Author name code: lagg ADS astronomy entries on 2022-09-14 author:"Lagg, Andreas" ------------------------------------------------------------------------ Title: Polarimetric calibration of the Sunrise UV Spectropolarimeter and Imager Authors: Iglesias, F. A.; Feller, A.; Gandorfer, A.; Lagg, A.; Riethmüller, T. L.; Solanki, S. K.; Katsukawa, Y.; Kubo, M.; Zucarelli, G.; Sanchez, M.; Sunrise Team Bibcode: 2022BAAA...63..305I Altcode: Sunrise is an optical observatory mounted in a stratospheric balloon, developed to study magnetic fields in the solar atmosphere with very high resolution. In its third flight, Sunrise carry the Sunrise UV Spectropolarimeter and Imager (SUSI), that operates in the 313-430 nm range, covering thousands of spectral lines not accessible from the ground and thus largely unexplored. SUSI does not include a polarimetric calibration unit on board. We report about the development status of SUSI and the preliminary results of its calibration. Title: Magnetized supersonic downflows in the chromosphere. A statistical study using the He I 10 830 Å lines Authors: Sowmya, K.; Lagg, A.; Solanki, S. K.; Castellanos Durán, J. S. Bibcode: 2022A&A...661A.122S Altcode: 2022arXiv220211679S The chromosphere above active regions (ARs) on the Sun hosts magnetized supersonic downflows. Studies of these supersonic downflows help to decipher the magnetic fine structure and dynamics of the chromosphere. We perform a statistical analysis of the magnetized supersonic downflows in a number of ARs at different evolutionary stages and survey their characteristics. We analyze spectro-polarimetric scans of parts of 13 ARs obtained in the infrared He I 10 830 Å triplet formed in the upper chromosphere recorded with the GREGOR Infrared Spectrograph mounted at the GREGOR solar telescope. We retrieve the line-of-sight velocities and the magnetic field vector using the HELIX+ inversion code that assumes Milne-Eddington atmospheres. We find magnetized supersonic downflows in all the ARs, with larger area coverage by such flows in ARs observed during their emerging phase. The fact that supersonic downflows were detected in all scans, albeit only covering a small fraction, 0.2-6.4%, of the observed field-of-view, suggests that they are a comparatively common phenomenon in the upper chromospheres of ARs. The supersonic downflows are found to be associated with many AR features, such as pores, sunspot umbrae, sunspot penumbrae, light bridges, plages, He I loops as part of arch filament systems characteristic of emerging fields, and filaments. Although several mechanisms are identified to be causing the supersonic downflows, by far the most common one appears to be the draining of plasma along the legs of rising magnetic loops. The loops mainly drain into forming pores. The line-of-sight velocities of the supersonic downflows reach values of up to 49 km s−1, and the velocity distribution shows multiple populations. Almost 92% of these supersonic downflows coexist with a subsonic flow component. The weaker, more horizontal fields associated with the supersonic component suggests that it is formed above the subsonic component. Title: The magnetic drivers of campfires seen by the Polarimetric and Helioseismic Imager (PHI) on Solar Orbiter Authors: Kahil, F.; Hirzberger, J.; Solanki, S. K.; Chitta, L. P.; Peter, H.; Auchère, F.; Sinjan, J.; Orozco Suárez, D.; Albert, K.; Albelo Jorge, N.; Appourchaux, T.; Alvarez-Herrero, A.; Blanco Rodríguez, J.; Gandorfer, A.; Germerott, D.; Guerrero, L.; Gutiérrez Márquez, P.; Kolleck, M.; del Toro Iniesta, J. C.; Volkmer, R.; Woch, J.; Fiethe, B.; Gómez Cama, J. M.; Pérez-Grande, I.; Sanchis Kilders, E.; Balaguer Jiménez, M.; Bellot Rubio, L. R.; Calchetti, D.; Carmona, M.; Deutsch, W.; Fernández-Rico, G.; Fernández-Medina, A.; García Parejo, P.; Gasent-Blesa, J. L.; Gizon, L.; Grauf, B.; Heerlein, K.; Lagg, A.; Lange, T.; López Jiménez, A.; Maue, T.; Meller, R.; Michalik, H.; Moreno Vacas, A.; Müller, R.; Nakai, E.; Schmidt, W.; Schou, J.; Schühle, U.; Staub, J.; Strecker, H.; Torralbo, I.; Valori, G.; Aznar Cuadrado, R.; Teriaca, L.; Berghmans, D.; Verbeeck, C.; Kraaikamp, E.; Gissot, S. Bibcode: 2022A&A...660A.143K Altcode: 2022arXiv220213859K Context. The Extreme Ultraviolet Imager (EUI) on board the Solar Orbiter (SO) spacecraft observed small extreme ultraviolet (EUV) bursts, termed campfires, that have been proposed to be brightenings near the apexes of low-lying loops in the quiet-Sun atmosphere. The underlying magnetic processes driving these campfires are not understood.
Aims: During the cruise phase of SO and at a distance of 0.523 AU from the Sun, the Polarimetric and Helioseismic Imager on Solar Orbiter (SO/PHI) observed a quiet-Sun region jointly with SO/EUI, offering the possibility to investigate the surface magnetic field dynamics underlying campfires at a spatial resolution of about 380 km.
Methods: We used co-spatial and co-temporal data of the quiet-Sun network at disc centre acquired with the High Resolution Imager of SO/EUI at 17.4 nm (HRIEUV, cadence 2 s) and the High Resolution Telescope of SO/PHI at 617.3 nm (HRT, cadence 2.5 min). Campfires that are within the SO/PHI−SO/EUI common field of view were isolated and categorised according to the underlying magnetic activity.
Results: In 71% of the 38 isolated events, campfires are confined between bipolar magnetic features, which seem to exhibit signatures of magnetic flux cancellation. The flux cancellation occurs either between the two main footpoints, or between one of the footpoints of the loop housing the campfire and a nearby opposite polarity patch. In one particularly clear-cut case, we detected the emergence of a small-scale magnetic loop in the internetwork followed soon afterwards by a campfire brightening adjacent to the location of the linear polarisation signal in the photosphere, that is to say near where the apex of the emerging loop lays. The rest of the events were observed over small scattered magnetic features, which could not be identified as magnetic footpoints of the campfire hosting loops.
Conclusions: The majority of campfires could be driven by magnetic reconnection triggered at the footpoints, similar to the physical processes occurring in the burst-like EUV events discussed in the literature. About a quarter of all analysed campfires, however, are not associated to such magnetic activity in the photosphere, which implies that other heating mechanisms are energising these small-scale EUV brightenings. Title: Similarities of magnetoconvection in the umbra and in the penumbra of sunspots Authors: Löptien, B.; Lagg, A.; van Noort, M.; Solanki, S. K. Bibcode: 2021A&A...655A..61L Altcode: 2021arXiv211001352L Context. It is unclear why there is a rather sharp boundary in sunspots between the umbra and the penumbra. Both regions exhibit magnetoconvection, which manifests in penumbral filaments in the penumbra and in umbral dots in the umbra.
Aims: Here we compare the physical properties of umbral dots and penumbral filaments. Our goal is to understand how the properties of these convective features change across the boundary between the umbra and the penumbra and how this is related to the rapid increase in brightness at the umbra-penumbra boundary.
Methods: We derived ensemble averages of the physical properties of different types of convective features based on observations of two sunspots with Hinode.
Results: There are strong similarities between the convective features in the outer parts of the umbra and the ones in the penumbra, with most physical parameters being smooth and continuous functions of the length of the features.
Conclusions: Our results indicate that the transition in brightness from the umbra to the penumbra is solely caused by an increased effectiveness of magnetoconvection within individual convective cells. There is no significant difference in the number density of convective elements between the outer umbra and the inner penumbra. Penumbral filaments exhibit a larger area and a higher brightness compared to umbral dots. It is still unclear how exactly the underlying magnetic field causes the increase in the size and brightness of convective features in the penumbra. Title: Inferring magnetic helicity spectrum in spherical domains: Method and example applications Authors: Prabhu, A. P.; Singh, N. K.; Käpylä, M. J.; Lagg, A. Bibcode: 2021A&A...654A...3P Altcode: 2021arXiv210407588P Context. Obtaining observational constraints on the role of turbulent effects for the solar dynamo is a difficult, yet crucial, task. Without such knowledge, the full picture of the operation mechanism of the solar dynamo cannot be formed.
Aims: The magnetic helicity spectrum provides important information about the α effect. Here we demonstrate a formalism in spherical geometry to infer magnetic helicity spectra directly from observations of the magnetic field, taking into account the sign change of magnetic helicity across the Sun's equator.
Methods: Using an angular correlation function of the magnetic field, we develop a method to infer spectra for magnetic energy and helicity. The retrieval of the latter relies on a fundamental definition of helicity in terms of linkage of magnetic flux. We apply the two-scale approach, previously used in Cartesian geometry, to spherical geometry for systems where a sign reversal of helicity is expected across the equator on both small and large scales.
Results: We test the method by applying it to an analytical model of a fully helical field, and to magneto-hydrodynamic simulations of a turbulent dynamo. The helicity spectra computed from the vector potential available in the models are in excellent agreement with the spectra computed solely from the magnetic field using our method. In a next test, we use our method to obtain the helicity spectrum from a synoptic magnetic field map corresponding to a Carrington rotation. We observe clear signs of a bihelical spectrum of magnetic helicity, which is in complete accordance to the previously reported spectra in literature from the same map.
Conclusions: Our formalism makes it possible to infer magnetic helicity in spherical geometry, without the necessity of computing the magnetic vector potential. It has many applications in solar and stellar observations, but can also be used to analyse global magnetoconvection models of stars and to compare them with observations. Title: How rare are counter Evershed flows? Authors: Castellanos Durán, J. S.; Lagg, A.; Solanki, S. K. Bibcode: 2021A&A...651L...1C Altcode: 2021arXiv210605592S One of the main characteristics of sunspot penumbrae is the radially outward-directed Evershed flow. Only recently have penumbral regions been reported with similar characteristics to normal penumbral filaments but with an opposite direction of the flow. Such flows directed toward the umbra are known as counter Evershed flows (CEFs). We aim to determine the occurrence frequency of CEFs in active regions (ARs) and to characterize their lifetime and the prevailing conditions in the ARs. We analyzed the continuum images, Dopplergrams, and magnetograms recorded by SDO/HMI of 97 ARs that appeared from 2011 to 2017. We followed the ARs for 9.6 ± 1.4 days on average. We found 384 CEFs in total, with a median value of six CEFs per AR. Counter Evershed flows are a rather common feature, occurring in 83.5% of all ARs regardless of the magnetic complexity of the AR. However, CEFs were only observed, on average, during 5.9% of the mean total duration of all the observations analyzed here. The lifetime of CEFs follows a log-normal distribution with a median value of 10.6−6.0+12.4 h. In addition, we report two populations of CEFs, those that are associated with light bridges and those that are not. We explain that the rarity of reports of CEFs in the literature is a result of highly incomplete coverage of ARs with spectropolarimetric data. By using the continuous observations now routinely available from space, we are able to overcome this limitation. Title: The magnetic fine structure of the Sun's polar region as revealed by Sunrise Authors: Prabhu, A.; Lagg, A.; Hirzberger, J.; Solanki, S. K. Bibcode: 2020A&A...644A..86P Altcode: Context. Polar magnetic fields play a key role in the solar magnetic cycle and they are the source of a significant portion of the interplanetary magnetic field. However, observations of the poles are challenging and hence our understanding of the polar magnetic environment is incomplete.
Aims: We deduce properties of small-scale magnetic features in the polar region using high-resolution data and specifically aim to determine the flux per patch above which one magnetic polarity starts to dominate over the other.
Methods: We study the high spatial resolution, seeing-free observations of the north solar polar region, obtained with the IMaX instrument on-board the balloon-borne SUNRISE observatory during June 2009, at the solar activity minimum. We performed inversions of the full Stokes vector recorded by IMaX to retrieve atmospheric parameters of the Sun's polar region, mainly the temperature stratification and the magnetic field vector.
Results: We infer kilo-Gauss (kG) magnetic fields in patches harbouring polar faculae, without resorting to a magnetic filling factor. Within these patches we find the maxima of the magnetic field to be near the dark narrow lanes, which are shifted towards the disc centre side in comparison to the maxima in continuum intensity. In contrast, we did not find any fields parallel to the solar surface with kG strengths. In addition to the kG patches, we found the polar region to be covered in patches of both polarities, which have a range of sizes. We find the field strength of these patches to increase with increasing size and flux, with the smaller patches showing a significant dispersion in field strength. The dominating polarity of the north pole during this phase of the solar cycle is found to be maintained by the larger patches with fluxes above 2.3 × 1017 Mx. Title: The SUNRISE UV Spectropolarimeter and imager for SUNRISE III Authors: Feller, Alex; Gandorfer, Achim; Iglesias, Francisco A.; Lagg, Andreas; Riethmüller, Tino L.; Solanki, Sami K.; Katsukawa, Yukio; Kubo, Masahito Bibcode: 2020SPIE11447E..AKF Altcode: Sunrise is a balloon-borne solar observatory dedicated to the investigation of key processes of the magnetic field and the plasma flows in the lower solar atmosphere. The observatory operates in the stratosphere at an altitude of around 37 km in order to avoid image degradation due to turbulence in the Earth's atmosphere and to access the UV range. The third science flight of Sunrise will carry new instrumentation which samples the solar spectrum over a broad wavelength domain from the UV to the near IR and covers an extended height range in the solar atmosphere. A key feature of the Sunrise UV Spectropolarimeter and Imager (SUSI) operating between 309 nm and 417 nm, is its capability to simultaneously record a large number of spectral lines. By combining the spectral and polarization information of many individual lines with different formation heights and sensitivities, the accuracy and the height resolution of the inferred atmospheric parameters can be significantly increased. The spectral bands of SUSI are selected one at a time by rotating a diffraction grating with respect to a fixed polarimetry unit. The spatial and spectral field of view on the 2k x 2k cameras is 59" and 2.0 - 2.3 nm, respectively. A further innovation is the numerical restoration of the spectrograph scans by means of synchronized 2D context imaging, a technique that has recently produced impressive results at ground-based solar observatories. Title: Sunrise Chromospheric Infrared SpectroPolarimeter (SCIP) for sunrise III: system design and capability Authors: Katsukawa, Y.; del Toro Iniesta, J. C.; Solanki, S. K.; Kubo, M.; Hara, H.; Shimizu, T.; Oba, T.; Kawabata, Y.; Tsuzuki, T.; Uraguchi, F.; Nodomi, Y.; Shinoda, K.; Tamura, T.; Suematsu, Y.; Ishikawa, R.; Kano, R.; Matsumoto, T.; Ichimoto, K.; Nagata, S.; Quintero Noda, C.; Anan, T.; Orozco Suárez, D.; Balaguer Jiménez, M.; López Jiménez, A. C.; Cobos Carrascosa, J. P.; Feller, A.; Riethmueller, T.; Gandorfer, A.; Lagg, A. Bibcode: 2020SPIE11447E..0YK Altcode: The Sunrise balloon-borne solar observatory carries a 1 m aperture optical telescope and provides us a unique platform to conduct continuous seeing-free observations at UV-visible-IR wavelengths from an altitude of higher than 35 km. For the next flight planned for 2022, the post-focus instrumentation is upgraded with new spectro- polarimeters for the near UV (SUSI) and the near-IR (SCIP), whereas the imaging spectro-polarimeter Tunable Magnetograph (TuMag) is capable of observing multiple spectral lines within the visible wavelength. A new spectro-polarimeter called the Sunrise Chromospheric Infrared spectroPolarimeter (SCIP) is under development for observing near-IR wavelength ranges of around 770 nm and 850 nm. These wavelength ranges contain many spectral lines sensitive to solar magnetic fields and SCIP will be able to obtain magnetic and velocity structures in the solar atmosphere with a sufficient height resolution by combining spectro-polarimetric data of these lines. Polarimetric measurements are conducted using a rotating waveplate as a modulator and polarizing beam splitters in front of the cameras. The spatial and spectral resolutions are 0.2" and 2 105, respectively, and a polarimetric sensitivity of 0.03 % (1σ) is achieved within a 10 s integration time. To detect minute polarization signals with good precision, we carefully designed the opto-mechanical system, polarization optics and modulation, and onboard data processing. Title: Coordination within the remote sensing payload on the Solar Orbiter mission Authors: Auchère, F.; Andretta, V.; Antonucci, E.; Bach, N.; Battaglia, M.; Bemporad, A.; Berghmans, D.; Buchlin, E.; Caminade, S.; Carlsson, M.; Carlyle, J.; Cerullo, J. J.; Chamberlin, P. C.; Colaninno, R. C.; Davila, J. M.; De Groof, A.; Etesi, L.; Fahmy, S.; Fineschi, S.; Fludra, A.; Gilbert, H. R.; Giunta, A.; Grundy, T.; Haberreiter, M.; Harra, L. K.; Hassler, D. M.; Hirzberger, J.; Howard, R. A.; Hurford, G.; Kleint, L.; Kolleck, M.; Krucker, S.; Lagg, A.; Landini, F.; Long, D. M.; Lefort, J.; Lodiot, S.; Mampaey, B.; Maloney, S.; Marliani, F.; Martinez-Pillet, V.; McMullin, D. R.; Müller, D.; Nicolini, G.; Orozco Suarez, D.; Pacros, A.; Pancrazzi, M.; Parenti, S.; Peter, H.; Philippon, A.; Plunkett, S.; Rich, N.; Rochus, P.; Rouillard, A.; Romoli, M.; Sanchez, L.; Schühle, U.; Sidher, S.; Solanki, S. K.; Spadaro, D.; St Cyr, O. C.; Straus, T.; Tanco, I.; Teriaca, L.; Thompson, W. T.; del Toro Iniesta, J. C.; Verbeeck, C.; Vourlidas, A.; Watson, C.; Wiegelmann, T.; Williams, D.; Woch, J.; Zhukov, A. N.; Zouganelis, I. Bibcode: 2020A&A...642A...6A Altcode: Context. To meet the scientific objectives of the mission, the Solar Orbiter spacecraft carries a suite of in-situ (IS) and remote sensing (RS) instruments designed for joint operations with inter-instrument communication capabilities. Indeed, previous missions have shown that the Sun (imaged by the RS instruments) and the heliosphere (mainly sampled by the IS instruments) should be considered as an integrated system rather than separate entities. Many of the advances expected from Solar Orbiter rely on this synergistic approach between IS and RS measurements.
Aims: Many aspects of hardware development, integration, testing, and operations are common to two or more RS instruments. In this paper, we describe the coordination effort initiated from the early mission phases by the Remote Sensing Working Group. We review the scientific goals and challenges, and give an overview of the technical solutions devised to successfully operate these instruments together.
Methods: A major constraint for the RS instruments is the limited telemetry (TM) bandwidth of the Solar Orbiter deep-space mission compared to missions in Earth orbit. Hence, many of the strategies developed to maximise the scientific return from these instruments revolve around the optimisation of TM usage, relying for example on onboard autonomy for data processing, compression, and selection for downlink. The planning process itself has been optimised to alleviate the dynamic nature of the targets, and an inter-instrument communication scheme has been implemented which can be used to autonomously alter the observing modes. We also outline the plans for in-flight cross-calibration, which will be essential to the joint data reduction and analysis.
Results: The RS instrument package on Solar Orbiter will carry out comprehensive measurements from the solar interior to the inner heliosphere. Thanks to the close coordination between the instrument teams and the European Space Agency, several challenges specific to the RS suite were identified and addressed in a timely manner. Title: Models and data analysis tools for the Solar Orbiter mission Authors: Rouillard, A. P.; Pinto, R. F.; Vourlidas, A.; De Groof, A.; Thompson, W. T.; Bemporad, A.; Dolei, S.; Indurain, M.; Buchlin, E.; Sasso, C.; Spadaro, D.; Dalmasse, K.; Hirzberger, J.; Zouganelis, I.; Strugarek, A.; Brun, A. S.; Alexandre, M.; Berghmans, D.; Raouafi, N. E.; Wiegelmann, T.; Pagano, P.; Arge, C. N.; Nieves-Chinchilla, T.; Lavarra, M.; Poirier, N.; Amari, T.; Aran, A.; Andretta, V.; Antonucci, E.; Anastasiadis, A.; Auchère, F.; Bellot Rubio, L.; Nicula, B.; Bonnin, X.; Bouchemit, M.; Budnik, E.; Caminade, S.; Cecconi, B.; Carlyle, J.; Cernuda, I.; Davila, J. M.; Etesi, L.; Espinosa Lara, F.; Fedorov, A.; Fineschi, S.; Fludra, A.; Génot, V.; Georgoulis, M. K.; Gilbert, H. R.; Giunta, A.; Gomez-Herrero, R.; Guest, S.; Haberreiter, M.; Hassler, D.; Henney, C. J.; Howard, R. A.; Horbury, T. S.; Janvier, M.; Jones, S. I.; Kozarev, K.; Kraaikamp, E.; Kouloumvakos, A.; Krucker, S.; Lagg, A.; Linker, J.; Lavraud, B.; Louarn, P.; Maksimovic, M.; Maloney, S.; Mann, G.; Masson, A.; Müller, D.; Önel, H.; Osuna, P.; Orozco Suarez, D.; Owen, C. J.; Papaioannou, A.; Pérez-Suárez, D.; Rodriguez-Pacheco, J.; Parenti, S.; Pariat, E.; Peter, H.; Plunkett, S.; Pomoell, J.; Raines, J. M.; Riethmüller, T. L.; Rich, N.; Rodriguez, L.; Romoli, M.; Sanchez, L.; Solanki, S. K.; St Cyr, O. C.; Straus, T.; Susino, R.; Teriaca, L.; del Toro Iniesta, J. C.; Ventura, R.; Verbeeck, C.; Vilmer, N.; Warmuth, A.; Walsh, A. P.; Watson, C.; Williams, D.; Wu, Y.; Zhukov, A. N. Bibcode: 2020A&A...642A...2R Altcode: Context. The Solar Orbiter spacecraft will be equipped with a wide range of remote-sensing (RS) and in situ (IS) instruments to record novel and unprecedented measurements of the solar atmosphere and the inner heliosphere. To take full advantage of these new datasets, tools and techniques must be developed to ease multi-instrument and multi-spacecraft studies. In particular the currently inaccessible low solar corona below two solar radii can only be observed remotely. Furthermore techniques must be used to retrieve coronal plasma properties in time and in three dimensional (3D) space. Solar Orbiter will run complex observation campaigns that provide interesting opportunities to maximise the likelihood of linking IS data to their source region near the Sun. Several RS instruments can be directed to specific targets situated on the solar disk just days before data acquisition. To compare IS and RS, data we must improve our understanding of how heliospheric probes magnetically connect to the solar disk.
Aims: The aim of the present paper is to briefly review how the current modelling of the Sun and its atmosphere can support Solar Orbiter science. We describe the results of a community-led effort by European Space Agency's Modelling and Data Analysis Working Group (MADAWG) to develop different models, tools, and techniques deemed necessary to test different theories for the physical processes that may occur in the solar plasma. The focus here is on the large scales and little is described with regards to kinetic processes. To exploit future IS and RS data fully, many techniques have been adapted to model the evolving 3D solar magneto-plasma from the solar interior to the solar wind. A particular focus in the paper is placed on techniques that can estimate how Solar Orbiter will connect magnetically through the complex coronal magnetic fields to various photospheric and coronal features in support of spacecraft operations and future scientific studies.
Methods: Recent missions such as STEREO, provided great opportunities for RS, IS, and multi-spacecraft studies. We summarise the achievements and highlight the challenges faced during these investigations, many of which motivated the Solar Orbiter mission. We present the new tools and techniques developed by the MADAWG to support the science operations and the analysis of the data from the many instruments on Solar Orbiter.
Results: This article reviews current modelling and tool developments that ease the comparison of model results with RS and IS data made available by current and upcoming missions. It also describes the modelling strategy to support the science operations and subsequent exploitation of Solar Orbiter data in order to maximise the scientific output of the mission.
Conclusions: The on-going community effort presented in this paper has provided new models and tools necessary to support mission operations as well as the science exploitation of the Solar Orbiter data. The tools and techniques will no doubt evolve significantly as we refine our procedure and methodology during the first year of operations of this highly promising mission. Title: The Solar Orbiter Science Activity Plan. Translating solar and heliospheric physics questions into action Authors: Zouganelis, I.; De Groof, A.; Walsh, A. P.; Williams, D. R.; Müller, D.; St Cyr, O. C.; Auchère, F.; Berghmans, D.; Fludra, A.; Horbury, T. S.; Howard, R. A.; Krucker, S.; Maksimovic, M.; Owen, C. J.; Rodríguez-Pacheco, J.; Romoli, M.; Solanki, S. K.; Watson, C.; Sanchez, L.; Lefort, J.; Osuna, P.; Gilbert, H. R.; Nieves-Chinchilla, T.; Abbo, L.; Alexandrova, O.; Anastasiadis, A.; Andretta, V.; Antonucci, E.; Appourchaux, T.; Aran, A.; Arge, C. N.; Aulanier, G.; Baker, D.; Bale, S. D.; Battaglia, M.; Bellot Rubio, L.; Bemporad, A.; Berthomier, M.; Bocchialini, K.; Bonnin, X.; Brun, A. S.; Bruno, R.; Buchlin, E.; Büchner, J.; Bucik, R.; Carcaboso, F.; Carr, R.; Carrasco-Blázquez, I.; Cecconi, B.; Cernuda Cangas, I.; Chen, C. H. K.; Chitta, L. P.; Chust, T.; Dalmasse, K.; D'Amicis, R.; Da Deppo, V.; De Marco, R.; Dolei, S.; Dolla, L.; Dudok de Wit, T.; van Driel-Gesztelyi, L.; Eastwood, J. P.; Espinosa Lara, F.; Etesi, L.; Fedorov, A.; Félix-Redondo, F.; Fineschi, S.; Fleck, B.; Fontaine, D.; Fox, N. J.; Gandorfer, A.; Génot, V.; Georgoulis, M. K.; Gissot, S.; Giunta, A.; Gizon, L.; Gómez-Herrero, R.; Gontikakis, C.; Graham, G.; Green, L.; Grundy, T.; Haberreiter, M.; Harra, L. K.; Hassler, D. M.; Hirzberger, J.; Ho, G. C.; Hurford, G.; Innes, D.; Issautier, K.; James, A. W.; Janitzek, N.; Janvier, M.; Jeffrey, N.; Jenkins, J.; Khotyaintsev, Y.; Klein, K. -L.; Kontar, E. P.; Kontogiannis, I.; Krafft, C.; Krasnoselskikh, V.; Kretzschmar, M.; Labrosse, N.; Lagg, A.; Landini, F.; Lavraud, B.; Leon, I.; Lepri, S. T.; Lewis, G. R.; Liewer, P.; Linker, J.; Livi, S.; Long, D. M.; Louarn, P.; Malandraki, O.; Maloney, S.; Martinez-Pillet, V.; Martinovic, M.; Masson, A.; Matthews, S.; Matteini, L.; Meyer-Vernet, N.; Moraitis, K.; Morton, R. J.; Musset, S.; Nicolaou, G.; Nindos, A.; O'Brien, H.; Orozco Suarez, D.; Owens, M.; Pancrazzi, M.; Papaioannou, A.; Parenti, S.; Pariat, E.; Patsourakos, S.; Perrone, D.; Peter, H.; Pinto, R. F.; Plainaki, C.; Plettemeier, D.; Plunkett, S. P.; Raines, J. M.; Raouafi, N.; Reid, H.; Retino, A.; Rezeau, L.; Rochus, P.; Rodriguez, L.; Rodriguez-Garcia, L.; Roth, M.; Rouillard, A. P.; Sahraoui, F.; Sasso, C.; Schou, J.; Schühle, U.; Sorriso-Valvo, L.; Soucek, J.; Spadaro, D.; Stangalini, M.; Stansby, D.; Steller, M.; Strugarek, A.; Štverák, Š.; Susino, R.; Telloni, D.; Terasa, C.; Teriaca, L.; Toledo-Redondo, S.; del Toro Iniesta, J. C.; Tsiropoula, G.; Tsounis, A.; Tziotziou, K.; Valentini, F.; Vaivads, A.; Vecchio, A.; Velli, M.; Verbeeck, C.; Verdini, A.; Verscharen, D.; Vilmer, N.; Vourlidas, A.; Wicks, R.; Wimmer-Schweingruber, R. F.; Wiegelmann, T.; Young, P. R.; Zhukov, A. N. Bibcode: 2020A&A...642A...3Z Altcode: 2020arXiv200910772Z Solar Orbiter is the first space mission observing the solar plasma both in situ and remotely, from a close distance, in and out of the ecliptic. The ultimate goal is to understand how the Sun produces and controls the heliosphere, filling the Solar System and driving the planetary environments. With six remote-sensing and four in-situ instrument suites, the coordination and planning of the operations are essential to address the following four top-level science questions: (1) What drives the solar wind and where does the coronal magnetic field originate?; (2) How do solar transients drive heliospheric variability?; (3) How do solar eruptions produce energetic particle radiation that fills the heliosphere?; (4) How does the solar dynamo work and drive connections between the Sun and the heliosphere? Maximising the mission's science return requires considering the characteristics of each orbit, including the relative position of the spacecraft to Earth (affecting downlink rates), trajectory events (such as gravitational assist manoeuvres), and the phase of the solar activity cycle. Furthermore, since each orbit's science telemetry will be downloaded over the course of the following orbit, science operations must be planned at mission level, rather than at the level of individual orbits. It is important to explore the way in which those science questions are translated into an actual plan of observations that fits into the mission, thus ensuring that no opportunities are missed. First, the overarching goals are broken down into specific, answerable questions along with the required observations and the so-called Science Activity Plan (SAP) is developed to achieve this. The SAP groups objectives that require similar observations into Solar Orbiter Observing Plans, resulting in a strategic, top-level view of the optimal opportunities for science observations during the mission lifetime. This allows for all four mission goals to be addressed. In this paper, we introduce Solar Orbiter's SAP through a series of examples and the strategy being followed. Title: The Polarimetric and Helioseismic Imager on Solar Orbiter Authors: Solanki, S. K.; del Toro Iniesta, J. C.; Woch, J.; Gandorfer, A.; Hirzberger, J.; Alvarez-Herrero, A.; Appourchaux, T.; Martínez Pillet, V.; Pérez-Grande, I.; Sanchis Kilders, E.; Schmidt, W.; Gómez Cama, J. M.; Michalik, H.; Deutsch, W.; Fernandez-Rico, G.; Grauf, B.; Gizon, L.; Heerlein, K.; Kolleck, M.; Lagg, A.; Meller, R.; Müller, R.; Schühle, U.; Staub, J.; Albert, K.; Alvarez Copano, M.; Beckmann, U.; Bischoff, J.; Busse, D.; Enge, R.; Frahm, S.; Germerott, D.; Guerrero, L.; Löptien, B.; Meierdierks, T.; Oberdorfer, D.; Papagiannaki, I.; Ramanath, S.; Schou, J.; Werner, S.; Yang, D.; Zerr, A.; Bergmann, M.; Bochmann, J.; Heinrichs, J.; Meyer, S.; Monecke, M.; Müller, M. -F.; Sperling, M.; Álvarez García, D.; Aparicio, B.; Balaguer Jiménez, M.; Bellot Rubio, L. R.; Cobos Carracosa, J. P.; Girela, F.; Hernández Expósito, D.; Herranz, M.; Labrousse, P.; López Jiménez, A.; Orozco Suárez, D.; Ramos, J. L.; Barandiarán, J.; Bastide, L.; Campuzano, C.; Cebollero, M.; Dávila, B.; Fernández-Medina, A.; García Parejo, P.; Garranzo-García, D.; Laguna, H.; Martín, J. A.; Navarro, R.; Núñez Peral, A.; Royo, M.; Sánchez, A.; Silva-López, M.; Vera, I.; Villanueva, J.; Fourmond, J. -J.; de Galarreta, C. Ruiz; Bouzit, M.; Hervier, V.; Le Clec'h, J. C.; Szwec, N.; Chaigneau, M.; Buttice, V.; Dominguez-Tagle, C.; Philippon, A.; Boumier, P.; Le Cocguen, R.; Baranjuk, G.; Bell, A.; Berkefeld, Th.; Baumgartner, J.; Heidecke, F.; Maue, T.; Nakai, E.; Scheiffelen, T.; Sigwarth, M.; Soltau, D.; Volkmer, R.; Blanco Rodríguez, J.; Domingo, V.; Ferreres Sabater, A.; Gasent Blesa, J. L.; Rodríguez Martínez, P.; Osorno Caudel, D.; Bosch, J.; Casas, A.; Carmona, M.; Herms, A.; Roma, D.; Alonso, G.; Gómez-Sanjuan, A.; Piqueras, J.; Torralbo, I.; Fiethe, B.; Guan, Y.; Lange, T.; Michel, H.; Bonet, J. A.; Fahmy, S.; Müller, D.; Zouganelis, I. Bibcode: 2020A&A...642A..11S Altcode: 2019arXiv190311061S
Aims: This paper describes the Polarimetric and Helioseismic Imager on the Solar Orbiter mission (SO/PHI), the first magnetograph and helioseismology instrument to observe the Sun from outside the Sun-Earth line. It is the key instrument meant to address the top-level science question: How does the solar dynamo work and drive connections between the Sun and the heliosphere? SO/PHI will also play an important role in answering the other top-level science questions of Solar Orbiter, while hosting the potential of a rich return in further science.
Methods: SO/PHI measures the Zeeman effect and the Doppler shift in the Fe I 617.3 nm spectral line. To this end, the instrument carries out narrow-band imaging spectro-polarimetry using a tunable LiNbO3 Fabry-Perot etalon, while the polarisation modulation is done with liquid crystal variable retarders. The line and the nearby continuum are sampled at six wavelength points and the data are recorded by a 2k × 2k CMOS detector. To save valuable telemetry, the raw data are reduced on board, including being inverted under the assumption of a Milne-Eddington atmosphere, although simpler reduction methods are also available on board. SO/PHI is composed of two telescopes; one, the Full Disc Telescope, covers the full solar disc at all phases of the orbit, while the other, the High Resolution Telescope, can resolve structures as small as 200 km on the Sun at closest perihelion. The high heat load generated through proximity to the Sun is greatly reduced by the multilayer-coated entrance windows to the two telescopes that allow less than 4% of the total sunlight to enter the instrument, most of it in a narrow wavelength band around the chosen spectral line.
Results: SO/PHI was designed and built by a consortium having partners in Germany, Spain, and France. The flight model was delivered to Airbus Defence and Space, Stevenage, and successfully integrated into the Solar Orbiter spacecraft. A number of innovations were introduced compared with earlier space-based spectropolarimeters, thus allowing SO/PHI to fit into the tight mass, volume, power and telemetry budgets provided by the Solar Orbiter spacecraft and to meet the (e.g. thermal) challenges posed by the mission's highly elliptical orbit. Title: PMI: The Photospheric Magnetic Field Imager Authors: Staub, Jan; Fernandez-Rico, German; Gandorfer, Achim; Gizon, Laurent; Hirzberger, Johann; Kraft, Stefan; Lagg, Andreas; Schou, Jesper; Solanki, Sami K.; del Toro Iniesta, Jose Carlos; Wiegelmann, Thomas; Woch, Joachim Bibcode: 2020JSWSC..10...54S Altcode: We describe the design and the capabilities of the Photospheric Magnetic field Imager (PMI), a compact and lightweight vector magnetograph, which is being developed for ESA's Lagrange mission to the Lagrange L5 point. After listing the design requirements and give a scientific justification for them, we describe the technical implementation and the design solution capable of fulfilling these requirements. This is followed by a description of the hardware architecture as well as the operations principle. An outlook on the expected performance concludes the paper. Title: Helicity proxies from linear polarisation of solar active regions Authors: Prabhu, A.; Brandenburg, A.; Käpylä, M. J.; Lagg, A. Bibcode: 2020A&A...641A..46P Altcode: 2020arXiv200110884P Context. The α effect is believed to play a key role in the generation of the solar magnetic field. A fundamental test for its significance in the solar dynamo is to look for magnetic helicity of opposite signs both between the two hemispheres as well as between small and large scales. However, measuring magnetic helicity is compromised by the inability to fully infer the magnetic field vector from observations of solar spectra, caused by what is known as the π ambiguity of spectropolarimetric observations.
Aims: We decompose linear polarisation into parity-even and parity-odd E and B polarisations, which are not affected by the π ambiguity. Furthermore, we study whether the correlations of spatial Fourier spectra of B and parity-even quantities such as E or temperature T are a robust proxy for magnetic helicity of solar magnetic fields.
Methods: We analysed polarisation measurements of active regions observed by the Helioseismic and Magnetic Imager on board the Solar Dynamics observatory. Theory predicts the magnetic helicity of active regions to have, statistically, opposite signs in the two hemispheres. We then computed the parity-odd EB and TB correlations and tested for a systematic preference of their sign based on the hemisphere of the active regions.
Results: We find that: (i) EB and TB correlations are a reliable proxy for magnetic helicity, when computed from linear polarisation measurements away from spectral line cores; and (ii) E polarisation reverses its sign close to the line core. Our analysis reveals that Faraday rotation does not have a significant influence on the computed parity-odd correlations.
Conclusions: The EB decomposition of linear polarisation appears to be a good proxy for magnetic helicity independent of the π ambiguity. This allows us to routinely infer magnetic helicity directly from polarisation measurements. Title: No universal connection between the vertical magnetic field and the umbra-penumbra boundary in sunspots Authors: Löptien, B.; Lagg, A.; van Noort, M.; Solanki, S. K. Bibcode: 2020A&A...639A.106L Altcode: 2020arXiv200602346L Context. It has been reported that the boundary between the umbra and the penumbra of sunspots occurs at a canonical value of the strength of the vertical magnetic field, independently of the size of the spot. This critical field strength is interpreted to be the threshold for the onset of magnetoconvection.
Aims: Here we investigate the reasons why this criterion, also called the Jurčák criterion in the literature, does not always identify the boundary between the umbra and the penumbra.
Methods: We performed a statistical analysis of 23 sunspots observed with Hinode/SOT. We compared the properties of the continuum intensity and the vertical magnetic field between filaments and spines and how they vary between spots of different sizes.
Results: We find that the inner boundary of the penumbra is not related to a universal value of the vertical magnetic field. The properties of spines and filaments vary between spots of different sizes. Both components are darker in larger spots and the spines exhibit a stronger vertical magnetic field. These variations of the properties of filaments and spines with the spot size are also the reason for the reported invariance in the averaged vertical magnetic field at 50% of the mean continuum intensity.
Conclusions: The formation of filaments and the onset of magnetoconvection are not related to a canonical value of the strength of the vertical magnetic field. The seemingly unique magnetic field strength is rather an effect of the filling factor of spines and penumbral filaments. Title: Detection of the Strongest Magnetic Field in a Sunspot Light Bridge Authors: Castellanos Durán, J. S.; Lagg, Andreas; Solanki, Sami K.; van Noort, Michiel Bibcode: 2020ApJ...895..129C Altcode: 2020arXiv200312078C; 2020ApJ...895..129D Traditionally, the strongest magnetic fields on the Sun have been measured in sunspot umbrae. More recently, however, much stronger fields have been measured at the ends of penumbral filaments carrying the Evershed and counter-Evershed flows. Superstrong fields have also been reported within a light bridge separating two umbrae of opposite polarities. We aim to accurately determine the strengths of the strongest fields in a light bridge using an advanced inversion technique and to investigate their detailed structure. We analyze observations from the spectropolarimeter on board the Hinode spacecraft of the active region AR 11967. The thermodynamic and magnetic configurations are obtained by inverting the Stokes profiles using an inversion scheme that allows multiple height nodes. Both the traditional 1D inversion technique and the so-called 2D coupled inversions, which take into account the point-spread function of the Hinode telescope, are used. We find a compact structure with an area of 32.7 arcsec2 within a bipolar light bridge with field strengths exceeding 5 kG, confirming the strong fields in this light bridge reported in the literature. Two regions associated with downflows of ∼5 km s-1 harbor field strengths larger than 6.5 kG, covering a total area of 2.97 arcsec2. The maximum field strength found is 8.2 kG, which is the largest ever observed field in a bipolar light bridge up to now. Title: Connecting the Wilson depression to the magnetic field of sunspots Authors: Löptien, B.; Lagg, A.; van Noort, M.; Solanki, S. K. Bibcode: 2020A&A...635A.202L Altcode: 2020arXiv200207484L Context. In sunspots, the geometric height of continuum optical depth unity is depressed compared to the quiet Sun. This so-called Wilson depression is caused by the Lorentz force of the strong magnetic field inside the spots. However, it is not understood in detail yet how the Wilson depression is related to the strength and geometry of the magnetic field or to other properties of the sunspot.
Aims: We aim to study the dependence of the Wilson depression on the properties of the magnetic field of the sunspots and how exactly the magnetic field contributes to balancing the Wilson depression with respect to the gas pressure of the surroundings of the spots.
Methods: Our study is based on 24 spectropolarimetric scans of 12 individual sunspots performed with Hinode. We derived the Wilson depression for each spot using both a recently developed method that is based on minimizing the divergence of the magnetic field and an approach that was developed earlier, which enforces an equilibrium between the gas pressure and the magnetic pressure inside the spot and the gas pressure in the quiet Sun, thus neglecting the influence of the curvature force. We then performed a statistical analysis by comparing the Wilson depression resulting from the two techniques with each other and by relating them to various parameters of the sunspots, such as their size or the strength of the magnetic field.
Results: We find that the Wilson depression becomes larger for spots with a stronger magnetic field, but not as much as one would expect from the increased magnetic pressure. This suggests that the curvature integral provides an important contribution to the Wilson depression, particularly for spots with a weak magnetic field. Our results indicate that the geometry of the magnetic field in the penumbra is different between spots with different strengths of the average umbral magnetic field. Title: Fast downflows in a chromospheric filament Authors: Sowmya, K.; Lagg, A.; Solanki, S. K.; Castellanos Durán, J. S. Bibcode: 2020IAUS..354..454S Altcode: 2019arXiv191206586S An active region filament in the upper chromosphere is studied using spectropolarimetric data in He i 10830 Å from the GREGOR telescope. A Milne-Eddingon based inversion of the Unno-Rachkovsky equations is used to retrieve the velocity and the magnetic field vector of the region. The plasma velocity reaches supersonic values closer to the feet of the filament barbs and coexist with a slow velocity component. Such supersonic velocities result from the acceleration of the plasma as it drains from the filament spine through the barbs. The line-of-sight magnetic fields have strengths below 200 G in the filament spine and in the filament barbs where fast downflows are located, their strengths range between 100 - 700 G. Title: Superstrong photospheric magnetic fields in sunspot penumbrae Authors: Siu-Tapia, A.; Lagg, A.; van Noort, M.; Rempel, M.; Solanki, S. K. Bibcode: 2019A&A...631A..99S Altcode: 2019arXiv190913619S Context. Recently, there have been some reports of unusually strong photospheric magnetic fields (which can reach values of over 7 kG) inferred from Hinode SOT/SP sunspot observations within penumbral regions. These superstrong penumbral fields are even larger than the strongest umbral fields on record and appear to be associated with supersonic downflows. The finding of such fields has been controversial since they seem to show up only when spatially coupled inversions are performed.
Aims: Here, we investigate and discuss the reliability of those findings by studying in detail observed spectra associated with particularly strong magnetic fields at the inner edge of the penumbra of active region 10930.
Methods: We applied classical diagnostic methods and various inversions with different model atmospheres to the observed Stokes profiles in two selected pixels with superstrong magnetic fields, and compared the results with a magnetohydrodynamic simulation of a sunspot whose penumbra contains localized regions with strong fields (nearly 5 kG at τ = 1) associated with supersonic downflows.
Results: The different inversions provide different results: while the SPINOR 2D inversions consider a height-dependent single-component model and return B > 7 kG and supersonic positive vLOS (corresponding to a counter-Evershed flow), height-dependent two-component inversions suggest the presence of an umbral component (almost at rest) with field strengths ∼4 - 4.2 kG and a penumbral component with vLOS ∼ 16 - 18 km s-1 and field strengths up to ∼5.8 kG. Likewise, height-independent two-component inversions find a solution for an umbral component and a strongly redshifted (vLOS ∼ 15 - 17 km s-1) penumbral component with B ∼ 4 kG. According to a Bayesian information criterion, the inversions providing a better balance between the quality of the fits and the number of free parameters considered by the models are the height-independent two-component inversions, but they lie only slightly above the SPINOR 2D inversions. Since it is expected that the physical parameters all display considerable gradients with height, as supported by magnetohydrodynamic (MHD) sunspot simulations, the SPINOR 2D inversions are the preferred ones.
Conclusions: According to the MHD sunspot simulation analyzed here, the presence of counter-Evershed flows in the photospheric penumbra can lead to the necessary conditions for the observation of ∼5 kG fields at the inner penumbra. Although a definite conclusion about the potential existence of fields in excess of 7 kG cannot be given, their nature could be explained (based on the simulation results) as the consequence of the extreme dynamical effects introduced by highly supersonic counter-Evershed flows (vLOS > 10 km s-1 and up to ∼30 km s-1 according to SPINOR 2D). The latter are much faster and more compressive downflows than those found in the MHD simulations and therefore could lead to field intensification up to considerably stronger fields. Also, a lower gas density would lead to a deeper depression of the τ = 1 surface, making possible the observation of deeper-lying stronger fields. The superstrong magnetic fields are expected to be nearly force-free, meaning that they can attain much larger strengths than expected when considering only balance between magnetic pressure and the local gas pressure. Title: A comparison between solar plage and network properties Authors: Buehler, D.; Lagg, A.; van Noort, M.; Solanki, S. K. Bibcode: 2019A&A...630A..86B Altcode: 2019arXiv190807464B
Aims: We compare the properties of kG magnetic structures in the solar network and in active region plage at high spatial resolution.
Methods: Our analysis used six SP scans of the solar disc centre aboard Hinode SOT and inverted the obtained spectra of the photospheric 6302 Å line pair using the 2D SPINOR code.
Results: Photospheric magnetic field concentrations in network and plage areas are on average 1.5 kG strong with inclinations of 10° -20°, and have < 400 m s-1 internal and 2-3 km s-1 external downflows. At the disc centre, the continuum intensity of magnetic field concentrations in the network are on average 10% brighter than the mean quiet Sun, whilst their plage counterparts are 3% darker. A more detailed analysis revealed that all sizes of individual kG patches in the network have 150 G higher field strengths on average, 5% higher continuum contrasts, and 800 m s-1 faster surrounding downflows than similarly sized patches in the plage. The speed of the surrounding downflows also correlates with the patch area, and patches containing pores can produce supersonic flows exceeding 11 km s-1 in individual pixels. Furthermore, the magnetic canopies of kG patches are on average 9° more horizontal in the plage compared to the network.
Conclusions: Most of the differences between the network and plage are due to their different patch size distributions, but the intrinsic differences between similarly sized patches likely results from the modification of the convection photospheric convection with increasing amounts of magnetic flux. Title: Performance Analysis of the SO/PHI Software Framework for On-board Data Reduction Authors: Albert, K.; Hirzberger, J.; Busse, D.; Rodríguez, J. Blanco; Castellanos Duran, J. S.; Cobos Carrascosa, J. P.; Fiethe, B.; Gandorfer, A.; Guan, Y.; Kolleck, M.; Lagg, A.; Lange, T.; Michalik, H.; Solanki, S. K.; del Toro Iniesta, J. C. Bibcode: 2019ASPC..523..151A Altcode: 2019arXiv190508690A The Polarimetric and Helioseismic Imager (PHI) is the first deep-space solar spectropolarimeter, on-board the Solar Orbiter (SO) space mission. It faces: stringent requirements on science data accuracy, a dynamic environment, and severe limitations on telemetry volume. SO/PHI overcomes these restrictions through on-board instrument calibration and science data reduction, using dedicated firmware in FPGAs. This contribution analyses the accuracy of a data processing pipeline by comparing the results obtained with SO/PHI hardware to a reference from a ground computer. The results show that for the analyzed pipeline the error introduced by the firmware implementation is well below the requirements of SO/PHI. Title: Using the infrared iron lines to probe solar subsurface convection Authors: Milić, I.; Smitha, H. N.; Lagg, A. Bibcode: 2019A&A...630A.133M Altcode: 2019arXiv190407306M Context. Studying the properties of solar convection using high-resolution spectropolarimetry began in the early 1990s with the focus on observations in the visible wavelength regions. Its extension to the infrared (IR) remains largely unexplored.
Aims: The IR iron lines around 15 600 Å, most commonly known for their high magnetic sensitivity, also have a non-zero response to line-of-sight (LOS) velocity below log(τ) = 0.0. In this paper we explore the possibility of using these lines to measure subsurface convective velocities.
Methods: By assuming a snapshot of a three-dimensional magnetohydrodynamic simulation to represent the quiet Sun, we investigate how well the iron IR lines can reproduce the LOS velocity in the cube and to what depth. We use the recently developed spectropolarimetric inversion code SNAPI and discuss the optimal node placements for the retrieval of reliable results from these spectral lines.
Results: We find that the IR iron lines can measure the convective velocities down to log(τ) = 0.5, below the photosphere, not only at the original resolution of the cube, but also when degraded with a reasonable spectral and spatial PSF and stray light. Instead, the commonly used Fe I 6300 Å line pair performs significantly worse.
Conclusions: Our investigation reveals that the IR iron lines can probe the subsurface convection in the solar photosphere. This paper is a first step towards exploiting this diagnostic potential. Title: Moving Magnetic Features around a Pore Authors: Kaithakkal, A.; Riethmueller, T.; Solanki, S. K.; Lagg, A. Bibcode: 2019ASPC..526..307K Altcode: Moving magnetic features (MMFs) are small-scale magnetic elements observed to move radially outward from sunspots. Some studies have reported the presence of MMFs around pores as well. We analyzed data from SunriseII/IMaX observations obtained on 2013 June 12 between 23:39:10 and 23:55:37 UT. IMaX scanned the Fe I 5250.225 Å spectral line at eight wavelength positions and recorded the full Stokes vector at each of these positions. The field of view covered a large pore (μ = 0.93) with pixel scale of 0″.055. MMFs of opposite (positive) and same (negative) polarity as the pore were observed to stream from the pore boundary. We carried out a statistical analysis of the physical properties of MMFs and the main results are: 1) the number of opposite polarity MMFs within 1.5 Mm from the pore border, when they were first identified, is twice that of the same polarity MMFs. 2) Only 11% of the chosen MMFs appear to be monopolar and they all have the same polarity as the pore. 3) Majority of MMFs of both polarities move away from the pore border with an average speed of 1.5 km/s. However, they do not always follow a smooth radial track and some of them even move in tangential direction to the pore. 4) MMFs of opposite polarity show a preferential up-flow whereas those of the same polarity do not show any preference. 5) MMFs of both polarities are characterized by inclined fields.

