially-erupting prominences to study their relationship with other CME-associated phenomena and compare these observations with observables predicted by a model of partially-expelled-flux-ropes (Gibson & Fan 2006a, ApJ, 637, L65; 2006b, J. Geophys. Res., 111, 12103).
Methods: We studied 6 selected events with partially-erupting prominences using multi-wavelength observations recorded by the Extreme-ultraviolet Imaging Telescope (EIT), Transition Region and Coronal Explorer (TRACE), Mauna Loa Solar Observatory (MLSO), Big Bear Solar Observatory (BBSO), and Soft X-ray Telescope (SXT). The observational features associated with partially-erupting prominences were then compared with the predicted observables from the model.
Results: The partially-expelled-flux-rope (PEFR) model can explain the partial eruption of these prominences, and in addition predicts a variety of other CME-related observables that provide evidence of internal reconnection during eruption. We find that all of the partially-erupting prominences studied in this paper exhibit indirect evidence of internal reconnection. Moreover, all cases showed evidence of at least one observable unique to the PEFR model, e.g., dimmings external to the source region and/or a soft X-ray cusp overlying a reformed sigmoid.
Conclusions: The PEFR model provides a plausible mechanism to explain the observed evolution of partially-erupting-prominence-associated CMEs in our study. Title: Energy Release and Transfer in Solar Flares: Simulations of Three-Dimensional Reconnection Authors: Birn, J.; Fletcher, L.; Hesse, M.; Neukirch, T. Bibcode: 2009ApJ...695.1151B Altcode: Using three-dimensional magnetohydrodynamic simulations we investigate energy release and transfer in a three-dimensional extension of the standard two-ribbon flare picture. In this scenario, reconnection is initiated in a thin current sheet (suggested to form below a departing coronal mass ejection) above a bipolar magnetic field. Two cases are contrasted: an initially force-free current sheet (low beta) and a finite-pressure current sheet (high beta), where beta represents the ratio between gas (plasma) and magnetic pressure. The energy conversion process from reconnection consists of incoming Poynting flux turned into up- and downgoing Poynting flux, enthalpy flux, and bulk kinetic energy flux. In the low-beta case, the outgoing Poynting flux is the dominant contribution, whereas the outgoing enthalpy flux dominates in the high-beta case. The bulk kinetic energy flux is only a minor contribution in the downward direction. The dominance of the downgoing Poynting flux in the low-beta case is consistent with an alternative to the thick target electron beam model for solar flare energy transport, suggested recently by Fletcher & Hudson, whereas the enthalpy flux may act as an alternative transport mechanism. For plausible characteristic parameters of the reconnecting field configuration, we obtain energy release timescales and energy output rates that compare favorably with those inferred from observations for the impulsive phase of flares. Significant enthalpy flux and heating are found even in the initially force-free case with very small background beta, resulting mostly from adiabatic compression rather than Ohmic dissipation. The energy conversion mechanism is most easily understood as a two-step process (although the two steps may occur essentially simultaneously): the first step is the acceleration of the plasma by Lorentz forces in layers akin to the slow shocks in the Petschek reconnection model, involving the conversion of magnetic energy to bulk kinetic energy. However, due to pressure gradient forces that oppose the Lorentz forces in approximate, or partial force balance, the accelerated plasma becomes slowed down and compressed, whereby the bulk kinetic energy is converted to heat, either locally deposited or transported away by enthalpy flux and deposited later. This mechanism is most relevant in the downflow region, which is more strongly governed by force balance; it is less important in the outflow above the reconnection site, where more energy remains in the form of fast bulk flow. Title: Inertial Alfvén Wave Acceleration of Solar Flare Electrons Authors: McClements, K. G.; Fletcher, L. Bibcode: 2009ApJ...693.1494M Altcode: The possibility that electrons could be accelerated by inertial Alfvén waves to hard X-ray-emitting energies in the low solar corona during flares is investigated theoretically. This investigation is prompted in part by recent microwave observations indicating that the coronal magnetic field is strong enough that the Alfvén velocity cA above active regions could be of the order of a tenth of the speed of light or more; electrons can be accelerated to velocities in excess of cA on collisionless timescales via reflection by a single inertial Alfvén wave pulse. It is shown that the fraction of particles accelerated is a sensitive function of the initial electron temperature and the transverse length scale δx of the shear Alfvén wave pulse; under typical pre-flare coronal conditions, a significant fraction of the electron population can be accelerated if δx is of the order of a few meters or less. Title: Retrievals of atmospheric variables on the gas giants from ground-based mid-infrared imaging Authors: Fletcher, L. N.; Orton, G. S.; Yanamandra-Fisher, P.; Fisher, B. M.; Parrish, P. D.; Irwin, P. G. J. Bibcode: 2009Icar..200..154F Altcode: Thermal-infrared imaging of Jupiter and Saturn using the NASA/IRTF and Subaru observatories are quantitatively analyzed to assess the capabilities for reproducing and extending the zonal mean atmospheric results of the Cassini/CIRS experiment. We describe the development of a robust, systematic and reproducible approach to the acquisition and reduction of planetary images in the mid-infrared (7-25 μm), and perform an adaptation and validation of the optimal estimation, correlated- k retrieval algorithm described by Irwin et al. [Irwin, P., Teanby, N., de Kok, R., Fletcher, L., Howett, C., Tsang, C., Wilson, C., Calcutt, S., Nixon, C., Parrish, P., 2008. J. Quant. Spectrosc. Radiat. Trans. 109 (6), 1136-1150] for channel-integrated radiances. Synthetic spectral analyses and a comparison to Cassini results are used to verify our abilities to retrieve temperatures, haze opacities and gaseous abundances from filtered imaging. We find that ground-based imaging with a sufficiently high spatial resolution is able to reproduce the three-dimensional temperature and para-H 2 fields measured by spacecraft visiting Jupiter and Saturn, allowing us to investigate vertical wind shear, pressure and, with measured cloud-top winds, Ertel potential vorticity on potential temperature surfaces. Furthermore, by scaling vertical profiles of NH 3, PH 3, haze opacity and hydrocarbons as free parameters during thermal retrievals, we can produce meridional results comparable with CIRS spectroscopic investigations. This paper demonstrates that mid-IR imaging instruments operating at ground-based observatories have access to several dynamical and chemical diagnostics of the atmospheric state of the gas giants, offering the prospect for quantitative studies over much longer baselines and often covering much wider areas than is possible from spaceborne platforms. Title: Methane and its isotopologues on Saturn from Cassini/CIRS observations Authors: Fletcher, L. N.; Orton, G. S.; Teanby, N. A.; Irwin, P. G. J.; Bjoraker, G. L. Bibcode: 2009Icar..199..351F Altcode: High spectral resolution observations from the Cassini Composite Infrared Spectrometer [Flasar, F.M., and 44 colleagues, 2004. Space Sci. Rev. 115, 169-297] are analysed to derive new estimates for the mole fractions of CH 4, CH 3D and 13CH 4 of (4.7±0.2)×10, (3.0±0.2)×10 and (5.1±0.2)×10 respectively. The mole fractions show no hemispherical asymmetries or latitudinal variability. The analysis combines data from the far-IR methane rotational lines and the mid-IR features of methane and its isotopologues, using both the correlated- k retrieval algorithm of Irwin et al. [Irwin, P., and 9 colleagues, 2008. J. Quant. Spectrosc. Radiat. Trans. 109, 1136-1150] and a line-by-line approach to evaluate the reliability of the retrieved quantities. C/H was found to be enhanced by 10.9±0.5 times the solar composition of Grevesse et al. [Grevesse, N., Asplund, M., Sauval, A., 2007. Space Sci. Rev. 130 (1), 105-114], 2.25±0.55 times larger than the enrichment on Jupiter, and supporting the increasing fractional core mass with distance from the Sun predicted by the core accretion model of planetary formation. A comparison of the jovian and saturnian C/N, C/S and C/P ratios suggests different reservoirs of the trapped volatiles in a primordial solar nebula whose composition varies with distance from the Sun. This is supported by our derived D/H ratio in methane of (1.6±0.2)×10, which appears to be smaller than the jovian value of Lellouch et al. [Lellouch, E., Bézard, B., Fouchet, T., Feuchtgruber, H., Encrenaz, T., de Graauw, T., 2001. Astron. Astrophys. 370, 610-622]. Mid-IR emission features provided an estimate of C12/C13=91.8-7.8+8.4, which is consistent with both the terrestrial ratio and jovian ratio, suggesting that carbon was accreted from a shared reservoir for all of the planets. Title: Ultra-violet footpoints as tracers of coronal magnetic connectivity and restructuring during a solar flare Authors: Fletcher, L. Bibcode: 2009A&A...493..241F Altcode: Context: The bright, compact ultraviolet sources that appear in flare ribbons are interpreted as sites of energisation of the chromosphere, most likely by electron beams from the corona. Previously we have developed an algorithm to track these compact sources in observations by the Transition Region and Coronal Explorer (TRACE), recording position and intensity. We now exploit this further.
Aims: We aim at identifying conjugate footpoint pairs by cross-correlating the TRACE 1600 Å lightcurves in one particular event - the 2002-July-17 M 8.5 flare. We also seek the spatial relationship between the magnetic flux transfer (reconnection) rate, well-connected locations, and energy input by electrons.
Methods: We performed wavelet à trous filtering on the UV light curves, followed by a linear cross-correlation, to identify well-correlated pairs. We used RHESSI data to determine the locations of strong electron beam input.
Results: Maps of footpoint pairs were produced in which we can identify well-separated locations that have well-correlated 1600 Å light curves. The time lag between credible conjugate footpoint brightenings can be a few seconds. The flare magnetic connectivity is found to evolve with time. RHESSI hard X-ray sources are found where the flux transfer rate is highest.
Conclusions: We propose that the correlated footpoints are in fact conjugate pairs that are magnetically linked. In some instances, this linkage may be via a coronal null. The time lag in many cases is consistent with excitation by relativistic particles, but correlations with a longer time lag may suggest excitation by waves. Title: Commission 10: Solar Activity Authors: Klimchuk, James A.; van Driel-Gesztelyi, Lidia; Schrijver, Carolus J.; Melrose, Donald B.; Fletcher, Lyndsay; Gopalswamy, Natchimuthuk; Harrison, Richard A.; Mandrini, Cristina H.; Peter, Hardi; Tsuneta, Saku; Vršnak, Bojan; Wang, Jing-Xiu Bibcode: 2009IAUTA..27...79K Altcode: 2008arXiv0809.1444K Commission 10 deals with solar activity in all of its forms, ranging from the smallest nanoflares to the largest coronal mass ejections. This report reviews scientific progress over the roughly two-year period ending in the middle of 2008. This has been an exciting time in solar physics, highlighted by the launches of the Hinode and STEREO missions late in 2006. The report is reasonably comprehensive, though it is far from exhaustive. Limited space prevents the inclusion of many significant results. The report is divided into the following sections: Photosphere and chromosphere; Transition region; Corona and coronal heating; Coronal jets; flares; Coronal mass ejection initiation; Global coronal waves and shocks; Coronal dimming; The link between low coronal CME signatures and magnetic clouds; Coronal mass ejections in the heliosphere; and Coronal mass ejections and space weather. Primary authorship is indicated at the beginning of each section. Title: Polar Phenomena in Outer Planet Atmospheres Authors: Orton, G.; Fletcher, L.; Yanamandra-Fisher, P.; Leyrat, C.; Greathouse, T.; Parrish, P.; Encrenaz, T.; Simon-Miller, A. Bibcode: 2008AGUFM.P11B1272O Altcode: Infrared observations of the polar regions of the outer planets have revealed similarities to the Earth's atmosphere and some new phenomena. The most dominant force which is apparent in time-dependent studies of the poles is seasonal radiative forcing, which was detected in Saturn's stratosphere as early as 1973. For Saturn, Uranus and Neptune, planets with substantial obliquities, the seasonally dependent changes are predictable and can be used to constrain abundances of optically active gases and the rate of restoration by stratospheric circulation. In the case of Neptune, recent evidence shows that the heating is sufficient to allow a "leak" from the reservoir of methane in the deep atmosphere into the polar stratosphere. New thermal images of Uranus show that the winter pole of Uranus which has only recently emerged fully from darkness is colder than when it was in the middle of winter when Voyager 2 visited, confirming the substantial seasonal phase delay associated with radiative heating and cooling models. Even Jupiter with its 3-degree obliquity shows clear evidence for seasonal forcing of temperatures in the upper troposphere and stratosphere. The second most prominent characteristic of the resolvable polar temperature fields in Jupiter and Saturn is the formation of polar vortices. Jupiter's polar vortices are cold, similar to those detected in the terrestrial planets; they have sharp equatorward boundaries which are characterized by Rossby waves which rotate at the speed of the local zonal wind flow and are coincident with the similarly irregular boundaries of a polar haze, also known as "polar hoods". The cold vortex at Saturn's northern winter pole is muted, but Saturn also has a unique "warm polar vortex" in the south (late summer) pole which shows no apparent wave structure. Saturn's warm polar vortex has no counterpart in the Earth's atmosphere, where summer radiative warming simply dissipates the cold winter vortex. Saturn also possesses dynamically driven hot regions within 2 degrees of its poles where dynamics is driving relatively dry air downwards, causing adiabatic warming and clearing the atmosphere; this phenomenon also has no terrestrial counterpart. Jupiter's upper polar stratosphere is warmed in discrete local regions by Joule heating from energetic particles cascading into the neutral atmosphere. The northern auroral-related polar "hot spot" has a very predictable geometry, but an amplitude that is variable over time scales of months. On the other hand, the stratosphere 25-30 degrees from Neptune's pole shows signs of ephemeral hot spots which are more likely to related to dynamics. These phenomena provide a rich basis of constraints for global climate models which must, at least for Jupiter, be coupled with models of auroral energy transport. Title: A General Radiative Seasonal Climate Model Applied to Saturn, Uranus, and Neptune. Authors: Greathouse, T. K.; Strong, S.; Moses, J.; Orton, G.; Fletcher, L.; Dowling, T. Bibcode: 2008AGUFM.P21B..06G Altcode: With similar compositions, a range of planet-sun distances, different orbital periods, and a variety of axial tilts, the Giant Planets are a unique test set for seasonal climate variation studies. We have created a general radiative seasonal climate model in an attempt to reproduce observed and predict future stratospheric temperatures of the Giant Planets. We present here a description of the radiative heating and cooling algorithms used in calculating the change in temperature with time. We will discuss the methods used to decrease run time, the opacity tables used, and indicate where more detailed opacity information would prove useful. We will use Saturn seasonal models to show the impact variations of the key coolants, acetylene and ethane, and the dominant heaters, methane and aerosols, have on predicted stratospheric temperatures. We will also present the initial results from the application of our model to the atmospheres of Uranus and Neptune. The same planet independent heating/cooling code implemented in our radiative seasonal climate model is being incorporated into the global circulation model EPIC. This work was funded by NASA PATM grants NNX08AE64G and NNX08AL95G. Title: Spatial and Temporal Relationships Between WL/UV Continuum and hard X-ray Footpoints in Solar Flares Authors: Hudson, H. S.; Fletcher, L.; McTiernan, J. Bibcode: 2008AGUFMSH41A1605H Altcode: Hard X-rays show the presence of energetic electrons in the impulsive phase of a solar flare. According to standard models, these electrons contain a large fraction of the total flare energy. We show that comparable amounts of energy are present in the compact, rapidly variable WL and UV bright points that constitute white-light flares. This suggests that these structures can be identified with each other, and indeed the image centroids and time variations match well. There are image differences that we believe mainly to be due to the different resolving powers of Hinode and TRACE WL/UV imaging on the one hand, and RHESSI hard X-rays on the other. We therefore also use RHESSI modeling software to simulate hard X-ray images using TRACE and Hinode data as templates to understand this relationship more precisely. Title: Saturn's South Polar Vortex Compared to Other Large Vortices in the Solar System Authors: Dyudina, U. A.; Ingersoll, A. P.; Ewald, S. P.; Vasavada, A. R.; West, R. A.; Baines, K. H.; Momary, T. W.; Barbara, J. M.; Del Genio, A. D.; Porco, C. C.; Achterberg, R. K.; Flasar, F.; Simon-Miller, A. A.; Fletcher, L. N. Bibcode: 2008AGUFM.P11C1283D Altcode: Observations made by the Imaging Science Subsystem (ISS), Visible and In- frared Mapping Spectrometer (VIMS) and the long-wavelength Composite Infrared Spectrometer (CIRS) aboard the Cassini spacecraft reveal that the large, long-lived cyclonic vortex at Saturn's south pole has a 4200-km-diameter cloud-free nearly circular region. This region has a 4 K warm core extending from the troposphere into the stratosphere, concentric cloud walls extending 20-70 km above the internal clouds, and numerous external clouds whose an- ticyclonic vorticity suggests a convective origin. The rotation speeds of the vortex reach 150-190 m/s, and may strengthen with depth. The Saturn polar vortex has features in common with terrestrial hurricanes and with the Venus polar vortex. Neptune and other giant planets may also have strong polar vortices. Title: Deuterium in the Outer Planets: New Constraints and New Questions from Infrared Spectroscopy Authors: Fletcher, L. N.; Orton, G. S.; Mainzer, A.; Line, M. R.; Merlet, C.; Burgdorf, M.; Irwin, P. G. Bibcode: 2008AGUFM.P21B..04F Altcode: We discuss how new observations of far-infrared rotational lines of HD and mid-infrared vibrational features of CH3D are challenging the accepted measurements for the deuterium abundance in the outer solar system. New derivations of D/H will be presented from the Cassini Composite Infrared Spectrometer (CIRS) for Saturn, the Spitzer Infrared Spectrometer (IRS) for Uranus and Neptune and the grism mode of the AKARI Infrared camera (IRC) for Neptune. Many thousands of spatially resolved Cassini/CIRS spectra at an unapodized spectral resolution of 0.25 cm-1 covering a variety of latitudes on Saturn have been acquired during Cassini's prime mission, and are coadded to give ten independent estimates of the HD mole fraction and hundreds of estimates of the CH3D mole fraction. Spitzer/IRS acquired disc-averaged spectra of Uranus during Cycle 1 and more recently with Director Discretionary time in December 2007. Neptune disc-averaged spectra were acquired during Cycle 2 (November 2005). ISAS/JAXA's AKARI satellite recorded disc-integrated spectra of Neptune in May 2007 with a resolving power of 50 in the 5.5-13 micron range. These spectra have been analysed using two separated radiative transfer and retrieval models to check for consistency of results. On Saturn, we retrieve lower estimates of D/H from HD and CH3D than were obtained from ISO/SWS by Lellouch et al. (2001). Preliminary analysis of Uranus spectra suggest that the CH3D/CH4 ratio is significantly smaller than that predicted by the HD abundance determined from ISO/SWS by Feuchtgruber et al. (1999), suggesting a Uranian ratio more like that of Saturn, or a substantially different fractionation factor from that in the current literature. Furthermore, although constraints on CH3D from mid-IR Neptune spectroscopy are weaker, preliminary findings are that the CH3D/CH4 ratio is lower than that obtained by Orton et al. (1992) and inferred from HD measurements from ISO/SWS (Feuchtgruber et al., 1999). Fletcher is supported by an appointment to the NASA Postdoctoral Program at the Caltech/Jet Propulsion Laboratory, administered by Oak Ride Associated Universities through a contract with NASA. Title: Saturn and Jupiter: Surprising Similarities and Stark Differences in Dynamics and Chemistry in the Gas Giants as Revealed by Galileo, Cassini, and New Horizons Authors: Baines, K. H.; Fletcher, L. N.; Momary, T. W.; West, R. A.; Atreya, S. K.; Brown, R. H.; Showman, A. P.; Simon-Miller, A. A. Bibcode: 2008AGUFM.P21B..05B Altcode: Imagery and spectra obtained by a variety of spacecraft over the past decade have revealed much about the atmospheres of the two gas giants. A partial listing of salient phenomena documented by these spacecraft on both planets include aurorae, lightning, the 3-D nature of zonal winds, thunderstorm-related clouds, spectrally-identifiable ammonia clouds, wave features, and long-lived discrete features at mid-latitudes and near the poles. Temporal variability in regional cloud structures are observed - seasonally on Saturn, more episodically on Jupiter. Molecular abundances of disequilibrium gases also vary spatially on both planets. These and other relevant phenomena will be discussed in this talk comparing the dynamics and chemistry of the two gas giants of our solar system. Title: Correlative Analysis of the Interaction of a Large Red Oval with the Great Red Spot and Oval BA in May - August 2008: Local Meteorology Authors: Yanamandra-Fisher, P. A.; Orton, G. S.; Fletcher, L. N.; Simon-Miller, A. Bibcode: 2008AGUFM.P11A1257Y Altcode: We acquired visible, near- and mid-infrared observations via a coordinated global campaign to observe the close encounter between the Great Red Spot and Oval BA, involving Hubble Space Telescope (HST), NASA/InfraRed Telescope Facility (IRTF)(NSFCAM2/MIRSI), Telescopio Nazionale Galileo (TNG)/NICS (with adaptive optics), Very Large Telescope (VLT)/VISIR, NOAJ/Subaru/COMICS and UKIRT/UIST (with tip-tilt). Although initial results indicate that changes in the albedo of the visible cloud deck and thermal field in the troposphere recovered shortly after the passage of the large red anticyclonic oval between the GRS and Oval BA, at near-infrared wavelengths, changes in the atmosphere are still occurring (as of this writing). The interaction started late June 2008. The small red oval, drifting eastward toward the GRS, was entrained in the peripheral flow south of the GRS. After being squeezed between the GRS and Oval BA, the elongated large red oval emerged, with part of it following a spiral path as it was entrained in the northern flow around the GRS, while another portion reformed itself slightly north of its pre-interaction latitude, indicating that the nature of the passage may have occurred at higher altitudes. By 10 July 2008, remnants of the red oval were still recognizable as a distinct feature as high-altitude particles in the near infrared. The red oval and Oval BA continued to drift eastward of the GRS. By 27 July 2008, the GRS and Oval BA were still observable at as relatively bright, discrete features in the reflected sunlight, with only the GRS showing a bright 4.78-micron annulus. However, the pre-encounter 4.78-micron bright annulus of the large red oval was not detectable. We shall present correlative analysis of the local meteorology of the interaction in terms of variations of the wind field, spectral composition, and tropospheric properties and compare with similar properties prior to the current interaction. Title: Hard X-ray emission from the solar corona Authors: Krucker, S.; Battaglia, M.; Cargill, P. J.; Fletcher, L.; Hudson, H. S.; MacKinnon, A. L.; Masuda, S.; Sui, L.; Tomczak, M.; Veronig, A. L.; Vlahos, L.; White, S. M. Bibcode: 2008A&ARv..16..155K Altcode: 2008A&ARv.tmp....8K This review surveys hard X-ray emissions of non-thermal electrons in the solar corona. These electrons originate in flares and flare-related processes. Hard X-ray emission is the most direct diagnostic of electron presence in the corona, and such observations provide quantitative determinations of the total energy in the non-thermal electrons. The most intense flare emissions are generally observed from the chromosphere at footpoints of magnetic loops. Over the years, however, many observations of hard X-ray and even γ-ray emission directly from the corona have also been reported. These coronal sources are of particular interest as they occur closest to where the electron acceleration is thought to occur. Prior to the actual direct imaging observations, disk occultation was usually required to study coronal sources, resulting in limited physical information. Now RHESSI has given us a systematic view of coronal sources that combines high spatial and spectral resolution with broad energy coverage and high sensitivity. Despite the low density and hence low bremsstrahlung efficiency of the corona, we now detect coronal hard X-ray emissions from sources in all phases of solar flares. Because the physical conditions in such sources may differ substantially from those of the usual “footpoint” emission regions, we take the opportunity to revisit the physics of hard X-radiation and relevant theories of particle acceleration. Title: Impulsive Flare Energy Transport by Large-Scale Alfven Waves, and Flare Electron Acceleration Authors: Fletcher, L.; Hudson, H. S. Bibcode: 2008ESPM...12.3.62F Altcode: The impulsive phase of a solar flare marks the epoch of rapid conversion of energy stored in the pre-flare coronal magnetic field. Hard X-ray observations imply that a substantial fraction of flare energy released during the impulsive phase is converted to the kinetic energy of mildly relativistic electrons (10-100 keV). The liberation of the magnetic free energy can occur as the coronal magnetic field reconfigures and relaxes following reconnection. Motivated by observations pointing to a high local Alfven speed in parts of the corona, and by considerations from magnetospheric physics, we investigate a scenario in which products of the reconfiguration - large-scale Alfven wave pulses - transport the energy and magnetic-field changes rapidly through the corona to the lower atmosphere. We investigate the opportunities that such a scenario offers for heating of the chromospheric plasma in flare footpoints, and for electron acceleration, and confront our findings with observational constraints, including energetics, HXR timing, and radio signatures. Title: Observations of the Interaction of a Large Red Oval with the Great Red Spot and Oval BA in May-Aug 2008: Thermal Emission Properties Authors: Orton, Glenn S.; Fletcher, L. N.; Yanamandra-Fisher, P. A.; Mousis, O.; Van den Anck, M.; Edkins, E.; Line, M.; Fujiyoshi, T.; Fuse, T.; Rogers, J.; Sanchez-Lavega, A.; Simon-Miller, A.; Chanover, N. Bibcode: 2008DPS....40.5002O Altcode: 2008BAAS...40..487O Thermal-infrared observations of the close passage of Jupiter's Great Red Spot and Oval BA serendipitously observed their interaction with a smaller and younger red anticyclone in late June through August of 2008. Filtered radiometric images were obtained at the NASA IRTF's MIRSI instrument at 7.85 - 24.5 microns, together with imaging between 8.8 and 24.5 microns and 7-14 micron spectroscopy at higher spatial resolution with the Subaru Telescope COMICS and the Very Large Telescope (Melipal) VISIR instruments over several nights in this time frame. The data were acquired during regularly scheduled observations at the IRTF and Subaru, service time at the VLT, and VLT target-of-opportunity observations triggered by this event. We derive maps of temperature structure in the 100-400 mbar range, variations of the para-hydrogen fraction and ammonia gas abundance near 300 mbar, and relative cloud opacities at the 600-mbar level and deeper. Before the interaction, the small red spot is clearly identified as a well-defined anticyclone with strongly-defined boundaries of peripheral subsidence and a cold and cloudy central upwelling. Drifting eastward toward the Great Red Spot, it was captured in the periphery of southbound flow around the GRS around July 1 and was recognizable over the next few days as a narrow, cold cloud feature, stretched around the GRS south periphery. The data suggest that a portion of it became entrained in the GRS itself and formed a very elongated and nearly spiral feature, while another portion remained outside the GRS and temporarily reformed to its east, accompanied by smaller fragments. As of this writing, the event is still taking place, and conclusions are tentative. Variations of tropospheric properties will be scrutinized and compared with prior conditions, as well as visible color changes and near-infrared tracking of upper-tropospheric particulates. Title: Investigation of Lyman <alpha> Emission in a Solar Flare Authors: Rubio da Costa, F.; Fletcher, L.; Labrosse, N.; Zuccarello, F. Bibcode: 2008ESPM...12.2.64R Altcode: The TRACE satellite observed a small number of solar flares in the Lyman alpha channel, which have until now not been analysed. We look at a well-observed flare on 8th September 1999 to investigate different topics. We carry out a study of the spatial and temporal evolution of the flare and associated filament eruption in Lyman alpha, hard X-rays and soft X-rays, and examine the flare energetics using the hard X-rays (in the collisional thick target approximation) to estimate the energy flux carried by electrons, and TRACE Lyman alpha/1600 Å channels to estimate the temperature and radiative power in UV. We will use these observations to anticipate what can be observed in the future by the proposed SMESE satellite mission, and to compare with predictions of semi-empirical and theoretical models of the flare chromosphere. Title: The Strongest Jet Ever Detected and a New Thermal Wave in Saturn's Equatorial Stratosphere Authors: Li, Liming; Gierasch, P.; Achterberg, R.; Conrath, B.; Flasar, M.; Vasavada, A.; Ingersoll, A.; Banfield, D.; Simon-Miller, A.; Fletcher, L. Bibcode: 2008DPS....40.5306L Altcode: 2008BAAS...40..495L The strongest stratospheric jet yet detected, with a speed between 500 and 600 m/s, has been discovered in the equatorial region of Saturn by combining the nadir and limb observations of Composite Infrared Spectrometer (CIRS) aboard the Cassini spacecraft. A similar jet was discovered on Jupiter. These discoveries raise the possibility that intense jets are common in the equatorial stratospheres of giant planets. The jet's velocity is steady during the observational period (March, 2005 to January, 2008), but variations over a longer time-scale are possible and may be associated with the semi-annual oscillations of Saturn&#226&#8364&#8482s low-latitude stratospheric temperatures. An equatorial wave with wavenumber 9 is revealed in the stratosphere of Saturn by the CIRS high spatial-resolution thermal maps. The equatorial wave has a westward phase velocity of 10-110 m/s relative to the background current, indicating that it is an equatorial Rossby wave. The discovery of an equatorial wave in the stratosphere suggests that Saturn's equatorial oscillations may be driven by vertically propagating waves, the same mechanism that drives the quasi-biennial oscillation (QBO) on Earth. Title: Hard X-ray Emission from a Flare-related Jet Authors: Bain, H. M.; Fletcher, L. Bibcode: 2008ESPM...122.102B Altcode: We report the observation of hard X-ray emission which we attribute to a flare-related jet. The event occurred on the 22nd of August 2002 and its evolution was observed by a number of instruments. In particular we study the pre-impulsive and impulsive phase of the flare using data from RHESSI and the TRACE 195 passband. During this period RHESSI observes significant hard X-ray emission to energies as high as 50 keV in the jet. Estimates from RHESSI spectroscopy suggest a temperature of the order of approximately 20MK for this time. Radio observations from the Nobeyama Radioheliograph (NoRH) show a positive spectral index for the ejected material backing the presence of non-thermal emission. This also shows the jet to be optically thick at radio frequencies, possibly due to free-free absorption. Title: First Results of Infrared Spectroscopy of Neptune From AKARI IRC Authors: Burgdorf, Martin J.; Drossart, P.; Encrenaz, T.; Fletcher, L. N.; Orton, G. Bibcode: 2008DPS....40.5009B Altcode: 2008BAAS...40..489B Disk-integrated spectra of Neptune were recorded on 2007-05-13, between 1.8 and 13 microns, using both the prism and the grism of the Infrared Camera on board ISAS/JAXA's AKARI satellite. The spectral resolving power was about 140 in the interval 2.5 - 5 microns and between 20 and 50 at other wavelengths. As Triton was included in the field of view at a distance of only 6 arcsec in the cross-dispersion direction, we had to subtract its contribution to the near-infrared spectra.

