Author name code: mason ADS astronomy entries on 2022-09-14 author:"Mason, Helen E." ------------------------------------------------------------------------ Title: Multiwavelength Observations by XSM, Hinode, and SDO of an Active Region. Chemical Abundances and Temperatures Authors: Del Zanna, G.; Mondal, B.; Rao, Y. K.; Mithun, N. P. S.; Vadawale, S. V.; Reeves, K. K.; Mason, H. E.; Sarkar, A.; Janardhan, P.; Bhardwaj, A. Bibcode: 2022ApJ...934..159D Altcode: 2022ApJ...934..159Z; 2022arXiv220706879D We have reviewed the first year of observations of the Solar X-ray Monitor (XSM) on board Chandrayaan-2 and the available multiwavelength observations to complement the XSM data, focusing on the Solar Dynamics Observatory AIA and Hinode XRT and EIS observations. XSM has provided disk-integrated solar spectra in the 1-15 keV energy range, observing a large number of microflares. We present an analysis of multiwavelength observations of AR 12759 during its disk crossing. We use a new radiometric calibration of EIS to find that the quiescent active region (AR) core emission during its disk crossing has a distribution of temperatures and chemical abundances that does not change significantly over time. An analysis of the XSM spectra confirms the EIS results and shows that the low first ionization potential (FIP) elements are enhanced compared to their photospheric values. The frequent microflares produced by the AR did not affect the abundances of the quiescent AR core. We also present an analysis of one of the flares it produced, SOL2020-04-09T09:32. The XSM analysis indicates isothermal temperatures reaching 6 MK. The lack of very high-T emission is confirmed by AIA. We find excellent agreement between the observed XSM spectrum and the one predicted using an AIA DEM analysis. In contrast, the XRT Al-poly/Be-thin filter ratio gives lower temperatures for the quiescent and flaring phases. We show that this is due to the sensitivity of this ratio to low temperatures, as the XRT filter ratios predicted with a DEM analysis based on EIS and AIA give values in good agreement with the observed ones. Title: Diagnostics of non-Maxwellian electron distributions in solar active regions from Fe XII lines observed by Hinode/EIS and IRIS Authors: Del Zanna, G.; Polito, V.; Dudík, J.; Testa, P.; Mason, H. E.; Dzifčáková, E. Bibcode: 2022arXiv220707026D Altcode: We present joint Hinode/EIS and IRIS observations of Fe XII lines in active regions, both on-disk and off-limb. We use an improved calibration for the EIS data, and find that the 192.4 A / 1349 A observed ratio is consistent with the values predicted by CHIANTI and the coronal approximation in quiescent areas, but not in all active region observations, where the ratio is often lower than expected by up to a factor of about two. We investigate a number of physical mechanisms that could affect this ratio, such as opacity and absorption from cooler material. We find significant opacity in the EIS Fe XII 193 and 195 A lines, but not in the 192.4 A line, in agreement with previous findings. As we cannot rule out possible EUV absorption by H, He and He II in the on-disk observations, we focus on an off-limb observation where such absorption is minimal. After considering these, as well as possible non-equilibrium effects, we suggest that the most likely explanation for the observed low Fe XII 192.4 A / 1349 A ratio is the presence of non-Maxwellian electron distributions in the active regions. This is in agreement with previous findings based on EIS and IRIS observations independently. Title: Diagnostics of Non-Maxwellian Electron Distributions in Solar Active Regions from Fe XII Lines Observed by the Hinode Extreme Ultraviolet Imaging Spectrometer and Interface Region Imaging Spectrograph Authors: Del Zanna, G.; Polito, V.; Dudík, J.; Testa, P.; Mason, H. E.; Dzifčáková, E. Bibcode: 2022ApJ...930...61D Altcode: We present joint Hinode Extreme Ultraviolet Imaging Spectrometer (EIS) and Interface Region Imaging Spectrograph (IRIS) observations of Fe XII lines in active regions, both on-disk and off-limb. We use an improved calibration for the EIS data, and find that the 192.4 Å/1349 Å observed ratio is consistent with the values predicted by CHIANTI and the coronal approximation in quiescent areas, but not in all active-region observations, where the ratio is often lower than expected by up to a factor of about two. We investigate a number of physical mechanisms that could affect this ratio, such as opacity and absorption from cooler material. We find significant opacity in the EIS Fe XII 193 and 195 Å lines, but not in the 192.4 Å line, in agreement with previous findings. As we cannot rule out possible EUV absorption by H, He, and He II in the on-disk observations, we focus on an off-limb observation where such absorption is minimal. After considering these, as well as possible nonequilibrium effects, we suggest that the most likely explanation for the observed low Fe XII 192.4 Å/1349 Å ratio is the presence of non-Maxwellian electron distributions in the active regions. This is in agreement with previous findings based on EIS and IRIS observations independently. Title: The centre-to-limb variation of non-thermal velocities using IRIS Si IV Authors: Rao, Yamini K.; Del Zanna, Giulio; Mason, Helen E. Bibcode: 2022MNRAS.511.1383R Altcode: 2022arXiv220107290R; 2022MNRAS.tmp..149R We study the non-thermal velocities in the quiet Sun using various high spatial, temporal, and spectral resolution observations from the Interface Region Imaging Spectrograph (IRIS). We focus our analysis on the transition region using the optically thin line (Si IV 1393.7 Å), and select line profiles that are nearly Gaussian. We find evidence of a centre-to-limb variation using different observations having different exposure times, ranging from 5 to 30 s. The distribution of non-thermal velocities close to the limb is observed to peak around 20 km s-1 while the disc observations show a peak around 15 km s-1. The distributions are also different. The overall variation in the non-thermal velocities are correlated with the intensity of the line, as found previously. The on-disc velocities are smaller than most previous observations. In general, we find that the non-thermal velocities are independent of the selected exposure times. The Si IV lines did not seem to exhibit any significant opacity effects. We conclude that these Doppler motions are mostly transverse to the radial direction. The possibility of swaying/torsional motions leading to such variations are validated from these IRIS observations. Title: Preliminary Results from the Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) Authors: Winebarger, Amy; Savage, Sabrina; Kobayashi, Ken; Champey, Patrick; Golub, Leon; Walsh, Robert; Athiray, P. S.; Bradshaw, Stephen; Cheimets, Peter; Cirtain, Jonathan; DeLuca, Edward; Del Zanna, Giulio; Mason, Helen; McKenzie, David; Ramsey, Brian; Reeves, Katharine; Testa, Paola; Vigil, Genevieve; Warren, Harry Bibcode: 2021AGUFMSH51A..06W Altcode: Coronal heating mechanisms are notoriously difficult to constrain with current observations. We present new observations from an instrument designed to measure a critical diagnostic of the frequency heating events in active regions. The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) is a sounding rocket mission that aims to observe the soft x-ray solar spectrum (0.6 2.5 nm) with both spatial and spectral resolution. This wavelength range has several high temperature and abundance diagnostics that can be used to infer the coronal heating frequency. MaGIXS will observe the Sun through a 12 x 33 slot, producing ``overlappograms, where the spatial and spectral information are overlapped and must be unfolded. In this presentation, I will report on the MaGIXS launch and data collection and provide preliminary analysis of MaGIXS observations. Title: Evolution of Elemental Abundances during B-Class Solar Flares: Soft X-Ray Spectral Measurements with Chandrayaan-2 XSM Authors: Mondal, Biswajit; Sarkar, Aveek; Vadawale, Santosh V.; Mithun, N. P. S.; Janardhan, P.; Del Zanna, Giulio; Mason, Helen E.; Mitra-Kraev, Urmila; Narendranath, S. Bibcode: 2021ApJ...920....4M Altcode: 2021arXiv210707825M The Solar X-ray Monitor (XSM) payload on board Chandrayaan-2 provides disk-integrated solar spectra in the 1-15 keV energy range with an energy resolution of 180 eV (at 5.9 keV) and a cadence of 1 s. During the period from 2019 September to 2020 May, covering the minimum of Solar Cycle 24, it observed nine B-class flares ranging from B1.3 to B4.5. Using time-resolved spectroscopic analysis during these flares, we examined the evolution of temperature, emission measure, and absolute elemental abundances of four elements-Mg, Al, Si, and S. These are the first measurements of absolute abundances during such small flares and this study offers a unique insight into the evolution of absolute abundances as the flares evolve. Our results demonstrate that the abundances of these four elements decrease toward their photospheric values during the peak phase of the flares. During the decay phase, the abundances are observed to quickly return to their preflare coronal values. The depletion of elemental abundances during the flares is consistent with the standard flare model, suggesting the injection of fresh material into coronal loops as a result of chromospheric evaporation. To explain the quick recovery of the so-called coronal "First Ionization Potential bias" we propose two scenarios based on the Ponderomotive force model. Title: Thermodynamic evolution of a sigmoidal active region with associated flares Authors: Mulay, Sargam M.; Tripathi, Durgesh; Mason, Helen Bibcode: 2021MNRAS.504.1201M Altcode: 2021MNRAS.tmp..832M; 2021arXiv210309561M Active regions often show S-shaped structures in the corona called sigmoids. These are highly sheared and twisted loops formed along the polarity inversion line. They are considered to be one of the best pre-eruption signatures for CMEs. Here, we investigate the thermodynamic evolution of an on-disc sigmoid observed during 2015 December 24-28. For this purpose, we have employed Emission Measure (EM) and filter-ratio techniques on the observations recorded by the Atmospheric Imaging Assembly (AIA) on-board the Solar Dynamics Observatory (SDO) and X-ray Telescope (XRT) on-board Hinode. The EM analysis showed multithermal plasma along the sigmoid and provided a peak temperature of ~10-12.5 MK for all observed flares. The sigmoidal structure showed emission from Fe XVIII (93.93 Å) and Fe XXI (128.75 Å) lines in the AIA 94 and 131 Å channels, respectively. Our results show that the hot plasma is often confined to very hot strands. The temperature obtained from the EM analysis was found to be in good agreement with that obtained using the XRT, AIA, and GOES filter-ratio methods. These results provide important constraints for the thermodynamic modelling of sigmoidal structures in the core of active regions. Moreover, this study also benchmarks different techniques available for temperature estimation in solar coronal structures. Title: High resolution soft X-ray spectroscopy and the quest for the hot (5-10 MK) plasma in solar active regions Authors: Del Zanna, Giulio; Andretta, Vincenzo; Cargill, Peter J.; Corso, Alain J.; Daw, Adrian N.; Golub, Leon; Klimchuk, James A.; Mason, Helen E. Bibcode: 2021FrASS...8...33D Altcode: 2021arXiv210306156D We discuss the diagnostics available to study the 5--10 MK plasma in the solar corona, which is key to understanding the heating in the cores of solar active regions. We present several simulated spectra, and show that excellent diagnostics are available in the soft X-rays, around 100 Angstroms, as six ionisation stages of Fe can simultaneously be observed, and electron densities derived, within a narrow spectral region. As this spectral range is almost unexplored, we present an analysis of available and simulated spectra, to compare the hot emission with the cooler component. We adopt recently designed multilayers to present estimates of count rates in the hot lines, with a baseline spectrometer design. Excellent count rates are found, opening up the exciting opportunity to obtain high-resolution spectroscopy of hot plasma. Title: 'We love STEAM!' Authors: Mason, Helen; Schell, Helen Bibcode: 2021A&G....62.1.26M Altcode: Helen Mason and Helen Schell explain how the SunSpaceArt outreach programme flourished in 2020, bringing art and science together for pupils and teachers Title: Electron Densities in the Solar Corona Measured Simultaneously in the Extreme Ultraviolet and Infrared Authors: Dudík, Jaroslav; Del Zanna, Giulio; Rybák, Ján; Lörinčík, Juraj; Dzifčáková, Elena; Mason, Helen E.; Tomczyk, Steven; Galloy, Michael Bibcode: 2021ApJ...906..118D Altcode: 2020arXiv201109175D Accurate measurements of electron density are critical for determination of the plasma properties in the solar corona. We compare the electron densities diagnosed from Fe XIII lines observed by the Extreme-Ultraviolet Imaging Spectrometer (EIS) onboard the Hinode mission with the near-infrared (NIR) measurements provided by the ground-based Coronal Multichannel Polarimeter (CoMP). To do that, the emissivity-ratio method based on all available observed lines of Fe XIII is used for both EIS and CoMP. The EIS diagnostics is further supplemented by the results from Fe XII lines. We find excellent agreement, within 10%, between the electron densities measured from both extreme-ultraviolet and NIR lines. In the five regions selected for detailed analysis, we obtain electron densities of log(Ne [cm-3]) = 8.2-8.6. Where available, the background subtraction has a significant impact on the diagnostics, especially on the NIR lines, where the loop contributes less than a quarter of the intensity measured along the line of sight. For the NIR lines, we find that the line center intensities are not affected by stray light within the instrument, and recommend using these for density diagnostics. The measurements of the Fe XIII NIR lines represent a viable method for density diagnostics using ground-based instrumentation. Title: Study of the spatial association between an active region jet and a nonthermal type~${\rm III}$ radio burst Authors: Mulay, Sargam M.; Sharma, Rohit; Valori, Gherardo; Vásquez, Alberto M.; Del Zanna, Giulio; Mason, Helen; Oberoi, Divya Bibcode: 2020arXiv200914581M Altcode: We aim to investigate the spatial location of the source of an active region (AR) jet and its relation with associated nonthermal type~III radio emission. An emission measure (EM) method was used to study the thermodynamic nature of the AR jet. The nonthermal type~{\rm III} radio burst observed at meterwavelength was studied using the Murchison Widefield Array (MWA) radio imaging and spectroscopic data. The local configuration of the magnetic field and the connectivity of the source region of the jet with open magnetic field structures was studied using a nonlinear force-free field (NLFFF) extrapolation and potential field source surface (PFSS) extrapolation respectively. The plane-of-sky velocity of the AR jet was found to be $\sim$136~km/s. The EM analysis confirmed the presence of low temperature 2~MK plasma for the spire, whereas hot plasma, between 5-8 MK, was present at the footpoint region which also showed the presence of Fe~{\sc xviii} emission. A lower limit on the electron number density was found to be 1.4$\times$10$^{8}$ cm$^{-3}$ for the spire and 2.2$\times$10$^{8}$~cm$^{-3}$ for the footpoint. A temporal and spatial correlation between the AR jet and nonthermal type III burst confirmed the presence of open magnetic fields. An NLFFF extrapolation showed that the photospheric footpoints of the null point were anchored at the location of the source brightening of the jet. The spatial location of the radio sources suggests an association with the extrapolated closed and open magnetic fields although strong propagation effects are also present. The multi-scale analysis of the field at local, AR, and solar scales confirms the interlink between different flux bundles involved in the generation of the type III radio signal with flux transferred from a small coronal hole to the periphery of the sunspot via null point reconnection with an emerging structure. Title: Plasma Diagnostics from Active Region and Quiet-Sun Spectra Observed by Hinode/EIS: Quantifying the Departures from a Maxwellian Distribution Authors: Lörinčík, Juraj; Dudík, Jaroslav; del Zanna, Giulio; Dzifčáková, Elena; Mason, Helen E. Bibcode: 2020ApJ...893...34L Altcode: 2020arXiv200307091L We perform plasma diagnostics, including that of the non-Maxwellian κ-distributions, in several structures observed in the solar corona by the Extreme-Ultraviolet Imaging Spectrometer (EIS) on board the Hinode spacecraft. To prevent uncertainties due to the in-flight calibration of EIS, we selected spectral atlases observed shortly after the launch of the mission. One spectral atlas contains an observation of an active region, while the other is an off-limb quiet-Sun region. To minimize the uncertainties of the diagnostics, we rely only on strong lines and average the signal over a spatial area within selected structures. Multiple plasma parameters are diagnosed, such as the electron density, the differential emission measure, and the non-Maxwellian parameter κ. To do that, we use a simple, well-converging iterative scheme based on refining the initial density estimates via the differential emission measure (DEM) and κ. We find that while the quiet-Sun spectra are consistent with a Maxwellian distribution, the coronal loops and moss observed within the active region are strongly non-Maxwellian with κ ⪅ 3. These results were checked by calculating synthetic ratios using DEMs obtained as a function of κ. Ratios predicted using the DEMs assuming κ-distributions converged to the ratios observed in the quiet Sun and coronal loops. To our knowledge, this work presents a strong evidence of the presence of different electron distributions between two physically distinct parts of the solar corona. Title: Study of the spatial association between an active region jet and a nonthermal type III radio burst Authors: Mulay, Sargam M.; Sharma, Rohit; Valori, Gherardo; Vásquez, Alberto M.; Del Zanna, Giulio; Mason, Helen; Oberoi, Divya Bibcode: 2019A&A...632A.108M Altcode:
Aims: We aim to investigate the spatial location of the source of an active region (AR) jet and its relation with associated nonthermal type III radio emission.
Methods: An emission measure (EM) method was used to study the thermodynamic nature of the AR jet. The nonthermal type III radio burst observed at meterwavelength was studied using the Murchison Widefield Array (MWA) radio imaging and spectroscopic data. The local configuration of the magnetic field and the connectivity of the source region of the jet with open magnetic field structures was studied using a nonlinear force-free field (NLFFF) extrapolation and potential field source surface (PFSS) extrapolation respectively.
Results: The plane-of-sky velocity of the AR jet was found to be ∼136 km s-1. The EM analysis confirmed the presence of low temperature 2 MK plasma for the spire, whereas hot plasma, between 5 and 8 MK, was present at the footpoint region which also showed the presence of Fe XVIII emission. A lower limit on the electron number density was found to be 1.4 × 108 cm-3 for the spire and 2.2 × 108 cm-3 for the footpoint. A temporal and spatial correlation between the AR jet and nonthermal type III burst confirmed the presence of open magnetic fields. An NLFFF extrapolation showed that the photospheric footpoints of the null point were anchored at the location of the source brightening of the jet. The spatial location of the radio sources suggests an association with the extrapolated closed and open magnetic fields although strong propagation effects are also present.
Conclusions: The multi-scale analysis of the field at local, AR, and solar scales confirms the interlink between different flux bundles involved in the generation of the type III radio signal with flux transferred from a small coronal hole to the periphery of the sunspot via null point reconnection with an emerging structure.