This work, presented in an oral contribution at this Workshop, has been published on The Astrophysical Journal Supplement Series (Kaithakkal et al. 2017). Title: Photospheric Magnetic Fields of the Trailing Sunspots in Active Region NOAA 12396 Authors: Verma, M.; Balthasar, H.; Denker, C.; Böhm, F.; Fischer, C. E.; Kuckein, C.; González Manrique, S. J.; Sobotka, M.; Bello González, N.; Diercke, A.; Berkefeld, T.; Collados, M.; Feller, A.; Hofmann, A.; Lagg, A.; Nicklas, H.; Orozco Suárez, D.; Pastor Yabar, A.; Rezaei, R.; Schlichenmaier, R.; Schmidt, D.; Schmidt, W.; Sigwarth, M.; Solanki, S. K.; Soltau, D.; Staude, J.; Strassmeier, K.; Volkmer, R.; von der Lühe, O.; Waldmann, T. Bibcode: 2019ASPC..526..291V Altcode: 2018arXiv180507752V The solar magnetic field is responsible for all aspects of solar activity. Sunspots are the main manifestation of the ensuing solar activity. Combining high-resolution and synoptic observations has the ambition to provide a comprehensive description of the sunspot growth and decay processes. Active region NOAA 12396 emerged on 2015 August 3 and was observed three days later with the 1.5-meter GREGOR solar telescope on 2015 August 6. High-resolution spectropolarimetric data from the GREGOR Infrared Spectrograph (GRIS) are obtained in the photospheric lines Si I λ1082.7 nm and Ca I λ1083.9 nm, together with the chromospheric He I λ1083.0 nm triplet. These near-infrared spectropolarimetric observations were complemented by synoptic line-of-sight magnetograms and continuum images of the Helioseismic and Magnetic Imager (HMI) and EUV images of the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). Title: Measuring the Wilson depression of sunspots using the divergence-free condition of the magnetic field vector Authors: Löptien, B.; Lagg, A.; van Noort, M.; Solanki, S. K. Bibcode: 2018A&A...619A..42L Altcode: 2018arXiv180806867L Context. The Wilson depression is the difference in geometric height of unit continuum optical depth between the sunspot umbra and the quiet Sun. Measuring the Wilson depression is important for understanding the geometry of sunspots. Current methods suffer from systematic effects or need to make assumptions on the geometry of the magnetic field. This leads to large systematic uncertainties of the derived Wilson depressions.
Aims: We aim to develop a robust method for deriving the Wilson depression that only requires the information about the magnetic field that is accessible from spectropolarimetry, and that does not rely on assumptions on the geometry of sunspots or on their magnetic field.
Methods: Our method is based on minimizing the divergence of the magnetic field vector derived from spectropolarimetric observations. We have focused on large spatial scales only in order to reduce the number of free parameters.
Results: We tested the performance of our method using synthetic Hinode data derived from two sunspot simulations. We find that the maximum and the umbral averaged Wilson depression for both spots determined with our method typically lies within 100 km of the true value obtained from the simulations. In addition, we applied the method to Hinode observations of a sunspot. The derived Wilson depression (∼600 km) is consistent with results typically obtained from the Wilson effect. We also find that the Wilson depression obtained from using horizontal force balance gives 110-180 km smaller Wilson depressions than both, what we find and what we deduce directly from the simulations. This suggests that the magnetic pressure and the magnetic curvature force contribute to the Wilson depression by a similar amount. Title: SOPHISM: Software Instrument Simulator Authors: Blanco Rodríguez, J.; del Toro Iniesta, J. C.; Orozco Suárez, D.; Martínez Pillet, V.; Bonet, J. A.; Feller, A.; Hirzberger, J.; Lagg, A.; Piqueras, J.; Gasent Blesa, J. L. Bibcode: 2018ascl.soft10017B Altcode: SOPHISM models astronomical instrumentation from the entrance of the telescope to data acquisition at the detector, along with software blocks dealing with, for example, demodulation, inversion, and compression. The code performs most analyses done with light in astronomy, such as differential photometry, spectroscopy, and polarimetry. The simulator offers flexibility and implementation of new effects and subsystems, making it user-adaptable for a wide variety of instruments. SOPHISM can be used for all stages of instrument definition, design, operation, and lifetime tracking evaluation. Title: Temporal evolution of arch filaments as seen in He I 10 830 Å Authors: González Manrique, S. J.; Kuckein, C.; Collados, M.; Denker, C.; Solanki, S. K.; Gömöry, P.; Verma, M.; Balthasar, H.; Lagg, A.; Diercke, A. Bibcode: 2018A&A...617A..55G Altcode: 2018arXiv180700728G
Aims: We study the evolution of an arch filament system (AFS) and of its individual arch filaments to learn about the processes occurring in them.
Methods: We observed the AFS at the GREGOR solar telescope on Tenerife at high cadence with the very fast spectroscopic mode of the GREGOR Infrared Spectrograph (GRIS) in the He I 10 830 Å spectral range. The He I triplet profiles were fitted with analytic functions to infer line-of-sight (LOS) velocities to follow plasma motions within the AFS.
Results: We tracked the temporal evolution of an individual arch filament over its entire lifetime, as seen in the He I 10 830 Å triplet. The arch filament expanded in height and extended in length from 13″ to 21″. The lifetime of this arch filament is about 30 min. About 11 min after the arch filament is seen in He I, the loop top starts to rise with an average Doppler velocity of 6 km s-1. Only two minutes later, plasma drains down with supersonic velocities towards the footpoints reaching a peak velocity of up to 40 km s-1 in the chromosphere. The temporal evolution of He I 10 830 Å profiles near the leading pore showed almost ubiquitous dual red components of the He I triplet, indicating strong downflows, along with material nearly at rest within the same resolution element during the whole observing time.
Conclusions: We followed the arch filament as it carried plasma during its rise from the photosphere to the corona. The material then drained toward the photosphere, reaching supersonic velocities, along the legs of the arch filament. Our observational results support theoretical AFS models and aids in improving future models.

The movie associated to Fig. 3 is available at https://www.aanda.org/ Title: SOPHISM: An End-to-end Software Instrument Simulator Authors: Blanco Rodríguez, J.; del Toro Iniesta, J. C.; Orozco Suárez, D.; Martínez Pillet, V.; Bonet, J. A.; Feller, A.; Hirzberger, J.; Lagg, A.; Piqueras, J.; Gasent Blesa, J. L. Bibcode: 2018ApJS..237...35B Altcode: We present a software simulator for the modeling of astronomical instrumentation, which includes platform effects and software processing. It is an end-to-end simulator, from the entrance of the telescope to the data acquisition at the detector, along with software blocks dealing, e.g., with demodulation, inversion, and compression. Developed following the Solar Orbiter/Polarimetric and Helioseismic Imager (SO/PHI) instrument, it comprises elements such as a filtergraph, polarimetric modulator, detector, vibrations, and accumulations. Through these, the simulator performs most of the analyses that can be done with light in astronomy, such as differential photometry, spectroscopy, and polarimetry. The simulator is coded with high flexibility and ease of implementation of new effects and subsystems. Thus, it allows for the user to adapt it to a wide variety of instruments, even not exclusively solar ones, as illustrated with an example of application to a night-time observation. The simulator can provide support in the phase of instrument design and help assess tolerances and test solutions to underperformances arising during the instrument operations. All this makes SOPHISM a very valuable tool for all the stages of astronomical instrument definition, design, operation, and lifetime tracking evaluation. Title: Bihelical Spectrum of Solar Magnetic Helicity and Its Evolution Authors: Singh, Nishant K.; Käpylä, Maarit J.; Brandenburg, Axel; Käpylä, Petri J.; Lagg, Andreas; Virtanen, Ilpo Bibcode: 2018ApJ...863..182S Altcode: 2018arXiv180404994S Using a recently developed two-scale formalism to determine the magnetic helicity spectrum, we analyze synoptic vector magnetograms built with data from the Vector Spectromagnetograph instrument on the Synoptic Optical Long-term Investigations of the Sun telescope during 2010 January-2016 July. In contrast to an earlier study using only three Carrington rotations (CRs), our analysis includes 74 synoptic CR maps. We recover here bihelical spectra at different phases of solar cycle 24, where the net magnetic helicity in the majority of the data is consistent with a large-scale dynamo with helical turbulence operating in the Sun. More than 20% of the analyzed maps, however, show violations of the expected sign rule. Title: Getting Ready for the Third Science Flight of SUNRISE Authors: Barthol, Peter; Katsukawa, Yukio; Lagg, Andreas; Solanki, Sami K.; Kubo, Masahito; Riethmueller, Tino; Martínez Pillet, Valentin; Gandorfer, Achim; Feller, Alex; Berkefeld, . Thomas; Orozco Suárez, David; Del Toro Iniesta, Jose Carlos; Bernasconi, Pietro; Álvarez-Herrero, Alberto; Quintero Noda, Carlos Bibcode: 2018cosp...42E.215B Altcode: SUNRISE is a balloon-borne, stratospheric solar observatory dedicated to the investigation of the structure and dynamics of the Sun's magnetic field and its interaction with convective plasma flows and waves. The previous science flights of SUNRISE in 2009 and 2013 have led to many new scientific results, so far described in around 90 refereed publications. This success has shown the huge potential of the SUNRISE concept and the recovery of the largely intact payload offers the opportunity for a third flight.The scientific instrumentation of SUNRISE 3 will have extended capabilities in particular to measure magnetic fields, plasma velocities and temperatures with increased sensitivity and over a larger height range in the solar atmosphere, from the convectively dominated photosphere up to the still poorly understood chromosphere. The latter is the key interaction region between magnetic field, waves and radiation and plays a central role in transporting energy to the outer layers of the solar atmosphere including the corona.SUNRISE 3 will carry 2 new grating-based spectro-polarimeters with slit-scanning and context imaging with slitjaw cameras. The SUNRISE UV Spectro-polarimeter and Imager (SUSI) will explore the rich near-UV range between 300 nm and 430 nm which is poorly accessible from the ground. The SUNRISE Chromospheric Infrared spectro-Polarimeter (SCIP) will sample 2 spectral windows in the near-infrared, containing many spectral lines highly sensitive to magnetic fields at different formation heights. In addition to the two new instruments the Imaging Magnetograph eXperiment (IMaX), an etalon-based tunable filtergraph and spectro-polarimeter flown on both previous missions, will be upgraded to IMaX+, enhancing its cadence and giving access to 2 spectral lines in the visible spectral range. All three instruments will allow investigating both the photosphere and the chromosphere and will ideally complement each other in terms of sensitivity, height coverage and resolution.A new gondola with a sophisticated attitude control system including roll damping will provide improved pointing/tracking performance. Upgraded image stabilization with higher bandwidth will further reduce residual jitter, maximizing the quality of the science data.SUNRISE 3 is a joint project of the German Max-Planck-Institut für Sonnensystemforschung together with the Spanish SUNRISE consortium, the Johns Hopkins University Applied Physics Laboratory, USA, the German Kiepenheuer Institut für Sonnenphysik, the National Astronomical Observatory of Japan and the Japan Aerospace eXploraion Agency (JAXA). Title: Measurements of Photospheric and Chromospheric Magnetic Fields Authors: Lagg, Andreas; Lites, Bruce; Harvey, Jack; Gosain, Sanjay; Centeno, Rebecca Bibcode: 2018smf..book...37L Altcode: No abstract at ADS Title: Evershed and Counter-Evershed Flows in Sunspot MHD Simulations Authors: Siu-Tapia, A. L.; Rempel, M.; Lagg, A.; Solanki, S. K. Bibcode: 2018ApJ...852...66S Altcode: 2017arXiv171201202S There have been a few reports in the literature of counter-Evershed flows observed in well-developed sunspot penumbrae, i.e., flows directed toward the umbra along penumbral filaments. Here, we investigate the driving forces of such counter-Evershed flows in a radiative magnetohydrodynamic simulation of a sunspot, and compare them to the forces acting on the normal Evershed flow. The simulation covers a timespan of 100 solar hours and generates an Evershed outflow exceeding 8 km s-1 in the penumbra along radially aligned filaments where the magnetic field is almost horizontal. Additionally, the simulation produces a fast counter-Evershed flow (i.e., an inflow near τ =1) in some regions within the penumbra, reaching peak flow speeds of ∼12 km s-1. The counter-Evershed flows are transient and typically last a few hours before they turn into outflows again. By using the kinetic energy equation and evaluating its various terms in the simulation box, we found that the Evershed flow occurs due to overturning convection in a strongly inclined magnetic field, while the counter-Evershed flows can be well-described as siphon flows. Title: Normal and counter Evershed flows in the photospheric penumbra of a sunspot. SPINOR 2D inversions of Hinode-SOT/SP observations Authors: Siu-Tapia, A.; Lagg, A.; Solanki, S. K.; van Noort, M.; Jurčák, J. Bibcode: 2017A&A...607A..36S Altcode: 2017arXiv170907386S Context. The Evershed effect, a nearly horizontal outflow of material seen in the penumbrae of sunspots in the photospheric layers, is a common characteristic of well-developed penumbrae, but is still not well understood. Even less is known about photospheric horizontal inflows in the penumbra, also known as counter Evershed flows.
Aims: Here we present a rare feature observed in the penumbra of the main sunspot of AR NOAA 10930. This spot displays the normal Evershed outflow in most of the penumbra, but harbors a fast photospheric inflow of material over a large sector of the disk-center penumbra. We investigate the driving forces of both, the normal and the counter Evershed flows.
Methods: We invert the spectropolarimetric data from Hinode SOT/SP using the spatially coupled version of the SPINOR inversion code, which allows us to derive height-dependent maps of the relevant physical parameters in the sunspot. These maps show considerable fine structure. Similarities and differences between the normal Evershed outflow and the counter Evershed flow are investigated.
Results: In both the normal and the counter Evershed flows, the material flows from regions with field strengths of the order of 1.5-2 kG to regions with stronger fields. The sources and sinks of both penumbral flows display opposite field polarities, with the sinks (tails of filaments) harboring local enhancements in temperature, which are nonetheless colder than their sources (heads of filaments).
Conclusions: The anti-correlation of the gradients in the temperature and magnetic pressure between the endpoints of the filaments from the two distinct penumbral regions is compatible with both the convective driver and the siphon flow scenarios. A geometrical scale of the parameters is necessary to determine which is the dominant force driving the flows. Title: Flows along arch filaments observed in the GRIS `very fast spectroscopic mode' Authors: González Manrique, S. J.; Denker, C.; Kuckein, C.; Pastor Yabar, A.; Collados, M.; Verma, M.; Balthasar, H.; Diercke, A.; Fischer, C. E.; Gömöry, P.; Bello González, N.; Schlichenmaier, R.; Cubas Armas, M.; Berkefeld, T.; Feller, A.; Hoch, S.; Hofmann, A.; Lagg, A.; Nicklas, H.; Orozco Suárez, D.; Schmidt, D.; Schmidt, W.; Sigwarth, M.; Sobotka, M.; Solanki, S. K.; Soltau, D.; Staude, J.; Strassmeier, K. G.; Volkmer, R.; von der Lühe, O.; Waldmann, T. Bibcode: 2017IAUS..327...28G Altcode: 2017arXiv170102206G A new generation of solar instruments provides improved spectral, spatial, and temporal resolution, thus facilitating a better understanding of dynamic processes on the Sun. High-resolution observations often reveal multiple-component spectral line profiles, e.g., in the near-infrared He i 10830 Å triplet, which provides information about the chromospheric velocity and magnetic fine structure. We observed an emerging flux region, including two small pores and an arch filament system, on 2015 April 17 with the `very fast spectroscopic mode' of the GREGOR Infrared Spectrograph (GRIS) situated at the 1.5-meter GREGOR solar telescope at Observatorio del Teide, Tenerife, Spain. We discuss this method of obtaining fast (one per minute) spectral scans of the solar surface and its potential to follow dynamic processes on the Sun. We demonstrate the performance of the `very fast spectroscopic mode' by tracking chromospheric high-velocity features in the arch filament system. Title: Measurements of Photospheric and Chromospheric Magnetic Fields Authors: Lagg, Andreas; Lites, Bruce; Harvey, Jack; Gosain, Sanjay; Centeno, Rebecca Bibcode: 2017SSRv..210...37L Altcode: 2015arXiv151006865L; 2015SSRv..tmp..115L The Sun is replete with magnetic fields, with sunspots, pores and plage regions being their most prominent representatives on the solar surface. But even far away from these active regions, magnetic fields are ubiquitous. To a large extent, their importance for the thermodynamics in the solar photosphere is determined by the total magnetic flux. Whereas in low-flux quiet Sun regions, magnetic structures are shuffled around by the motion of granules, the high-flux areas like sunspots or pores effectively suppress convection, leading to a temperature decrease of up to 3000 K. The importance of magnetic fields to the conditions in higher atmospheric layers, the chromosphere and corona, is indisputable. Magnetic fields in both active and quiet regions are the main coupling agent between the outer layers of the solar atmosphere, and are therefore not only involved in the structuring of these layers, but also for the transport of energy from the solar surface through the corona to the interplanetary space.

Consequently, inference of magnetic fields in the photosphere, and especially in the chromosphere, is crucial to deepen our understanding not only for solar phenomena such as chromospheric and coronal heating, flares or coronal mass ejections, but also for fundamental physical topics like dynamo theory or atomic physics. In this review, we present an overview of significant advances during the last decades in measurement techniques, analysis methods, and the availability of observatories, together with some selected results. We discuss the problems of determining magnetic fields at smallest spatial scales, connected with increasing demands on polarimetric sensitivity and temporal resolution, and highlight some promising future developments for their solution. Title: Three-dimensional magnetic structure of a sunspot: Comparison of the photosphere and upper chromosphere Authors: Joshi, Jayant; Lagg, Andreas; Hirzberger, Johann; Solanki, Sami K. Bibcode: 2017A&A...604A..98J Altcode: 2017arXiv170508404J
Aims: We investigate the magnetic field of a sunspot in the upper chromosphere and compare it to the photospheric properties of the field.
Methods: We observed the main leading sunspot of the active region NOAA 11124 during two days with the Tenerife Infrared Polarimeter-2 (TIP-2) mounted at the German Vacuum Tower Telescope (VTT). Through inversion of Stokes spectra of the He I triplet at 10 830 Å, we obtained the magnetic field vector of the upper chromosphere. For comparison with the photosphere, we applied height-dependent inversions of the Si I 10 827.1 Å and Ca I 10 833.4 Å lines.
Results: We found that the umbral magnetic field strength in the upper chromosphere is lower by a factor of 1.30-1.65 compared to the photosphere. The magnetic field strength of the umbra decreases from the photosphere toward the upper chromosphere by an average rate of 0.5-0.9 G km-1. The difference in the magnetic field strength between both atmospheric layers steadily decreases from the sunspot center to the outer boundary of the sunspot; the field, in particular its horizontal component, is stronger in the chromopshere outside the spot and this is suggestive of a magnetic canopy. The sunspot displays a twist that on average is similar in the two layers. However, the differential twist between the photosphere and chromosphere increases rapidly toward the outer penumbral boundary. The magnetic field vector is more horizontal with respect to the solar surface by roughly 5-20° in the photosphere compared to the upper chromosphere. Above a lightbridge, the chromospheric magnetic field is equally strong as that in the umbra, whereas the field of the lightbridge is weaker than its surroundings in the photosphere by roughly 1 kG. This suggests a cusp-like magnetic field structure above the lightbridge. Title: Extended Subadiabatic Layer in Simulations of Overshooting Convection Authors: Käpylä, Petri J.; Rheinhardt, Matthias; Brandenburg, Axel; Arlt, Rainer; Käpylä, Maarit J.; Lagg, Andreas; Olspert, Nigul; Warnecke, Jörn Bibcode: 2017ApJ...845L..23K Altcode: 2017arXiv170306845K We present numerical simulations of hydrodynamic overshooting convection in local Cartesian domains. We find that a substantial fraction of the lower part of the convection zone (CZ) is stably stratified according to the Schwarzschild criterion while the enthalpy flux is outward directed. This occurs when the heat conduction profile at the bottom of the CZ is smoothly varying, based either on a Kramers-like opacity prescription as a function of temperature and density or a static profile of a similar shape. We show that the subadiabatic layer arises due to nonlocal energy transport by buoyantly driven downflows in the upper parts of the CZ. Analysis of the force balance of the upflows and downflows confirms that convection is driven by cooling at the surface. We find that the commonly used prescription for the convective enthalpy flux being proportional to the negative entropy gradient does not hold in the stably stratified layers where the flux is positive. We demonstrate the existence of a non-gradient contribution to the enthalpy flux, which is estimated to be important throughout the convective layer. A quantitative analysis of downflows indicates a transition from a tree-like structure where smaller downdrafts merge into larger ones in the upper parts to a structure in the deeper parts where a height-independent number of strong downdrafts persist. This change of flow topology occurs when a substantial subadiabatic layer is present in the lower part of the CZ. Title: Erratum: Morphological Properties of Slender CaII H Fibrils Observed by sunrise II (ApJS 229, 1, 6) Authors: Gafeira, R.; Lagg, A.; Solanki, S. K.; Jafarzadeh, S.; van Noort, M.; Barthol, P.; Blanco Rodríguez, J.; del Toro Iniesta, J. C.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Knölker, M.; Orozco Suárez, D.; Riethmüller, T. L.; Schmidt, W. Bibcode: 2017ApJS..230...11G Altcode: No abstract at ADS Title: The Second Flight of the Sunrise Balloon-borne Solar Observatory: Overview of Instrument Updates, the Flight, the Data, and First Results Authors: Solanki, S. K.; Riethmüller, T. L.; Barthol, P.; Danilovic, S.; Deutsch, W.; Doerr, H. -P.; Feller, A.; Gandorfer, A.; Germerott, D.; Gizon, L.; Grauf, B.; Heerlein, K.; Hirzberger, J.; Kolleck, M.; Lagg, A.; Meller, R.; Tomasch, G.; van Noort, M.; Blanco Rodríguez, J.; Gasent Blesa, J. L.; Balaguer Jiménez, M.; Del Toro Iniesta, J. C.; López Jiménez, A. C.; Orozco Suarez, D.; Berkefeld, T.; Halbgewachs, C.; Schmidt, W.; Álvarez-Herrero, A.; Sabau-Graziati, L.; Pérez Grande, I.; Martínez Pillet, V.; Card, G.; Centeno, R.; Knölker, M.; Lecinski, A. Bibcode: 2017ApJS..229....2S Altcode: 2017arXiv170101555S The Sunrise balloon-borne solar observatory, consisting of a 1 m aperture telescope that provides a stabilized image to a UV filter imager and an imaging vector polarimeter, carried out its second science flight in 2013 June. It provided observations of parts of active regions at high spatial resolution, including the first high-resolution images in the Mg II k line. The obtained data are of very high quality, with the best UV images reaching the diffraction limit of the telescope at 3000 Å after Multi-Frame Blind Deconvolution reconstruction accounting for phase-diversity information. Here a brief update is given of the instruments and the data reduction techniques, which includes an inversion of the polarimetric data. Mainly those aspects that evolved compared with the first flight are described. A tabular overview of the observations is given. In addition, an example time series of a part of the emerging active region NOAA AR 11768 observed relatively close to disk center is described and discussed in some detail. The observations cover the pores in the trailing polarity of the active region, as well as the polarity inversion line where flux emergence was ongoing and a small flare-like brightening occurred in the course of the time series. The pores are found to contain magnetic field strengths ranging up to 2500 G, and while large pores are clearly darker and cooler than the quiet Sun in all layers of the photosphere, the temperature and brightness of small pores approach or even exceed those of the quiet Sun in the upper photosphere. Title: Vertical magnetic field gradient in the photospheric layers of sunspots Authors: Joshi, Jayant; Lagg, Andreas; Hirzberger, Johann; Solanki, Sami K.; Tiwari, Sanjiv K. Bibcode: 2017A&A...599A..35J Altcode: 2016arXiv161000500J
Aims: We investigate the vertical gradient of the magnetic field of sunspots in the photospheric layer.
Methods: Independent observations were obtained with the Solar Optical Telescope/Spectropolarimeter (SOT/SP) on board the Hinode spacecraft and with the Tenrife Infrared Polarimeter-2 (TIP-2) mounted at the German Vacuum Tower Telescope (VTT). We apply state-of-the-art inversion techniques to both data sets to retrieve the magnetic field and the corresponding vertical gradient along with other atmospheric parameters in the solar photosphere.
Results: In the sunspot penumbrae we detected patches of negative vertical gradients of the magnetic field strength, I.e., the magnetic field strength decreases with optical depth in the photosphere. The negative gradient patches are located in the inner and partly in the middle penumbrae in both data sets. From the SOT/SP observations we found that the negative gradient patches are restricted mainly to the deep photospheric layers and are concentrated near the edges of the penumbral filaments. Magnetohydrodynamic (MHD) simulations also show negative gradients in the inner penumbrae, also at the locations of filaments. In the observations and the simulation negative gradients of the magnetic field vs. optical depth dominate at some radial distances in the penumbra. The negative gradient with respect to optical depth in the inner penumbrae persists even after averaging in the azimuthal direction in the observations and, to a lesser extent, in the MHD simulations. If the gradients in the MHD simulations are determined with respect to geometrical height, then the azimuthal averages are always positive within the sunspot (above log τ = 0), corresponding to magnetic field increasing with depth, as generally expected.
Conclusions: We interpret the observed localized presence of negative vertical gradient of the magnetic field strength in the observations as a consequence of stronger field from spines expanding with height and closing above the weaker field inter-spines. The presence of the negative gradients with respect to optical depth after azimuthal averaging can be explained by two different mechanisms: the high corrugation of equal optical depth surfaces and the cancellation of polarized signal due to the presence of unresolved opposite polarity patches in the deeper layers of the penumbra. Title: Morphological Properties of Slender Ca II H Fibrils Observed by SUNRISE II Authors: Gafeira, R.; Lagg, A.; Solanki, S. K.; Jafarzadeh, S.; van Noort, M.; Barthol, P.; Blanco Rodríguez, J.; del Toro Iniesta, J. C.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Knölker, M.; Orozco Suárez, D.; Riethmüller, T. L.; Schmidt, W. Bibcode: 2017ApJS..229....6G Altcode: 2016arXiv161200319G We use seeing-free high spatial resolution Ca II H data obtained by the SUNRISE observatory to determine properties of slender fibrils in the lower solar chromosphere. In this work we use intensity images taken with the SuFI instrument in the Ca II H line during the second scientific flight of the SUNRISE observatory to identify and track elongated bright structures. After identification, we analyze theses structures to extract their morphological properties. We identify 598 slender Ca II H fibrils (SCFs) with an average width of around 180 km, length between 500 and 4000 km, average lifetime of ≈400 s, and average curvature of 0.002 arcsec-1. The maximum lifetime of the SCFs within our time series of 57 minutes is ≈2000 s. We discuss similarities and differences of the SCFs with other small-scale, chromospheric structures such as spicules of type I and II, or Ca II K fibrils. Title: Oscillations on Width and Intensity of Slender Ca II H Fibrils from Sunrise/SuFI Authors: Gafeira, R.; Jafarzadeh, S.; Solanki, S. K.; Lagg, A.; van Noort, M.; Barthol, P.; Blanco Rodríguez, J.; del Toro Iniesta, J. C.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Knölker, M.; Orozco Suárez, D.; Riethmüller, T. L.; Schmidt, W. Bibcode: 2017ApJS..229....7G Altcode: 2017arXiv170102801G We report the detection of oscillations in slender Ca II H fibrils (SCFs) from high-resolution observations acquired with the Sunrise balloon-borne solar observatory. The SCFs show obvious oscillations in their intensity, but also their width. The oscillatory behaviors are investigated at several positions along the axes of the SCFs. A large majority of fibrils show signs of oscillations in intensity. Their periods and phase speeds are analyzed using a wavelet analysis. The width and intensity perturbations have overlapping distributions of the wave period. The obtained distributions have median values of the period of 32 ± 17 s and 36 ± 25 s, respectively. We find that the fluctuations of both parameters propagate in the SCFs with speeds of {11}-11+49 km s-1 and {15}-15+34 km s-1, respectively. Furthermore, the width and intensity oscillations have a strong tendency to be either in anti-phase or, to a smaller extent, in phase. This suggests that the oscillations of both parameters are caused by the same wave mode and that the waves are likely propagating. Taking all the evidence together, the most likely wave mode to explain all measurements and criteria is the fast sausage mode. Title: Moving Magnetic Features around a Pore Authors: Kaithakkal, A. J.; Riethmüller, T. L.; Solanki, S. K.; Lagg, A.; Barthol, P.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; vanNoort, M.; Blanco Rodríguez, J.; Del Toro Iniesta, J. C.; Orozco Suárez, D.; Schmidt, W.; Martínez Pillet, V.; Knölker, M. Bibcode: 2017ApJS..229...13K Altcode: 2016arXiv160905664K Spectropolarimetric observations from Sunrise/IMaX, obtained in 2013 June, are used for a statistical analysis to determine the physical properties of moving magnetic features (MMFs) observed near a pore. MMFs of the same and opposite polarity, with respect to the pore, are found to stream from its border at an average speed of 1.3 km s-1 and 1.2 km s-1, respectively, with mainly same-polarity MMFs found further away from the pore. MMFs of both polarities are found to harbor rather weak, inclined magnetic fields. Opposite-polarity MMFs are blueshifted, whereas same-polarity MMFs do not show any preference for up- or downflows. Most of the MMFs are found to be of sub-arcsecond size and carry a mean flux of ∼1.2 × 1017 Mx. Title: Measurements of photospheric magnetic fields Authors: Lagg, Andreas Bibcode: 2017psio.confE..31L Altcode: No abstract at ADS Title: Slipping reconnection in a solar flare observed in high resolution with the GREGOR solar telescope Authors: Sobotka, M.; Dudík, J.; Denker, C.; Balthasar, H.; Jurčák, J.; Liu, W.; Berkefeld, T.; Collados Vera, M.; Feller, A.; Hofmann, A.; Kneer, F.; Kuckein, C.; Lagg, A.; Louis, R. E.; von der Lühe, O.; Nicklas, H.; Schlichenmaier, R.; Schmidt, D.; Schmidt, W.; Sigwarth, M.; Solanki, S. K.; Soltau, D.; Staude, J.; Strassmeier, K. G.; Volkmer, R.; Waldmann, T. Bibcode: 2016A&A...596A...1S Altcode: 2016arXiv160500464S A small flare ribbon above a sunspot umbra in active region 12205 was observed on November 7, 2014, at 12:00 UT in the blue imaging channel of the 1.5 m GREGOR telescope, using a 1 Å Ca II H interference filter. Context observations from the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO), the Solar Optical Telescope (SOT) onboard Hinode, and the Interface Region Imaging Spectrograph (IRIS) show that this ribbon is part of a larger one that extends through the neighboring positive polarities and also participates in several other flares within the active region. We reconstructed a time series of 140 s of Ca II H images by means of the multiframe blind deconvolution method, which resulted in spatial and temporal resolutions of 0.1″ and 1 s. Light curves and horizontal velocities of small-scale bright knots in the observed flare ribbon were measured. Some knots are stationary, but three move along the ribbon with speeds of 7-11 km s-1. Two of them move in the opposite direction and exhibit highly correlated intensity changes, which provides evidence of a slipping reconnection at small spatial scales.