From the mid-infrared spectra we determine the stratospheric temperature and the CH4 mixing ratio. We find good agreement with the observations obtained with the infrared spectrometer aboard Spitzer on 2005-11-20, with possible differences in the measured emission of ethane and methane between the two observatories being less than 10%. In contrast to this we find in the near-infrared flux densities up to a factor five weaker than previous measurements, confirming the presence of meteorological variations.

At short wavelength, an emission peak at 4.7 microns can be interpreted as due to fluorescent emission of CO. A similar emission feature has been detected previously on Uranus (Encrenaz et al, A&A, 2004). As on Uranus, the fluorescent dominant emission comes from CO (2-1) band, and fits the observed peak. The contribution from the (1-0) band is strongly self-absorbed, and weaker. Synthetic spectra are calculated from a non-LTE radiative model, including solar radiation absorption, self-absorption in the resonant fluorescent (1-0) band, and frequency redistribution from vibrational CO bands. The spectra are compared to constrain the vertical variation of CO abundance as measured from submm range (Hesman et al, Icarus, 2007), the information from the fluorescence emission coming from as deep as the 1 bar level. Title: Jupiter's South Equatorial Belt Outbreak Spots and the SEB Fade and Revival Cycle Authors: Go, Christopher; de Pater, I.; Marcus, P.; Rogers, J.; Simon-MIller, A.; Wong, M.; Orton, G.; Baines, K.; Asay-Davis, X.; Yanamandra-Fisher, P.; Fletcher, L. Bibcode: 2008DPS....40.4306G Altcode: 2008BAAS...40..475G Amateur planetary imagers chronicled the 2007 upheaval of Jupiter, providing an opportunity to observe the Fade/Revival Cycle of the South Equatorial Belt (SEB). When the outbreaks of convective white spots in the SEB stopped, the SEB faded and the wake of the GRS disappeared. When an outbreak appeared, the SEB revival occurred--and the GRS wake became turbulent once more. The distinctive dark red color of the SEB is also associated with material brought up by SEB outbreaks.

This poster will show the SEB Fade and Revival cycle and how the SEB Outbreak plays a role in this cycle from images from various amateur astronomers, along with images from the Hubble Space Telescope, ground based observatories and various spacecraft. Title: Saturn's North Polar Vortex Revealed by Cassini/VIMS: Zonal Wind Structure and Constraints on Cloud Distributions Authors: Baines, Kevin H.; Momary, T. W.; Fletcher, L. N.; Buratti, B. J.; Roos-Serote, M.; Showman, A. P.; Brown, R. H.; Clark, R. N.; Nicholson, P. D. Bibcode: 2008DPS....40.5309B Altcode: 2008BAAS...40..495B We present the first high-spatial resolution, near-nadir imagery and movies of Saturn's north polar region that reveal the wind structure of a north polar vortex. Obtained by Cassini/VIMS on June 15, 2008 from high over Saturn's polar region (sub-spacecraft latitude of 65 degrees N. lat) at an altitude of 0.42 million km during the long polar night, these 210-per-pixel images of the polar region north of 73 degrees N. latitude show several concentric cloud rings and hundreds of individual cloud features in silhouette against the 5-micron background thermal glow of Saturn's deep atmosphere. In contrast to the clear eye of the south polar vortex, the north polar vortex sports a central cloud feature about 650-km in diameter. Zonal winds reach a maximum of 150 m/s near 88 degrees N. latitude (planetocentric) - comparable to the south polar vortex maximum of 190 m/s near 88 degrees S. latitude - and fall off nearly monotonically to 10 m/s near 80 degrees N. latitude. At slightly greater distance from the pole, inside the north polar hexagon in the 75-77 degree N. latitude region, zonal winds increase dramatically to 130 m/s, as silhouetted clouds are seen speeding aroud the "race track” of the hexagonal feature. VIMS 5-micron thermal observations over a 1.6-year period from October 29, 2006 to June 15, 2008 are consistent with the polar hexagon structure itself remaining fixed in the Voyager-era radio rotation rate (Desch and Kaiser, Geophys. Res. Lett, 8, 253-256, 1981) to within an accuracy of 3 seconds per rotational period. This agrees with the stationary nature of the wave in this rotation system found by Godfrey (Icarus 76, 335-356, 1988), but is inconsistent with rotation rates found during the current Cassini era. Title: The Pre-flare Phase: Key to Understanding Energy and Mass Transport in Flare Loops Authors: Battaglia, M.; Fletcher, L.; Benz, A. O. Bibcode: 2008ESPM...12.2.85B Altcode: In the classical solar flare scenario, the chromosphere is heated by an incident beam of supra-thermal electrons that were accelerated in the corona, then precipitated downward along the field lines of a magnetic loop. The hot chromospheric plasma expands and fills the magnetic loops. This process has been termed chromospheric evaporation. The classical scenario causes characteristic emission in soft- and hard X-rays, both from the corona and the chromosphere. The time evolution of this emission follows a specific pattern known as the Neupert effect.

Recent observations indicate that this scenario is only applicable for about half of the observed flares (Veronig et al. 2002). The early rise phase of many events is dominated by increasing soft X-ray emission up to minutes before the onset of the hard X-ray emission. This pre-heating clearly contradicts the classical Neupert scenario and indicates that other mechanisms of energy transport such as thermal conduction have to be at work. It also implies that the pre-flare energy release is dominated by heating, not acceleration. While energy transport by thermal conduction and subsequent chromospheric evaporation has been studied in some detail for the decay phase of solar flares, we present the first comprehensive study of the early phases of 4 pre-heating events. We analyze the time evolution of those events in imaging and spectroscopy using data from the RHESSI satellite and demonstrate how this can improve our understanding of heating and evaporation processes in coronal loops and the initiation of particle acceleration. Title: Saturn's Dynamic Atmosphere at Depth: Physical Characteristics and Zonal Winds Derived from Clouds Near the 2-bar Level and Their Dynamical Implications from Cassini-Huygens/VIMS Authors: Momary, Thomas W.; Baines, K. H.; Fletcher, L. N.; Kim, J. H.; Buratti, B. J.; Roos-Serote, M.; Showman, A. P.; Brown, R. H.; Clark, R. N.; Nicholson, P. D.; Cassini/VIMS Science Team Bibcode: 2008DPS....40.4113M Altcode: 2008BAAS...40..472M A wide variety of cloud structures - comprised, putatively, of ammonia and ammonia hydrosulfide , but perhaps with an admixture of water - has been characterized by Cassini/VIMS, including dozens of axisymmetric zonal features, planetary waves, classic vortex structures at both the north and south poles, and a hexagonal slow-speed wave feature centered on the north pole. At depth, the axisymmetric zonal features average just 1.7 degrees in latitudinal width, less than half of that at the 0.05- and 0.5-bar levels observed in reflected sunlight, suggesting that either (1) the patterns of ascending/descending motion have smaller latitudinal length scales at > 1.3 bar than at shallower levels, and/or (2) horizontal mixing is better able to "smooth out" the cloud structure at shallow levels than at depth. Numerous long-lived (> 1.5-years) discrete cloud structures have been observed in the northern hemisphere, including annular ("donut") clouds near 49 and 57 degrees north latitude (planetocentric) and a "string of pearls” of some two-dozen similarly sized ( 1500 km diameter) cloud-clearings nearly uniformly spaced across 100 degrees of longitude near 33.5 degrees latitude. The "string of pearls” and the mid-latitude annular cloud exhibit the fastest retrograde speeds on Saturn (in the Voyager rotational frame). In the south, the fastest retrograde jet correlates with the only thunderstorm-associated clouds observed on Saturn. VIMS daytime spectra indicate that two kinds of clouds predominate there: spectrally bright and spectrally dark. The bright clouds are the first spectrally-identified ammonia clouds on Saturn, presumably formed by ammonia-laden air propelled upward by thunderstorm-related convection originating > 75 km below. Thus both vertically-extensive (thunderstorms) and long-lived, coherent cloud features ("pearls” and "donuts") correlate well with retrograde motions, perhaps indicating unusually low vertical shears there which preserve coherency and allow convective flows to rise relatively unimpeded over large vertical distances. Title: Energy Release and Transport in Solar Flares: Three-Dimensional MHD Simulations Authors: Birn, J.; Birn, J.; Fletcher, L.; Hesse, M.; Neukirch, T. Bibcode: 2008ESPM...12.3.33B Altcode: Using three-dimensional magnetohydrodynamic (MHD) simulations, we investigate energy release and transfer in a three-dimensional extension of the standard two-ribbon flare picture. In this scenario reconnection is initiated in a thin current sheet (suggested to form below a departing coronal mass ejection) above a bipolar magnetic field. Two cases are contrasted: an initially force-free current sheet (low beta) and a finite-pressure current sheet (high beta). The energy conversion process from reconnection consists of incoming Poynting flux (from the release of magnetic energy) turned into up- and downgoing Poynting flux, enthalpy flux and bulk kinetic energy flux. In the low-beta case, the outgoing Poynting flux is the dominant contribution, whereas the outgoing enthalpy flux dominates in the high-beta case. The bulk kinetic energy flux is only a minor contribution, particularly in the downward direction. The dominance of the downgoing Poynting flux in the low-beta case, which may be seen as an Alfvenic pulse, is consistent with an alternative to the thick target electron beam model for solar flare energy transport, suggested recently by Fletcher and Hudson. For plausible characteristic parameters of the reconnecting field configuration, we obtain energy release time scales and and energy output rates that compare favorably with those inferred from observations for the impulsive phase of flares. Title: The Continuing Evolution of the Interaction of a Large Red Oval with the Great Red Spot and Oval BA in May - August 2008: Near-Infrared Properties Authors: Yanamandra-Fisher, Padma A.; Orton, G. S.; Fletcher, L. N.; Tanga, P.; Cecconi, M.; Adamoli, G.; Irwin, P.; Holt, D.; Grimes, H.; Edkins, E.; Brookhart, M.; Adamson, A. Bibcode: 2008DPS....40.4103Y Altcode: 2008BAAS...40..469Y We acquired near- and mid-infrared observations via a coordinated global campaign to observe the close encounter between the Great Red Spot and Oval BA, involving NASA/InfraRed Telescope Facility (IRTF)(NSFCAM2/MIRSI), Telescopio Nazionale Galileo (TNG)/NICS (with adaptive optics), Very Large Telescope (VLT)/VISIR, NOAJ/Subaru/COMICS and UKIRT/UIST (with tip-tilt). We focus on near-infrared observations where the longest-lasting changes to the atmosphere occurred and report on the evolution of a large red anticyclonic vortex that passed between them because of the unexpected nature of the event. The interaction started late June 2008. After being squeezed between the much larger GRS and Oval BA 1-3 July 2008, the large red oval emerged slightly north of its pre-interaction latitude, indicating that the nature of the passage may have occurred at higher altitudes. By 10 July 2008, remnants of the red oval were still recognizable as a distinct feature as high-altitude particles in the near infrared. The red oval and Oval BA continued to drift eastward of the GRS. Some peripheral material from the red oval appeared to have become entrained around the GRS northern boundary. By 27 July 2008, the GRS and Oval BA were still observable at as relatively bright, discrete features in the reflected sunlight, with only the GRS showing a bright 4.78-micron annulus. However, the pre-encounter 4.78-micron bright annulus of the large red oval was not detectable. In reflected sunlight from upper-atmospheric particulates, the large red oval had evolved into a main core, accompanied by a number of small discrete features, quasi-evenly located between the main core and the northeast quadrant of the GRS. The GRS-Oval BA-large red oval complex continues to evolve in the near-infrared. As of this writing, we continue to acquire further observations of the three-oval complex. Title: Spitzer IRS Analysis of Neptune Authors: Line, Michael R.; Orton, G. S.; Fletcher, L. N.; Mahmud, A.; Moses, J. I.; Mainzer, A. K.; Yung, Y. L. Bibcode: 2008DPS....40.4203L Altcode: 2008BAAS...40..473L Recent (2005) Spitzer Infrared Spectrometer (IRS) data of Neptune between 5 and 20 um contain a wealth of information about the chemical composition and temperature structure of its cold atmospheres. Emission features in its spectrum arise from many hydrocarbons, including ethane, acetylene and methane, and they appear to be superimposed on top of a collision-induced H2 continuum. As the derivation of all other parameters depends on the assumed temperature profile, special efforts were taken to ensure that the stratospheric profile between 1 bar and 0.3 mbar matched the H2 continuum and the H2 S(1) quadrupole feature at 17 um. Additionally we matched the methane v4 feature at 7.7 um in order to constrain the stratospheric temperature profile above the 0.3-mbar level as well as the methane stratospheric volume mixing ratios (VMRs). After the determination of the temperature profile and methane VMRs, the VMRs for several species were then determined through fitting their corresponding features in the spectrum, initially by scaling existing photochemical models (see Mahmud et al., this conference). These species include methylacetylene, diacetylene, benzene, acetylene, ethane, methyl radical, ethylene and carbon dioxide which are all derived from methane photochemistry.

I would like to acknowledge the NASA USRP program for supporting this work. Title: Solar Flare Impulsive-phase Footpoints in Extreme UV, Soft X-Rays and Hard X-Rays Authors: Bain, H. M.; Fletcher, L. Bibcode: 2008ASPC..397..157B Altcode: We examine the flare of 14 March 2002, which has early impulsive phase TRACE 171 Å channel EUV footpoints co-spatial with RHESSI foopoints at energies between 6 and 50 keV. Surprisingly, the HXR spectrum from these footpoint sources at this time is clearly thermal, consistent with plasma temperatures up to 30 MK. The evidence points to impulsive thermal footpoint emission, such as was observed previously with the Yohkoh Soft X-ray Telescope, implying that the upper chromosphere or transition region plasma is heated rapidly to temperatures of millions of degrees. Title: A Testbed for Advanced Cold Curation of Astromaterials Authors: Fletcher, L. A.; Bastien, R.; Allen, C. C. Bibcode: 2008M&PSA..43.5066F Altcode: No abstract at ADS Title: Changing Characteristics of Jupiter's Little Red SPOT Authors: Cheng, A. F.; Simon-Miller, A. A.; Weaver, H. A.; Baines, K. H.; Orton, G. S.; Yanamandra-Fisher, P. A.; Mousis, O.; Pantin, E.; Vanzi, L.; Fletcher, L. N.; Spencer, J. R.; Stern, S. A.; Clarke, J. T.; Mutchler, M. J.; Noll, K. S. Bibcode: 2008AJ....135.2446C Altcode: The Little Red Spot (LRS) in Jupiter's atmosphere was investigated in unprecedented detail by the New Horizons spacecraft together with the Hubble Space Telescope (HST) and the Very Large Telescope (VLT). The LRS and the larger Great Red Spot (GRS) of Jupiter are the largest known atmospheric storms in the solar system. Originally a white oval, the LRS formed from the mergers of three smaller storms in 1998 and 2000, and became as red as the GRS between 2005 and 2006. Here we show that circulation and wind speeds in the LRS have increased substantially since the Voyager and Galileo eras when the oval was white. The maximum tangential velocity of the LRS is now 172 ± 18 m s-1, close to the highest values ever seen in the GRS, which has also evolved both in size and maximum wind speed. The cloud-top altitudes of the GRS and LRS are similar, both storms extending much higher in the atmosphere than other Jovian anti-cyclonic systems. The similarities in wind speeds, cloud morphology, and coloring suggest a common dynamical mechanism explaining the reddening of the two largest anticyclonic systems on Jupiter. These storms will not be observed again from close range until at least 2016. Title: The role of large-scale Alfvén waves in solar flare energy release and particle acceleration Authors: Fletcher, L.; Hudson, H. S. Bibcode: 2008AGUSMSH51C..06F Altcode: The impulsive phase of a solar flare marks the epoch of rapid conversion of energy stored in the pre-flare coronal magnetic field. Hard X-ray observations imply that a substantial fraction of flare energy released during the impulsive phase is converted to the kinetic energy of mildly relativistic electrons (10-100 keV). The liberation of the magnetic free energy can occur as the coronal magnetic field reconfigures and relaxes following reconnection. We investigate a scenario, inspired in part by magnetospheric physics, in which products of the reconfiguration - large-scale Alfvén wave pulses - transport the energy and magnetic-field changes rapidly through the corona to the lower atmosphere. This offers two possibilities for electron acceleration. Firstly, in a coronal plasma with E < me/mp, the waves propagate as inertial Alfvén waves. In the presence of strong spatial gradients, these generate field-aligned electric fields that can accelerate electrons to energies on the order of 10 keV and above, including by repeated interactions between electrons and wavefronts. Secondly, when they reflect in the chromosphere, a cascade to high wave numbers may develop. This will also accelerate electrons by turbulence, in a medium with a locally high electron number density. This concept, which bridges MHD-based and particle- based views of a flare, provides an interpretation of the recently-observed rapid variations of the line-of-sight component of the photospheric magnetic field across the flare impulsive phase, and offers solutions to some perplexing flare problems, such as the flare "number problem" of finding and resupplying sufficient electrons to explain impulsive-phase hard X-ray emission. Title: The NEMESIS planetary atmosphere radiative transfer and retrieval tool Authors: Irwin, P. G. J.; Teanby, N. A.; de Kok, R.; Fletcher, L. N.; Howett, C. J. A.; Tsang, C. C. C.; Wilson, C. F.; Calcutt, S. B.; Nixon, C. A.; Parrish, P. D. Bibcode: 2008JQSRT.109.1136I Altcode: No abstract at ADS Title: Impulsive Phase Flare Energy Transport by Large-Scale Alfvén Waves and the Electron Acceleration Problem Authors: Fletcher, L.; Hudson, H. S. Bibcode: 2008ApJ...675.1645F Altcode: 2007arXiv0712.3452F The impulsive phase of a solar flare marks the epoch of rapid conversion of energy stored in the preflare coronal magnetic field. Hard X-ray observations imply that a substantial fraction of flare energy released during the impulsive phase is converted to the kinetic energy of mildly relativistic electrons (10-100 keV). The liberation of the magnetic free energy can occur as the coronal magnetic field reconfigures and relaxes following reconnection. We investigate a scenario in which products of the reconfiguration—large-scale Alfvén wave pulses—transport the energy and the magnetic field changes rapidly through the corona to the lower atmosphere. This offers two possibilities for electron acceleration. First, in a coronal plasma with β < me/mp, the waves propagate as inertial Alfvén waves. In the presence of strong spatial gradients, these generate field-aligned electric fields that can accelerate electrons to energies on the order of 10 keV and above, including by repeated interactions between electrons and wave fronts. Second, when they reflect and mode-convert in the chromosphere, a cascade to high wavenumbers may develop. This will also accelerate electrons by turbulence, in a medium with a locally high electron number density. This concept, which bridges MHD-based and particle-based views of a flare, provides an interpretation of the recently observed rapid variations of the line-of-sight component of the photospheric magnetic field across the flare impulsive phase, and offers solutions to some perplexing flare problems, such as the flare "number problem" of finding and resupplying sufficient electrons to explain the impulsive-phase hard X-ray emission. Title: Atacama Desert Mudflow as an Analog for Recent Gully Activity on Mars Authors: Heldmann, J. L.; Conley, C.; Brown, A. J.; Fletcher, L.; Bishop, J. L.; McKay, C. P. Bibcode: 2008LPI....39.2214H Altcode: We discuss light-toned gully deposits in the Atacama Desert that share similar morphologic and spectral signatures with the new Mars gully deposits. We suggest that, similar to the Atacama deposits, the Mars gully features may be remnant mudflows. Title: Curation of Frozen Samples Authors: Fletcher, L. A.; Allen, C. C.; Bastien, R. Bibcode: 2008LPI....39.2202F Altcode: We discuss the design, installation, and testing of a cold glovebox system to be used for the curation of future frozen samples. Title: Global and temporal variations in hydrocarbons and nitriles in Titan's stratosphere for northern winter observed by Cassini/CIRS Authors: Teanby, N. A.; Irwin, P. G. J.; de Kok, R.; Nixon, C. A.; Coustenis, A.; Royer, E.; Calcutt, S. B.; Bowles, N. E.; Fletcher, L.; Howett, C.; Taylor, F. W. Bibcode: 2008Icar..193..595T Altcode: Mid-infrared spectra measured by Cassini's Composite InfraRed Spectrometer (CIRS) between July 2004 and January 2007 ( L=293°-328°) have been used to determine stratospheric temperature and abundances of C 2H 2, C 3H 4, C 4H 2, HCN, and HC 3N. Over 65,000 nadir spectra with spectral resolutions of 0.5 and 2.5 cm -1 were used to probe spatial and temporal composition variations in Titan's stratosphere. Cassini's 180° orbital transfer in mid-2006 allowed low emission angle observations of the north polar region for the first time in the mission and allowed us to probe the full latitude range. We present the first measurements of composition variations within the polar vortex, which display increasing abundances right up to 90° N. The lack of a homogeneous abundance-latitude variation within the vortex indicates limited horizontal mixing and suggests that subsidence is greatest at the vortex core. Contrary to numerical model predictions and tropospheric cloud observations, we do not see any evidence for a secondary circulation cell near the south pole, which suggests a single Hadley-type circulation in the stratosphere at this epoch. This difference can be reconciled if the secondary cell is restricted to altitudes below 100 km, where there is no sensitivity in our data. Temporal variations in composition were observed in the south, with volatile species becoming less abundant as the season progressed. The observed variations are compared to numerical model predictions and observations from Voyager. Title: Depth of a strong jovian jet from a planetary-scale disturbance driven by storms Authors: Sánchez-Lavega, A.; Orton, G. S.; Hueso, R.; García-Melendo, E.; Pérez-Hoyos, S.; Simon-Miller, A.; Rojas, J. F.; Gómez, J. M.; Yanamandra-Fisher, P.; Fletcher, L.; Joels, J.; Kemerer, J.; Hora, J.; Karkoschka, E.; de Pater, I.; Wong, M. H.; Marcus, P. S.; Pinilla-Alonso, N.; Carvalho, F.; Go, C.; Parker, D.; Salway, M.; Valimberti, M.; Wesley, A.; Pujic, Z. Bibcode: 2008Natur.451.1022S Altcode: No abstract at ADS Title: Invisible sunspots and rate of solar magnetic flux emergence Authors: Dalla, S.; Fletcher, L.; Walton, N. A. Bibcode: 2008A&A...479L...1D Altcode: 2008arXiv0801.0703D Aims:We study the visibility of sunspots and its influence on observed values of sunspot region parameters.
Methods: We use Virtual Observatory tools provided by AstroGrid to analyse a sample of 6862 sunspot regions. By studying the distributions of locations where sunspots were first and last observed on the solar disk, we derive the visibility function of sunspots, the rate of magnetic flux emergence and the ratio between the durations of growth and decay phases of solar active regions.
Results: We demonstrate that the visibility of small sunspots has a strong centre-to-limb variation, far larger than would be expected from geometrical (projection) effects. This results in a large number of young spots being invisible: 44% of new regions emerging in the west of the Sun go undetected. For sunspot regions that are detected, large differences exist between actual locations and times of flux emergence, and the apparent ones derived from sunspot data. The duration of the growth phase of solar regions has been, up to now, underestimated.