The movie associated to Fig. 4 is available at https://www.aanda.org Title: Hinode EIS line widths in the quiet corona up to 1.5 R⊙ Authors: Del Zanna, G.; Gupta, G. R.; Mason, H. E. Bibcode: 2019A&A...631A.163D Altcode: 2019arXiv190509783D We present an analysis of several Hinode Extreme-ultraviolet Imaging Spectrometer (EIS) observations of coronal line widths in the quiet Sun, up to 1.5 R⊙ radial distances. Significant variations are found, which indicates no damping of Alfvén waves in the quiescent corona. However, the uncertainties in estimating the instrumental width mean that a firm conclusion cannot be reached. We present a discussion of various EIS instrumental issues and suggest that the strongest lines, from Fe XII at 193.5 Å and 195.1 Å, have anomalous instrumental widths. We also show how line widths in EIS are uncertain when the signal is low, and that the instrumental variation along the slit is also uncertain. We also find an anomalous decrease (up to 40%) in the intensities of these lines in many off-limb and active region observations, and provide evidence that this is due to opacity effects. We find that the most reliable measurements are obtained from the weaker lines. Title: Exploring the damping of Alfvén waves along a long off-limb coronal loop, up to 1.4 R⊙ Authors: Gupta, G. R.; Del Zanna, G.; Mason, H. E. Bibcode: 2019A&A...627A..62G Altcode: 2019arXiv190508194G The Alfvén wave energy flux in the corona can be explored using the electron density and velocity amplitude of the waves. The velocity amplitude of Alfvén waves can be obtained from the non-thermal velocity of spectral line profiles. Previous calculations of the Alfvén wave energy flux with height in active regions and polar coronal holes have provided evidence for the damping of Alfvén waves with height. We present off-limb Hinode Extreme-ultraviolet Imaging Spectrometer (EIS) observations of a long coronal loop up to 1.4 R⊙. We obtained the electron density along the loop and found the loop to be almost in hydrostatic equilibrium. We obtained the temperature using the emission measure-loci (EM-loci) method and found the loop to be isothermal across, as well as along, the loop with a temperature of about 1.37 MK. We significantly improve the estimate of non-thermal velocities over previous studies by using the estimated ion (equal to electron) temperature. Estimates of electron densities are improved using the significant updates of the CHIANTI v.8 atomic data. More accurate measurements of propagating Alfvén wave energy along the coronal loop and its damping are presented up to distances of 1.4 R⊙, further than have been previously explored. The Alfvén wave energy flux obtained could contribute to a significant part of the coronal losses due to radiation along the loop. Title: Signatures of the non-Maxwellian κ-distributions in optically thin line spectra. II. Synthetic Fe XVII-XVIII X-ray coronal spectra and predictions for the Marshall Grazing-Incidence X-ray Spectrometer (MaGIXS) Authors: Dudík, Jaroslav; Dzifčáková, Elena; Del Zanna, Giulio; Mason, Helen E.; Golub, Leon L.; Winebarger, Amy R.; Savage, Sabrina L. Bibcode: 2019A&A...626A..88D Altcode: 2019arXiv190510356D
Aims: We investigated the possibility of diagnosing the degree of departure from the Maxwellian distribution using the Fe XVII-Fe XVIII spectra originating in plasmas in collisional ionization equilibrium, such as in the cores of solar active regions or microflares.
Methods: The original collision strengths for excitation are integrated over the non-Maxwellian electron κ-distributions characterized by a high-energy tail. Synthetic X-ray emission line spectra were calculated for a range of temperatures and κ. We focus on the 6-24 Å spectral range to be observed by the upcoming Marshall Grazing-Incidence X-ray Spectrometer MaGIXS.
Results: We find that many line intensity ratios are sensitive to both T and κ. Best diagnostic options are provided if a ratio involving both Fe XVII and Fe XVIII is combined with another ratio involving lines formed within a single ion. The sensitivity of such diagnostics to κ is typically a few tens of per cent. Much larger sensitivity, of about a factor of two to three, can be obtained if the Fe XVIII 93.93 Å line observed by SDO/AIA is used in conjuction with the X-ray lines.
Conclusions: We conclude that the MaGIXS instrument is well-suited for detection of departures from the Maxwellian distribution, especially in active region cores. Title: Flare-related Recurring Active Region Jets: Evidence for Very Hot Plasma Authors: Mulay, Sargam M.; Matthews, Sarah; Hasegawa, Takahiro; Del Zanna, Giulio; Mason, Helen; Shimizu, Toshifumi Bibcode: 2018SoPh..293..160M Altcode: We present a study of two active region jets (AR jets) that are associated with two C-class X-ray flares. The recurrent, homologous jets originated from the northern periphery of a sunspot. We confirm flare-like temperatures at the footpoints of these jets using spectroscopic observations of Fe XXIII (263.76 Å) and Fe XXIV (255.11 Å) emission lines. The emission measure loci method was used to obtain an isothermal temperature, and the results show a decrease (17.7 to 13.6 MK) in the temperature during the decay phase of the C 3.0 flare. The electron number densities at the footpoints were found to range from 1.7 ×1010 to 2.0 ×1011cm−3 using the Fe XIV line pair ratio. Nonthermal velocities were found to range from 34 - 100 km/s for Fe XXIV and 51 - 89 km/s for Fe XXIII. The plane-of-sky velocities were calculated to be 462 ±21 and 228 ±23 km/s for the two jets using the Atmospheric Imaging Assembly (AIA) 171 Å channel. The AIA light curves of the jet footpoint regions confirmed the temporal and spatial correlation between the two X-ray flares and the jet footpoint emission. The Gamma-ray Burst Monitor (GBM) also confirmed superhot plasma of 27 (25) MK with a nonthermal energy of 2.38 ×1026 (2.87 ×1027) ergs−1 in the jet footpoint region during the rise (peak) phase of one of the flares. The temperatures of the jet footpoint regions obtained from EIS agree very well (within an uncertainty of 20%) with temperatures obtained from the Geostationary Environmental Operational Satellite (GOES) flux ratios. These results provide clear evidence for very hot plasma (>10 MK) at the footpoints of the flare-related jets, and they confirm the heating and cooling of the plasma during the flares. Title: Solar UV and X-ray spectral diagnostics Authors: Del Zanna, Giulio; Mason, Helen E. Bibcode: 2018LRSP...15....5D Altcode: 2018arXiv180901618D X-ray and ultraviolet (UV) observations of the outer solar atmosphere have been used for many decades to measure the fundamental parameters of the solar plasma. This review focuses on the optically thin emission from the solar atmosphere, mostly found at UV and X-ray (XUV) wavelengths, and discusses some of the diagnostic methods that have been used to measure electron densities, electron temperatures, differential emission measure (DEM), and relative chemical abundances. We mainly focus on methods and results obtained from high-resolution spectroscopy, rather than broad-band imaging. However, we note that the best results are often obtained by combining imaging and spectroscopic observations. We also mainly focus the review on measurements of electron densities and temperatures obtained from single ion diagnostics, to avoid issues related to the ionisation state of the plasma. We start the review with a short historical introduction on the main XUV high-resolution spectrometers, then review the basics of optically thin emission and the main processes that affect the formation of a spectral line. We mainly discuss plasma in equilibrium, but briefly mention non-equilibrium ionisation and non-thermal electron distributions. We also summarise the status of atomic data, which are an essential part of the diagnostic process. We then review the methods used to measure electron densities, electron temperatures, the DEM, and relative chemical abundances, and the results obtained for the lower solar atmosphere (within a fraction of the solar radii), for coronal holes, the quiet Sun, active regions and flares. Title: The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) Authors: Winebarger, A. R.; Savage, S. L.; Kobayashi, K.; Champey, P. R.; McKenzie, D. E.; Golub, L.; Testa, P.; Reeves, K.; Cheimets, P.; Cirtain, J. W.; Walsh, R. W.; Bradshaw, S. J.; Warren, H.; Mason, H. E.; Del Zanna, G. Bibcode: 2017AGUFMSH44A..06W Altcode: For over four decades, X-ray, EUV, and UV spectral observations have been used to measure physical properties of the solar atmosphere. At wavelengths below 10 nm, however, observations of the solar corona with simultaneous spatial and spectral resolution are limited, and not since the late 1970's have spatially resolved solar X-ray spectra been measured. Because the soft X-ray regime is dominated by emission lines formed at high temperatures, X-ray spectroscopic techniques yield insights to fundamental physical processes that are not accessible by any other means. Using a novel implementation of corrective optics, the Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) will measure, for the first time, the solar spectrum from 0.6- 2.4 nm with a 6 arcsec resolution over an 8 arcmin slit. The MaGIXS mission will address on of the fundamental problems of coronal physics: the nature of coronal heating. There are several observables in the MaGIXS wavelength range that will constrain the heating frequency and hence discriminate between competing coronal heating theories. In this presentation, we will present the MaGIXS scientific motivation and provide an update on instrument development. MaGIXS will be launched from White Sands Missile Range in the summer of 2019. Title: Non-thermal distributions and energy transport in the solar flares Authors: Matthews, Sarah; del Zanna, Guilio; Calcines, Ariadna; Mason, Helen; Mathioudakis, Mihalis; Culhane, Len; Harra, Louise; van Driel-Gesztelyi, Lidia; Green, Lucie; Long, David; Baker, Deb; Valori, Gherardo Bibcode: 2017arXiv171200773M Altcode: Determining the energy transport mechanisms in flares remains a central goal in solar flares physics that is still not adequately answered by the 'standard flare model'. In particular, the relative roles of particles and/or waves as transport mechanisms, the contributions of low energy protons and ions to the overall flare budget, and the limits of low energy non-thermal electron distribution are questions that still cannot be adequately reconciled with current instrumentation. In this 'White Paper' submitted in response to the call for inputs to the Next Generation Solar Physics Mission review process initiated by JAXA, NASA and ESA in 2016, we outline the open questions in this area and possible instrumentation that could provide the required observations to help answer these and other flare-related questions. Title: Cool and hot emission in a recurring active region jet Authors: Mulay, Sargam M.; Del Zanna, Giulio; Mason, Helen Bibcode: 2017A&A...606A...4M Altcode:
Aims: We present a thorough investigation of the cool and hot temperature components in four recurring active region jets observed on July 10, 2015 using the Atmospheric Imaging Assembly (AIA), X-ray Telescope (XRT), and Interface Region Imaging Spectrograph (IRIS) instruments.
Methods: A differential emission measure (DEM) analysis was performed on areas in the jet spire and footpoint regions by combining the IRIS spectra and the AIA observations. This procedure better constrains the low temperature DEM values by adding IRIS spectral lines. Plasma parameters, such as Doppler velocities, electron densities, nonthermal velocities and a filling factor were also derived from the IRIS spectra.
Results: In the DEM analysis, significant cool emission was found in the spire and the footpoint regions. The hot emission was peaked at log T [K] = 5.6-5.9 and 6.5 respectively. The DEM curves show the presence of hot plasma (T = 3 MK) in the footpoint region. We confirmed this result by estimating the Fe XVIII emission from the AIA 94 Å channel which was formed at an effective temperature of log T [K] = 6.5. The average XRT temperatures were also found to be in agreement with log T [K] = 6.5. The emission measure (EM) was found to be three orders of magnitude higher in the AIA-IRIS DEM compared with that obtained using only AIA. The O IV (1399/1401 Å) electron densities were found to be 2.0×1010 cm-3 in the spire and 7.6 × 1010 cm-3 in the footpoint. Different threads along the spire show different plane-of-sky velocities both in the lower corona and transition region. Doppler velocities of 32 km s-1 (blueshifted) and 13 km s-1 (redshifted) were obtained in the spire and footpoint, respectively from the Si IV 1402.77 Å spectral line. Nonthermal velocities of 69 and 53 km s-1 were recorded in the spire and footpoint region, respectively. We obtained a filling factor of 0.1 in the spire at log T [K] = 5.
Conclusions: The recurrent jet observations confirmed the presence of significant cool emission co-spatial with the coronal emission.

The movie attached to Fig. 3 is available at http://www.aanda.org Title: Spectroscopy of Very Hot Plasma in Non-flaring Parts of a Solar Limb Active Region: Spatial and Temporal Properties Authors: Parenti, Susanna; del Zanna, Giulio; Petralia, Antonino; Reale, Fabio; Teriaca, Luca; Testa, Paola; Mason, Helen E. Bibcode: 2017ApJ...846...25P Altcode: 2017arXiv170708445P In this work we investigate the thermal structure of an off-limb active region (AR) in various non-flaring areas, as it provides key information on the way these structures are heated. In particular, we concentrate on the very hot component (> 3 {MK}) as it is a crucial element to distinguish between different heating mechanisms. We present an analysis using Fe and Ca emission lines from both the Solar Ultraviolet Measurement of Emitted Radiation (SUMER) on board the Solar and Heliospheric Observatory (SOHO) and the EUV Imaging Spectrometer (EIS) on board Hinode. A data set covering all ionization stages from Fe x to Fe xix has been used for the thermal analysis (both differential emission measure and emission measure, EM). Ca xiv is used for the SUMER-EIS radiometric cross calibration. We show that the very hot plasma is present and persistent almost everywhere in the core of the limb AR. The off-limb AR is clearly structured in Fe xviii. Almost everywhere, the EM analysis reveals plasma at 10 MK (visible in Fe xix emission), which is down to 0.1% of EM of the main 3 {MK} plasma. We estimate the power-law index of the hot tail of the EM to be between -8.5 and -4.4. However, the question about the possible existence of a small minor peak at around 10 {MK} remains open. The absence in some part of the AR of the Fe xix and Fe xxiii lines (which fall into our spectral range) enables us to determine an upper limit on the EM at these temperatures. Our results include a new Ca xiv 943.59 Å atomic model. Title: Nonequilibrium Processes in the Solar Corona, Transition Region, Flares, and Solar Wind (Invited Review) Authors: Dudík, Jaroslav; Dzifčáková, Elena; Meyer-Vernet, Nicole; Del Zanna, Giulio; Young, Peter R.; Giunta, Alessandra; Sylwester, Barbara; Sylwester, Janusz; Oka, Mitsuo; Mason, Helen E.; Vocks, Christian; Matteini, Lorenzo; Krucker, Säm; Williams, David R.; Mackovjak, Šimon Bibcode: 2017SoPh..292..100D Altcode: 2017arXiv170603396D We review the presence and signatures of the non-equilibrium processes, both non-Maxwellian distributions and non-equilibrium ionization, in the solar transition region, corona, solar wind, and flares. Basic properties of the non-Maxwellian distributions are described together with their influence on the heat flux as well as on the rates of individual collisional processes and the resulting optically thin synthetic spectra. Constraints on the presence of high-energy electrons from observations are reviewed, including positive detection of non-Maxwellian distributions in the solar corona, transition region, flares, and wind. Occurrence of non-equilibrium ionization is reviewed as well, especially in connection to hydrodynamic and generalized collisional-radiative modeling. Predicted spectroscopic signatures of non-equilibrium ionization depending on the assumed plasma conditions are summarized. Finally, we discuss the future remote-sensing instrumentation that can be used for the detection of these non-equilibrium phenomena in various spectral ranges. Title: Analysis and modelling of recurrent solar flares observed with Hinode/EIS on March 9, 2012 Authors: Polito, V.; Del Zanna, G.; Valori, G.; Pariat, E.; Mason, H. E.; Dudík, J.; Janvier, M. Bibcode: 2017A&A...601A..39P Altcode: 2016arXiv161203504P Three homologous C-class flares and one last M-class flare were observed by both the Solar Dynamics Observatory (SDO) and the Hinode EUV Imaging Spectrometer (EIS) in the AR 11429 on March 9, 2012. All the recurrent flares occurred within a short interval of time (less than 4 h), showed very similar plasma morphology and were all confined, until the last one when a large-scale eruption occurred. The C-class flares are characterized by the appearance, at approximatively the same locations, of two bright and compact footpoint sources of ≈3-10 MK evaporating plasma, and a semi-circular ribbon. During all the flares, the continuous brightening of a spine-like hot plasma (≈10 MK) structure is also observed. Spectroscopic observations with Hinode/EIS are used to measure and compare the blueshift velocities in the Fe xxiii emission line and the electron number density at the flare footpoints for each flare. Similar velocities, of the order of 150-200 km s-1, are observed during the C2.0 and C4.7 confined flares, in agreement with the values reported by other authors in the study of the last M1.8 class flare. On the other hand, lower electron number densities and temperatures tend to be observed in flares with lower peak soft X-ray flux. In order to investigate the homologous nature of the flares, we performed a non-linear force-free field (NLFFF) extrapolation of the 3D magnetic field configuration in the corona. The NLFFF extrapolation and the Quasi-Separatrix Layers (QSLs) provide the magnetic field context which explains the location of the kernels, spine-like hot plasma and semi-circular brightenings observed in the (non-eruptive) flares. Given the absence of a coronal null point, we argue that the homologous flares were all generated by the continuous recurrence of bald patch reconnection.