Movies associated to Figs. 1 and 2 are available at http://www.aanda.org Title: Deep probing of the photospheric sunspot penumbra: no evidence of field-free gaps Authors: Borrero, J. M.; Asensio Ramos, A.; Collados, M.; Schlichenmaier, R.; Balthasar, H.; Franz, M.; Rezaei, R.; Kiess, C.; Orozco Suárez, D.; Pastor Yabar, A.; Berkefeld, T.; von der Lühe, O.; Schmidt, D.; Schmidt, W.; Sigwarth, M.; Soltau, D.; Volkmer, R.; Waldmann, T.; Denker, C.; Hofmann, A.; Staude, J.; Strassmeier, K. G.; Feller, A.; Lagg, A.; Solanki, S. K.; Sobotka, M.; Nicklas, H. Bibcode: 2016A&A...596A...2B Altcode: 2016arXiv160708165B Context. Some models for the topology of the magnetic field in sunspot penumbrae predict regions free of magnetic fields or with only dynamically weak fields in the deep photosphere.
Aims: We aim to confirm or refute the existence of weak-field regions in the deepest photospheric layers of the penumbra.
Methods: We investigated the magnetic field at log τ5 = 0 is by inverting spectropolarimetric data of two different sunspots located very close to disk center with a spatial resolution of approximately 0.4-0.45''. The data have been recorded using the GRIS instrument attached to the 1.5-m solar telescope GREGOR at the El Teide observatory. The data include three Fe I lines around 1565 nm, whose sensitivity to the magnetic field peaks half a pressure scale height deeper than the sensitivity of the widely used Fe I spectral line pair at 630 nm. Before the inversion, the data were corrected for the effects of scattered light using a deconvolution method with several point spread functions.
Results: At log τ5 = 0 we find no evidence of regions with dynamically weak (B< 500 Gauss) magnetic fields in sunspot penumbrae. This result is much more reliable than previous investigations made on Fe I lines at 630 nm. Moreover, the result is independent of the number of nodes employed in the inversion, is independent of the point spread function used to deconvolve the data, and does not depend on the amount of stray light (I.e., wide-angle scattered light) considered. Title: Spectropolarimetric observations of an arch filament system with the GREGOR solar telescope Authors: Balthasar, H.; Gömöry, P.; González Manrique, S. J.; Kuckein, C.; Kavka, J.; Kučera, A.; Schwartz, P.; Vašková, R.; Berkefeld, T.; Collados Vera, M.; Denker, C.; Feller, A.; Hofmann, A.; Lagg, A.; Nicklas, H.; Orozco Suárez, D.; Pastor Yabar, A.; Rezaei, R.; Schlichenmaier, R.; Schmidt, D.; Schmidt, W.; Sigwarth, M.; Sobotka, M.; Solanki, S. K.; Soltau, D.; Staude, J.; Strassmeier, K. G.; Volkmer, R.; von der Lühe, O.; Waldmann, T. Bibcode: 2016AN....337.1050B Altcode: 2016arXiv160901514B Arch filament systems occur in active sunspot groups, where a fibril structure connects areas of opposite magnetic polarity, in contrast to active region filaments that follow the polarity inversion line. We used the GREGOR Infrared Spectrograph (GRIS) to obtain the full Stokes vector in the spectral lines Si I λ1082.7 nm, He I λ1083.0 nm, and Ca I λ1083.9 nm. We focus on the near-infrared calcium line to investigate the photospheric magnetic field and velocities, and use the line core intensities and velocities of the helium line to study the chromospheric plasma. The individual fibrils of the arch filament system connect the sunspot with patches of magnetic polarity opposite to that of the spot. These patches do not necessarily coincide with pores, where the magnetic field is strongest. Instead, areas are preferred not far from the polarity inversion line. These areas exhibit photospheric downflows of moderate velocity, but significantly higher downflows of up to 30 km s-1 in the chromospheric helium line. Our findings can be explained with new emerging flux where the matter flows downward along the field lines of rising flux tubes, in agreement with earlier results. Title: Magnetic fields of opposite polarity in sunspot penumbrae Authors: Franz, M.; Collados, M.; Bethge, C.; Schlichenmaier, R.; Borrero, J. M.; Schmidt, W.; Lagg, A.; Solanki, S. K.; Berkefeld, T.; Kiess, C.; Rezaei, R.; Schmidt, D.; Sigwarth, M.; Soltau, D.; Volkmer, R.; von der Luhe, O.; Waldmann, T.; Orozco, D.; Pastor Yabar, A.; Denker, C.; Balthasar, H.; Staude, J.; Hofmann, A.; Strassmeier, K.; Feller, A.; Nicklas, H.; Kneer, F.; Sobotka, M. Bibcode: 2016A&A...596A...4F Altcode: 2016arXiv160800513F Context. A significant part of the penumbral magnetic field returns below the surface in the very deep photosphere. For lines in the visible, a large portion of this return field can only be detected indirectly by studying its imprints on strongly asymmetric and three-lobed Stokes V profiles. Infrared lines probe a narrow layer in the very deep photosphere, providing the possibility of directly measuring the orientation of magnetic fields close to the solar surface.
Aims: We study the topology of the penumbral magnetic field in the lower photosphere, focusing on regions where it returns below the surface.
Methods: We analyzed 71 spectropolarimetric datasets from Hinode and from the GREGOR infrared spectrograph. We inferred the quality and polarimetric accuracy of the infrared data after applying several reduction steps. Techniques of spectral inversion and forward synthesis were used to test the detection algorithm. We compared the morphology and the fractional penumbral area covered by reversed-polarity and three-lobed Stokes V profiles for sunspots at disk center. We determined the amount of reversed-polarity and three-lobed Stokes V profiles in visible and infrared data of sunspots at various heliocentric angles. From the results, we computed center-to-limb variation curves, which were interpreted in the context of existing penumbral models.
Results: Observations in visible and near-infrared spectral lines yield a significant difference in the penumbral area covered by magnetic fields of opposite polarity. In the infrared, the number of reversed-polarity Stokes V profiles is smaller by a factor of two than in the visible. For three-lobed Stokes V profiles the numbers differ by up to an order of magnitude. Title: Horizontal flow fields in and around a small active region. The transition period between flux emergence and decay Authors: Verma, M.; Denker, C.; Balthasar, H.; Kuckein, C.; González Manrique, S. J.; Sobotka, M.; Bello González, N.; Hoch, S.; Diercke, A.; Kummerow, P.; Berkefeld, T.; Collados, M.; Feller, A.; Hofmann, A.; Kneer, F.; Lagg, A.; Löhner-Böttcher, J.; Nicklas, H.; Pastor Yabar, A.; Schlichenmaier, R.; Schmidt, D.; Schmidt, W.; Schubert, M.; Sigwarth, M.; Solanki, S. K.; Soltau, D.; Staude, J.; Strassmeier, K. G.; Volkmer, R.; von der Lühe, O.; Waldmann, T. Bibcode: 2016A&A...596A...3V Altcode: 2016arXiv160507462V Context. The solar magnetic field is responsible for all aspects of solar activity. Thus, emergence of magnetic flux at the surface is the first manifestation of the ensuing solar activity.
Aims: Combining high-resolution and synoptic observations aims to provide a comprehensive description of flux emergence at photospheric level and of the growth process that eventually leads to a mature active region.
Methods: The small active region NOAA 12118 emerged on 2014 July 17 and was observed one day later with the 1.5-m GREGOR solar telescope on 2014 July 18. High-resolution time-series of blue continuum and G-band images acquired in the blue imaging channel (BIC) of the GREGOR Fabry-Pérot Interferometer (GFPI) were complemented by synoptic line-of-sight magnetograms and continuum images obtained with the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). Horizontal proper motions and horizontal plasma velocities were computed with local correlation tracking (LCT) and the differential affine velocity estimator (DAVE), respectively. Morphological image processing was employed to measure the photometric and magnetic area, magnetic flux, and the separation profile of the emerging flux region during its evolution.
Results: The computed growth rates for photometric area, magnetic area, and magnetic flux are about twice as high as the respective decay rates. The space-time diagram using HMI magnetograms of five days provides a comprehensive view of growth and decay. It traces a leaf-like structure, which is determined by the initial separation of the two polarities, a rapid expansion phase, a time when the spread stalls, and a period when the region slowly shrinks again. The separation rate of 0.26 km s-1 is highest in the initial stage, and it decreases when the separation comes to a halt. Horizontal plasma velocities computed at four evolutionary stages indicate a changing pattern of inflows. In LCT maps we find persistent flow patterns such as outward motions in the outer part of the two major pores, a diverging feature near the trailing pore marking the site of upwelling plasma and flux emergence, and low velocities in the interior of dark pores. We detected many elongated rapidly expanding granules between the two major polarities, with dimensions twice as large as the normal granules. Title: Upper chromospheric magnetic field of a sunspot penumbra: observations of fine structure Authors: Joshi, J.; Lagg, A.; Solanki, S. K.; Feller, A.; Collados, M.; Orozco Suárez, D.; Schlichenmaier, R.; Franz, M.; Balthasar, H.; Denker, C.; Berkefeld, T.; Hofmann, A.; Kiess, C.; Nicklas, H.; Pastor Yabar, A.; Rezaei, R.; Schmidt, D.; Schmidt, W.; Sobotka, M.; Soltau, D.; Staude, J.; Strassmeier, K. G.; Volkmer, R.; von der Lühe, O.; Waldmann, T. Bibcode: 2016A&A...596A...8J Altcode: 2016arXiv160801988J
Aims: The fine-structure of the magnetic field in a sunspot penumbra in the upper chromosphere is to be explored and compared to that in the photosphere.
Methods: Spectropolarimetric observations with high spatial resolution were recorded with the 1.5-m GREGOR telescope using the GREGOR Infrared Spectrograph (GRIS). The observed spectral domain includes the upper chromospheric Hei triplet at 10 830 Å and the photospheric Sii 10 827.1 Å and Cai 10 833.4 Å spectral lines. The upper chromospheric magnetic field is obtained by inverting the Hei triplet assuming a Milne-Eddington-type model atmosphere. A height-dependent inversion was applied to the Sii 10 827.1 Å and Cai 10 833.4 Å lines to obtain the photospheric magnetic field.
Results: We find that the inclination of the magnetic field varies in the azimuthal direction in the photosphere and in the upper chromosphere. The chromospheric variations coincide remarkably well with the variations in the inclination of the photospheric field and resemble the well-known spine and interspine structure in the photospheric layers of penumbrae. The typical peak-to-peak variations in the inclination of the magnetic field in the upper chromosphere are found to be 10°-15°, which is roughly half the variation in the photosphere. In contrast, the magnetic field strength of the observed penumbra does not vary on small spatial scales in the upper chromosphere.
Conclusions: Thanks to the high spatial resolution of the observations that is possible with the GREGOR telescope at 1.08 microns, we find that the prominent small-scale fluctuations in the magnetic field inclination, which are a salient part of the property of sunspot penumbral photospheres, also persist in the chromosphere, although at somewhat reduced amplitudes. Such a complex magnetic configuration may facilitate penumbral chromospheric dynamic phenomena, such as penumbral micro-jets or transient bright dots. Title: Active region fine structure observed at 0.08 arcsec resolution Authors: Schlichenmaier, R.; von der Lühe, O.; Hoch, S.; Soltau, D.; Berkefeld, T.; Schmidt, D.; Schmidt, W.; Denker, C.; Balthasar, H.; Hofmann, A.; Strassmeier, K. G.; Staude, J.; Feller, A.; Lagg, A.; Solanki, S. K.; Collados, M.; Sigwarth, M.; Volkmer, R.; Waldmann, T.; Kneer, F.; Nicklas, H.; Sobotka, M. Bibcode: 2016A&A...596A...7S Altcode: 2016arXiv160707094S Context. The various mechanisms of magneto-convective energy transport determine the structure of sunspots and active regions.
Aims: We characterise the appearance of light bridges and other fine-structure details and elaborate on their magneto-convective nature.
Methods: We present speckle-reconstructed images taken with the broad-band imager (BBI) at the 1.5 m GREGOR telescope in the 486 nm and 589 nm bands. We estimate the spatial resolution from the noise characteristics of the image bursts and obtain 0.08″ at 589 nm. We describe structure details in individual best images as well as the temporal evolution of selected features.
Results: We find branched dark lanes extending along thin (≈1″) light bridges in sunspots at various heliocentric angles. In thick (≳ 2″) light bridges the branches are disconnected from the central lane and have a Y shape with a bright grain toward the umbra. The images reveal that light bridges exist on varying intensity levels and that their small-scale features evolve on timescales of minutes. Faint light bridges show dark lanes outlined by the surrounding bright features. Dark lanes are very common and are also found in the boundary of pores. They have a characteristic width of 0.1″ or smaller. Intergranular dark lanes of that width are seen in active region granulation.
Conclusions: We interpret our images in the context of magneto-convective simulations and findings: while central dark lanes in thin light bridges are elevated and associated with a density increase above upflows, the dark lane branches correspond to locations of downflows and are depressed relative to the adjacent bright plasma. Thick light bridges with central dark lanes show no projection effect. They have a flat elevated plateau that falls off steeply at the umbral boundary. There, Y-shaped filaments form as they do in the inner penumbra. This indicates the presence of inclined magnetic fields, meaning that the umbral magnetic field is wrapped around the convective light bridge. Title: Probing deep photospheric layers of the quiet Sun with high magnetic sensitivity Authors: Lagg, A.; Solanki, S. K.; Doerr, H. -P.; Martínez González, M. J.; Riethmüller, T.; Collados Vera, M.; Schlichenmaier, R.; Orozco Suárez, D.; Franz, M.; Feller, A.; Kuckein, C.; Schmidt, W.; Asensio Ramos, A.; Pastor Yabar, A.; von der Lühe, O.; Denker, C.; Balthasar, H.; Volkmer, R.; Staude, J.; Hofmann, A.; Strassmeier, K.; Kneer, F.; Waldmann, T.; Borrero, J. M.; Sobotka, M.; Verma, M.; Louis, R. E.; Rezaei, R.; Soltau, D.; Berkefeld, T.; Sigwarth, M.; Schmidt, D.; Kiess, C.; Nicklas, H. Bibcode: 2016A&A...596A...6L Altcode: 2016arXiv160506324L Context. Investigations of the magnetism of the quiet Sun are hindered by extremely weak polarization signals in Fraunhofer spectral lines. Photon noise, straylight, and the systematically different sensitivity of the Zeeman effect to longitudinal and transversal magnetic fields result in controversial results in terms of the strength and angular distribution of the magnetic field vector.
Aims: The information content of Stokes measurements close to the diffraction limit of the 1.5 m GREGOR telescope is analyzed. We took the effects of spatial straylight and photon noise into account.
Methods: Highly sensitive full Stokes measurements of a quiet-Sun region at disk center in the deep photospheric Fe I lines in the 1.56 μm region were obtained with the infrared spectropolarimeter GRIS at the GREGOR telescope. Noise statistics and Stokes V asymmetries were analyzed and compared to a similar data set of the Hinode spectropolarimeter (SOT/SP). Simple diagnostics based directly on the shape and strength of the profiles were applied to the GRIS data. We made use of the magnetic line ratio technique, which was tested against realistic magneto-hydrodynamic simulations (MURaM).
Results: About 80% of the GRIS spectra of a very quiet solar region show polarimetric signals above a 3σ level. Area and amplitude asymmetries agree well with small-scale surface dynamo-magneto hydrodynamic simulations. The magnetic line ratio analysis reveals ubiquitous magnetic regions in the ten to hundred Gauss range with some concentrations of kilo-Gauss fields.
Conclusions: The GRIS spectropolarimetric data at a spatial resolution of ≈0.̋4 are so far unique in the combination of high spatial resolution scans and high magnetic field sensitivity. Nevertheless, the unavoidable effect of spatial straylight and the resulting dilution of the weak Stokes profiles means that inversion techniques still bear a high risk of misinterpretating the data. Title: Flow and magnetic field properties in the trailing sunspots of active region NOAA 12396 Authors: Verma, M.; Denker, C.; Böhm, F.; Balthasar, H.; Fischer, C. E.; Kuckein, C.; Bello González, N.; Berkefeld, T.; Collados, M.; Diercke, A.; Feller, A.; González Manrique, S. J.; Hofmann, A.; Lagg, A.; Nicklas, H.; Orozco Suárez, D.; Pator Yabar, A.; Rezaei, R.; Schlichenmaier, R.; Schmidt, D.; Schmidt, W.; Sigwarth, M.; Sobotka, M.; Solanki, S. K.; Soltau, D.; Staude, J.; Strassmeier, K. G.; Volkmer, R.; von der Lühe, O.; Waldmann, T. Bibcode: 2016AN....337.1090V Altcode: Improved measurements of the photospheric and chromospheric three-dimensional magnetic and flow fields are crucial for a precise determination of the origin and evolution of active regions. We present an illustrative sample of multi-instrument data acquired during a two-week coordinated observing campaign in August 2015 involving, among others, the GREGOR solar telescope (imaging and near-infrared spectroscopy) and the space missions Solar Dynamics Observatory (SDO) and Interface Region Imaging Spectrograph (IRIS). The observations focused on the trailing part of active region NOAA 12396 with complex polarity inversion lines and strong intrusions of opposite polarity flux. The GREGOR Infrared Spectrograph (GRIS) provided Stokes IQUV spectral profiles in the photospheric Si I λ1082.7 nm line, the chromospheric He I λ1083.0 nm triplet, and the photospheric Ca I λ1083.9 nm line. Carefully calibrated GRIS scans of the active region provided maps of Doppler velocity and magnetic field at different atmospheric heights. We compare quick-look maps with those obtained with the ``Stokes Inversions based on Response functions'' (SIR) code, which furnishes deeper insight into the magnetic properties of the region. We find supporting evidence that newly emerging flux and intruding opposite polarity flux are hampering the formation of penumbrae, i.e., a penumbra fully surrounding a sunspot is only expected after cessation of flux emergence in proximity to the sunspots. Title: Three-dimensional structure of a sunspot light bridge Authors: Felipe, T.; Collados, M.; Khomenko, E.; Kuckein, C.; Asensio Ramos, A.; Balthasar, H.; Berkefeld, T.; Denker, C.; Feller, A.; Franz, M.; Hofmann, A.; Joshi, J.; Kiess, C.; Lagg, A.; Nicklas, H.; Orozco Suárez, D.; Pastor Yabar, A.; Rezaei, R.; Schlichenmaier, R.; Schmidt, D.; Schmidt, W.; Sigwarth, M.; Sobotka, M.; Solanki, S. K.; Soltau, D.; Staude, J.; Strassmeier, K. G.; Volkmer, R.; von der Lühe, O.; Waldmann, T. Bibcode: 2016A&A...596A..59F Altcode: 2016arXiv161104803F Context. Active regions are the most prominent manifestations of solar magnetic fields; their generation and dissipation are fundamental problems in solar physics. Light bridges are commonly present during sunspot decay, but a comprehensive picture of their role in the removal of the photospheric magnetic field is still lacking.
Aims: We study the three-dimensional configuration of a sunspot, and in particular, its light bridge, during one of the last stages of its decay.
Methods: We present the magnetic and thermodynamical stratification inferred from full Stokes inversions of the photospheric Si I 10 827 Å and Ca I 10 839 Å lines obtained with the GREGOR Infrared Spectrograph of the GREGOR telescope at the Observatorio del Teide, Tenerife, Spain. The analysis is complemented by a study of continuum images covering the disk passage of the active region, which are provided by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory.
Results: The sunspot shows a light bridge with penumbral continuum intensity that separates the central umbra from a smaller umbra. We find that in this region the magnetic field lines form a canopy with lower magnetic field strength in the inner part. The photospheric light bridge is dominated by gas pressure (high-β), as opposed to the surrounding umbra, where the magnetic pressure is higher. A convective flow is observed in the light bridge. This flow is able to bend the magnetic field lines and to produce field reversals. The field lines merge above the light bridge and become as vertical and strong as in the surrounding umbra. We conclude that this occurs because two highly magnetized regions approach each other during the sunspot evolution.

Movies associated to Figs. 2 and 13 are available at http://www.aanda.org Title: Inference of magnetic fields in the very quiet Sun Authors: Martínez González, M. J.; Pastor Yabar, A.; Lagg, A.; Asensio Ramos, A.; Collados, M.; Solanki, S. K.; Balthasar, H.; Berkefeld, T.; Denker, C.; Doerr, H. P.; Feller, A.; Franz, M.; González Manrique, S. J.; Hofmann, A.; Kneer, F.; Kuckein, C.; Louis, R.; von der Lühe, O.; Nicklas, H.; Orozco, D.; Rezaei, R.; Schlichenmaier, R.; Schmidt, D.; Schmidt, W.; Sigwarth, M.; Sobotka, M.; Soltau, D.; Staude, J.; Strassmeier, K. G.; Verma, M.; Waldman, T.; Volkmer, R. Bibcode: 2016A&A...596A...5M Altcode: 2018arXiv180410089M Context. Over the past 20 yr, the quietest areas of the solar surface have revealed a weak but extremely dynamic magnetism occurring at small scales (<500 km), which may provide an important contribution to the dynamics and energetics of the outer layers of the atmosphere. Understanding this magnetism requires the inference of physical quantities from high-sensitivity spectro-polarimetric data with high spatio-temporal resolution.
Aims: We present high-precision spectro-polarimetric data with high spatial resolution (0.4'') of the very quiet Sun at 1.56 μm obtained with the GREGOR telescope to shed some light on this complex magnetism.
Methods: We used inversion techniques in two main approaches. First, we assumed that the observed profiles can be reproduced with a constant magnetic field atmosphere embedded in a field-free medium. Second, we assumed that the resolution element has a substructure with either two constant magnetic atmospheres or a single magnetic atmosphere with gradients of the physical quantities along the optical depth, both coexisting with a global stray-light component.
Results: Half of our observed quiet-Sun region is better explained by magnetic substructure within the resolution element. However, we cannot distinguish whether this substructure comes from gradients of the physical parameters along the line of sight or from horizontal gradients (across the surface). In these pixels, a model with two magnetic components is preferred, and we find two distinct magnetic field populations. The population with the larger filling factor has very weak ( 150 G) horizontal fields similar to those obtained in previous works. We demonstrate that the field vector of this population is not constrained by the observations, given the spatial resolution and polarimetric accuracy of our data. The topology of the other component with the smaller filling factor is constrained by the observations for field strengths above 250 G: we infer hG fields with inclinations and azimuth values compatible with an isotropic distribution. The filling factors are typically below 30%. We also find that the flux of the two polarities is not balanced. From the other half of the observed quiet-Sun area 50% are two-lobed Stokes V profiles, meaning that 23% of the field of view can be adequately explained with a single constant magnetic field embedded in a non-magnetic atmosphere. The magnetic field vector and filling factor are reliable inferred in only 50% based on the regular profiles. Therefore, 12% of the field of view harbour hG fields with filling factors typically below 30%. At our present spatial resolution, 70% of the pixels apparently are non-magnetised. Title: Fitting peculiar spectral profiles in He I 10830Å absorption features Authors: González Manrique, S. J.; Kuckein, C.; Pastor Yabar, A.; Collados, M.; Denker, C.; Fischer, C. E.; Gömöry, P.; Diercke, A.; Bello González, N.; Schlichenmaier, R.; Balthasar, H.; Berkefeld, T.; Feller, A.; Hoch, S.; Hofmann, A.; Kneer, F.; Lagg, A.; Nicklas, H.; Orozco Suárez, D.; Schmidt, D.; Schmidt, W.; Sigwarth, M.; Sobotka, M.; Solanki, S. K.; Soltau, D.; Staude, J.; Strassmeier, K. G.; Verma, M.; Volkmer, R.; von der Lühe, O.; Waldmann, T. Bibcode: 2016AN....337.1057G Altcode: 2016arXiv160300679G The new generation of solar instruments provides better spectral, spatial, and temporal resolution for a better understanding of the physical processes that take place on the Sun. Multiple-component profiles are more commonly observed with these instruments. Particularly, the He I 10830 Å triplet presents such peculiar spectral profiles, which give information on the velocity and magnetic fine structure of the upper chromosphere. The purpose of this investigation is to describe a technique to efficiently fit the two blended components of the He I 10830 Å triplet, which are commonly observed when two atmospheric components are located within the same resolution element. The observations used in this study were taken on 2015 April 17 with the very fast spectroscopic mode of the GREGOR Infrared Spectrograph (GRIS) attached to the 1.5-m GREGOR solar telescope, located at the Observatorio del Teide, Tenerife, Spain. We apply a double-Lorentzian fitting technique using Levenberg-Marquardt least-squares minimization. This technique is very simple and much faster than inversion codes. Line-of-sight Doppler velocities can be inferred for a whole map of pixels within just a few minutes. Our results show sub- and supersonic downflow velocities of up to 32 km s-1 for the fast component in the vicinity of footpoints of filamentary structures. The slow component presents velocities close to rest. Title: The vertical thickness of Jupiter's Europa gas torus from charged particle measurements Authors: Kollmann, P.; Paranicas, C.; Clark, G.; Roussos, E.; Lagg, A.; Krupp, N. Bibcode: 2016GeoRL..43.9425K Altcode: Measurements and modeling suggest the presence of a neutral gas torus collocated with the orbit of Jupiter's moon Europa. Here we use data from the CMS instrument that is part of the Energetic Particles Detector (EPD) on board the Galileo spacecraft to characterize the distribution of 130 keV protons. Near the orbit of Europa this distribution has a minimum around 70° in equatorial pitch angle. We reproduce this with a model assuming that the protons are lost via charge exchange with a gas torus. Since the pitch angle characterizes whether the protons remain mostly in the dense center of the torus or continuously bounce through it, we can determine the latitudinal extent of the torus. We find that the full thickness where its density falls to 1/e of its maximum has to be ≲2RJ and is closer to ≈1RJ. Title: Formation of a solar Hα filament from orphan penumbrae Authors: Buehler, D.; Lagg, A.; van Noort, M.; Solanki, S. K. Bibcode: 2016A&A...589A..31B Altcode: 2016arXiv160305899B
Aims: The formation and evolution of an Hα filament in active region (AR) 10953 is described.
Methods: Observations from the Solar Optical Telescope (SOT) aboard the Hinode satellite starting from UT 18:09 on 27th April 2007 until UT 06:08 on 1st May 2007 were analysed. 20 scans of the 6302 Å Fe I line pair recorded by SOT/SP were inverted using the spatially coupled version of the SPINOR code. The inversions were analysed together with co-spatial SOT/BFI G-band and Ca II H and SOT/NFI Hα observations.
Results: Following the disappearance of an initial Hα filament aligned along the polarity inversion line (PIL) of the AR, a new Hα filament formed in its place some 20 h later, which remained stable for, at least, another 1.5 days. The creation of the new Hα filament was driven by the ascent of horizontal magnetic fields from the photosphere into the chromosphere at three separate locations along the PIL. The magnetic fields at two of these locations were situated directly underneath the initial Hα filament and formed orphan penumbrae already aligned along the Hα filament channel. The 700 G orphan penumbrae were stable and trapped in the photosphere until the disappearance of the overlying initial Hα filament, after which they started to ascend into the chromosphere at 10 ± 5 m/s. Each ascent was associated with a simultaneous magnetic flux reduction of up to 50% in the photosphere. The ascended orphan penumbrae formed dark seed structures in Hα in parallel with the PIL, which elongated and merged to form an Hα filament. The filament channel featured horizontal magnetic fields of on average 260 G at log (τ) = -2 suspended above the nearly field-free lower photosphere. The fields took on an overall inverse configuration at log (τ) = -2 suggesting a flux rope topology for the new Hα filament. The destruction of the initial Hα filament was likely caused by the flux emergence at the third location along the PIL.
Conclusions: We present a new interpretation of the Hα filament formation in AR 10953 whereby the mainly horizontal fields of orphan penumbrae, aligned along the Hα filament channel, ascend into the chromosphere, forming seed fragments for a new, second Hα filament. The orphan penumbral fields ascend into the chromosphere ~9-24 h before the Hα filament is fully formed. Title: Flows in and around Active Region NOAA12118 Observed with the GREGOR Solar Telescope and SDO/HMI Authors: Verma, M.; Denker, C.; Balthasar, H.; Kuckein, C.; González Manrique, S. J.; Sobotka, M.; Bello González, N.; Hoch, S.; Diercke, A.; Kummerow, P.; Berkefeld, T.; Collados, M.; Feller, A.; Hofmann, A.; Kneer, F.; Lagg, A.; Löhner-Böttcher, J.; Nicklas, H.; Pastor Yabar, A.; Schlichenmaier, R.; Schmidt, D.; Schmidt, W.; Schubert, M.; Sigwarth, M.; Solanki, S. K.; Soltau, D.; Staude, J.; Strassmeier, K.; Volkmer, R.; von der Lühe, O.; Waldmann, T. Bibcode: 2016ASPC..504...29V Altcode: 2016arXiv160301109V Accurate measurements of magnetic and velocity fields in and around solar active regions are key to unlocking the mysteries of the formation and the decay of sunspots. High spatial resolution images and spectral sequences with a high cadence obtained with the GREGOR solar telescope give us an opportunity to scrutinize 3-D flow fields with local correlation tracking and imaging spectroscopy. We present GREGOR early science data acquired in 2014 July - August with the GREGOR Fabry-Pérot Interferometer and the Blue Imaging Channel. Time-series of blue continuum (λ 450.6 nm) images of the small active region NOAA 12118 were restored with the speckle masking technique to derive horizontal proper motions and to track the evolution of morphological changes. In addition, high-resolution observations are discussed in the context of synoptic data from the Solar Dynamics Observatory. Title: Depth-dependent global properties of a sunspot observed by Hinode using the Solar Optical Telescope/Spectropolarimeter Authors: Tiwari, Sanjiv K.; van Noort, Michiel; Solanki, Sami K.; Lagg, Andreas Bibcode: 2015A&A...583A.119T Altcode: 2015arXiv150804830T Context. For the past two decades, the three-dimensional structure of sunspots has been studied extensively. A recent improvement in the Stokes inversion technique prompts us to revisit the depth-dependent properties of sunspots.
Aims: In the present work, we aim to investigate the global depth-dependent thermal, velocity, and magnetic properties of a sunspot, as well as the interconnection between various local properties.
Methods: We analysed high-quality Stokes profiles of the disk-centred, regular, leading sunspot of NOAA AR 10933, acquired by the Solar Optical Telescope/Spectropolarimeter (SOT/SP) on board the Hinode spacecraft. To obtain depth-dependent stratification of the physical parameters, we used the recently developed, spatially coupled version of the SPINOR inversion code.
Results: First, we study the azimuthally averaged physical parameters of the sunspot. We find that the vertical temperature gradient in the lower- to mid-photosphere is at its weakest in the umbra, while it is considerably stronger in the penumbra, and stronger still in the spot's surroundings. The azimuthally averaged field becomes more horizontal with radial distance from the centre of the spot, but more vertical with height. At continuum optical depth unity, the line-of-sight velocity shows an average upflow of ~300 ms-1 in the inner penumbra and an average downflow of ~1300 ms-1 in the outer penumbra. The downflow continues outside the visible penumbral boundary. The sunspot shows, at most, a moderate negative twist of <5° at log (τ) = 0, which increases with height. The sunspot umbra and the spines of the penumbra show considerable similarity with regard to their physical properties, albeit with some quantitative differences (weaker, somewhat more horizontal fields in spines, commensurate with their location being further away from the sunspot's core). The temperature shows a general anti-correlation with the field strength, with the exception of the heads of penumbral filaments, where a weak positive correlation is found. The dependence of the physical parameters on each other over the full sunspot shows a qualitative similarity to that of a standard penumbral filament and its surrounding spines.
Conclusions: The large-scale variation in the physical parameters of a sunspot at various optical depths is presented. Our results suggest that the spines in the penumbra are basically the outward extension of the umbra. The spines and the penumbral filaments, together, are the basic elements that form a sunspot penumbra. Title: Statistical analysis of supersonic downflows in sunspot penumbrae. Authors: Kim, Hyunnam; Lagg, Andreas; Solanki, Sami K.; Narayan, Gautam; van Noort, Michiel; Kim, Kap-Sung Bibcode: 2015IAUGA..2254868K Altcode: Supersonic downflow patches was found in the outer edge of sunspot penumbra. These patches are believed to be the return channels of the Evershed flow. There was previous study to investigate their structure in detail using Hinode SOT/SP observations (M. van Noort et al. 2013) but their data sample was only two sunspots. To make general description it needs to check more sunspot data sample.We selected 242 downflow patches of 16 sunspots using Hinode SOT/SP observations from 2006 to 2012. Height-dependent maps of atmospheric parameters of these downflows was produced by using HeLix which was height dependent LTE inversion code of Stokes profiles.Statistical analysis of magnetic field strength, inclination angle of field line, temperature and line-of-sight velocity are presented. The recovered atmospheric data tell us that downflow patches have different physical signatures comparing normal penumbra properties. Furthermore, our results of three height-dependent layer support that heating process should occur on the downflow patches in the middle of layer. Title: Using Realistic MHD Simulations for Modeling and Interpretation of Quiet-Sun Observations with the Solar Dynamics Observatory Helioseismic and Magnetic Imager Authors: Kitiashvili, I. N.; Couvidat, S.; Lagg, A. Bibcode: 2015ApJ...808...59K Altcode: 2014arXiv1407.2663K The solar atmosphere is extremely dynamic, and many important phenomena develop on small scales that are unresolved in observations with the Helioseismic and Magnetic Imager (HMI) instrument on the Solar Dynamics Observatory. For correct calibration and interpretation of the observations, it is very important to investigate the effects of small-scale structures and dynamics on the HMI observables, such as Doppler shift, continuum intensity, spectral line depth, and width. We use 3D radiative hydrodynamics simulations of the upper turbulent convective layer and the atmosphere of the Sun, and a spectro-polarimetric radiative transfer code to study observational characteristics of the Fe i 6173 Å line observed by HMI in quiet-Sun regions. We use the modeling results to investigate the sensitivity of the line Doppler shift to plasma velocity, and also sensitivities of the line parameters to plasma temperature and density, and determine effective line formation heights for observations of solar regions located at different distances from the disk center. These estimates are important for the interpretation of helioseismology measurements. In addition, we consider various center-to-limb effects, such as convective blueshift, variations of helioseismic travel-times, and the “concave” Sun effect, and show that the simulations can qualitatively reproduce the observed phenomena, indicating that these effects are related to a complex interaction of the solar dynamics and radiative transfer. Title: Variation in sunspot properties between 1999 and 2014 Authors: Rezaei, R.; Beck, C.; Lagg, A.; Borrero, J. M.; Schmidt, W.; Collados, M. Bibcode: 2015A&A...578A..43R Altcode:
Aims: We study the variation in the magnetic field strength, area, and continuum intensity of umbrae in solar cycles 23 and 24.
Methods: We analyzed a sample of 374 sunspots observed from 1999 until 2014 with the Tenerife Infrared Polarimeter at the German Vacuum Tower Telescope and the Facility InfRared Spectropolarimeter at the Dunn Solar Telescope. The sample of field strength, area, and intensities was used to trace any long-term or cyclic trend of umbral properties in the last 15 years.
Results: Sunspots are systematically weaker, that is, have a weaker field strength and stronger continuum intensity, toward the end of cycle 23 than they had at the maximum of cycle 23. The linear trend reverses with the onset of cycle 24. We find that the field strength decreases in the declining phase of cycle 23 by about 112 (± 16) G yr-1, while it increases in the rising phase of cycle 24 by about 138 (± 72) G yr-1. The umbral intensity shows the opposite trend: the intensity increases with a rate of 0.7 (± 0.3)% of Ic yr-1 toward the end of cycle 23 and decreases with a rate of 3.8 (± 1.5)% of Ic yr-1 toward the maximum of cycle 24. The distribution of the umbral maximum field strength in cycle 24 is similar to that of cycle 23, but is slightly shifted toward lower values by about 80 G, corresponding to a possible long-term gradient in umbral field strength of about 7 ± 4 G yr-1. If instead of the maximum umbral field we consider the average value over the entire umbra, the distribution shifts by about 44 Gauss.
Conclusions: The umbral brightness decreases in the rising stage of a solar cycle, but increases from maximum toward the end of the cycle. Our results do not indicate a drastic change of the solar cycle toward a grand minimum in the near future. Title: Properties of solar plage from a spatially coupled inversion of Hinode SP data Authors: Buehler, D.; Lagg, A.; Solanki, S. K.; van Noort, M. Bibcode: 2015A&A...576A..27B Altcode: 2015arXiv150101151B
Aims: The properties of magnetic fields forming an extended plage region in AR 10953 were investigated.
Methods: Stokes spectra of the Fe I line pair at 6302 Å recorded by the spectropolarimeter aboard the Hinode satellite were inverted using the SPINOR code. The code performed a 2D spatially coupled inversion on the Stokes spectra, allowing the retrieval of gradients in optical depth within the atmosphere of each pixel, whilst accounting for the effects of the instrument's PSF. Consequently, no magnetic filling factor was needed.
Results: The inversion results reveal that plage is composed of magnetic flux concentrations (MFCs) with typical field strengths of 1520 G at log (τ) = -0.9 and inclinations of 10°-15°. The MFCs expand by forming magnetic canopies composed of weaker and more inclined magnetic fields. The expansion and average temperature stratification of isolated MFCs can be approximated well with an empirical plage thin flux tube model. The highest temperatures of MFCs are located at their edges in all log (τ) layers. Whilst the plasma inside MFCs is nearly at rest, each is surrounded by a ring of downflows of on average 2.4 km s-1 at log (τ) = 0 and peak velocities of up to 10 km s-1, which are supersonic. The downflow ring of an MFC weakens and shifts outwards with height, tracing the MFC's expansion. Such downflow rings often harbour magnetic patches of opposite polarity to that of the main MFC with typical field strengths below 300 G at log (τ) = 0. These opposite polarity patches are situated beneath the canopy of their main MFC. We found evidence of a strong broadening of the Stokes profiles in MFCs and particularly in the downflow rings surrounding MFCs (expressed by a microturbulence in the inversion). This indicates the presence of strong unresolved velocities. Larger magnetic structures such as sunspots cause the field of nearby MFCs to be more inclined. Title: Comparison of inversion codes for polarized line formation in MHD simulations. I. Milne-Eddington codes Authors: Borrero, J. M.; Lites, B. W.; Lagg, A.; Rezaei, R.; Rempel, M. Bibcode: 2014A&A...572A..54B Altcode: 2014arXiv1409.3376B Milne-Eddington (M-E) inversion codes for the radiative transfer equation are the most widely used tools to infer the magnetic field from observations of the polarization signals in photospheric and chromospheric spectral lines. Unfortunately, a comprehensive comparison between the different M-E codes available to the solar physics community is still missing, and so is a physical interpretation of their inferences. In this contribution we offer a comparison between three of those codes (VFISV, ASP/HAO, and HeLIx+). These codes are used to invert synthetic Stokes profiles that were previously obtained from realistic non-grey three-dimensional magnetohydrodynamical (3D MHD) simulations. The results of the inversion are compared with each other and with those from the MHD simulations. In the first case, the M-E codes retrieve values for the magnetic field strength, inclination and line-of-sight velocity that agree with each other within σB ≤ 35 (Gauss), σγ ≤ 1.2°, and σv ≤ 10 m s-1, respectively. Additionally, M-E inversion codes agree with the numerical simulations, when compared at a fixed optical depth, within σB ≤ 130 (Gauss), σγ ≤ 5°, and σv ≤ 320 m s-1. Finally, we show that employing generalized response functions to determine the height at which M-E codes measure physical parameters is more meaningful than comparing at a fixed geometrical height or optical depth. In this case the differences between M-E inferences and the 3D MHD simulations decrease to σB ≤ 90 (Gauss), σγ ≤ 3°, and σv ≤ 90 m s-1. Title: Inclinations of small quiet-Sun magnetic features based on a new geometric approach Authors: Jafarzadeh, S.; Solanki, S. K.; Lagg, A.; Bellot Rubio, L. R.; van Noort, M.; Feller, A.; Danilovic, S. Bibcode: 2014A&A...569A.105J Altcode: 2014arXiv1408.2443J Context. High levels of horizontal magnetic flux have been reported in the quiet-Sun internetwork, often based on Stokes profile inversions.
Aims: Here we introduce a new method for deducing the inclination of magnetic elements and use it to test magnetic field inclinations from inversions.
Methods: We determine accurate positions of a set of small, bright magnetic elements in high spatial resolution images sampling different photospheric heights obtained by the Sunrise balloon-borne solar observatory. Together with estimates of the formation heights of the employed spectral bands, these provide us with the inclinations of the magnetic features. We also compute the magnetic inclination angle of the same magnetic features from the inversion of simultaneously recorded Stokes parameters.
Results: Our new, geometric method returns nearly vertical fields (average inclination of around 14° with a relatively narrow distribution having a standard deviation of 6°). In strong contrast to this, the traditionally used inversions give almost horizontal fields (average inclination of 75 ± 8°) for the same small magnetic features, whose linearly polarised Stokes profiles are adversely affected by noise. We show that for such magnetic features inversions overestimate the flux in horizontal magnetic fields by an order of magnitude.
Conclusions: The almost vertical field of bright magnetic features from our geometric method is clearly incompatible with the nearly horizontal magnetic fields obtained from the inversions. This indicates that the amount of magnetic flux in horizontal fields deduced from inversions is overestimated in the presence of weak Stokes signals, in particular if Stokes Q and U are close to or under the noise level. Inversions should be used with great caution when applied to data with no clear Stokes Q and no U signal. By combining the proposed method with inversions we are not just improving the inclination, but also the field strength. This technique allows us to analyse features that are not reliably treated by inversions, thus greatly extending our capability to study the complete magnetic field of the quiet Sun. Title: Vigorous convection in a sunspot granular light bridge Authors: Lagg, Andreas; Solanki, Sami K.; van Noort, Michiel; Danilovic, Sanja Bibcode: 2014A&A...568A..60L Altcode: 2014arXiv1407.1202L Context. Light bridges are the most prominent manifestation of convection in sunspots. The brightest representatives are granular light bridges composed of features that appear to be similar to granules.
Aims: An in-depth study of the convective motions, temperature stratification, and magnetic field vector in and around light bridge granules is presented with the aim of identifying similarities and differences to typical quiet-Sun granules.
Methods: Spectropolarimetric data from the Hinode Solar Optical Telescope were analyzed using a spatially coupled inversion technique to retrieve the stratified atmospheric parameters of light bridge and quiet-Sun granules.
Results: Central hot upflows surrounded by cooler fast downflows reaching 10 km s-1 clearly establish the convective nature of the light bridge granules. The inner part of these granules in the near surface layers is field free and is covered by a cusp-like magnetic field configuration. We observe hints of field reversals at the location of the fast downflows. The quiet-Sun granules in the vicinity of the sunspot are covered by a low-lying canopy field extending radially outward from the spot.
Conclusions: The similarities between quiet-Sun and light bridge granules point to the deep anchoring of granular light bridges in the underlying convection zone. The fast, supersonic downflows are most likely a result of a combination of invigorated convection in the light bridge granule due to radiative cooling into the neighboring umbra and the fact that we sample deeper layers, since the downflows are immediately adjacent to the slanted walls of the Wilson depression.

The two movies are available in electronic form at http://www.aanda.org Title: Migration of Ca II H bright points in the internetwork Authors: Jafarzadeh, S.; Cameron, R. H.; Solanki, S. K.; Pietarila, A.; Feller, A.; Lagg, A.; Gandorfer, A. Bibcode: 2014A&A...563A.101J Altcode: 2014arXiv1401.7522J Context. The migration of magnetic bright point-like features (MBP) in the lower solar atmosphere reflects the dispersal of magnetic flux as well as the horizontal flows of the atmospheric layer they are embedded in.
Aims: We analyse trajectories of the proper motion of intrinsically magnetic, isolated internetwork Ca ii H MBPs (mean lifetime 461 ± 9 s) to obtain their diffusivity behaviour.
Methods: We use seeing-free high spatial and temporal resolution image sequences of quiet-Sun, disc-centre observations obtained in the Ca ii H 3968 Å passband of the Sunrise Filter Imager (SuFI) onboard the Sunrise balloon-borne solar observatory. Small MBPs in the internetwork are automatically tracked. The trajectory of each MBP is then calculated and described by a diffusion index (γ) and a diffusion coefficient (D). We also explore the distribution of the diffusion indices with the help of a Monte Carlo simulation.
Results: We find γ = 1.69 ± 0.08 and D = 257 ± 32 km2 s-1 averaged over all MBPs. Trajectories of most MBPs are classified as super-diffusive, i.e. γ > 1, with the determined γ being the largest obtained so far to our knowledge. A direct correlation between D and timescale (τ) determined from trajectories of all MBPs is also obtained. We discuss a simple scenario to explain the diffusivity of the observed, relatively short-lived MBPs while they migrate within a small area in a supergranule (i.e. an internetwork area). We show that the scatter in the γ values obtained for individual MBPs is due to their limited lifetimes.
Conclusions: The super-diffusive MBPs can be described as random walkers (due to granular evolution and intergranular turbulence) superposed on a large systematic (background) velocity, caused by granular, mesogranular, and supergranular flows. Title: Magnetic structure of an activated filament in a flaring active region Authors: Sasso, C.; Lagg, A.; Solanki, S. K. Bibcode: 2014A&A...561A..98S Altcode: 2013arXiv1312.2781S
Aims: While the magnetic field in quiescent prominences has been widely investigated, less is known about the field in activated prominences. We report observational results on the magnetic field structure of an activated filament in a flaring active region. In particular, we studied its magnetic structure and line-of-sight flows during its early activated phase, shortly before it displayed signs of rotation.
Methods: We inverted the Stokes profiles of the chromospheric He i 10 830 Å triplet and the photospheric Si i 10 827 Å line observed in this filament by the Vacuum Tower Telescope on Tenerife. Using these inversion results, we present and interpret the first maps of the velocity and magnetic field obtained in an activated filament, both in the photosphere and the chromosphere.
Results: Up to five different magnetic components are found in the chromospheric layers of the filament, while outside the filament a single component is sufficient to reproduce the observations. Magnetic components displaying an upflow are preferentially located towards the centre of the filament, while the downflows are concentrated along its periphery. Moreover, the upflowing gas is associated with an opposite-polarity magnetic configuration with respect to the photosphere, while the downflowing gas is associated with a same-polarity configuration.
Conclusions: The activated filament has a very complex structure. Nonetheless, it is compatible with a flux rope, albeit a distorted one, in the normal configuration. The observations are best explained by a rising flux rope in which part of the filament material is still stably stored (upflowing material, rising with the field), while the rest is no longer stably stored and flows down along the field lines.

The movie is available in electronic form at http://www.aanda.org Title: Analysis of magnetic fields in a plage region using a spatially coupled 2D inversion technique Authors: Buehler, David; Lagg, Andreas; Solanki, Sami K.; Van Noort, Michiel Bibcode: 2014cosp...40E.427B Altcode: The properties of magnetic features (MFCs) within a plage region in the vicinity of a sunspot were investigated at high spatial resolution. Stokes spectra of the 630nm line pair recorded by the spectropolarimeter aboard Hinode were inverted using an extended version of the SPINOR code. The code preformed a spatially coupled inversion of the Stokes spectra using three log(tau) nodes in optical depth. No magnetic filling factors was employed. The analysis of the inversion results reveals that the MFCs have typical field strengths of 1500G at log(tau)=-0.9 and inclinations between 10-15 degrees in all three log(tau) nodes. The MFCs expand by forming magnetic canopies composed of weaker and more inclined magnetic fields. The expansion of the magnetic field and temperature stratification of MFCs with optical depth is in good agreement with a thin flux tube model. Whilst the gas inside magnetic flux concentrations is typically at rest, the majority of MFCs were surrounded by a ring of downflows with an average value of 2.5km/s at log(tau)=0. The ring gradually shifts outwards following the expansion of the MFC. Within the downflow rings of MFCs small magnetic patches of opposite polarity to that of the main MFC were identified, which are predominantly situated beneath the canopy of its main MFC. We found evidence for a strong broadening of the Stokes profiles within MFCs and their surrounding downflow rings (expressed by a microturbulence in the inversion). This indicates the presence of strong unresolved velocities. Title: Peripheral downflows in sunspot penumbrae Authors: van Noort, M.; Lagg, A.; Tiwari, S. K.; Solanki, S. K. Bibcode: 2013A&A...557A..24V Altcode: 2013arXiv1308.0466V Context. Sunspot penumbrae show high-velocity patches along the periphery.
Aims: The high-velocity downflow patches are believed to be the return channels of the Evershed flow. We aim to investigate their structure in detail using Hinode SOT/SP observations.
Methods: We employ Fourier interpolation in combination with spatially coupled height dependent LTE inversions of Stokes profiles to produce high-resolution, height-dependent maps of atmospheric parameters of these downflows and investigate their properties.
Results: High-speed downflows are observed over a wide range of viewing angles. They have supersonic line-of-sight velocities, some in excess of 20 km s-1, and very high magnetic field strengths, reaching values of over 7 kG. A relation between the downflow velocities and the magnetic field strength is found, in good agreement with MHD simulations.
Conclusions: The coupled inversion at high resolution allows for the accurate determination of small-scale structures. The recovered atmospheric structure indicates that regions with very high downflow velocities contain some of the strongest magnetic fields that have ever been measured on the Sun.