Appendix A is only available in electronic form at http://www.aanda.org Title: Atacama Desert Mudflow as an Analog for Recent Gully Activity on Mars Authors: Heldmann, J. L.; Conley, C.; Brown, A. J.; Fletcher, L. Bibcode: 2008LPICo1303...44H Altcode: No abstract at ADS Title: Temperature and Composition of Saturn’s Polar Hot Spots and Hexagon Authors: Fletcher, L. N.; Irwin, P. G. J.; Orton, G. S.; Teanby, N. A.; Achterberg, R. K.; Bjoraker, G. L.; Read, P. L.; Simon-Miller, A. A.; Howett, C.; de Kok, R.; Bowles, N.; Calcutt, S. B.; Hesman, B.; Flasar, F. M. Bibcode: 2008Sci...319...79F Altcode: Saturn’s poles exhibit an unexpected symmetry in hot, cyclonic polar vortices, despite huge seasonal differences in solar flux. The cores of both vortices are depleted in phosphine gas, probably resulting from subsidence of air into the troposphere. The warm cores are present throughout the upper troposphere and stratosphere at both poles. The thermal structure associated with the marked hexagonal polar jet at 77°N has been observed for the first time. Both the warm cyclonic belt at 79°N and the cold anticyclonic zone at 75°N exhibit the hexagonal structure. Title: Depth of a strong jovian jet from a planetary-scale disturbance driven by storms Authors: Sánchez-Lavega, A.; Orton, G. S.; Hueso, R.; García-Melendo, E.; Pérez-Hoyos, S.; Simon-Miller, A.; Rojas, J. F.; Gómez, J. M.; Yanamandra-Fisher, P.; Fletcher, L.; Joels, J.; Kemerer, J.; Hora, J.; Karkoschka, E.; de Pater, I.; Wong, M. H.; Marcus, P. S.; Pinilla-Alonso, N.; Carvalho, F.; Go, C.; Parker, D.; Salway, M.; Valimberti, M.; Wesley, A.; Pujic, Z. Bibcode: 2008Natur.451..437S Altcode: The atmospheres of the gas giant planets (Jupiter and Saturn) contain jets that dominate the circulation at visible levels. The power source for these jets (solar radiation, internal heat, or both) and their vertical structure below the upper cloud are major open questions in the atmospheric circulation and meteorology of giant planets. Several observations and in situ measurements found intense winds at a depth of 24bar, and have been interpreted as supporting an internal heat source. This issue remains controversial, in part because of effects from the local meteorology. Here we report observations and modelling of two plumes in Jupiter's atmosphere that erupted at the same latitude as the strongest jet (23°N). The plumes reached a height of 30km above the surrounding clouds, moved faster than any other feature (169ms-1), and left in their wake a turbulent planetary-scale disturbance containing red aerosols. On the basis of dynamical modelling, we conclude that the data are consistent only with a wind that extends well below the level where solar radiation is deposited. Title: Impulsive Flare Energy Transport by Large-Scale Alfven Waves and the Electron Acceleration Problem Authors: Fletcher, L.; Hudson, H. S. Bibcode: 2007AGUFMSM53B1278F Altcode: In this poster, we investigate an alternative scenario for solar flare energy transport. Usually, the energy stored in the solar corona and released during a flare is thought to be transported to the lower atmosphere by electron beams. However, based on microwave observations, magnetic fields of the order of a few 100 Gauss to a kilogauss are measured in the corona above the core of an active region. This implies an Alfvén speed on the order of 0.1c, meaning that Alfvén wave pulses become plausible agents for transporting the stored energy of the flare. We investigate this scenario, and the opportunities it presents for both heating the lower chromosphere and accelerating electrons to HXR-emitting energies. Title: Observations of Jupiter Supporting the New Horizons Encounter and During a Period of "Global Upheaval" Authors: Orton, G.; Baines, K.; Yanamandra-Fisher, P.; Mousis, O.; Vanzi, L.; Hayward, T.; De Buizer, J.; Simon-Miller, A.; Bjoraker, G.; Fletcher, L.; Gladstone, R.; Edkins, E.; Kemerer, J.; Sitko, M.; Lynch, D. Bibcode: 2007AGUFM.P53C..03O Altcode: Observations of Jupiter were made between February and June of 2007 to provide an expanded spectral coverage and timeline for the New Horizons remote-sensing of Jupiter's atmosphere. From March to May, two prominent vertical jets in the southern portion of Jupiter's North Temperate Belt (NTBs) initiated a major darkening of this region, and their wakes restored the darker color of the belt but not its bright 5-micron appearance. A brightening of the southern component of the dark South Equatorial Belt (SEBs) was interrupted by a series of vertical outbursts from which a darker material emanated in both directions was appeared bright at 5 microns.It also generated a series of anticyclonic vortices with upwelling interiors and substantial downwelling annuli which continue to this writing. Title: Characteristics of Titan's stratospheric aerosols and condensate clouds from Cassini CIRS far-infrared spectra Authors: de Kok, R.; Irwin, P. G. J.; Teanby, N. A.; Nixon, C. A.; Jennings, D. E.; Fletcher, L.; Howett, C.; Calcutt, S. B.; Bowles, N. E.; Flasar, F. M.; Taylor, F. W. Bibcode: 2007Icar..191..223D Altcode: Four broad spectral features were identified in far-infrared limb spectra from the Cassini Composite Infrared Spectrometer (CIRS), two of which have not been identified before. The features are broader than the spectral resolution, which suggests that they are caused by particulates in Titan's stratosphere. We derive here the spectral properties and variations with altitude for these four features for six latitudes between 65° S and 85° N. Titan's main aerosol is called Haze 0 here. It is present at all wavenumbers in the far-infrared and is found to have a fractional scale height (i.e., the aerosol density scale height divided by the atmospheric density scale height) between 1.5 and 1.7 with a small increase in opacity in the north. A second feature around 140 cm -1 (Haze A) has similar spatial properties to Haze 0, but has a smaller fractional scale height of 1.2-1.3. Both Haze 0 and Haze A show an increase in retrieved abundance below 100 km. Two other features (Haze B around 220 cm -1 and Haze C around 190 cm -1) have a large maximum in their density profiles at 140 and 90 km, respectively. Haze B is much more abundant in the northern hemisphere compared to the southern hemisphere. Haze C also shows a large increase towards the north, but then disappears at 85° N. Title: The relative timing of supra-arcade downflows in solar flares Authors: Khan, J. I.; Bain, H. M.; Fletcher, L. Bibcode: 2007A&A...475..333K Altcode: Context: Supra-arcade downflows (generally dark, sunward-propagating features located above the bright arcade of loops in some solar flares) have been reported mostly during the decay phase, although some have also been reported during the rise phase of solar flares.
Aims: We investigate, from a statistical point of view, the timing of supra-arcade downflows during the solar flare process, and thus determine the possible relation of supra-arcade downflows to the primary or secondary energy release in a flare.
Methods: Yohkoh Soft X-ray Telescope (SXT) imaging data are examined to produce a list of supra-arcade downflow candidates. In many of our events supra-arcade downflows are not directly observed. However, the events do show laterally moving (or “waving”) bright rays in the supra-arcade fan of coronal rays which we interpret as due to dark supra-arcade downflows. The events are analysed in detail to determine whether the supra-arcade downflows (or the proxy waving coronal rays) occur during a) the rise and/or decay phases of the soft X-ray flare and b) the flare hard X-ray bursts. It is also investigated whether the supra-arcade downflows events show prior eruptive signatures as seen in SXT, other space-based coronal data, or reported in ground-based Hα images.
Results: A substantial majority of supra-arcade downflow events show downflows which start during the soft X-ray flare rise phase (73%), occur during hard X-ray bursts (90%), and have prior eruptive signatures associated with them (73%). However, we find a single event (2% of the total) which clearly and unambiguously showed supra-arcade downflows starting during the soft X-ray flare decay phase.
Conclusions: Since the majority of supra-arcade downflows occur during the rise phase of the soft X-ray flare and the time of hard X-ray bursts, and have prior eruptive signatures this suggests that they are related to the main flare energy release process. Furthermore, the suggested association of supra-arcade downflows with recently reconnected magnetic field lines means they may indeed be considered as evidence for a magnetic reconnection process. The single supra-arcade downflow event which unambiguously started during the decay phase of the flare occurred during hard X-ray bursts and thus appears to be related to late energy release. Title: Observations of Simultaneous Coronal Loop Shrinkage and Expansion during the Decay Phase of a Solar Flare Authors: Khan, J. I.; Fletcher, L.; Nitta, N. V. Bibcode: 2007ASPC..369..485K Altcode: We report what we believe are the first direct and unambiguous observations of simultaneous coronal magnetic flux loop shrinkage and expansion during the decay phase of a solar flare. The retracting and expanding loops were observed nearly face-on (i.e., with the loop major axis approximately orthogonal to the line of sight) in emission in imaging data from the Yohkoh Soft X-ray Telescope (SXT). The retracting loop is observed to shrink with a speed of 165±26 km s^{-1}. The faint outward moving loop-like feature occurred ∼200 arcsec above the shrinking loop during the time of the shrinking loop. We estimate the speed of the outward moving loop was ∼280±130 km s^{-1}. We interpret the shrinking loop and simultaneous outward moving loop as direct evidence for reconnected magnetic field lines during a flare. Title: Structure and Dynamics of the Little Red Spot on Jupiter Authors: Cheng, Andrew F.; Simon-Miller, A.; Weaver, H. A.; Baines, K. H.; Orton, G. S.; Yanamandra-Fisher, P. A.; Mousis, O.; Pantin, E.; Vanzi, L.; Fletcher, L. N.; Spencer, J.; Stern, A.; New Horizons Team Bibcode: 2007DPS....39.1903C Altcode: 2007BAAS...39..444C The New Horizons spacecraft obtained high resolution images of the Little Red Spot in Jupiter's atmosphere, during the New Horizons Jupiter encounter in January - March, 2007. The Little Red Spot is an Earth-sized storm that formed from the coalescence of three, 60-year old, white ovals starting in 1998 and that became clearly red in 2006. The New Horizons observations have been combined for the first time with Jupiter observations from the Very Large Telescope array in Chile and from the Hubble Space Telescope to determine the three-dimensional structure and dynamics of the Little Red Spot. Within this cold anticyclonic oval, the peak wind speeds reach 170 m/s, and the vertical gradient length, from the thermal wind equation, exceeds 90 km. Horizontal flow divergences are identified. The dynamical structure of the Little Red Spot is similar to that of the Great Red Spot. It is suggested that both spots may now persist for centuries, although the Little Red Spot attained its current state only recently. Title: Zonal Mean Dynamics On Saturn From Cassini And Voyager Data Authors: Read, Peter L.; Fletcher, L. N.; Irwin, P. G.; Achterberg, R. K.; Conrath, B. J.; Cassini CIRS Team Bibcode: 2007DPS....39.3705R Altcode: 2007BAAS...39..487R A high resolution global map of zonal mean zonal winds and potential vorticity in Saturn's upper troposphere and stratosphere has been constructed, assuming geostrophic thermal wind balance, from a combination of cloud-level winds (derived from Voyager and Cassini images) and profiles of temperature and molecular hydrogen para-fraction retrieved from measurements by the Cassini Composite InfraRed Spectrometer (CIRS) between October 2004 and March 2006. Away from the equator, the results show a clear pattern of alternating jet streams extending to polar latitudes, all of which are found to decay significantly with height between 200 and <5 hPa pressure. The equatorial jet also exhibits strong decay with height into the lower stratosphere, but with evidence of some more complex structure in the middle and upper stratosphere. Potential vorticity profiles show evidence for a hyper-staircase structure, much as found on Jupiter, though with some intriguing differences. Like Jupiter, Saturn's zonal flow appears to be close to neutral stability relative to Arnol'd's second stability theorem. This allows an estimation of the upper tropospheric Rossby deformation radius as a function of latitude, that ranges from 2000 km at high latitudes to more than 8000 km in the sub-tropics. These results will be presented and discussed in the context of their implications for global atmospheric dynamics on Saturn and the other outer planets. Title: Meridional variations in stratospheric acetylene and ethane in the southern hemisphere of the saturnian atmosphere as determined from Cassini/CIRS measurements Authors: Howett, C. J. A.; Irwin, P. G. J.; Teanby, N. A.; Simon-Miller, A.; Calcutt, S. B.; Fletcher, L. N.; de Kok, R. Bibcode: 2007Icar..190..556H Altcode: These are the first results from nadir studies of meridional variations in the abundance of stratospheric acetylene and ethane from Cassini/CIRS data in the southern hemisphere of Saturn. High resolution, 0.5 cm -1, CIRS data was used from three data sets taken in June-November 2004 and binned into 2° wide latitudinal strips to increase the signal-to-noise ratio. Tropospheric and stratospheric temperatures were initially retrieved to determine the temperature profile for each latitude bin. The stratospheric temperature at 2 mbar increased by 14 K from 9° to 68° S, including a steep 4 K rise between 60° and 68° S. The tropospheric temperatures showed significantly more meridional variation than the stratospheric ones, the locations of which are strongly correlated to that of the zonal jets. Stratospheric acetylene abundance decreases steadily from 30 to 68° S, by a factor of 1.8 at 2.0 mbar. Between 18° and 30° S the acetylene abundance increases at 2.0 mbar. Global values for acetylene have been calculated as (1.9±0.19)×10 at 2.0 mbar, (2.6±0.27)×10 at 1.6 mbar and (3.1±0.32)×10 at 1.4 mbar. Global values for ethane are also determined and found to be (1.6±0.25)×10 at 0.5 mbar and (1.4±0.19)×10 at 1.0 mbar. Ethane abundance in the stratosphere increases towards the south pole by a factor of 2.5 at 2.0 mbar. The increase in stratospheric ethane is especially pronounced polewards of 60° S at 2.0 mbar. The increase of stratospheric ethane towards the south pole supports the presence of a meridional wind system in the stratosphere of Saturn. Title: The 2007 Jupiter's North Temperate Belt Disturbance: I. Overview and jet stream changes. Authors: Sanchez-Lavega, Agustin; Orton, G. S.; Hueso, R.; Garcia-Melendo, E.; Perez-Hoyos, S.; Simon-Miller, A.; Rojas, J. F.; Gomez, J. M.; Yanamandra-Fisher, P. A.; Fletcher, L.; Joels, J.; Kemerer, J.; Hora, J.; Karkoschka, E.; de Pater, I.; Wong, M. H.; Marcus, P. S.; Pinilla, N.; International Outer Planet Watch (IOPW) Bibcode: 2007DPS....39.0104S Altcode: 2007BAAS...39S.407S Changes in belts and zones of Jupiter are sometimes virulent, starting from a localized eruption followed by the development of a planetary scale disturbance. The archetype of this phenomenology occurs rarely, about once every fifteen years, at 23° North latitude where the highest speed Jovian jet stream resides. In late March 2007 two nearly simultaneous eruptions of bright plumes separated by 63,000 km (55° longitude) occurred in the peak of the jet, causing a new disturbance. Here we present detailed observations of the disturbance onset and evolution, and of the related changes and deep extent of the jet based on Hubble Space Telescope images and ground-based observations in the visible and near infrared. The plumes reached a height elevation of 30 km relative to background clouds and, moving faster eastward than any other feature in the planet at about 165 m/s, generated a turbulent and complex periodic pattern in their wake, injecting a large amount of red aerosols. Only small changes were detected in the jet wind velocity profile as measured before the disturbance and after its dissipation. Radiative transfer of cloud vertical structure, mesoscale models of the plumes and a general circulation model of the turbulent pattern require the jet stream to be robust extending down to at least 5-7 bar pressure, the base of the water clouds, well below the sunlight penetration level.

Acknowledgments: this work was supported by the Spanish MEC-PNAYA. We acknowledge the HST director's discretionary time (GO/DD11310) for June 5 observations. And GO/DD10782 for March 08 and May 11 data. Title: Spaceward Bound: Field Training for the Next Generation of Space Explorers Authors: McKay, C. P.; Coe, L. K.; Battler, M.; Bazar, D.; Conrad, L.; Day, B.; Fletcher, L.; Green, R.; Heldmann, J.; Muscatello, T.; Rask, J. C.; Smith, H.; Sun, H.; Zubrin, R. Bibcode: 2007LPICo1371.3028M Altcode: 2007eelo.work.3028M No abstract at ADS Title: Observations of Jupiter Supporting the New Horizons Encounter and During a Period of "Global Upheaval" Authors: Orton, Glenn S.; Yanamandra-Fisher, P. A.; Baines, K. H.; Momary, T.; Mousis, O.; Vanzi, L.; Hayward, T.; DeBuizer, J.; Simon-Miller, A.; Bjoraker, G.; Fletcher, L.; Edkins, E.; Joels, J.; Kemerer, J.; Parrish, P. Bibcode: 2007DPS....39.0103O Altcode: 2007BAAS...39..407O Multi-spectral observations of Jupiter obtained between February and September of 2007 provided both increased spectral support and an extended timeline for the New Horizons remote-sensing of its atmosphere. The observations also tracked a series of rapid changes in Jupiter's atmosphere. Data were acquired at NASA's Infrared Telescope Facility (MIRSI, NSFCam2 and SpeX), Gemini/South (T-ReCS), ESO's Very Large Telescope (VISIR) and Lick observatory (the Aerospace VNIRIS spectrometer). Mid-infrared observations from the large telescopes optimized spatial resolution in the mid-infrared by minimizing the effects of diffraction. In mid-February, the north and south auroral-generated stratospheric hot spots were resolved spatially, possibly for the first time; the southern one being bright in methane, ethylene and ethane emission. In contrast, the northern one was recognizable in all of these emissions, but barely above the background level. Subsequent observation in March and later did not detect any enhanced emission from the north. Observations of polar regions provided evidence of distinct boundaries to polar airmasses which coincided with the locations of high-altitude haze layers. These high-resolution images revealed that temperatures in the interior of the Great Red Spot were not elliptically symmetric but were warmer to the south and center of the vortex. Observations from March to June coincided with the initiation of several vertical jets in the southern portion of Jupiter's North Temperate Belt (NTBs), which precede a major color change in the entire belt and often signal the beginning of an epoch of "global upheaval" in Jupiter's cloud system with major disruptions to its typical appearance. Observations from May through this writing tracked the initiation of similar weaker jets in the southern portion of the South Equatorial Belt (SEBs). Our observations determine the altitude of these outbursts, and their influence on the temperature field and the distribution of para-hydrogen and ammonia. Title: Saturn's South Polar Vortex: A Possible Gas-Giant Analog to a Terrestrial Hurricane Authors: Dyudina, Ulyana A.; Ingersoll, A. P.; Ewald, S. P.; Vasavada, A. R.; West, R. A.; Del Genio, A.; Barbara, J.; Porco, C. C.; Porco, C. C.; Achterberg, R. K.; Flasar, F. M.; Simon-Miller, A. A.; Fletcher, L. N. Bibcode: 2007DPS....39.3709D Altcode: 2007BAAS...39..488D Observations made by the Cassini spacecraft reveal a large, long-lived vortex anchored to the south pole of Saturn that shares many properties with terrestrial hurricanes. Among these are: a central eye with cyclonic vorticity, an outer region where vorticity is near zero, a warm temperature anomaly within the eye, concentric eyewall clouds that extend two pressure scale heights above the clouds within the eye, numerous small clouds whose anticyclonic vorticity suggests a convective origin, and evidence, at high altitudes, of excess cyclonic rotation not balanced by the inward pressure force, implying outward flow. Besides differences of scale, the main distinctions between hurricanes on Earth and the one seen on Saturn are the static, polar location of the latter and the lack of a liquid ocean to support it. This is the first hurricane-like vortex detected on a planet other than Earth. Title: Condensation during Titan's Polar Winter Authors: de Kok, Remco; Irwin, P. G.; Teanby, N. A.; Fletcher, L. N.; Howett, C. J.; Calcutt, S. B.; Bowles, N. E.; Taylor, F. W. Bibcode: 2007DPS....39.5611D Altcode: 2007BAAS...39..530D Titan is currently experiencing winter in its northern hemisphere and the lower atmosphere of its north polar region has been in prolonged darkness since the solstice in October 2002. As a result, the north polar region is currently characterised by cold stratospheric temperatures and there is enrichment of trace gases due to downward atmospheric motion (e.g. Teanby et al., Icarus 181 pp. 243-255, 2006). These conditions make the polar winter very suitable for cloud formation in the stratosphere.