The movie associated to Fig. 2 is available at http://www.aanda.org Title: Fan Loops Observed by IRIS, EIS, and AIA Authors: Ghosh, Avyarthana; Tripathi, Durgesh; Gupta, G. R.; Polito, Vanessa; Mason, Helen E.; Solanki, Sami K. Bibcode: 2017ApJ...835..244G Altcode: 2017arXiv170101617G A comprehensive study of the physical parameters of active region fan loops is presented using the observations recorded with the Interface Region Imaging Spectrometer (IRIS), the EUV Imaging Spectrometer (EIS) on board Hinode, and the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). The fan loops emerging from non-flaring AR 11899 (near the disk center) on 2013 November 19 are clearly discernible in AIA 171 Å images and in those obtained in Fe viii and Si vii images using EIS. Our measurements of electron densities reveal that the footpoints of these loops are at an approximately constant pressure with electron densities of {log} {N}e=10.1 cm-3 at {log} [T/K]=5.15 (O IV), and {log} {N}e=8.9 cm-3 at {log} [T/K]=6.15 (Si x). The electron temperature diagnosed across the fan loops by means of EM-Loci suggest that two temperature components exist at {log} [T/K]=4.95 and 5.95 at the footpoints. These components are picked up by IRIS lines and EIS lines, respectively. At higher heights, the loops are nearly isothermal at {log} [T/K]=5.95, which remained constant along the loop. The measurement of the Doppler shift using IRIS lines suggests that the plasma at the footpoints of these loops is predominantly redshifted by 2-3 km s-1 in C II, 10-15 km s-1 in Si IV, and 15-20 km s-1 in O IV, reflecting the increase in the speed of downflows with increasing temperature from {log} [T/K]=4.40 to 5.15. These observations can be explained by low-frequency nanoflares or impulsive heating, and provide further important constraints on the modeling of the dynamics of fan loops. Title: Temperature and density structure of a recurring active region jet Authors: Mulay, Sargam M.; Del Zanna, Giulio; Mason, Helen Bibcode: 2017A&A...598A..11M Altcode: 2016arXiv160908472M
Aims: We present a study of a recurring jet observed on October 31, 2011 by the Atmosphereic Imaging Assembly (AIA) on board the Solar Dynamic Observatory, the X-ray Telescope (XRT) and EUV Imaging Spectrometer (EIS) on board Hinode. We discuss the physical parameters of the jet that are obtained using imaging and spectroscopic observations, such as density, differential emission measure, peak temperature, velocity, and filling factor.
Methods: A differential emission measure (DEM) analysis was performed at the region of the jet spire and the footpoint using EIS observations and also by combining AIA and XRT observations. The resulting EIS DEM curves were compared to those obtained with AIA-XRT. The DEM curves were used to create synthetic spectra with the CHIANTI atomic database. The predicted total count rates for each AIA channel were compared with the observed count rates. The effects of varying elemental abundances and the temperature range for the DEM inversion were investigated. Spectroscopic diagnostics were used to obtain an electron number density distribution for the jet spire and the jet footpoint.
Results: The plasma along the line of sight in the jet spire and jet footpoint was found to be peak at 2.0 MK (log T [K] = 6.3). We calculated electron densities using the Fe XII (λ186/λ195) line ratio in the region of the spire (Ne = 7.6 × 1010 cm-3) and the footpoint (1.1 × 1011 cm-3). The plane-of-sky velocity of the jet is found to be 524 km s-1. The resulting EIS DEM values are in good agreement with those obtained from AIA-XRT. The synthetic spectra contributing to each AIA channel confirms the multi-thermal nature of the AIA channels in both regions. There is no indication of high temperatures, such as emission from Fe XVII (λ254.87) (log T [K] = 6.75) seen in the jet spire. In the case of the jet footpoint, synthetic spectra predict weak contributions from Ca XVII (λ192.85) and Fe XVII (λ254.87). With further investigation, we confirmed emission from the Fe XVIII (93.932 Å) line in the AIA 94 Å channel in the region of the footpoint. We also found good agreement between the estimated and predicted Fe XVIII count rates. A study of the temporal evolution of the jet footpoint and the presence of high-temperature emission from the Fe XVIII (λ93.932) (log T [K] = 6.85) line leads us to conclude that the hot component in the jet footpoint was present initially and that the jet had cooled down by the time EIS observed it.

Two movies attached to Fig. 2 are available at http://www.aanda.org Title: Can the non-Maxwellian kappa-distributions be diagnosed in the solar corona? Authors: Dudík, J.; Dzifcakova, E.; Del Zanna, G.; Mackovjak, Š.; Mason, H. E. Bibcode: 2016AGUFMSH21D2555D Altcode: We report on the search of signatures of the non-Maxwellian kappa-distributions in the emission line spectra of the solar corona. A survey of coronal lines is performed for single-ion and multi-ion diagnostics using ions spanning the temperature range of 0.5 - 6 MK. State-of-art excitation cross-sections are integrated directly to obtain the corresponding non-Maxwellian excitation and deexcitation rates. Ionization and recombination rates are obtained by approximative methods. We find that there are only a few good diagnostic options. This is due to majority of lines being formed from similar energy levels. The best diagnostic options rely on lines formed at different excitation tresholds, i.e., at different wavelengths. This highlights the importance of absolute intensity calibration of space-borne spectrometers. The applicability of these methods is demonstrated on analysis of a dedicated extreme-ultraviolet observations made in the Fe XI-XIII lines by the Hinode/EIS satellite during HOP 226. The observations are performed in an active region containing a filament and several coronal loops. A transient coronal loop appears at the foot of a filament and is preceded by activity within this filament. EIS spectra are used to diagnose the electron density, but also reveal that the transient loop is highly non-Maxwellian, characterized by a kappa=2 distribution. We discuss the methods for separation the non-Maxwellian effects from the effects of plasma multi-thermality arising due to finite spatial resolution, as well as the effect of kappa-distributions on the degree of multithermality diagnosed in various observed coronal features. Title: Solar Coronal Jets: Observations, Theory, and Modeling Authors: Raouafi, N. E.; Patsourakos, S.; Pariat, E.; Young, P. R.; Sterling, A. C.; Savcheva, A.; Shimojo, M.; Moreno-Insertis, F.; DeVore, C. R.; Archontis, V.; Török, T.; Mason, H.; Curdt, W.; Meyer, K.; Dalmasse, K.; Matsui, Y. Bibcode: 2016SSRv..201....1R Altcode: 2016arXiv160702108R; 2016SSRv..tmp...31R Coronal jets represent important manifestations of ubiquitous solar transients, which may be the source of significant mass and energy input to the upper solar atmosphere and the solar wind. While the energy involved in a jet-like event is smaller than that of "nominal" solar flares and coronal mass ejections (CMEs), jets share many common properties with these phenomena, in particular, the explosive magnetically driven dynamics. Studies of jets could, therefore, provide critical insight for understanding the larger, more complex drivers of the solar activity. On the other side of the size-spectrum, the study of jets could also supply important clues on the physics of transients close or at the limit of the current spatial resolution such as spicules. Furthermore, jet phenomena may hint to basic process for heating the corona and accelerating the solar wind; consequently their study gives us the opportunity to attack a broad range of solar-heliospheric problems. Title: Density diagnostics derived from the O iv and S iv intercombination lines observed by IRIS Authors: Polito, V.; Del Zanna, G.; Dudík, J.; Mason, H. E.; Giunta, A.; Reeves, K. K. Bibcode: 2016A&A...594A..64P Altcode: 2016arXiv160705072P The intensity of the O iv 2s2 2p 2P-2s2p24P and S iv 3 s2 3p 2P-3s 3p24 P intercombination lines around 1400 Å observed with the Interface Region Imaging Spectrograph (IRIS) provide a useful tool to diagnose the electron number density (Ne) in the solar transition region plasma. We measure the electron number density in a variety of solar features observed by IRIS, including an active region (AR) loop, plage and brightening, and the ribbon of the 22-June-2015 M 6.5 class flare. By using the emissivity ratios of O iv and S iv lines, we find that our observations are consistent with the emitting plasma being near isothermal (logT[K] ≈ 5) and iso-density (Ne ≈ 1010.6 cm-3) in the AR loop. Moreover, high electron number densities (Ne ≈ 1013 cm-3) are obtained during the impulsive phase of the flare by using the S iv line ratio. We note that the S iv lines provide a higher range of density sensitivity than the O iv lines. Finally, we investigate the effects of high densities (Ne ≳ 1011 cm-3) on the ionization balance. In particular, the fractional ion abundances are found to be shifted towards lower temperatures for high densities compared to the low density case. We also explored the effects of a non-Maxwellian electron distribution on our diagnostic method.

The movie associated to Fig. 3 is available at http://www.aanda.org Title: Multiwavelength study of 20 jets that emanate from the periphery of active regions Authors: Mulay, Sargam M.; Tripathi, Durgesh; Del Zanna, Giulio; Mason, Helen Bibcode: 2016A&A...589A..79M Altcode: 2016arXiv160200151M
Aims: We present a multiwavelength analysis of 20 EUV jets which occurred at the periphery of active regions close to sunspots. We discuss the physical parameters of the jets and their relation with other phenomena such as Hα surges, nonthermal type-III radio bursts and hard X-ray (HXR) emission.
Methods: These jets were observed between August 2010 and June 2013 by the Atmospheric Imaging Assembly (AIA) instrument that is onboard the Solar Dynamic Observatory (SDO). We selected events that were observed on the solar disk within +/-60° latitude. Using AIA wavelength channels that are sensitive to coronal temperatures, we studied the temperature distribution in the jets using the line of sight (LOS) differential emission measure (DEM) technique. We also investigated the role of the photospheric magnetic field using the LOS magnetogram data from the Helioseismic and Magnetic Imager (HMI) onboard SDO.
Results: It has been observed that most of the jets originated from the western periphery of active regions. Their lifetimes range from 5 to 39 min with an average of 18 min and their velocities range from 87 to 532 km s-1 with an average of 271 km s-1. All the jets are co-temporally associated with Hα surges. Most of the jets are co-temporal with nonthermal type-III radio bursts observed by the Wind/WAVES spacecraft in the frequency range from 20 kHz to 13 MHz. We confirm the source region of these bursts using the potential field source surface (PFSS) technique. Using Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) observations, we found that half of the jets produced HXR emission and they often shared the same source region as the HXR emission (6-12 keV). Ten out of 20 events showed that the jets originated in a region of flux cancellation and six jets in a region of flux emergence. Four events showed flux emergence and then cancellation during the jet evolution. DEM analyses showed that for most of the spires of the jets, the DEM peaked at around log T [K] = 6.2/6.3 (~2 MK). In addition, we derived an emission measure and a lower limit of electron density at the location of the spire (jet 1: log EM = 28.6, Ne = 1.3 × 1010 cm-3; jet 2: log EM = 28.0, Ne = 8.6 × 109 cm-3) and the footpoint (jet 1 - log EM = 28.6, Ne = 1.1 × 1010 cm-3; jet 2: log EM = 28.1, Ne = 8.4 × 109 cm-3). These results are in agreement with those obtained earlier by studying individual active region jets.
Conclusions: The observation of flux cancellation, the association with HXR emission and emission of nonthermal type-III radio bursts, suggest that the initiation and therefore, heating is taking place at the base of the jet. This is also supported by the high temperature plasma revealed by the DEM analysis in the jet footpoint (peak in the DEM at log T [K] = 6.5). Our results provide substantial constraints for theoretical modeling of the jets and their thermodynamic nature.