Two movies are available in electronic form at http://www.aanda.org Title: Structure of sunspot penumbral filaments: a remarkable uniformity of properties Authors: Tiwari, Sanjiv Kumar; van Noort, Michiel; Lagg, Andreas; Solanki, Sami K. Bibcode: 2013A&A...557A..25T Altcode: 2013arXiv1307.3668T Context. The sunspot penumbra comprises numerous thin, radially elongated filaments that are central for heat transport within the penumbra, but whose structure is still not clear.
Aims: We aim to investigate the fine-scale structure of these penumbral filaments.
Methods: We perform a depth-dependent inversion of spectropolarimetric data of a sunspot very close to solar disk center obtained by Solar Optical Telescope/Spectropolarimeter onboard the Hinode spacecraft. We have used a recently developed, spatially coupled 2D inversion scheme, which allows us to analyze the fine structure of individual penumbral filaments up to the diffraction limit of the telescope.
Results: Filaments of different sizes in all parts of the penumbra display very similar magnetic field strengths, inclinations, and velocity patterns. The temperature structure is also similar, although the filaments in the inner penumbra have cooler tails than those in the outer penumbra. The similarities allowed us to average all these filaments and to subsequently extract the physical properties common to all of them. This average filament shows upflows associated with an upward-pointing field at its inner, umbral end (head) and along its axis, as well as downflows along the lateral edge and strong downflows in the outer end (tail) associated with a nearly vertical, strong, and downward-pointing field. The upflowing plasma is significantly, i.e., up to 800 K, hotter than the downflowing plasma. The hot, tear-shaped head of the averaged filament can be associated with a penumbral grain. The central part of the filament shows nearly horizontal fields with strengths in the range of 1 kG. The field above the filament converges, whereas a diverging trend is seen in the deepest layers near the head of the filament. The fluctuations in the physical parameters along and across the filament increase rapidly with depth.
Conclusions: We put forward a unified observational picture of a sunspot penumbral filament. It is consistent with such a filament being a magneto-convective cell, in line with recent magnetohydrodynamic simulations. The uniformity of its properties over the penumbra sets constraints on penumbral models and simulations. The complex and inhomogeneous structure of the filament provides a natural explanation for a number of long-running controversies in the literature. Title: Quiet Sun magnetic fields observed by Hinode: Support for a local dynamo Authors: Buehler, D.; Lagg, A.; Solanki, S. K. Bibcode: 2013A&A...555A..33B Altcode: 2013arXiv1307.0789B Context. The Hinode mission has revealed copious amounts of horizontal flux covering the quiet Sun. Local dynamo action has been proposed to explain the presence of this flux.
Aims: We sought to test whether the quiet Sun flux detected by Hinode is due to a local or the global dynamo by studying long-term variations in the polarisation signals detectable at the disc centre of the quiet Sun between November 2006 and May 2012, with particular emphasis on weak signals in the internetwork.
Methods: The investigation focusses on line-integrated circular polarisation Vtot and linear polarisation LPtot profiles obtained from the Fe I 6302.5 Å absorption line in Hinode SOT/SP.
Results: Both circular and linear polarisation signals show no overall variation in the fraction of selected pixels from 2006 until 2012. There is also no variation in the magnetic flux in this interval of time. The probability density functions (PDF) of the line-of-sight magnetic flux can be fitted with a power law from 1.17 × 1017 Mx to 8.53 × 1018 Mx with index α = -1.82 ± 0.02 in 2007. The variation of α's across all years does not exceed a significance of 1σ. Linearly polarised features are also fitted with a power law, with index α = -2.60 ± 0.06 in 2007. Indices derived from linear polarisation PDFs of other years also show no significant variation.
Conclusions: Our results show that the ubiquitous horizontal polarisation on the edges of bright granules seen by Hinode are invariant during the minimum of cycle 23. This supports the notion that the weak circular and linear polarisation is primarily caused by an independent local dynamo. Title: Chromospheric magnetic field of an active region filament using the He I triplet and the primary observation of filaments (prominences) using New Vacuum Solar Tower of China Authors: Xu, Zhi; Lagg, A.; Solanki, S.; Liu, Z.; New Vacuum Solar Telescope Observers Bibcode: 2013SPD....4410504X Altcode: There are two parts in my presentation. In the first part I present the magnetic field measurement of an active region filament using the full Stokes profiles of He I 10830 and Si I 10827 band when the filament in its stable phase. This observation was fulfilled using German Vacuum Tower Telescope (VTT). The vector magnetic field and Doppler velocity map both in the photosphere and chromosphere were observed and analyzed co-temporally and co-spatially. The observation findings reveal that we were observing the emergence of a flux rope with a subsequent formation of a filament. In the second part, I would like to exhibit another ground-based observation facility, 1m New Vacuum Solar Telescope (NVST) located in Fu-Xian Lake Solar Observatory of China. After the basic introduction including the location and instrumentations, I give some high lights including granulation, faculae, micro-flares, jets, and filaments or prominence since the first running in 2010, showing our potential ability to do high-resolution solar observation from the ground. Observation proposals from the international solar community are well appreciated in future. Title: Structure and dynamics of isolated internetwork Ca II H bright points observed by SUNRISE Authors: Jafarzadeh, S.; Solanki, S. K.; Feller, A.; Lagg, A.; Pietarila, A.; Danilovic, S.; Riethmüller, T. L.; Martínez Pillet, V. Bibcode: 2013A&A...549A.116J Altcode: 2012arXiv1211.4836J
Aims: We aim to improve our picture of the low chromosphere in the quiet-Sun internetwork by investigating the intensity, horizontal velocity, size and lifetime variations of small bright points (BPs; diameter smaller than 0.3 arcsec) observed in the Ca II H 3968 Å passband along with their magnetic field parameters, derived from photospheric magnetograms.
Methods: Several high-quality time series of disc-centre, quiet-Sun observations from the Sunrise balloon-borne solar telescope, with spatial resolution of around 100 km on the solar surface, have been analysed to study the dynamics of BPs observed in the Ca II H passband and their dependence on the photospheric vector magnetogram signal.
Results: Parameters such as horizontal velocity, diameter, intensity and lifetime histograms of the isolated internetwork and magnetic Ca II H BPs were determined. Mean values were found to be 2.2 km s-1, 0.2 arcsec (≈150 km), 1.48 ⟨ ICa ⟩ and 673 s, respectively. Interestingly, the brightness and the horizontal velocity of BPs are anti-correlated. Large excursions (pulses) in horizontal velocity, up to 15 km s-1, are present in the trajectories of most BPs. These could excite kink waves travelling into the chromosphere and possibly the corona, which we estimate to carry an energy flux of 310 W m-2, sufficient to heat the upper layers, although only marginally.
Conclusions: The stable observing conditions of Sunrise and our technique for identifying and tracking BPs have allowed us to determine reliable parameters of these features in the internetwork. Thus we find, e.g., that they are considerably longer lived than previously thought. The large velocities are also reliable, and may excite kink waves. Although these wave are (marginally) energetic enough to heat the quiet corona, we expect a large additional contribution from larger magnetic elements populating the network and partly also the internetwork. Title: The GREGOR Solar Telescope on Tenerife Authors: Schmidt, W.; von der Lühe, O.; Volkmer, R.; Denker, C.; Solanki, S. K.; Balthasar, H.; Bello González, N.; Berkefeld, T.; Collados Vera, M.; Hofmann, A.; Kneer, F.; Lagg, A.; Puschmann, K. G.; Schmidt, D.; Sobotka, M.; Soltau, D.; Strassmeier, K. G. Bibcode: 2012ASPC..463..365S Altcode: 2012arXiv1202.4289S 2011 was a successful year for the GREGOR project. The telescope was finally completed in May with the installation of the 1.5-meter primary mirror. The installation of the first-light focal plane instruments was completed by the end of the year. At the same time, the preparations for the installation of the high-order adaptive optics were finished, its integration to the telescope is scheduled for early 2012. This paper describes the telescope and its instrumentation in their present first-light configuration, and provides a brief overview of the science goals of GREGOR. Title: The GREGOR Solar Telescope Authors: Denker, C.; Lagg, A.; Puschmann, K. G.; Schmidt, D.; Schmidt, W.; Sobotka, M.; Soltau, D.; Strassmeier, K. G.; Volkmer, R.; von der Luehe, O.; Solanki, S. K.; Balthasar, H.; Bello Gonzalez, N.; Berkefeld, T.; Collados Vera, M.; Hofmann, A.; Kneer, F. Bibcode: 2012IAUSS...6E.203D Altcode: The 1.5-meter GREGOR solar telescope is a new facility for high-resolution observations of the Sun. The telescope is located at the Spanish Observatorio del Teide on Tenerife. The telescope incorporates advanced designs for a foldable-tent dome, an open steel-truss telescope structure, and active and passive means to minimize telescope and mirror seeing. Solar fine structure can be observed with a dedicated suite of instruments: a broad-band imaging system, the "GREGOR Fabry-Perot Interferometer", and the "Grating Infrared Spectrograph". All post-focus instruments benefit from a high-order (multi-conjugate) adaptive optics system, which enables observations close to the diffraction limit of the telescope. The inclusion of a spectrograph for stellar activity studies and the search for solar twins expands the scientific usage of the GREGOR to the nighttime domain. We report on the successful commissioning of the telescope until the end of 2011 and the first steps towards science verification in 2012. Title: A retrospective of the GREGOR solar telescope in scientific literature Authors: Denker, C.; von der Lühe, O.; Feller, A.; Arlt, K.; Balthasar, H.; Bauer, S. -M.; Bello González, N.; Berkefeld, Th.; Caligari, P.; Collados, M.; Fischer, A.; Granzer, T.; Hahn, T.; Halbgewachs, C.; Heidecke, F.; Hofmann, A.; Kentischer, T.; Klva{ňa, M.; Kneer, F.; Lagg, A.; Nicklas, H.; Popow, E.; Puschmann, K. G.; Rendtel, J.; Schmidt, D.; Schmidt, W.; Sobotka, M.; Solanki, S. K.; Soltau, D.; Staude, J.; Strassmeier, K. G.; Volkmer, R.; Waldmann, T.; Wiehr, E.; Wittmann, A. D.; Woche, M. Bibcode: 2012AN....333..810D Altcode: 2012arXiv1210.3167D In this review, we look back upon the literature, which had the GREGOR solar telescope project as its subject including science cases, telescope subsystems, and post-focus instruments. The articles date back to the year 2000, when the initial concepts for a new solar telescope on Tenerife were first presented at scientific meetings. This comprehensive bibliography contains literature until the year 2012, i.e., the final stages of commissioning and science verification. Taking stock of the various publications in peer-reviewed journals and conference proceedings also provides the ``historical'' context for the reference articles in this special issue of Astronomische Nachrichten/Astronomical Notes. Title: The 1.5 meter solar telescope GREGOR Authors: Schmidt, W.; von der Lühe, O.; Volkmer, R.; Denker, C.; Solanki, S. K.; Balthasar, H.; Bello Gonzalez, N.; Berkefeld, Th.; Collados, M.; Fischer, A.; Halbgewachs, C.; Heidecke, F.; Hofmann, A.; Kneer, F.; Lagg, A.; Nicklas, H.; Popow, E.; Puschmann, K. G.; Schmidt, D.; Sigwarth, M.; Sobotka, M.; Soltau, D.; Staude, J.; Strassmeier, K. G.; Waldmann , T. A. Bibcode: 2012AN....333..796S Altcode: The 1.5 m telescope GREGOR opens a new window to the understanding of solar small-scale magnetism. The first light instrumentation includes the Gregor Fabry Pérot Interferometer (GFPI), a filter spectro-polarimeter for the visible wavelength range, the GRating Infrared Spectro-polarimeter (GRIS) and the Broad-Band Imager (BBI). The excellent performance of the first two instruments has already been demonstrated at the Vacuum Tower Telescope. GREGOR is Europe's largest solar telescope and number 3 in the world. Its all-reflective Gregory design provides a large wavelength coverage from the near UV up to at least 5 microns. The field of view has a diameter of 150 arcsec. GREGOR is equipped with a high-order adaptive optics system, with a subaperture size of 10 cm, and a deformable mirror with 256 actuators. The science goals are focused on, but not limited to, solar magnetism. GREGOR allows us to measure the emergence and disappearance of magnetic flux at the solar surface at spatial scales well below 100 km. Thanks to its spectro-polarimetric capabilities, GREGOR will measure the interaction between the plasma flows, different kinds of waves, and the magnetic field. This will foster our understanding of the processes that heat the chromosphere and the outer layers of the solar atmosphere. Observations of the surface magnetic field at very small spatial scales will shed light on the variability of the solar brightness. Title: GRIS: The GREGOR Infrared Spectrograph Authors: Collados, M.; López, R.; Páez, E.; Hernández, E.; Reyes, M.; Calcines, A.; Ballesteros, E.; Díaz, J. J.; Denker, C.; Lagg, A.; Schlichenmaier, R.; Schmidt, W.; Solanki, S. K.; Strassmeier, K. G.; von der Lühe, O.; Volkmer, R. Bibcode: 2012AN....333..872C Altcode: This paper describes the main characteristics of GRIS (GREGOR Infrared Spectrograph), the grating spectrograph installed in the recently inaugurated (May 2012) 1.5-meter GREGOR telescope located at the Observatorio del Teide in Tenerife. The spectrograph has a standard Czerny-Turner configuration with parabolic collimator and camera mirrors that belong to the same conic surface. Although nothing prevents its use at visible wavelengths, the spectrograph will be initially used in combination with the infrared detector of the Tenerife Infrared Polarimeter (TIP-II) in standard spectroscopic mode as well as for spectropolarimetric measurements. Title: Chromospheric magnetic fields of an active region filament Authors: Xu, Z.; Solanki, S.; Lagg, A. Bibcode: 2012EAS....55..163X Altcode: Vector magnetic fields of an active region filament are co-spatially and co-temporally mapped in photosphere and upper chromosphere, by using spectro-polarimetric observations made by Tenerife Infrared Polarimeter (TIP II) at the German Vacuum Tower Telescope (VTT). A Zeeman-based ME inversion is performed on the full Stokes vectors of both the photospheric Si I 1082.7 nm and the chromospheric He I 1083.0 nm lines. We found that the strong magnetic fields, with the field strength of 600 - 800 G in the He I line formation height, are not uncommon among AR filaments. But such strong magnetic field is not always found in AR filaments. Title: First Results from the SUNRISE Mission Authors: Solanki, S. K.; Barthol, P.; Danilovic, S.; Feller, A.; Gandorfer, A.; Hirzberger, J.; Jafarzadeh, S.; Lagg, A.; Riethmüller, T. L.; Schüssler, M.; Wiegelmann, T.; Bonet, J. A.; González, M. J. M.; Pillet, V. M.; Khomenko, E.; Yelles Chaouche, L.; Iniesta, J. C. d. T.; Domingo, V.; Palacios, J.; Knölker, M.; González, N. B.; Borrero, J. M.; Berkefeld, T.; Franz, M.; Roth, M.; Schmidt, W.; Steiner, O.; Title, A. M. Bibcode: 2012ASPC..455..143S Altcode: The SUNRISE balloon-borne solar observatory consists of a 1m aperture Gregory telescope, a UV filter imager, an imaging vector polarimeter, an image stabilization system, and further infrastructure. The first science flight of SUNRISE yielded high-quality data that reveal the structure, dynamics, and evolution of solar convection, oscillations, and magnetic fields at a resolution of around 100 km in the quiet Sun. Here we describe very briefly the mission and the first results obtained from the SUNRISE data, which include a number of discoveries. Title: Solar magnetism eXplorer (SolmeX). Exploring the magnetic field in the upper atmosphere of our closest star Authors: Peter, Hardi; Abbo, L.; Andretta, V.; Auchère, F.; Bemporad, A.; Berrilli, F.; Bommier, V.; Braukhane, A.; Casini, R.; Curdt, W.; Davila, J.; Dittus, H.; Fineschi, S.; Fludra, A.; Gandorfer, A.; Griffin, D.; Inhester, B.; Lagg, A.; Landi Degl'Innocenti, E.; Maiwald, V.; Sainz, R. Manso; Martínez Pillet, V; Matthews, S.; Moses, D.; Parenti, S.; Pietarila, A.; Quantius, D.; Raouafi, N. -E.; Raymond, J.; Rochus, P.; Romberg, O.; Schlotterer, M.; Schühle, U.; Solanki, S.; Spadaro, D.; Teriaca, L.; Tomczyk, S.; Trujillo Bueno, J.; Vial, J. -C. Bibcode: 2012ExA....33..271P Altcode: 2011arXiv1108.5304P; 2011ExA...tmp..134P The magnetic field plays a pivotal role in many fields of Astrophysics. This is especially true for the physics of the solar atmosphere. Measuring the magnetic field in the upper solar atmosphere is crucial to understand the nature of the underlying physical processes that drive the violent dynamics of the solar corona—that can also affect life on Earth. SolmeX, a fully equipped solar space observatory for remote-sensing observations, will provide the first comprehensive measurements of the strength and direction of the magnetic field in the upper solar atmosphere. The mission consists of two spacecraft, one carrying the instruments, and another one in formation flight at a distance of about 200 m carrying the occulter to provide an artificial total solar eclipse. This will ensure high-quality coronagraphic observations above the solar limb. SolmeX integrates two spectro-polarimetric coronagraphs for off-limb observations, one in the EUV and one in the IR, and three instruments for observations on the disk. The latter comprises one imaging polarimeter in the EUV for coronal studies, a spectro-polarimeter in the EUV to investigate the low corona, and an imaging spectro-polarimeter in the UV for chromospheric studies. SOHO and other existing missions have investigated the emission of the upper atmosphere in detail (not considering polarization), and as this will be the case also for missions planned for the near future. Therefore it is timely that SolmeX provides the final piece of the observational quest by measuring the magnetic field in the upper atmosphere through polarimetric observations. Title: Magnetic Fields of an Active Region Filament from Full Stokes Analysis of Si I 1082.7 nm and He I 1083.0 nm Authors: Xu, Z.; Lagg, A.; Solanki, S.; Liu, Y. Bibcode: 2012ApJ...749..138X Altcode: 2012arXiv1202.4562X Vector magnetic fields of an active region filament in the photosphere and upper chromosphere are obtained from spectro-polarimetric observations recorded with the Tenerife Infrared Polarimeter (TIP II) at the German Vacuum Tower Telescope. We apply Milne-Eddington inversions on full Stokes vectors of the photospheric Si I 1082.7 nm and the upper chromospheric He I triplet at 1083.0 nm to obtain the magnetic field vector and velocity maps in two atmosphere layers. We find that (1) a complete filament was already present in Hα at the beginning of the TIP II data acquisition. Only a partially formed one, composed of multiple small threads, was present in He I. (2) The AR filament comprises two sections. One shows strong magnetic field intensities, about 600-800 G in the upper chromosphere and 800-1000 G in the photosphere. The other exhibits only comparatively weak magnetic field strengths in both layers. (3) The Stokes V signal is indicative of a dip in the magnetic field strength close to the chromospheric PIL. (4) In the chromosphere, consistent upflows are found along the PIL flanked by downflows. (5) The transversal magnetic field is nearly parallel to the PIL in the photosphere and inclined by 20°-30° in the chromosphere. (6) The chromospheric magnetic field around the filament is found to be in normal configuration, while the photospheric field presents a concave magnetic topology. The observations are consistent with the emergence of a flux rope with a subsequent formation of a filament. 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: Diffusivity of Isolated Internetwork Ca II H Bright Points Observed by SuFI/SUNRISE Authors: Jafarzadeh, S.; Solanki, S. K.; Cameron, R. H.; Feller, A.; Pietarila, A.; Lagg, A.; Barthol, P.; Berkefeld, T.; Gandorfer, A.; Knoelker, M.; Martinez Pillet, V.; Schmidt, W.; Title, A. Bibcode: 2012decs.confE..99J Altcode: We analyze trajectories of the proper motion of intrinsically magnetic, isolated internetwork Ca II H BPs (with mean lifetime of 461 sec) to obtain their diffusivity behaviors. We use high spatial and temporal resolution image sequences of quiet-Sun, disc-centre observations obtained in the Ca II H 397 nm passband of the Sunrise Filter Imager (SuFI) on board the SUNRISE balloon-borne solar observatory. In order to avoid misidentification, the BPs are semi-manually selected and then automatically tracked. The trajectory of each BP is then calculated and its diffusion index is described by a power law exponent, using which we classify the BPs' trajectories into sub-, normal and super- diffusive. In addition, the corresponding diffusion coefficients (D) based on the observed displacements are consequently computed. We find a strong super-diffusivity at a height sampled by the SuFI/SUNRISE Ca II H passband (i.e. a height corresponding roughly to the temperature minimum). We find that 74% of the identified tiny BPs are super-diffusive, 18% move randomly (i.e. their motion corresponds to normal diffusion) and only 8% belong to the sub-diffusion regime. In addition, we find that 53% of the super-diffusion regime (i.e. 39% of all BPs) have the diffusivity index of 2 which are termed as "Ballistic BPs". Finally, we explore the distribution of diffusion index with the help of a simple simulation. The results suggest that the BPs are random walkers superposed by a systematic (background) velocity in which the magnitude of each component (and hence their ratio) depends on the time and spatial scales. We further discuss a simple sketch to explain the diffusivity of observed BPs while they migrate within a supergranule (i.e. internetwork areas) or close to the network regions. Title: Siphon flow in a cool magnetic loop Authors: Bethge, C.; Beck, C.; Peter, H.; Lagg, A. Bibcode: 2012A&A...537A.130B Altcode: 2011arXiv1111.5564B Context. Siphon flows that are driven by a gas pressure difference between two photospheric footpoints of different magnetic field strength connected by magnetic field lines are a well-studied phenomenon in theory, but observational evidence is scarce. Aims. We investigate the properties of a structure in the solar chromosphere in an active region to find out whether the feature is consistent with a siphon flow in a magnetic loop filled with chromospheric material.

Methods. We derived the line-of-sight (LOS) velocity of several photospheric spectral lines and two chromospheric spectral lines, Ca II H 3968.5 *Aring; and He I 10830 Å, in spectropolarimetric observations of NOAA 10978 done with the Tenerife Infrared Polarimeter (TIP-II) and the POlarimetric LIttrow Spectrograph (POLIS). The structure can be clearly traced in the LOS velocity maps and the absorption depth of He I. The magnetic field configuration in the photosphere is inferred directly from the observed Stokes parameters and from inversions with the HELIX+ code. Data from the full-disk Chromospheric Telescope (ChroTel) in He I in intensity and LOS velocity are used for tracking the temporal evolution of the flow, along with TRACE Fe IX/X 171 Å data for additional information about coronal regions related to the structure under investigation.

Results. The inner end of the structure is located in the penumbra of a sunspot. It shows downflows whose strength decreases with decreasing height in the atmosphere. The flow velocity in He I falls abruptly from above 40 km s-1 to about zero further into the penumbra. A slight increase of emission is seen in the Ca II H spectra at the endpoint. At the outer end of the structure, the photospheric lines that form higher up in the atmosphere show upflows that accelerate with height. The polarization signal near the outer end shows a polarity opposite to that of the sunspot, the magnetic field strength of 580 G is roughly half as large as at the inner end. The structure exists for about 90 min. Its appearance is preceeded by a brightening in its middle in the coronal TRACE data.

Conclusions. The observed flows match theoretical predictions of chromospheric and coronal siphon flows, with accelerating upflowing plasma at one footpoint with low field strength and decelerating downflowing plasma at the other end. A tube shock at the inner end is probable, but the evidence is not conclusive. The TRACE data suggest that the structure forms because of a reorganization of field lines after a reconnection event. Title: Variation of quiet Sun magnetic elements between 2006 and 2011 using Hinode SOT/SP Authors: Buehler, D.; Lagg, A.; Solanki, S. K. Bibcode: 2011sdmi.confE..76B Altcode: The Hinode satellite has revealed copious amounts of horizontal flux covering the quiet Sun, nurturing the notion of local dynamo action operating close to the solar surface. We sought to investigate the variation in the occurrence as well as the strength of circular and linear polarisation on the quiet Sun during the minimum of cycle 23, covering a period from November 2006 until August 2011. This investigation used Hinode SOT/SP images of the disk centre and a large FOV and focussed on line-integrated linear and circular polarisation signals obtained from the Fe I 6302.5 Å absorption line. The circular polarisation showed an overall linear decline in occurrence from November 2006 until August 2011. By comparing PDFs we found that this decline is associated in particular with network elements. The internetwork on the other hand showed a 10% decrease in occurrence from November 2010 until June 2009, followed by an equal increase until August 2011. The investigation also revealed a reduction of 30% in the occurrence of linear polarisation signals between November 2006 and December 2009. From August 2010 until August 2011 the occurrence of linear polarisation was increasing again. Hence, our results show that the occurrence of the ubiquitous linear polarisation of the internetwork as seen by Hinode is measurably influenced by the solar cycle. This implies that an independent local dynamo process is unlikely to be the sole cause responsible for the generation of this magnetic flux. Title: The Sun at high resolution: first results from the Sunrise mission Authors: Solanki, S. K.; Barthol, P.; Danilovic, S.; Feller, A.; Gandorfer, A.; Hirzberger, J.; Lagg, A.; Riethmüller, T. L.; Schüssler, M.; Wiegelmann, T.; Bonet, J. A.; Pillet, V. Martínez; Khomenko, E.; del Toro Iniesta, J. C.; Domingo, V.; Palacios, J.; Knölker, M.; González, N. Bello; Borrero, J. M.; Berkefeld, T.; Franz, M.; Roth, M.; Schmidt, W.; Steiner, O.; Title, A. M. Bibcode: 2011IAUS..273..226S Altcode: The Sunrise balloon-borne solar observatory consists of a 1m aperture Gregory telescope, a UV filter imager, an imaging vector polarimeter, an image stabilization system and further infrastructure. The first science flight of Sunrise yielded high-quality data that reveal the structure, dynamics and evolution of solar convection, oscillations and magnetic fields at a resolution of around 100 km in the quiet Sun. Here we describe very briefly the mission and the first results obtained from the Sunrise data, which include a number of discoveries. Title: The height of chromospheric loops in an emerging flux region Authors: Merenda, L.; Lagg, A.; Solanki, S. K. Bibcode: 2011A&A...532A..63M Altcode: 2012arXiv1202.1113M Context. The chromospheric layer observable with the He i 10 830 Å triplet is strongly warped. The analysis of the magnetic morphology of this layer therefore requires a reliable technique to determine the height at which the He i absorption takes place.
Aims: The He i absorption signature connecting two pores of opposite polarity in an emerging flux region is investigated. This signature is suggestive of a loop system connecting the two pores. We aim to show that limits can be set on the height of this chromospheric loop system.
Methods: The increasing anisotropy in the illumination of a thin, magnetic structure intensifies the linear polarization signal observed in the He i triplet with height. This signal is altered by the Hanle effect. We apply an inversion technique incorporating the joint action of the Hanle and Zeeman effects, with the absorption layer height being one of the free parameters.
Results: The observed linear polarization signal can be explained only if the loop apex is higher than ≈ 5 Mm. Best agreement with the observations is achieved for a height of 6.3 Mm.
Conclusions: The strength of the linear polarization signal in the loop apex is inconsistent with the assumption of a He i absorption layer at a constant height level. The determined height supports the earlier conclusion that dark He 10 830 Å filaments in emerging flux regions trace emerging loops. Title: Polarimetry with GREGOR Authors: Balthasar, H.; Bello González, N.; Collados, M.; Denker, C.; Feller, A.; Hofmann, A.; Lagg, A.; Nagaruju, L.; Puschmann, K. G.; Soltau, D.; Volkmer, R. Bibcode: 2011ASPC..437..351B Altcode: A brief description of the new 1.5-meter solar telescope GREGOR located at the Observatorio del Teide in Tenerife will be given. GREGOR will provide a spatial resolution of about 75 km on the Sun, and with its light collecting capability we will be able to study the development of small magnetic features with high cadence. From the beginning, it will be equipped with the GREGOR Fabry-Pérot Interferometer (GFPI) for the visible spectral range and with a GRating Infrared Spectrograph (GRIS). Both postfocus instruments can be combined with a polarimeter, and in both cases the light is modulated by two ferro-electric liquid crystals. A calibration unit can be inserted to determine the instrumental polarization. Because of the altazimuthal mount, time-dependent rotation of the polarimetric reference plane is introduced, and we have to develop a polarization model of the telescope. Measurements to verify this model are in preparation. Title: Intensity contrast from MHD simulations and HINODE observations Authors: Afram, N.; Unruh, Y. C.; Solanki, S. K.; Schüssler, M.; Lagg, A.; Vögler, A. Bibcode: 2011A&A...526A.120A Altcode: 2010arXiv1011.6102A Context. Changes in the solar surface area, which is covered by small-scale magnetic elements, are thought to cause long-term changes in the solar spectral irradiance, which are important for determining the impact on Earth's climate.
Aims: To study the effect of small-scale magnetic elements on the total and spectral irradiance, we derive their contrasts from 3-D MHD simulations of the solar atmosphere. These calculations are necessary because measurements of small-scale flux tube contrasts are confined to a few wavelengths and affected by scattered light and instrument defocus, even for space observations.
Methods: To test the contrast calculations, we compare rms contrasts from simulations with those obtained with the broad-band filter imager mounted on the Solar Optical Telescope (SOT) onboard the Hinode satellite and also analyse centre-to-limb variations (CLV). The 3-D MHD simulations include the interaction between convection and magnetic flux tubes. They are performed by assuming non-grey radiative transfer and using the MURaM code. The simulations have an average vertical magnetic field of 0 G, 50 G, and 200 G. Emergent intensities are calculated with the spectral synthesis code ATLAS9 and are convolved with a theoretical point-spread function to account for the properties of the observations' optical system.
Results: We find reasonable agreement between simulated and observed intensity distributions in the visible continuum bands. Agreement is poorer for the CN and G-bands. The analysis of the simulations uncovers a potentially more realistic centre-to-limb behaviour than calculations based on 1-D model atmospheres.
Conclusions: We conclude that starting from 3-D MHD simulations represents a powerful approach to obtaining intensity contrasts for a wide wavelength coverage and different positions across on the solar disk. This also paves the way for future calculations of facular and network contrast as a function of magnetic fluxes. Title: Multicomponent He I 10 830 Å profiles in an active filament Authors: Sasso, C.; Lagg, A.; Solanki, S. K. Bibcode: 2011A&A...526A..42S Altcode: 2011arXiv1101.5563S
Aims: We present new spectropolarimetric observations of the chromospheric He i 10 830 Å multiplet observed in a filament during its phase of activity.
Methods: The data were recorded with the new Tenerife Infrared Polarimeter (TIP-II) at the German Vacuum Tower Telescope (VTT) on 2005 May 18. We inverted the He Stokes profiles using multiple atmospheric components.
Results: The observed He Stokes profiles display a remarkably wide variety of shapes. Most of the profiles show very broad Stokes I absorptions and complex and spatially variable Stokes V signatures. The inversion of the profiles shows evidence of different atmospheric blue- and redshifted components of the He i lines within the resolution element (~1 arcsec), with supersonic velocities of up to ~100 km s-1. Up to five different atmospheric components are found in the same profile. We show that even these complex profiles can be reliably inverted. Title: Fully Resolved Quiet-Sun Magnetic flux Tube Observed with the SUNRISE/IMAX Instrument Authors: Lagg, A.; Solanki, S. K.; Riethmüller, T. L.; Martínez Pillet, V.; Schüssler, M.; Hirzberger, J.; Feller, A.; Borrero, J. M.; Schmidt, W.; del Toro Iniesta, J. C.; Bonet, J. A.; Barthol, P.; Berkefeld, T.; Domingo, V.; Gandorfer, A.; Knölker, M.; Title, A. M. Bibcode: 2010ApJ...723L.164L Altcode: 2010arXiv1009.0996L Until today, the small size of magnetic elements in quiet-Sun areas has required the application of indirect methods, such as the line-ratio technique or multi-component inversions, to infer their physical properties. A consistent match to the observed Stokes profiles could only be obtained by introducing a magnetic filling factor that specifies the fraction of the observed pixel filled with magnetic field. Here, we investigate the properties of a small magnetic patch in the quiet Sun observed with the IMaX magnetograph on board the balloon-borne telescope SUNRISE with unprecedented spatial resolution and low instrumental stray light. We apply an inversion technique based on the numerical solution of the radiative transfer equation to retrieve the temperature stratification and the field strength in the magnetic patch. The observations can be well reproduced with a one-component, fully magnetized atmosphere with a field strength exceeding 1 kG and a significantly enhanced temperature in the mid to upper photosphere with respect to its surroundings, consistent with semi-empirical flux tube models for plage regions. We therefore conclude that, within the framework of a simple atmospheric model, the IMaX measurements resolve the observed quiet-Sun flux tube. Title: Magnetic structures of an emerging flux region in the solar photosphere and chromosphere Authors: Xu, Z.; Lagg, A.; Solanki, S. K. Bibcode: 2010A&A...520A..77X Altcode:
Aims: We investigate the vector magnetic field and Doppler velocity in the photosphere and upper chromosphere of a young emerging flux region of the sun close to disk center.
Methods: Spectropolarimetric scans of a young active region made using the second generation Tenerife Infrared Polarimeter (TIP II) on the German Vacuum Tower Telescope (VTT) are analyzed. The scanned area contained multiple sunspots and an emerging flux region. An inversion based on the Milne-Eddington approximation was performed on the full Stokes vector of the chromospheric He I 10 830 Å and the photospheric Si I 10 827.1 Å lines. This provided the magnetic vector and line-of-sight velocity at each spatial point in both atmospheric layers.
Results: A clear difference is seen between the complex magnetic structure of the emerging flux region (EFR) in the photosphere and the much simpler structure in the upper chromosphere. The upper chromospheric structure is consistent with a set of emerging loops following elongated dark structures seen in the He I 10 830 Å triplet, similar to arch filament systems (AFS), while in the photosphere we infer the presence of U-loops within the emergence zone. Nonetheless, in general the upper chromospheric field has a similar linear relationship between inclination angle and field strength as the photospheric field: the field is weak (≈300 G) and horizontal in the emergence zone, but strong (up to 850 G) and more vertical near its edges. The field strength decreases from the photosphere to the upper chromosphere by approximately 0.1-0.2 G km-1 (or even less) within the emergence zone and by 0.3-0.6 G km-1 in sunspots located at its edge. We reconstructed the magnetic field in 3D based on the chromospheric vector field under the assumption that the He I 10 830 Å triplet forms along the magnetic field loops. The reconstructed loops are quite flat with supersonic downflows at both footpoints. Arguments and evidence for an enhanced formation height of He I 10 830 Å in arch-filaments seen in this line are provided, which support the validity of the reconstructed loops.
Conclusions: The main chromospheric properties of EFRs previously deduced for a single region NOAA 9451 are shown to be valid for another region as well, suggesting that the main original results may have a wider application. The main exception is that only the first region displayed a current sheet in the chromosphere. We propose a scenario in which the relatively complex photospheric structure evolves into the simpler chromospheric one. Title: GREGOR telescope: start of commissioning Authors: Volkmer, R.; von der Lühe, O.; Denker, C.; Solanki, S.; Balthasar, H.; Berkefeld, T.; Caligari, P.; Collados, M.; Halbgewachs, C.; Heidecke, F.; Hofmann, A.; Klvana, M.; Kneer, F.; Lagg, A.; Popow, E.; Schmidt, D.; Schmidt, W.; Sobotka, M.; Soltau, D.; Strassmeier, K. Bibcode: 2010SPIE.7733E..0KV Altcode: 2010SPIE.7733E..18V With the integration of a 1-meter Cesic primary mirror the GREGOR telescope pre-commissioning started. This is the first time, that the entire light path has seen sunlight. The pre-commissioning period includes testing of the main optics, adaptive optics, cooling system, and pointing system. This time was also used to install a near-infrared grating spectro-polarimeter and a 2D-spectropolarimeter for the visible range as first-light science instruments. As soon as the final 1.5 meter primary mirror is installed, commissioning will be completed, and an extended phase of science verification will follow. In the near future, GREGOR will be equipped with a multi-conjugate adaptive optics system that is presently under development at KIS. Title: GREGOR solar telescope: Design and status Authors: Volkmer, R.; von der Lühe, O.; Denker, C.; Solanki, S. K.; Balthasar, H.; Berkefeld, T.; Caligari, P.; Collados, M.; Fischer, A.; Halbgewachs, C.; Heidecke, F.; Hofmann, A.; Klvaňa, M.; Kneer, F.; Lagg, A.; Popow, E.; Schmidt, D.; Schmidt, W.; Sobotka, M.; Soltau, D.; Strassmeier, K. G. Bibcode: 2010AN....331..624V Altcode: The integration and verification phase of the GREGOR telescope reached an important milestone with the installation of the interim 1 m SolarLite primary mirror. This was the first time that the entire light path had seen sunlight. Since then extensive testing of the telescope and its subsystems has been carried out. The integration and verification phase will culminate with the delivery and installation of the final 1.5 m Zerodur primary mirror in the summer of 2010. Observatory level tests and science verification will commence in the second half of 2010 and in 2011. This phase includes testing of the main optics, adaptive optics, cooling and pointing systems. In addition, assuming the viewpoint of a typical user, various observational modes of the GREGOR Fabry-Pérot Interferometer (GFPI), the Grating Infrared Spectrograph (GRIS), and high-speed camera systems will be tested to evaluate if they match the expectations and science requirements. This ensures that GREGOR will provide high-quality observations with its combination of (multi-conjugate) adaptive optics and advanced post-focus instruments. Routine observations are expected for 2012. Title: The calibration of the Cassini-Huygens CAPS Electron Spectrometer Authors: Lewis, G. R.; Arridge, C. S.; Linder, D. R.; Gilbert, L. K.; Kataria, D. O.; Coates, A. J.; Persoon, A.; Collinson, G. A.; André, N.; Schippers, P.; Wahlund, J.; Morooka, M.; Jones, G. H.; Rymer, A. M.; Young, D. T.; Mitchell, D. G.; Lagg, A.; Livi, S. A. Bibcode: 2010P&SS...58..427L Altcode: We present the two-stage method used to calibrate the electron spectrometer (ELS), part of the plasma spectrometer (CAPS) on board the Cassini spacecraft currently in orbit around Saturn. The CAPS-ELS is a top-hat electrostatic analyser designed to measure electron fluxes between 0.5 eV and 26 keV. The on-ground calibration method described here includes the production of photoelectrons, which are energised and passed into the CAPS-ELS in a purpose designed calibration facility. Knowledge of the intensity of these incident electrons and the subsequent instrument output provides an on-ground calibrated geometric factor. Comparative studies of physical quantities such as plasma density and electron differential flux calculated using on-ground calibration factor with the quantities deduced from the wave experiment and high energy electron detector provide in-flight calibration. The results of this are presented together with a comparison of the experimentally calibrated values with simulated calibration values. Title: Nonlinear force-free modelling: influence of inaccuracies in the measured magnetic vector Authors: Wiegelmann, T.; Yelles Chaouche, L.; Solanki, S. K.; Lagg, A. Bibcode: 2010A&A...511A...4W Altcode: 2009arXiv0912.3002W Context. Solar magnetic fields are regularly extrapolated into the corona starting from photospheric magnetic measurements that can be affected by significant uncertainty.
Aims: We study how inaccuracies introduced into the maps of the photospheric magnetic vector by the inversion of ideal and noisy Stokes parameters influence the extrapolation of nonlinear force-free magnetic fields.
Methods: We compute nonlinear force-free magnetic fields based on simulated vector magnetograms, by the inversion of Stokes profiles that were computed by a 3-D radiation MHD simulation snapshot. These extrapolations are compared with extrapolations that originate directly in the field in the MHD simulations, which is our reference. We investigate how line formation and instrumental effects such as noise, limited spatial resolution, and the effect of employing a filter instrument influence the resulting magnetic field structure. The comparison is performed qualitatively by visually inspecting the magnetic field distribution and quantitatively by different metrics.
Results: The reconstructed field is most accurate if ideal Stokes data are inverted and becomes less accurate if instrumental effects and noise are included. The results demonstrate that the nonlinear force-free field extrapolation method tested here is relatively insensitive to the effects of noise in measured polarization spectra at levels consistent with present-day instruments.
Conclusions: Our results show that we can reconstruct the coronal magnetic field as a nonlinear force-free field from realistic photospheric measurements with an accuracy of a few percent, at least in the absence of sunspots. Title: Temperatures of small scale magnetic structures in deep solar photospheric layers Authors: Oklay, Nilda; Gandorfer, Achim; Lagg, Andreas; Solanki, Sami K.; Bianda, Michele; Ramelli, Renzo Bibcode: 2010cosp...38.2857O Altcode: 2010cosp.meet.2857O With current solar instrumentation, small scale magnetic structures still remain unresolved. Nevertheless, it is possible to retrieve information about these unresolved magnetic structures via spectropolarimetry. For this reason, IRSOL (Istituto Ricerche Solari Locarno) facility is used to obtain simultaneously recorded spectra of Stokes I and Stokes V/I of CI (5380.3 A), FeI (5379.6 A, 5383.4 A) and TiII (5381.0 A) lines on an active region using the ZIMPOL II (Zurich Imaging Polarimeter II) instrument. We used Stokes V amplitude ratios technique to investigate temperatures of unresolved magnetic features down to deep photospheric layers. Atmospheric parameters are obtained from the inversions done with the SPINOR code (Stokes-Profile-INversion-O-Routines). Then the results are compared with the results from the realistic MHD simulations obtained from MURaM code (MPS/University of Chicago radiative MHD). Comparisons of the results from observations, inversions and numerical simulations show a good agreement, which confirms the usage of this technique as a temperature diagnostic tool. Title: How do inaccuracies and unresolved structures in the measured solar photospheric magnetic vector influence the accuracy of coronal magnetic field models? Authors: Wiegelmann, Thomas; Yelles, Lotfi; Solanki, Sami; Lagg, Andreas Bibcode: 2010cosp...38.2827W Altcode: 2010cosp.meet.2827W Solar magnetic fields are usually extrapolated into the corona starting from photospheric mag-netic measurements that can suffer from significant uncertainties caused by the presence of unresolved fine structures due to a limited spatial resolution and by the limited polarimet-ric accuracy and spectral resolution. We investigate how these inaccuracies in the measured photospheric magnetic field vector influence the accuracy of the extrapolated coronal mag-netic field. We compare non-linear force-free coronal magnetic field extrapolations from a 3-D radiation MHD simulation snapshot with corresponding extrapolations from synthetic vector magnetograms. The synthetic magnetograms contain instrumental effects such as noise, limited spatial and spectral resolution and the effect of employing a filter instrument. The parameters are chosen in particular to mimic the effects of the Hinode/SOT and the future Solar Orbiter PHI instruments, respectively. We discuss, how photospheric structures, which are inherent in the MHD snapshot, but not resolved in the photospheric magnetic field measurements, influence the quality of the computed coronal magnetic field model. Title: Relation between the Sunrise photospheric magnetic field and the Ca II H bright features Authors: Jafarzadeh, Shahin; Hirzberger, J.; Feller, A.; Lagg, A.; Solanki, S. K.; Pietarila, A.; Danilovic, S.; Riethmueller, T.; Barthol, P.; Berkefeld, T.; Gandorfer, A.; Knülker, M.; Martínez Pillet, V.; Schmidt, W.; Schüssler, M.; Title, A. Bibcode: 2010cosp...38.2856J Altcode: 2010cosp.meet.2856J Recent observations from the Sunrise balloon-borne solar telescope have enabled us to reach an unprecedented high spatial resolution on the solar surface with the near-ultraviolet photo-spheric and chromospheric images as well as the magnetograms. We use these high resolution observations to investigate the structure of the solar upper photosphere and lower chromosphere as well as their temporal evolutions. We study the relation between the inter-granular Ca II 397 nm bright structures in images obtained by the Sunrise Filter Imager (SuFI) and their corresponding photospheric vector magnetic field computed from the Imaging Magnetogram eXperiment (IMaX) observations. The targets under study are in a quiet Sun region and close to disc-centre. Title: Energetic particles in Saturn's magnetosphere during the Cassini nominal mission (July 2004-July 2008) Authors: Krupp, N.; Roussos, E.; Lagg, A.; Woch, J.; Müller, A. L.; Krimigis, S. M.; Mitchell, D. G.; Roelof, E. C.; Paranicas, C.; Carbary, J.; Jones, G. H.; Hamilton, D. C.; Livi, S.; Armstrong, T. P.; Dougherty, M. K.; Sergis, N. Bibcode: 2009P&SS...57.1754K Altcode: In July 2004 the Cassini spacecraft began its orbital tour in the Saturnian system and performed 74 orbits during the nominal mission (July 2004-July 2008) providing data from nearly all local times at various distances and latitudes relative to the planet. The particles and field instruments onboard the spacecraft were essentially operating continuously offering the possibility to study the global configuration and the dynamics of the second largest magnetosphere in our solar system extensively. One of those instruments aboard Cassini is the Low Energy Magnetospheric Measurement System (LEMMS), one of three particle detectors of the Magnetospheric Imaging Instrument (MIMI). MIMI/LEMMS measures the intensity, energy spectra and pitch angle distributions of energetic ions (E>30keV) and electrons (E>20keV) separately. The measured energetic particle distributions together with the measured magnetic field provide a very powerful tool to investigate the Saturnian magnetosphere in those regions covered by the Cassini orbits. This paper will give an overview of the energetic particle measurements of the MIMI/LEMMS sensor in the Saturnian system. In the first part of the paper synoptic maps will be shown where all the data are presented as a function of various trajectory parameters of the spacecraft. Secondly bi-directional electron distributions along the magnetic field direction will be described as a feature in the Saturnian system. Thirdly the particle parameters in the inner magnetosphere with absorption signatures of the various moons are presented. Fourthly it will be shown that the region around about 15 RS seems to be a characteristic region where depletion signatures in energetic particle distributions are very often observed. At the end of this work a 60 min intensity periodicity in the MIMI/LEMMS data is discussed. Title: Simulation of a flux emergence event and comparison with observations by Hinode Authors: Yelles Chaouche, L.; Cheung, M. C. M.; Solanki, S. K.; Schüssler, M.; Lagg, A. Bibcode: 2009A&A...507L..53Y Altcode: 2009arXiv0910.5737Y Aims: We study the observational signature of flux emergence in the photosphere using synthetic data from a 3D MHD simulation of the emergence of a twisted flux tube.
Methods: Several stages in the emergence process are considered. At every stage we compute synthetic Stokes spectra of the two iron lines Fe I 6301.5 Å and Fe I 6302.5 Å and degrade the data to the spatial and spectral resolution of Hinode's SOT/SP. Then, following observational practice, we apply Milne-Eddington-type inversions to the synthetic spectra in order to retrieve various atmospheric parameters and compare the results with recent Hinode observations.
Results: During the emergence sequence, the spectral lines sample different parts of the rising flux tube, revealing its twisted structure. The horizontal component of the magnetic field retrieved from the simulations is close to the observed values. The flattening of the flux tube in the photosphere is caused by radiative cooling, which slows down the ascent of the tube to the upper solar atmosphere. Consistent with the observations, the rising magnetized plasma produces a blue shift of the spectral lines during a large part of the emergence sequence.