A simple transport and condensation model has been made to explore condensation processes in Titan's northern stratosphere. In the model, the atmosphere is advected downwards and clouds are formed as the saturation pressure of various gases is reached. Upper limits of the gases C4N2 and propionitrile (C2H5CN) were determined from Cassini Composite Infrared Spectrometer data to assess scenarios of chemical disequilibrium where the gas phase is far less abundant than the solid phase. The upper limit for C4N2 is 9e-9, which discounts the massive C4N2 build-up in the polar winter proposed by Samuelson et al. (PSS 45, pp. 941-948, 1997) to explain the observed C4N2 cloud at the Voyager epoch. The propionitrile upper limit is 8e-9, which is several orders of magnitude less than needed to create the condensate feature at 220 cm-1 of Khanna (Icarus 177, pp. 116-121) and de Kok et al. (Icarus, in press), assuming it is propionitrile ice, under the steady-state conditions explored by the aformentioned model. HCN ice seems to play an important role in the formation of a massive polar cloud (Haze B in de Kok et al., Icarus, in press), because of the unavailability of sufficient condensable gas other than HCN (and possibly HC3N) to produce the condensate features seen in far-infrared spectra at 220 cm-1. Title: Jovian Wind Periodicity Revisited Authors: Tsavaris, Irene; Simon-Miller, A. A.; Orton, G. S.; Fisher, B.; Yanamandra-Fisher, P. A.; Parrish, P.; Fletcher, L.; Joels, J. Bibcode: 2007DPS....39.1906T Altcode: 2007BAAS...39..445T Prior analysis of Jupiter's zonal wind field offered slight evidence of periodicity on short time scales, though time coverage was marginal (Simon-Miller et al. 2007 Icarus 186, 192-203). Though the winds are measured through tracking of tropospheric clouds, it was hoped that some relation could be found between stratospheric temperature oscillations (the Quasi-Quadrennial Oscillation) and tropospheric winds. However, complicating the analysis was the fact that the pressure levels of the tracked cloud features are unknown, and are spatially and temporally variable. Thermal wind analysis for a few of the dates showed cloud level variations could easily account for most of the wind speed variability, except at 7 deg. S latitude. New images, acquired in 2006 and 2007, have allowed the extension of the zonal wind time base, improving the periodogram analysis. We will present results based on our newest zonal wind and temperature profiles. Title: Characterising Saturn's vertical temperature structure from Cassini/CIRS Authors: Fletcher, L. N.; Irwin, P. G. J.; Teanby, N. A.; Orton, G. S.; Parrish, P. D.; de Kok, R.; Howett, C.; Calcutt, S. B.; Bowles, N.; Taylor, F. W. Bibcode: 2007Icar..189..457F Altcode: Thermal infrared spectra of Saturn from 10-1400 cm -1 at 15 cm -1 spectral resolution and a spatial resolution of 1°-2° latitude have been obtained by the Cassini Composite Infrared Spectrometer [Flasar, F.M., and 44 colleagues, 2004. Space Sci. Rev. 115, 169-297]. Many thousands of spectra, acquired over eighteen-months of observations, are analysed using an optimal estimation retrieval code [Irwin, P.G.J., Parrish, P., Fouchet, T., Calcutt, S.B., Taylor, F.W., Simon-Miller, A.A., Nixon, C.A., 2004. Icarus 172, 37-49] to retrieve the temperature structure and para-hydrogen distribution over Saturn's northern (winter) and southern (summer) hemispheres. The vertical temperature structure is analysed in detail to study seasonal asymmetries in the tropopause height (65-90 mbar), the location of the radiative-convective boundary (350-500 mbar), and the variation with latitude of a temperature knee (between 150 and 300 mbar) which was first observed in inversions of Voyager/IRIS spectra [Hanel, R., and 15 colleagues, 1981. Science 212, 192-200; Hanel, R., Conrath, B., Flasar, F.M., Kunde, V., Maguire, W., Pearl, J.C., Pirraglia, J., Samuelson, R., Cruikshank, D.P., Gautier, D., Gierasch, P.J., Horn, L., Ponnamperuma, C., 1982. Science 215, 544-548]. Uncertainties due to both the modelling of spectral absorptions (collision-induced absorption coefficients, tropospheric hazes, helium abundance) and the nature of our retrieval algorithm are quantified. Temperatures in the stratosphere near 1 mbar show a 25-30 K temperature difference between the north pole and south pole. This asymmetry becomes less pronounced with depth as the radiative time constant for the atmospheric response increases at deeper pressure levels. Hemispherically-symmetric small-scale temperature structures associated with zonal winds are superimposed onto the temperature asymmetry for pressures greater than 100 mbar. The para-hydrogen fraction in the 100-400 mbar range is greater than equilibrium predictions for the southern hemisphere and parts of the northern hemisphere, and less than equilibrium predictions polewards of 40° N. The temperature knee between 150-300 mbar is larger in the summer hemisphere than in the winter, smaller and higher at the equator, deeper and larger in the equatorial belts and small at the poles. Solar heating on tropospheric haze is proposed as a possible mechanism for this effect; the increased efficiency of ortho- to para-hydrogen conversion in the southern hemisphere is consistent with the presence of larger aerosols in the summer hemisphere, which we demonstrate to be qualitatively consistent with previous studies of Saturn's tropospheric aerosol distribution. Title: Observations of Jupiter supporting the New Horizons encounter and at the onset of a period of "global upheaval" Authors: Orton, G.; Yanamandra-Fisher, P.; Baines, K.; Mousis, O.; Vanzi, L.; Hayward, T.; De Buizer, J.; Simon-Miller, A.; Bjoraker, G.; Fletcher, L.; Edkins, E.; Kemerer, J. Bibcode: 2007epsc.conf..611O Altcode: Observations of Jupiter were made between February and June of 2007 to provide both increased spectral support and an extended timeline for the New Horizons remotesensing of Jupiter's atmosphere. Several ground-based facilities were used, using the NASA Infrared Telescope Facility (MIRSI and NSFCam2 mid- and near-infrared instruments, respectively), Gemini/South (T-Recs mid-infrared camera/spectrometer), and ESO's Very Large Telescope (VISIR mid-infrared camera/spectrometer). Midinfrared observations from the large telescopes provide the maximum possible spatial resolution in the mid-infrared, as the point-response function is primarily defined by the limitations of diffraction rather than atmospheric turbulence. In mid-February, the north and south auroral-generated stratospheric hot spots were resolved spatially, possibly for the first time; the southern one being bright in methane, ethylene and ethane emission. In contrast, the northern one was recognizable in all of these emissions, but barely above the background level. Subsequent observations in March and thereafter did not detect any enhanced emission from the north. Observations of polar regions provided evidence of distinct boundaries to polar airmasses which coincided with the locations of high-altitude haze layers. These high-resolution images revealed that temperatures in the interior of the Great Red Spot were not elliptically symmetric but were warmer to the south and center of the vortex. Observations from March to June coincided with the initiation of several vertical jets in the southern portion of Jupiter's North Temperate Belt (NTBs), which precede a major color change in the entire belt and often signal the beginning of an epoch of "global upheaval" in Jupiter's cloud system with major disruptions to its typical appearance. Our observations determine the altitude of these outbursts and their influence on the temperature field. Title: Solar active region emergence and flare productivity Authors: Dalla, Silvia C.; Fletcher, Lyndsay; Walton, Nicholas A. Bibcode: 2007HiA....14..614D Altcode: 2006IAUSS...3E..45D We use the workflow capabilities of the AstroGrid Virtual Observatory system (<http://www.astrogrid.org>) to analyse the relation between flare productivity and location of Active Region (AR) emergence on the Sun. Specifically, we investigate whether emergence of a new region near existing ones results in increased productivity of the new and/or pre-existing AR. To address this question, we build a series of workflows that perform queries to catalogues of regions and flares, and operations on the results of the queries. There is a strong East-West asymmetry in the location of emergence of new regions. We do not find a significant difference between the flaring rate of paired and isolated regions, when we choose a value of 12° as the cutoff between the two populations. Title: Flare productivity of newly-emerged paired and isolated solar active regions Authors: Dalla, S.; Fletcher, L.; Walton, N. A. Bibcode: 2007A&A...468.1103D Altcode: Aims:We investigate whether sunspot regions that emerge near existing ones are more flare productive than those that emerge isolated.
Methods: We analyse a sample of 2115 new regions obtained from the USAF/Mount Wilson catalogue of sunspot regions. For our analysis we use AstroGrid, a Virtual Observatory developed in the UK, to build a series of workflows that perform queries to catalogues of solar regions and flares, and operations on the results of the queries. If a new region emerged through the solar surface within 12° of a pre-existing one, we classify it as paired, otherwise as isolated.
Results: We find that paired regions are more flare productive than isolated ones, although this is a small effect. Here only soft X-ray flares of magnitude greater than C1.0 are considered, and flare productivity is characterised by the percentage of regions that produced at least one flare over 4 days since emergence, and by the average number of flares over the same period. For paired regions, we also consider the flare productivity of the nearby companion region and find that if a flare does happen within the pair, it will more likely take place in the companion region than in the newly-emerged one. Our results show that although emergence in proximity to another region can slightly increase the probability of a flare taking place, presumably by increasing the likelihood of magnetic reconnection and significant change in magnetic topology, this is not a large effect. It appears that intrinsic properties of the region are the key factor in determining whether or not it will produce flares, as opposed to interaction with pre-existing regions. Title: Energy Deposition in White Light Flares with TRACE and RHESSI Authors: Fletcher, L.; Hannah, I. G.; Hudson, H. S.; Metcalf, T. R. Bibcode: 2007ASPC..368..423F Altcode: In Fletcher et al. (2007) we investigated the white light (WL) continuum during solar flares and its relationship to energy deposition by electron beams. In 9 flare events, spanning GOES classifications from C4.8 to M9.1, we have high cadence TRACE WL and RHESSI hard X-ray observations, and compare the WL radiative power output with that provided by flare electrons. Under the thick--target model assumptions, we find that the electron beam must extend down to 15--20 keV, and the energy input to the chromosphere should occur within the collisional stopping depth of these electrons - approximately 2× 10-4 g cm-2. In this short paper, we discuss some ideas on flare WL emission, summarise the results of the Fletcher et al. (2007) study and discuss their implications for chromospheric heating and white light flare emission. Title: Electron Acceleration By Inertial Alfven Waves In The Impulsive Phase Of A Solar Flare Authors: Hudson, Hugh S.; Fletcher, L. Bibcode: 2007AAS...210.9303H Altcode: 2007BAAS...39R.211H The impulsive phase of a solar flare marks the epoch of rapid conversion of energy stored in the pre-flare coronal magnetic field. Hard X-ray observations imply that a substantial fraction of flare energy released during the impulsive phase is converted to the kinetic energy of mildly relativistic electrons (10-100 keV). The liberation of the magnetic free energy occurs as the coronal magnetic field reconfigures and relaxes following reconnection. Therefore, we investigate a scenario in which the electron acceleration is caused by the agents of this reconfiguration -- the large-scale Alfven waves which propagate the field changes throughout the atmosphere. In a plasma with β < me/mp, these waves propagate as inertial Alfven waves which, in the presence of strong spatial gradients, generate field-aligned electric fields that can accelerate electrons to energies on the order of 10 keV and above. This novel view also provides an interpretation of the recently-observed rapid variations of the line-of-sight component of the photospheric magnetic field during the flare impulsive phase, and offers solutions to some perplexing flare problems, such as the flare “number problem” of finding sufficient and resupplying sufficient electrons to explain the impulsive-phase hard X-ray emission. Title: The meridional phosphine distribution in Saturn's upper troposphere from Cassini/CIRS observations Authors: Fletcher, L. N.; Irwin, P. G. J.; Teanby, N. A.; Orton, G. S.; Parrish, P. D.; Calcutt, S. B.; Bowles, N.; de Kok, R.; Howett, C.; Taylor, F. W. Bibcode: 2007Icar..188...72F Altcode: The Cassini Composite Infrared Spectrometer (CIRS) has been used to derive the vertical and meridional variation of temperature and phosphine (PH 3) abundance in Saturn's upper troposphere. PH 3 has a significant effect on the measured radiances in the thermal infrared and between May 2004 and September 2005 CIRS recorded thousands of spectra in both the far (10-600 cm -1) and mid (600-1400 cm -1) infrared, at a variety of latitudes covering the southern hemisphere. Low spectral resolution (15 cm -1) data has been used to constrain the temperature structure of the troposphere between 100 and 500 mbar. The vertical distributions of phosphine and ammonia were retrieved from far-infrared spectra at the highest spectral resolution (0.5 cm -1), and lower resolution (2.5 cm -1) mid-infrared data were used to map the meridional variation in the abundance of phosphine in the 250-500 mbar range. Temperature variations at the 250 mbar level are shown to occur on the same scale as the prograde and retrograde jets in Saturn's atmosphere [Porco, C.C., and 34 colleagues, 2005. Science 307, 1243-1247]. The PH 3 abundance at 250 mbar is found to be enhanced at the equator when compared with mid-latitudes. At mid latitudes we see anti-correlation between temperature and PH 3 abundance at 250 mbar, phosphine being enhanced at 45° S and depleted at 25 and 55° S. The vertical distribution is markedly different polewards of 60-65° S, with depleted PH 3 at 500 mbar but a slower decline in abundance with altitude when compared with the mid-latitudes. This variation is similar to the variations of cloud and aerosol parameters observed in the visible and near infrared, and may indicate the subsidence of tropospheric air at polar latitudes, coupled with a diminished sunlight penetration depth reducing the rate of PH 3 photolysis in the polar region. Title: Birth and evolution of a dense coronal loop in a complex flare region Authors: Bone, L.; Brown, J. C.; Fletcher, L.; Veronig, A.; White, S. Bibcode: 2007A&A...466..339B Altcode: Context: During the 14th/15th of April 2002, several flares occurred in NOAA active region complex 9893/9910. Two of these were previously interpreted as having anomalously high coronal column densities.
Aims: We develop a scenario using multiwavelength observations to explain the high coronal column density (≈1020 cm-2) present at the onset of the 14th April 2002 M3.7 hard X-ray event.
Methods: Prior to this event a series of flares occurred in close temporal and spatial proximity. We observe the sequence of flares in a multiwavelength regime from radio to hard X-rays. This allows us to study the particle acceleration and plasma evaporation in these events.
Results: The observations of these flares lead us to propose a sequence of reconnections between multiple systems of loops in a 3 dimensional field geometry. We suggest that the dense loops in the M3.7 event can be explained as being already filled with plasma from the earlier events; these loops then themselves become unstable or reconnect leading to particle acceleration into an overdense coronal environment. We explore the possibility that a high-beta disruption is behind the instability of these dense loops, leading to the 14th April 2002 M3.7 event and the observation of hard X-rays in the corona at energies up to ≈50 keV. Title: Fast Alfvén Wave Heating and Acceleration of Ions in a Nonuniform Magnetoplasma Authors: McKay, R. J.; McClements, K. G.; Fletcher, L. Bibcode: 2007ApJ...658..631M Altcode: A test-particle approach is used to study the collisionless response of protons to cold plasma fast Alfvén waves propagating in a nonuniform magnetic field: specifically, a two-dimensional X-point field. The field perturbations associated with the waves, which are assumed to be azimuthally symmetric and invariant in the direction orthogonal to the X-point plane, are exact solutions of the linearized ideal magnetohydrodynamic (MHD) equations. The protons are initially Maxwellian, at temperatures that are consistent with the cold plasma approximation. Two kinds of wave solution are invoked: global perturbations, with inward- and outward-propagating components; and localized purely inward-propagating waves, the wave electric field E having a preferred direction. In both cases the protons are effectively heated in the direction parallel to the magnetic field, although the parallel velocity distribution is generally non-Maxwellian and some protons are accelerated to highly suprathermal energies. This heating and acceleration can be attributed to the fact that protons undergoing EXB drifts due to the presence of the wave are subject to a force in the direction parallel to B. The localized wave solution produces more effective proton heating than the global solution, and successive wave pulses have a synergistic effect. This process, which could play a role in both solar coronal heating and late-phase heating in solar flares, is effective for all ion species, but it has a negligible direct effect on electrons. However, both electrons and heavy ions would be expected to acquire a temperature comparable to that of the protons on collisional timescales. Title: Spaceward Bound: Field Training for the Next Generation of Space Explorers Authors: McKay, C. P.; Coe, L. H.; Battler, M.; Bazar, D.; Boston, P.; Conrad, L.; Day, B.; Fletcher, L.; Graham, P.; Green, R.; Heldmann, J.; Muscatello, T.; Rask, J.; Smith, H.; Sun, H.; Zubrin, R. Bibcode: 2007LPI....38.1467M Altcode: Spaceward Bound is an educational program developed at NASA Ames in partnership with The Mars Society, and funded by the Exploration Systems Mission Directorate (ESMD) at NASA Headquarters. Title: Oxygen compounds in Titan's stratosphere as observed by Cassini CIRS Authors: de Kok, R.; Irwin, P. G. J.; Teanby, N. A.; Lellouch, E.; Bézard, B.; Vinatier, S.; Nixon, C. A.; Fletcher, L.; Howett, C.; Calcutt, S. B.; Bowles, N. E.; Flasar, F. M.; Taylor, F. W. Bibcode: 2007Icar..186..354D Altcode: We have investigated the abundances of Titan's stratospheric oxygen compounds using 0.5 cm-1 resolution spectra from the Composite Infrared Spectrometer on the Cassini orbiter. The CO abundance was derived for several observations of far-infrared nadir spectra, taken at a range of latitudes (75° S-35° N) and emission angles (0°-60°), using rotational lines that have not been analysed before the arrival of Cassini at Saturn. The derived volume mixing ratios for the different observations are mutually consistent regardless of latitude. The weighted mean CO volume mixing ratio is 47±8 ppm if CO is assumed to be uniform with latitude. H2O could not be detected and an upper limit of 0.9 ppb was determined. CO2 abundances derived from mid-infrared nadir spectra show no significant latitudinal variations, with typical values of 16±2 ppb. Mid-infrared limb spectra at 55° S were used to constrain the vertical profile of CO2 for the first time. A vertical CO2 profile that is constant above the condensation level at a volume mixing ratio of 15 ppb reproduces the limb spectra very well below 200 km. This is consistent with the long chemical lifetime of CO2 in Titan's stratosphere. Above 200 km the CO2 volume mixing ratio is not well constrained and an increase with altitude cannot be ruled out there. Title: A TRACE White Light and RHESSI Hard X-Ray Study of Flare Energetics Authors: Fletcher, L.; Hannah, I. G.; Hudson, H. S.; Metcalf, T. R. Bibcode: 2007ApJ...656.1187F Altcode: In this paper we investigate the formation of the white-light (WL) continuum during solar flares and its relationship to energy deposition by electron beams inferred from hard X-ray emission. We analyze nine flares spanning GOES classifications from C4.8 to M9.1, seven of which show clear cospatial RHESSI hard X-ray and TRACE WL footpoints. We characterize the TRACE WL/UV continuum energy under two simplifying assumptions: (1) a blackbody function, or (2) a Paschen-Balmer continuum model. These set limits on the energy in the continuum, which we compare with that provided by flare electrons under the usual collisional thick-target assumptions. We find that the power required by the white-light luminosity enhancement is comparable to the electron beam power required to produce the HXR emission only if the low-energy cutoff to the spectrum is less than 25 keV. The bulk of the energy required to power the white-light flare (WLF) therefore resides at these low energies. Since such low-energy electrons cannot penetrate deep into a collisional thick target, this implies that the continuum enhancement is due to processes occurring at moderate depths in the chromosphere. Title: Vertical profiles of HCN, HC 3N, and C 2H 2 in Titan's atmosphere derived from Cassini/CIRS data Authors: Teanby, N. A.; Irwin, P. G. J.; de Kok, R.; Vinatier, S.; Bézard, B.; Nixon, C. A.; Flasar, F. M.; Calcutt, S. B.; Bowles, N. E.; Fletcher, L.; Howett, C.; Taylor, F. W. Bibcode: 2007Icar..186..364T Altcode: Mid-infrared limb spectra in the range 600-1400 cm-1 taken with the Composite InfraRed Spectrometer (CIRS) on-board the Cassini spacecraft were used to determine vertical profiles of HCN, HC3N, C2H2, and temperature in Titan's atmosphere. Both high (0.5 cm-1) and low (13.5 cm-1) spectral resolution data were used. The 0.5 cm-1 data gave profiles at four latitudes and the 13.5 cm-1 data gave almost complete latitudinal coverage of the atmosphere. Both datasets were found to be consistent with each other. High temperatures in the upper stratosphere and mesosphere were observed at Titan's northern winter pole and were attributed to adiabatic heating in the subsiding branch of a meridional circulation cell. On the other hand, the lower stratosphere was much colder in the north than at the equator, which can be explained by the lack of solar radiation and increased IR emission from volatile enriched air. HC3N had a vertical profile consistent with previous ground based observations at southern and equatorial latitudes, but was massively enriched near the north pole. This can also be explained in terms of subsidence at the winter pole. A boundary observed at 60° N between enriched and un-enriched air is consistent with a confining polar vortex at 60° N and HC3N's short lifetime. In the far north, layers were observed in the HC3N profile that were reminiscent of haze layers observed by Cassini's imaging cameras. HCN was also enriched over the north pole, which gives further evidence for subsidence. However, the atmospheric cross section obtained from 13.5 cm-1 data indicated a HCN enriched layer at 200-250 km, extending into the southern hemisphere. This could be interpreted as advection of polar enriched air towards the south by a meridional circulation cell. This is observed for HCN but not for HC3N due to HCN's longer photochemical lifetime. C2H2 appears to have a uniform abundance with altitude and is not significantly enriched in the north. This is consistent with observations from previous CIRS analysis that show increased abundances of nitriles and hydrocarbons but not C2H2 towards the north pole. Title: A Magnetometer For The Solar Orbiter Mission Authors: Carr, C. M.; Horbury, T. S.; Balogh, A.; Baumjohann, W.; Bavassano, B.; Breen, A.; Burgess, D.; Cargill, P. J.; Brooker, N.; Erdõs, G.; Fletcher, L.; Forsyth, R. J.; Giacalone, J.; Glassmeier, K. -H.; Hoeksema, J. T.; Goldstein, M. L.; Lockwood, M.; Magnes, W.; Masimovic, M.; Marsch, G.; Matthaeus, W. H.; Murphy, N.; Nakariakov, V. M.; Pacheco, J. R.; Pincon, J. -L.; Riley, P.; Russell, C. T.; Schwartz, S. J.; Szabo, A.; Thompson, M.; Vainio, R.; Velli, M.; Vennerstrom, S.; Walsh, R.; Wimmer-Schweingruber, R.; Zank, G. Bibcode: 2007ESASP.641E..41C Altcode: The magnetometer is a key instrument to the Solar Orbiter mission. The magnetic field is a fundamental parameter in any plasma: a precise and accurate measurement of the field is essential for understanding almost all aspects of plasma dynamics such as shocks and stream-stream interactions. Many of Solar Orbiter's mission goals are focussed around the links between the Sun and space. A combination of in situ measurements by the magnetometer, remote measurements of solar magnetic fields and global modelling is required to determine this link and hence how the Sun affects interplanetary space. The magnetic field is typically one of the most precisely measured plasma parameters and is therefore the most commonly used measurement for studies of waves, turbulence and other small scale phenomena. It is also related to the coronal magnetic field which cannot be measured directly. Accurate knowledge of the magnetic field is essential for the calculation of fundamental plasma parameters such as the plasma beta, Alfvén speed and gyroperiod. We describe here the objectives and context of magnetic field measurements on Solar Orbiter and an instrument that fulfils those objectives as defined by the scientific requirements for the mission. Title: New upper limits for hydrogen halides on Saturn derived from Cassini-CIRS data Authors: Teanby, N. A.; Fletcher, L. N.; Irwin, P. G. J.; Fouchet, T.; Orton, G. S. Bibcode: 2006Icar..185..466T Altcode: Far infrared spectra (10-600 cm -1) from Cassini's Composite InfraRed Spectrometer (CIRS) were used to determine improved upper limits of hydrogen halides HF, HCl, HBr, and HI in Saturn's atmosphere. Three observations, comprising a total of 3088 spectra, gave 3 σ upper limits on HF, HCl, HBr, and HI volume mole fractions of 8.0×10, 6.7×10, 1.3×10, and 1.4×10, respectively, at the 500 mbar pressure level. These upper limits confirm sub-solar abundances of halide species for HF, HCl, and HBr in Saturn's upper atmosphere—consistent with predictions from thermochemical models and influx of material from meteoroids. Our upper limit for HCl is 16 times lower than the tentative detection at 1.1×10 reported by Weisstein and Serabyn [Weisstein, E.W., Serabyn, E., 1996. Icarus 123, 23-36]. These observations are not sensitive to the deep halide abundance, which is expected to be enriched relative to the solar composition. Title: Comparison of Earth-Based Longitudinal Studies and Cassini CIRS Observations of Saturn's Temperature Field: Modifications of Seasonal Forcing Models and the Discovery of Nonseasonal Low-Latitude Thermal Oscillations Authors: Orton, G.; Parrish, P.; Yanamandra-Fisher, P.; Fisher, B.; Fletcher, L.; Irwin, P.; Nelson, J.; Gezari, D.; Fuse, T.; Fujiyoshi, T. Bibcode: 2006AGUFM.P41C1306O Altcode: During the sequence of observations made by Cassini CIRS from 2004 to the present, supporting observations of Saturn have been made in the same spectral region. Most of these were taken at NASA's 3-m Infrared Telescope Facility (IRTF), but they were supplemented by observations from the 8.2-m Subaru Telescope. An examination of temperature field retrieved from form spacecraft and earth-based observations has required us to assess carefully the limitation of vertical sensitivity for the ground-based images and the calibration of both geometry and absolute radiance. Keeping those limitations in mind, the combination of the two data sets has provided evidence that is consistent with the absence of effective cloud opacity in the mid- and far-infrared. Furthermore, the full sequence of ground-based imaging stretches back as early as 1990. These observations clearly indicate the expected hemispherically antisymmetric seasonal forcing, but with relaxation times considerably shorter than the 9-year scales in both the stratosphere and upper troposphere expected from gaseous constituents alone. An important non- seasonal effect was also noted in the long-term behavior of the equator and low-latitude regions which undergo a periodic oscillation with an alternating phases of thermal waves at the equator and at latitudes 5-25 degrees poleward in both hemispheres over a period of 20 years or longer. The observed behavior is consistent with the different stratospheric temperature profiles of these regions. This phenomenon is best explained by the presence of upwelling thermal waves which are similar to the Earth's quasi-biennial oscillation (QBO) and Jupiter's quasi-quadrennial oscillation (QQO). Title: Solar And Cosmic Ray Physics And The Space Environment: Studies For And With LISA Authors: Shaul, D. N. A.; Aplin, K. L.; Araújo, H.; Bingham, R.; Blake, J. B.; Branduardi-Raymont, G.; Buchman, S.; Fazakerley, A.; Finn, L. S.; Fletcher, L.; Glover, A.; Grimani, C.; Hapgood, M.; Kellet, B.; Matthews, S.; Mulligan, T.; Ni, W. -T.; Nieminen, P.; Posner, A.; Quenby, J. J.; Roming, P.; Spence, H.; Sumner, T.; Vocca, H.; Wass, P.; Young, P. Bibcode: 2006AIPC..873..172S Altcode: With data analysis preparations for LISA underway, there has been renewed interest in studying solar, cosmic ray and environmental physics for, and using LISA. The motivation for these studies is two fold. The primary incentive is to predict and consequently minimize the impact of disturbances associated with these factors, to maximize LISA's gravitational wave scientific yield. The second stimulus is the unique opportunity that is afforded by LISA's long-baseline 3-spacecraft configuration for studies of solar, cosmic ray and environmental physics. Here we present an overview of recent progress in these studies. Title: Optimal filtering of solar images using soft morphological processing techniques Authors: Marshall, S.; Fletcher, L.; Hough, K. Bibcode: 2006A&A...457..729M Altcode: Context: .CCD images obtained by space-based astronomy and solar physics are frequently spoiled by galactic and solar cosmic rays, and particles in the Earth's radiation belt, which produces an overlaid, often saturated, speckle.
Aims: .We describe the development and application of a new image-processing technique for the removal of this noise source, and apply it to SOHO/LASCO coronagraph images.
Methods: .We employ soft morphological filters, a branch of non-linear image processing originating from the field of mathematical morphology, which are particularly effective for noise removal.
Results: .The soft morphological filters result in a significant improvement in image quality, and perform significantly better than other currently existing methods based on frame comparison, thresholding, or simple morphologies.
Conclusions: .This is a promising and adaptable technique that should be extendable to other space-based solar and astronomy datasets. Title: Titan's Stratospheric Aerosols and Condensate Clouds as Observed with Cassini CIRS Authors: de Kok, Remco; Irwin, P. G.; Teanby, N. A.; Samuelson, R. E.; Nixon, C. A.; Jennings, D. E.; Fletcher, L.; Howett, C.; Calcutt, S. B.; Bowles, N. E.; Flasar, F. M.; Taylor, F. W.; Cassini/CIRS Team Bibcode: 2006DPS....38.2203D Altcode: 2006BAAS...38R.519D Four broad spectral features were identified in far-infrared limb spectra from the Cassini Composite Infrared Spectrometer (CIRS). The features are broader than the spectral resolution, which suggests that they are caused by particulates in Titan's stratosphere. We derive here the spectral properties and variations with altitude and latitude for these four features. Titan's main aerosol is called Haze 0 here. It is present at all wavenumbers in the far-infrared and is found to have a fractional scale height between 1.6-1.7 with a small increase in opacity in the north. A second feature around 140 cm-1 (Haze A) has similar spatial properties to Haze 0, but has a smaller fractional scale height of 1.2-1.3. Both Haze 0 and Haze A show an increase in abundance below 100 km, perhaps indicative of a scattering cloud. Two other features (Haze B around 220 cm-1 and Haze C around 190 cm-1) have a large maximum in their density profiles at 140 km and 90 km respectively. Haze B is much more abundant in the northern hemisphere compared to the southern hemisphere. Haze C also shows a large increase towards the north, but then disappears at 85oN. This work is supported by the Prins Bernhard Cultuurfond and Pieter Beijer Fonds. Title: Variations In The Abundance Of Acetylene And Ethane In The Atmosphere Of Saturn, As Deduced From Cassini/CIRS And IRTF/MIRI Measurements. Authors: Howett, Carly; Irwin, P.; Yanamandra-Fisher, P.; Parrish, P.; Orton, G.; Fletcher, L.; Teanby, N.; CIRS Team Bibcode: 2006DPS....38.3907H Altcode: 2006BAAS...38..555H High resolution data taken by Cassini/CIRS from June to November 2004 are analysed to deduce variations in the abundance of acetylene and ethane. The data has good spatial coverage of Saturn's southern latitudes covering 5 to 80 S, binned by latitude into strips of 2 degrees. Tropospheric and stratospheric temperatures are initially deduced using the hydrogen S(1) continuum and the methane v4 band. Using the retrieved temperature profiles latitudinal variations in the abundance of acetylene and ethane are determined using the v5 band of acetylene and the v9 band of ethane.