Movies are available in electronic form at http://www.aanda.org Title: Slipping Magnetic Reconnection, Chromospheric Evaporation, Implosion, and Precursors in the 2014 September 10 X1.6-Class Solar Flare Authors: Dudík, Jaroslav; Polito, Vanessa; Janvier, Miho; Mulay, Sargam M.; Karlický, Marian; Aulanier, Guillaume; Del Zanna, Giulio; Dzifčáková, Elena; Mason, Helen E.; Schmieder, Brigitte Bibcode: 2016ApJ...823...41D Altcode: 2016arXiv160306092D We investigate the occurrence of slipping magnetic reconnection, chromospheric evaporation, and coronal loop dynamics in the 2014 September 10 X-class flare. Slipping reconnection is found to be present throughout the flare from its early phase. Flare loops are seen to slip in opposite directions toward both ends of the ribbons. Velocities of 20-40 km s-1 are found within time windows where the slipping is well resolved. The warm coronal loops exhibit expanding and contracting motions that are interpreted as displacements due to the growing flux rope that subsequently erupts. This flux rope existed and erupted before the onset of apparent coronal implosion. This indicates that the energy release proceeds by slipping reconnection and not via coronal implosion. The slipping reconnection leads to changes in the geometry of the observed structures at the Interface Region Imaging Spectrograph slit position, from flare loop top to the footpoints in the ribbons. This results in variations of the observed velocities of chromospheric evaporation in the early flare phase. Finally, it is found that the precursor signatures, including localized EUV brightenings as well as nonthermal X-ray emission, are signatures of the flare itself, progressing from the early phase toward the impulsive phase, with the tether-cutting being provided by the slipping reconnection. The dynamics of both the flare and outlying coronal loops is found to be consistent with the predictions of the standard solar flare model in three dimensions. Title: The CHIANTI atomic database Authors: Young, P. R.; Dere, K. P.; Landi, E.; Del Zanna, G.; Mason, H. E. Bibcode: 2016JPhB...49g4009Y Altcode: 2015arXiv151205620Y The freely available CHIANTI atomic database was first released in 1996 and has had a huge impact on the analysis and modeling of emissions from astrophysical plasmas. It contains data and software for modeling optically thin atom and positive ion emission from low density (≲1013 cm-3) plasmas from x-ray to infrared wavelengths. A key feature is that the data are assessed and regularly updated, with version 8 released in 2015. Atomic data for modeling the emissivities of 246 ions and neutrals are contained in CHIANTI, together with data for deriving the ionization fractions of all elements up to zinc. The different types of atomic data are summarized here and their formats discussed. Statistics on the impact of CHIANTI to the astrophysical community are given and examples of the diverse range of applications are presented. Title: Simultaneous IRIS and Hinode/EIS Observations and Modelling of the 2014 October 27 X2.0 Class Flare Authors: Polito, V.; Reep, J. W.; Reeves, K. K.; Simões, P. J. A.; Dudík, J.; Del Zanna, G.; Mason, H. E.; Golub, L. Bibcode: 2016ApJ...816...89P Altcode: 2015arXiv151206378P We present a study of the X2-class flare which occurred on 2014 October 27 and was observed with the Interface Region Imaging Spectrograph (IRIS) and the EUV Imaging Spectrometer (EIS) on board the Hinode satellite. Thanks to the high cadence and spatial resolution of the IRIS and EIS instruments, we are able to compare simultaneous observations of the Fe xxi 1354.08 Å and Fe xxiii 263.77 Å high-temperature emission (≳10 MK) in the flare ribbon during the chromospheric evaporation phase. We find that IRIS observes completely blueshifted Fe xxi line profiles, up to 200 km s-1 during the rise phase of the flare, indicating that the site of the plasma upflows is resolved by IRIS. In contrast, the Fe xxiii line is often asymmetric, which we interpret as being due to the lower spatial resolution of EIS. Temperature estimates from SDO/AIA and Hinode/XRT show that hot emission (log(T[K]) > 7.2) is first concentrated at the footpoints before filling the loops. Density-sensitive lines from IRIS and EIS give estimates of electron number density of ≳1012 cm-3 in the transition region lines and 1010 cm-3 in the coronal lines during the impulsive phase. In order to compare the observational results against theoretical predictions, we have run a simulation of a flare loop undergoing heating using the HYDRAD 1D hydro code. We find that the simulated plasma parameters are close to the observed values that are obtained with IRIS, Hinode, and AIA. These results support an electron beam heating model rather than a purely thermal conduction model as the driving mechanism for this flare. Title: On the validity of the ICFT R-matrix method: Fe XIV Authors: Del Zanna, G.; Badnell, N. R.; Fernández-Menchero, L.; Liang, G. Y.; Mason, H. E.; Storey, P. J. Bibcode: 2015MNRAS.454.2909D Altcode: Recently, Aggarwal & Keenan published a Dirac R-matrix (DARC) calculation for the electron-impact excitation of Fe XIV. A 136-level configuration-interaction/close-coupling (CI/CC) expansion was adopted. Comparisons with earlier calculations, obtained by Liang et al. with the intermediate coupling frame transformation (ICFT) R-matrix method, showed significant discrepancies. One of the main differences was that the Liang et al. effective collision strengths were consistently larger. Aggarwal & Keenan suggested various possible causes for the differences. We discuss them in detail here. We have carried out an ICFT R-matrix calculation with the same 136-level CI/CC expansion adopted by Aggarwal & Keenan, and compared the results with theirs and with those of Liang et al., which employed a much larger CI/CC expansion. We find that the main differences arise because of the different CC and CI expansions, and not because of the use of the ICFT method, as suggested by Aggarwal & Keenan. The significant increase in the effective collision strengths obtained by Liang et al. is mainly due to the extra resonances that are present because of the larger target expansion. Title: CHIANTI - An atomic database for emission lines. Version 8 Authors: Del Zanna, G.; Dere, K. P.; Young, P. R.; Landi, E.; Mason, H. E. Bibcode: 2015A&A...582A..56D Altcode: 2015arXiv150807631D We present version 8 of the CHIANTI database. This version includes a large amount of new data and ions, which represent a significant improvement in the soft X-ray, extreme UV (EUV) and UV spectral regions, which several space missions currently cover. New data for neutrals and low charge states are also added. The data are assessed, but to improve the modelling of low-temperature plasma the effective collision strengths for most of the new datasets are not spline-fitted as previously, but are retained as calculated. This required a change of the format of the CHIANTI electron excitation files. The format of the energy files has also been changed. Excitation rates between all the levels are retained for most of the new datasets, so the data can in principle be used to model high-density plasma. In addition, the method for computing the differential emission measure used in the CHIANTI software has been changed. Title: Slipping reconnection and chromospheric evaporation in the 10 September 2014 flare Authors: Dudík, Jaroslav; Janvier, Miho; Polito, Vanessa; Mulay, Sargam; Del Zanna, Giulio; Mason, Helen; Aulanier, Guillaume Bibcode: 2015IAUGA..2252237D Altcode: We study the occurrence of slipping reconnection in the long-duration X-class flare of 2014 September 10. From the start, the flare shows apparent slippage of hot Fe XXI flare loops observed in the 131A channel of SDO/AIA. Using the time-distance plots, we show that the slipping motion of the flare loops proceeds in counter directions in both flare ribbons. Simultaneous IRIS Fe XXI observations show the occurrence of chromospheric evaporation at brightening kernels that are involved in the slipping reconnection of AIA loops. This happens also during a flux-rope breakout accompanied by a faint 'magnetic implosion' of a coronal loop. Based on the 3D MHD flare model, we argue that the 'implosion' is caused by the erupting flux rope pushing the neighbouring loops aside, with the low-lying loops being squeezed. Title: Imaging and Spectroscopic Observations of a Transient Coronal Loop: Evidence for the Non-Maxwellian K Distributions Authors: Dudík, Jaroslav; Mackovjak, Šimon; Dzifčáková, Elena; Del Zanna, Giulio; Williams, David R.; Karlický, Marian; Mason, Helen E.; Lörinčík, Juraj; Kotrč, Pavel; Fárník, František; Zemanová, Alena Bibcode: 2015ApJ...807..123D Altcode: 2015arXiv150504333D We report on the Solar Dynamics Observatory/Atmospheric Imaging Assembly (AIA) and Hinode/EUV Imaging Spectrograph (EIS) observations of a transient coronal loop. The loop brightens up in the same location after the disappearance of an arcade formed during a B8.9-class microflare 3 hr earlier. EIS captures this loop during its brightening phase, as observed in most of the AIA filters. We use the AIA data to study the evolution of the loop, as well as to perform the differential emission measure (DEM) diagnostics as a function of κ. The Fe xi-Fe xiii lines observed by EIS are used to perform the diagnostics of electron density and subsequently the diagnostics of κ. Using ratios involving the Fe xi 257.772 Å self-blend, we diagnose κ ≲ 2, i.e., an extremely non-Maxwellian distribution. Using the predicted Fe line intensities derived from the DEMs as a function of κ, we show that, with decreasing κ, all combinations of ratios of line intensities converge to the observed values, confirming the diagnosed κ ≲ 2. These results represent the first positive diagnostics of κ-distributions in the solar corona despite the limitations imposed by calibration uncertainties. Title: Joint High Temperature Observation of a Small C6.5 Solar Flare With Iris/Eis/Aia Authors: Polito, V.; Reeves, K. K.; Del Zanna, G.; Golub, L.; Mason, H. E. Bibcode: 2015ApJ...803...84P Altcode: We present the observation of a C6.5 class flare on 2014 February 3, obtained with the Interface Region Imaging Spectrograph (IRIS) and the EUV Imaging Spectrometer (EIS) on board HINODE. We follow the details of the impulsive phase with IRIS and the gradual decay phase with both IRIS and EIS. The IRIS Slit-Jaw Imager and Atmospheric Imaging Assembly (AIA) are used to precisely co-align the two sets of spectroscopic observations. Of particular interest is the Fe xxi 1354.08 Å spectral line, which is the highest temperature emission (∼10 MK) observed in the IRIS wavelength range. We show the evolution of the Fe xxi profiles during the impulsive phase of the flare at the same ribbon location with a 75 s temporal cadence. Totally blueshifted (∼82 km {{s}-1}) profiles are found at the very early phase of the flare and gradually decrease in about 6 minutes. This result is consistent with 1D model predictions during chromospheric evaporation in flares. The blueshifted components also exhibit large non-thermal broadening, which decreases simultaneously with the blueshifted velocity. After the evaporation first occurs, the Fe xxi intensity progressively moves from the footpoints to the top of the hot flare loops seen in the AIA 131 Å images, where the emission is observed to be at rest and thermal. Emission measure estimates from IRIS/EIS/AIA observations during the gradual phase show isothermal loop top structures cooling from about 13.5 to 12 MK with electron densities of the order of ∼ 5-6× {{10}10} c{{m}-3}. Title: Spectroscopic Observations of a Coronal Loop: Basic Physical Plasma Parameters Along the Full Loop Length Authors: Gupta, G. R.; Tripathi, Durgesh; Mason, Helen E. Bibcode: 2015ApJ...800..140G Altcode: 2014arXiv1412.7428G Coronal loops are the basic structures of the solar transition region and corona. Understanding of the physical mechanisms behind the loop heating, plasma flows, and filling are still considered a major challenge in solar physics. The mechanism(s) should be able to supply mass to the corona from the chromosphere and to heat the plasma over 1 MK within a small distance of a few hundred kilometers from the chromosphere to the corona. This problem makes coronal loops an interesting target for detailed study. In this study, we focus on spectroscopic observations of a coronal loop observed in its full length in various spectral lines as recorded by the Extreme-ultraviolet Imaging Spectrometer on board Hinode. We derive physical plasma parameters such as electron density, temperature, pressure, column depth, and filling factors along the loop length from one footpoint to the another. The obtained parameters are used to infer whether the observed coronal loop is overdense or underdense with respect to gravitational stratification of the solar atmosphere. These new measurements of physical plasma parameters, from one footpoint to another, provide important constraints on the modeling of the mass and energy balance in coronal loops. Title: The evolution of the emission measure distribution in the core of an active region Authors: Del Zanna, Giulio; Tripathi, Durgesh; Mason, Helen; Subramanian, Srividya; O'Dwyer, Brendan Bibcode: 2015A&A...573A.104D Altcode: 2014arXiv1411.0128D We study the spatial distribution and evolution of the slope of the emission measure (EM) between 1 MK and 3 MK in the core of the active region (AR) NOAA 11193, first when it appeared near the central meridian and then again when it reappeared after a solar rotation. We use observations recorded by the Extreme-ultraviolet Imaging Spectrometer (EIS) aboard Hinode, with a new radiometric calibration. We also use observations from the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO). We present the first spatially resolved maps of the EM slope in the 1-3 MK range within the core of the AR using several methods, either from approximations or from the differential emission measure (DEM). A significant variation of the slope is found at different spatial locations within the active region. We selected two regions that were not greatly affected by lower temperature emission along the line of sight. We found that the EM had a power law of the form EM ∝ Tb, with b = 4.4 ± 0.4, and 4.6 ± 0.4, during the first and second appearance of the active region, respectively. During the second rotation, line-of-sight effects become more important, although difficult to estimate. We found that the use of the ground calibration for Hinode/EIS and the approximate method to derive the EM, used in previous publications, produce an underestimation of the slopes. The EM distribution in active region cores is generally found to be consistent with high frequency heating, and does not change much during the evolution of the active region. Title: Emission Measure Distribution for Diffuse Regions in Solar Active Regions Authors: Subramanian, Srividya; Tripathi, Durgesh; Klimchuk, James A.; Mason, Helen E. Bibcode: 2014ApJ...795...76S Altcode: 2014arXiv1409.1447S Our knowledge of the diffuse emission that encompasses active regions is very limited. In this paper we investigate two off-limb active regions, namely, AR 10939 and AR 10961, to probe the underlying heating mechanisms. For this purpose, we have used spectral observations from Hinode/EIS and employed the emission measure (EM) technique to obtain the thermal structure of these diffuse regions. Our results show that the characteristic EM distributions of the diffuse emission regions peak at log T = 6.25 and the coolward slopes are in the range 1.4-3.3. This suggests that both low- as well as high-frequency nanoflare heating events are at work. Our results provide additional constraints on the properties of these diffuse emission regions and their contribution to the background/foreground when active region cores are observed on-disk. Title: Signatures of the non-Maxwellian κ-distributions in optically thin line spectra. I. Theory and synthetic Fe IX-XIII spectra Authors: Dudík, J.; Del Zanna, G.; Mason, H. E.; Dzifčáková, E. Bibcode: 2014A&A...570A.124D Altcode: 2014arXiv1408.0950D
Aims: We investigate the possibility of diagnosing the degree of departure from the Maxwellian distribution using single-ion spectra originating in astrophysical plasmas in collisional ionization equilibrium.
Methods: New atomic data for excitation of Fe ix - Fe xiii are integrated under the assumption of a κ-distribution of electron energies. Diagnostic methods using lines of a single ion formed at any wavelength are explored. Such methods minimize uncertainties from the ionization and recombination rates, as well as the possible presence of non-equilibrium ionization. Approximations to the collision strengths are also investigated.
Results: The calculated intensities of most of the Fe ix - Fe xiii EUV lines show consistent behaviour with κ at constant temperature. Intensities of these lines decrease with κ, with the vast majority of ratios of strong lines showing little or no sensitivity to κ. Several of the line ratios, especially involving temperature-sensitive lines, show a sensitivity to κ that is of the order of several tens of per cent, or, in the case of Fe ix, up to a factor of two. Forbidden lines in the near-ultraviolet, visible, or infrared parts of the spectrum are an exception, with smaller intensity changes or even a reverse behaviour with κ. The most conspicuous example is the Fe x 6378.26 Å red line, whose intensity incerases with κ. This line is a potentially strong indicator of departures from the Maxwellian distribution. We find that it is possible to perform density diagnostics independently of κ, with many Fe xi, Fe xii, and Fe xiii line ratios showing strong density-sensitivity and negligible sensitivity to κ and temperature. We also tested different averaging of the collision strengths. It is found that averaging over 0.01 interval in log(E [ Ryd ]) is sufficient to produce accurate distribution-averaged collision strengths Υ(T,κ) at temperatures of the ion formation in ionization equilibrium.

Appendices are available in electronic form at http://www.aanda.org Title: Atomic data for astrophysics: Ni XV Authors: Del Zanna, G.; Storey, P. J.; Mason, H. E. Bibcode: 2014A&A...567A..18D Altcode: We present the first R-matrix scattering calculation for electron collisional excitation of Ni xv. The large-scale target includes configurations up to n = 4. The calculations were carried out using the intermediate-coupling frame transformation method. Significant enhancements in the collision strengths, compared to previous distorted-wave (DW) calculations, are found for several cases, in particular the forbidden lines within the ground configuration and the 3s2 3p 4s levels. We provide a complete set of rates and a list of strongest lines that are observable in astrophysical plasmas. Previous identifications are reviewed, and a few new ones suggested. The new data can be used to accurately measure electron densities for high-temperature (3 MK) plasmas, and the nickel abundance.

The full dataset (energies, transition probabilities and rates) is available from our APAP website http://www.apap-network.org, and also at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/567/A18 Title: VizieR Online Data Catalog: Ni XV electron collisional excitation (Del Zanna+, 2014) Authors: Del Zanna, G.; Storey, P. J.; Mason, H. E. Bibcode: 2014yCat..35670018D Altcode: 2014yCat..35679018D We present the first R-matrix scattering calculation for electron collisional excitation of NiXV. The large-scale target includes configurations up to n=4. The calculations were carried out using the intermediate-coupling frame transformation method (ICFT). Significant enhancements in the collision strengths, compared to previous distorted wave (DW) calculations, are found for several cases, in particular the forbidden lines within the ground configuration and the 3s2 3p 4s levels. We provide a complete set of rates and a list of strongest lines that are observable in astrophysical plasmas. Previous identifications are reviewed, and a few new ones suggested. The new data can be used to accurately measure electron densities for high-temperature (3MK) plasmas, and the nickel abundance.

(2 data files). Title: Atomic data for astrophysics: Fe IX Authors: Del Zanna, G.; Storey, P. J.; Badnell, N. R.; Mason, H. E. Bibcode: 2014A&A...565A..77D Altcode: We present the results of a new large-scale intermediate-coupling frame transformation R-matrix scattering calculation for electron collisional excitation of Fe ix. The target includes all the main configurations up to n = 5, to improve our earlier R-matrix and distorted-wave (DW) calculations for the n = 3,4 levels. Unlike similar calculations which we carried out for the other coronal iron ions, in this case the larger target does not significantly affect the collision strengths of the strongest transitions to the n = 3,4 levels. Some differences are however present for a few transitions, in particular for the 3d-4p line at 197.86 Å. For the weaker transitions, significant enhancements due to extra resonances resulting from this much bigger target are found. Several new line identifications are suggested. We find excellent agreement between predicted and observed line intensities in the EUV (Hinode EIS) showing that Fe ix lines provide a reliable temperature diagnostic. We also show that the visible forbidden lines are a good diagnostic to measure electron densities.

The full dataset (energies, transition probabilities and rates) are also available in electronic form at the APAP website (www.apap-network.org) and are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/565/A77 Title: Elemental abundances and temperatures of quiescent solar active region cores from X-ray observations Authors: Del Zanna, G.; Mason, H. E. Bibcode: 2014A&A...565A..14D Altcode: A brief review of studies of elemental abundances and emission measures in quiescent solar active region cores is presented. Hinode EUV Imaging Spectrometer (EIS) observations of strong iron spectral lines have shown sharply peaked distributions around 3 MK. EIS observations of lines emitted by a range of elements have allowed good estimates of abundances relative to iron. However, X-ray observations are required to measure the plasma emission above 3 MK and the abundances of oxygen and neon. We revisit, using up-to-date atomic data, older X-ray observations obtained by a sounding rocket and by the Solar Maximum Mission (SMM) Flat Crystal Spectrometer (FCS). We find that the Fe/O and Fe/Ne ratios are normally increased by a factor of 3.2, compared to the photospheric values. Similar results are obtained from FCS observations of six quiescent active region cores. The FCS observations also indicate that the emission measure above 3 MK has a very steep negative slope, with very little plasma observed at 5 MK or above.

Appendix A is available in electronic form at http://www.aanda.org Title: Slipping Magnetic Reconnection during an X-class Solar Flare Observed by SDO/AIA Authors: Dudík, J.; Janvier, M.; Aulanier, G.; Del Zanna, G.; Karlický, M.; Mason, H. E.; Schmieder, B. Bibcode: 2014ApJ...784..144D Altcode: 2014arXiv1401.7529D We present SDO/AIA observations of an eruptive X-class flare of 2012 July 12, and compare its evolution with the predictions of a three-dimensional (3D) numerical simulation. We focus on the dynamics of flare loops that are seen to undergo slipping reconnection during the flare. In the Atmospheric Imaging Assembly (AIA) 131 Å observations, lower parts of 10 MK flare loops exhibit an apparent motion with velocities of several tens of km s-1 along the developing flare ribbons. In the early stages of the flare, flare ribbons consist of compact, localized bright transition-region emission from the footpoints of the flare loops. A differential emission measure analysis shows that the flare loops have temperatures up to the formation of Fe XXIV. A series of very long, S-shaped loops erupt, leading to a coronal mass ejection observed by STEREO. The observed dynamics are compared with the evolution of magnetic structures in the "standard solar flare model in 3D." This model matches the observations well, reproducing the apparently slipping flare loops, S-shaped erupting loops, and the evolution of flare ribbons. All of these processes are explained via 3D reconnection mechanisms resulting from the expansion of a torus-unstable flux rope. The AIA observations and the numerical model are complemented by radio observations showing a noise storm in the metric range. Dm-drifting pulsation structures occurring during the eruption indicate plasmoid ejection and enhancement of the reconnection rate. The bursty nature of radio emission shows that the slipping reconnection is still intermittent, although it is observed to persist for more than an hour. Title: VizieR Online Data Catalog: Atomic data for FeIX (Del Zanna+, 2014) Authors: Del Zanna, G.; Storey, P. J.; Badnell, N. R.; Mason, H. E. Bibcode: 2014yCat..35650077D Altcode: 2014yCat..35659077D We present the results of a new large-scale intermediate-coupling frame transformation R-matrix scattering calculation for electron collisional excitation of Fe IX. The target includes all the main configurations up to n=5, to improve our earlier R-matrix and distorted-wave (DW) calculations for the n=3,4 levels. Unlike similar calculations which we carried out for the other coronal iron ions, in this case the larger target does not significantly affect the collision strengths of the strongest transitions to the n=3,4 levels. Some differences are however present for a few transitions, in particular for the 3d-4p line at 197.86Å. For the weaker transitions, significant enhancements due to extra resonances resulting from this much bigger target are found. Several new line identifications are suggested. We find excellent agreement between predicted and observed line intensities in the EUV (Hinode EIS) showing that Fe IX lines provide a reliable temperature diagnostic. We also show that the visible forbidden lines are a good diagnostic to measure electron densities.