Figure 3 is only available in electronic form at http://www.aanda.org Title: Internetwork Horizontal Magnetic Fields in the Quiet Sun Chromosphere: Results from a Joint Hinode/VTT Study Authors: Lagg, A.; Ishikawa, R.; Merenda, L.; Wiegelmann, T.; Tsuneta, S.; Solanki, S. K. Bibcode: 2009ASPC..415..327L Altcode: We present results from a joint Hinode/VTT campaign (May 2008). Spectropolarimetric data of a quiet Sun super-granular network cell at a heliocentric angle of 28° in the He I 10830 Å line were analyzed using an inversion code incorporating Hanle and Zeeman effects (HeLIx^+) to retrieve magnetic field strength and direction in the upper chromosphere. Simultaneously recorded Hinode SOT/SP data reveal the photospheric magnetic field morphology, clearly showing magnetic flux concentrations in the internetwork. The photospheric magnetic field maps are used to feed potential field extrapolations similar to the work by Schrijver & Title (2003). The extrapolated magnetic field structure is compared with the magnetic field configuration resulting from the He 10830 inversions. These inversions also reveal horizontal magnetic structures extending over a length of up to 20 Mm above the internetwork, indicative of the presence of a magnetic canopy. The photospheric magnetic flux concentrations in the internetwork are obviously not sufficiently strong to prevent the formation of a canopy at chromospheric heights. Title: High-resolution spectro-polarimetry of a flaring sunspot penumbra Authors: Hirzberger, J.; Riethmüller, T.; Lagg, A.; Solanki, S. K.; Kobel, P. Bibcode: 2009A&A...505..771H Altcode: 2009arXiv0908.3803H We present simultaneous photospheric and chromospheric observations of the trailing sunspot in NOAA 10904 during a weak flare eruption (GOES magnitude B7.8), obtained with the Swedish Solar Telescope (SST) in La Palma, Canary Islands. High-resolution Ca II H images show a typical two-ribbon structure that has been hitherto only known for larger flares, and the flare appears in a confined region that is discernible by a bright border. The underlying photosphere shows a disturbed penumbral structure with intersecting branches of penumbral filaments. High-resolution Doppler- and vector-magnetograms exhibit oppositely directed Evershed flows and magnetic field vectors in the individual penumbral branches, resulting in several regions of magnetic azimuth discontinuity and several islands where the vertical magnetic field is reversed. The discontinuity regions are co-spatial with the locations of the onset of the flare ribbons. From the results, we conclude that the confined flare region is detached from the global magnetic field structure by a separatrix marked by the bright border visible in C II H. We further conclude that the islands of reversed vertical field appear because of flux emergence and that the strong magnetic shear appearing in the regions of magnetic azimuth discontinuity triggers the flare.

Movies are only available in electronic form at http://www.aanda.org Title: Full Magnetic Field Vector of an Emerging Flux Region Authors: Xu, Z.; Lagg, A.; Solanki, S. K. Bibcode: 2009ASPC..405..223X Altcode: We present maps of the full magnetic field vector of an emerging flux region in both the photosphere and chromosphere. The magnetic and velocity structure of freshly emerged loops is determined. Title: A summary of observational records on periodicities above the rotational period in the Jovian magnetosphere Authors: Kronberg, E. A.; Woch, J.; Krupp, N.; Lagg, A. Bibcode: 2009AnGeo..27.2565K Altcode: The Jovian magnetosphere is a very dynamic system. The plasma mass-loading from the moon Io and the fast planetary rotation lead to regular release of mass from the Jovian magnetosphere and to a change of the magnetic topology. These regular variations, most commonly on several (2.5-4) days scale, were derived from various data sets obtained by different spacecraft missions and instruments ranging from auroral images to in situ measurements of magnetospheric particles. Specifically, ion measurements from the Galileo spacecraft represent the periodicities, very distinctively, namely the periodic thinning of the plasma sheet and subsequent dipolarization, and explosive mass release occurring mainly during the transition between these two phases. We present a review of these periodicities, particularly concentrating on those observed in energetic particle data. The most distinct periodicities are observed for ions of sulfur and oxygen. The periodic topological change of the Jovian magnetosphere, the associated mass-release process and auroral signatures can be interpreted as a global magnetospheric instability with analogies to the two step concept of terrestrial substorms. Different views on the triggering mechanism of this magnetospheric instability are discussed. Title: The Three-Dimensional Structure of Magnetic Fields and Electric Currents in an Active Region Authors: Deng, Na; Choudhary, D.; Lagg, A.; Jing, J.; Wang, H. Bibcode: 2009SPD....40.0904D Altcode: Active Region NOAA 9661 consisting of various magnetic features (alpha spot, delta spot, pores, and plages) was observed simultaneously in three spectral lines (FeI 630.25, 630.15, and MgI 517.27) using full Stokes spectro-polarimetry with Advanced Stokes Polarimeter at NSO/SP. The formation heights of the three spectral lines span from photosphere to the low chromosphere. The magnetic field vectors are inverted from Stokes parameters using advanced inversion codes. In particular, HeLIx code is used to invert MgI's observation because it is dedicated for chromospheric Stokes inversion. The inverted magnetic field vectors in multiple atmospheric layers enable us to derive the three dimensional structure of the magnetic fields, electric current densities, current helicities, and their height gradients.

Acknowledgments:

This work is supported by NASA under grants NNX08AQ32G and NNX08AQ89G, and by NSF under grants ATM 05-48952 and ATM 07-16950. Title: Coupling from the Photosphere to the Chromosphere and the Corona Authors: Wedemeyer-Böhm, S.; Lagg, A.; Nordlund, Å. Bibcode: 2009SSRv..144..317W Altcode: 2008SSRv..tmp..171W; 2008arXiv0809.0987W The atmosphere of the Sun is characterized by a complex interplay of competing physical processes: convection, radiation, conduction, and magnetic fields. The most obvious imprint of the solar convection and its overshooting in the low atmosphere is the granulation pattern. Beside this dominating scale there is a more or less smooth distribution of spatial scales, both towards smaller and larger scales, making the Sun essentially a multi-scale object. Convection and overshooting give the photosphere its face but also act as drivers for the layers above, namely the chromosphere and corona. The magnetic field configuration effectively couples the atmospheric layers on a multitude of spatial scales, for instance in the form of loops that are anchored in the convection zone and continue through the atmosphere up into the chromosphere and corona. The magnetic field is also an important structuring agent for the small, granulation-size scales, although (hydrodynamic) shock waves also play an important role—especially in the internetwork atmosphere where mostly weak fields prevail. Based on recent results from observations and numerical simulations, we attempt to present a comprehensive picture of the atmosphere of the quiet Sun as a highly intermittent and dynamic system. Title: Zeeman Broadening in Cool Stars Authors: Anderson, Richard I.; Reiners, Ansgar; Solanki, Sami K.; Lagg, Andreas Bibcode: 2009AIPC.1094..708A Altcode: 2009csss...15..708A We investigate detectability of magnetic fields by Zeeman broadening of well-isolated spectral lines in F, G and K type stars. Data of unprecedented quality were taken with CES1 mounted on the 3.6 m ESO telescope at La Silla, Chile, in three campaigns in the optical range between 5770 Å and 6280 Å, each with a wavelength coverage of roughly 40 Å. We use the SPINOR/STOPRO (cf. Frutiger et al. [1]) package developed by ETH2 and MPS3 to perform spectral line inversion via χ2 minimization. Starting from constraints given by previous measurements of stellar parameters, we fit a number of extracted spectral lines. Eventually, our goal is to determine the product of the magnetic field strength B and the surface filling factor, B×f.

Our work is in progress and thus no final measurements can be presented at this stage. Title: Coupling from the Photosphere to the Chromosphere and the Corona Authors: Wedemeyer-Böhm, S.; Lagg, A.; Nordlund, Å. Bibcode: 2009odsm.book..317W Altcode: The atmosphere of the Sun is characterized by a complex interplay of competing physical processes: convection, radiation, conduction, and magnetic fields. The most obvious imprint of the solar convection and its overshooting in the low atmosphere is the granulation pattern. Beside this dominating scale there is a more or less smooth distribution of spatial scales, both towards smaller and larger scales, making the Sun essentially a multi-scale object. Convection and overshooting give the photosphere its face but also act as drivers for the layers above, namely the chromosphere and corona. The magnetic field configuration effectively couples the atmospheric layers on a multitude of spatial scales, for instance in the form of loops that are anchored in the convection zone and continue through the atmosphere up into the chromosphere and corona. The magnetic field is also an important structuring agent for the small, granulation-size scales, although (hydrodynamic) shock waves also play an important role—especially in the internetwork atmosphere where mostly weak fields prevail. Based on recent results from observations and numerical simulations, we attempt to present a comprehensive picture of the atmosphere of the quiet Sun as a highly intermittent and dynamic system. Title: CRISP Spectropolarimetric Imaging of Penumbral Fine Structure Authors: Scharmer, G. B.; Narayan, G.; Hillberg, T.; de la Cruz Rodriguez, J.; Löfdahl, M. G.; Kiselman, D.; Sütterlin, P.; van Noort, M.; Lagg, A. Bibcode: 2008ApJ...689L..69S Altcode: 2008arXiv0806.1638S We discuss penumbral fine structure in a small part of a pore, observed with the CRISP imaging spectropolarimeter at the Swedish 1-m Solar Telescope (SST), close to its diffraction limit of 0.16''. Milne-Eddington inversions applied to these Stokes data reveal large variations of field strength and inclination angle over dark-cored penumbral intrusions and a dark-cored light bridge. The mid-outer part of this penumbra structure shows ~0.3'' wide spines, separated by ~1.6'' (1200 km) and associated with 30° inclination variations. Between these spines, there are no small-scale magnetic structures that easily can be identified with individual flux tubes. A structure with nearly 10° more vertical and weaker magnetic field is seen midway between two spines. This structure is cospatial with the brightest penumbral filament, possibly indicating the location of a convective upflow from below. Title: Mass release process in the Jovian magnetosphere: Statistics on particle burst parameters Authors: Kronberg, E. A.; Woch, J.; Krupp, N.; Lagg, A. Bibcode: 2008JGRA..11310202K Altcode: The Jovian magnetosphere undergoes periodic reconfiguration processes mainly driven by the fast planetary rotation and mass loading from the moon Io. These reconfiguration processes of the Jovian magnetosphere are associated with the release of plasmoids discernible as ion flow bursts associated with bipolar magnetic signatures. We investigate these plasma flows statistically using data from the Energetic Particles Detector and from the magnetometer on board Galileo. The plasma flows are observed in different magnetospheric regions: the current sheet center, the plasma sheet boundary layers, and the lobe. We show that the bulk velocity of all species is the same for most of the magnetic field bipolar signatures associated with these plasma flows. The average speed of the observed plasmoids in the plasma sheet associated with the ion flow bursts is between 350 and 500 km s-1, and the duration of the events is between 10 and 20 min. The associated plasmoid length is correspondingly ∼9 RJ. The plasmoids are moving approximately with Alfvénic speed. The convection electric field during the plasmoid release is about an order of magnitude higher than the ambient value of the Jovian convection electric field. Title: Loop Morphology and Flows and their Relation to the Magnetic Field Authors: Teriaca, L.; Wiegelmann, T.; Lagg, A.; Solanki, S. K.; Curdt, W.; Sekii, T. Bibcode: 2008ASPC..397..196T Altcode: In November 2006 we obtained several rasters of a large sunspot and its trailing region using the SUMER spectrometer on SOHO. The observations consist of spectroheliograms in the continuum around 142 nm and in several spectral lines formed between 80000 K and 0.6 MK, covering the temperature range from the chromosphere to the lower corona. The observed profiles provide LOS velocity and Doppler width maps. TRACE images in the EUV passbands and in the 160 nm continuum provide a clear picture of the coronal loops and the chromosphere near their footpoints. The same target was also observed by all the instruments aboard Hinode and, in particular, by the SOT spectro-polarimeter measuring the photospheric magnetic vector. We combined SOT and MDI data (covering a larger FOV) to infer the coronal magnetic field of the active region by a nonlinear force-free field extrapolation. The observed radiance and velocity patterns at the various heights/temperatures throughout the solar atmosphere are compared with the field topology. Title: The Magnetic Vector Structure of an Active Region Plage Field Authors: Meling, M. H. M.; Lagg, A.; Solanki, S. K. Bibcode: 2008ESPM...12.2.58M Altcode: We present scans of the active region plage associated with NOAA 10953, recorded with the Tenerife Infrared Polarimeter 2 (TIP-2) mounted behind the German Vacuum Tower Telescope (VTT) on Tenerife and the SOT-SP instrument on-board the HINODE spacecraft. TIP-2 recorded the full Stokes vector close to the diffraction limit of the telescope over a 20 angstroem wavelength range containing six magnetically sensitive FeI lines in the infrared including the g=3 line FeI 15648.5. With these lines we use the advantage that the Zeeman splitting dominates over the Doppler broadening for kG fields. The iron lines used by HINODE are FeI 6301.501and FeI 6302.494.

We analyzed the data by applying a Milne-Eddington type inversion to it. In the context of a two-component model we found a bimodal distribution of field strengths, strong fields whose field strength distribution peaks at 1400 [G] and a weak field distribution, which may be associated with quiet sun regions bordering on the plage. Title: SST/CRISP Magnetometry with Fe I 630.2 nm Authors: Narayan, G.; Scharmer, G. B.; Hillberg, T.; Lofdahl, M.; van Noort, M.; Sutterlin, P.; Lagg, A. Bibcode: 2008ESPM...122.120N Altcode: We present recent full Stokes observations in the Fe I 630.2 nm line with CRISP, an imaging spectropolarimeter at the Swedish 1-m Solar Telescope (SST). The observations reach a spatial resolution of 0".16, close to the diffraction limit of the SST, representing a major improvement over any past ground based or space based spectropolarimetric data. We describe the data acquisition and reduction methods and present results of Milne-Eddington(ME) inversions applied on observations of plage. Title: Magnetic Structure of a Filament during its Phase of Activity Authors: Sasso, C.; Lagg, A.; Solanki, S. K. Bibcode: 2008ESPM...12.2.19S Altcode: We analyze and interpret spectropolarimetric observations of an active region filament located close to the solar disc center, during its phase of activity. The observations are obtained in the chromospheric He I lines at 1083.0 nm. We provide novel observational results on the magnetic field measurements in solar filaments to give constraints to the theoretical models of their support in the solar corona. Our main goal is to interpret the behavior of the atmospheric parameters retrieved from the spectropolarimetric data to give a picture of the magnetic structure of the observed filament. The analysis of the observed polarization of the He I 1083.0 nm multiplet in the filament, carried out by inverting the Stokes profiles, reveals the presence of different unresolved atmospheric components of the He lines, coexisting within the resolution element (1.2 arcsec). The different components, belonging to different magnetic field lines, show supersonic up- and downflows, sometimes within the same resolution element. The He blueshifted components belong to mostly transversal field lines in the body of the filament. These field lines are found to be curving upwards on both sides. This picture suggests the presence of dipped field lines that are moving upward, carrying with them the filament material. During this movement, we also observe filament material flowing down along field lines having the same polarity as the photospheric field (i.e. they have the opposite inclination with respect to the dipped field lines). These downflows are faster at the filament end points and can reach values close to 10 times the speed of sound. The field lines are found to be almost parallel to the filament axis in the plane perpendicular to the line of sight. We use the two main theoretical models of prominence support (dip or flux rope models) to interpret the results obtained. Title: The intensity contrast of solar granulation: comparing Hinode SP results with MHD simulations Authors: Danilovic, S.; Gandorfer, A.; Lagg, A.; Schüssler, M.; Solanki, S. K.; Vögler, A.; Katsukawa, Y.; Tsuneta, S. Bibcode: 2008A&A...484L..17D Altcode: 2008arXiv0804.4230D Context: The contrast of granulation is an important quantity characterizing solar surface convection.
Aims: We compare the intensity contrast at 630 nm, observed using the Spectro-Polarimeter (SP) aboard the Hinode satellite, with the 3D radiative MHD simulations of Vögler & Schüssler (2007, A&A, 465, L43).
Methods: A synthetic image from the simulation is degraded using a theoretical point-spread function of the optical system, and by considering other important effects.
Results: The telescope aperture and the obscuration by the secondary mirror and its attachment spider, reduce the simulated contrast from 14.4% to 8.5%. A slight effective defocus of the instrument brings the simulated contrast down to 7.5%, close to the observed value of 7.0%.
Conclusions: A proper consideration of the effects of the optical system and a slight defocus, lead to sufficient degradation of the synthetic image from the MHD simulation, such that the contrast reaches almost the observed value. The remaining small discrepancy can be ascribed to straylight and slight imperfections of the instrument, which are difficult to model. Hence, Hinode SP data are consistent with a granulation contrast which is predicted by 3D radiation MHD simulations. Title: Multiheight Analysis of Asymmetric Stokes Profiles in a Solar Active Region Authors: Deng, N.; Choudhary, D.; Solanki, S. K.; Lagg, A. Bibcode: 2008AGUSMSP51D..06D Altcode: Parameters characterizing Stokes asymmetries are derived from full Stokes I,Q,U,V spectra of FeI λλ 630.15, 630.25~nm line pair (formed at two different heights in the photosphere) and MgI b 517.27~nm line (formed at lower chromosphere) in a solar active region near disc center. The spectropolarimetric observations were taken with the National Solar Observatory/High Altitude Observatory Advanced Stokes Polarimeter. The observed active region consists of a α sunspot, a δ sunspot, several pores and granulation. The line center shifts and bi-sectors derived from Stokes-I profiles describe the line-of-sight Doppler velocity and Stokes-I asymmetry, respectively. Stokes-V amplitude and area asymmetries are defined by the normalized difference of respective quantities between blue and red lobes of circular polarization profiles. The same can be derived from linear polarization profiles ([Q2+U2]1/2). The Stokes asymmetries are compared for different regions and at multiple heights. Neutral line regions of the δ spot and outer penumbral regions show distinct large Stokes asymmetries. Both Stokes-V amplitude and area asymmetries become larger from lower to higher atmosphere in neutral line regions that have strong transverse field and mixed polarities. The Stokes-V area asymmetry of outer edge of penumbrae changes from positive in the photosphere to negative in lower chromosphere. Detailed results and interpretation will be presented. Title: The nature of running penumbral waves revealed Authors: Bloomfield, D. S.; Lagg, A.; Solanki, S. K. Bibcode: 2008IAUS..247...55B Altcode: 2007IAUS..247...55B We seek to clarify the nature of running penumbral (RP) waves: are they chromospheric trans-sunspot waves or a visual pattern of upward-propagating waves? Full Stokes spectropolarimetric time series of the photospheric Sii10827 Å line and the chromospheric Hei10830 Å multiplet were inverted using a Milne-Eddington code. Spatial pixels were paired between the outer umbral/inner penumbral photosphere and the penumbral chromosphere using inclinations retrieved by the inversion and the dual-height pairings of line-of-sight velocity time series were studied for signatures of wave propagation using a Fourier phase difference analysis. The dispersion relation for radiatively cooling acoustic waves, modified to incorporate an inclined propagation direction, fits well the observed phase differences between the pairs of photospheric and chromospheric pixels. We have thus demonstrated that RP waves are in effect low-β slow-mode waves propagating along the magnetic field. Title: Stratification of Sunspot Umbral Dots from Inversion of Stokes Profiles Recorded by Hinode Authors: Riethmüller, T. L.; Solanki, S. K.; Lagg, A. Bibcode: 2008ApJ...678L.157R Altcode: 2008arXiv0805.4324R This work aims to constrain the physical nature of umbral dots (UDs) using high-resolution spectropolarimetry. Full Stokes spectra recorded by the spectropolarimeter on Hinode of 51 UDs in a sunspot close to the disk center are analyzed. The height dependence of the temperature, magnetic field vector, and line-of-sight velocity across each UD is obtained from an inversion of the Stokes vectors of the two Fe I lines at 630 nm. No difference is found at higher altitudes [-3 <= log (τ500) <= - 2] between the UDs and the diffuse umbral background. Below that level the difference rapidly increases, so that at the continuum formation level [log (τ500) = 0] we find on average a temperature enhancement of 570 K, a magnetic field weakening of 510 G, and upflows of 800 m s-1 for peripheral UDs, whereas central UDs display an excess temperature of on average 550 K, a field weakening of 480 G, and no significant upflows. The results for, in particular, the peripheral UDs, including cuts of magnetic vector and velocity through them, look remarkably similar to the output of recent radiation MHD simulations. They strongly suggest that UDs are produced by convective upwellings. Title: The FeH F4Δ-X4Δ system. Creating a valuable diagnostic tool to explore solar and stellar magnetic fields Authors: Afram, N.; Berdyugina, S. V.; Fluri, D. M.; Solanki, S. K.; Lagg, A. Bibcode: 2008A&A...482..387A Altcode: Context: Lines of diatomic molecules are ideal tools for studying cool stellar atmospheres and the internal structure of sunspots and starspots, given their temperature and pressure sensitivities, which are typically higher than in atomic lines. The Wing-Ford FeH F4Δ-X4Δ system represents such a diatomic molecule that is, in addition, highly sensitive to magnetic fields. The current theoretical description of those transitions that include the involved molecular constants, however, are only based on intensity measurements because polarimetric observations have not been available until now, which limits their diagnostic value. Furthermore, the theory has so far been optimized to reproduce energy levels and line strengths without taking magnetic sensitivities into account.
Aims: The FeH F4Δ-X4Δ system is produced by transitions between two electronic states with the coupling of the angular momenta that is intermediate between limiting Hund's cases (a) and (b). Our goal is to investigate the diagnostic capabilities of the current theoretical description of the molecule FeH.
Methods: Using the most precise available Hamiltonian, we carried out the perturbation calculation of the molecular Zeeman effect for this transition and computed the Landé factors of the energy levels and of transitions. We extracted Landé factors from a comparison of observed and calculated Stokes I and V profiles. Certain spectral lines, most frequently with high magnetic sensitivity, exhibited discrepancies between the theory and observations. We extended the theoretical model with a semi-empirical approach to obtain a diagnostic tool that is able to reproduce many of the interesting spectral lines.
Results: We find that the current theory successfully reproduces the magnetic properties of a large number of lines in the FeH F4Δ-X4Δ system and that the modified Hamiltonian allows us to synthesize and successfully reproduce the most sensitive lines. Thus, our observations have provided valuable constraints for determining empirical molecular constants and Landé factors.
Conclusions: The FeH F4Δ-X4Δ system is found to be a very sensitive magnetic diagnostic tool. Polarimetric data of these lines, in contrast to intensity measurements, provide us with more direct and detailed information to study the coolest parts of sunspot and starspot umbrae, as well as cool active dwarfs. Title: Comparison of periodic substorms at Jupiter and Earth Authors: Kronberg, E. A.; Woch, J.; Krupp, N.; Lagg, A.; Daly, P. W.; Korth, A. Bibcode: 2008JGRA..113.4212K Altcode: The Energetic Particles Detector and magnetometer measurements on Galileo showed that the Jovian magnetosphere undergoes reconfiguration processes which are very similar to the characteristics of a terrestrial substorm. At Jupiter the reconfiguration process occurs quasi-periodically with a repetition period of several days. In the terrestrial magnetosphere periodic substorms have been observed during magnetic storms. The comparison of the periodic magnetospheric disturbances at Jupiter and Earth shows that they are similar in dynamic features as well as in spatial distribution but have different energy sources. In the case of Earth, the well-established energy source is the solar wind. In the case of the Jovian magnetosphere, it is believed that internal energy is supplied by the fast planetary rotation and the moon Io which releases ∼1000 kg s-1 of plasma into the magnetosphere. It is established that the energy accumulation and subsequent release lead to similar features in the magnetospheres of both planets. The particle data show periodic intensity fluctuations and plasma pressure variations. In addition, recurring signatures of stretching and dipolarization are observed in the magnetic field at the terrestrial and Jovian magnetospheres. Furthermore, the release process is associated with an intensification of auroral emissions. The typical phases for terrestrial substorms like growth, expansion and recovery are also found in the periodic substorms at Jupiter. As a lesson taken from the Jovian magnetosphere it is proposed that under certain conditions periodic magnetospheric substorms at Earth can be driven by mass-loading from the plasmasphere. Title: The Dust Halo of Saturn’s Largest Icy Moon, Rhea Authors: Jones, G. H.; Roussos, E.; Krupp, N.; Beckmann, U.; Coates, A. J.; Crary, F.; Dandouras, I.; Dikarev, V.; Dougherty, M. K.; Garnier, P.; Hansen, C. J.; Hendrix, A. R.; Hospodarsky, G. B.; Johnson, R. E.; Kempf, S.; Khurana, K. K.; Krimigis, S. M.; Krüger, H.; Kurth, W. S.; Lagg, A.; McAndrews, H. J.; Mitchell, D. G.; Paranicas, C.; Postberg, F.; Russell, C. T.; Saur, J.; Seiß, M.; Spahn, F.; Srama, R.; Strobel, D. F.; Tokar, R.; Wahlund, J. -E.; Wilson, R. J.; Woch, J.; Young, D. Bibcode: 2008Sci...319.1380J Altcode: Saturn’s moon Rhea had been considered massive enough to retain a thin, externally generated atmosphere capable of locally affecting Saturn’s magnetosphere. The Cassini spacecraft’s in situ observations reveal that energetic electrons are depleted in the moon’s vicinity. The absence of a substantial exosphere implies that Rhea’s magnetospheric interaction region, rather than being exclusively induced by sputtered gas and its products, likely contains solid material that can absorb magnetospheric particles. Combined observations from several instruments suggest that this material is in the form of grains and boulders up to several decimetres in size and orbits Rhea as an equatorial debris disk. Within this disk may reside denser, discrete rings or arcs of material. Title: Energetic electron signatures of Saturn's smaller moons: Evidence of an arc of material at Methone Authors: Roussos, E.; Jones, G. H.; Krupp, N.; Paranicas, C.; Mitchell, D. G.; Krimigis, S. M.; Woch, J.; Lagg, A.; Khurana, K. Bibcode: 2008Icar..193..455R Altcode: We present several energetic charged particle microsignatures of two Lagrange moons, Telesto and Helene, measured by the MIMI/LEMMS instrument. These small moons absorb charged particles but their effects are usually obscured by Tethys and Dione, the two larger saturnian satellites that occupy the same orbits. The scales and structures of these microsignatures are consistent with standard models for electron absorption from asteroid-sized moons in Saturn's radiation belts. In the context of these observations, we also examine the possibility that the 3 km Satellite Methone is responsible for two electron microsignatures detected by Cassini close to this moon's orbit. We infer that a previously undetected arc of material exists at Methone's orbit (R/2006 S5), we speculate how such a structure could form and what its physical characteristics and location could be. The origin of this arc could be linked to a possible presence of a faint ring produced by micrometeoroid impacts on Methone's surface, to E-ring dust clump formation at that distance or to temporary dust clouds produced by enceladian activity that spiral inwards under the effect of non-gravitational forces. Title: The Nature of Running Penumbral Waves Revealed Authors: Bloomfield, D. Shaun; Lagg, Andreas; Solanki, Sami K. Bibcode: 2007ApJ...671.1005B Altcode: 2007arXiv0709.3731B We seek to clarify the nature of running penumbral (RP) waves: are they chromospheric trans-sunspot waves or a visual pattern of upward-propagating waves? Full Stokes spectropolarimetric time series of the photospheric Si I λ10827 line and the chromospheric He I λ10830 multiplet were inverted using a Milne-Eddington atmosphere. Spatial pixels were paired between the outer umbral/inner penumbral photosphere and the penumbral chromosphere using inclinations retrieved by the inversion and the dual-height pairings of line-of-sight velocity time series were studied for signatures of wave propagation using a Fourier phase difference analysis. The dispersion relation for radiatively cooling acoustic waves, modified to incorporate an inclined propagation direction, fits well the observed phase differences between the pairs of photospheric and chromospheric pixels. We have thus demonstrated that RP waves are in effect low-β slow-mode waves propagating along the magnetic field. Title: Rhea's interaction with Saturn's magnetosphere Authors: Jones, G. H.; Roussos, E.; Krupp, N.; Beckmann, U.; Coates, A. J.; Crary, F.; Dandouras, I.; Dikarev, V.; Dougherty, M. K.; Garnier, P.; Hansen, C. J.; Hendrix, A. R.; Hospodarsky, G. B.; Johnson, R. E.; Kempf, S.; Khurana, K.; Krimigis, S. M.; Krueger, H.; Kurth, W. S.; Lagg, A.; McAndrews, H. J.; Mitchell, D. G.; Paranicas, C.; Postberg, F.; Russell, C. T.; Saur, J.; Seiss, M.; Spahn, F.; Srama, R.; Strobel, D. F.; Tokar, R. L.; Wahlund, J.; Wilson, R. J.; Woch, J.; Young, D. Bibcode: 2007AGUFM.P12B..05J Altcode: The instruments aboard the Cassini orbiter continue to provide a wealth of invaluable information on plasma interactions at the icy moons of Saturn. 1528 km-wide Rhea is the largest of Saturn's icy satellites. Here, we present our analysis of data from the two closest flybys of this moon to date, in November 2005 and August 2007. Data from six Cassini instruments are presented; MIMI, CAPS, MAG, RPWS, UVIS, and CDA, covering the plasma, neutral gas, and dust environments of the moon. The complementary information provided by these instruments allows us to draw a picture of this moon's intriguing interaction with Saturn's magnetospheric plasma. We compare the results at Rhea to those obtained at other moons, and we present our arguments for the causes of variations observed in the magnetospheric electron population. Title: Energetic charged particle absorption by Saturn's icy moons: future studies and new applications Authors: Roussos, E.; Krupp, N.; Jones, G. H.; Paranicas, C.; Mitchell, D. G.; Krimigis, S. M.; Motschmann, U.; Lagg, A.; Woch, J. Bibcode: 2007epsc.conf..905R Altcode: Energetic charged particle absorption signatures by Saturn's large icy moons, rings and dust are an excellent tool for the study of the planet's magnetospheric dynamics and dust environment. After the first two years of the Cassini mission, relevant observations with the MIMI/LEMMS energetic electron sensors extended and updated the results from previous studies that used data from experiments on the Pioneer 11 and the Voyager missions. The new results include values for the radial diffusion coefficients and their L-dependence, the observation of the non-axisymmetric structure of the electron drift shells, as well as the detection and the physical characterization of ring arcs at Methone's orbit and the G-ring. Furthermore, these results reveal that the information coded in charged particle absorption signatures is even greater than we could initially imagine: the highly variable lifetimes of electron microsignatures suggest a possible link with equally variable dynamic events, such as injections. The shape of the electron drift shells seems consistent with the effect of magnetospheric compression on the dayside, meaning that information about the magnetopause distance might be hidden in the absorption signature locations. The microsignature locations during high-latitude, close moon flybys, can also reveal the shape of the magnetic field lines and be used to ''calibrate" magnetic field models. Such observations could be crucial for the understanding of the magnetospheric and the space environment of Saturn. Title: Modified p-modes in penumbral filaments? Authors: Bloomfield, D. S.; Solanki, S. K.; Lagg, A.; Borrero, J. M.; Cally, P. S. Bibcode: 2007A&A...469.1155B Altcode: 2007arXiv0705.0481B Aims:The primary objective of this study is to search for and identify wave modes within a sunspot penumbra.
Methods: Infrared spectropolarimetric time series data are inverted using a model comprising two atmospheric components in each spatial pixel. Fourier phase difference analysis is performed on the line-of-sight velocities retrieved from both components to determine time delays between the velocity signals. In addition, the vertical separation between the signals in the two components is calculated from the Stokes velocity response functions.
Results: The inversion yields two atmospheric components, one permeated by a nearly horizontal magnetic field, the other with a less-inclined magnetic field. Time delays between the oscillations in the two components in the frequency range 2.5-4.5 mHz are combined with speeds of atmospheric wave modes to determine wave travel distances. These are compared to expected path lengths obtained from response functions of the observed spectral lines in the different atmospheric components. Fast-mode (i.e., modified p-mode) waves exhibit the best agreement with the observations when propagating toward the sunspot at an angle ~50° to the vertical. Title: Electron microdiffusion in the Saturnian radiation belts: Cassini MIMI/LEMMS observations of energetic electron absorption by the icy moons Authors: Roussos, E.; Jones, G. H.; Krupp, N.; Paranicas, C.; Mitchell, D. G.; Lagg, A.; Woch, J.; Motschmann, U.; Krimigis, S. M.; Dougherty, M. K. Bibcode: 2007JGRA..112.6214R Altcode: 2007JGRA..11206214R Since Saturn orbit insertion (SOI), Cassini has performed numerous crossings of Saturn's inner moons' L shells. The Low-Energy Magnetospheric Measurement System (LEMMS) has detected a large number of microsignatures in its lowest-energy electron channels (20-100 keV) as well as in the MeV energy range. We have catalogued and analyzed more than 70 microsignatures in the LEMMS data from the first 22 Cassini orbits and have correlated their evolution with electron diffusive processes. Our results on the L-dependence of the radial diffusion coefficients, DLL, show that radial microdiffusion driven by magnetic field impulses is the dominant mechanism to account for their refilling. The dependency of DLL from equatorial pitch angles also points toward this mechanism. The large scattering of the DLL values at Tethys and Dione suggest that these field impulses might be related to injections. Our analysis also supports the, inferred from pre-Cassini studies, filtering effect by the icy moons on radially diffusing electrons, which starts at the orbit of Dione, at 6.28 Saturn radii, Rs. This is suggested primarily by the very low radial diffusion speeds and by the characteristics of four microsignatures attributed to the moons Mimas and Epimetheus that all seem to have been formed in energies between 1.6 and 3.5 MeV. Despite the low DLL, diffusing electrons can escape absorption and be transported in the inner magnetosphere due to nonaxisymmetric drift shells, which can be detected even along the orbit of Enceladus. We estimate that a significant contribution to the filtering comes from the core of the E ring. Our results also show that L displacements due to the nonaxisymmetric drift shells are orders of magnitude higher than the icy moon L shell variability due to the nonzero eccentricities and inclinations, and total plasma losses on the moon surfaces should be reevaluated. We also examine the energy dependence of DLL and we present a series of possible explanations for the faster depletion of microsignatures at MeV energies. Using the high-energy resolution PHA channels we assess that this faster depletion could result partly from an increase of DLL with energy. The larger passbands of the high-energy electron detectors could amplify the erosion of the microsignature signal. Title: Energetic ion composition during reconfiguration events in the Jovian magnetotail Authors: Radioti, A.; Woch, J.; Kronberg, E. A.; Krupp, N.; Lagg, A.; Glassmeier, K. -H.; Dougherty, M. K. Bibcode: 2007JGRA..112.6221R Altcode: 2007JGRA..11206221R On the basis of the first 15 orbits of the Galileo spacecraft the composition of the energetic ion population of the Jovian magnetosphere is studied on a global scale. Analyzing data from the energetic particles detector onboard Galileo, we study the relative ion abundance ratios of S/O, S/He, O/He and p/He at various energy/nucleon values. Prominent enhancements of S/O, S/He, and O/He abundance ratios are observed in the predawn sector and are associated with substorm-like events in the Jovian magnetotail. During these reconfiguration events, frequent small-scale variations of the south-north component of the magnetic field are present. Acceleration by such magnetic field variations is examined as a possible mechanism for particle energization in that region. When the timescale of the magnetic field variation is comparable to the particle gyro period, the particle is accelerated by the induced electric field. It is shown that, during the Jovian substorm-like events, the heavier ions are more efficiently energized than the lighter leading to the observed ion abundances. Ion composition measurements in other parts of the magnetosphere have shown quasiperiodic 3-day modulations suggesting that the internally driven processes affect the ion composition in the whole magnetosphere. Title: Observations of Running Waves in a Sunspot Chromosphere Authors: Bloomfield, D. S.; Lagg, A.; Solanki, S. K. Bibcode: 2007ASPC..368..239B Altcode: 2007astro.ph..2056B Spectropolarimetric time series data of the primary spot of active region NOAA 9448 were obtained in the Si I 10827 Å line and the He I 10830 Å multiplet with the Tenerife Infrared Polarimeter. Throughout the time series the spectrograph slit was fixed over a region covering umbra, a light bridge, penumbra, and quiet sun. We present speeds of running penumbral waves in the chromosphere, their relation to both photospheric and chromospheric umbral oscillations, and their dependence on the magnetic field topology. Title: Tenerife Infrared Polarimeter II Authors: Collados, M.; Lagg, A.; Díaz Garcí A, J. J.; Hernández Suárez, E.; López López, R.; Páez Mañá, E.; Solanki, S. K. Bibcode: 2007ASPC..368..611C Altcode: Since May 2005 the Tenerife Infrared Polarimeter II (TIP-II) has been operational at the Vacuum Tower Telescope on Tenerife. The core of the polarimeter is a 1024×1020 pixel infrared camera allowing for high precision measurements of the full Stokes vector with a pixel size of 0.18 arcsec, corresponding to the diffraction limit of the telescope at 1 μm. The polarimeter is able to reach a polarimetric accuracy of a few times 10-4, covering a wavelength range of 1 to 1.8 μm. With an upgrade in July 2006, the slit size has been increased to 77 arcsec allowing most active regions to be covered with a single scan. Here we present the technical details of the polarimeter and the camera. We also show some data illustrating the power of this new instrumentation. Title: A possible intrinsic mechanism for the quasi-periodic dynamics of the Jovian magnetosphere Authors: Kronberg, E. A.; Glassmeier, K. -H.; Woch, J.; Krupp, N.; Lagg, A.; Dougherty, M. K. Bibcode: 2007JGRA..112.5203K Altcode: 2007JGRA..11205203K Most regions of the Jovian magnetosphere covered by the Galileo spacecraft measurements undergo quasi-periodic modulations with a time period of several Earth days. These modulations appear in various field and particle properties. Most prominent are periodically recurring ion flow bursts associated with disturbances in the meridional component of the magnetic field in the Jovian magnetotail or variations of the energy spectral shape of the particle distribution associated with the stretching and dipolarization of the magnetic field. Each individual cycle of these modulations is believed to represent a global reconfiguration of the Jovian magnetosphere. We present a simple conceptual model for these periodic processes assuming (1) ion mass loading from internal plasma sources and (2) fast planetary rotation causing magnetotail field line stretching due to centrifugal forces. This leads to a magnetotail configuration favoring magnetic reconnection. Magnetic reconnection causes plasmoid formation and release as well as dipolarization of field lines connected to the planet. Continued mass loading leads again to a stretching of the tail field lines. Our model shows that the suggested intrinsic mechanism can explain the observed periodicities of several days in Jovian substorm-like processes. Title: Full-Stokes Observations and Analysis of He I 10830 Å in a Flaring Region Authors: Sasso, C.; Lagg, A.; Solanki, S. K.; Aznar Cuadrado, R.; Collados, M. Bibcode: 2007ASPC..368..467S Altcode: We present observations of the full Stokes vector in a flaring region, taken in the chromospheric He I 10830 Å multiplet. The data were recorded with the new Tenerife Infrared Polarimeter (TIP 2) at the German Vacuum Tower Telescope (VTT) during May 2005. The He profiles during the flare are extraordinary, showing extremely broad Stokes I absorption and very complex and spatially variable Stokes V signatures. We give first results on the line-of-sight velocities and the magnetic field vector values in the chromosphere for one observed Stokes profile by applying an inversion code to the He I lines. Title: Dynamics of the Jovian Magnetosphere Authors: Krupp, N.; Vasyliunas, V. M.; Woch, J.; Lagg, A.; Khurana, K. K.; Kivelson, M. G.; Mauk, B. H.; Roelof, E. C.; Williams, D. J.; Krimigis, S. M.; Kurth, W. S.; Frank, L. A.; Patterson, W. R. Bibcode: 2007jupi.book..617K Altcode: No abstract at ADS Title: The Configuration of Jupiter's Magnetosphere Authors: Khurana, K. K.; Kivelson, M. G.; Vasyliunas, V. M.; Krupp, N.; Woch, J.; Lagg, A.; Mauk, B. H.; Kurth, W. S. Bibcode: 2007jupi.book..593K Altcode: No abstract at ADS Title: Supersonic downflows in the vicinity of a growing pore. Evidence of unresolved magnetic fine structure at chromospheric heights Authors: Lagg, A.; Woch, J.; Solanki, S. K.; Krupp, N. Bibcode: 2007A&A...462.1147L Altcode: Aims:The velocity and magnetic fine structure of the chromosphere at the leg of an emerging magnetic loop is investigated at a location of supersonic downflows.
Methods: We analyze a time series of spectropolarimetric data in the He i 1083 nm triplet covering a time interval of ≈70 min. The temporal evolution as well as the topology of the magnetic field in the downflow region are investigated. We apply an inversion technique based on a genetic algorithm using the Milne-Eddington approach. The technique is very reliable and robust in retrieving maps of the velocity and the magnetic field vector for both atmospheric components separately.
Results: We observe redshifts corresponding to a downflow speed of up to 40 km s-1 in the vicinity of a growing pore. These supersonic downflows always coexist with a second atmospheric component almost at rest (slow component) within the same resolution element. The redshifted component is more inclined to the solar normal than the slow component and has a different field strength.
Conclusions: .We interpret this downflow as a consequence of the draining of the rising loops. The different magnetic field orientation of the redshifted and the slow component give rise to two possible interpretations: an uncombed structure of the chromosphere, similar to the differently inclined flux-tubes in the penumbra of a sunspot, or a cloud-like structure containing gas at different velocities in two separate height layers of the solar atmosphere. Title: Recent advances in measuring chromospheric magnetic fields in the He I 10830 Å line Authors: Lagg, A. Bibcode: 2007AdSpR..39.1734L Altcode: During the last decade advances in instrumentation, atomic physics and modeling have greatly improved the access to the chromospheric magnetic field vector. High sensitivity polarimeters like the Tenerife Infrared Polarimeter (TIP2, VTT) or the Spectro-Polarimeter for Infrared and Optical Regions (SPINOR, HAO) lead to reliable Zeeman measurements using the He I 10830 Å triplet. The simultaneously measured Si I 10827 Å line provides additional information on the structure of the underlying photosphere. Theoretical modeling of the Hanle and the Paschen-Back effect helped to significantly improve the analysis of polarization measurements in the He I triplet, allowing to directly visualize the magnetic structure of spicules, polar prominences and active regions. Here, I will summarize the results of chromospheric magnetic field measurements using this interesting triplet obtained in the last couple of years and discuss the great potential it has to further uncover the complex structure of the chromosphere and its coupling to the photosphere. Title: T he Performance Of The SOLO-VIM Instrument: Effects Of Instrumental Noise And Lossy Data Compression Authors: Lagg, A.; Yelles, L.; Hirzberger, J.; Woch, J.; Solanki, S. K. Bibcode: 2007ESASP.641E..69L Altcode: Spectropolarimetric observations in photospheric lines reveal a wealth of information on physical parameters of the solar atmosphere like magnetic field strength and di rection or the line-of sight velocity. These observations require the measurement of the four Stokes parameters at a sample of N wavelength positions around the core of the spectral line, resulting in 4N images for one observation. The Visible light Imager and Magnetograph (VIM) instrument on board Solar Orbiter is capable of performing these measurements. However, the data rate required to transfer all 4N images with the required cadence is well beyond the telemetry limit. Here we use realistic, three-dimensional MHD simulations in order to simulate science data provided by VIM which are then used to test various compression techniques. We conclude that lossy data compression and instrumental noise have similar effects on the output data. Title: S imulations Of Science Data Of The Solo-VIM Instrument Authors: Yelles, L.; Hirzberger, J.; Lagg, A.; Woch, J.; Solanki, S. K.; Vögler, A. Bibcode: 2007ESASP.641E..34Y Altcode: The SolO-VIM instrument will be a two-dimensional full-Stokes spectro-polarimeter which will provide diffraction-limited vector-magnetograms, Dopplergrams, and continuum images of the solar photosphere. The instrument's performance depends on various parameters such as aperture diameter, filter characteristics, spectral- line sampling, and orbital position. Here we compute Stokes profiles in realistic 3D MHD simulations. These synthetic data are then degraded to match the output ex- pected from the VIM instrument, and subsequently inverted using a Milne-Eddington atmosphere. We present parameter studies in order to set up minimum require- ments on limitations of VIM's capabilities. Title: Velocity distribution of chromospheric downflows Authors: Aznar Cuadrado, R.; Solanki, S. K.; Lagg, A. Bibcode: 2007msfa.conf..173A Altcode: Infrared spectropolarimetric observations were obtained with the Tenerife Infrared Polarimeter (TIP) at the German Vacuum Tower Telescope (VTT) of the Spanish observatory of Izana, Tenerife. We present the velocity distributions of a large dataset composed of maps of the Stokes I, Q, U, and V profiles of active and quiet sun regions obtained in the chromospheric He I 1083.0 nm triplet. The line-of-sight velocities were determined by applying a multi-Gaussian fit to the intensity profiles. Single and double component fits were carried out for all datasets. We find that 18.7% of all observed pixels show strong downflows as evidenced by a second line profile component, generally shifted by more than 8 km s-1 relative to the rest wavelegth. The distribution of these strong down-flows displays two distinct populations. The slower one (near sonic and weakly supersonic flows) has line-of-sight velocities up to 17 km s-1 and is associated with moderate to strong magnetic signal (up to √(Q2 + U2 + V2)/Ic = 0.08). Strongly supersonic downflows (reaching up to 60 km s-1) are found at places with weak to moderate magnetic signal, with √(Q2 + U2 + V2)/Ic values mainly between 0.01 and 0.03. Title: Spectropolarimetry in the chromospheric He I 1083.0 nm multiplet Authors: Sasso, C.; Lagg, A.; Solanki, S. K. Bibcode: 2007waas.work...43S Altcode: Spectropolarimetry in the He I 1083.0 nm multiplet has a great potential to obtain information on the magnetic field in the solar upper chromosphere. We apply an inversion technique to infrared spectropolarimetric observations, to retrieve the full magnetic vector and the line-of sight velocity. The observations, obtained with the Tenerife Infrared Polarimeter (TIP) II at the German Vacuum Tower Telescope (VTT), provide maps in the Stokes parameters I, Q, U and V. Title: Modified p-modes in penumbral filaments Authors: Bloomfield, D. S.; Lagg, A.; Solanki, S. K.; Borrero, J. M. Bibcode: 2007msfa.conf..241B Altcode: A time series analysis was performed on velocity signals in a sunspot penumbra to search for possible wave modes. The spectropolarimetric photospheric data obtained by the Tenerife Infrared Polarimeter were inverted using the SPINOR code. An atmospheric model comprising two magnetic components and one stray-light component gave an optimal fit to the data. Fourier phase difference analysis between line-of-sight velocities of both magnetic components provided time delays between the two atmospheres. These delays were combined with the speeds of atmospheric wave modes and compared to height separations derived from velocity response functions to determine the wave mode. Title: Nonlinear Force-Free Magnetic Field Modelling For VIM On SO Authors: Wiegelmann, T.; Solanki, S. K.; Yelles, L.; Lagg, A. Bibcode: 2007ESASP.641E..19W Altcode: The aim of this work is to investigate how photon noise and errors in the retrieval of solar magnetic parameters from measured Stokes profiles influences the extrapolartion of nonlinear force-free coronal magnetic fields from photospheric vector magnetograms. To do so we use a nonlinear force-free extrapolation code based on an optimization principle. The extrapolation methods has been extensively tested and applied to data from various telescopes. Here we apply the code artificial vector magnetograms obtained from 3-D radiation-MHD simulations. As a reference case we compute the coronal magnetic field from an ideal magnetogram and compare the result with more realistic magnetograms based on simulated Solar Orbiter/VIM-measurements. We investigate the effect of noise, ambiguities, spatial resolution, inversion mechanism, of Stokes profiles etc. We rate the quality of the reconstructed coronal magnetic field qualitatively by magnetic field line plots and quantitatively by a number of comparison metrices, e.g., the vector correlation with the exact solution and how accurate the free magnetic energy is computed. Not surprisingly, the instrument effects and noise influence the quality of the nonlinear force-free coronal magnetic field model. The extrapolations from realistic vector magnetograms show a reasonable agreement with the ideal reconstruction, however, and are in particular significantly better than extrapolations based on line-of-sight magnetograms only. High quality VIM data will thus allow reasonably accurate extrapolations that can serve as the basis for magnetic coupling science through a comparison with observations from EUS and EUI. Title: Molecular Diagnostics of the Internal Structure of Starspots and Sunspots Authors: Afram, N.; Berdyugina, S. V.; Fluri, D. M.; Solanki, S. K.; Lagg, A.; Petit, P.; Arnaud, J. Bibcode: 2006ASPC..358..375A Altcode: We have analyzed the usefulness of molecules as a diagnostic tool for studying solar and stellar magnetism with the molecular Zeeman and Paschen-Back effects. In the first part we concentrate on molecules that are observed in sunspots such as MgH and TiO. We present calculated molecular line profiles obtained by assuming magnetic fields of 2-3 kG and compare these synthetic Stokes profiles with spectro-polarimetric observations in sunspots. The good agreement between the theory and observations allows us to turn our attention in the second part to starspots to gain insight into their internal structure. We investigate the temperature range in which the selected molecules can serve as indicators for magnetic fields on highly active cool stars and compare synthetic Stokes profiles with our recent observations. Title: Measuring the Magnetic Vector with the He I 10830 Å Line: A Rich New World Authors: Solanki, S. K.; Lagg, A.; Aznar Cuadrado, R.; Orozco Suárez, D.; Collados, M.; Wiegelmann, T.; Woch, J.; Sasso, C.; Krupp, N. Bibcode: 2006ASPC..358..431S Altcode: The triplet of the He I transitions around 10830 Å not only shows a rich variety of Stokes profiles, but also allows the full magnetic vector in the upper chromosphere to be probed, thus revealing the magnetic structure of loops, current sheets, finely structured supersonic downflows, the chromospheric layers of sunspots (supporting the presence of uncombed fields in the penumbra), flares, and the quiet Sun. A very brief overview of some of the observations and results obtained so far is given. Title: A New Spoke Formation Model Authors: Jones, G. H.; Krupp, N.; Krueger, H.; Roussos, E.; Ip, W.; Mitchell, D. G.; Krimigis, S. M.; Woch, J.; Lagg, A.; Fraenz, M.; Dougherty, M. K.; Arridge, C. S.; McAndrews, H. J. Bibcode: 2006AGUFM.P34A..06J Altcode: A new model is proposed for the formation of spokes in Saturn's rings. We contend that they are formed by the electrostatic charging of sub-micron ring particles by magnetic field-aligned electron beams originating in Saturn's atmosphere. The existence of these beams has recently been confirmed by the MIMI instrument aboard Cassini. Although observed by MIMI outside the main ring system, the beams are also expected to occur closer to the planet. On striking the rings, the electrons charge the dust, causing the levitation of the fine grains above the main ring plane. A simulation of the proposed formation process provides strong supporting evidence for the validity of the process, explaining the spokes' formation locations, morphologies, and subsequent development as observed in Voyager images. The process can be tested using Cassini observations; we outline how the model's validity can be gauged. Title: Icy Moon Absorption Signatures: Probes of Saturnian Magnetospheric Dynamics and Moon Activity Authors: Roussos, E.; Krupp, N.; Jones, G. H.; Paranicas, C.; Mitchell, D. G.; Krimigis, S. M.; Motschmann, U.; Dougherty, M. K.; Lagg, A.; Woch, J. Bibcode: 2006AGUFM.P51F..03R Altcode: After the first flybys at the outer planets by the Pioneer and Voyager probes, it became evident that energetic charged particle absorption features in the radiation belts are important tracers of magnetospheric dynamical features and parameters. Absorption signatures are especially important for characterizing the Saturnian magnetosphere. Due to the spin and magnetic axes' near-alignment, losses of particles to the icy moon surfaces and rings are higher compared to the losses at other planetary magnetospheres. The refilling rate of these absorption features (termed "micorsignatures") can be associated with particle diffusion. In addition, as these microsignatures drift with the properties of the pre-depletion electrons, they provide us direct information on the drift shell structure in the radiation belts and the factors that influence their shape. The multiple icy moon L-shell crossings by the Cassini spacecraft during the first 2 years of the mission provided us with almost 100 electron absorption events by eight different moons, at various longitudinal separations from each one and at various electron energies. Their analysis seems to give a consistent picture of the electron diffusion source and puts aside a lot of inconsistencies that resulted from relevant Pioneer and Voyager studies. The presence of non-axisymmetric particle drift shells even down to the orbit of Enceladus (3.98 Rs), also revealed through this analysis, suggests either large ring current disturbances or the action of global or localized electric fields. Finally, despite these absorption signatures being observed far from the originating moons, they can give us hints on the nature of the local interaction between each moon and the magnetospheric plasma. It is, nevertheless, beyond any doubt that energetic charged particle absorption signatures are a very powerful tool that can be used to effectively probe a series of dynamical processes in the Saturnian magnetosphere. Title: Supersonic Downflows in the Vicinity of a Solar Pore Authors: Lagg, A.; Woch, J.; Solanki, S. K.; Gandorfer, A. Bibcode: 2006ASPC..358..437L Altcode: At the footpoints of magnetic arcades spanning over a site of flux emergence we observe strong redshifts in the He I triplet at 1083 nm. These redshifts are associated with downflow speeds of up to 40 km s-1. Within the spatial resolution of our data (1 arcsec-2 arcsec) obtained with the Tenerife Infrared Polarimeter at the VTT we find an almost unshifted atmospheric component coexisting with the redshifted component. We were able to retrieve the magnetic field configuration in both the unshifted and the redshifted component simultaneously and infer an uncombed, fibril-like structure of the upper chromosphere. The supersonic downflow speeds are interpreted as a consequence of a significantly reduced pressure scale height above the pore, where the magnetic arcades are rooted. A temporal series of the fast downflow region reveals that the supersonic flow is maintained for more than one hour. Making use of the increased spatial resolution of the new TIP2 instrument we are working on reducing the upper limit on the size of the fibril-like flux channels in the upper chromosphere. Title: Formation of Saturn's ring spokes by lightning-induced electron beams Authors: Jones, G. H.; Krupp, N.; Krüger, H.; Roussos, E.; Ip, W. -H.; Mitchell, D. G.; Krimigis, S. M.; Woch, J.; Lagg, A.; Fränz, M.; Dougherty, M. K.; Arridge, C. S.; McAndrews, H. J. Bibcode: 2006GeoRL..3321202J Altcode: Spokes are near-linear markings sometimes visible on Saturn's rings. They are widely accepted as being electrostatically-levitated sheets of ~0.6 micron-radius charged grains. Previously-suggested causes of the grains' charging do not agree with all spoke characteristics, which include their rapid generation, localized formation primarily in Saturn's midnight-dawn sector, the seasonality of their apparitions, and, crucially, their morphologies. We contend that spokes are caused by lightning-induced electron beams striking the rings, at locations magnetically-connected to thunderstorms. This view is supported by a semi-quantitative spoke morphology simulation. Spokes' formation locations are further controlled by Saturn's ionospheric density, which reaches a near-dawn minimum where electron beams can most easily propagate to the rings. The beams may generate observed X-ray emission, supply particles to Saturn's radiation belts, and over time will modify the rings' constituents. Finally, we report Cassini MIMI instrument observations of an electron burst which displays some characteristics expected of a lightning-induced event. Title: Correction to ``Ion abundance ratios in the Jovian magnetosphere'' Authors: Radioti, A.; Krupp, N.; Woch, J.; Lagg, A.; Glassmeier, K. -H.; Waldrop, L. S. Bibcode: 2006JGRA..11110224R Altcode: No abstract at ADS Title: A New Spoke Formation Model Authors: Jones, Geraint H.; Krupp, N.; Krueger, H.; Roussos, E.; Ip, W.; Mitchell, D. G.; Krimigis, S. M.; Woch, J.; Lagg, A.; Fraenz, M.; Dougherty, M. K.; Arridge, C. S.; McAndrews, H. J. Bibcode: 2006DPS....38.4214J Altcode: 2006BAAS...38..562J We propose a new model for the formation of spokes in Saturn's rings. The model involves the electrostatic charging of sub-micron dust grains in the rings by magnetic field-aligned electron beams. Such beams have recently been observed by the MIMI instrument aboard Cassini at 3.1 Saturn radii, outside the main ring system. It is reasonable to expect the beams to also occur closer to the planet. We contend that on striking the rings, the electron beams’ dust-charging effects cause the levitation of the fine grains above the main ring plane, forming the spokes. Using a semi-quantitative model, we explain the spokes’ formation locations, their initial morphologies, and the subsequent development of their appearance as reported in studies based on Voyager observations. Controlling effects on the spokes’ locations are also proposed. We outline tests that can be carried out using Cassini datasets to gauge the validity of our proposed formation process.