These results are compared with ground-based observations of Saturn taken with MIRSI on the IRTF in January and February 2006. Temperature profiles are derived from fitting the hydrogen S(1) continuum and the methane v4 band. Variations in the abundance of the two hydrocarbons are then determined using the R branch of the v5 band of acetylene and the v9 band of ethane.

This research was funded by the UK Particle Physics and Astronomy Research Council and the NASA Cassini Project. Title: The Vortex Formerly Known as White Oval BA: Temperature Structure, CloudProperties and Dynamical Simulation Authors: Orton, Glenn S.; Yanamandra-Fisher, P. A.; Parrish, P. D.; Mousis, O.; Pantin, E.; Fuse, T.; Fujiyoshi, T.; Simon-Miller, A.; Morales-Juberias, R.; Tollestrup, E.; Connelley, M.; Trujillo, C.; Hora, J.; Irwin, P.; Fletcher, L.; Hill, D.; Kollmansberger, S. Bibcode: 2006DPS....38.3902O Altcode: 2006BAAS...38..554O White Oval BA, constituted from 3 predecessor vortices (known as Jupiter's "classical" White Ovals) after successive mergers in 1998 and 2000, became second-largest vortex in the atmosphere of Jupiter (and possibly the solar system) at the time of its formation. While it continues in this distinction,it required a name change after a 2005 December through 2006 February transformation which made it appear visually the same color as the Great Red Spot. Our campaign to understand the changes involved examination of the detailed color and wind field using Hubble Space Telescope instrumentation on several orbits in April. The field of temperatures, ammonia distribution and clouds were also examined using the mid-infrared VISIR camera/spectrometer on ESO's 8.2-m Very Large Telescope, the NASA Infrared telescope with the mid-infrared MIRSI instrument and the refurbished near-infrared facility camera NSFCam2. High-resolution images of the Oval were made before the color change with the COMICS mid-infrared facility on the 8.2-m Subaru telescope.We are using these images, togther with images acquired at the IRTF and with the Gemini/North NIRI near-infrared camera between January, 2005, and August, 2006, to characterize the extent to which changes in storm strength (vorticity, postive vertical motion) influenced (i) the depth from which colored cloud particles may have been "dredged up" from depth or (ii) the altitude to which particles may have been lofted and subject to high-energy UV radiation which caused a color change, as alternative explanations for the phenomenon. Clues to this will provide clues to the chemistry of Jupiter's cloud system and its well-known colors in general. The behavior of Oval BA, its interaction with the Great Red Spot in particular,are also being compared with dynamical models run with the EPIC code. Title: Vertical Profiles Of Nitrile Compounds In Titan's Atmosphere Measured By Cassini CIRS As A Tracer Of Atmospheric Circulation Authors: Teanby, Nicholas A.; Irwin, P. G.; de Kok, R.; Vinatier, S.; Bezard, B.; Nixon, C. A.; Flasar, M.; Calcutt, S. B.; Bowles, N. E.; Fletcher, L.; Howett, C.; Taylor, F. W. Bibcode: 2006DPS....38.3204T Altcode: 2006BAAS...38..543T The vertical profiles of nitrile compounds including HCN and HC3N were derived from mid-infrared observations taken with the Composite InfraRed Spectrometer (CIRS) on board the Cassini orbiter.

Nitrile compounds are created by photochemical reactions and have lifetimes ranging from under a year to tens of years - of the same order as a Titan year. Therefore, abundance variations can be used to probe atmospheric motion.

We used the limb sounding capabilities of CIRS to retrieve vertical profiles of HCN and HC3N from 85S to 85N. First, the segment of the mid-IR spectrum from 1240-1360cm-1 was used to retrieve temperature. Second, sub-spectra were extracted from the 600-750cm-1 region and used to obtain vertical profiles of nitriles. The limiting vertical resolution of these profiles is determined by the field-of-view size at the tangent height, which varied between 10 and 50km.

Both high (0.5cm-1) and low (13.5cm-1) spectral resolution data were used to derive the abundance profiles. The high resolution data was more precise, but only covered a few discrete latitudes, whereas the low resolution data covered almost the entire limb from north- to south-pole, but required verification by comparison with the high resolution data.

HC3N was massively enriched near the north pole, which can be explained in terms of subsidence. A boundary observed at 60N between enriched and un-enriched air is consistent with a confining polar vortex at 60N and HC3N's short lifetime.

HCN was also enriched over the north pole, which gives further evidence for subsidence. However, the atmospheric cross section obtained from 13.5cm-1 data indicated a HCN enriched layer at 200-250km, extending into the southern hemisphere. This could be interpreted as advection of polar enriched air towards the south by a meridional circulation cell. This is observed for HCN but not for HC3N due to HCN's longer photochemical lifetime. Title: Modelling Temperature Distribution Along A Magnetic Field Line Authors: Pollock, J. A.; Fletcher, L. Bibcode: 2006IAUJD...3E...4P Altcode: Fast electrons moving along a magnetic field line in the solar atmosphere undergo collisions with the particles of the background plasma. In doing so, they deposit some of their energy into the background plasma, increasing its temperature. In addition to this temperature increase, the plasma also undergoes radiative and conductive cooling, which alters the temperature distribution along the field line. Using stochastic simulations, we can model the movement of fast electrons along a field line and calculate changes in their energy as they undergo collisions. We use this data to map the temperature distribution along the field line, including radiative and conductive cooling, for injected electron beams of various initial distributions and injection parameters. Temperature maps, and the radiation maps that arise from them, can be compared with observations from RHESSI and other satellites. Title: Observations of simultaneous coronal loop shrinkage and expansion during the decay phase of a solar flare Authors: Khan, J. I.; Fletcher, L.; Nitta, N. V. Bibcode: 2006A&A...453..335K Altcode: We report what we believe are the first direct and unambiguous observations of simultaneous coronal magnetic flux loop shrinkage and expansion during the decay phase of a solar flare. The retracting and expanding loops were observed nearly face-on (i.e., with the loop major axis approximately orthogonal to the line of sight) in emission in imaging data from the Yohkoh Soft X-ray Telescope (SXT). The retracting loop is observed to shrink with a speed of 118 ± 66 km s-1. The faint outward moving loop-like feature occurred ~200´´ above the shrinking loop during the time of the shrinking loop. We estimate the speed of the outward moving loop was ~129 ± 74 km s-1. We interpret the shrinking loop and simultaneous outward moving loop as direct evidence for reconnected magnetic field lines during a flare. Title: Comparison of the Energy Spectra and Number Fluxes From a simple Flare Model to Observations Authors: Hannah, Iain G.; Fletcher, Lyndsay Bibcode: 2006SoPh..236...59H Altcode: In this paper, we investigate the energy spectra produced by a simple test particle X-point model of a solar flare for different configurations of the initial electromagnetic field. We find that once the reconnection electric field is larger than 1 Vm-1 the particle distribution transits from a heated one to a partially accelerated one. As we close the separatrices of the X-point and the angle in the inflow direction widens we find that more particles are accelerated out of the thermal distribution and this power-law component extends to lower energies. When we introduce a guiding magnetic field component we find that more particles are energised, but only up to a maximum energy dictated primarily by the reconnection electric field. Despite being able to accelerate particles to observable energies and demonstrate behaviour in the energy spectra that is consistent with observations, this single X-line model can only deliver the number fluxes required for microflares. Title: Modelling Temperature Distribution Along A Field Line Authors: Pollock, Jennifer A.; Fletcher, L. Bibcode: 2006SPD....37.0108P Altcode: 2006BAAS...38R.216P Fast electrons moving along a magnetic field line in the solaratmosphere undergo collisions with the particles of the backgroundplasma. In doing so, they deposit some of their energy into thebackground plasma, increasing its temperature. In addition to thistemperature increase, the plasma also undergoes radiative and conductivecooling, which alters the temperature distribution along the field line.Using stochastic simulations, we can model the movement of fastelectrons along a field line and calculate changes in their energy asthey undergo collisions. We use this data to map the temperaturedistribution along the field line, including radiative and condutivecooling, for injected electron beams of various initial distributionsand injection parameters. Temperature maps, and the radiation maps that arise from them, can be compared with observations from RHESSI and other satellites. Title: Latitudinal variations of HCN, HC 3N, and C 2N 2 in Titan's stratosphere derived from Cassini CIRS data Authors: Teanby, N. A.; Irwin, P. G. J.; de Kok, R.; Nixon, C. A.; Coustenis, A.; Bézard, B.; Calcutt, S. B.; Bowles, N. E.; Flasar, F. M.; Fletcher, L.; Howett, C.; Taylor, F. W. Bibcode: 2006Icar..181..243T Altcode: Mid- and far-infrared spectra from the Composite InfraRed Spectrometer (CIRS) have been used to determine volume mixing ratios of nitriles in Titan's atmosphere. HCN, HC 3N, C 2H 2, and temperature were derived from 2.5 cm -1 spectral resolution mid-IR mapping sequences taken during three flybys, which provide almost complete global coverage of Titan for latitudes south of 60° N. Three 0.5 cm -1 spectral resolution far-IR observations were used to retrieve C 2N 2 and act as a check on the mid-IR results for HCN. Contribution functions peak at around 0.5-5 mbar for temperature and 0.1-10 mbar for the chemical species, well into the stratosphere. The retrieved mixing ratios of HCN, HC 3N, and C 2N 2 show a marked increase in abundance towards the north, whereas C 2H 2 remains relatively constant. Variations with longitude were much smaller and are consistent with high zonal wind speeds. For 90°-20° S the retrieved HCN abundance is fairly constant with a volume mixing ratio of around 1 × 10 -7 at 3 mbar. More northerly latitudes indicate a steady increase, reaching around 4 × 10 -7 at 60° N, where the data coverage stops. This variation is consistent with previous measurements and suggests subsidence over the northern (winter) pole at approximately 2 × 10 -4 m s -1. HC 3N displays a very sharp increase towards the north pole, where it has a mixing ratio of around 4 × 10 -8 at 60° N at the 0.1-mbar level. The difference in gradient for the HCN and HC 3N latitude variations can be explained by HC 3N's much shorter photochemical lifetime, which prevents it from mixing with air at lower latitude. It is also consistent with a polar vortex which inhibits mixing of volatile rich air inside the vortex with that at lower latitudes. Only one observation was far enough north to detect significant amounts of C 2N 2, giving a value of around 9 × 10 -10 at 50° N at the 3-mbar level. Title: Organization and variation of Saturn's temperature field from Cassini CIRS and supporting ground-based observations Authors: Orton, G.; Parrish, P.; Yanamandra-Fisher, P.; Fisher, B.; Fletcher, L.; Irwin, P.; Flasar, M.; Achterberg, R.; Conrath, B.; Simon-Miller, A. Bibcode: 2006cosp...36.2583O Altcode: 2006cosp.meet.2583O An extended set of observations of Saturn s thermal field has been made by Cassini s Composite Infrared Spectrometer CIRS complemented by ground-based stations NASA s Infrared Telescope Facility Gemini North Telescope W M Keck Observatory and the Subaru Japanese National Telescope Observations by the large telescopes have provided high diffraction-limited spatial resolution of Saturn s disk on the order of 5000 km although so far these all have been at single points in time Thermal images from the NASA IRTF are characterized by spatial resolutions of approximately 13 000 km but have been made at more frequent intervals in time usually once every month except during solar conjunction Cassini CIRS observations of Saturn s temperature field have been made primarily in a mode in which a single hemisphere is mapped by scanning the central meridian while Saturn rotates CIRS spatial resolutions are typically 10 000 km in these maps but observations with spatial resolutions as high as 3 000 km have been made These observations including support imaging stretching several years before the Cassini arrival at Saturn show a warming of the south polar region as a result of increased seasonal sunlight a very hot south polar spot and a possible warm polar vortex in the south polar region Zonal thermal waves also exist at 16 28 38 and 52 degrees S planetocentric but they are not always present CIRS measurements of the shadowed north polar region do not show a cold counterpart to the warm south pole but a more detailed structure Saturn s Title: Latitudinal variations in the temperature and composition of Saturn's upper troposphere from Cassini/CIRS Authors: Fletcher, L. N.; Irwin, P. G. J.; Teanby, N. A.; Orton, G. S.; Parrish, P. D.; Calcutt, S. B.; Bowles, N.; de Kok, R.; Howett, C.; Cassini/Cirs Team Bibcode: 2006cosp...36..853F Altcode: 2006cosp.meet..853F The Cassini Composite Infrared Spectrometer CIRS Flasar et al 2004 has been used to derive the meridional variation of temperature phosphine PH 3 and ammonia NH 3 abundance in Saturn s upper troposphere 0 8 to 0 1 atm Since orbital insertion in July 2004 CIRS has recorded thousands of spectra in both the far 10 - 600 cm -1 and mid 600 - 1400 cm -1 infrared at a variety of apodized spectral resolutions 0 5 - 15 0 cm -1 and viewing geometries covering both hemispheres of the gas giant We use a non-linear optimal estimation retrieval code Irwin et al 2004 to derive vertical profiles of temperature composition and aerosol abundance The abundances of NH 3 and PH 3 are retrieved from rotational lines in the 10 - 200 cm -1 region and the nu 4 fundamental of PH 3 at 1070 - 1200 cm -1 Latitudinal temperature variations at the 0 25 atm are shown to occur on the same scale as the prograde and retrograde jets in Saturn s atmosphere Porco et al 2005 The distribution of phosphine a disequilibrium species in Saturn s cold upper troposphere Orton et al 2000 2001 may be used as a tracer for the upwelling of constituent-rich air from deeper within the atmosphere Elevated abundances of PH 3 at polar and equatorial latitudes correlations of PH 3 and NH 3 with the belt-zone temperature structure deviations of parahydrogen fraction from local thermochemical equilibrium at the equator and evidence for atmospheric heating by aerosols at 0 25 atm will also be Title: Organic Matter Analysis of the Hyper-Arid Peruvian Desert in comparison to other Hyper-Arid Environments Authors: Valdivia-Silva, J. E.; Fletcher, L. E.; Navarro-González, R.; McKay, C. P.; Pérez Montano, S.; Condori Apaza, R.; Conley, C. A. Bibcode: 2005AGUFM.P51D0949V Altcode: The Peruvian Desert is located along the Pacific coast of southern Peru and is a continuation of the Atacama Desert in Chile. The Peruvian Desert at the Pampas of La Joya has extreme environmental conditions, such as hyperaridity, and a complete absence of macroscopic life. La Joya contains volcanic soils with the presence of magnetite and quartz. Furthermore, the El Niño phenomena, centralized directly off the coast-line near La Joya, provides stronger climactic effects on this desert, resulting in higher levels of precipitation which should allow for the development of microscopic life. Taking into account that life is based on carbon, here we search for relationships between soil organic matter detected by oxidation versus pyrolisis (pyr-GC-MS) techniques. Our preliminary results showed similar levels of organic compounds to Yungay, the hyper-arid core of the Atacama Desert, similar levels of organic compounds to the Antarctic Dry Valleys, and direct correlation between oxidation and pyrolitic techniques. Title: a Solar Science Case with Astrogrid: Flare Productivity of Recently-Emerged Paired and Isolated Active Regions Authors: Dalla, S.; Fletcher, L.; Walton, N. A. Bibcode: 2005ESASP.600E.117D Altcode: 2005dysu.confE.117D; 2005ESPM...11..117D No abstract at ADS Title: Multiwavelength Observations of a Partially Occulted Solar Flare Authors: Bone, L.; Brown, J. C.; Fletcher, L. Bibcode: 2005ESASP.600E..38B Altcode: 2005ESPM...11...38B; 2005dysu.confE..38B No abstract at ADS Title: Coronal Heating and X-Ray Emission from a Beam of Fast Electrons Authors: Pollock, J. A.; Fletcher, L. Bibcode: 2005ESASP.600E.138P Altcode: 2005dysu.confE.138P; 2005ESPM...11..138P No abstract at ADS Title: X-Ray Quasi-Periodic Pulsations in Solar Flares as Magnetohydrodynamic Oscillations Authors: Foullon, C.; Verwichte, E.; Nakariakov, V. M.; Fletcher, L. Bibcode: 2005ESASP.600E..33F Altcode: 2005ESPM...11...33F; 2005dysu.confE..33F No abstract at ADS Title: Temperature Structure of Saturn from Spectral Mapping by Cassini CIRS and Joint High-Resolution Subaru COMICS and IRTF MIRSI Mid-Infrared Imaging Authors: Orton, G.; Parrish, P.; Yanamandra-Fisher, P.; Fletcher, L.; Irwin, P.; Fuse, T.; Fujiyoshi, T.; Hagopian, H.; Laakso, T.; Vogt, M.; Lotoszinski, J.; Hora, J. Bibcode: 2005AGUFM.P11C0129O Altcode: We report on a joint project of Cassini and ground-based support observations of Saturn's temperature field. Several sequences of CIRS spectra were made during 2004-2005 which scanned Saturn's central meridian using its FP1 (long wavelength-) and its FP3 and FP4 (intermediate- and short-wavelength) focal planes for the purpose of determining temperatures between 1 microbar and 400 mbar total pressure at spatial resolutions ranging from 170 to 3800 km (from 0.5 to 11 great-circle degrees). These infrequent observations (2004 Oct 30; 2005 March 10, April 8-9, May 22) were supplemented by a program at the NASA Infrared Telescope Facility of thermal imaging using the MIRSI mid-infrared camera spectrometer with diffraction-limited resolutions of ~3000 km, which provided a time sequence which is particularly valuable for characterizing wave structure and other time-dependent phenomena and for verifying CIRS temperature maps at 10 mbar or between 100 and 400 mbar pressure. We also obtained diffraction-limited resolutions of 1000 km thermal images of Saturn from the Subaru Japanese National Telescope using their COMICS facility mid-infrared camera/spectrometer on 2005 April 30 and May 24, providing spatial resolution commensurate with the Cassini/CIRS, global imaging, the opportunity for center-to-limb studies, and the means to track variability in PH3 and cloud optical thickness in very faint spectral regions. The meridional variability of temperatures is consistent with the seasonal dependence of temperatures documented by two decades of thermal monitoring of Saturn at the IRTF. Title: TRACE white light and RHESSI hard X-rays Authors: Fletcher, L.; Allred, J.; Hannah, I.; Hudson, H.; Metcalf, T. Bibcode: 2005AGUFMSH13A0286F Altcode: We study the energetics of RHESSI and TRACE observations for a sample of 11 solar flares well observed in the TRACE ``white light" channel. In general, the data show excellent correlations between hard X-rays and white light. We discuss the energetics of this relationship based upon simple models for the visible/UV continuum, namely (i) a non-thermal approximation (Balmer and Paschen continuum), (ii) a thermal approximation (blackbody), and (iii) model spectra derived from radiation-hydrodynamic modeling. We relate the white-light energy and the low-energy cutoff energy of the primary electron spectrum required for energetic equivalence. This comparison will be made in the context of the flare WL morphology and in comparison with RHESSI hard X-ray images. Title: X-Ray Quasi-Periodic Pulsations in Solar Flares as Magnetohydrodynamic Oscillations Authors: Foullon, C.; Verwichte, E.; Nakariakov, V. M.; Fletcher, L. Bibcode: 2005ESASP.596E..46F Altcode: 2005ccmf.confE..46F No abstract at ADS Title: The Observational Motivation for Computational Advances in Solar Flare Physics Authors: Fletcher, Lyndsay Bibcode: 2005SSRv..121..141F Altcode: A solar flare is a violent and transient release of energy in the corona of the Sun, associated with the reconfiguration of the coronal magnetic field. The major mystery of solar flare physics is the precise nature of the conversion of stored magnetic energy into the copious accelerated particles that are observed indirectly by the radiation that they produce, and also directly with in situ detectors. This presents a major challenge for theory and modeling. Recent years have brought significant observational advances in the study of solar flares, addressing the storage and release of magnetic energy, and the acceleration and propagation of fast electrons and ions. This paper concentrates on two topics relevant to the early phase of a flare, magnetic reconnection and charged particle acceleration and transport. Some recent pertinent observations are reviewed and pointers given for the directions that, this reviewer suggests, computational models should now seek to take. Title: X-ray quasi-periodic pulsations in solar flares as magnetohydrodynamic oscillations Authors: Foullon, C.; Verwichte, E.; Nakariakov, V. M.; Fletcher, L. Bibcode: 2005A&A...440L..59F Altcode: We report the first observation at high spatial resolution of long-period quasi-periodic pulsations (QPP) of X-ray radiation during solar flares, made possible with the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), supported by complementary data at other wavelengths from space-based and ground-based telescopes. Evidence for the presence of a transequatorial loop possibly responsible for the detected periodicity connected with its kink mode is found. Our findings suggest that QPP can be interpreted as a periodic pumping of electrons in a compact flaring loop, modulated by oscillations in a magnetically linked and larger loop acting as a long-period magnetohydrodynamic resonator. Title: Flows in the solar atmosphere due to the eruptions on the 15th July, 2002 Authors: Harra, L. K.; Démoulin, P.; Mandrini, C. H.; Matthews, S. A.; van Driel-Gesztelyi, L.; Culhane, J. L.; Fletcher, L. Bibcode: 2005A&A...438.1099H Altcode: Which kind of flows are present during flares? Are they compatible with the present understanding of energy release and which model best describes the observations? We analyze successive flare events in order to answer these questions. The flares were observed in the magnetically complex NOAA active region (AR) 10030 on 15 July 2002. One of them is of GOES X-class. The description of these flares and how they relate to the break-out model is presented in Gary & Moore (2004). The Coronal Diagnostic Spectrometer on board SOHO observed this active region for around 14 h. The observed emission lines provided data from the transition region to the corona with a field of view covering more than half of the active region. In this paper we analyse the spatially resolved flows seen in the atmosphere from the preflare to the flare stages. We find evidence for evaporation occurring before the impulsive phase. During the main phase, the ongoing magnetic reconnection is demonstrated by upflows located at the edges of the flare loops (while downflows are found in the flare loops themselves). We also report the impact of a filament eruption on the atmosphere, with flows up to 300 km s-1 observed at transition-region temperatures in regions well away from the location of the pre-eruptive filament. Our results are consistent with the predictions of the break out model before the impulsive phase of the flare; while, as the flare progresses, the directions of the flows are consistent with flare models invoking evaporation followed by cooling and downward plasma motions in the flare loops. Title: Saturn's atmospheric structure: the intercomparison of Cassini/CIRS-derived temperatures with ground-based determinations Authors: Parrish, P. D.; Orton, G. S.; Yanamandra-Fisher, P. A.; Fletcher, L.; Irwin, P. G. J.; Teanby, N.; Flasar, F. M.; Nixon, C. A.; Simon-Miller, A. A.; Cassini CIRS Team Bibcode: 2005DPS....37.3019P Altcode: 2005BAAS...37R.680P Although Saturn is similar to that of Jupiter in several respects, it has yet to be qualitatively-determined whether Saturn experiences similar seasonal variation of its equatorial stratosphere as have been observed on Jupiter [Orton et al., 1991; Flasar et al., 2003] and Earth [Linzen, 1968; reviewed by Baldwin et al., 2003]. While the nature of the radiatively-based, seasonal forcing on Jupiter is not fully understood, the modulated-temperatures are thought to play an important role in the transport of momentum between the troposphere and the stratosphere of any planet [Friedson, 1999]. The recent arrival of the Cassini-Huygens spacecraft to the Saturnian system provides an ideal opportunity to study this phenomena on Saturn. Specifically, what is the spatial orientation and temporal organisation of the atmospheric structure at upper-tropospheric/lower-stratospheric altitudes with regard to the dynamical models of other, better-characterised planets? The preliminary analysis, comparing Cassini Composite Infrared Spectrometer-derived temperatures with those obtained via images taken with NASA's Infrared Telescope Facility will be presented.

Baldwin, M.P. et al. (2001). Rev. Geophys., 29: 179-229.

Flasar, F.M. et al. (2003). Nature, 429(6969): 132-135.