(2 data files). Title: Diagnostics for the O IV and Si IV lines observed by IRIS Authors: Dudik, Jaroslav; Mason, Helen; Del Zanna, Giulio; Golub, Leon; Dzifcakova, Elena Bibcode: 2014cosp...40E.754D Altcode: We investigate the formation of the IRIS O IV and Si IV lines under non-Maxwellian conditions characterized by kappa-distributions. It is found that the Si IV lines are always formed at lower temperatures than the O IV lines. However, as the departure from the Maxwellian increases, the peak formation temperatures are shifted progressively to lower and lower temperatures. Coupled with the slope of the differential emission measure (DEM), it is possible for the Si IV lines to be formed very close to the solar chromosphere, with the majority of the O IV intensities coming from a different, higher part of the transition region. The predicted spectra for kappa-distributions exhibit very low O IV intensities compared to Si IV, analogously to what is observed by the IRIS spacecraft. Potential density diagnostics are discussed, as well as the contribution of photoexcitation to the formation of these lines. Title: Chromospheric evaporation in recurrent flares Authors: Polito, V.; Mason, Helen; Del Zanna, Giulio; Dudik, Jaroslav Bibcode: 2014cosp...40E2581P Altcode: We present high-cadence (3 minutes) Hinode/EIS observations of small recurrent flares and provide densities and velocities of the upflowing plasma in the locations of the chromospheric evaporation. Lines formed in the 2-10 MK range have significant blueshifts, of the order of 50 km/s or more. This upflowing plasma is the source of the 10 MK plasma that emits strongly in EUV and X-ray lines after the impulsive phases. We use the high-cadence and high-resolution SDO/AIA images to describe the locations of the upflows, and magnetograms to locate the ribbons. One interesting feature is that the recurrent flares are confined, until the last one when a large-scale eruption occurs. Title: Response of Hinode XRT to quiet Sun, active region and flare plasma Authors: O'Dwyer, B.; Del Zanna, G.; Mason, H. E. Bibcode: 2014A&A...561A..20O Altcode:
Aims: We examine the response of the Hinode X-Ray Telescope (XRT), using simultaneous observations with the Hinode Extreme-ultraviolet Imaging Spectrometer (EIS), for a flare, an active region and a quiet Sun region. We also examine the relative intensity calibration of EIS and XRT.
Methods: EIS differential emission measure distribution (DEM) curves were used to create synthetic spectra with the CHIANTI atomic database. The contribution of spectral lines and continuum emission to each of the XRT channels was determined from the synthetic spectra, which were then convolved with the effective area of each XRT channel. The predicted total count rates for each channel were compared with the observed count rates. The effects of varying elemental abundances and the temperature range for the inversion were investigated. DEMs obtained from the XRT bands were also computed and compared to those obtained with EIS.
Results: For the active region observations, the observed XRT count rates for most of the channels are in reasonable agreement with those predicted using EIS observations, but are dependent on the elemental abundances chosen. Significant discrepancies between predicted and observed count rates were found and are discussed for the adjacent quiet Sun region and also for the flare. Synthetic spectra and continuum emission contributing to the XRT channels are presented and discussed for the active region, quiet Sun and flare observations. Title: Solar Transition Region Lines Observed by the Interface Region Imaging Spectrograph: Diagnostics for the O IV and Si IV Lines Authors: Dudík, J.; Del Zanna, G.; Dzifčáková, E.; Mason, H. E.; Golub, L. Bibcode: 2014ApJ...780L..12D Altcode: 2013arXiv1311.6978D The formation of the transition region O IV and Si IV lines observable by the Interface Region Imaging Spectrograph (IRIS) is investigated for both Maxwellian and non-Maxwellian conditions characterized by a κ-distribution exhibiting a high-energy tail. The Si IV lines are formed at lower temperatures than the O IV lines for all κ. In non-Maxwellian situations with lower κ, the contribution functions are shifted to lower temperatures. Combined with the slope of the differential emission measure, it is possible for the Si IV lines to be formed at very different regions of the solar transition region than the O IV lines; possibly close to the solar chromosphere. Such situations might be discernible by IRIS. It is found that photoexcitation can be important for the Si IV lines, but is negligible for the O IV lines. The usefulness of the O IV ratios for density diagnostics independently of κ is investigated and it is found that the O IV 1404.78 Å/1399.77 Å ratio provides a good density diagnostics except for very low T combined with extreme non-Maxwellian situations. Title: A Collaborative FP7 Effort towards the First European Comprehensive SOLar Irradiance Data Exploitation (SOLID) Authors: Haberreiter, Margit; Dasi, Maria; Delouille, Veronique; Del Zanna, Giulio; Dudok de Wit, Thierry; Ermolli, Ilaria; Kretzschmar, Matthieu; Krivova, Natalie; Mason, Helen; Qahwaji, Rami; Schmutz, Werner; Solanki, Sami; Thuillier, Gerard; Tourpali, Kleareti; Unruh, Yvonne; Verbeeck, Cis; Weber, Mark; Woods, Tom Bibcode: 2013EGUGA..1513079H Altcode: Variations of solar irradiance are the most important natural factor in the terrestrial climate and as such, the time dependent spectral solar irradiance is a crucial input to any climate modelling. There have been previous efforts to compile solar irradiance but it is still uncertain by how much the spectral and total solar irradiance changed on yearly, decadal and longer time scales. Observations of irradiance data exist in numerous disperse data sets. Therefore, it is important to bring together the European expertise in the field to analyse and merge the complete set of European irradiance data, complemented by archive data that include data from non-European missions. We report on the initiation of a collaborative effort to unify representatives from all European solar space experiments and European teams specialized in multi-wavelength solar image processing. It is intended to include the European groups involved in irradiance modelling and reconstruction. They will work with two different state of the art approaches to produce reconstructed spectral and total solar irradiance data as a function of time. These results will be used to bridge gaps in time and wavelength coverage of the observational data. This will allow the proposing SOLID team to reduce the uncertainties in the irradiance time series - an important requirement by the climate community - and to provide uniform data sets of modelled and observed solar irradiance data from the beginning of the space era to the present including proper error and uncertainty estimates. Climate research needs these data sets and therefore, the primary benefit is for the climate community, but the stellar community, planetary, lunar, and ionospheric researchers are also interested in having at their disposition incident radiation of the Sun. The proposing team plans to realize a wide international synergy in solar physics from 7 European countries, and collaborators from the US, complemented by representatives from the climate community, who will accompany their research work with wide dissemination activities. Title: Doppler Shifts in Active Region Moss Using SOHO/SUMER Authors: Winebarger, Amy; Tripathi, Durgesh; Mason, Helen E.; Del Zanna, Giulio Bibcode: 2013ApJ...767..107W Altcode: The velocity of the plasma at the footpoint of hot loops in active region cores can be used to discriminate between different heating frequencies. Velocities on the order of a few kilometers per second would indicate low-frequency heating on sub-resolution strands, while velocities close to zero would indicate high-frequency (steady) heating. To discriminate between these two values requires accurate velocity measurements; previous velocity measurements suffer from large uncertainties, mainly due to the lack of an absolute wavelength reference scale. In this paper, we determine the velocity in the loop footpoints using observations from Solar Ultraviolet Measurements of Emitted Radiation (SUMER) on Solar and Heliospheric Observatory. We use neutral spectral lines to determine the wavelength scale of the observations with an uncertainty in the absolute velocity of <3.5 km s-1 and co-aligned Transition Region and Coronal Explorer (TRACE) images to identify footpoint regions. We studied three different active regions and found average redshifts in the Ne VIII 770 Å emission line (formed at 6 × 105 K) of 5.17 ± 5.37 km s-1 and average redshifts in the C IV 1548 and 1550 Å emission lines (formed at 1 × 105 K) of 13.94 ± 4.93 km s-1 and 14.91 ± 6.09 km s-1, respectively. We find no correlation between the brightness in the spectral line and the measured velocity, nor do we find correlation between the Ne VIII and C IV velocities measured co-spatially and co-temporally. SUMER scanned two of the active regions twice; in those active regions we find positive correlation between the co-spatial velocities measured during the first and second scans. These results provide definitive and quantitative measurements for comparisons with simulations of different coronal heating mechanisms. Title: CHIANTI 7.1: a new database release for SDO data analysis Authors: Young, P. R.; Landi, E.; Del Zanna, G.; Dere, K. P.; Mason, H. E. Bibcode: 2013enss.confE..58Y Altcode: Version 7.1 of the CHIANTI atomic database was released in October 2012 and contains a number of improvements to better model data returned by the AIA and EVE instruments on board SDO. Specifically the models for the important iron ions Fe VIII to Fe XIV have been greatly expanded, yielding many thousands of new transitions in the 50-170 angstrom range that enable the irradiance spectra obtained by EVE to be modeled more accurately. A lack of available atomic data meant that the AIA 94 angstrom channel was not well modeled at low temperatures in earlier versions of CHIANTI. New data for Fe VIII, Fe X and Fe XIV added to CHIANTI 7.1 give important contributions to the channel and greatly improve comparisons with theory. Title: CHIANTI—An Atomic Database for Emission Lines. XIII. Soft X-Ray Improvements and Other Changes Authors: Landi, E.; Young, P. R.; Dere, K. P.; Del Zanna, G.; Mason, H. E. Bibcode: 2013ApJ...763...86L Altcode: The CHIANTI spectral code consists of two parts: an atomic database and a suite of computer programs in Python and IDL. Together, they allow the calculation of the optically thin spectrum of astrophysical objects and provide spectroscopic plasma diagnostics for the analysis of astrophysical spectra. The database includes atomic energy levels, wavelengths, radiative transition probabilities, collision excitation rate coefficients, ionization, and recombination rate coefficients, as well as data to calculate free-free, free-bound, and two-photon continuum emission. Version 7.1 has been released, which includes improved data for several ions, recombination rates, and element abundances. In particular, it provides a large expansion of the CHIANTI models for key Fe ions from Fe VIII to Fe XIV to improve the predicted emission in the 50-170 Å wavelength range. All data and programs are freely available at http://www.chiantidatabase.org and in SolarSoft, while the Python interface to CHIANTI can be found at http://chiantipy.sourceforge.net. Title: The Sun as a Star Authors: Del Zanna, Giulio; Mason, Helen Bibcode: 2013pss4.book...87D Altcode: In this chapter we provide an overview of various observational and theoreticalaspects about the Sun, paying more attention to global ones, i.e., to thosewhere the Sun is considered as a star, so they can be more or less directlyrelated to those studied for other stars. The emphasis is on the processes bywhich energy is transferred to the solar atmosphere and then flows fromthe Sun in the form of radiation and particles. The chapter starts withan historical introduction, and then discusses various subjects, startingwith a brief description of the photosphere, the chromosphere, and thetransition region of the Sun. The interior of the Sun is then introduced,with the standard model and solar neutrinos, and with the observationsand theory of solar oscillations. We present some important results fromhelioseismology, and briefly discuss the problematics involved with theproduction and regeneration of the solar magnetic fields during a solarcycle. Title: The spectroscopy of the dynamic Sun Authors: Mason, Helen; Baker, Deb Bibcode: 2012A&G....53f..29M Altcode: MEETING REPORT Helen Mason and Deb Baker celebrate the collaboration between George Doschek and Tetsuya Watanabe that has uncovered so much about the Sun's behaviour. Title: SDO AIA and EVE observations and modelling of solar flare loops Authors: Petkaki, P.; Del Zanna, G.; Mason, H. E.; Bradshaw, S. J. Bibcode: 2012A&A...547A..25P Altcode: We present imaging and spectroscopic observations of an isolated C1-class solar flare, obtained with the Atmospheric Imaging Assembly (AIA) and Extreme ultraviolet Variability Experiment (EVE) on the Solar Dynamics Observatory (SDO). We obtain excellent agreement between the peak flare temperatures estimated using the EVE spectra with those obtained from GOES and, most importantly, from the ratio of the 94 Å and 131 Å AIA channels, which are found to be dominated by Fe xviii and Fe xxi. These results confirm that these two AIA bands can be reliably used to provide temperature diagnostics for the peak and gradual phases of solar flares. The flare kernels, probable sources of chromospheric evaporation, are seen as strong localised emission in the AIA bands at the footpoints of flare loops. The flare loops are close to isothermal during the gradual phase. We have run several hydrodynamic simulations (using the HYDRAD code) to study the cooling of the flare loops. We find good overall agreement between observed and predicted electron temperatures and densities when a gradual increase and decrease of the heating is assumed. Title: Atomic data for astrophysics: Fe xii soft X-ray lines Authors: Del Zanna, G.; Storey, P. J.; Badnell, N. R.; Mason, H. E. Bibcode: 2012A&A...543A.139D Altcode: We present new large-scale R-matrix (up to n = 4) and distorted-wave (DW, up to n = 6) scattering calculations for electron collisional excitation of Fe xii. The first aim is to provide accurate atomic data for the soft X-rays, where strong decays from the n = 4 levels are present. As found in previous work on Fe x, resonances attached to n = 4 levels increase the cross-sections for excitations from the ground state to some n = 4 levels, when compared to DW calculations. Cascading from higher levels is also important. We provide a number of models and line intensities, and list a number of strong unidentified lines. The second aim is to assess the effects of the large R-matrix calculation on the n = 3 transitions. Compared to our previous (n = 3) R-matrix calculation, we find overall excellent agreement to within a few percent, however a few key density diagnostic EUV intensities differ by about 60% at coronal densities. The new atomic data result in lower electron densities, resolving previous discrepancies with solar observations.

The full dataset (energies, transition probabilities and rates) are available in electronic form at our APAP website (http://www.apap-network.org) as well as at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/543/A139 Title: Active Region Moss: Doppler Shifts from Hinode/Extreme-ultraviolet Imaging Spectrometer Observations Authors: Tripathi, Durgesh; Mason, Helen E.; Klimchuk, James A. Bibcode: 2012ApJ...753...37T Altcode: 2012arXiv1204.6550T Studying the Doppler shifts and the temperature dependence of Doppler shifts in moss regions can help us understand the heating processes in the core of the active regions. In this paper, we have used an active region observation recorded by the Extreme-ultraviolet Imaging Spectrometer (EIS) on board Hinode on 2007 December 12 to measure the Doppler shifts in the moss regions. We have distinguished the moss regions from the rest of the active region by defining a low-density cutoff as derived by Tripathi et al. in 2010. We have carried out a very careful analysis of the EIS wavelength calibration based on the method described by Young et al. in 2012. For spectral lines having maximum sensitivity between log T = 5.85 and log T = 6.25 K, we find that the velocity distribution peaks at around 0 km s-1 with an estimated error of 4-5 km s-1. The width of the distribution decreases with temperature. The mean of the distribution shows a blueshift which increases with increasing temperature and the distribution also shows asymmetries toward blueshift. Comparing these results with observables predicted from different coronal heating models, we find that these results are consistent with both steady and impulsive heating scenarios. However, the fact that there are a significant number of pixels showing velocity amplitudes that exceed the uncertainty of 5 km s-1 is suggestive of impulsive heating. Clearly, further observational constraints are needed to distinguish between these two heating scenarios. Title: VizieR Online Data Catalog: Fe XII soft X-ray lines (Del Zanna+, 2012) Authors: Del Zanna, G.; Storey, P. J.; Badnell, N. R.; Mason, H. E. Bibcode: 2012yCat..35430139D Altcode: 2012yCat..35439139D We present new large-scale R-matrix (up to n=4) and distorted-wave (DW, up to n=6) scattering calculations for electron collisional excitation of Fe XII. The first aim is to provide accurate atomic data for the soft X-rays, where strong decays from the n=4 levels are present. As found in previous work on Fe X, resonances attached to n=4 levels increase the cross-sections for excitations from the ground state to some n=4 levels, when compared to DW calculations. Cascading from higher levels is also important.

We provide a number of models and line intensities, and list a number of strong unidentified lines.

The second aim is to assess the effects of the large R-matrix calculation on the n=3 transitions. Compared to our previous (n=3) R-matrix calculation, we find overall excellent agreement to within a few percent, however a few key density diagnostic EUV intensities differ by about 60% at coronal densities. The new atomic data result in lower electron densities, resolving previous discrepancies with solar observations.

(5 data files). Title: Observations of Plasma Upflow in a Warm Loop with Hinode/EIS Authors: Tripathi, Durgesh; Mason, Helen E.; Del Zanna, Giulio; Bradshaw, Steven Bibcode: 2012ApJ...754L...4T Altcode: 2012arXiv1206.3367T A complete understanding of Doppler shift in active region loops can help probe the basic physical mechanism involved into the heating of those loops. Here, we present observations of upflows in coronal loops detected in a range of temperatures (log T = 5.8-6.2). The loop was not discernible above these temperatures. The speed of upflow was strongest at the footpoint and decreased with height. The upflow speed at the footpoint was about 20 km s-1 in Fe VIII, which decreased with temperature, being about 13 km s-1 in Fe X, about 8 km s-1 in Fe XII, and about 4 km s-1 in Fe XIII. To the best of our knowledge, this is the first observation providing evidence of upflow of plasma in coronal loop structures at these temperatures. We interpret these observations as evidence of chromospheric evaporation in quasi-static coronal loops. Title: VizieR Online Data Catalog: FeX soft X-ray lines (Del Zanna+, 2012) Authors: Del Zanna, G.; Storey, P. J.; Badnell, N. R.; Mason, H. E. Bibcode: 2012yCat..35410090D Altcode: 2012yCat..35419090D New atomic calculations for Fe X are presented. They focus on the need to model the soft X-ray spectrum and in particular the line at 94.0Å which is the dominant contribution to the Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) 94Å band in quiet Sun conditions. This line, and others in the band, are due to strong decays from n=4 levels. We present new large-scale R-matrix (up to n=4) and distorted-wave (DW, up to n=6) scattering calculations for electron collisional excitation and compare them to earlier work. We find significant discrepancies with previous calculations. We show that resonances significantly increase the cross-sections for excitations from the ground state to some n=4 levels, in particular to those in the 3s2 3p4 4s configuration. Cascading from higher levels is also important. We suggest a new identification for the 3s 3p6 2S1/2 - 3s 3p5 4s 2P3/2 transition, that has a predicted intensity larger than the decays from the 3s2 3p4 4s levels which were identified by Edlen in 1936. The results presented here are relevant to our understanding of transitions from n=4 levels in a wide range of other ions.