MIMI/LEMMS work at MPS is financed by the German Bundesministerium für Bildung und Forschung, and by the Max Planck Gesellschaft. Title: Milne-Eddington inversions of the He <sf>I</sf> 10 830 Å Stokes profiles: influence of the Paschen-Back effect Authors: Sasso, C.; Lagg, A.; Solanki, S. K. Bibcode: 2006A&A...456..367S Altcode: 2011arXiv1102.0898S Context: .The Paschen-Back effect influences the Zeeman sublevels of the He I multiplet at 10 830 Å, leading to changes in strength and in position of the Zeeman components of these lines.
Aims: .We illustrate the relevance of this effect using synthetic Stokes profiles of the He I 10 830 Å multiplet lines and investigate its influence on the inversion of polarimetric data.
Methods: .We invert data obtained with the Tenerife Infrared Polarimeter (TIP) at the German Vacuum Tower Telescope (VTT). We compare the results of inversions based on synthetic profiles calculated with and without the Paschen-Back effect being included.
Results: .We find that when taking into account the incomplete Paschen-Back effect, on average 16% higher field strength values are obtained. We also show that this effect is not the main cause for the area asymmetry exhibited by many He I 10 830 Stokes V-profiles. This points to the importance of velocity and magnetic field gradients over the formation height range of these lines.
Title: Multi-component analysis of a flaring region in the chromospheric He I 1083.0 nm triplet Authors: Sasso, C.; Lagg, A.; Solanki, S. K. Bibcode: 2006IAUJD...3E..31S Altcode: We present infrared spectropolarimetric observations of the solar active region NOAA 0763 obtained with the new Tenerife Infrared Polarimeter (TIP 2) at the German Vacuum Tower Telescope (VTT) during May 2005, taken in the chromospheric He I 1083.0 nm multiplet. The region was in the initial phase of a C2.0 flare. We observe up to 4 atmospheric components within the spatial resolution of our observations. The components are clearly separated in wavelength, the largest separation corresponding to downflow velocities of up to 64 km/s. We give preliminary results on the magnetic vector and the line-of sight velocity obtained by inverting the Stokes I, Q, U and V profiles of the He 1083.0 nm triplet. Title: Flux Emergence In The Solar Photosphere - Diagnostics Based On 3-D Rradiation-MHD Simulations Authors: Yelles Chaouche, L.; Cheung, M.; Lagg, A.; Solanki, S. Bibcode: 2006IAUJD...3E..75Y Altcode: We investigate flux tube emergence in the solar photosphere using a diagnostic procedure based on analyzing Stokes signals from different spectral lines calculated in 3-D radiation-MHD simulations. The simulations include the effects of radiative transport and partial ionization and cover layers both above and below the solar surface. The simulations consider the emergence of a twisted magnetic flux tube through the solar surface. We consider different stages in the emergence process, starting from the early appearance of the flux tube at the solar surface, and following the emergence process until the emerged flux looks similar to a normal bipolar region. At every stage we compute line profiles by numerically solving the Unno-Rachkovsky equations at every horizontal grid point. Then, following observational practice, we apply Milne-Eddington-type inversions to the synthetic spectra in order to retrieve different atmospheric parameters. We include the influence of spatial smearing on the deduced atmospheric parameters to identify signatures of different stages of flux emergence in the solar photosphere. Title: Solar Coronal Magnetic Field Mapper Authors: Solanki, S. K.; Raouafi, N. -E.; Gandorfer, A.; Schühle, U.; Lagg, A. Bibcode: 2006ESASP.617E.160S Altcode: 2006soho...17E.160S No abstract at ADS Title: Planetary Rotation Modulation of Various Measured Plasma Parameters in Saturns Magnetosphere: a Possible Mechanism Authors: Mitchell, D. G.; Brandt, P. C.; Carbary, J. F.; Krimigis, S. M.; Mauk, B. E.; Paranicas, C. P.; Roelof, E. C.; Jones, G.; Krupp, N.; Lagg, A.; Gurnett, D. A.; Kurth, W. S.; Dougherty, M. K.; Southwood, D. J.; Saur, J.; Zarka, P. Bibcode: 2006AGUSM.P44A..04M Altcode: The period of Saturn kilometric radiation (SKR) modulation established by Voyagers 1 and 2 in 1980 and 1981 (10 hours, 39 minutes, 22.4 +/- 7s) has been adopted by the International Astronomical Union as the official rotation period of Saturn. Other quantities seen to exhibit modulation at about the same period include the magnetic field, energetic electron spectral slope, and energetic neutral atom (ENA) emission. However first the Ulysses spacecraft, and later Cassini, have measured a significantly different the SKR period than the Voyagers (approximately 10 hours, 45minutes). This change is problematic, because if the field is truly locked to Saturns rotation, this would imply a huge change in angular momentum over a relatively short period. Furthermore, no consensus model has been accepted to explain how the effects of the rotation are communicated from the planetary body out to distances as large as over 20 Rs (Saturn radii). In this paper, we explore the possibility that the observed SKR period is not Saturns intrinsic rotation period, but rather stems from friction between the ionosphere and Saturns zonal wind flows. We suggest that the SKR location reflects a high conductivity anomaly in Saturns ionosphere, whereby rigid rotation is imposed on that part of the magnetosphere that connects via the magnetic field and field-aligned currents with this high conductivity anomaly (this is similar to the hypothesis of the camshaft model for the magnetic perturbation suggested by Espinosa et al., 2003). In that work, Espinosa et al. suggest that the high conductivity region exists because of a high order magnetic anomaly, that affects ionospheric conductivity locally. We extend that model to include a feed-back loop with the magnetosphere. In this scenario, a magnetospheric disturbance initially triggered by interaction with the field-aligned currents results in additional energy deposition in the ionosphere. This further increases the ionospheric conductivity, but more importantly ties the high conductivity region to the middle magnetospheric disturbance. The local zonal thermospheric winds, if they are in frictional equilibrium with the conducting ionosphere, will move the high conductivity region (and the rest of the ionosphere) at whatever velocity they are traveling. With the feedback between the magnetospheric heating and the ionospheric conductivity established, the field-aligned current remains rooted in the wind-convected ionosphere, and so the active (SKR) meridian will slowly drift away from the core-rooted magnetic anomaly. The process will be self-sustaining for a certain length of time, until it fizzles out (either because the magnetospheric instability is no longer sufficiently close to triggering, or because the source particle populations are depleted, or whatever). Some time later, when the magnetosphere has stored sufficient energy to prime the instability, it will go off again, again starting at the location of the magnetic anomaly. Espinosa, S. A., D. J. Southwood, and M. K. Dougherty, How can Saturn impose its rotation period in a noncorotating magnetosphere? J. Geophys. Res., 108(A2), 1086, doi:10.1029/2001JA005084, 2003 Title: On the fine structure of sunspot penumbrae. III. The vertical extension of penumbral filaments Authors: Borrero, J. M.; Solanki, S. K.; Lagg, A.; Socas-Navarro, H.; Lites, B. Bibcode: 2006A&A...450..383B Altcode: 2005astro.ph.10586B In this paper we study the fine structure of the penumbra as inferred from the uncombed model (flux tube embedded in a magnetic surrounding) when applied to penumbral spectropolarimetric data from the neutral iron lines at 6300 Å. The inversion infers very similar radial dependences in the physical quantities (LOS velocity, magnetic field strength etc.) as those obtained from the inversion of the Fe I 1.56 μm lines. In addition, the large Stokes V area asymmetry exhibited by the visible lines helps to constrain the size of the penumbral flux tubes. As we demonstrate here, the uncombed model is able to reproduce the area asymmetry with striking accuracy, returning flux tubes as thick as 100-300 kilometers in the vertical direction, in good agreement with previous investigations. Title: Enceladus' Varying Imprint on the Magnetosphere of Saturn Authors: Jones, G. H.; Roussos, E.; Krupp, N.; Paranicas, C.; Woch, J.; Lagg, A.; Mitchell, D. G.; Krimigis, S. M.; Dougherty, M. K. Bibcode: 2006Sci...311.1412J Altcode: The bombardment of Saturn's moon Enceladus by >20-kiloelectron volt magnetospheric particles causes particle flux depletions in regions magnetically connected to its orbit. Irrespective of magnetospheric activity, proton depletions are persistent, whereas electron depletions are quickly erased by magnetospheric processes. Observations of these signatures by Cassini's Magnetospheric Imaging Instrument allow remote monitoring of Enceladus' gas and dust environments. This reveals substantial outgassing variability at the moon and suggests increased dust concentrations at its Lagrange points. The characteristics of the particle depletions additionally provide key radial diffusion coefficients for energetic electrons and an independent measure of the inner magnetosphere's rotation velocity. Title: Anti-planetward auroral electron beams at Saturn Authors: Saur, J.; Mauk, B. H.; Mitchell, D. G.; Krupp, N.; Khurana, K. K.; Livi, S.; Krimigis, S. M.; Newell, P. T.; Williams, D. J.; Brandt, P. C.; Lagg, A.; Roussos, E.; Dougherty, M. K. Bibcode: 2006Natur.439..699S Altcode: Strong discrete aurorae on Earth are excited by electrons, which are accelerated along magnetic field lines towards the planet. Surprisingly, electrons accelerated in the opposite direction have been recently observed. The mechanisms and significance of this anti-earthward acceleration are highly uncertain because only earthward acceleration was traditionally considered, and observations remain limited. It is also unclear whether upward acceleration of the electrons is a necessary part of the auroral process or simply a special feature of Earth's complex space environment. Here we report anti-planetward acceleration of electron beams in Saturn's magnetosphere along field lines that statistically map into regions of aurora. The energy spectrum of these beams is qualitatively similar to the ones observed at Earth, and the energy fluxes in the observed beams are comparable with the energies required to excite Saturn's aurora. These beams, along with the observations at Earth and the barely understood electron beams in Jupiter's magnetosphere, demonstrate that anti-planetward acceleration is a universal feature of aurorae. The energy contained in the beams shows that upward acceleration is an essential part of the overall auroral process. Title: Icy moon absorption signatures reveal non-axisymmetric drift shells in the Saturnian radiation belts: implications for a magnetospheric electric field? Authors: Roussos, E.; Krupp, N.; Jones, G. H.; Paranicas, C.; Lagg, A.; Woch, J.; Mitchell, D. G.; Krimigis, S. M.; Dougherty, M. K. Bibcode: 2006epsc.conf..545R Altcode: Data collected during the first 22 orbits of Cassini by the MIMI/LEMMS experiment revealed a significant number of energetic electron absorption features (microsignatures) from the icy moons Enceladus, Tethys and Dione, between 3.8 and 7 Rs . As the absorption regions drift as the pre-depletion plasma, electron microsignatures can be used as drift-shell tracers. By organizing the observed location of the microsignatures with local time we find that electrons have the tendency to drift inward in the midnight section and outward in the noon to dusk sector. Displacements up to 0.5 Rs at Tethys and 0.9 Rs at Dione cannot only be the result of magnetopause and ring current disturbances. This suggests the presence of an electric field or other processes that cause significant deviations from drift shell axisymmetry, even down to 5 Rs . We investigate possible mechanisms that could account for these observations (such the possible influence of a dusk to dawn electric field). Irrespective of the mechanism responsible for the observed displacements, the non-axisymmetric drift shells could be in part responsible for plasma transport inside the L-shells of Dione and Tethys as the refilling of the electron microsignatures points to very slow radial diffusion for electrons. Title: The Saturnian magnetosphere after two years of Cassini in situ results Authors: Krupp, N.; Jones, G. H.; Roussos, E.; Lagg, A.; Mitchell, D. G.; Krimigis, S. M.; Arridge, C.; McAndrews, H.; Dougherty, M. K.; Kurth, W. Bibcode: 2006epsc.conf..386K Altcode: The Cassini spacecraft arrived at Saturn in July 2004. Since then the particles and fields instrument onboard have continuously monitoring the Saturnian magnetosphere for more than 30 orbits covering mostly the dawn and predawn regions. In this study we use energetic particle, magnetic field and plasma wave data obtained during the first two years in orbit to investigate the global structure of the Saturnian magnetosphere and its dynamics. On a global scale the Cassini data reveal a variety of spatial structures in the inner and outer magnetosphere as well as temporal variations in most of the derived properties. We will show local time, latitude and longitude variations of energetic particles and changes in the energy spectrum as well as correlations with other data sets. Highest intensities of energetic particles have been found in the radiation belts between 6 and 15 RS with a local time asymmetry between dawn and dusk. The outer magnetosphere beyond that distance sometimes show very pronounced dropouts in the magnetotail indicating dynamical processes in that part of the magnetosphere. Parameters from the plasma, magnetic field and plasma wave investigations show also an unexpected modulation at the planetary rotation period. The investigation of these modulations is key to understanding the dynamics of the Saturnian magnetosphere and will be discussed in the talk. Title: Influence of the Paschen-Back effect on the results of polarimetric inversions of the He I 10830 Å triplet Authors: Sasso, C.; Lagg, A.; Solanki, S. K.; Socas-Navarro, H. Bibcode: 2006MSAIS...9..126S Altcode: The He I triplet at 10830 Å has a great potential for determining the magnetic field vector in the upper chromosphere. The triplet is Zeeman sensitive (Landé factors 2.0, 1.75 and 1.25) and shows the signature of the Hanle effect under appropriate conditions. Additionally, the Zeeman sublevels are influenced by the Paschen-Back effect leading to changes in strength and in position of the Zeeman components of the transitions forming the triplet. In this work we calculate the influence of the Paschen-Back effect on the Stokes profiles and investigate its relevance to inversions on spectro-polarimetric data obtained with the Tenerife Infrared Polarimeter (TIP) at the German Vacuum Tower Telescope (VTT). Title: Comparison periodic substorms at Jupiter and Earth Authors: Kronberg, E. A.; Woch, J.; Krupp, N.; Lagg, A.; Glassmeier, K. -H. Bibcode: 2006epsc.conf..483K Altcode: The Energetic Particles Detector and magnetometer measurements on Galileo showed that the Jovian magnetosphere undergoes reconfiguration processes which are very similar to the characteristics of a terrestrial substorm. At Jupiter the reconfiguration process occurs quasi-periodically with a repetition period of several days. In the terrestrial magnetosphere periodic substorms have been occasionally observed. The comparison of these periodic magnetospheric disturbances shows that they are similar in spatial distribution as well as in dynamic features, in spite of that the energy sources are different. In the case of the Earth, the well established energy source is the solar wind. In the case of the Jovian magnetosphere, it is the internal energy supplied by mass loading of fast rotating flux tubes. The energy accumulation and release leads to similar features: in the particle data we observed periodic "sawtooth" intensity fluctuations and plasma pressure and bulk velocity variations. In the magnetic field reoccurring signatures of stretching and dipolarization are observed. Furthermore, the release process is associated with an intensification of auroral emissions. In both magnetospheres signatures of cross-tail and field-aligned current generations are found. Title: The interaction of Rhea with Saturn's magnetosphere Authors: Jones, G. H.; Roussos, E.; Krupp, N.; Lagg, A.; Woch, J.; Cassini MIMI Team Bibcode: 2006epsc.conf..382J Altcode: Rhea, a 1500km-wide icy satellite of Saturn, orbits the planet at 8.7 Saturn radii. The Cassini spacecraft's single close approach to the moon to date occurred on November 26, 2005, approaching to within 500km of Rhea's surface. The LEMMS sensors of Cassini's MIMI instrument observed energetic (>20keV) electrons and ions in the moon's vicinity. As expected, a significant depletion was observed in low energy electrons downstream of the moon in the magnetospheric corotation flow. This missing population constituted particles that struck Rhea, forming a wake downstream. In addition to this relatively well-understood feature, the LEMMS data revealed a wide, relatively shallow electron flux depletion extending for several Rhea radii both inbound and outbound. Energetic ions also changed their characteristics within this broad region - a volume of space much larger than expected for a magnetospheric interaction with an inert body. We present our interpretation of this perplexing interaction region. Title: Comparison of the mass-release processes at Jupiter and Earth. Authors: Kronberg, E. A.; Woch, J.; Krupp, N.; Lagg, A.; Glassmeier, K. -H. Bibcode: 2006cosp...36.1712K Altcode: 2006cosp.meet.1712K The study using Energetic Particles Detector and magnetometer measurements on Galileo discovered that the corotational flow inherent for the Jovian magnetosphere is disrupted by radially outward and inward particle bursts in the magnetotail These bursts are associated with transient bipolar south-north magnetic field distortions and were reffered to the reconfiguration events at Jupiter and they are very similar to terrestrial substorms in terms of the characteristic features The reconfiguration process in the magnetotail consists of a transition from a quiet loading state to a disturbed state In analogy with the terrestrial substorm process the initial loading phase resembles characteristics of the growth loading phase and the disturbed phase unloading resembles the expansion phase of terrestrial substorms The recovery phase of the Jovian reconfiguration process seems to be very short in relation to the other phases similar as in the terrestrial case A closer look at the substorm-like processes in the Jovian magnetosphere also reveals further features similar to the terrestrial substorms such as the onset of magnetic fluctuations on a time scale of an ion gyroperiod in the magnetotail plasma sheet boundary layer formation signatures of travelling compression regions and the formation of a post plasmoid plasma sheet The signatures of cross-tail and field-aligned current generations during the reconfiguration process e g potential drop reversed dispersion of ions and electrons timing of reconfiguration events support the substorm Title: Particles and fields in Saturn's magnetosphere: Cassini results after 2 years in orbit Authors: Krupp, N.; Jones, G. H.; Roussos, E.; Lagg, A.; Woch, J.; Mitchell, D. G.; Krimigis, S. M.; Arridge, C.; McAndrews, H.; Kurth, W. Bibcode: 2006cosp...36.2071K Altcode: 2006cosp.meet.2071K The Cassini spacecraft arrived at Saturn in July 2004 Since then the particles and fields instrument onboard have continuously monitoring the Kronian magnetosphere for more than 30 orbits In this study we use energetic particle and magnetic field data obtained during the first two years in orbit to investigate the global structure of the Saturnian magnetosphere and its dynamics On a global scale the Cassini data reveal a variety of spatial structures and temporal variations in Saturn s magnetosphere We will show local time latitude and longitude variations of energetic particles fluxes and changes in the energy spectrum as well as correlations with other instruments Highest intensities of energetic particles have been found between 6 and 15 RS with a local time asymmetry between dawn and dusk Parameters from the plasma magnetic field and plasma wave investigations show a very pronounced modulation at the planetary rotation period The investigation of these modulations is key to understanding the dynamics of the Saturnian magnetosphere Title: Energetic particle composition during substorm-like events in the Jovian magnetosphere Authors: Radioti, A.; Woch, J.; Kronberg, E.; Krupp, N.; Glassmeier, K. -H.; Lagg, A. Bibcode: 2006cosp...36..660R Altcode: 2006cosp.meet..660R Based on the first 15 orbits of the Galileo spacecraft the composition of the energetic ion population of the Jovian magnetosphere is studied on a global scale Analyzing data from the Energetic Particles Detector onboard Galileo we study the relative ion abundance ratios of S O S He O He and p He at various energy nucleon Prominent enhancements of S O S He and O He abundance ratios are observed in the predawn sector associated with substorm-like events in the magnetotail During these reconfiguration events frequent small-scale variations of the south-north component of the magnetic field are present Acceleration by such magnetic field variations is examined as a possible mechanism for particle energization in that region When the time scale of the magnetic field variation is comparable to the particle gyro period the particle is accelerated by the induced electric field It is shown that during the Jovian substorms sulfur and oxygen ions are more effectively energized than helium and protons generating the observed ion abundances Title: Magnetic field measurements at different levels in the solar atmosphere and magnetic coupling Authors: Solanki, S. K.; Lagg, A. Bibcode: 2006cosp...36..916S Altcode: 2006cosp.meet..916S The magnetic field couples the different layers of the solar atmosphere with each other To unravel this coupling we need to be able to measure the field at all the relevant levels Most measurements of the magnetic field refer to the photosphere where magnetographs and spectropolarimetry using the Zeeman effect have allowed the magnetic structure and its evolution to be studied Observations of the field at higher layers in the atmosphere are more rare although a number of techniques are available These include Zeeman-effect and Hanle effect based measurements in the chromosphere and the corona as well as radio observations of coronal magnetic field These direct measurements are complemented by magnetic field extrapolations starting from the photosphere A brief overview of results obtained by various techniques of magnetic field measurements is given and a more detailed discussion of the main results of recent measurements of the field in the photosphere and the upper chromosphere are presented Title: The magnetospheric dynamics: Periodic substorms and Jupiter and Earth Authors: Kronberg, E. A.; Woch, J.; Glassmeier, K. -H.; Krupp, N.; Lagg, A. Bibcode: 2006cosp...36.1715K Altcode: 2006cosp.meet.1715K The Jovian and terrestrial magnetospheres show both fundamental commonalities and differences in their dynamical behaviour The Jovian substorm-like process is different from the terrestrial one by the inherently periodic behavior The cycle of topological stretching dipolarization repeats every several days Storage of magnetic energy in the lobe region by interaction with the interplanetary medium seems not to be the prime driver of the reconfiguration process Rather the Jovian reconfiguration process is internally driven In order to confirm this a simple conceptual model for this periodic process was developed It assumes that the ion-mass loading from internal plasma sources and the fast planetary rotation causes magnetotail field line stretching due to centrifugal forces This leads to the development of a magnetotail configuration favoring magnetic reconnection It is established that the condition for the onset of a tearing mode instability is satisfied just before each disturbed period of the reconfiguration process This causes both plasmoid formation and their release with continuing mass loading leading to renewed stretching of tail field lines The model yields that the intrinsic time constant of the Jovian reconfiguration process depends primarily on internal parameters like the mass-loading rate and is affected by the external solar wind conditions This model shows that the suggested intrinsic mechanism can explain the observed periodicities of several days of the Jovian substorm-like process We compare the Jovian periodical mass release processes Title: New insights into chromospheric structures from vector magnetic field measurements Authors: Lagg, A. Bibcode: 2006cosp...36..549L Altcode: 2006cosp.meet..549L During the last decade advances in instrumentation atomic physics and modeling have greatly improved the access to the chromospheric magnetic field vector High sensitivity polarimeters like the Tenerife Infrared Polarimeter TIP2 VTT or the Spectro-Polarimeter for Infrared and Optical Regions SPINOR HAO lead to reliable Zeeman measurements using the He I 10830 nm triplet Theoretical modeling of the Hanle and the Paschen Back effect helped to significantly improve the analysis of polarization measurements in this triplet allowing to directly visualize the magnetic structure of spicules polar prominences and active regions In this presentation I will summarize the results of chromospheric magnetic field measurements using this interesting triplet obtained in the last couple of years and discuss the great potential it has to further uncover the complex structure of the chromosphere Title: Temporal variability of the ion abundance ratios in the Jovian magnetosphere Authors: Radioti, A.; Krupp, N.; Woch, J.; Lagg, A.; Glassmeier, K. -H. Bibcode: 2006cosp...36..661R Altcode: 2006cosp.meet..661R Galileo as the first orbiting spacecraft around Jupiter provides the opportunity to study globally and in an extended energy range the energetic particle composition of the Jovian magnetosphere Analyzing data from the Energetic Particles Detector onboard Galileo we study the relative ion abundance ratios of S O S He O He and p He at various energy nucleon The global coverage of the Galileo trajectories enables a quantitative comparison with results of previous missions and especially Voyager 2 for the same radial distance and local time The large discrepancies found are attributed to a strong energy dependence but also to secular variations Ion intensities exhibit strong time variations between the two missions Temporal variations do exist also on times scales of several weeks as shown by the analysis of consecutive Galileo orbits Large and small scale variations of the ion abundance ratios are related to the temporal variability of the Io torus and to solar wind changes Additionally time varying particle acceleration processes are discussed Title: Low energy electron microsignatures at the orbit of Tethys: Cassini MIMI/LEMMS observations Authors: Roussos, E.; Krupp, N.; Woch, J.; Lagg, A.; Jones, G. H.; Paranicas, C.; Mitchell, D. G.; Livi, S.; Krimigis, S. M.; Dougherty, M. K.; Armstrong, T.; Ip, W. -H.; Motschmann, U. Bibcode: 2005GeoRL..3224107R Altcode: We report on low energy electron microsignature observations by the Low Energy Magnetospheric Measurement System (LEMMS) in the vicinity of Tethys's L-shell, during the first seven orbits of the Cassini mission. Tethys, due to its large size, is the source of strong microsignatures. Shallower absorption features seen are the result of aged Tethys microsignatures rather than the effect of its small Lagrangian moons. Several remarkable observations are also discussed: the displacement of the microsignatures indicates that the drift shell deviation from axisymmetry is greater than previously expected. Midnight to dawn wakes have drifted toward the planet whereas noon to dusk ones have drifted outward, revealing possible magnetospheric convection effects. Double microsignatures seen for the first time, suggest low radial diffusion coefficients and point to dynamic events in the magnetosphere. Title: Electron microsignatures from the Saturnian satellites: Cassini MIMI/LEMMS observations Authors: Roussos, E.; Krupp, N.; Jones, G. H.; Lagg, A.; Woch, J.; Paranicas, C.; Mitchell, D. G.; Krimigis, S. M.; Dougherty, M. K.; Ip, W. H.; Armstrong, T. P. Bibcode: 2005AGUFM.P43A0955R Altcode: Since the Saturn Orbit Insertion in July 2004, Cassini has performed numerous crossings of Saturn's inner moons L-shells at various longitudinal distances from the moons. The Low Energy Magnetospheric Measurement System (LEMMS) has detected a significant number of absorption features, referred to as microsignatures, in the the lowest energy electron channels (20-200 keV). The detections occur mainly in the vicinity of Tethys and Dione L-shells, while microsignatures from Enceladus, Rhea and Mimas are less frequent. From the analysis of these features we present: (i) estimates of the radial diffusion coefficient in Saturn's radiation belts as a function of L and energy, including for the first time their dependence on local time, (ii) the region of influence that the electric fields and energetic events (e.g. injections) have on the electron drift shells and (iii) the implications for the unique interaction characteristics of each moon with Saturn's magnetospheric plasma. Data from the recent close flybys of Tethys, Dione and Rhea are also briefly discussed. Title: Global Structure and Dynamics of the Kronian Magnetosphere: Cassini Results Authors: Krupp, N.; Lagg, A.; Woch, J.; Jones, G. H.; Roussos, E.; Krimigis, S. M.; Livi, S.; Mitchell, D. G.; Roelof, E. C.; Paranicas, C.; Hamilton, D. C.; Armstrong, T. P.; Dougherty, M. K. Bibcode: 2005AGUFM.P43A0949K Altcode: Since July 2004 the Cassini spacecraft is in orbit around Saturn providing in-situ measurements of the Saturnian magnetosphere. Several magnetospheric regions could be identified including the intense radiation belts and ring current regions in the inner magnetosphere as well as the equatorial plasma sheet and the regions close to the outer boundaries of the magnetosphere from which the global structure as well as the dynamic of the Kronian magnetosphere can be studied. Using the energetic particle measurements from the MIMI instrument as well as the magnetic field measurements from the MAG instrument onboard Cassini we will discuss the derived pitch angle distributions, electron and ion energy spectra and periodicities in magnetic field components and particle parameters in various regions. Some of the results are (1) asymmetry in the particle fluxes between the day and night sector at comparable distances; (2) highly varying particle fluxes as a consequence of large-scale dynamic processes in the equatorial plasma sheet; (3) field-aligned bi-directional electron fluxes in the outer part of the Kronian magnetosphere with correlation to the Saturnian aurora; (4) variations of the magnetic field components and electron fluxes with the planetary rotation period pointing to a magnetic anomaly inside the planet or pointing to corotating structures in the Saturnian magnetotail; (5) injections and corotating structures in Saturn's magnetotail as a consequence of dynamical processes. Title: Macrosignatures of the icy moons in the inner magnetosphere of Saturn Authors: Jones, G. H.; Roussos, E.; Krupp, N.; Woch, J.; Lagg, A.; Paranicas, C.; Krimigis, S. M.; Mitchell, D. G.; Mauk, B. H.; Ip, W. -P.; Dougherty, M. K. Bibcode: 2005AGUFM.P43A0958J Altcode: The energetic particle population of the inner magnetosphere of Saturn is significantly affected by the presence of the planet's icy moons. Charged particles that strike the surfaces of these moons are removed from the magnetosphere, significantly reducing the fluxes of particles observed on crossing these moons' L-shells. The signatures have previously been separated into two classes: Microsignatures are temporary signatures in longitude and time observed in the charged-particle wakes of satellites. Macrosignatures are longitude- and time-averaged effects of absorbers on the radial distribution of particles. Here, we present an overview of the decreases in energetic particle fluxes observed at these moons' L-shells, as observed by the LEMMS portion of the MIMI instrument aboard Cassini. We concentrate on macrosignatures, particularly those at the L-shell of Enceladus, where a deep, persistent decrease in energetic protons is observed. We discuss these features' formation, and the possible contribution of E-ring material to the observed flux decreases. It has recently been suggested that charged particle bombardment leads to a conversion of water ice from a crystalline to an amorphous state. Here we discuss the particle evidence for persistent weathering of Enceladus's surface and the extent to which each charged species is likely involved in this process. Title: Observation of the Spectrum and Angular Distribution of Trapped Protons in Saturn's Inner Magnetosphere: Implications for Sources, Transport, and Loss Authors: Armstrong, T.; Manweiler, J.; Krupp, N.; Lagg, A.; Krimigis, S.; Livi, S.; Mitchell, D.; Roelof, E.; Paranicas, C.; Hamilton, D. Bibcode: 2005AGUFM.P43A0951A Altcode: The Cassini MIMI investigation carried a set of solid state detectors designed in part to resolve the shape and magnitude a local minimum in the flux of energetic protons at about 10 MeV reported from the Voyager 2 flyby in 1981. Preliminary results from Cassini Saturn Orbit Injection (SOI) show that this reported feature of the proton spectrum has persisted throughout the region within Dione's orbit . We will report the fluxes, pitch angle distributions, and phase space densities along with our estimates of source and loss processes of Saturnian trapped protons. Further, we will attempt to reconcile our results with those from Voyagers 1 and 2 and Pioneer 11, especially regarding the inner "CRAND" source. Title: Diagnostics of a Simulated Flux Tube Emergence Authors: Yelles Chaouche, L.; Cheung, M.; Lagg, A.; Solanki, S. Bibcode: 2005ESASP.600E..74Y Altcode: 2005ESASP.600E..74C; 2005ESPM...11...74C; 2005dysu.confE..74C No abstract at ADS Title: Influence of the Paschen-Back Effect on the Stokes Profiles of the he 10830 Å Triplet Authors: Sasso, C.; Lagg, A.; Solanki, S. K. Bibcode: 2005ESASP.596E..64S Altcode: 2005ccmf.confE..64S No abstract at ADS Title: Results from Chromospheric Magnetic Field Measurements Authors: Lagg, A. Bibcode: 2005ESASP.596E...6L Altcode: 2005ccmf.confE...6L No abstract at ADS Title: International Scientific Conference on Chromospheric and Coronal Magnetic Fields Authors: Innes, D. E.; Lagg, A.; Solanki, S. A. Bibcode: 2005ESASP.596E....I Altcode: 2005ccmf.confE....I No abstract at ADS Title: Photospheric and Chromospheric Magnetic Structure of a Sunspot Authors: Orozco Suarez, D.; Lagg, A.; Solanki, S. K. Bibcode: 2005ESASP.596E..59O Altcode: 2005ccmf.confE..59O No abstract at ADS Title: Magnetic Loops: a Comparison of Extrapolations from the Photosphere with Chromospheric Measurements Authors: Wiegelmann, T.; Lagg, A.; Solanki, S.; Inhester, B.; Woch, J. Bibcode: 2005ESASP.596E...7W Altcode: 2005ccmf.confE...7W No abstract at ADS Title: International Scientific Conference on Chromospheric and Coronal Magnetic Fields Authors: Innes, D. E.; Lagg, A.; Solanki, S. A. Bibcode: 2005ESASP.596.....I Altcode: 2005ccmf.conf.....I No abstract at ADS Title: Supersonic Downflows in the Solar Chromosphere are Very Common Authors: Aznar Cuadrado, R.; Solanki, S. K.; Lagg, A. Bibcode: 2005ESASP.596E..49A Altcode: 2005ccmf.confE..49A No abstract at ADS Title: Evidence of Enceladus and Tethys microsignatures Authors: Paranicas, C.; Mitchell, D. G.; Livi, S.; Krimigis, S. M.; Roussos, E.; Krupp, N.; Woch, J.; Lagg, A.; Saur, J.; Turner, F. S. Bibcode: 2005GeoRL..3220101P Altcode: We present evidence of two icy satellite microsignatures in the Cassini LEMMS data. Just upstream of Enceladus, a deep and narrow decrease in the flux of several MeV electrons is consistent with a recent absorption by that moon. This microsignature is collocated with a deep depletion in the MeV proton flux. The proton feature is much wider than the satellite diameter, suggesting multiple interactions and/or losses to the E Ring and neutral gas. An observed increase in proton flux toward the planet suggests a possible inner magnetospheric source. A decrease in the low energy electron intensity downstream of Tethys is also consistent with a microsignature approximately the size of the satellite that has drifted slightly toward the planet near midnight. Modeling suggests that microsignatures near Tethys' orbit would persist for more than a complete rotation of Saturn and the radial diffusion coefficient is about 10-9 RS2/s. Title: Dynamics of energetic particles and neutrals in Saturn's variable magnetosphere: results from the MIMI investigation Authors: Krimigis, S. M.; Mitchell, D. G.; Hamilton, D. C.; Krupp, N.; Livi, S.; Roelof, E. C.; Dandouras, J.; Mauk, B. H.; Brandt, P. C.; Paranicas, C. P.; Saur, J.; Armstrong, T. P.; Bolton, S.; Cheng, A. F.; Gloeckler, G.; Hill, M. E.; Hsieh, K. C.; Ip, W. H.; Lagg, A.; Lanzerotti, L. J.; McEntire, R. W.; Williams, D. J. Bibcode: 2005DPS....37.0604K Altcode: 2005BAAS...37Q.626K The Magnetospheric IMaging Instrument (MIMI) comprises three sensors: the Ion and Neutral Camera (INCA) provides images using energetic neutral atoms (ENA) and ions; the Charge-Energy-Mass-Spectrometer (CHEMS) determines the mass and charge state of ions; and the Low Energy Magnetospheric Measurement System (LEMMS) measures ion and electron distributions using a dual field-of-view telescope (Krimigis et al, Space Sci Rev,114, 2333-329, 2004). Measurements by MIMI after Saturn orbit insertion on 1 July 2004 have elucidated several new features of the planet's magnetosphere. These include: (1) A dynamical magnetosphere with an11-hour periodicity. (2) The first remotely-sensed radiation belt inside Saturn's D-ring. (3) Abundant water products in the magnetospheric plasma > or = 10 kev/charge, but little nitrogen (N+/O+<0.05); neutral gas is found to be a major mechanism for particle loss. (4) Injections of plasma in the ∼4-11Rs and also >20Rs corotate with the planet and can last for several days. (5) Activity (possibly analogous to Earth's substorms) occurs in Saturn's magnetotail in the 20-40 Rs region during large magnetospheric disturbances; this has not been observed during quiet times. (6) Field-aligned electron beams occur in the dawn to early morning sector as close as ∼10 Rs, and map to latitudes of observed Saturn aurora. (7) A gas cloud around Titan with dimensions > 1 Rs, with strong high ( 3200 km) altitude ENA emissions forms a continuous, asymmetric ``halo." (8) Titan's emission is centered on moon--hot plasma interaction with the exosphere; changing intensity depends on variable (x10-100) ion population and magnetic field orientation about Titan. (9) Upstream ion events have been measured to large (<50 to > 800 Rs) distances; several are enriched in oxygen ions, suggesting a magnetospheric origin. The observations will be presented and discussed in the context of current models of Saturn's magnetosphere. Title: The Saturnian plasma sheet as revealed by energetic particle measurements Authors: Krupp, N.; Lagg, A.; Woch, J.; Krimigis, S. M.; Livi, S.; Mitchell, D. G.; Roelof, E. C.; Paranicas, C.; Mauk, B. H.; Hamilton, D. C.; Armstrong, T. P.; Dougherty, M. K. Bibcode: 2005GeoRL..3220S03K Altcode: Since July 2004 Cassini is in orbit around Saturn providing in-situ measurements of the Saturnian magnetosphere. One of the three sensors of the Magnetospheric Imaging Instrument (MIMI) is the Low Energy Magnetospheric Measurement System (LEMMS) that responds to energetic particles which can serve as indicators of key regions (Krimigis et al., 2005) and ongoing plasma processes in the magnetosphere. In this paper we identify and characterize, based on energetic particle and magnetic field measurements, the radiation belts, the plasma sheet, and the lobe region. The transition between plasma sheet and lobe region sometimes occurs very rapidly, and sometimes occurs with the period of Saturn's rotation. We explain the highly variable nature of the Saturnian plasma sheet as a combination of the geometry of the Cassini trajectory, together with the variable location of the boundary between open and closed field lines caused by a strong localized magnetic anomaly in the Saturnian field. Title: Ion abundance ratios in the Jovian magnetosphere Authors: Radioti, A.; Krupp, N.; Woch, J.; Lagg, A.; Glassmeier, K. -H.; Waldrop, L. S. Bibcode: 2005JGRA..110.7225R Altcode: 2005JGRA..11007225R Galileo, as the first orbiting spacecraft around Jupiter, provides the opportunity to study globally the composition of the energetic ion population in the equatorial plane of the Jovian magnetosphere. This enables us to derive the relative importance of the various sources and sinks of plasma and energetic particles in the largest magnetosphere of our solar system. In this paper we use data from the Energetic Particles Detector (EPD) on board Galileo and derive relative ion abundance ratio maps of S/O, S/He, O/He, and p/He. We extend the previous work in terms of global coverage, species, and energy range. In addition we compare them with previous results and especially with those derived on board Voyager 2. We found that the S/O abundance ratio is relatively constant throughout the magnetosphere decreasing slightly with radial distance. Within the error bars the S/O ratios could be reproduced. Only a minor energy dependence is observed for this ratio pointing to a common source for both ions. The S/He-, O/He-, and p/He-ratios decrease with increasing radial distance, furthering the notion that sulfur, oxygen, and protons originate mainly from a source within the Jovian system, in contrast with helium, which originates from the solar wind. A spectral kink observed at energies of several 100 keV/nuc for all species and most pronounced for helium explains the observed energy dependence of the ratios relative to helium. Differences in the abundance ratios up to more than one order of magnitude between sequential orbits are evidence of large temporal variations taking place in the Jovian magnetosphere. These variations and the strong energy dependence can explain the differences between the results derived from Galileo EPD measurements and those from Voyager data. Title: On the fine structure of sunspot penumbrae. II. The nature of the Evershed flow Authors: Borrero, J. M.; Lagg, A.; Solanki, S. K.; Collados, M. Bibcode: 2005A&A...436..333B Altcode: 2005astro.ph..3677B We investigate the fine structure of the sunspot penumbra by means of a model that allows for a flux tube in horizontal pressure balance with the magnetic background atmosphere in which it is embedded. We apply this model to spectropolarimetric observations of two neutral iron lines at 1.56 μm and invert several radial cuts in the penumbra of the same sunspot at two different heliocentric angles. In the inner part of the penumbra we find hot flux tubes that are somewhat inclined to the horizontal. They become gradually more horizontal and cooler with increasing radial distance. This is accompanied by an increase in the velocity of the plasma and a decrease of the gas pressure difference between flux tube and the background component. At large radial distances the flow speed exceeds the critical speed and evidence is found for the formation of a shock front. These results are in good agreement with simulations of the penumbral fine structure and provide strong support for the siphon flow as the physical mechanism driving the Evershed flow. Title: Jovian plasma sheet morphology: particle and field observations by the Galileo spacecraft Authors: Waldrop, L. S.; Fritz, T. A.; Kivelson, M. G.; Khurana, K.; Krupp, N.; Lagg, A. Bibcode: 2005P&SS...53..681W Altcode: We present results from an investigation