Friedson, A.J (1999). Icarus, 137(1):34-55.

Lindzen, R.S. et al. (1968). J. Atmos. Sci., 25: 1095-1107.

Orton, G.S. et al. (1991). Science, 252: 537-542.

Acknowledgements: The acquisition of data described here was accomplished through the coordinated effort of Cassini-Huygens project staff, Deep Space Network personel and the CIRS instrument and science-planning teams with funding provided by NASA/JPL, the UK Particle Physics and Astronomy Council, NASA/GSFC and the National Research Council Research Associate Program. Title: Vertical profiles and latitudinal variations of nitrile abundances in Titan's atmosphere derived from Cassini/CIRS limb and nadir data Authors: Teanby, N. A.; Irwin, P. G. J.; de Kok, R.; Nixon, C. A.; Coustenis, A.; Bézard, B.; Calcutt, S. B.; Bowles, N. E.; Flasar, F. M.; Fletcher, L.; Howett, C.; Taylor, F. W.; CIRS Team Bibcode: 2005DPS....37.4102T Altcode: 2005BAAS...37..707T The Cassini/Huygens spacecraft entered orbit around Saturn on 1st July 2004. Since then, the Composite InfraRed Spectrometer (CIRS) has successfully returned thousands of infrared spectra of Titan at resolutions from 0.5--15 cm-1 in the mid- and far-IR (10--1400 cm-1 or 1000--7 μ m). This spectral region is rich in features from many nitrile compounds, which allows their abundance to be retrieved.

Nitrile species provide the possibility of tracing atmospheric circulation on Titan. One Titan year lasts 30 earth years. Therefore, with photochemical lifetimes ranging from under a year to tens of years, nitrile abundances can be used to probe time scales relevant to atmospheric motion. The observed variations can then be compared to predictions from dynamical and photochemical models.

We have used the limb sounding capabilities of CIRS to retrieve vertical profiles of nitrile species, including HCN and HC3N. First, the segment of the mid-IR spectrum from 1240-1360 cm-1 was used to retrieve stratospheric temperature. Second, sub-spectra were extracted from the 10--800 cm-1 region and used to obtain vertical profiles of nitriles. The limiting vertical resolution of these profiles is determined by the field of view size at the tangent height, which varies between 10 and 50 km. Profiles from the equator and north polar region will be presented.

We also discuss the latitude variation of nitrile compounds derived from over 18000 nadir spectra selected from 2.5 cm-1 resolution mapping sequences taken from July 2004 to April 2005 and covering 90S to 60N. Contribution functions for these observations peak around 3 mbar, well into the stratosphere. HCN, HC3N, and C2N2 all display a marked increase toward the north. HCN displays a 4 fold increase from 0--60N. A simple 1D numerical model coupled with the HCN variation implies a downwelling velocity of 0.3 mms-1. The nadir determinations will be compared with vertical profiles derived from the limb data. Title: Latitudinal Variation in Temperature and Composition of Saturn's Upper Troposphere from Cassini/CIRS as a Tracer For Atmospheric Dynamics Authors: Fletcher, L. N.; Irwin, P. G. J.; Teanby, N.; Orton, G.; Parrish, P.; de Kok, R.; Calcutt, S.; Howett, C.; Read, P. L.; Taylor, F. W.; Cassini CIRS Team Bibcode: 2005DPS....37.3006F Altcode: 2005BAAS...37Q.678F The presence of the Cassini Huygens spacecraft in the Saturnian system provides an unprecedented opportunity to study the dynamics of the gas giant in more detail than ever before. Infrared spectra from Saturn's southern hemisphere have been obtained by the Composite Infrared Spectrometer (CIRS), at both a high (0.5cm-1) and medium (2.5cm-1) apodized spectral resolution. Latitudinal variations of temperature and composition in Saturn's upper troposphere are measured using an optimal estimation retrieval code developed in Oxford. The far infrared (10-600cm-1) continuum is modelled by varying temperature, para-hydrogen fraction and aerosol opacity, with temperature contribution functions sensing pressures from 0.1 to 0.5atm. Abundances and fractional scale heights of ammonia and phosphine are then retrieved from rotational lines in the 10-200cm-1 region. The mid infrared (600-1400cm-1) provides temperature profiles from 600-700cm-1, whilst the ν 4 fundamental of phosphine at 1118cm-1 is used to retrieve a further measure of its abundance. Results are compared to global data from the Mid Infrared Spectrometer and Imager (MIRSI) instrument on NASA's Infrared Telescope Facility. Measurement from filters covering the collision induced absorption of hydrogen in the 400-600cm-1 region and the ν 2 phosphine fundamental near to 1000cm-1 were obtained using the same retrieval scheme.

The distribution of phosphine and ammonia is a balance between vertical transport and photochemical destruction. Elevated abundances of these gases are used as tracers for regions of upwelling constituent-rich air from deeper within the troposphere. Variations in retrieved optical depth due to aerosols, and deviations of parahydrogen fraction from local thermal equilibrium are also presented. Using an assumed stratospheric abundance of methane, the mid infrared spectra were used to obtain preliminary measures of the [D]/[H] ratio in methane of (1.96± 0.80) × 10-5 and a [12C]/[13C] ratio of 78.5-14.0+21.9.

Acknowledgement: This work is funded by the UK Particle Physics and Astronomy Research Council. Title: Titan's Oxygen compound distributions and condensate characteristics from Cassini/CIRS observations Authors: de Kok, R.; Irwin, P. G. J.; Teanby, N. A.; Fletcher, L.; Calcutt, S. B.; Howett, C.; Taylor, F. W.; Bowles, N. E.; Cassini CIRS Team Bibcode: 2005DPS....37.4508D Altcode: 2005BAAS...37Q.718D The Cassini/CIRS instrument has measured Titan's infrared spectrum many times since its arrival at Saturn in July 2004. Observations were made both in nadir and in limb geometry, at a wide range of latitudes and altitudes.

Using nadir and limb data with the highest spectral resolution obtainable by CIRS (0.5 cm-1), the stratospheric emission of carbon dioxide at 667 cm-1 was analysed. Results of this analysis include the variations of the CO2 concentration with latitude, and the variation with altitude. The latter is critical for understanding the oxygen chemistry in Titan's atmosphere and can constrain the nature of Titan's oxygen source. The abundance of CO was also determined and an upper limit was set for the H2O abundance.