(5 data files). Title: Cross-Calibration of Hinode/EIS and SDO/AIA Authors: O'Dwyer, B.; Zanna, G. D.; Mason, H. E.; Weber, M. A.; Tripathi, D. Bibcode: 2012ASPC..455..369O Altcode: We examine the contribution of spectral lines and continuum emission to the EUV channels of the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO) in different regions of the solar atmosphere (coronal hole, quiet Sun, active region, and flare plasma). We highlight the contribution of particular spectral lines which under certain conditions can affect the interpretation of SDO AIA data. In addition we use simultaneous observations from the Hinode Extreme-ultraviolet Imaging Spectrometer (EIS) and SDO/AIA to examine their relative intensity calibration. Good agreement is found between the two instruments for an active region observation. Title: Hinode Observations and Modeling of Small Flares Authors: Zanna, G. D.; Mitra-Kraev, U.; Bradshaw, S. J.; Mason, H. E.; Asai, A. Bibcode: 2012ASPC..455..295Z Altcode: We present Hinode observations of a small B-class flare which occurred on May 22, 2007, supplemented with X-ray, EUV, and radio data. We found new signatures of chromospheric evaporation, strong (up to 170 km s-1) blue-shifted emission in lines formed around 2-3 MK, in a very narrow layer at the footpoints of a 10 MK flare loop. We have found good agreement between the observed properties and those predicted by a HYDRAD non-equilibrium hydrodynamic numerical simulation. Title: Atomic data for astrophysics: Fe x soft X-ray lines Authors: Del Zanna, G.; Storey, P. J.; Badnell, N. R.; Mason, H. E. Bibcode: 2012A&A...541A..90D Altcode: New atomic calculations for Fe x are presented. They focus on the need to model the soft X-ray spectrum and in particular the line at 94.0 Å which is the dominant contribution to the Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) 94 Å band in quiet Sun conditions. This line, and others in the band, are due to strong decays from n = 4 levels. We present new large-scale R-matrix (up to n = 4) and distorted-wave (DW, up to n = 6) scattering calculations for electron collisional excitation and compare them to earlier work. We find significant discrepancies with previous calculations. We show that resonances significantly increase the cross-sections for excitations from the ground state to some n = 4 levels, in particular to those in the 3s2 3p4 4s configuration. Cascading from higher levels is also important. We suggest a new identification for the 3s 3p62S1/2-3s 3p5 4s 2P3/2 transition, that has a predicted intensity larger than the decays from the 3s2 3p4 4s levels which were identified by Edlén in 1936. The results presented here are relevant to our understanding of transitions from n = 4 levels in a wide range of other ions.

The full dataset (energies, transition probabilities and rates) are available in electronic form at our APAP website (www.apap-network.org) as well as at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/541/A90 Title: Understanding Coronal Heating with Emission Measure Distributions Authors: Klimchuk, James A.; Tripathi, D.; Bradshaw, S. J.; Mason, H. E. Bibcode: 2012AAS...22042302K Altcode: It is widely believed that the cross-field spatial scale of coronal heating is small, so that the fundamental plasma structures (loop strands) are spatially unresolved. We therefore must appeal to diagnostic techniques that are not strongly affected by spatial averaging. One valuable observable is the emission measure distribution, EM(T), which indicates how much material is present at each temperature. Using data from the Extreme-ultraviolet Imaging Spectrograph on the Hinode mission, we have determined emission measure distributions in the cores of two active regions. The distributions have power law slopes of approximately 2.4 coolward of the peak. We compare these slopes, as well as the amount of emission measure at very high temperature, with the predictions of a series of models. The models assume impulsive heating (nanoflares) in unresolved strands and take full account of nonequilibrium ionization. Title: VizieR Online Data Catalog: Atomic data for X-ray lines of FeVIII and FeIX (O'Dwyer+, 2012) Authors: O'Dwyer, B.; Del Zanna, G.; Badnell, N. R.; Mason, H. E.; Storey, P. J. Bibcode: 2012yCat..35370022O Altcode: 2012yCat..35379022O The distorted wave extension of the autostructure code has been used to calculate energy levels, radiative transition probabilities and collisional excitation rates of Fe VIII and Fe IX up to n=6 for Fe IX and n=7 for Fe VIII. We have compared some of the data with previous calculations, finding overall agreement for radiative transition rates, but interesting differences for some collisional data.

************************************************************************** * * * Sorry, but the author(s) never supplied the tabular material * * announced in the paper * * * ************************************************************************** Title: Spectroscopic Diagnostics and Heating of Active Region Cores Authors: Tripathi, D.; Mason, H. E.; Klimchuk, J. A. Bibcode: 2012decs.confE..92T Altcode: It is widely believed that we are still far from spatially resolving the fundamental plasma structures in solar corona. Therefore, we must use spectroscopic diagnostic techniques such as emission measure distribution (EM(T)) and Doppler shifts that are not affected by spatial averaging. Using observations recorded by the Extreme ultraviolet Imaging Spectrometer we have studies emission measure (EM) distribution and Doppler shift in the moss and inter-moss regions. The EM distributions obtained for moss regions cab be reproduced by considering strong coronal condensation scenario suggesting bulk downflow of the plasma. Doppler shift measurements for the moss regions show that almost all the moss regions are red-shifted with velocities up to 15km/s with mean velocity of 5 km/s. However, the uncertainty on the Doppler shift was large. The EM distributions obtained for inter-moss regions have power law slopes of approximately 2.4 coolward of the peak. We compare the EM for inter-moss region with that obtained from nanoflare model using EBTEL (Enthalpy-Based Thermal Evolution of Loops). Our results suggest that the EM distribution for both the moss as well as inter-moss regions and Doppler shift in the moss regions can be explained by nanoflare heating. IRIS will provide a better account of the Doppler shift in the moss regions, which will dramatically enhance our understanding of the heating of active region core. Title: Spectroscopic Diagnostics with IRIS Authors: Mason, H. E.; Del Zanna, G. Bibcode: 2012decs.confE..47M Altcode: This talk will review the spectroscopic diagnostics available in the IRIS wavelength bands, built on the previous heritage of observations in the 1330-1410A wavelength band. Consideration will be given to the accuracy of available atomic data in CHIANTI and the relevant atomic processes. Ways in which the IRIS data could be used to complement observations from other observatories (SDO and Hinode) will be explored with a view to probing the energy transport and dissipation in the solar atmosphere. Title: CHIANTI—An Atomic Database for Emission Lines. XII. Version 7 of the Database Authors: Landi, E.; Del Zanna, G.; Young, P. R.; Dere, K. P.; Mason, H. E. Bibcode: 2012ApJ...744...99L Altcode: The CHIANTI spectral code consists of an atomic database and a suite of computer programs to calculate the optically thin spectrum of astrophysical objects and carry out spectroscopic plasma diagnostics. The database includes atomic energy levels, wavelengths, radiative transition probabilities, collision excitation rate coefficients, and ionization and recombination rate coefficients, as well as data to calculate free-free, free-bound, and two-photon continuum emission. Version 7 has been released, which includes several new ions, significant updates to existing ions, as well as Chianti-Py, the implementation of CHIANTI software in the Python programming language. All data and programs are freely available at http://www.chiantidatabase.org, while the Python interface to CHIANTI can be found at http://chiantipy.sourceforge.net. Title: Velocity Measurements for a Solar Active Region Fan Loop from Hinode/EIS Observations Authors: Young, P. R.; O'Dwyer, B.; Mason, H. E. Bibcode: 2012ApJ...744...14Y Altcode: 2011arXiv1107.2362Y The velocity pattern of a fan loop structure within a solar active region over the temperature range 0.15-1.5 MK is derived using data from the EUV Imaging Spectrometer (EIS) on board the Hinode satellite. The loop is aligned toward the observer's line of sight and shows downflows (redshifts) of around 15 km s-1 up to a temperature of 0.8 MK, but for temperatures of 1.0 MK and above the measured velocity shifts are consistent with no net flow. This velocity result applies over a projected spatial distance of 9 Mm and demonstrates that the cooler, redshifted plasma is physically disconnected from the hotter, stationary plasma. A scenario in which the fan loops consist of at least two groups of "strands"—one cooler and downflowing, the other hotter and stationary—is suggested. The cooler strands may represent a later evolutionary stage of the hotter strands. A density diagnostic of Mg VII was used to show that the electron density at around 0.8 MK falls from 3.2 × 109 cm-3 at the loop base, to 5.0 × 108 cm-3 at a projected height of 15 Mm. A filling factor of 0.2 is found at temperatures close to the formation temperature of Mg VII (0.8 MK), confirming that the cooler, downflowing plasma occupies only a fraction of the apparent loop volume. The fan loop is rooted within a so-called outflow region that displays low intensity and blueshifts of up to 25 km s-1 in Fe XII λ195.12 (formed at 1.5 MK), in contrast to the loop's redshifts of 15 km s-1 at 0.8 MK. A new technique for obtaining an absolute wavelength calibration for the EIS instrument is presented and an instrumental effect, possibly related to a distorted point-spread function, that affects velocity measurements is identified. Title: Atomic data for the X-ray lines of Fe viii and Fe ix Authors: O'Dwyer, B.; Del Zanna, G.; Badnell, N. R.; Mason, H. E.; Storey, P. J. Bibcode: 2012A&A...537A..22O Altcode: The distorted wave extension of the autostructure code has been used to calculate energy levels, radiative transition probabilities and collisional excitation rates of Fe viii and Fe ix up to n = 6 for Fe ix and n = 7 for Fe viii. We have compared some of the data with previous calculations, finding overall agreement for radiative transition rates, but interesting differences for some collisional data. We have merged our data for the higher energy levels with published R-matrix collisional excitation rates for the lower ones to calculate spectral line intensities and compare them with observations. In particular, we have focused on the transitions from high energy levels of Fe viii & Fe ix which are present in the 93-95 Å region. A few new identifications are tentatively provided. We find that Fe ix 5f-3d and Fe viii 7f-3d transitions only comprise a small fraction of the observed lines in the 93-95 Å region for quiet Sun conditions, and thus their contribution to the Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) 94 Å band is expected to be small.

A complete list of calculated energies, radiative data and thermally averaged collision strengths is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/537/A22 Title: Understanding Coronal Heating with Emission Measure Distributions Authors: Klimchuk, J. A.; Tripathi, D.; Bradshaw, S. J.; Mason, H. E. Bibcode: 2011AGUFMSH43F..03K Altcode: It is widely believed that the cross-field spatial scale of coronal heating is small, so that the fundamental plasma structures (loop strands) are spatially unresolved. We therefore must appeal to diagnostic techniques that are not strongly affected by spatial averaging. One valuable observable is the emission measure distribution, EM(T), which indicates how much material is present at each temperature. Using data from the Extreme-ultraviolet Imaging Spectrograph on the Hinode mission, we have determined emission measure distributions in the cores of two active regions. The distributions have power law slopes of approximately 2.4 coolward of the peak. We compare these slopes, as well as the amount of emission measure at very high temperature, with the predictions of a series of models. The models assume impulsive heating (nanoflares) in unresolved strands and take full account of nonequilibrium ionization. A variety of nanoflare properties and initial conditions are considered. We also comment on the selection of spectral lines for upcoming missions like Solar Orbiter. Title: SDO AIA and Hinode EIS observations of "warm" loops Authors: Del Zanna, G.; O'Dwyer, B.; Mason, H. E. Bibcode: 2011A&A...535A..46D Altcode: We present simultaneous observations of active region "warm" (1 MK) loops using the Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) and Hinode EUV Imaging Spectrometer (EIS). Sample EIS spectra for a loop footpoint and a lop leg region are presented, and are used to describe the spectral lines which contribute to the six AIA EUV channels, both directly and predicted with DEM modeling. We find good overall agreement between observed and predicted count rates for the 131 Å, 193 Å, and 335 Å bands, but highlight a number of problems, partly to be ascribed to inter-calibration issues, partly due to the fact that a large number of lines remain unidentified for the 94 Å, 171 Å, and 211 Å bands. We also found that the 335 Å band is severely affected by cross-talk with the 131 Å band and by second order contributions. We extend our previous work where we highlighted the multi-thermal nature of the SDO AIA bands to show that emission from lines formed at typical transition region temperatures (log T[K] = 5.0-5.8) can be significant for all the EUV channels, and even dominant in some cases. We also assess the possibility of deriving accurate emission measures from the AIA observations. We have found that the inversion of the AIA data to obtain a description of the thermal characteristics of warm loops is unreliable. We highlight the need for further work on the relevant atomic data before the AIA data can be reliably used for plasma diagnostic purposes.