of the plasma sheet encounter signatures observed in the Jovian magnetosphere by the Energetic Particles Detector (EPD) and Magnetometer (MAG) onboard the Galileo spacecraft. Maxima in ion flux were used to identify over 500 spacecraft encounters with the plasma sheet between radial distances from Jupiter from 20 to 140 RJ during the first 25 orbits (4 years of data). Typical signatures of plasma sheet encounters show a characteristic periodicity of either 5 or 10 hours that is attributed to an oscillation in the relative distance between the spacecraft and the plasma sheet that arises from the combination of planetary rotation and offset magnetic and rotational axes. However, the energetic particle and field data also display much variability, including instances of intense fluxes having little to no periodicity that persist for several Jovian rotation periods. Abrupt changes in the mean distance between the plasma sheet and the spacecraft are suggested to account for some of the transitions between typical flux periodicities associated with plasma sheet encounters. Additional changes in the plasma sheet thickness and/or amplitude of the plasma sheet displacement from the location of the spacecraft are required to explain the cases where the periodicity breaks down but fluxes remain high. These changes in plasma sheet characteristics do not display an obvious periodicity; however, the observations suggest that dawn/dusk asymmetries in both the structure of the plasma sheet and the frequency of anomalous plasma sheet encounters are present. Evidence of a thin, well-ordered plasma sheet is found out to 110 RJ in the dawn and midnight local time sectors, while the dusk magnetosphere is characterized by a thicker, more disordered plasma sheet and has a potentially more pronounced response to an impulsive trigger. Temporal variations associated with changing solar wind conditions are suggested to account for the anomalous plasma sheet encounters there. Title: How To Use Magnetic Field Information For Coronal Loop Identification Authors: Wiegelmann, T.; Inhester, B.; Lagg, A.; Solanki, S. K. Bibcode: 2005SoPh..228...67W Altcode: 2008arXiv0801.4573W The structure of the solar corona is dominated by the magnetic field because the magnetic pressure is about four orders of magnitude higher than the plasma pressure. Due to the high conductivity the emitting coronal plasma (visible, e.g., in SOHO/EIT) outlines the magnetic field lines. The gradient of the emitting plasma structures is significantly lower parallel to the magnetic field lines than in the perpendicular direction. Consequently information regarding the coronal magnetic field can be used for the interpretation of coronal plasma structures. We extrapolate the coronal magnetic field from photospheric magnetic field measurements into the corona. The extrapolation method depends on assumptions regarding coronal currents, e.g., potential fields (current-free) or force-free fields (current parallel to magnetic field). As a next step we project the reconstructed 3D magnetic field lines on an EIT-image and compare with the emitting plasma structures. Coronal loops are identified as closed magnetic field lines with a high emissivity in EIT and a small gradient of the emissivity along the magnetic field. Title: Saturn's Dynamic Magnetosphere: Energetic Particles and Neutrals from the Magnetospheric Imaging Instrument (MIMI) Authors: Krimigis, S. M.; Mitchell, D. G.; Hamilton, D. C.; Krupp, N.; Livi, S.; Roelof, E. C.; Dandouras, I.; Mauk, B. H.; Brandt, P. C.; Paranicas, C.; Saur, J.; Armstrong, T. P.; Bolton, S.; Cheng, A. F.; Gloeckler, G.; Hill, M. E.; Hsieh, K.; Ip, W.; Lagg, A.; Lanzerotti, L. J.; McEntire, R. W.; Williams, D. J. Bibcode: 2005AGUSM.P14A..04K Altcode: The MIMI investigation comprises three sensors: the Ion and Neutral Camera (INCA) provides images using energetic neutral atoms (ENA) and ions; the Charge-Energy-Mass-Spectrometer (CHEMS) determines the mass and charge state of ions; and the Low Energy Magnetospheric Measurement System (LEMMS) measures ion and electron distributions using a dual field-of-view telescope (Krimigis et al., 2004). Measurements by MIMI following Saturn orbit insertion on 1 July 2004 revealed: (1) a dynamical magnetosphere with a day-night asymmetry and an 11-hour periodicity; (2) several water-product ions (O+, OH+, H2O+), but little N+; (3) inferred quantities of neutral gas sufficient to cause major losses in the trapped ions and electrons in the middle and inner magnetosphere; (4) a Titan exosphere that is a copious source of energetic neutral atoms (ENA); (5) a previously unknown radiation belt residing inward of the D-ring that is most likely the result of double charge-exchange between the main radiation belt and the upper layers of Saturn's exosphere. Finally, MIMI data show evidence of injections of plasma on the night-side of the planet, some substorm-like in the magnetotail and others in the 7-10 RS region that subsequently corotate with the planet for a number of days before dissipating. The observations will be presented and discussed in the context of current theoretical models of Saturn's magnetosphere. Krimigis, S. M., et al., Magnetosphere Imaging Instrument (MIMI) on the Cassini Mission to Saturn/Titan, Space Sci. Rev., volume 114/1-4, pp 233-329, 2004. Title: Comparing magnetic field extrapolations with measurements of magnetic loops Authors: Wiegelmann, T.; Lagg, A.; Solanki, S. K.; Inhester, B.; Woch, J. Bibcode: 2005A&A...433..701W Altcode: 2008arXiv0801.4519W We compare magnetic field extrapolations from a photospheric magnetogram with the observationally inferred structure of magnetic loops in a newly developed active region. This is the first time that the reconstructed 3D-topology of the magnetic field is available to test the extrapolations. We compare the observations with potential fields, linear force-free fields and non-linear force-free fields. This comparison reveals that a potential field extrapolation is not suitable for a reconstruction of the magnetic field in this young, developing active region. The inclusion of field-line-parallel electric currents, the so called force-free approach, gives much better results. Furthermore, a non-linear force-free computation reproduces the observations better than the linear force-free approximation, although no free parameters are available in the former case. Title: Overview of Results from the Cassini Magnetospheric Imaging Instrument (MIMI) During the First Year of Operations Authors: Krimigis, S. M.; Mitchell, D. G.; Hamilton, D. C.; Krupp, N.; Livi, S.; Roelof, E. C.; Dandouras, J.; Mauk, B. H.; Brandt, J. P.; Paranicas, C.; Saur, J.; Armsrong, T. P.; Bolton, S.; Cheng, A. F.; Gloeckler, G.; Hsieh, K. C.; Ip, W. -H.; Lagg, A.; Lanzerotti, L. J.; McEntire, R. W.; Williams, D. J. Bibcode: 2005LPI....36.1361K Altcode: A high-level overview of MIMI results includes corotation of the magnetosphere, overwhelming presence of water-product ions, identification of a radiation belt inside the D-ring, and inferred presence of neutral gas absorbing ions and electrons inward of Dione's orbit. Title: Mass release at Jupiter: Substorm-like processes in the Jovian magnetotail Authors: Kronberg, E. A.; Woch, J.; Krupp, N.; Lagg, A.; Khurana, K. K.; Glassmeier, K. -H. Bibcode: 2005JGRA..110.3211K Altcode: 2005JGRA..11003211K The Jupiter orbiting spacecraft Galileo has provided evidence that the Jovian magnetotail is subject to a periodic process with typical timescales of several days by which the Jovian system is presumably releasing its excess iogenic mass. The mass release process resembles a terrestrial substorm in the sense of a global reconfiguration of the magnetotail. During the initial "loading" phase the plasma convection is at a moderate speed in the corotation direction and the Jovian plasma sheet appears to be in a stable configuration. In the release phase, reconnection through a thinned current sheet leads to radially inward and outward plasma flows and the ejection of plasmoids. Storage of magnetic energy in the lobe region seems not to be the prime driver of the reconfiguration process. Therefore the role of the solar wind as energy source is of less importance than for terrestrial substorms. Instead, it can be envisaged that plasma loading of fast rotating magnetic flux tubes and the associated centrifugal forces drive the reconfiguration process. Title: Dynamics of Saturn's Magnetosphere from MIMI During Cassini's Orbital Insertion Authors: Krimigis, S. M.; Mitchell, D. G.; Hamilton, D. C.; Krupp, N.; Livi, S.; Roelof, E. C.; Dandouras, J.; Armstrong, T. P.; Mauk, B. H.; Paranicas, C.; Brandt, P. C.; Bolton, S.; Cheng, A. F.; Choo, T.; Gloeckler, G.; Hayes, J.; Hsieh, K. C.; Ip, W. -H.; Jaskulek, S.; Keath, E. P.; Kirsch, E.; Kusterer, M.; Lagg, A.; Lanzerotti, L. J.; LaVallee, D.; Manweiler, J.; McEntire, R. W.; Rasmuss, W.; Saur, J.; Turner, F. S.; Williams, D. J.; Woch, J. Bibcode: 2005Sci...307.1270K Altcode: The Magnetospheric Imaging Instrument (MIMI) onboard the Cassini spacecraft observed the saturnian magnetosphere from January 2004 until Saturn orbit insertion (SOI) on 1 July 2004. The MIMI sensors observed frequent energetic particle activity in interplanetary space for several months before SOI. When the imaging sensor was switched to its energetic neutral atom (ENA) operating mode on 20 February 2004, at ~103 times Saturn's radius RS (0.43 astronomical units), a weak but persistent signal was observed from the magnetosphere. About 10 days before SOI, the magnetosphere exhibited a day-night asymmetry that varied with an ~11-hour periodicity. Once Cassini entered the magnetosphere, in situ measurements showed high concentrations of H+, H2+, O+, OH+, and H2O+ and low concentrations of N+. The radial dependence of ion intensity profiles implies neutral gas densities sufficient to produce high loss rates of trapped ions from the middle and inner magnetosphere. ENA imaging has revealed a radiation belt that resides inward of the D ring and is probably the result of double charge exchange between the main radiation belt and the upper layers of Saturn's exosphere. Title: Signature of Current Sheets as Seen by Tip at VTT in the HeI Multiplet at 1083.0 nm Authors: Aznar Cuadrado, R.; Solanki, S. K.; Lagg, A.; Thomas, R. M. Bibcode: 2004ESASP.575..593A Altcode: 2004soho...15..593A No abstract at ADS Title: Structure of Saturn's Magnetosphere as Revealed by Energetic Particles Authors: Krupp, N.; Woch, J.; Lagg, A.; Lim, J.; Krimigis, S. M.; Mitchell, D. G.; Roelof, E. C.; Mauk, B. H.; Paranicas, C.; Livi, S.; Armstrong, T. P.; Dougherty, M. K.; Kurth, W. S.; Louarn, P.; Dandouras, I.; Hamilton, D. C. Bibcode: 2004AGUFM.P54A..06K Altcode: At the end of June/beginning of July 2004 Cassini entered the magnetosphere of Saturn, 24 years after the last encounter of a spacecraft with the planet in 1981. Cassini entered the magnetosphere at about 08:00 local time 15 degrees below the equatorial plane, crossed the ring plane at a distance of 158500 km from the planet and reached 80230 km during closest approach, much closer than the smallest distance of Voyager. We report on results from the Low Energy Magnetospheric Measurement System (LEMMS), one out of three detector systems of the Magnetospheric Imaging Instrument (MIMI). MIMI/LEMMS is designed to investigate the global configuration and topology of the Kronian magnetosphere and to study dynamical processes. Its double-ended sensor is able to detect energetic electrons (15 keV- 5 MeV) and ions with energies above 30 keV separately. Several different regions inside the magnetosphere could be identified through changes and differences in the energetic particle characteristics: A lobe region with low ion and electron intensities, a plasma sheet region with higher intensities and very abrupt changes when the spacecraft enters/leaves the plasma sheet, the ring current region close to the planet with the highest measured intensities, and the region above the rings with extremely low particle intensities near background. Besides the very high intensities in the main radiation belts close to the planet and the very low intensities above the rings around closest approach results of MIMI/LEMMS observed the Kronian magnetosphere in a highly dynamic state indicated by so-called injection events and quasi-periodic fluctuations of the intensities with a period of about an hour. These periodicities have also been observed in magnetic field and plasma wave data on board Cassini. Preliminary analysis correlate these fluctuations with the motion of the plasma sheet of Saturn which either has a wavy surface or corrugated sheet structure within this period. Title: Imaging of Saturn's magnetosphere and energetic particles obsered during Cassini's orbit insertion at Saturn Authors: Krimigis, S. M.; Mitchell, D. G.; Hamilton, D. C.; Krupp, N.; Livi, S.; Roelof, E. C.; Dandouras, J.; Armstrong, T. P.; Mauk, B. H.; Paranicas, C.; Brandt, P.; Bolton, S.; Cheng, A. F.; Choo, T.; Gloeckler, G.; Hayes, J.; Hsieh, K. C.; Ip, W. -H.; Jaskulek, S.; Keath, E. P.; Kirsch, E.; Kusterer, M.; Lagg, A.; Lanzerotti, L. J.; LaVallee, D.; Manweiler, J.; McEntire, R. W.; Rasmuss, W.; Saur, J.; Turner, F. S.; Williams, D. J. Bibcode: 2004DPS....36.0202K Altcode: 2004BAAS...36.1067K The MIMI investigation comprises three sensors, the Ion and Neutral Camera (INCA), Charge-Energy-Mass-Spectrometer (CHEMS), and Low Energy Magnetospheric Measurement System (LEMMS) covering the energy ranges 7 keV/nuc < E < 200 keV/nuc (ions/neutrals), 3 < E < 230 keV/e (ions), and 0.02 < E <18 Mev (ions)/0.015 < E <1 Mev (electrons), respectively. Also, LEMMS measures high-energy electrons (E > 3 Mev) and protons (1.6 < E < 160 Mev) from the back end of the dual field-of-view telescope. The Saturn observation sequences began in January, 2004 and culminated in Saturn Orbit Insertion (SOI) on July 1, 2004. The MIMI sensors observed substantial activity in interplanetary space for several months prior to SOI, including several interplanetary shocks associated with corotating interaction regions, as well as numerous increases most likely originating from particle streams in the vicinity of the Saturnian bow shock. When the INCA sensor was switched to its energetic neutral atom (ENA) operating mode on day 51, at ∼ 1000 RS (0.43 AU), a weak signal was observed denoting the presence of Saturn's magnetosphere. Results during SOI revealed a dynamical magnetosphere with a day-night asymmetry and an 11-hour periodicity; several water-product ions (O+, OH+, H2O+), but no N+; a substantial gas cloud around Titan, but little evidence of a discernible torus; and sufficient (inferred) quantities of neutral gas that cause major losses to trapped ions in the middle and inner magnetosphere. Finally, INCA imaging has revealed a previously unknown radiation belt that resides inside the D-ring that is most likely the result of double charge-exchange between the main radiation belt and the upper layers of Saturn's exosphere. The observations will be presented and discussed in the context of current theoretical models. Title: Energetic particle observations in the vicinity of Jupiter: Cassini MIMI/LEMMS results Authors: Krupp, N.; Woch, J.; Lagg, A.; Livi, S.; Mitchell, D. G.; Krimigis, S. M.; Dougherty, M. K.; Hanlon, P. G.; Armstrong, T. P.; Espinosa, S. A. Bibcode: 2004JGRA..109.9S10K Altcode: We report on energetic particle measurements from the Low Energy Magnetospheric Measurement System (LEMMS) on board the Cassini spacecraft during the Jupiter flyby (October 2000 to April 2001). Cassini passed Jupiter on its way to Saturn on the dusk flank of the magnetosphere and explored for the first time the dusk-to-midnight magnetosheath of the planet. The flyby period can be divided into three distinct regimes where energetic particle parameter changes are observed. The first period (October 2000 to 10 January 2001) covers the approach phase toward the planet, including bow shock crossings in and out of the magnetosheath as well as the closest approach. In this period, LEMMS responded on solar wind pressure pulses and recorded the passing of two interplanetary shocks. Hours before the first bow shock crossing, low-energy particle intensity increases were observed, possibly with Jovian origin. Before the closest approach approach to the planet two inbound and one outbound bow shock crossings have been observed. The second period (9-10 January) is the period where Cassini briefly entered the magnetosphere twice at about 200 RJ. LEMMS data are only available during a large portion of the second encounter. Inside the magnetosphere the energetic electrons showed a bidirectional pitch angle distribution along the magnetic field, indicative of a closed magnetic field configuration predominantly in the north-south direction. In addition, quasi-periodic electron intensity variations with periods of ≈40 min were observed. The third period (January to April 2001) covers the distances between 205 and 800 RJ. The spacecraft was skimming along the bow shock boundary in the dusk-to-midnight sector. More than 44 inbound and outbound bow shock crossings have been observed. The most interesting magnetosheath encounter occurred between day 19 and day 28 at distances between 300 and 400 RJ. In that period, LEMMS observed strong intensification of MeV-electron fluxes to values similar to those measured inside the magnetosphere as reported by [2002]. Most of these increases in electrons were associated with sign changes in the north-south component of the magnetic field. We interpret these observations in terms of magnetic dayside reconnection and particle leakage through the duskside magnetosheath. Title: Energetic ion characteristics and neutral gas interactions in Jupiter's magnetosphere Authors: Mauk, B. H.; Mitchell, D. G.; McEntire, R. W.; Paranicas, C. P.; Roelof, E. C.; Williams, D. J.; Krimigis, S. M.; Lagg, A. Bibcode: 2004JGRA..109.9S12M Altcode: Spectra, integral moments, and composition (H, He, O, S) of energetic ions (50 keV to 50 MeV) are presented for selected Jupiter magnetospheric positions near the equator between radial distances of ∼6 to ∼46 Jupiter radii (RJ), as revealed by analysis of the Galileo Energetic Particle Detector data. These characteristics are then used as the basis of interpreting and modeling reported signatures of energetic ion/neutral gas interactions within Jupiter's inner magnetosphere, particularly energetic neutral atom emissions measured during the Cassini spacecraft flyby of Jupiter. Key findings include the following: (1) sulfur ions significantly dominate the energetic (≥50 keV) ion density and pressure at all radial distances >7 RJ; (2) protons dominate integral number and energy intensity planetward of 20-25 RJ; (3) a distinct signature of local, equatorial acceleration of energetic protons is revealed between Io (5.9 RJ) and Europa (9.4 RJ); (4) significant spectral and compositional signatures of neutral gas interactions are also revealed between the orbits of Io and Europa; (5) a previously reported significant depletion of ring current ion populations between Io and Europa during the early-phase operation of Galileo (∼1995), as compared with observations obtained during the Voyager epoch (1979), has persisted and probably deepened during later Galileo phases (1999); and (6) detailed energetic neutral atom emission modeling, based on the in situ results reported here, further constrains recent estimates of the contents of the neutral gas torus of Europa. Title: Thermal-magnetic relation in a sunspot and a map of its Wilson depression Authors: Mathew, S. K.; Solanki, S. K.; Lagg, A.; Collados, M.; Borrero, J. M.; Berdyugina, S. Bibcode: 2004A&A...422..693M Altcode: We present relations between thermal and magnetic quantities in a simple, isolated sunspot, as deduced from the inversion of 1.56 μm spectropolarimetric data. We used a combination of two infrared Fe I lines at 15 648.5 Å and 15 652.8 Å/ in the inversions. Due to the high Zeeman sensitivity of these lines, we can study this relationship in the entire sunspot. The relevant parameters were derived both as a function of location within the sunspot and of height in the atmosphere using an inversion technique based on response functions. In this paper we relate the magnetic vector with temperature. We find a non-linear relationship between the various components of the magnetic vector and temperature, which confirm the results from earlier investigations. We also computed the Wilson depression and the plasma β for the observed sunspot and compare our results with earlier findings. Title: On the fine structure of sunspot penumbrae. I. A quantitative comparison of two semiempirical models with implications for the Evershed effect Authors: Borrero, J. M.; Solanki, S. K.; Bellot Rubio, L. R.; Lagg, A.; Mathew, S. K. Bibcode: 2004A&A...422.1093B Altcode: Sunspot penumbrae exhibit prominent fine structure. Different interpretations of spectropolarimetric observations suggest different, sometimes contradictory, properties of this fine structure. In this paper we show that the results of inversions of penumbral infrared profiles based on one-component models with gradients of the atmospheric parameters and two-component models without gradients are compatible with each other. Our analysis reconciles the results of previous investigations and provides further support for the picture that sunspot penumbrae are composed of penumbral flux tubes embedded in a magnetic background. The magnetic field in the tubes is more horizontal and weaker than that of the background atmosphere. While the tubes carry most of the Evershed flow, the background is essentially at rest. We notice also that the magnetic field strength in the flux tubes drops much more slowly with radial distance than the background field. This finding is discussed as a possible driver for the Evershed flow. Title: Energetic electrons in the inner part of the Jovian magnetosphere and their relation to auroral emissions Authors: TomáS, A. T.; Woch, J.; Krupp, N.; Lagg, A.; Glassmeier, K. -H.; Kurth, W. S. Bibcode: 2004JGRA..109.6203T Altcode: The energetic particle distribution in the magnetosphere of Jupiter changes significantly between the inner and the middle magnetosphere. One of the most prominent changes is a transition of the electron pitch angle distribution (PAD) from a pancake to a bidirectional distribution. The transition is a persistent and localized feature defining a distinct spatial boundary between 10 and 17 RJ. We discuss the possible relation between the PAD boundary and some of the observed structures in the Jovian aurora. A comparison between the Hubble Space Telescope observations and the predicted ionospheric footprints of the PAD boundary indicates a good correlation, with a discrete belt of emissions equatorward of the main auroral oval. Furthermore, the precipitation energy flux associated with the energetic electron distribution at the PAD boundary is compatible with the brightness range of these auroral emissions. Title: Charged Particle Losses near the Inner Galilean Satellites Authors: Paranicas, C.; Lagg, A.; Krupp, N.; Woch, J.; Mauk, B. H. Bibcode: 2004AGUSMSM51A..05P Altcode: To study the losses of energetic charged particles in the inner magnetosphere of Jupiter, we have calculated proton phase space densities from the Galileo Energetic Particles Detector (EPD) data. The phase space density as a function of L shell is believed to obey a diffusion equation. In previous calculations, the phase space density in the inner magnetosphere has been shown to decrease inward toward the planet, suggesting sources at large distances, and losses due to satellite sweeping and other effects. The Galileo data reveal features indicating a loss process near the satellites Io and Europa. We also verify a region of strong loss just outside the orbital radius of Io. We will present loss rate estimates for the relevant physical processes within a diffusion context. These loss rate calculations, for instance, allow us to place an upper bound on the neutral gas distribution in radius (or L shell). Title: Europa's Neutral Gas Torus Authors: Mauk, B. H.; Mitchell, D. G.; McEntire, R. W.; Paranicas, C. P.; Roelof, E. C.; Williams, D. J.; Krimigis, S. M.; Lagg, A. Bibcode: 2004AGUSMSA22A..03M Altcode: In-situ energetic ion measurements from the Galileo spacecraft and remote energetic neutral atom (ENA) images from the Cassini spacecraft have been previously interpreted as revealing an unexpectedly massive torus of gas co-orbiting with Jupiter's moon Europa (Lagg et al., 2003; Mauk et al., 2003). Here we report on the results of detailed modeling of the ENA emission process from the Europa regions. Updates to the distribution and composition of the trapped energetic ion populations are included in the models, as are considerations of the partitioning of the gas products into multiple atomic and molecular species. Comparisons between the models and the Cassini observations reveal a torus with a total gas content equal to (0.5 +/- 0.2) E34 atoms plus molecules. This value is higher than, but within a factor of 3 of, an estimate inferred from a prediction of gas densities derived from Voyager plasma measurements and modeling of the interaction between the plasmas and the gases assumed to be emanating from Europa (Schreier et al., 1993). Lagg, A., N. Krupp, J. Woch, and D. J. Williams, Geophys. Res. Lett., 30, DOI 10.1029/2003GL017214, 2003. Mauk, B. H., D. G. Mitchell, S. M. Krimigs, E. C. Roelof, and C. P. Paranicas, Nature, 241, 920, 2003. Schreier, S., A. Eviatar, V. M. Vasyliunas, and J. D. Richardson, J. Geophys. Res., 98, 21231, 1993. Title: Changes of the energetic particles characteristics in the inner part of the Jovian magnetosphere: a topological study Authors: Tomás, A.; Woch, J.; Krupp, N.; Lagg, A.; Glassmeier, K. -H.; Dougherty, M. K.; Hanlon, P. G. Bibcode: 2004P&SS...52..491T Altcode: Based on 33 Galileo passages through the inner part of the Jovian magnetosphere, the properties of the energetic charged particle population are investigated. Pronounced changes in the particle intensities, and in their energy and pitch angle distributions (PADs) are generally observed. The good coverage in local time and radial distance provided by Galileo allowed to trace the location of the most distinct changes within the equatorial plane. Independent of local time they occur at distances between 10 and 30RJ. Within this region particle intensities drop by several orders of magnitude and the energy spectra softens considerably. However, most prominent is a change of the electron PAD from a pancake or trapped (maximum at 90°) to a distribution which maximises at different pitch angle values (bi-directional or butterfly distributions). The change occurs rapidly, usually within the time resolution of the measurements, giving rise to a sharp and distinct boundary. This boundary is located dependent on the orbit between 10 and 17RJ. It does not exhibit striking local time dependencies, specifically a pronounced dawn-dusk asymmetry, with the exception of the boundary being slightly closer to the planet near noon compared to the other local times. The change in the electron pitch angle distribution occurs in a region where the magnetic field topology is still close to a dipolar field configuration. The softening of the particle energy spectra is collocated with the transition of the magnetic field from a dipolar to a current sheet topology. Possible connections to and implications for the Jovian high-latitude aurora are addressed. Title: Retrieval of the full magnetic vector with the He I multiplet at 1083 nm. Maps of an emerging flux region Authors: Lagg, A.; Woch, J.; Krupp, N.; Solanki, S. K. Bibcode: 2004A&A...414.1109L Altcode: A technique is presented to invert Stokes profiles of the He I 1083 nm multiplet lines in order to obtain the full magnetic vector and the line-of-sight velocity. The technique makes use of spectropolarimetry connected with the Zeeman effect supplemented by a simple Hanle effect based diagnostic when appropriate. It takes into account effects like line saturation, magnetooptieffects, etc. and is coupled with a genetic algorithm, which ensures that the global minimum in a goodness of fit hypersurface is found. Tests using both artificial and real data demonstrated the robustness of the method. As an illustration maps of deduced parameters of an emerging flux region are shown and briefly discussed. Title: Energetic Particles In The Vicinity Of Saturn: Cassini Mimi/Lemms Observations Authors: Krupp, N.; Lagg, A.; Woch, J.; Krimigis, S. M.; Livi, S.; Mitchell, D. G.; Hamilton, D. C.; Armstrong, T. P.; Lanzerotti, L. J. Bibcode: 2004cosp...35.2723K Altcode: 2004cosp.meet.2723K The Cassini-Huygens mission, launched in 1997, finally reached Saturn in July 2004. One of the science goals of the mission is to investigate the magnetosphere of Saturn, the interaction of the magnetospheric plasma and energetic particle population with the rings, moons and the solar wind. The Low Energy Magnetospheric Measurement System LEMMS (one out of three sensors of the Magnetospheric Imaging Instrument MIMI onboard Cassini) is able to measure low- and high-energy electrons and ions separately in the energy range between 0.015 to 5 MeV for electrons and 0.03 to about 160 MeV for ions. The instrument is mounted on a programmable scan platform allowing measurements from all direction within the scan plane which most of the time will be perpendicular to the ecliptic. This configuration will allow a good coverage in pitch angles. We present details of the first results in the vicinity of Saturn in and outside of the Kronian magnetosphere during the approach phase and insertion phase until July 2004. We will discuss these results by comparing them with early Pioneer and Voyager measurements. Title: Temporal evolution of chromospheric downflows Authors: Lagg, Andreas; Woch, J.; Krupp, N.; Gandorfer, A.; Solanki, S. K. Bibcode: 2004IAUS..223..279L Altcode: 2005IAUS..223..279L At the footpoints of loops spanning a site of flux emergence, earlier investigated in the papers by Solanki et al. (2003) and Lagg et al. (2004), we find large redshifts in the He 1083 nm line coexisting with an almost unshifted component. The speed associated with these redshifts reaches values as high as 40 km/s. We interpret these downflows in the context of several models: the free-fall downflow of matter along vertical field lines (Schmidt et al. 2000), the redshift by downward propagating acoustic waves (Hansteen 1993) and the motion of condensation regions to either side of loop footpoints (Müller et al. 2003). We present the temporal evolution of these redshifts and reconstruct the magnetic field vector in these regions for both the redshifted and the unshifted atmospheric component. Title: The structure and dynamics of the Jovian energetic particle distribution Authors: Woch, J.; Krupp, N.; Lagg, A.; Tomás, A. Bibcode: 2004AdSpR..33.2030W Altcode: We review the recent progress made in unravelling the properties of the energetic particle population in the magnetosphere of Jupiter. The importance of the findings with respect to mechanisms driving the dynamics of the Jovian system is addressed. We concentrate on the implications of phase space density variations for particle loss and source mechanism. Systematic local time and radial dependencies observed in the characteristics of the energetic ion and electron distributions, specifically the particle pitch angle distributions and particle flow pattern are discussed. They possibly bear important information for disentangling those mechanisms responsible for driving the Jovian aurora and for identifying the magnetospheric source populations. Furthermore, we discuss transient particle events in the tail which point to the importance of reconnection for the tail dynamics. Title: Long-term dynamics of the inner Jovian electron radiation belts Authors: Sicard, A.; Bourdarie, S.; Krupp, N.; Lagg, A.; Boscher, D.; Santos-Costa, D.; Gerard, E.; Galopeau, P.; Bolton, S.; Sault, R.; Williams, D. J. Bibcode: 2004AdSpR..33.2039S Altcode: Long-term variations of total Jovian synchrotron emission are well known to vary slowly in time. Several hypotheses have been proposed to explain these variations, they can be solar wind driven and/or induced by the geometrical effect of the declination of the Earth in the jovicentric coordinates, DE. However, until now, not any of them have been definitely proved. We propose here to investigate, this long-term dynamics based on appropriate simulation from a 3D model, Salammbô-3D. This model has been developed to study spatial distribution of electrons in the inner Jovian radiation belts. We will carry out two different approaches, the first one being based on synchrotron simulation from the Salammbô code and the second one being based on GALILEO EPD measurements. Two-dimensional images of Jupiter synchrotron emission can be obtained from our model, for any geometrical configuration ( λIII(CML), DE). Comparisons show a good agreement between modeling results and VLA observations. With Salammbô-3D, we can also study long-term variations of total Jovian synchrotron emission. The role of the two geometrical factors, λIII(CML) and DE, will be analyzed. First, we will present beaming curves (evolution of Jovian synchrotron emission in terms of λIII(CML)), resulting from the simulation to validate the geometry of the system in the code. Then, the evolution of the non-thermal flux density of synchrotron emission, in terms of DE, joviographic declination of the Earth, will be studied. With the help of simulations resulting from Salammbô-3D, we will try to discriminate between geometrical induced variations and natural dynamics. On the other hand we will investigate on GALILEO EPD measurements from 1995 until now, restricted to 5-10 Rj, to find out any similarity with the long-term variations of non-thermal flux density of synchrotron emission. Title: Microsignatures of satellite and ring absorption events Authors: Ip, W. H.; Hsu, W. H.; Lagg, A.; Krupp, N.; Woch, J.; Livi, S.; Armstrong, T.; Krimigis, S. K. Bibcode: 2004cosp...35.1517I Altcode: 2004cosp.meet.1517I Energetic charged particles interact with particulate material in planetary magnetospheres by impact absorption and surface sputtering. This process is of fundamental importance in providing a source of neutral gas and ions of chemical composition different from that of the solar wind. At the same time, the absorption of the trapped charged particles will create dips in the corresponding intensity distribution. Such absorption features, sometimes of just a few tens to hundreds of km in dimension, could serve as a sensitive probe to the existence of unseen small satellites and rings. In this presentation we will first make a brief review of the previous observations and theoretical interpretations of microsignatures detected in the Saturnian magnetosphere by the Pioneer 11 and Voyager spacecraft. This is to be followed by an examination of the opportunityy provided by the Cassini mission in making a detailed census of small satellites and narrow ring arcs of transient nature by a combination of charged particle experiments and imaging devices. Title: Dynamics of the Jovian magnetosphere Authors: Krupp, N.; Vasyliunas, V. M.; Woch, J.; Lagg, A.; Khurana, K. K.; Kivelson, M. G.; Mauk, B. H.; Roelof, E. C.; Williams, D. J.; Krimigis, S. M.; Kurth, W. S.; Frank, L. A.; Paterson, W. R. Bibcode: 2004jpsm.book..617K Altcode: Radial transport; Short-term variations: plasma interchange, injection events, ULF waves in Jupiter's magnetosphere; Long-term variations: phenomena at the planetary spin period, plasmasheet dynamics; Boundary phenomena: variability of boundaries, boundary layers, boundary fluctuations, injection of particles into interplanetary space. Title: The configuration of Jupiter's magnetosphere Authors: Khurana, Krishan K.; Kivelson, Margaret G.; Vasyliunas, Vytenis M.; Krupp, Norbert; Woch, Joachim; Lagg, Andreas; Mauk, Barry H.; Kurth, William S. Bibcode: 2004jpsm.book..593K Altcode: The inner magnetosphere: internal magnetic field, plasma sources, radiation belts; The middle magnetosphere: current sheet morphology and structural models, thermal and energetic plasmas, magnetic field models of the current sheet, the structure of the middle magnetosphere, bend-back of the field and plasma outflow; The outer magnetosphere: the Chapman-Ferraro currents, magnetotail; Plasma diffusion and convection: how plasma moves outwards, observations; Plasma acceleration and heating in Jupiter's magnetosphere: ionization and charge exchange, adiabatic processes, reconnection and magnetotail processes, low-altitude and auroral processes; Local time asymmetries: influence of solar wind. Title: Successful Measurement of the Full Magnetic Vector Near the Base of the Solar Corona Authors: Solanki, S. K.; Lagg, A.; Woch, J.; Krupp, N.; Landi Degl'Innocenti, E.; Collados, M. Bibcode: 2003AGUFMSH41D..05S Altcode: The measurement of coronal fields has in the past generally been restricted to the field strength or to only some of the components of the magnetic vector. We present here a technique for measuring the full magnetic vector near the base of the solar corona. As an application we report on observations of a developing active region with ongoing magnetic flux emergence. The data allow the first measurement of the 3-D structure of magnetic loops. They also provide the first detection of an electric current sheet located near the base of the solar corona. Such current sheets or tangential discontinuities of the coronal magnetic field have long been thought to be a major source of coronal heating. Title: Three dimensional structure of a regular sunspot from the inversion of IR Stokes profiles Authors: Mathew, S. K.; Lagg, A.; Solanki, S. K.; Collados, M.; Borrero, J. M.; Berdyugina, S.; Krupp, N.; Woch, J.; Frutiger, C. Bibcode: 2003A&A...410..695M Altcode: The magnetic, thermal and velocity structure of a regular sunspot, observed close to solar disk center is presented. Spectropolarimetric data obtained with the Tenerife Infrared Polarimeter (TIP) in two infrared FeI lines at 15 648.5 Å and 15 652.8 Å are inverted employing a technique based on response functions to retrieve the atmospheric stratification at every point in the sunspot. In order to improve the results for the umbra, profiles of Zeeman split OH lines blending the FeI 15 652.8 Å are also consistently fit. Thus we obtain maps of temperature, line-of-sight velocity, magnetic field strength, inclination, and azimuth, as a function of both location within the sunspot and height in the atmosphere. We present these maps for an optical depth range between log tau5 = 0 and log tau5 = -1.5, where these lines provide accurate results. We find decreasing magnetic field strength with increasing height all over the sunspot, with a particularly large vertical field gradient of ~ -4 G km-1 in the umbra. We also observe the so called ``spine'' structures in the penumbra, i.e. extended radial features with a stronger and more vertical magnetic field than the surroundings. Also we found that the magnetic field zenith angle increases with height. From the velocity map it is clear that the Evershed flow avoids the spines and mostly concentrates in the more inclined intervening field. The field inclination at a few locations in the outer penumbra in lower layers goes beyond 90o. These locations coincide with the strongest flows in the velocity map. Title: Three-dimensional magnetic field topology in a region of solar coronal heating Authors: Solanki, S. K.; Lagg, A.; Woch, J.; Krupp, N.; Collados, M. Bibcode: 2003Natur.425..692S Altcode: Flares and X-ray jets on the Sun arise in active regions where magnetic flux emerges from the solar interior amd interacts with the ambient magnetic field. The interactions are believed to occur in electric current sheets separating regions of opposite magnetic polarity. The current sheets located in the corona or upper chromosphere have long been thought to act as an important source of coronal heating, requiring their location in the corona or upper chromosphere. The dynamics and energetics of these sheets are governed by a complex magnetic field structure that, until now, has been difficult to measure. Here we report the determination of the full magnetic vector in an interaction region near the base of the solar corona. The observations reveal two magnetic features that characterize young active regions on the Sun: a set of rising magnetic loops and a tangential discontinuity of the magnetic field direction, the latter being the observational signature of an electric current sheet. This provides strong support for coronal heating models based on the dissipation of magnetic energy at current sheets. Title: Molecular Lines as Diagnostics of Solar and Stellar Magnetic Fields Authors: Berdyugina, S. V.; Solanki, S. K.; Lagg, A. Bibcode: 2003csss...12..210B Altcode: Thanks to recent advances in theory we can now calculate molecular line profiles in the presence of magnetic fields with high accuracy, both in the Zeeman and Paschen-Back regimes (Berdyugina et al. 2000; Berdyugina & Solanki 2001a). The synthetic Stokes profiles of various molecular species (e.g. TiO, OH, MgH, CN, FeH) have been compared with profiles observed in sunspots. The agreement between the theory and observations is remarkable. For example, the mutually opposite polarities of different OH lines are reproduced without invoking any free parameters, except the magnetic field strength and sunspot temperature. Introducing molecular lines into the inversion of sunspot spectra leads to significant improvements in the deduced magnetic field vector. Here we investigate how molecular lines can be used to deduce magnetic parameters of cool stars. We find that such lines are of great interest for measuring magnetic fields on cooler stars and in starspots. Title: Quiet-Sun inter-network magnetic fields observed in the infrared Authors: Khomenko, E. V.; Collados, M.; Solanki, S. K.; Lagg, A.; Trujillo Bueno, J. Bibcode: 2003A&A...408.1115K Altcode: This paper presents the results of an investigation of the quiet Sun's magnetic field based on high-resolution infrared spectropolarimetric observations obtained with the Tenerife Infrared Polarimeter (TIP) at the German VTT of the Observatorio del Teide. We observed two very quiet regions at disc centre. The seeing was exceptionally good during both observing runs, being excellent during one of them. In both cases the network was intentionally avoided to the extent possible, to focus the analysis on the characteristics of the weak polarization signals of the inter-network regions. We find that the Stokes V profile of Fe I 15648 Å line in almost 50% of the pixels and Stokes Q and/or U in 20% of the pixels have a signal above 10-3 (in units of continuum intensity Ic), which is significantly above the noise level of 2-3 x 10-4. This implies that we detect fluxes as low as 2 x 1015 Mx/px. We find evidence that we have detected most of the net flux that is in principle detectable at 1'' resolution with the Zeeman effect. The observed linear polarization resulting from the transverse Zeeman effect indicates that the magnetic fields have a broad range of inclinations, although most of the pixels show polarization signatures which imply an inclination of about 20o. Nearly 30% of the selected V-profiles have irregular shapes with 3 or more lobes, suggesting mixed polarities with different LOS velocity within the resolution element. The profiles are classified using a single value decomposition approach. The spatial distribution of the magnetic signal shows that profiles of different classes (having different velocities, splitting, asymmetries) are clustered together and form patches, close to the spatial resolution in size. Most of the field is found to be located in intergranular lanes. The statistical properties of the mainly inter-network field sampled by these observations are presented, showing that most of the observed fields are weak with relatively few kG features. The field strength distribution peaks at 350 G and has a FWHM of 300 G. Other parameters, such as profile asymmetries, filling factors and line-of-sight velocities are also determined and discussed.