CIRS has the capability to measure, for the first time, the spectral region between 10-200 cm-1. This region is mainly dominated by collision induced absorption and includes the rotational lines of e.g. CH4, HCN and CO. In this region, at least two broad spectral features were also identified, possibly caused by condensates. CIRS data with low spectral resolution (15 cm-1) was used to obtain dependences with latitude and altitude of these features, therefore constraining their possible sources. Title: Electron Acceleration at Reconnecting X-Points in Solar Flares Authors: Hamilton, B.; Fletcher, L.; McClements, K. G.; Thyagaraja, A. Bibcode: 2005ApJ...625..496H Altcode: The acceleration of electrons in solar flares is simulated using an extended version of a full orbit test-particle code previously used to compute losses of fusion alpha particles from tokamaks and to study flare proton acceleration. The magnetic and electric fields in the model are obtained from solutions of the linearized MHD equations for reconnecting modes at a magnetic X-point with zero equilibrium current. The magnetic field is assumed to have a small finite component perpendicular to the plane of the X-point. The version of the code used in the simulations is fully relativistic and includes Coulomb collisions. It is demonstrated that electrons cross the system boundary at distinct footpoints with the relative numbers and energy distribution at each footpoint sensitive to the longitudinal magnetic field component and collision time. These results are discussed in the context of recent flare observations showing asymmetric hard X-ray emission from the chromospheric footpoints of magnetic loops. Title: TRACE and RHESSI observations of white-light flares Authors: Hudson, H. H.; Metcalf, T.; Wolfson, J.; Fletcher, L.; Khan, J. Bibcode: 2005AGUSMSP51C..03H Altcode: TRACE gives a photometrically stable, high-resolution view of the visible and UV emissions of solar flares, with enough diagnostic power to distinguish photospheric from chromospheric contributions. These emissions dominate the radiant energy of a flare and correspond well with hard X-ray emission in the impulsive phase. We survey these data with reference to well-observed events of 4~October~2002 and 4~November~2003, on the disk (M4; S19W09) and on the limb (X17; S19W83) respectively. We analyze the spatial and temporal properties of the footpoint sources in these two events, characterizing their physical parameters (contrast, image gradients, apparent motions). The brightest kernels of the 4~October~2002 event have intensities twice that of the quiet photosphere, and have sizes close to the Nyquist limit of the TRACE pixels (0.5~arc~sec). The white-light footpoint sources can be considered as a proxy for the target region of fast electrons studied via hard X-ray bremsstrahlung. We compare RHESSI hard X-ray footpoint sources with their white-light counterparts and estimate filling factors for the hard X-ray emission itself. Title: Fip Enhancement by Alfvén Ionization Authors: Diver, D. A.; Fletcher, L.; Potts, H. E. Bibcode: 2005SoPh..227..207D Altcode: Alfvén ionization is offered as a possible mechanism underlying the enhanced population of low first ionization potential (FIP) species in the solar corona. In this process, the photospheric flow impinging on the magnetic structure of a coronal flux tube collides with, and displaces, ions in the magnetised plasma within the flux tube. This leads to pockets of charge imbalance that persist due to the impeded electron transport perpendicular to the magnetic field. The localised electric field then energises electrons to the impact ionization energy threshold of low-FIP components in the surface flow. Such species remain trapped in the plasma, and drift up the magnetic structure, causing a localised population enhancement compared to photospheric levels. We find that this mechanism successfully accounts for observed biases for flow speeds known to exist in the photosphere, and moreover explains certain anomalous abundances which do not fit into existing theories. Title: Multialtitude Observations of a Coronal Jet during the Third Whole Sun Month Campaign Authors: Ko, Y. -K.; Raymond, J. C.; Gibson, S. E.; Alexander, D.; Strachan, L.; Holzer, T.; Gilbert, H.; Cyr, O. C. St.; Thompson, B. J.; Pike, C. D.; Mason, H. E.; Burkepile, J.; Thompson, W.; Fletcher, L. Bibcode: 2005ApJ...623..519K Altcode: On 1999 August 26, a coronal jet occurred at the northwest limb near a sigmoid active region (AR 8668) that was the target for a joint observation plan (SOHO joint observing program 106) during the third Whole Sun Month Campaign. This jet was observed by several instruments at the limb (SOHO/CDS, SOHO/EIT, TRACE, and Mauna Loa Solar Observatory CHIP and PICS) and at 1.64 Rsolar (SOHO/UVCS). At the limb, this jet event displayed both low- and high-temperature components. Both high- and low-temperature components were evident during the early phase (first 20 minutes) of the event. However, the low-temperature component is maintained for ~1 hr after the higher temperature component is gone. There is a second brightening (a possible second jet) seen by EIT and TRACE about 50 minutes after the onset of the first jet. The line-of-sight motion at the limb began with a 300 km s-1 redshift and evolved to a 200 km s-1 blueshift. At 1.64 Rsolar, the intensities of Lyα and Lyβ in the jet increased by a factor of several hundred compared with the background corona. The C III λ977 line also brightened significantly. This indicates low-temperature [~(1-2)×105 K] emission in the jet, while the intensities of O VI λ1032 and O VI λ1037 increased by as much as a factor of 8. The UVCS data show evidence of heating at the early phase of the event. The Doppler shift in the lines indicates that the line-of-sight (LOS) velocity in the jet started from ~150 km s-1 in blueshift and ended at ~100 km s-1 in redshift. This LOS motion seen at 1.64 Rsolar was apparently opposite to what was observed when the jet emerged from the limb. The Doppler dimming analysis indicates that the radial outflow speed correlates with the magnitude of the LOS speed. Interestingly, UVCS observations at 2.33 and 2.66 Rsolar show no trace of the jet and SOHO/LASCO observations also yield no firm detection. We find that a simple ballistic model can explain most of the dynamical properties of this jet, while the morphology and the thermal properties agree well with reconnection-driven X-ray jet models. Title: Rhessi Microflare Statistics Authors: Hannah, I. G.; Christe, S.; Krucker, S.; Hudson, H. S.; Fletcher, L.; Hendry, M. A. Bibcode: 2004ESASP.575..259H Altcode: 2004soho...15..259H No abstract at ADS Title: On the Role of Fast Shocks in Creating Relativistic Electrons in the Solar Corona Authors: Hesse, M.; Fletcher, L.; Neukirch, T. Bibcode: 2004AGUFMSH24A..05H Altcode: The existence of fast shocks, at the interface between reconnection outflow jets and underlying magnetic loops, has been suggested by a number of researchers. Should they exist, fast shocks would provide an effective mechanism to convert a large fraction of the combined kinetic energy in the reconnection outflow into thermal energy of the shocked plasma. Since this process affects directly a large number of particles, it may provide a solution to the problem of explaining the number of electrons that are apparently involved in the generation of the high-energy X-ray signatures observed by RHESSI. In order to investigate this possibility further, we present the results of fully-electromagnetic, relativistic, particle-in-cell simulations of fast shock structure and evolution. In particular, we discuss the effect on downstream nonthermal electrons of parameters such as Mach number, plasma beta, and the angle between shock normal and the upstream magnetic field. We will compare our results to earlier kinetic studies of fast shocks, and provide an evaluation of the shock mechanism as a means to explain nonthermal, relativistic electron distributions such as expected in conjunction with RHESSI X-ray events. Title: The hard X-ray spectral structure of flare ribbons Authors: Hudson, H.; Fletcher, L.; Krucker, S.; Pollock, J. Bibcode: 2004AGUFMSH24A..02H Altcode: We examine the spatial distribution of hard X-ray spectral parameters in flares exhibiting the classic two-ribbon structure using RHESSI observations. The flares studied include July~15 and July~17, 2002, and October~29, 2003. We confirm the existence of a tendency for the localization of the hard X-ray sources into dominant bright ``footpoint'' regions which do not show ribbon structure as extensive as that seen in Hα or UV~images. As a part of the study we characterize the ribbons photometrically in the EUV as observed by TRACE, confirming earlier results that find complicated relationships between EUV and hard X-rays. We seek an empirical explanation for the restricted hard X-ray footpoints in terms of a spatial analog of the well-known ``soft-hard-soft'' morphology: the regions of weaker hard X-ray emission correspond to steeper X-ray energy spectra and hence to softer electron precipitation spectra. This relationship may be as predicted by the 1D radiation hydrodynamics models of flaring loops. Title: Overview of Solar Flares Authors: Hudson, Hugh; Fletcher, Lyndsay; Khan, Josef I.; Kosugi, Takeo Bibcode: 2004ASSL..314..153H Altcode: This chapter reviews the physics of solar flares, with special emphasis on the past decade. During this decade first Yohkoh and then TRACE have drastically improved our observational capabilities for flares, with contributions also from the essentially non-flare instrumentation on SOHO and of course the ground-based observatories. In this review we assess how these new observations have changed our understanding of the basic physics of flares and consider the implications of these results for future observations with FASR. The discussion emphasizes flaring loops, flare ejecta, particle acceleration, and microflares. Title: Tracking of TRACE Ultraviolet Flare Footpoints Authors: Fletcher, Lyndsay; Pollock, Jennifer A.; Potts, Hugh E. Bibcode: 2004SoPh..222..279F Altcode: Solar flares produce bright, compact sources of UV emission in the lower atmosphere, identified as flare footpoints. Observed at high time cadence with the Transition Region and Coronal Explorer, groups of UV footpoints define flare `ribbons' which move as the flare progresses. We have developed a procedure to track individual bright kernels within flare ribbons, enabling us to study the motion of these sites of excitation through the solar chromosphere. We have applied this to a flare observed by TRACE in the 1600 Å passband at 2-s cadence. In this event, the footpoints have an average speed of 15 km s−1, with a superposed random `meandering' component, consistent with the footpoint magnetic field being anchored around the edges of granular cells. Examining the brightness as a function of time, we find that the timing of peaks in brightness is significantly correlated with the timing of peaks in the product of the footpoint speed with the line-of-sight magnetic field strength at the footpoint location; in other words with a measure of the coronal reconnection rate. Title: Electron Inertial Effects on Rapid Energy Redistribution at Magnetic X-Points Authors: McClements, K. G.; Thyagaraja, A.; Ben Ayed, N.; Fletcher, L. Bibcode: 2004ApJ...609..423M Altcode: 2004astro.ph..1573M The evolution of nonpotential perturbations to a current-free magnetic X-point configuration is studied, taking into account electron inertial effects as well as resistivity. Electron inertia is shown to have a negligible effect on the evolution of the system whenever the collisionless skin depth is less than the resistive scale length. Nonpotential magnetic field energy in this resistive MHD limit initially reaches equipartition with flow energy, in accordance with ideal MHD, and is then dissipated extremely rapidly on an Alfvénic timescale that is essentially independent of Lundquist number. In agreement with resistive MHD results obtained by previous authors, the magnetic field energy and kinetic energy are then observed to decay on a longer timescale and exhibit oscillatory behavior, reflecting the existence of discrete normal modes with finite real frequency. When the collisionless skin depth exceeds the resistive scale length, the system again evolves initially according to ideal MHD. At the end of this ideal phase, the field energy decays typically on an Alfvénic timescale, while the kinetic energy (which is equally partitioned between ions and electrons in this case) is dissipated on the electron collision timescale. The oscillatory decay in the energy observed in the resistive case is absent, but short-wavelength structures appear in the field and velocity profiles, suggesting the possibility of particle acceleration in oppositely directed current channels. The model provides a possible framework for interpreting observations of energy release and particle acceleration on timescales down to less than a second in the impulsive phase of solar flares. Title: Meeting report: Core to corona: UKSP 2004 Authors: Fletcher, Lyndsay; Erdelyi, Robert Bibcode: 2004A&G....45c..33F Altcode: The UK solar physics community gathered with the MIST community in Edinburgh from 29 March - 1 April 2004, with a programme that reflected the strength and diversity of UK research in the field. Lyndsay Fletcher and Robert Erdelyi report. Title: The hard X-ray spectral structure of flare ribbons Authors: Fletcher, L.; Hudson, H. S.; Krucker, S.; Pollock, J. A. Bibcode: 2004AAS...204.5403F Altcode: 2004BAAS...36..758F We examine the spatial distribution of hard X-ray spectral parameters in flares exhibiting the classic two-ribbon structure using RHESSI observations. The flares studied include July 15 and July 17, 2002, and October 29, 2003. We confirm the existence of a tendency for the localization of the hard X-ray sources into dominant bright ``footpoint'' regions which do not show ribbon structure as extensive as that seen in Hα or UV images. As a part of the study we characterize the ribbons photometrically in the EUV as observed by TRACE, confirming earlier results that find complicated relationships between EUV and hard X-rays. We seek an empirical explanation for the restricted hard X-ray footpoints in terms of a spatial analog of the well-known ``soft-hard-soft'' morphology: the regions of weaker hard X-ray emission correspond to steeper X-ray energy spectra and hence to softer electron precipitation spectra. This relationship may be as predicted by the 1D radiation hydrodynamics models of flaring loops. Title: Multi-Altitude Observations of a Coronal Jet Authors: Ko, Y. -K.; Raymond, J. C.; Gibson, S. E.; Alexander, D.; Strachan, L.; Holzer, T.; Gilbert, H.; St. Cyr, O. C.; Thompson, B. J.; Pike, C. D.; Burkepile, J.; Thompson, W.; Fletcher, L. Bibcode: 2004AAS...204.5413K Altcode: 2004BAAS...36..759K A coronal jet occurred on August 26, 1999 at the NW limb near a sigmoid active region (AR8668). This jet was observed by several instruments at the limb (SOHO/CDS, SOHO/EIT, TRACE, MLSO/CHIP, MLSO/PICS) and at 1.64 Ro (SOHO/UVCS). At the limb, this jet event has both low and high temperature components. The high temperature component appeared at the early phase (first 20 minutes) of the event along with the low temperature component while the latter seems to last long ( ∼ 1 hour) after the higher temperature component was gone. The line-of-sight motion at the limb started with red-shifted (by as much as 300 km/s) and turned blue-shifted (by as much as 200 km/s). At 1.64 Ro, the intensities of Lyα , Lyβ in the jet increased by a factor of several hundreds compared with the background corona. C III λ 977 line also brightened significantly. This indicates low temperature ( ∼ 1-2× 105 K) emission in the jet, while the intensities of O VI λ 1032 and O VI λ 1037 increased by a factor of as large as 8. Both UVCS and CDS data show evidence of heating at the early phase of the event. The line-of-sight velocity seen at 1.64 Ro started with ∼ 150 km/sec in blue shift and ended at ∼ 100 km/sec in red shift. This is apparently opposite to what were observed when the jet emerged from the limb. The Doppler dimming analysis indicates that the radial outflow speed correlates with the magnitude of the line-of-sight speed. Interestingly, UVCS observations at 2.33 and 2.66 Ro show no trace of the jet and LASCO observations also yield no firm sight of the jet. In this paper, we present the observations by these instruments and discuss the dynamical structure and physical properties of this jet. Y.-K. Ko acknowledges the support by NASA grant NAG5-12865. Title: Electron inertia modifications to X-point reconnection in solar flares Authors: McClements, K. G.; Thyagaraja, A.; Ben Ayed, N.; Fletcher, L. Bibcode: 2004cosp...35.1242M Altcode: 2004cosp.meet.1242M The evolution of perturbations to a current-free magnetic X-point is studied as a paradigm for short timescale energy release in solar flares, taking into account electron inertia as well as resistivity. Electron inertia is found to have a negligible effect whenever the collisionless skin depth is less than the resistive scale length. Non-potential magnetic field energy in this resistive MHD limit initially reaches equipartition with flow energy, in accordance with ideal MHD, and is then dissipated extremely rapidly, on an Alfvénic timescale that is essentially independent of Lundquist number. In agreement with resistive MHD results obtained by previous authors [1], the magnetic field energy and kinetic energy are then observed to decay on a longer timescale and exhibit oscillatory behavior, reflecting the existence of discrete normal modes with finite real frequency. When the collisionless skin depth exceeds the resistive scale length, the field energy again decays on an Alfvénic timescale, while the kinetic energy (which is equally partitioned between ions and electrons in this case) decays on the electron collision timescale. In this regime filaments appear in the field and velocity profiles, suggesting the possibility of particle acceleration in oppositely-directed current channels and symmetrical precipitation out of the acceleration region. Both the rapid decay in field energy and the filamentation process arise from phase mixing associated with a continuous eigenmode spectrum that replaces the discrete resistive MHD spectrum [2]. Because of the Alfvénic timescale of the field decay, very modest perturbation amplitudes are sufficient for the corresponding inductive electric fields to produce hard X-ray emitting electrons on sub-second timescales. The model thus provides a framework for interpreting observations of short timescale energy release and particle acceleration in the impulsive phase of flares. This work was supported by the United Kingdom Engineering and Physical Sciences Research Council [1] Craig I. J. D. & Watson P. G. Astrophys. J 393, 385 (1992) [2] McClements K. G. & Thyagaraja A. Plasma Phys. Control. Fusion 46, 39 (2004) Title: Hubble Goes IMAX: 3D Visualization of the GOODS Southern Field for a Large Format Short Film Authors: Summers, F. J.; Stoke, J. M.; Albert, L. J.; Bacon, G. T.; Barranger, C. L.; Feild, A. R.; Frattare, L. M.; Godfrey, J. P.; Levay, Z. G.; Preston, B. S.; Fletcher, L. M.; GOODS Team Bibcode: 2003AAS...203.8603S Altcode: 2003BAAS...35.1345S The Office of Public Outreach at the Space Telescope Science Institute is producing a several minute IMAX film that will have its world premiere at the January 2004 AAS meeting. The film explores the rich tapestry of galaxies in the GOODS Survey Southern Field in both two and three dimensions. This poster describes the visualization efforts from FITS files through the galaxy processing pipeline to 3D modelling and the rendering of approximately 100 billion pixels. The IMAX film will be shown at a special session at Fernbank Science Center, and the video will be shown at the STScI booth. Title: UKSP: Solar physics in Dublin Authors: Erdélyi, R.; Fletcher, L.; Doyle, G. J. Bibcode: 2003A&G....44c..13E Altcode: This year's annual UK Solar Physics meeting took place in Dublin from 7-11 April 2003, overlapping with the National Astronomy Meeting. R Erdélyi, L Fletcher and G J Doyle summarize. Title: Field-Guided Proton Acceleration at Reconnecting x-Points in Flares Authors: Hamilton, B.; McClements, K. G.; Fletcher, L.; Thyagaraja, A. Bibcode: 2003SoPh..214..339H Altcode: 2003astro.ph..1359H An explicitly energy-conserving full orbit code CUEBIT, developed originally to describe energetic particle effects in laboratory fusion experiments, has been applied to the problem of proton acceleration in solar flares. The model fields are obtained from solutions of the linearised MHD equations for reconnecting modes at an X-type neutral point, with the additional ingredient of a longitudinal magnetic field component. To accelerate protons to the highest observed energies on flare timescales, it is necessary to invoke anomalous resistivity in the MHD solution. It is shown that the addition of a longitudinal field component greatly increases the efficiency of ion acceleration, essentially because it greatly reduces the magnitude of drift motions away from the vicinity of the X-point, where the accelerating component of the electric field is largest. Using plasma parameters consistent with flare observations, we obtain proton distributions extending up to γ-ray-emitting energies (> 1 MeV). In some cases the energy distributions exhibit a bump-on-tail in the MeV range. In general, the shape of the distribution is sensitive to the model parameters. Title: RHESSI Workshop Reports: Multiwavelength Correlative Studies of RHESSI events Authors: Fletcher, L.; RHESSI Workshop Series Working Group 4 Team Bibcode: 2003SPD....34.1402F Altcode: 2003BAAS...35..829F In this talk we will report on the projects and progress of RHESSI Working Group 4, 'Multi-Wavelength Correlative Studies'. The remit of this working group is to use diagnostics from space and ground-based instrumentation in tandem with RHESSI to further our understanding of the fast particles and plasmas produced during large and small flaring events, and to illuminate the magnetic environment in which these take place. Topics being studied include the Neupert effect, hot coronal sources and coronal mass motions, and flare footpoint evolution. The April 21st 2002 X1.5 flare is a focus for much of the group's activities. This event has excellent multiwavelength coverage and shows many interesting features such as coronal downflows, moving RHESSI coronal sources, and very compact hard X-ray footpoints. Title: The Energy Release Process in Solar Flares; Constraints from TRACE Observations Authors: Fletcher, L.; Warren, H. P. Bibcode: 2003LNP...612...58F Altcode: 2003ecpa.conf...58F The Transition Region And Coronal Explorer Satellite, TRACE, launched in 1998, has proved a valuable tool in the study of solar flares. UV and EUV observations of the impulsive and gradual phases of many tens of flares have been made. TRACE's excellent spatial resolution and image cadence on the order of one second allow the rearrangement of the magnetic field to be tracked in some detail. The combination of these observations with data from other instruments, and with magnetic field reconstructions, have provided strong evidence for (a) UV emission as a beam proxy in the impulsive phase (b) long duration coronal heating in the gradual phase (c) very complex and varied magnetic geometries. We review the observational evidence for the above, discussing implications for energy release. Title: Charged particle dynamics in X-type neutral points Authors: Hamilton, B.; Fletcher, L.; McClements, K. G.; Thyagaraja, A. Bibcode: 2002ESASP.506..291H Altcode: 2002svco.conf..291H; 2002ESPM...10..291H We have developed a novel algorithm for the calculation of test particle orbits in electromagnetic fields. We have applied this to the problem of determining ion and electron orbits in an X-type magnetic configuration, of a type that may occur during reconnection in the corona above a flaring region. Particles in our simulation gain energy through interaction with the normal modes of oscillation of the X-type structure. We find that the addition of a longitudinal magnetic field component to a model proposed by Craig and McClymont [ApJ 371, L41 (1991)] produces a much greater efficiency in accelerating protons. Results of different simulations are presented and the sensitivity of the results to the parameters of the magnetic environment is discussed. Title: Chaotic dynamics and collisionless reconnection at an X-type neutral point Authors: Hannah, Iain G.; Fletcher, Lyndsay; Hendry, Martin A. Bibcode: 2002ESASP.506..295H Altcode: 2002svco.conf..295H; 2002ESPM...10..295H The chaotic dynamics of test particle orbits in a magnetic X-type neutral point have been investigated through the use of Lyapunov Characteristic Exponents (LCE), with the aim of solving the Pesin Identity (sum of the positive LCE) as a Monte Carlo integration problem. Treating the identity in this manner allows the phase space of a system to be intelligently sampled for the most chaotic orbits, as these orbits contribute most to the integral. This analysis so far has concentrated on how the chaotic behaviour relates to particle acceleration and energy gain, with future work to examine whether the chaos can produce an "anomalous resistivity" affecting the reconnection rate. Title: Energetic particles in the solar atmosphere Authors: Fletcher, Lyndsay Bibcode: 2002ESASP.506..223F Altcode: 2002svco.conf..223F; 2002ESPM...10..223F This article reviews the evidence for, and the nature of, accelerated particles in the lower solar atmosphere. Particle distributions with significantly non-thermal components are ubiquitous throughout the solar atmosphere, and we concentrate primarily on those arising in solar flares. We mention the main diagnostics for accelerated flare electrons and ions, and discuss the more popular theoretical ideas regarding their acceleration. Title: Mapping RHESSI footpoints with potential-field models Authors: Fletcher, L.; Hudson, H. S.; Metcalf, T. R. Bibcode: 2002AGUFMSH52A0452F Altcode: RHESSI hard X-ray observations help us to identify the locations of magnetically conjugate footpoints, and to study their apparent motions during the evolution of the impulsive phase of a flare. We put this information into the context of an M-class flare that occurred 2002 March 14 01:50 UT (GOES peak time) at S12, E23 (NOAA region 9866) by making potential-field mappings of the coronal magnetic structure. In principle the hard X-ray sources (plus the mapping) constrain the site of magnetic energy release, and the maps reveal the location of the stored energy. The RHESSI source centroids can be determined to better than 1'' (rms) for an M-class flare. This analysis is an exploration of the feasibility of such an approach, since full success would require understanding the magnetic restructuring in detail. If suitable X-class RHESSI flares occur we will be able to present data with better precision. Title: Spectral and Spatial Variations of Flare Hard X-ray Footpoints Authors: Fletcher, L.; Hudson, H. S. Bibcode: 2002SoPh..210..307F Altcode: In a sample of strong RHESSI M-class flares we have made a study of the relationship between the `hardness' of the HXR spectrum and the intensity in the 30-50 keV energy range. In all events we find clear evidence for a `soft-hard-soft' pattern of correlation between hardness and flux, on time scales as short as 10 s. We investigate whether or not this pattern is intrinsic to the acceleration mechanism. The RHESSI images in this energy range are dominated by footpoint brightenings, and we have searched for a correlation between footpoint separation velocity and spectral hardness, to be compared qualitatively with theoretical flare models. We find quite systematic footpoint motions, and also note that episodes in which footpoint separation varies rapidly often correspond with episodes of significant change in the flare spectral index, though not as the simplest flare models would predict. We report also on one of our events, on 14 March 2002, which exhibits highly sheared HXR footpoint ribbons extending over a scale of 100 arc sec. For this flare we find a correlation between footpoint motion and hard X-ray flux. Title: Magnetic flux ropes: Would we know one if we saw one? Authors: Gibson, S. E.; Low, B. C.; Leka, K. D.; Fan, Y.; Fletcher, L. Bibcode: 2002ESASP.505..265G Altcode: 2002IAUCo.188..265G; 2002solm.conf..265G There has been much debate lately about whether twisted magnetic flux ropes exist in the corona. When asked for observational evidence of them, the temptation is to show images of apparently twisted structures. However, we must be very careful of projection effects in interpreting these observations. Two critical aspects of understanding how we might observe flux ropes are 1) the 3D nature of the flux rope, and 2) physically, which bits are visible and for what reasons? In this paper we will use a simple but physically reasonable 3D analytic model to address these two issues, and develop techniques that can in future be used on more general models, both analytic and numerical. Title: High-energy solar radiation with RHESSI Authors: Fletcher, L. Bibcode: 2002Obs...122..249F Altcode: No abstract at ADS Title: The Structure and Evolution of a Sigmoidal Active Region Authors: Gibson, S. E.; Fletcher, L.; Del Zanna, G.; Pike, C. D.; Mason, H. E.; Mandrini, C. H.; Démoulin, P.; Gilbert, H.; Burkepile, J.; Holzer, T.; Alexander, D.; Liu, Y.; Nitta, N.; Qiu, J.; Schmieder, B.; Thompson, B. J. Bibcode: 2002ApJ...574.1021G Altcode: Solar coronal sigmoidal active regions have been shown to be precursors to some coronal mass ejections. Sigmoids, or S-shaped structures, may be indicators of twisted or helical magnetic structures, having an increased likelihood of eruption. We present here an analysis of a sigmoidal region's three-dimensional structure and how it evolves in relation to its eruptive dynamics. We use data taken during a recent study of a sigmoidal active region passing across the solar disk (an element of the third Whole Sun Month campaign). While S-shaped structures are generally observed in soft X-ray (SXR) emission, the observations that we present demonstrate their visibility at a range of wavelengths including those showing an associated sigmoidal filament. We examine the relationship between the S-shaped structures seen in SXR and those seen in cooler lines in order to probe the sigmoidal region's three-dimensional density and temperature structure. We also consider magnetic field observations and extrapolations in relation to these coronal structures. We present an interpretation of the disk passage of the sigmoidal region, in terms of a twisted magnetic flux rope that emerges into and equilibrates with overlying coronal magnetic field structures, which explains many of the key observed aspects of the region's structure and evolution. In particular, the evolving flux rope interpretation provides insight into why and how the region moves between active and quiescent phases, how the region's sigmoidicity is maintained during its evolution, and under what circumstances sigmoidal structures are apparent at a range of wavelengths. Title: Emergence of twisted magnetic flux into the corona Authors: Gibson, S.; Low, B. C.; Fan, Y.; Fletcher, L. Bibcode: 2002AAS...200.3603G Altcode: 2002BAAS...34..693G The interaction between emerging magnetic structures and preexisting overlying coronal structures will be addressed using a combination of observations and physical models that incorporate a range of twisted magnetic topologies. Solar explosive events such as coronal mass ejections (CMEs) and flares are commonly considered to be driven by the free magnetic energy stored in twisted (current carrying) coronal magnetic fields. Understanding the origin and the three-dimensional nature of these twisted coronal magnetic structures is a crucial step towards explaining and predicting CMEs and flares. One possible and appealing picture is that the twisted coronal magnetic structures form as a result of the emergence of twisted magnetic flux tubes from the solar interior. We might imagine a scenario where a flux rope forms sub-photospherically, emerges through the photosphere, exists in the corona until it loses its stability and erupts in a CME which moves out through interplanetary space until ultimately impacting on the Earth's magnetosphere. Attractively simple as this picture is, reality is likely to be more complicated since the various regimes are physically very different and pre-existing structures would get in the way of our traveling flux rope. We will concentrate on joining up two of these regimes, by considering how a flux rope could rise from beneath the photosphere and emerge into the corona, interacting with pre-existing coronal structures. We will approach this problem by using a combination of numerical models of the flux rope emergence from beneath the photosphere, analytic models of coronal dynamic and equilibrium magnetic structures, and photospheric and coronal observations of the 3-d structure and evolution of a so-called "sigmoidal", or S-shaped active region. In so doing we hope to gain essential insight into how twisted magnetic fields are formed and how they could be ultimately removed from the solar corona. Title: 2-ribbon flares: observations vs. models Authors: Fletcher, Lyndsay Bibcode: 2002ocnd.confE..10F Altcode: No abstract at ADS Title: The Magnetic Structure and Generation of EUV Flare Ribbons Authors: Fletcher, L.; Hudson, H. Bibcode: 2001SoPh..204...69F Altcode: The `ribbons' of two-ribbon flares show complicated patterns reflecting the linkages of coronal magnetic field lines through the lower solar atmosphere. We describe the morphology of the EUV ribbons of the July 14, 2000 flare, as seen in SOHO, TRACE, and Yohkoh data, from this point of view. A successful co-alignment of the TRACE, SOHO/MDI and Yohkoh/HXT data has allowed us to locate the EUV ribbon positions on the underlying field to within ∼ 2'', and thus to investigate the relationship between the ribbons and the field, and also the sites of electron precipitation. We have also made a determination of the longitudinal magnetic flux involved in the flare reconnection event, an important parameter in flare energetic considerations. There are several respects in which the observations differ from what would be expected in the commonly-adopted models for flares. Firstly, the flare ribbons differ in fine structure from the (line-of-sight) magnetic field patterns underlying them, apparently propagating through regions of very weak and probably mixed polarity. Secondly, the ribbons split or bifurcate. Thirdly, the amount of line-of-sight flux passed over by the ribbons in the negative and positive fields is not equal. Fourthly, the strongest hard X-ray sources are observed to originate in stronger field regions. Based on a comparison between HXT and EUV time-profiles we suggest that emission in the EUV ribbons is caused by electron bombardment of the lower atmosphere, supporting the hypothesis that flare ribbons map out the chromospheric footpoints of magnetic field lines newly linked by reconnection. We describe the interpretation of our observations within the standard model, and the implications for the distribution of magnetic fields in this active region. Title: Numerical Modelling of Trapped Electrons in an Expanding Solar Loop Authors: Fletcher, L.; Hudson, H. Bibcode: 2001AGUFMSH42A0777F Altcode: Recent observations with the Yohkoh Hard X-ray telescope and the Nobeyama Radioheliograph [Hudson et al., 2001] have shown a moving hard X-ray coronal source, associated in space and time with moving microwave and decimeter sources. Because of the electron energies involved in producing these emissions, we hypothesize that the radiation indicates the presence of a coronal population of high energy electrons, trapped in a magnetic loop which is expanding outward. The expansion will lead to a `betatron' deceleration effect, which, combined with the normal Coulomb scattering and energy losses, will lead to an evolution of the particle energy density, spectrum and pitch angle distribution. We model this process using a stochastic test particle simulation. >http://isass1.solar.isas.ac.jp/ ~hudson/drafts/apr18.pdf</a> Title: A Relationship Between Transition Region Brightenings, Abundances, and Magnetic Topology Authors: Fletcher, Lyndsay; López Fuentes, Marcelo C.; Mandrini, Cristina H.; Schmieder, Brigitte; Démoulin, Pascal; Mason, Helen E.; Young, Peter R.; Nitta, Nariaki Bibcode: 2001SoPh..203..255F Altcode: We present multi-instrument observations of active region (AR) 8048, made between 3 June and 5 June 1997, as part of the SOHO Joint Observing Program 33. This AR has a sigmoid-like global shape and undergoes transient brightenings in both soft X-rays and transition region (TR) lines. We compute a magneto-hydrostatic model of the AR magnetic field, using as boundary condition the photospheric observations of SOHO/MDI. The computed large-scale magnetic field lines show that the large-scale sigmoid is formed by two sets of coronal loops. Shorter loops, associated with the core of the SXT emission, coincide with the loops observed in the hotter CDS lines. These loops reveal a gradient of temperature, from 2 MK at the top to 1 MK at the ends. The field lines most closely matching these hot loops extend along the quasi-separatrix layers (QSLs) of the computed coronal field. The TR brightenings observed with SOHO/CDS can also be associated with the magnetic field topology, both QSL intersections with the photosphere, and places where separatrices issuing from bald patches (sites where field lines coming from the corona are tangent to the photosphere) intersect the photosphere. There are, furthermore, suggestions that the element abundances measured in the TR may depend on the type of topological structure present. Typically, the TR brightenings associated with QSLs have coronal abundances, while those associated with BP separatrices have abundances closer to photospheric values. We suggest that this difference is due to the location and manner in which magnetic reconnection occurs in two different topological structures. Title: Evidence for the Flare Trigger Site and Three-Dimensional Reconnection in Multiwavelength Observations of a Solar Flare Authors: Fletcher, L.; Metcalf, T. R.; Alexander, D.; Brown, D. S.; Ryder, L. A. Bibcode: 2001ApJ...554..451F Altcode: Based on a multiwavelength data set and a topological model for the magnetic field, we argue that a M1.9 flare which occurred on 1993 May shows evidence of three-dimensional coronal reconnection in a spine-fan configuration. Images from the Transition Region and Coronal Explorer allow the detailed examination of the structures involved in the flare and preflare in the 171 Å (1 MK) EUV passband and the Lyα (10,000-20,000 K) passband. Yohkoh Hard X-ray Telescope maps the position of nonthermal electron precipitation and the Soft X-ray Telescope reveals preflare and flare heating on large and small scales. While the flare appears to be driven by changes in small-scale field close to the photosphere, near the interface between strong opposite magnetic polarities, the result is the disruption of large-scale field. We demonstrate how this observed activity on large and