Appendices A-C are available in electronic form at http://www.aanda.org Title: Emission Measure Distribution and Heating of Two Active Region Cores Authors: Tripathi, Durgesh; Klimchuk, James A.; Mason, Helen E. Bibcode: 2011ApJ...740..111T Altcode: 2011arXiv1107.4480T Using data from the Extreme-ultraviolet Imaging Spectrometer aboard Hinode, we have studied the coronal plasma in the core of two active regions. Concentrating on the area between opposite polarity moss, we found emission measure distributions having an approximate power-law form EMvpropT 2.4 from log T = 5.5 up to a peak at log T = 6.55. We show that the observations compare very favorably with a simple model of nanoflare-heated loop strands. They also appear to be consistent with more sophisticated nanoflare models. However, in the absence of additional constraints, steady heating is also a viable explanation. Title: The 22 May 2007 B-class flare: new insights from Hinode observations Authors: Del Zanna, G.; Mitra-Kraev, U.; Bradshaw, S. J.; Mason, H. E.; Asai, A. Bibcode: 2011A&A...526A...1D Altcode: We present multi-wavelength observations of a small B-class flare which occurred on the Sun on 2007 May 22. The observations include data from Hinode, GOES, TRACE and the Nobeyama Radioheliograph. We obtained spatially and spectrally-resolved information from the Hinode EUV Imaging Spectrometer (EIS) during this event. The temporal and temperature coverage of the EIS observations provides new insights into our understanding of chromospheric evaporation and cooling. The flare showed many “typical” features, such as brightenings in the ribbons, hot (10 MK) loop emission and subsequent cooling. We also observed a new feature, strong (up to 170 km s-1) blue-shifted emission in lines formed around 2-3 MK, located at the footpoints of the 10 MK coronal emission and within the ribbons. Electron densities at 2 MK in the kernels are high, of the order of 1011 cm-3, suggesting a very narrow layer where the chromospheric evaporation occurs. We have run a non-equilibrium hydrodynamic numerical simulation using the HYDRAD code to study the cooling of the 10 MK plasma, finding good agreement between the predicted and observed temperatures, densities and ion populations. Line blending for some potentially useful diagnostic lines for flares, which are observed with Hinode/EIS, is also discussed. Title: Hinode extreme-ultraviolet imaging spectrometer observations of a limb active region Authors: O'Dwyer, B.; Del Zanna, G.; Mason, H. E.; Sterling, A. C.; Tripathi, D.; Young, P. R. Bibcode: 2011A&A...525A.137O Altcode:
Aims: We investigate the electron density and temperature structure of a limb active region.
Methods: We have carried out a study of an active region close to the solar limb using observations from the Extreme-ultraviolet Imaging Spectrometer (EIS) and the X-ray telescope (XRT) on board Hinode. The electron density and temperature distributions of the coronal emission have been determined using emission line intensity ratios. Differential emission measure (DEM) analysis and the emission measure (EM) loci technique were used to examine the thermal structure of the emitting plasma as a function of distance from the limb.
Results: The highest temperature and electron density values are found to be located in the core of the active region, with a peak electron number density value of 1.9 × 1010 cm-3 measured using the Fe XII 186.887 Å to 192.394 Å line intensity ratio. The plasma along the line of sight in the active region was found to be multi-thermal at different distances from the limb. The EIS and XRT DEM analyses appear to be in agreement in the temperature interval from log T = 6.5-6.7.
Conclusions: Our results provide new constraints for models of coronal heating in active regions. Title: Science Objectives for an X-Ray Microcalorimeter Observing the Sun Authors: Laming, J. Martin; Adams, J.; Alexander, D.; Aschwanden, M; Bailey, C.; Bandler, S.; Bookbinder, J.; Bradshaw, S.; Brickhouse, N.; Chervenak, J.; Christe, S.; Cirtain, J.; Cranmer, S.; Deiker, S.; DeLuca, E.; Del Zanna, G.; Dennis, B.; Doschek, G.; Eckart, M.; Fludra, A.; Finkbeiner, F.; Grigis, P.; Harrison, R.; Ji, L.; Kankelborg, C.; Kashyap, V.; Kelly, D.; Kelley, R.; Kilbourne, C.; Klimchuk, J.; Ko, Y. -K.; Landi, E.; Linton, M.; Longcope, D.; Lukin, V.; Mariska, J.; Martinez-Galarce, D.; Mason, H.; McKenzie, D.; Osten, R.; Peres, G.; Pevtsov, A.; Porter, K. Phillips F. S.; Rabin, D.; Rakowski, C.; Raymond, J.; Reale, F.; Reeves, K.; Sadleir, J.; Savin, D.; Schmelz, J.; Smith, R. K.; Smith, S.; Stern, R.; Sylwester, J.; Tripathi, D.; Ugarte-Urra, I.; Young, P.; Warren, H.; Wood, B. Bibcode: 2010arXiv1011.4052L Altcode: We present the science case for a broadband X-ray imager with high-resolution spectroscopy, including simulations of X-ray spectral diagnostics of both active regions and solar flares. This is part of a trilogy of white papers discussing science, instrument (Bandler et al. 2010), and missions (Bookbinder et al. 2010) to exploit major advances recently made in transition-edge sensor (TES) detector technology that enable resolution better than 2 eV in an array that can handle high count rates. Combined with a modest X-ray mirror, this instrument would combine arcsecondscale imaging with high-resolution spectra over a field of view sufficiently large for the study of active regions and flares, enabling a wide range of studies such as the detection of microheating in active regions, ion-resolved velocity flows, and the presence of non-thermal electrons in hot plasmas. It would also enable more direct comparisons between solar and stellar soft X-ray spectra, a waveband in which (unusually) we currently have much better stellar data than we do of the Sun. Title: Evidence of Impulsive Heating in Active Region Core Loops Authors: Tripathi, Durgesh; Mason, Helen E.; Klimchuk, James A. Bibcode: 2010ApJ...723..713T Altcode: 2010arXiv1009.0663T Using a full spectral scan of an active region from the Extreme-Ultraviolet Imaging Spectrometer (EIS) we have obtained emission measure EM(T) distributions in two different moss regions within the same active region. We have compared these with theoretical transition region EMs derived for three limiting cases, namely, static equilibrium, strong condensation, and strong evaporation from Klimchuk et al. The EM distributions in both the moss regions are strikingly similar and show a monotonically increasing trend from log T[K] = 5.15-6.3. Using photospheric abundances, we obtain a consistent EM distribution for all ions. Comparing the observed and theoretical EM distributions, we find that the observed EM distribution is best explained by the strong condensation case (EMcon), suggesting that a downward enthalpy flux plays an important and possibly dominant role in powering the transition region moss emission. The downflows could be due to unresolved coronal plasma that is cooling and draining after having been impulsively heated. This supports the idea that the hot loops (with temperatures of 3-5 MK) seen in the core of active regions are heated by nanoflares. Title: SDO/AIA response to coronal hole, quiet Sun, active region, and flare plasma Authors: O'Dwyer, B.; Del Zanna, G.; Mason, H. E.; Weber, M. A.; Tripathi, D. Bibcode: 2010A&A...521A..21O Altcode:
Aims: We examine the contribution of spectral lines and continuum emission to the EUV channels of the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO) in different regions of the solar atmosphere.
Methods: Synthetic spectra were obtained using the CHIANTI atomic database and sample differential emission measures for coronal hole, quiet Sun, active region and flare plasma. These synthetic spectra were convolved with the effective area of each channel, in order to determine the dominant contribution in different regions of the solar atmosphere.
Results: We highlight the contribution of particular spectral lines which under certain conditions can affect the interpretation of SDO/AIA data. Title: Evidence for magnetic flux cancelation leading to an ejective solar eruption observed by Hinode, TRACE, STEREO, and SoHO/MDI Authors: Sterling, A. C.; Chifor, C.; Mason, H. E.; Moore, R. L.; Young, P. R. Bibcode: 2010A&A...521A..49S Altcode:
Aims: We study the onset of a solar eruption involving a filament ejection on 2007 May 20.
Methods: We observe the filament in Hα images from Hinode/SOT and in EUV with TRACE and STEREO/SECCHI/EUVI. Hinode/XRT images are used to study the eruption in soft X-rays. From spectroscopic data taken with Hinode/EIS we obtain bulk-flow velocities, line profiles, and plasma densities in the onset region. The magnetic field evolution was observed in SoHO/MDI magnetograms.
Results: We observed a converging motion between two opposite polarity sunspots that form the primary magnetic polarity inversion line (PIL), along which resides filament material before eruption. Positive-flux magnetic elements, perhaps moving magnetic features (MMFs) flowing from the spot region, appear north of the spots, and the eruption onset occurs where these features cancel repeatedly in a negative-polarity region north of the sunspots. An ejection of material observed in Hα and EUV marks the start of the filament eruption (its “fast-rise”). The start of the ejection is accompanied by a sudden brightening across the PIL at the jet's base, observed in both broad-band images and in EIS. Small-scale transient brightenings covering a wide temperature range (Log Te = 4.8-6.3) are also observed in the onset region prior to eruption. The preflare transient brightenings are characterized by sudden, localized density enhancements (to above Log ne [ cm-3] = 9.75, in Fe XIII) that appear along the PIL during a time when pre-flare brightenings were occurring. The measured densities in the eruption onset region outside the times of those enhancements decrease with temperature. Persistent downflows (red-shifts) and line-broadening (Fe XII) are present along the PIL.
Conclusions: The array of observations is consistent with the pre-eruption sheared-core magnetic field being gradually destabilized by evolutionary tether-cutting flux cancelation that was driven by converging photospheric flows, and the main filament ejection being triggered by flux cancelation between the positive flux elements and the surrounding negative field. A definitive statement however on the eruption's ultimate cause would require comparison with simulations, or additional detailed observations of other eruptions occurring in similar magnetic circumstances.

The video that accompanies Fig. 3 is only available in electronic form at http://www.aanda.org Title: Active region moss. Basic physical parameters and their temporal variation Authors: Tripathi, D.; Mason, H. E.; Del Zanna, G.; Young, P. R. Bibcode: 2010A&A...518A..42T Altcode: 2010arXiv1005.2220T Context. Active region moss are transition region phenomena, first noted in the images recorded by the Transition Region and Coronal Explorer (TRACE) in λ171. Moss regions are thought to be the footpoints of hot loops (3-5 MK) seen in the core of active regions. These hot loops appear “fuzzy” (unresolved). Therefore, it is difficult to study the physical plasma parameters in individual hot core loops and hence their heating mechanisms. Moss regions provide an excellent opportunity to study the physics of hot loops. In addition, they allow us to study the transition region dynamics in the footpoint regions.
Aims: To derive the physical plasma parameters such as temperature, electron density, and filling factors in moss regions and to study their variation over a short (an hour) and a long time period (5 consecutive days).
Methods: Primarily, we have analyzed spectroscopic observations recorded by the Extreme-ultraviolet Imaging Spectrometer (EIS) aboard Hinode. In addition we have used supplementary observations taken from TRACE and the X-Ray Telescope (XRT) aboard Hinode.
Results: The moss emission is strongest in the Fe XII and Fe XIII lines. Based on analyses using line ratios and emission measure we found that moss regions have a characteristic temperature of log T[K] = 6.2. The temperature structure in moss region remains almost identical from one region to another and it does not change with time. The electron densities measured at different locations in the moss regions using Fe XII ratios are about 1-3 × 1010 cm-3 and about 2-4 × 109 cm-3 using Fe XIII and Fe XIV. The densities in the moss regions are similar in different places and show very little variation over short and long time scales. The derived electron density substantially increased (by a factor of about 3-4 or even more in some cases) when a background subtraction was performed. The filling factor of the moss plasma can vary between 0.1-1 and the path length along which the emission originates is from a few 100 to a few 1000 kms long. By combining the observations recorded by TRACE, EIS and XRT, we find that the moss regions correspond to the footpoints of both hot and warm loops. Title: VizieR Online Data Catalog: IRON project. LXVIII (Del Zanna+, 2010) Authors: Del Zanna, G.; Storey, P. J.; Mason, H. E. Bibcode: 2010yCat..35140040D Altcode: 2010yCat..35149040D ************************************************************************** * * * Sorry, but the author(s) never supplied the tabular material * * (detailed tables) as announced in the paper. * ************************************************************************** Title: Plasma Flows in Coronal Loops Authors: Young, Peter R.; Dwyer, B. O.; Mason, H. E. Bibcode: 2010AAS...21630004Y Altcode: A survey of plasma flows in coronal loops is underway using data from the Hinode/EIS instrument. The principal target is a study of flows in 1 MK (so-called 'warm' loops). Using emission lines formed between logT=5.6 and 6.2 it is possible to study the temperature dependence of the flows, and also the density of the emitting material. The results will be critical to making a definitive statement about whether apparent motions seen in TRACE 171 movies are due to actual mass motion or wave propagation. In addition we will also comment on the relation between the flows in warm loops and those in the newly-discovered active region outflow regions found by Hinode. Title: Atomic data from the IRON project. LXVIII. Electron impact excitation of Fe xi Authors: Del Zanna, G.; Storey, P. J.; Mason, H. E. Bibcode: 2010A&A...514A..40D Altcode: A new R-matrix scattering calculation for electron collisional excitation of Fe xi is presented and compared to earlier calculations. The calculation includes 145 LS terms and 465 fine-structure levels and uses the intermediate-coupling frame transformation method (ICFT). We discuss the strong interactions that exist between three J = 1 levels in the 3s2 3p3 3d electron configuration. These levels give rise to strong lines in the EUV spectrum and their energies and identifications have been the source of much confusion in the literature. We show that the oscillator and collision strengths linking these levels to the ground levels of the ion are very sensitive to the choice of configuration basis and argue that most earlier calculations have failed to represent these levels adequately.

Detailed tables of the present data are available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/514/A40 Title: VizieR Online Data Catalog: IRON Project. LVIII. (Storey+, 2005) Authors: Storey, P. J.; Del Zanna, G.; Mason, H. E.; Zeippen, C. J. Bibcode: 2010yCat..34330717S Altcode: A new calculation of rate coefficients for electron collisional excitation of Fe XII is presented and compared to earlier calculations. Significant differences are found with all earlier work due to the inclusion of resonance processes that have not previously been considered and to the use of the intermediate coupling frame transformation method. The resulting dataset of collision strengths is shown to resolve many of the outstanding discrepancies between theory and solar observations. In particular, density sensitive line ratios in Fe XII now indicate electron densities close to those derived from other ions of comparable ionization potential.

************************************************************************** * * * Sorry, but the author(s) never supplied the tabular material * * announced in the paper * * * ************************************************************************** Title: Two types of magnetic flux cancelation in the solar eruption of 2007 May 20 Authors: Sterling, Alphonse; Moore, Ronald; Mason, Helen Bibcode: 2010cosp...38.1946S Altcode: 2010cosp.meet.1946S We study a solar eruption on 2007 May 20, in an effort to understand the cWe study a solar eruption of 2007 May 20, in an effort to understand the cause of the eruption's onset. The event produced a GOES class B6.7 flare peaking at 05:56 UT, while ejecting a surge/filament and producing a coronal mass ejection (CME). We examine several data sets, including Hα images from the Solar Optical Telescope (SOT) on Hinode, EUV images from TRACE, and line-of-sight magnetograms from SoHO/MDI. Flux cancelation occurs among two different sets of flux elements inside of the erupting active region: First, for several days prior to eruption, opposite-polarity sunspot groups inside the region move toward each other, leading to the cancelation of ∼ 1021 Mx of flux over three days. Second, within hours prior to the eruption, positive-polarity moving magnetic features (MMFs) flowing out of the positive-flux spots at ∼ 1 km/s repeatedly cancel with field inside a patch of negative-polarity flux located north of the sunspots. The filament erupts as a surge whose base is rooted in the location where the MMF cancelation occurs, while during the eruption that filament flows out along the polarity inversion line between the converging spot groups. We conclude that a plausible scenario is that the converging spot fields brought the magnetic region to the brink of instability, and the MMF cancelation pushed the system "over the edge," triggering the eruption. This work was funded by NASA's Science Mission Directorate thought the Living With a Star Targeted Research and Technology Program, the Supporting Research and Program, and the Hinode project. Title: Diagnostics of Active Region Loops Observed with Hinode/EIS Authors: Tripathi, D.; Mason, H. E.; Dwivedi, B. N.; Del Zanna, G. Bibcode: 2009ASPC..415..260T Altcode: The Extreme Ultraviolet Imaging Spectrometer (EIS) on board Hinode provides us with an excellent opportunity to study the physical parameters in spatially resolved coronal structures. In this paper we have carried out a study of active region loops using observations from the EIS. The active region was observed on 2007 Ma 19 using the 1 arcsec slit of EIS. At coronal temperatures, we find that electron densities measured from Fe XII and Si X line ratios decrease along the loop length, being ≈10100 cm-3 at foot point and ≈108.5 cm-3 at a height of about 75 Mm. However, the electron densities measured from the Mg VII line ratios (at a transition region temperature) show significantly lower values at the foot point. The electron temperature along the loop increases with height from ≈0.8 MK (at foot point) to ≈1.5 MK (at a height of 75 Mm). The temperature diagnostics using EM-loci at different locations along the loop show that the loop is ``nearly isothermal'' or ``mildly multi-thermal'' along the LOS. These measurements provide important constraints on the theoretical modelling of coronal loops. Title: Multi-Instrument Campaigns to Observe the Off-Limb Corona Authors: Del Zanna, G.; Andretta, V.; Poletto, G.; Teriaca, L.; Ko, Y. -K.; Mason, H. E.; Vourdilas, A.; Bemporad, A.; Magri, M. Bibcode: 2009ASPC..415..315D Altcode: We briefly describe two multi-instrument campaigns we coordinated to observe the off-limb corona in 2007, with some preliminary results. The first one (Hinode HOP 7) was a SOHO/Hinode/TRACE/STEREO/Ulysses week-long campaign during the SOHO-Ulysses quadrature in 2007 May. We could not achieve all of our goals, however we were very fortunate in that the ``Del Zanna'' active region appeared on the Sun at the right longitude, and that a filament eruption and a CME were observed. Of particular significance is the finding of large (100 km s-1) non-thermal broadenings in all coronal lines observed by Hinode/EIS in the region where the filament was erupting. The second campaign (Hinode HOP 44) involved SOHO (CDS, SUMER, UVCS), Hinode, and TRACE to measure the physical parameters of plume/interplume regions in the polar coronal holes from the low corona to 1.7 solar radii, on 30/10-4/11. We obtained a good set of observations, however various instrumental constraints and the lack of fully developed plumes limited our goals. Title: Temperature Tomography of a Coronal Sigmoid Supporting the Gradual Formation of a Flux Rope Authors: Tripathi, Durgesh; Kliem, Bernhard; Mason, Helen E.; Young, Peter R.; Green, Lucie M. Bibcode: 2009ApJ...698L..27T Altcode: 2009arXiv0904.4782T Multiwavelength observations of a sigmoidal (S-shaped) solar coronal source by the EUV Imaging Spectrometer and the X-Ray Telescope aboard the Hinode spacecraft and by the EUV Imager aboard STEREO are reported. The data reveal the coexistence of a pair of J-shaped hot arcs at temperatures T>2 MK with an S-shaped structure at somewhat lower temperatures (T ≈ 1-1.3 MK). The middle section of the S-shaped structure runs along the polarity inversion line of the photospheric field, bridging the gap between the arcs. Flux cancellation occurs at the same location in the photosphere. The sigmoid forms in the gradual decay phase of the active region, which does not experience an eruption. These findings correspond to the expected signatures of a flux rope forming, or being augmented, gradually by a topology transformation inside a magnetic arcade. In such a transformation, the plasma on newly formed helical field lines in the outer flux shell of the rope (S-shaped in projection) is expected to enter a cooling phase once the reconnection of their parent field line pairs (double-J shaped in projection) is complete. Thus, the data support the conjecture that flux ropes can exist in the corona prior to eruptive activity. Title: CHIANTI - an atomic database for emission lines. IX. Ionization rates, recombination rates, ionization equilibria for the elements hydrogen through zinc and updated atomic data Authors: Dere, K. P.; Landi, E.; Young, P. R.; Del Zanna, G.; Landini, M.; Mason, H. E. Bibcode: 2009A&A...498..915D Altcode: Aims: The goal of the CHIANTI atomic database is to provide a set of atomic data for the interpretation of astrophysical spectra emitted by collisionally dominated, high temperature, optically thin sources.
Methods: A complete set of ground level ionization and recombination rate coefficients has been assembled for all atoms and ions of the elements of H through Zn and inserted into the latest version of the CHIANTI database, CHIANTI 6. Ionization rate coefficients are taken from the recent work of Dere (2007, A&A, 466, 771) and recombination rates from a variety of sources in the literature. These new rate coefficients have allowed the calculation of a new set of ionization equilibria and radiative loss rate coefficients. For some ions, such as Fe VIII and Fe IX, there are significant differences from previous calculations. In addition, existing atomic parameters have been revised and new atomic parameters inserted into the database.
Results: For each ion in the CHIANTI database, elemental abundances, ionization potentials, atomic energy levels, radiative rates, electron and proton collisional rate coefficients, ionization and recombination rate coefficients, and collisional ionization equilibrium populations are provided. In addition, parameters for the calculation of the continuum due to bremsstrahlung, radiative recombination and two-photon decay are provided. A suite of programs written in the Interactive Data Language (IDL) are available to calculate line and continuum emissivities and other properties. All data and programs are freely available at http://wwwsolar.nrl.navy.mil/chianti Title: CHIANTI Version 6.0 - Inclusion of Ionization and Recombination Rates Authors: Dere, Kenneth P.; Landi, E.; Young, P.; Del Zanna, G.; Mason, H.; Landini, M. Bibcode: 2009SPD....40.1504D Altcode: A new version of the CHIANTI atomic database for astrophysical spectroscopy is being prepared for imminent release. This will constitute Version 6.0. The main focus of this release is the inclusion of ionization cross-sections and rate coefficients from Dere (2007) and recombination rate coefficients from the literature, in particular, the calculations of Badnell and colleagues. A new set of ionization equilibria have been calculated from these rate coefficients. These show some significant differences from previous calculations. Atomic data for many ions have been revised and new calculations are included that enable the calculation of spectra of ions new to the CHIANTI database. The radiative loss function has been calculated based on the CHIANTI Version 6 database for both coronal and photospheric abundances.