Based on observations with the German Vacuum Tower Telescope (VTT) operated by the Kiepenheuer-Institut für Sonnenphysik at the Spanish Observatorio del Teide of the Instituto de Astrofísica de Canarias (IAC). Title: Infrared Polarimetry at the MPAe: The Solar Atmosphere from the Photosphere to the Upper Chromosphere Authors: Lagg, Andreas; Woch, Joachim; Solanki, Sami K.; Mathew, Shibu; Borrero, Juan M.; Krupp, N.; Raouafi, N. E. Bibcode: 2003ANS...324...29L Altcode: 2003ANS...324..D04L No abstract at ADS Title: In-situ observations of a neutral gas torus at Europa Authors: Lagg, A.; Krupp, N.; Woch, J.; Williams, D. J. Bibcode: 2003GeoRL..30.1556L Altcode: 2003GeoRL..30k..10L A persistent pattern in the pitch angle distributions of energetic protons near the orbit of Europa has been observed with the Energetic Particles Detector (EPD) on board the Galileo spacecraft during each of the Europa orbit crossings in the last 7 years. The proton fluxes at energies larger than 220 keV peak at equatorial pitch angles of 90° whereas fluxes of lower energy protons (80-220 keV) at this pitch angle are depleted. We propose that a Jupiter-surrounding neutral gas torus in the vicinity of the orbit of Europa is responsible for the depletion of energetic particle fluxes by charge exchange collisions. In order to reproduce the observed depletion signature an average neutral number density of 20 to 50 cm-3 is required. Title: Velocity Profiles Of Energetic Particles In The Jovian Magnetosphere Authors: Krupp, N.; Woch, J.; Lagg, A. Bibcode: 2003EAEJA....10013K Altcode: During the 34 orbits of the Galileo spacecraft around Jupiter in the years 1995--2003 the Energetic Particles Detector EPD measured angular distributions of energetic ions in Jupiter's equatorial plane. These distributions have been used to derive global velocity profiles of energetic ions. We present examples of these velocity profiles at different local times and radial distances and discuss local time asymmetries in Jupiter's magnetosphere. Title: Changes of the energetic particle characteristics in the inner jovian magnetosphere and the relation to auroral features Authors: Tomas, A.; Woch, J.; Krupp, N.; Lagg, A.; Glassmeier, K. -H.; Dougherty, M. K.; Hanlon, P. G.; Khurana, K. K.; Prange, R. Bibcode: 2003EAEJA.....9357T Altcode: Based on 33 Galileo passages through the inner part of the jovian magnetosphere the properties of the energetic charged particle population are investigated. Pronounced changes in the particle intensities, and in their energy and pitch angle distribution are generally observed. The good coverage in local time and radial distance provided by Galileo allowed to trace the location of the most distinct changes within the equatorial plane. Independent on local time they occur at distances between 10 R_J and 30 R_J. Within this region particle intensities drop by several orders of magnitude and the energy spectra softens considerably. However, most prominent is a change of the electron pitch angle distribution from a pancake or trapped to a bi-directional distribution with maxima close to 0^0 and 180^0. The change occurs rapidly, usually within the time resolution of the measurements, giving rise to a sharp and distinct boundary. This boundary is located dependent on the orbit between 10 and 17 R_J, and occurs in a region where the magnetic field topology is still close to a dipolar field configuration. In order to establish a relation to and implications for the jovian high-latitude aurora, the mentioned region was then mapped into the ionosphere of Jupiter, using the Khurana and the VIP4 model for the tracing of magnetic field lines. Estimation of the electron precipitation flux and a detailed comparison with HST observations suggest that the sharp pitch angle boundary is related to the transition between the belt of diffuse auroras and the main auroral oval of Jupiter. Title: New Molecular Indicators of Sunspot Magnetic Fields: Infrared OH Lines Authors: Berdyugina, S. V.; Solanki, S. K.; Lagg, A. Bibcode: 2003ASPC..286..299B Altcode: 2003ctmf.conf..299B No abstract at ADS Title: Structure of a simple sunspot from the inversion of IR spectral data Authors: Mathew, S. K.; Solanki, S. K.; Lagg, A.; Collados, M.; Berdyugina, S. V.; Frutiger, C.; Krupp, N.; Woch, J. Bibcode: 2003AN....324..388M Altcode: Analysis of spectral data of two neighboring infrared lines, Fe i 15648.5 Å (g = 3) and Fe i 15652.9 Å (g_eff = 1.53) are carried out for a simple sunspot when it was near the solar disk center (mu = 0.92), to understand the basic structure of sunspot magnetic field. Inversions of Stokes profiles are carried out to derive different atmospheric parameters both as a function of location within the sunspot and height in the atmosphere. As a result of the inversion we have obtained maps of magnetic field strength, temperature, line-of-sight velocity, field inclination and azimuth for different optical depth layers between log (tau_ {5}) = 0 and log (tau_ {5}) = -2.0 . In this paper we present few results from our inversion for a layer averaged between log (tau_ {5}) from 0.0 to -0.5. Title: Modeling the Fine Structure of a Sunspot Penumbra through the Inversion of Stokes Profiles Authors: Borrero, J. M.; Lagg, A.; Solanki, S. K.; Frutiger, C.; Collados, M.; Bellot Rubio, L. R. Bibcode: 2003ASPC..286..235B Altcode: 2003ctmf.conf..235B No abstract at ADS Title: Thermal-magnetic relation of a sunspot as inferred from the inversion of 1.5 μm spectral data Authors: Mathew, S. K.; Solanki, S. K.; Lagg, A.; Krupp, N.; Woch, J.; Collados, M.; Berdyugina, S.; Frutiger, C. Bibcode: 2002ESASP.505..501M Altcode: 2002IAUCo.188..501M; 2002solm.conf..501M We present the thermal-magnetic relation in a simple, isolated sunspot deduced from the inversion of 1.56 μm spectropolarimetric data. Due to the high Zeeman sensitivity of the g = 3, Fe I 1.5648 μm line, we can study this relationship in the entire sunspot. An inversion technique based on response functions is used to derive various parameters, both as a function of location within the sunspot and of height in the atmosphere. In this paper we attempt to relate field strength, vertical and radial field components and the field inclination with temperature. Title: Statistical properties of magnetic fields in intranetwork Authors: Khomenko, E. V.; Collados, M.; Lagg, A.; Solanki, S. K.; Trujillo Bueno, J. Bibcode: 2002ESASP.505..445K Altcode: 2002IAUCo.188..445K; 2002solm.conf..445K We report a study of the quiet sun's magnetic field based on high-resolution infrared spectropolarimetric observations (TIP/VTT). We find that in almost 50% of the pixels Stokes V and in 15% the Stokes Q and/or U profiles have a signal above 10-3. The statistical properties of the mainly intranetwork field sampled by these observations are presented, showing that most of the observed fields are weak (the field strength distribution peaks at 350 G and has a FWHM of 300 G) with very few kG features. The magnetized regions occupy a very small fill fractions (about 2%). The field changes properties on granular spatial scales and the size of the patches formed by similar profiles is close to 1". Most of the parameters of the observed polarization profiles show correlations with granulation parameters. Title: Leakage of energetic particles from Jupiter's dusk magnetosphere: Dual spacecraft observations Authors: Krupp, N.; Woch, J.; Lagg, A.; Espinosa, S. A.; Livi, S.; Krimigis, S. M.; Mitchell, D. G.; Williams, D. J.; Cheng, A. F.; Mauk, B. H.; McEntire, R. W.; Armstrong, T. P.; Hamilton, D. C.; Gloeckler, G.; Dandouras, J.; Lanzerotti, L. J. Bibcode: 2002GeoRL..29.1736K Altcode: 2002GeoRL..29o..26K For the first time, two spacecraft, Galileo and Cassini, observed Jupiter's magnetosphere simultaneously for nearly half a year between October 2000 and March 2001. This provided an unprecedented opportunity to disentangle spatial and temporal aspects of the dynamics of the Jovian magnetosphere. In this paper we report new results on the source of the leakage of energetic particles (electrons with energy 15 keV to several MeV and ions with energy > 30 keV) from the dusk side of the magnetosphere. The dual spacecraft measurements show clearly that magnetospheric particles leak directly into the interplanetary medium from the closed magnetosphere, and are the source for the ``upstream'' particle events [Baker et al., 1996; Zwickl et al., 1981; Krimigis, 1992; Haggerty and Armstrong, 1999; Anagnostopoulos et al., 1998] that have been reported from instruments during prior single spacecraft encounters with the planet. These events, consisting of high-energy particles of Jovian origin, have been observed throughout the heliosphere [Baker and Van Allen, 1976] and their propagation has recently been modelled [Fichtner et al., 2000; Ferreira et al., 2001]. Jupiter then is an important contributor to the interplanetary charged particle fluxes, especially within an astronomical unit of the planet. Title: Particle bursts in the Jovian magnetosphere: Evidence for a near-Jupiter neutral line Authors: Woch, Joachim; Krupp, Norbert; Lagg, Andreas Bibcode: 2002GeoRL..29.1138W Altcode: 2002GeoRL..29g..42W In the magnetosphere of Jupiter the plasma convection is driven by the planetary rotation up to considerable distances from the planet. However, at larger distances the rotational flow is often disrupted by explosive events, seen as jets of energetic particles propagating in the radial direction. These events are observed very frequently and can be regarded as an intrinsic property of the Jovian system. A statistical survey shows that the burst events are concentrated in the post-midnight tail region. Inward directed bursts dominate closer to the planet, outward directed bursts further away from the planet. The transition from mainly inward to mainly outward directed bursts defines the most probable location of a near-Jupiter neutral line. The findings corroborate early models which postulate that magnetic flux tubes heavily loaded with plasma originating from the moon Io will be stretched by the centrifugal forces up to such a degree that spontaneous reconnection sets in. This leads to acceleration of plasma and the release of plasmoids into interplanetary space. The process may also drive the recently observed auroral dawn storms at Jupiter. Title: A nebula of gases from Io surrounding Jupiter Authors: Krimigis, Stamatios M.; Mitchell, Donald G.; Hamilton, Douglas C.; Dandouras, Jannis; Armstrong, Thomas P.; Bolton, Scott J.; Cheng, Andrew F.; Gloeckler, George; Hsieh, K. C.; Keath, Edwin P.; Krupp, Norbert; Lagg, Andreas; Lanzerotti, Louis J.; Livi, Stefano; Mauk, Barry H.; McEntire, Richard W.; Roelof, Edmond C.; Wilken, Berend; Williams, Donald J. Bibcode: 2002Natur.415..994K Altcode: Several planetary missions have reported the presence of substantial numbers of energetic ions and electrons surrounding Jupiter; relativistic electrons are observable up to several astronomical units (AU) from the planet. A population of energetic (>30keV) neutral particles also has been reported, but the instrumentation was not able to determine the mass or charge state of the particles, which were subsequently labelled energetic neutral atoms. Although images showing the presence of the trace element sodium were obtained, the source and identity of the neutral atoms-and their overall significance relative to the loss of charged particles from Jupiter's magnetosphere-were unknown. Here we report the discovery by the Cassini spacecraft of a fast (>103kms-1) and hot magnetospheric neutral wind extending more than 0.5AU from Jupiter, and the presence of energetic neutral atoms (both hot and cold) that have been accelerated by the electric field in the solar wind. We suggest that these atoms originate in volcanic gases from Io, undergo significant evolution through various electromagnetic interactions, escape Jupiter's magnetosphere and then populate the environment around the planet. Thus a `nebula' is created that extends outwards over hundreds of jovian radii. Title: New Results of Energetic Particle Observations In The Duskside Jovian Magnetosphere Authors: Krupp, N.; Woch, J.; Lagg, A. Bibcode: 2002EGSGA..27.2855K Altcode: We report on new results from in-situ energetic particle measurements in the vicin- ity of Jupiter observed during the last year 2001 and the beginning of 2002 by the Energetic Particles Detector EPD onboard the Galileo spacecraft. We concentrate on so-called realtime data in and outside the Jovian magnetosphere from the outer dusk- side Jovian magnetosphere out the magnetopause location at about 100 planetary radii (RJ). EPD, which measures electrons (15-884 keV), ions (30-3200 keV) and protons (80-1250 keV), Helium (27-1000 keV/n), Oxygen (12-562 keV/n), and Sulfur (16-310 keV/n) ions separately, has the capability to derive energy spectra, relative ion compo- sition and angular distributions. This allows us to investigate relative ion composition, acceleration mechanisms and particle motion in regions of the Jovian magnetosphere where nearly no other data are available. Preliminary results show that the Jovian mag- netosphere at a local time of 1700 LT was very active and dynamic in early 2002 with very sharp boundary crossings around 80-100 RJ. The results will be discussed in the context of previous data sets at other local times and will be compared with MHD simulations Title: The structure and dynamics of the Jovian energetic particle population Authors: Woch, J.; Krupp, N.; Lagg, A. Bibcode: 2002cosp...34E.936W Altcode: 2002cosp.meetE.936W The comprehensive measurements performed by the Galileo spacecraft allowed for the first time to study in detail a planetary magnetosphere other than the Earth's one. The observations confirmed besides similarities the existence of significant differences. In contrast to the solar wind-controlled terrestrial magnetosphere, the plasma convection in the magnetosphere of Jupiter is driven by the fast planetary rotation up to considerable distances from the planet. Furthermore, strong internal plasma sources give rise to dynamical processes unknown from Earth. We will review the structure and dynamics of the Jovian system as deduced from energetic particle observations, focussing on the particle convection pattern, the formation of a near-Jupiter neutral line, substorm-like instabilities, and outer boundary layer processes. We will address their relevance for the high-latitude aurorae at Jupiter and discuss the relative importance of internal and solar wind energy sources. Title: Particle Emission From The Earth and Jupiter Magnetospheres Measured By The Cassini-lemms-particle Detector Authors: Kirsch, E.; Krupp, N.; Lagg, A.; Dougherty, M. K.; Krimigis, S. M.; Livi, S.; Armstrong, T. P. Bibcode: 2002EGSGA..27.5423K Altcode: The Cassini spacecraft passed the Earth in August 1999 and Jupiter in December 2000 on its way to planet Saturn. The Low Energy Magnetospheric Measurement System LEMMS (Ep > 30 keV, Ee > 15 keV) which is a part of the MIMI instrument ob- served particle bursts emitted from the Earth and Jupiter magnetospheres. We study the flux, energy and time behavior of such bursts and compare them for both planets. It will be discussed whether substorm or other effects are responsible for the particle acceleration and how the particles reach interplanetary magnetic field lines. We com- pare our results also with measurements obtained earlier by other Earth satellites and the Ulysses mission to planet Jupiter. Title: Energetic particle measurements during the earth swing-by of the Cassini spacecraft in August 1999 Authors: Lagg, A.; Krupp, N.; Livi, S.; Woch, J.; Krimigis, S. M.; Dougherty, M. K. Bibcode: 2001JGR...10630209L Altcode: We report on energetic particle measurements from the Low-Energy Magnetospheric Measurement System (LEMMS) aboard the Cassini spacecraft during the Earth swing-by maneuver in August 1999. LEMMS is capable of identifying the energy and incidence direction of energetic ions and electrons with energies of a few tens of keV to several tens of MeV. Cassini flew by Earth with a velocity of 16 kms-1 or 9 Earth radii (RE) per hour, which means that the entire dayside magnetosphere was passed within 1 hour. This fast flyby trajectory of the spacecraft provided a snapshot of the Earth's magnetosphere where key regions were passed within a few hours instead of typically tens of hours or days for orbiting spacecraft. The measurements provide a means to show the performance of the instrument's capabilities as well as to test models of energetic particle distributions within the Earth's magnetosphere [e.g. Sibeck et al., 1987]. Particle pitch angle distributions (PADs) on the inbound pass along the 1300 magnetic local time (MLT) meridian gradually changed from normal distributions (maximum at 90° pitch angle) to butterfly pitch angle distributions (maximum at intermediate pitch angles). Close to the plasmapause, LEMMS observed field-aligned bidirectional distributions. During the outbound pass through the inner magnetosphere at 0130 MLT, pitch angle distributions are generally close to isotropic. Shortly after a substorm onset, identified by ground-based observations and aboard the Polar spacecraft [Khan et al., this issue], LEMMS observed an energy-time dispersed enhancement in the differential flux of low-energy electrons. We further address the question of whether signatures of the Earth magnetotail were observed at distances beyond 5000RE when Cassini passed through the Earth's downstream region. LEMMS measured a series of particle increases during that time. The angular distributions during these enhancements show that most of these particles did indeed arrive from the Earth's direction. Nevertheless, the lack of singly charged heavy ions does not allow for a definite identification of this event as a deep-tail encounter. Title: Global flows of energetic ions in Jupiter's equatorial plane: First-order approximation Authors: Krupp, N.; Lagg, A.; Livi, S.; Wilken, B.; Woch, J.; Roelof, E. C.; Williams, D. J. Bibcode: 2001JGR...10626017K Altcode: Galileo, as the first orbiting spacecraft in an outer planet's magnetosphere, provides the opportunity to study global energetic ion distributions in Jupiter's magnetosphere. We present directional anisotropies of energetic ion distributions measured by the Galileo Energetic Particles Detector (EPD). The EPD measurements of proton (80-1050 keV), oxygen (26-562 keV/nucleon), and sulfur (16-310 keV/nucleon) distributions cover a wide energy range. Spatially, the data set includes measurements from 6 to 142 Jovian radii (RJ) and covers all local times inside the Jovian magnetosphere. For each species a single detector head scans almost the entire sky (~4π sr), producing the three-dimensional angular distributions from which the anisotropies are derived. Consequently, the resulting anisotropy estimates are both global and robust. Such anisotropies, generally produced by convective flow, ion intensity gradients, and field-aligned components, have long been used to estimate flow velocities and to locate spatial boundaries within magnetospheres. They can therefore provide vital information on magnetospheric circulation and dynamics. We find that the EPD measured anisotropies in the Jovian magnetosphere are dominated by a component in the corotational direction punctuated by episodic radial components, both inward and outward. Under the assumption that anisotropies are produced predominantly by convective flow, we derive flow velocities of protons, oxygen ions, and sulfur ions. The validity of that approach is supported by the fact that these three independently derived flow velocities agree, to a large extent, in this approximation. Thus, for the first time, we are able to derive the global flow pattern in a magnetosphere of an outer planet. In a comparison between the first-order EPD flow velocities and those predicted by a magnetohydrodynamic (MHD) simulation of the Jovian magnetosphere, we find that qualitatively the directions appear similar, although no firm evidence of steady outflow of ions has been observed at distances covered by Galileo. A first rough comparison indicates that the measured first-order flow velocities are higher by at least a factor of 1.5 than the MHD simulation results. Title: Observations in Jupiter's Vicinity with the Magnetospheric Imaging Instrument (MIMI) During Cassini/Huygens Flyby (October 2000-March 2001) Authors: Krimigis, S. M.; Mitchell, D. G.; Hamilton, D. G.; Livi, S.; Armstrong, T. P.; Cheng, A. F.; Dandouras, J.; Gloeckler, G.; Hsieh, K. C.; Ip, W. H.; Keath, E. P.; Kirsch, E.; Krupp, N.; Lagg, A.; Lanzerotti, L. J.; Mauk, B. H.; McEntire, R. W.; Roelof, E. C.; Wilken, B.; Williams, D. J. Bibcode: 2001AGUSM...P51A11K Altcode: The MIMI investigation comprises three sensors, the Ion and Neutral Camera (INCA), Charge-Energy-Mass-Spectrometer (CHEMS), and Low Energy Magnetospheric Measurement System (LEMMS) covering the energy ranges 7 keV/nuc <E<3 Mev/nuc (ions/ < 400 keV/nuc neutrals), 3<E<230 keV/e (ions), and 0.02 <E<18 Mev (ions)/0.015 <E<1 Mev (electrons), respectively. Also, LEMMS measures high-energy electrons (E>3 Mev) and protons (1.6 < E < 160 Mev) from the back end of the dual field-of-view telescope. MIMI obtained data intermittently from October 2000 to March 2001 corresponding to distances of ~ 103RJ upstream to ~ 103RJ downstream of the planet. The first unambiguous image of Energetic Neutral Atoms (ENA) was seen at ~ 1155RJ upstream and occupied one pixel in INCA at ~ 3% statistics. The observed intensity in the range ~ 15 to 55 keV (hydrogen) corresponds to ~ 0.08 (cm2 s keV)-1 when scaled to 100 RJ., i.e. similar to expectations based on Voyager 1 observations some 21 years earlier. Many images were obtained through, and past, closest approach (140 RJ; Mitchell et al, this AGU). In addition to ENA's, the CHEMS sensor detected several ion species of Jovian (O+, S+, SO2+, etc) and interstellar (He+) origin in the upstream medium that manifested themselves as pick-up and accelerated components, suggesting that cis-Jovian space is dominated by a nebula populated by volcanic gases from Io (Hamilton, et al, this AGU). Energetic electrons and ion events (LEMMS) were also present upstream and marked each crossing of the extended bow shock and magnetopause of the planet. While in the magnetosphere, field-aligned electron distributions provided unambiguous evidence of closed field lines to at least 200 RJ downstream from Jupiter. Simultaneously, highly charged (S3+, S4+, O3+, O2+, etc) ions were seen, suggesting that plasma outflow in the dusk magnetotail is dominated by magnetospheric rather than solar wind plasma. Evidence that Jovian plasmas are present to at least ~ 850RJ downstream will be presented and implications discussed on overall outflow of magnetospheric plasma. Title: Hot plasma heavy ion abundance in the inner Jovian magnetosphere (/<10 Rj) Authors: Maclennan, C. G.; Lanzerotti, L. J.; Lagg, Andreas Bibcode: 2001P&SS...49..275M Altcode: Knowledge of the hot plasma components of the Jovian environment is important for several scientific problems, including the acceleration and transport of Jovian plasmas, the stability of the plasma sheet, and the bombardment, implantation, and sputtering of the surfaces of Jovian moons, especially Europa. The multiple flybys of the Jovian moon Europa during the Galileo mission have provided the opportunity to study the time and spatial dependence of the abundance of the dominant hot plasma (∼0.2-10 MeV/nucleon (n)) heavy ions in the innermost region of the Jovian magnetosphere (≲10 Rj) . Reported here are measurements made by the CMS Δ E× E telescopes in the EPD instrument on the Galileo orbiter during the first six encounters with the moon Europa, data taken over a period of about 1.5 years. We use these measurements to study the hot plasma oxygen, sulfur, and sodium abundances near and inside the Europa orbit. The values we determine for these species in the energy range of 0.5-1.0 MeV/n are 0.67±0.05 for the S/O abundance and 0.05±0.01 for the Na/O abundance, and are similar to previous determinations made by instruments on the Voyager (measurements in 1979) and Ulysses (measurements in 1992) spacecraft. Title: Local time asymmetry of energetic ion anisotropies in the Jovian magnetosphere Authors: Krupp, N.; Woch, J.; Lagg, A.; Roelof, E. C.; Williams, D. J.; Livi, S.; Wilken, B. Bibcode: 2001P&SS...49..283K Altcode: Since December 1995 the Galileo spacecraft is in orbit around Jupiter. Up to now the spacecraft performed 25 orbits through the Jovian system within nearly 4 years providing an excellent data coverage in local time specifically for distances r<40 RJ. We present first-order anisotropies measured in energetic ion distributions from the Energetic Particles Detector (EPD) onboard Galileo. In this paper, we concentrate on measurements in the inner Jovian magnetosphere at distances between 6 and 40 RJ. Results from three different ion species show a pronounced local time asymmetry in the ion distributions at these distances especially between the dawn-prenoon and the dusk-premidnight sector of the magnetosphere. The predominantly first-order anisotropies in the co-rotation direction show larger amplitudes with radial outward components in the dawn sector whereas at dusk smaller anisotropies with small radial inward components are observed. Under the reasonable assumption that the anisotropies are primarily due to flow, we conclude that the flow pattern is asymmetric in local time. The flow in the dusk sector between 10 and 40 RJ is reduced compared to the dawn region. Title: Energetic charged particles near Europa Authors: Paranicas, C.; McEntire, R. W.; Cheng, A. F.; Lagg, A.; Williams, D. J. Bibcode: 2000JGR...10516005P Altcode: Galileo energetic particles detector (EPD) data are presented from several close encounters of the spacecraft with Jupiter's moon Europa. These data reveal significant decreases in electron and ion count rates very close to the moon and a few Europa radii downstream. The relation between count rate decreases and satellite absorption is analyzed because these particles sputter and chemically modify Europa's surface. Decreases on the plasma wake side of the satellite have radial extents comparable to satellite dimensions. Furthermore, some energetic particle wakes are shifted toward Jupiter from predicted locations. At some wake locations, electron fluxes do not get above instrument background levels. Corresponding electrons are lost preferentially on Europa's trailing hemisphere. Upstream of Europa during the E12 encounter, deep decreases in energetic ion count rates are observed for some instrument look directions. These decreases are associated with satellite absorption because the E12 closest approach altitude is smaller than relevant ion gyroradii. Other E12 decreases, such as a ``bite-out'' corresponding to a peak in the measured magnetic field intensity, are associated with ``secondary'' drifts in the radial direction caused by the field gradient. Pitch angle distributions measured during the E15 encounter (when Galileo was in Europa's wake) show much higher fluxes of locally mirroring particles than would be expected in a simple absorption signature. We suggest that a fraction of the upstream population escapes absorption because of the pileup of magnetic flux on Europa's trailing hemisphere. Title: Plasma sheet dynamics in the Jovian magnetotail: Signatures For substorm-like processes ? Authors: Woch, J.; Krupp, N.; Khurana, K. K.; Kivelson, M. G.; Roux, A.; Perraut, S.; Louarn, P.; Lagg, A.; Williams, D. J.; Livi, S.; Wilken, B. Bibcode: 1999GeoRL..26.2137W Altcode: During Galileo's orbit G2 in 1996 the Energetic Particles Detector (EPD) onboard the spacecraft detected a number of particle bursts with large radial/antisunward anisotropies in the distant Jovian magnetotail [Krupp et al., 1998]. In this letter we focus on a detailed analysis of one of the bursts. Prior to the onset of the burst, particle intensities at low energies increase over several hours. This phase can be interpreted as a plasma loading phase. It ends after the onset of strong distortions in the magnetic field with a bipolar excursion of the north-south component being the most prominent feature. The subsequent plasma sheet encounters show that the plasma sheet has thinned considerably. Accelerated/heated ion beams first from the Jovian direction and then later from the tail direction are seen at the plasma sheet and lobe interfaces and intense radio and plasma wave emissions are detected. The event is tentatively interpreted as a dynamical process, where the Jovian magnetotail is internally driven unstable by mass loading of magnetic flux tubes. Title: Determination of the neutral number density in the Io torus from Galileo-EPD measurements Authors: Lagg, A.; Krupp, N.; Woch, J.; Livi, S.; Wilken, B.; Williams, D. J. Bibcode: 1998GeoRL..25.4039L Altcode: During the GALILEO spacecraft encounter with Io in December 1995, the Energetic Particles Detector (EPD) [Williams et al., 1992] measured pitch angle distributions with high spatial and temporal resolution. All ion and electron channels show a depletion of field-aligned particles due to the interaction of trapped particles with the ionosphere / atmosphere of Jupiter. The medium nuclei channels, containing mainly sulphur and oxygen ions, show a second minimum for particles moving perpendicular to the magnetic field direction. This observation indicates that charge exchange between the singly-charged energetic ions and neutral atoms in the Io torus represents an important loss mechanism for energetic ions within the Io torus regions. Additionally, knowing the cross-sections of the involved charge exchange reactions it is possible to calculate the average neutral number density in the Io torus. The obtained result of ≈35 cm-3 is in good agreement with density estimations using ground based measurements. Title: Energetic particle bursts in the predawn Jovian magnetotail Authors: Krupp, N.; Woch, J.; Lagg, A.; Wilken, B.; Livi, S.; Williams, D. J. Bibcode: 1998GeoRL..25.1249K Altcode: From September to October 1996 the Galileo spacecraft crossed through the distant predawn tail region of the Jovian magnetosphere. The Energetic Particles Detector (EPD) onboard Galileo recorded a series of energetic particle flow bursts in the region beyond 80 RJ to the apojove at 113 RJ. The events are similar in nature to an event observed with the hot plasma instrument (LECP) onboard Voyager 2. The individual events last for several hours and cover the whole energy range from 15 keV to 55 MeV. The majority of them show considerable intensity increases which are most prominent for heavy ions. The events exhibit high radially outward directed anisotropies suggesting strongly collimated radial outflowing ion beams. The Voyager event was observed beyond the corotation boundary within a magnetospheric boundary layer termed the magnetospheric wind region and consequently it was assumed that the underlying process is connected with a boundary layer instability. However, the Galileo observations show the bursts being embedded in a general corotation flow. It is thus suggested that the flow bursts are driven by an internal plasma sheet process possibly associated with a major re-configuration of the Jovian magnetotail. A series of five very prominent flow bursts observed near apojove of the orbit occurred quasi-periodically with a repetition period of about 2.6±0.2 days which is presumably related to an internal time constant of the Jovian magnetotail. Title: Quasi-periodic modulations of the Jovian magnetotail Authors: Woch, J.; Krupp, N.; Lagg, A.; Wilken, B.; Livi, S.; Williams, D. J. Bibcode: 1998GeoRL..25.1253W Altcode: Measurements with the Energetic Particles Detector (EPD) on Galileo orbit C9 in the Jovian magnetotail revealed the existence of distinct quasi-periodic variations of energetic ion intensities which are superimposed on the well-known 10-hour modulations due to the planetary rotation. The intensity variations are associated with changes of the particle energy spectra and the plasma flow pattern. They are clearly of temporal nature and not the consequence of the spacecraft passing through periodically separated spatial structures. The modulation period is about 3 days. The oscillations are most pronounced throughout the middle magnetotail regime (20 to 80 RJ), however, seem to persist even in the deep tail region. The amplitude of the modulation is dependent on the particle energy. The highest energies measured (about 1 MeV) show the strongest variations. Energetic particle features with similar periodicity are observed on other Galileo orbits as well. The cause of these modulations is unclear; however, it may be speculated that they correspond to a quasi-periodic transition between two basic states of the Jovian magnetotail which occur with a time constant inherent to the Jovian magnetosphere. Title: Galileo-measured depletion of near-Io hot ring current plasmas since the Voyager epoch Authors: Mauk, B. H.; McEntire, R. W.; Williams, D. J.; Lagg, A.; Roelof, E. C.; Krimigis, S. M.; Armstrong, T. P.; Fritz, T. A.; Lanzerotti, L. J.; Roederer, J. G.; Wilken, B. Bibcode: 1998JGR...103.4715M Altcode: The first mass-discriminated, hot ion distribution moments (pressure, energy intensity) are determined for hot >50-keV ions in Jupiter's inner magnetosphere at the outer edge of Io's plasma torus by using the Galileo energetic particle detector (EPD) data. These hot plasmas were significantly depleted during the Galileo encounter in 1995 as compared with the Voyager epoch of 1979. The depletion of the hot ions is apparently caused by enhanced charge exchange losses of hot ions, perhaps associated with enhanced emissions of neutral gases from the volcanoes of Io. Such neutral gas enhancements could simultaneously explain increases, reported elsewhere, in the densities of the cooler Io torus plasmas. The hot plasma changes may explain why radial transport interchange turbulence has been observed by Galileo in the Io torus regions, whereas such turbulence was not apparent during the Voyager encounters in 1979. The hot ion depletion could also play a role in explaining the apparent differences between the Jovian auroral configuration observed in recent years by the Hubble space telescope and ground observers and the configuration observed by Voyager. This possibility is much less certain, however. Title: The Energetic Particles Detector (EPD) aboard the Galileo Spacecraft: First Results in the Jovian Magnetosphere Authors: Krupp, N.; Lagg, A.; Livi, S.; Wilken, B.; Woch, J.; Williams, D. J. Bibcode: 1997ASSL..220..319K Altcode: 1997tgms.conf..319K No abstract at ADS