small scales, along with many other aspects of the flare, suggests a qualitative explanation in the three-dimensional reconfiguration of coronal magnetic field, following a small-scale flux cancellation at the photosphere. Title: Ribbons and field at high resolution Authors: Fletcher, L.; Hudson, H. S. Bibcode: 2001AGUSM..SH31D10F Altcode: The TRACE data let us define the geometry of flare ribbons with great precision, as for example in the Bastille Day 2000 flare. We study the UV and EUV ribbon motions for this event in comparison with the loops seen by SXT and in the TRACE high-temperature response, and compare these also with the photospheric magnetic field as observed by MDI. In this work we assume the standard model for large-scale coronal magnetic reconnection as a source of flare energy, and search for a correlation between footpoint locations, magnetic field strength and flare energy release as measured by hard X-ray emission. Title: CDS UV Brightenings Explained by Quasi-separatrices and Bald Patches in an S-shape active region Authors: Schmieder, B.; Démoulin, P.; Fletcher, L.; López Fuentes, M. C.; Mandrini, C. H.; Mason, H. E.; Young, P. R.; Nitta, N. Bibcode: 2001IAUS..203..314S Altcode: We present multi-instrument observations of AR 8048, made between June 3 and June5 1997 as part of SoHO JOP033. This active region has a sigmoid-like global shape and undergoes transient erupting phenomena which releases the stored energy. Using a force free field approach, we defined coronal magnetic field lines which fit with the observations. The large-scale magnetic field lines confirms the sigmoid characteristics of the active region. The study in 3D of the configuration explained where and how the energy is released at different places. The Ne VI brightenings correspond to the location of tangent to the photosphere field lines, named "bald patch", they are localized in the low transition region and represent feet of field lines. The Si XII brightenings at coronal temperature are at the top of coronal loops joining quasi-separatrices. Title: SOHO/UVCS Observations of a Coronal Jet During the Third Whole Sun Month Campaign Authors: Ko, Y. -K.; Raymond, J.; Gibson, S.; Strachan, L.; Alexander, D.; Fletcher, L.; Holzer, T.; Gilbert, H.; Burkepile, J.; St. Cyr, C.; Thompson, B. Bibcode: 2000SPD....31.0271K Altcode: 2000BAAS...32R.823K On August 26 1999, a coronal jet occurred at the north west limb near a sigmoid active region which has been the target for a joint observation plan during the third Whole Sun Month Campaign. This jet was observed by several instruments at the limb (SOHO/CDS, SOHO/EIT, TRACE, MLSO/CHIP, MLSO/PICS), at 1.7 Ro (SOHO/UVCS), and at the outer corona (SOHO/LASCO). At 1.7 Ro, the intensities of Lyman alpha, Lyman beta in the jet increased by as large a factor of 100 compared with the background corona, while those for O VI 1032 and O VI 1037 increased by a factor of 2. C III 977 line also brightened significantly. The line shift in the lines indicates that the line-of-sight velocity in the jet started from 150 km/sec blue shift and ended at 120 km/sec red shift. This line-of-sight motion seen at 1.7 Ro apparently was opposite that observed when the jet emerged from the limb. In this paper, we present the observation by SOHO/UVCS and discuss the dynamic structure and physical properties of this jet as it passed through 1.7 Ro. Comparisons will be shown with the observations from other instruments. This work is supported by NASA Grant number NAG5-7822. Title: Evidence for the Flare Trigger Site and 3-D Reconnection in Multi-Wavelength Observations of a Solar Flare Authors: Metcalf, T. R.; Fletcher, L.; Alexander, D.; Brown, D. S.; Ryder, L. A. Bibcode: 2000SPD....31.0261M Altcode: 2000BAAS...32..822M Based on a multi-wavelength data set and a topological model for the magnetic field, we argue that a M1.9 flare which occurred on 3-May-99 shows evidence of 3-d reconnection through a coronal null. Images from the Transition Region and Coronal Explorer allow the detailed examination of the structures involved in the flare and pre-flare in the 171 Angstroms (1MK) EUV passband, and the Lyman α (10,000-20,000K) passband. Yohkoh Hard X-ray Telescope maps the position of non-thermal electron precipitation and the Soft X-ray Telescope reveals pre-flare and flare heating on large and small-scales. While the flare appears to trigger in small scale field close to the photosphere, near the interface between strong opposite magnetic polarities, the large-scale field is directly involved in or affected by all phases of the flare. We demonstrate how this observed activity on large and small scales, along with many other aspects of the flare find a qualitative explanation in the three-dimensional reconfiguration of coronal magnetic field, following a small-scale flux cancelation at the photosphere. This work is supported by the TRACE and SXT projects at LMSAL (contract NAS5-38099 and NAS8-40801). Title: Observations of H-alpha Polarization in Flares Authors: Mickey, D. L.; Metcalf, T. R.; Fletcher, L. Bibcode: 2000SPD....31.0255M Altcode: 2000BAAS...32R.820M Max Millennium Coordinated Observing Plan #006 has as its goal the measurement of H-alpha linear polarization, a possible signature of low-energy proton beams in solar flares. Such observations have been attempted in the past, but the results were inconclusive. A campaign involving Mees Solar Observatory and Big Bear Solar Observatory, together with Yohkoh, SOHO and TRACE spacecraft, was carried out during the latter half of March 2000. We present preliminary results from the observations with the Imaging Vector Magnetograph at Mees Solar Observatory. The IVM was operated in a standard mode, except that the spectral scan was limited to one point in the core of H-alpha and one in the blue wing. This limited spectral sampling, together with a recently upgraded data acquisition system, permitted a complete measurement of Stokes vectors every 3.5 seconds. The field of view was 280 arc sec square, with one arc sec pixels. A second camera, exposed simultaneously but with a broad-band filter, provides images which allow compensation for relative image motion and stretch between exposures. Approximately two dozen flares were observed by the IVM during the campaign, including one X-class and one M-class flare. We present samples of the observations, including relevant spacecraft observations, and discuss the sensitivity of the IVM to linear polarization under these conditions. This work was supported in part by the SXT project at LMSAL (contract NAS5-38099) and by NASA grant NAG5-4941. Title: Electron Trapping and Precipitation in Asymmetric Solar Flare Loops Authors: Aschwanden, M. J.; Fletcher, L.; Sakao, T.; Kosugi, T.; Hudson, H. Bibcode: 2000IAUS..195..375A Altcode: Acceleration, propagation, and energy loss of particles energized in solar flares cannot be studied separately because their radiative signatures observed in the form of hard X-ray bremsstrahlung or radio gyrosynchrotron emission represent a convolution of all these processes. We analyze hard X-ray emission from solar flares using a kinematic model that includes free-streaming electrons (having an energy-dependent time-of-flight delay) as well as temporarily trapped electrons (which are pitch-angle scattered by Coulomb collisional scattering) to determine various physical parameters (trapping times, flux asymmetry, loss-cone angles, magnetic mirror ratios) in flare loops with asymmetric magnetic fields. Title: Electron Kinematics near the Loss-Cone Authors: Fletcher, L.; Aschwanden, M. J. Bibcode: 2000SPD....31.0247F Altcode: 2000BAAS...32..819F With the upcoming launch of the HESSI satellite, we expect that problems of non-thermal electron transport and radiation signatures will once more be the subject of some attention, since this is an integral part of the calculation of the spectral and spatial behavior of the radiative signatures which will be observed by HESSI. Problems of particle transport in coronal magnetic traps are often treated by making simple geometrical and timescale arguments for the fractions of accelerated particles which are trapped and precipitate from coronal loops. Such arguments are used to calculate the populations of, for example, directly precipitating and trap-precipitating particles (which can in principle be identified from hard X-ray time-series), or coronal versus footpoint emission ratios (which can be studied from spatially resolved HXR data). Using numerical simulation and analytic arguments we have studied the dynamics of particles within coronal traps, paying particular attention to the behavior in the vicinity of the loss-cone. We find that over a broad range of normally-assumed coronal parameters, such as mirror-ratio, loop length and loop density, (a) electrons cannot pass easily from the trap region to the loss-cone, so that (b) there is no collisionless trap-precipitating component and (c) a large fraction of accelerated particles will lose their entire energy budget within the coronal loop. We discuss what this means for our current understanding of the solar flare environment and our interpretation of radiative signatures. This work was supported by the Yohkoh/SXT project at LMSAL (NASA grant NAS8-40801) and by the U.K. Particle Physics and Astronomy Research Council. Title: Dynamics in Restructuring Active Regions Observed During Soho/Yohkoh/Gbo Campaigns Authors: Schmieder, B.; Deng, Y.; Mandrini, C. H.; Rudawy, P.; Nitta, N.; Mason, H.; Fletcher, L.; Martens, P.; Brynildsen, N. Bibcode: 2000AdSpR..25.1879S Altcode: JOP17 and JOP 33 are SOHO Joint Observing Programs in collaboration with Yohkoh/SXT and ground based observatories (GBO's), dedicated to observe dynamical events through the atmosphere. During runs of these programs we observed in restructuring active regions (ARs), surges, subflares, bright knots, but not large flares and jets. From these observations we have been able to derive some of the responses of the coronal and chromospheric plasma to the evolution of the photospheric magnetic field. Emerging flux in an AR led to the formation of Arch Filament Systems in the chromosphere, hot loops and knots in the transition region, and X-ray loops. Frequent surges have been observed in relation to parasitic or mixed polarities, but coronal jets have not yet been found. We discuss the possible mechanisms acting during the restructuring of the active regions (reconnection or ``sea-serpent'' geometries) Title: High-resolution Observations of Plasma Jets in the Solar Corona Authors: Alexander, David; Fletcher, Lyndsay Bibcode: 1999SoPh..190..167A Altcode: We present recent observations of coronal jets, made by TRACE and Yohkoh/SXT on 28 May and 19 August 1998. The high spatial resolution of TRACE enables us to see in detail the process of material ejection; in the line of Fe ix (one million degrees) we see both bright emitting material and dark absorbing/scattering material being ejected, i.e., both hot and cold material, highly collimated and apparently ejected along the direction of the overlying field lines. Bright ejecta are seen simultaneously in Lyman α for one event and Yohkoh/SXT in the other. The jets on the two days are different in that the 19 August jet displays the morphology typical of a one-sided anemone jet while the 28 May jet exhibits a two-sided jet morphology. The 19 August jet shows evidence for rotation and an interesting bifurcation at large distances from the energy release site. We study the physical properties and energetics of these jetting events, and conclude that existing theoretical models capture the essential physics of the jet phenomena. Title: Looptop Hard X-ray Sources Authors: Fletcher, L. Bibcode: 1999ESASP.448..693F Altcode: 1999mfsp.conf..693F; 1999ESPM....9..693F No abstract at ADS Title: What is Moss? Authors: Berger, T. E.; De Pontieu, B.; Fletcher, L.; Schrijver, C. J.; Tarbell, T. D.; Title, A. M. Bibcode: 1999SoPh..190..409B Altcode: TRACE observations of active regions show a peculiar extreme ultraviolet (EUV) emission over certain plage areas. Termed `moss' for its spongy, low-lying, appearance, observations and modeling imply that the phenomenon is caused by thermal conduction from 3-5 MKcoronal loops overlying the plage: moss is the upper transition region emission of hot coronal loops. The spongy appearance is due to the presence of chromospheric jets or `spicules' interspersed with the EUV emission elements. High cadence TRACE observations show that the moss EUV elements interact with the chromospheric jets on 10 s time scales. The location of EUV emission in the moss does not correlate well to the locations of underlying magnetic elements in the chromosphere and photosphere, implying a complex magnetic topology for coronal loop footpoint regions. We summarize here the key observations leading to these conclusions and discuss new implications for understanding the structuring of the outer solar atmosphere. Title: Plasma Diagnostics of Transition Region ``Moss'' using SOHO/CDS and TRACE Authors: Fletcher, Lyndsay; De Pontieu, Bart Bibcode: 1999ApJ...520L.135F Altcode: Recent observations of solar active regions with the Transition Region and Coronal Explorer (TRACE) have revealed finely textured, low-lying EUV emission, called the ``moss,'' appearing as a bright dynamic pattern with dark inclusions. The moss has been interpreted as the upper transition region by Berger and coworkers. In this study we use SOHO Coronal Diagnostic Spectrometer and TRACE observations of Active Region 8227 on 1998 May 30 to determine the physical parameters of the moss material. We establish that the plasma responsible for the moss emission has a temperature range of (0.6-1.5)×106 K and is associated with hot loops (T>2×106 K). Moss plasma has an electron density of (2-5)×109 cm-3 at a temperature of 1.3×106 K, giving a pressure of 0.7-1.7 dynes cm-2 (a few times higher than in coronal loops observed in the TRACE Fe IX/X λ171 passband). The volume filling factor of the moss plasma is of order 0.1, and the path along which the emission originates is of order 1000 km long. Title: Coronal Loop Oscillations Observed with the Transition Region and Coronal Explorer Authors: Aschwanden, Markus J.; Fletcher, Lyndsay; Schrijver, Carolus J.; Alexander, David Bibcode: 1999ApJ...520..880A Altcode: We report here, for the first time, on spatial oscillations of coronal loops, which were detected in extreme-ultraviolet wavelengths (171 Å) with the Transition Region and Coronal Explorer, in the temperature range of Te~1.0-1.5 MK. The observed loop oscillations occurred during a flare that began at 1998 July 14, 12:55 UT and are most prominent during the first 20 minutes. The oscillating loops connect the penumbra of the leading sunspot to the flare site in the trailing portion. We identified five oscillating loops with an average length of L=130,000+/-30,000 km. The transverse amplitude of the oscillations is A=4100+/-1300 km, and the mean period is T=280+/-30 s. The oscillation mode appears to be a standing wave mode (with fixed nodes at the footpoints). We investigate different MHD wave modes and find that the fast kink mode with a period τ=205(L/1010 cm)(ne/109 cm-3)1/2(B/10 G)-1 s provides the best agreement with the observed period. We propose that the onset of loop oscillations in distant locations is triggered by a signal or disturbance that propagates from the central flare site with a radial speed of ~700 km s-1. Because the observed loop oscillation periods are comparable to photospheric 5 minute oscillations, a resonant coupling between the two systems is possible. We further find evidence for global extreme-UV dimming in the entire active region possibly associated with a coronal mass ejection. Title: A new view of the solar outer atmosphere by the Transition Region and Coronal Explorer Authors: Schrijver, C. J.; Title, A. M.; Berger, T. E.; Fletcher, L.; Hurlburt, N. E.; Nightingale, R. W.; Shine, R. A.; Tarbell, T. D.; Wolfson, J.; Golub, L.; Bookbinder, J. A.; DeLuca, E. E.; McMullen, R. A.; Warren, H. P.; Kankelborg, C. C.; Handy, B. N.; De Pontieu, B. Bibcode: 1999SoPh..187..261S Altcode: The Transition Region and Coronal Explorer (TRACE) - described in the companion paper by Handy et al. (1999) - provides an unprecedented view of the solar outer atmosphere. In this overview, we discuss the initial impressions gained from, and interpretations of, the first million images taken with TRACE. We address, among other topics, the fine structure of the corona, the larger-scale thermal trends, the evolution of the corona over quiet and active regions, the high incidence of chromospheric material dynamically embedded in the coronal environment, the dynamics and structure of the conductively dominated transition region between chromosphere and corona, loop oscillations and flows, and sunspot coronal loops. With TRACE we observe a corona that is extremely dynamic and full of flows and wave phenomena, in which loops evolve rapidly in temperature, with associated changes in density. This dynamic nature points to a high degree of spatio-temporal variability even under conditions that traditionally have been referred to as quiescent. This variability requires that coronal heating can turn on and off on a time scale of minutes or less along field-line bundles with cross sections at or below the instrumental resolution of 700 km. Loops seen at 171 Å (∼1 MK) appear to meander through the coronal volume, but it is unclear whether this is caused by the evolution of the field or by the weaving of the heating through the coronal volume, shifting around for periods of up to a few tens of minutes and lighting up subsequent field lines. We discuss evidence that the heating occurs predominantly within the first 10 to 20 Mm from the loop footpoints. This causes the inner parts of active-region coronae to have a higher average temperature than the outer domains. Title: Deconvolution of Directly Precipitating and Trap-precipitating Electrons in Solar Flare Hard X-Rays. III.Yohkoh Hard X-Ray Telescope Data Analysis Authors: Aschwanden, Markus J.; Fletcher, Lyndsay; Sakao, Taro; Kosugi, Takeo; Hudson, Hugh Bibcode: 1999ApJ...517..977A Altcode: We analyze the footpoint separation d and flux asymmetry A of magnetically conjugate double footpoint sources in hard X-ray images from the Yohkoh Hard X-Ray Telescope (HXT). The data set of 54 solar flares includes all events simultaneously observed with the Compton Gamma Ray Observatory (CGRO) in high time resolution mode. From the CGRO data we deconvolved the direct-precipitation and trap-precipitation components previously (in Paper II). Using the combined measurements from CGRO and HXT, we develop an asymmetric trap model that allows us to quantify the relative fractions of four different electron components, i.e., the ratios of direct-precipitating (qP1, qP2) and trap-precipitating electrons (qT1, qT2) at both magnetically conjugate footpoints. We find mean ratios of qP1=0.14+/-0.06, qP2=0.26+/-0.10, and qT=qT1+qT2=0.60+/-0.13. We assume an isotropic pitch-angle distribution at the acceleration site and double-sided trap precipitation (qT2/qT1=qP2/qP1) to determine the conjugate loss-cone angles (α1=42deg+/-11deg and α2=52deg+/-10deg) and magnetic mirror ratiosat both footpoints (R1=1.6,...,4.0 and R2=1.3,...,2.5). From the relative displacement of footpoint sources we also measure altitude differences of hard X-ray emission at different energies, which are found to decrease systematically with higher energies, with a statistical height difference of hLo-hM1=980+/-250 km and hM1-hM2=310+/-300 km between the three lower HXT energy channels (Lo, M1, M2). Title: Plasma Diagnostics of Transition Region ``Moss'' using SOHO/CDS and TRACE Authors: Fletcher, L.; de Pontieu, B. Bibcode: 1999AAS...194.7902F Altcode: 1999BAAS...31..963F Recent observations of solar active regions with the Transition Region And Coronal Explorer (TRACE) have revealed finely textured, low-lying extreme ultraviolet (EUV) emission, called the ``moss'', appearing as a bright dynamic pattern with dark inclusions. The moss has been interpreted as the upper transition region by Berger et al., (1999). In this study we use simultaneous SOHO Coronal Diagnostic Spectrometer (CDS) and TRACE observations of Active Region (AR) 8227 on 30-May-1998 to determine the physical parameters of the moss material. A differential emission measure (DEM) analysis and other diagnostic tools establish that the plasma responsible for the moss emission has a temperature range of 0.6-1.5 * 10(6) K and is associated with hot loops (T > 2 * 10(6) K) observed with CDS. This plasma has an electron density of 2-5* 10(9) cm(-3) at a temperature of 1.3 * 10(6) K, giving a pressure of 0.7-1.7 dyne cm(-2) . Both the density and pressure in the moss plasma are a few times higher than in coronal loops observed in the TRACE Fe IX/X 171 Angstroms passband. The volume filling factor of the moss plasma is of the order 0.1 and the path along which the emission originates is of the order 1,000 km long. Title: Dynamics and Plasma Diagnostics of Transition Region ``Moss'' using SOHO/CDS, TRACE and SVST (La Palma) Authors: de Pontieu, B.; Berger, T. E.; Fletcher, L.; Schrijver, C. J.; Title, A. M. Bibcode: 1999AAS...194.7804D Altcode: 1999BAAS...31..961D Recent observations of solar active regions with the Transition Region And Coronal Explorer (TRACE) have revealed finely textured, low-lying extreme ultraviolet (EUV) emission, called the ``moss'', appearing as a bright dynamic pattern with dark inclusions. The moss has been interpreted as the upper transition region by Berger et al., (1999). In this poster we study the physical conditions in the moss plasma, as well as its dynamics and connections to photosphere and chromosphere. Using simultaneous SOHO Coronal Diagnostic Spectrometer (CDS) and TRACE observations of Active Region (AR) 8227 on 30-May-1998 we determine the physical parameters of the moss material. We find T_e = 0.6-1.5 10(6) K and n_e = 2-5 10(9) cm(-3) at a temperature of 1.3 10(6) K. The pressure in the moss plasma is higher than that in coronal loops observed in the TRACE Fe IX/X 171 Angstroms passband, and moss emission is associated with high temperature loops, observed by SXT and by CDS in lines of T_max > 2.5 10(6) K. The volume filling factor of the moss plasma is of the order 0.1 and the path along which the emission originates is of the order 1,000 km long. We examine the dynamics of the moss plasma, by making comparisons of TRACE 171 Angstroms movies with SVST (La Palma) Ca II K-line, Hα , and G-band movies. Local Correlation Tracking (LCT) flowmapping techniques are used to establish the photospheric flowfield in plage regions with and without associated moss. The relation of moss emission to chromospheric spicules or fibrils is examined in detail using Hα movies and dopplergrams. In addition, several miniflare events occuring in plage regions are analyzed using TRACE and SVST movies. This research was supported by NASA contract NAS5-38099 (TRACE) and NASA SR&T grant NASW-98008. Title: Rendering Three-Dimensional Solar Coronal Structures of Active Region 8227 Authors: Gary, G. A.; Alexander, D.; Fletcher, L. Bibcode: 1999AAS...194.7807G Altcode: 1999BAAS...31..962G Coronal X-ray and EUV synthesized images of Active Region 8227 (May-June 1996) are constructed and compared with TRACE, Yohkoh/SXT, and SOHO/EIT observations. Using the rendering technique of Gary (1997) and Alexander, Gary, and Thompson (1998), specific geometric and physical models are used to integrate the plasma emission along the line of sight to obtain a rendered image. The instrumental profiles are convolved in the integration process as well as unique heating functions. We analyze coronal X-ray and EUV structures via the constructing of synthesized images and investigate how different heating rates within the active region loop system affect the emission characteristics. The intercomparison of the emission seen in different telescopes with that predicted by the assumed model provides a diagnostic tool for determining the properties of the heating and a physical explanation for the observed distributions. Of particular note is the presence of bright EUV emission at the base of hot X-ray loops, reminiscent of the "moss" observed by Berger & et al. (1999), and Fletcher & De Pontieu (1999). Gary, G. A.: 1997, Solar Physics, 174, 241. Alexander, D., Gary, G. A., and Thompson, B.J.: 1998, Proc. 2nd ASPE, PASP Conference Series. Berger, T. E., De Pontieu, B., Schrijver, C. J., Title, A. M., 1999. ApJ Letts. (submitted) Fletcher, L., De Pontieu, B. 1999, ApJ Letts. (submitted) Title: Calentamiento de arcos coronales en una región activa por reconfiguración topológica del campo magnético. Authors: López Fuentes, M.; Mandrini, C. H.; Démoulin, P.; Schmieder, B.; Fletcher, L.; Mason, H. Bibcode: 1999BAAA...43...24L Altcode: We study the active region (AR) 8048 observed on June 1997 in several wavelenghts. The combined observations obtained using CDS (SOHO) and SXT (Yohkoh) show the heating of the coronal magnetic loops at different atmospheric altitudes. Extrapolating the magnetic field in the corona from longitudinal magnetograms from MDI (SOHO), we determine the location of Bald Patches in the surroundings of the leading spot. This magnetic feature, the emergence of parasitic magnetic polarities and the observed photospheric motions provide the conditions to explain the observed heating. Title: Generation of solar Hα impact polarization by fragmented evaporative upflows Authors: Fletcher, L.; Brown, J. C. Bibcode: 1998A&A...338..737F Altcode: In this paper a novel mechanism is proposed for the generation of Hα impact polarization observed during some solar flares. Rather than being generated by the primary particle beams transporting energy from the chromosphere to the corona, we suggest that following heating, the solar chromosphere evaporates in a fragmented manner, and that impact excitations in the regions of interaction of hot evaporating and cool non-evaporating material locally generates impact-polarized Hα emission. This thermal upflow model is more consistent with the large areas and times over which polarization is observed than are beam models. A simple model for the process is given, and the resulting polarization is calculated and compared with observations, under two assumptions about the number density of neutral particles in the interaction regions. Title: A Model for Hard X-Ray Emission from the Top of Flaring Loops Authors: Fletcher, L.; Martens, P. C. H. Bibcode: 1998ApJ...505..418F Altcode: The frequent occurrence of hard X-ray emission from the top of flaring loops was one of the discoveries by the Hard X-Ray Telescope on board the Japanese Yohkoh satellite. In this paper we take a flare current-sheet geometry and show how the combined effect of magnetic field convergence and pitch-angle scattering of nonthermal electrons injected at the top of the loop results in the generation of a looptop source with properties akin to those observed by Yohkoh. We demonstrate that a looptop source can be produced in both impulsive and gradual phase loops. We further present a possible mechanism for the generation of high-temperature ``ridges'' in the loop legs. Title: A Possible Third Festoon Flow in Atalanta Planitia, Venus Authors: Fletcher, L.; Wright, H.; Grosfils, E.; Reinen, L.; Gilmore, M.; Kozak, S. Bibcode: 1998LPI....29.1188F Altcode: No abstract at ADS Title: Hard X-Ray Emission from a Mirror Trap at the Top of Reconnecting Loops Authors: Martens, P. C. H.; Fletcher, L. Bibcode: 1998ASSL..229..269M Altcode: 1998opaf.conf..269M No abstract at ADS Title: Surges and filaments in active regions during SOHO campaigns Authors: Schmieder, B.; Deng, Y.; Rudawy, P.; Nitta, N.; Mandrini, C. H.; Fletcher, L.; Martens, P.; Innes, D.; Young, P.; Mason, H. Bibcode: 1998ESASP.421..323S Altcode: 1998sjcp.conf..323S No abstract at ADS Title: SOHO: een zonne-observatorium in de ruimte. Authors: Fletcher, L. Bibcode: 1998Zenit..25....4F Altcode: No abstract at ADS Title: Numerical simulations of coronal particle trapping. Authors: Fletcher, L. Bibcode: 1997A&A...326.1259F Altcode: In this paper the trapping of high energy particles in solar coronal loops is addressed. Using simulations, the time evolution of electrons and protons trapped in a magnetic bottle is calculated under various scattering conditions and the results compared with loss-cone analysis. Thereafter the case of time-dependent injection into a magnetic loop is addressed, and the results compared with previous analytic work on X and γ-ray delay times. Title: Magnetic pumping in the cataclysmic variable AE Aquarii. Authors: Kuijpers, J.; Fletcher, L.; Abada-Simon, M.; Horne, K. D.; Raadu, M. A.; Ramsay, G.; Steeghs, D. Bibcode: 1997A&A...322..242K Altcode: We propose that the radio outbursts of the cataclysmic variable AE Aqr are caused by eruptions of bubbles of fast particles from a magnetosphere surrounding the white dwarf. We investigate the acceleration process of magnetic pumping in the magnetosphere which is periodically driven both by the relative motion with the companion and with the infalling spray of gas at the spin frequency of the white dwarf. As the accretion rate is relatively low, the conversion of spin energy into acceleration (rather than heating) of electrons and protons can be efficient. The accelerated particles are trapped in the white dwarf magnetosphere until their total energy content becomes comparable to that of the trapping magnetic field structure and a MHD instability sets in. Synchrotron radiation is emitted in the expelled expanding plasmoid at radio and down to millimetric wavelengths. We find that there is sufficient energy transferred from the rotation energy of the rapidly-spinning white dwarf to fast particles by magnetic pumping to explain quiescent and flaring radio emissions. Title: Particle Acceleration and Transport in Reconnecting Plasmas Authors: Fletcher, Lyndsay; Petkaki, Panagiota Bibcode: 1997SoPh..172..267F Altcode: 1997ESPM....8..267F We model the behaviour of particles in and around X-type magnetic configurations, a possible solar flare reconnection geometry. Particles are accelerated by a time-varying electric field close to the neutral point, and followed by integrating the equations of motion. When their motion becomes adiabatic a stochastic simulation is used to model their further transport in a collisional magnetised medium. Title: O^{5+} Acceleration by Turbulence in Polar Coronal Holes Authors: Fletcher, L.; Huber, M. C. E. Bibcode: 1997ESASP.404..379F Altcode: 1997cswn.conf..379F No abstract at ADS Title: Are Coronal Mass Ejections Caused by Magnetic Pumping? Authors: Kuijpers, Jan; Fletcher, Lyndsay Bibcode: 1996SoPh..169..415K Altcode: Magnetic pumping in the solar corona is revisited. We derive conditions under which magnetic pumping can be the cause of heating of loops rather than of particle acceleration. Candidate sources for such a process are coronal mass ejections (CMEs). Large loops are susceptible to heating primarily of protons by magnetic compressions with periods between 50 and 5000 s, the observed spectrum of the photospheric driver. Efficient heating by pumping occurs since in these large loops the density is low enough that the proton-proton collision time is comparable to the periods of the external compressions. We suggest that CMEs may be pressure-driven explosions of large-beta loops caused by magnetic pumping, in contrast to current-driven `flares' in low-beta environments. Title: The height distribution of non-thermal X-ray sources in impulsive solar flares. Authors: Fletcher, L. Bibcode: 1996A&A...310..661F Altcode: In this paper we use numerical simulations to accurately model the evolution of non-thermal electron distributions in coronal loops, from which we calculate electron bremsstrahlung height versus energy distributions. The results are compared with results of the Yohkoh satellite and it is found that a model taking into account the full complexity of electron transport can explain what is observed, for quite reasonable loop parameters. We test three loop models, the first with no field convergence, the second with field convergence occurring rapidly and only in the chromosphere and the third where field convergence occurs slowly in the corona. We demonstrate the effects of varying parameters of the loop (such as density, length and field strength), and of the beam (spectral index, pitch angle distribution) and outline parameter regimes in which best agreement with the data can be found. Broadly, densities between 2x10^10^ and 3x10^11^cm^-3^ and coronal half-lengths L=~1.3-2.7x10^9^cm give qualitatively acceptable results. Finally we discuss possible tests to distinguish between the various models which can explain the height distribution. Title: Triggering the radio emission from AE Aqr: Authors: Steeghs, D.; Kuijpers, J.; Fletcher, L.; et al. Bibcode: 1996ASSL..208..167S Altcode: 1996IAUCo.158..167S; 1996cvro.coll..167S No abstract at ADS Title: On Determining Flare Beam Parameters from Loop-top Hard X-ray Sources Authors: Fletcher, L. Bibcode: 1996ApL&C..34..151F Altcode: No abstract at ADS Title: Radio Emission from AE Aquarii Authors: Abada-Simon, M.; Bastian, T. S.; Fletcher, L.; Horne, K.; Kuijpers, J.; Steeghs, D.; Bookbinder, J. A. Bibcode: 1996ASPC...93..182A Altcode: 1996ress.conf..182A No abstract at ADS Title: The Height Distribution of Hard X-rays in Impulsive Solar Flares Authors: Fletcher, L. Bibcode: 1996mpsa.conf..549F Altcode: 1996IAUCo.153..549F No abstract at ADS Title: On the generation of loop-top impulsive hard X-ray sources. Authors: Fletcher, L. Bibcode: 1995A&A...303L...9F Altcode: Recently observed with the Hard X-ray Telescope onboard Yohkoh, loop-top hard X-ray sources have focussed interest on energy release in solar flares. Possibly a direct indication of the site of particle acceleration, they have thus far only been interpreted as thermal sources. In this letter we propose instead that the sources arise as a result of transport effects, and show using a stochastic simulation of non-thermal electron transport in a simple loop model, that many characteristics of the loop-top source can be reproduced. Title: Solar flare Hα impact polarization from high energy electrons? Authors: Fletcher, L.; Brown, J. C. Bibcode: 1995A&A...294..260F Altcode: In this paper we investigate the possibility of obtaining Hα line linear polarization in solar flares following the excitation of neutral hydrogen by energetic electron beams with a large initial pitch angle. We compare the factors affecting the sign, magnitude and intensity of polarized radiation collisionally excited by electron and proton beams and present a calculation of the polarization which could be observed from an electron beam, using a stochastic simulation to solve the Fokker-Planck evolution equation for the electron beam in the collisionally thick chromosphere, in the presence of a converging magnetic field. We find that polarization from electron beams is possible but requires extreme energy fluxes which are unlikely to be present for any length of time during solar flares. Title: Modelling particle transport with stochastic simulations Authors: Fletcher, Lyndsay Bibcode: 1994SSRv...68..239F Altcode: We use stochastic simulations to calculate the evolution of particle distributions in complex situations. Comparison of numerical and analytical solutions is made, for the case of electrons moving from the corona to the chromosphere and undergoing pure scattering. A temporally fragmented beam injection is treated, under various atmospheric conditions. Title: Foreword Authors: van den Oord, Bert; Kuijpers, Jan; Kuperus, Max; Benz, A. O.; Brown, J. C.; Einaudi, G.; Kuperus, M.; Raadu, M. A.; Trottet, G.; van den Oord, G. H. J.; Vlahos, L.; Zheleznyakov, V. V.; Wijburg, Marion; Fletcher, Lyndsay; Volwerk, Martin Bibcode: 1994SSRv...68D..17V Altcode: No abstract at ADS Title: Hα impact polarization as a solar and astrophysical particle diagnostic Authors: Fletcher, Lyndsay Bibcode: 1993PhDT.......113F Altcode: No abstract at ADS Title: H-alpha polarization of wind-heated optical bullets in SS 433. Authors: Brown, J. C.; Fletcher, L. Bibcode: 1992A&A...259L..43B Altcode: Mechanisms for energy supply to the optical bullets are discussed. It is pointed out that in the case of heating by bullet collisions with the system wind, recently shown to be a likely heating candidate, impact polarization of the H-alpha line should be generated. An estimate shows that this line polarization should be at least 0.2 percent and orthogonal to the jet, precessing with it on the sky. This should be observable and is proposed as a diagnostic of the wind heating model, in contrast to turbulent internal heating. Title: Asymmetric Flux Loops in Active Regions - Part Two Authors: Petrovay, K.; Brown, J. C.; van Driel-Gesztelyi, L.; Fletcher, L.; Marik, M.; Stewart, G. Bibcode: 1990SoPh..127...51P Altcode: We propose that magnetic flux loops in the subphotospheric layers of the Sun are seriously asymmetrical as a consequence of the drag force exerted on them because of the different rotational rate of the surrounding plasma. In numerical models of stationary slender flux loops in the plane parallel approximation we show that a serious tilt is both possible and probable. Observational facts (see van Driel-Gesztelyi and Petrovay, 1989; Paper I) strongly support the case for high asymmetry. The different stability of p and f spots may also be related to such an asymmetry. Title: Aerodynamic heating and thermal protection systems Authors: Fletcher, L. S. Bibcode: 1978PrAA...59.....F Altcode: The aerothermal environment is considered, taking into account the aerothermal environment for the Pioneer Venus multiprobe mission, shuttle elevon cove aerodynamic heating by ingested flow, aerothermodynamic base heating, vortices induced in a stagnation region by wakes, three-dimensional shock-wave interference heating prediction, methods for predicting radiation-coupled flowfields about planetary entry probes, shock-tube studies of silicon-compound vapors, and Mach number and wall temperature effects on turbulent heat blockage. A comparison of calculated and measured rocket plume infrared radiation is discussed along with a band model for calculating radiance and transmission of water vapor and carbon dioxide, and a comparison of theoretical and experimental infrared radiation from a rocket exhaust. Thermal protection systems are examined and attention is given to the effect of melt removal by aerodynamic shear on melt-through of metal plates, the ablation performance of tungsten and copper-infiltrated tungsten systems in arc jets, the asymmetric nose-tip shape change during atmospheric entry, the high-pressure arc test performance of carbon-carbon nose tips, and segmented tungsten nose tips for high-performance flight vehicles. Individual items were announced in issues 07, 08, 17, and 18, 1977. Title: A Search for a Buried Meteorite Authors: Fletcher, L. Bibcode: 1906Natur..74..490F Altcode: No abstract at ADS Title: L'Uranolithe de Crumlin Authors: Fletcher, L. Bibcode: 1903BSAFR..17..142F Altcode: No abstract at ADS Title: Fall of a Meteoric Stone near Crumlin (Co. Antrim) September 13 Authors: Fletcher, L. Bibcode: 1902Natur..66..577F Altcode: No abstract at ADS Title: The Supposed Occurrence of Widespread Meteoritic Showers Authors: Fletcher, L. Bibcode: 1891Natur..43R.295F Altcode: No abstract at ADS