A paper describing CHIANTI Version 6.0 in detail has been accepted for publication in Astronomy and Astrophysics. Title: Active Region Loops: Hinode/Extreme-Ultraviolet Imaging Spectrometer Observations Authors: Tripathi, Durgesh; Mason, Helen E.; Dwivedi, Bhola N.; del Zanna, Giulio; Young, Peter R. Bibcode: 2009ApJ...694.1256T Altcode: 2009arXiv0901.0095T We have carried out a study of active region loops using observations from the Extreme-ultraviolet Imaging Spectrometer (EIS) on board Hinode using 1'' raster data for an active region observed on 2007 May 19. We find that active region structures which are clearly discernible in cooler lines (≈1 MK) become "fuzzy" at higher temperatures (≈2 MK). The active region was comprised of redshifted emissions (downflows) in the core and blueshifted emissions (upflows) at the boundary. The flow velocities estimated in the two regions located near the footpoints of coronal loop showed redshifted emission at transition region temperature and blueshifted emission at coronal temperature. The upflow speed in these regions increased with temperature. For more detailed study we selected one particular well-defined loop. Downward flows are detected along the coronal loop, being stronger in lower-temperature lines (rising up to 60 km s-1 near the footpoint). The downflow was localized toward the footpoint in transition region lines (Si VII) and toward the loop top in high-temperature line (Fe XV). By carefully accounting for the background emission we found that the loop structure was close to isothermal for each position along the loop, with the temperature rising from around 0.8 MK to 1.5 MK from the close to the base to higher up toward the apex (≈75 Mm). We derived electron density using well-established line ratio diagnostic techniques. Electron densities along the active region loop were found to vary from 1010 cm-3 close to the footpoint to 108.5 cm-3 higher up. A lower electron density, varying from 109 cm-3 close to the footpoint to 108.5 cm-3 higher up, was found for the lower temperature density diagnostic. Using these densities we derived filling factors in along the coronal loop which can be as low as 0.02 near the base of the loop. The filling factor increased with projected height of the loop. These results provide important constraints on coronal loop modeling. Title: Partially-erupting prominences: a comparison between observations and model-predicted observables Authors: Tripathi, D.; Gibson, S. E.; Qiu, J.; Fletcher, L.; Liu, R.; Gilbert, H.; Mason, H. E. Bibcode: 2009A&A...498..295T Altcode: 2009arXiv0902.1228T Aims: We investigate several partially-erupting prominences to study their relationship with other CME-associated phenomena and compare these observations with observables predicted by a model of partially-expelled-flux-ropes (Gibson & Fan 2006a, ApJ, 637, L65; 2006b, J. Geophys. Res., 111, 12103).
Methods: We studied 6 selected events with partially-erupting prominences using multi-wavelength observations recorded by the Extreme-ultraviolet Imaging Telescope (EIT), Transition Region and Coronal Explorer (TRACE), Mauna Loa Solar Observatory (MLSO), Big Bear Solar Observatory (BBSO), and Soft X-ray Telescope (SXT). The observational features associated with partially-erupting prominences were then compared with the predicted observables from the model.
Results: The partially-expelled-flux-rope (PEFR) model can explain the partial eruption of these prominences, and in addition predicts a variety of other CME-related observables that provide evidence of internal reconnection during eruption. We find that all of the partially-erupting prominences studied in this paper exhibit indirect evidence of internal reconnection. Moreover, all cases showed evidence of at least one observable unique to the PEFR model, e.g., dimmings external to the source region and/or a soft X-ray cusp overlying a reformed sigmoid.
Conclusions: The PEFR model provides a plausible mechanism to explain the observed evolution of partially-erupting-prominence-associated CMEs in our study. Title: Are Coronal Loops Isothermal or Multithermal? Authors: Schmelz, J. T.; Nasraoui, K.; Rightmire, L. A.; Kimble, J. A.; del Zanna, G.; Cirtain, J. W.; DeLuca, E. E.; Mason, H. E. Bibcode: 2009ApJ...691..503S Altcode: 2009arXiv0901.3281S Surprisingly few solar coronal loops have been observed simultaneously with TRACE and SOHO/Coronal Diagnostics Spectrometer (CDS), and even fewer analyses of these loops have been conducted and published. The SOHO Joint Observing Program 146 was designed in part to provide the simultaneous observations required for in-depth temperature analysis of active region loops and determine whether these loops are isothermal or multithermal. The data analyzed in this paper were taken on 2003 January 17 of AR 10250. We used TRACE filter ratios, emission measure loci, and two methods of differential emission measure analysis to examine the temperature structure of three different loops. TRACE and CDS observations agree that Loop 1 is isothermal with log T = 5.85, both along the line of sight as well as along the length of the loop leg that is visible in the CDS field of view. Loop 2 is hotter than Loop 1. It is multithermal along the line of sight, with significant emission between 6.2 < log T< 6.4, but the loop apex region is out of the CDS field of view so it is not possible to determine the temperature distribution as a function of the loop height. Loop 3 also appears to be multithermal, but a blended loop that is just barely resolved with CDS may be adding cool emission to the Loop 3 intensities and complicating our results. So, are coronal loops isothermal or multithermal? The answer appears to be yes. Title: Magnetic flux cancellation associated with a recurring solar jet observed with Hinode, RHESSI, and STEREO/EUVI Authors: Chifor, C.; Isobe, H.; Mason, H. E.; Hannah, I. G.; Young, P. R.; Del Zanna, G.; Krucker, S.; Ichimoto, K.; Katsukawa, Y.; Yokoyama, T. Bibcode: 2008A&A...491..279C Altcode: Aims: We study the physical properties of a recurring solar active region jet observed in X-rays and extreme-ultraviolet (EUV).
Methods: Multi-wavelength data from all three instruments on board Hinode were analysed. X-ray imaging and spectroscopy of the microflaring emission associated with the jets was performed with the Reuven Ramaty High Energy Spectroscopic Imager (RHESSI). Associated EUV jets were observed with the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI)/Extreme Ultraviolet Imager (EUVI) on board STEREO.
Results: We found a correlation between recurring magnetic flux cancellation close to a pore, the X-ray jet emission, and associated Ca II H ribbon brightenings. We estimated the lower limit for the decrease in magnetic energy associated with the X-ray jet emission at 3 × 1029 erg. The recurring plasma ejection was observed simultaneously at EUV and X-ray temperatures, associated with type III radio bursts and microflaring activity at the jet footpoint.
Conclusions: The recurring jet (EUV and X-ray) emissions can be attributed to chromospheric evaporation flows due to recurring coronal magnetic reconnection. In this process, the estimated minimum loss in the magnetic energy is sufficient to account for the total energy required to launch the jet.

Movie of Fig. 3 is only available in electronic form via http://www.aanda.org Title: Chapter 7: Active Region Diagnostics Authors: Mason, H. E.; Tripathi, D. Bibcode: 2008psa..book..127M Altcode: Active regions present us with complex and dynamic structures, which look relatively simple, but are in fact very difficult to model and explain. An active region is a region on the Sun where the magnetic field breaks through the surface (photosphere and chromosphere) to form giant arches of hot plasma. The magnetic field is stronger than in surrounding regions and the plasma is hotter, so emits strongly in UV and X-ray radiation. Figures 7.1 and 7.2 show UV images of the Sun taken with the Transition Region and Coronal Explorer (TRACE) spacecraft and the Extreme Ultraviolet Imaging Telescope (EIT) aboard the Solar and Heliospheric Observatory (SOHO) spacecraft. The hot plasma (around a million degree) traces out the magnetic field structures... Title: Active Region Microflares From Hinode and RHESSI Authors: Chifor, C.; Hannah, I. G.; Mason, H. E.; Isobe, H.; Yokoyama, T.; Young, P. R.; Tripathi, D. Bibcode: 2008ASPC..397..164C Altcode: We are studying microflares (A, B-C class flares) in active regions using coordinated observations from Hinode and RHESSI. Hinode/EIS has unprecedented diagnostic power for small, transient activity in the solar corona, providing temperature, density, and velocity information. For this purpose, we designed and ran an EIS observing sequence to provide high-cadence data at both transition region and coronal temperatures. A preliminary analysis of these observations is reported, with one data set given as an example. Title: Source Region Evolution of the Solar Wind Disappearance Event of 11 May 1999 Authors: Janardhan, P.; Tripathi, D.; Mason, H. E. Bibcode: 2008ESPM...122.118J Altcode: A recent, detailed study of the well known "solar wind disappearance event" of 11 May 1999 traced its origin to a coronal hole lying adjacent to a large active region, AR8525

in Carrington rotation 1949. The active region was located at central meridian on 05 May 1999 when the flows responsible for this event began. In this paper we examine the evolution of the active region-coronal hole complex during 5-6 May 1999 to study the changes that apparently played a key role in causing this disappearance event. To study the evolution of the solar source region of the disappearance event of 11 May 1999 we have used images from the Soft X-ray Telescope (SXT), the Extreme-ultraviolet Imaging Telescope (EIT) and the Michelson Doppler Imager (MDI) to examine the evolution of the coronal hole and active region complex at the source region of the disappearance event. We find a dynamic evolution taking place in the coronal hole-active region boundary at the source region of the disappearance event of 11 May 1999. Based on the combined observations it appears that the rapid evolution seen in the coronal hole is due to reconnection's taking place between the newly emerging flux and the open field regions from the coronal hole and the active region-coronal hole boundary regions. This evolution, which is found to reduce the area of the coronal hole, is accompanied by the formation of new loops in EUV images which are spatially and temporally correlated with emerging flux regions as seen in MDI data.

As opposed to the well known drivers of space weather phenomena like CME's or large flares, disappearance events are not associated with explosive solar phenomena. However, they do produce other observable effects that are not fully understood. In the period leading up to the disappearance event of 11 May 1999, our observations, during quiet solar conditions and in the absence of CMEs, provide the first clear evidence for Sun-Earth connection originating from an evolving active region-coronal hole region located at central meridian. With the exception of corotating interacting regions, these observations provide the first link between the Sun and space weather effects at 1 AU, arising from non-explosive solar events. Title: Density Structure in Active Regions from Hinode/EIS Authors: Tripathi, D.; Mason, H. E.; Young, P. R.; Chifor, C.; Del Zanna, G. Bibcode: 2008ASPC..397...45T Altcode: The Extreme-ultraviolet Imaging Spectrometer (EIS) on board Hinode provides an excellent opportunity to study the physical plasma parameters in spatially resolved coronal features. In this paper we present the density structure in an active region at many different temperatures. The active region was rastered on May 01, 2007 with the 2^{''} slit. We find that the electron density is highest in the core of the active region where it exceeds log_{10} N_e = 10.5. Title: Nonthermal and thermal diagnostics of a solar flare observed with RESIK and RHESSI Authors: Dzifčáková, E.; Kulinová, A.; Chifor, C.; Mason, H. E.; Del Zanna, G.; Sylwester, J.; Sylwester, B. Bibcode: 2008A&A...488..311D Altcode: Aims: We aim to prove and diagnose the occurrence of nonthermal electron distributions in solar flare plasma using X-ray spectral observations.
Methods: An M4.9 flare on 2003 January 7/8 was observed with the RESIK instrument in the 3-6 Å wavelength range (2-4 keV) and with RHESSI at energies above 6 keV. The temporal behavior of RESIK flare spectra has been analyzed for two different types of velocity distributions - a thermal (Maxwellian) distribution and a nonthermal plasma distribution of free electrons. The Si XIV, Si XIII, and Si XIId satellite lines observed with RESIK in the 5-6 Å range were used to determine the degree of deviation from Maxwellian, and the equivalent non-Maxwellian pseudo-temperature, τ. The diagnostics presented are sensitive to the shape of the distribution in the energy range where the maximum of the electron distribution occurs (where the bulk of electrons reside) and does not include the influence of the shape of the high-energy tail of the distribution. Under the assumption of a Maxwellian distribution of electron velocities, the plasma temperature was determined from an emission measure (EM) loci analysis and a differential emission measure (DEM) analysis of RESIK spectra. The high-energy end of the flare radiative emission was investigated through RHESSI spectral analysis.
Results: The nonthermal analysis of RESIK spectra has shown that the largest deviations of the plasma electron distribution from Maxwellian appeared during the impulsive phase of the flare. The decay phase spectra had an almost isothermal character. The pseudo-temperature, τ, reached its maximum around the peak time of the soft and hard X-ray fluxes. The temporal behavior of the temperatures derived from the thermal analysis was similar to the behavior of the nonthermal pseudo-temperature. The values of the pseudo-temperature were consistent with the temperatures obtained in both thermal analyses, but lower than the temperatures derived from the slope of the RHESSI continua. In comparison with the synthetic isothermal or multithermal spectra, the nonthermal synthetic spectra fitted the observed Si XIId satellite lines much more closely (the error is less than 10%). The fluxes in the Si XIId satellite lines in isothermal or multithermal spectra have been underestimated by a factor of three or more in comparison to the observed fluxes. The value of this factor varies with time and it is different for the different satellite lines.
Conclusions: Evidence was found for considerable deviations of the distribution of free electrons from Maxwellian in the plasma during a solar flare. These occurred mainly during the flare impulsive phase and can be diagnosed using existing X-ray spectral observations. Title: The solar wind disappearance event of 11 May 1999: source region evolution Authors: Janardhan, P.; Tripathi, D.; Mason, H. E. Bibcode: 2008A&A...488L...1J Altcode: 2008arXiv0807.2697J Context: A recent, detailed study of the well-known “solar wind disappearance event” of 11 May 1999 traced its origin to a coronal hole (CH) lying adjacent to a large active region (AR), AR8525 in Carrington rotation 1949. The AR was located at central meridian on 05 May 1999 when the flows responsible for this event began. We examine the evolution of the AR-CH complex during 5-6 May 1999 to study the changes that apparently played a key role in causing this disappearance event.
Aims: To study the evolution of the solar source region of the disappearance event of 11 May 1999.
Methods: Using images from the Soft X-ray Telescope (SXT), the Extreme-ultraviolet Imaging Telescope (EIT) and the Michelson Doppler Imager (MDI) to examine the evolution of the CH and AR complex at the source region of the disappearance event.
Results: We find a dynamic evolution taking place in the CH-AR boundary at the source region of the disappearance event of 11 May 1999. This evolution, which is found to reduce the area of the CH, is accompanied by the formation of new loops in EUV images that are spatially-and-temporally correlated with emerging flux regions as seen in MDI data.
Conclusions: In the period leading up to the disappearance event of 11 May 1999, our observations, during quiet solar conditions and in the absence of CMEs, provide the first clear evidence for Sun-Earth connection originating from an evolving AR-CH region located at central meridian. With the exception of corotating interacting regions (CIR), these observations provide the first link between the Sun and space weather effects at 1 AU, arising from non-explosive solar events.

2 movies are only available in electronic form at http://www.aanda.org Title: Magnetic Flux Cancelation Leading to the Eruption of a Coronal Mass Ejection: Observations from Hinode, SOHO, TRACE, and STEREO Authors: Sterling, A. C.; Chifor, C.; Mason, H.; Moore, R. L. Bibcode: 2008AGUSMSP23B..05S Altcode: We study a solar eruption involving ejection of a filament on 2007 May 20, using instruments on Hinode, STEREO, TRACE, and SOHO. We observe the filament in EUV from TRACE and STEREO, and in H-alpha from SOT on Hinode. We also see the eruption in soft X-rays with XRT on Hinode, and in several EUV lines from EIS on Hinode. SOHO/MDI magnetograms show that converging motion between opposite-polarity sunspots in the region result in expansion of large-scale loops overlying the region's primary magnetic neutral line, along which sits filament material prior to its eruption. The source location of an EUV filament's surge-like ejection is a negative-polarity magnetic region that is north of the interacting spots, and patches of magnetic field flow at ~ 0.5 km/s from the positive converging spots into the negative region in the north. Apparently, repeated episodes of flux cancelation occur where the flowing positive flux collides with the northern negative flux, and the source of the EUV filament's ejection is near this cancelation site. Spectroscopic data from EIS are available for a portion of the active region that includes the northern cancelation site, and from these data we obtain bulk-flow velocities, line-broadening turbulent velocities, and densities of plasma in the region. The array of observations is consistent with the pre-eruption sheared-core magnetic arcade being gradually destabilized by evolutionary tether-cutting flux cancelation that was driven by converging photospheric flows. Title: Density structure of an active region and associated moss using Hinode/EIS Authors: Tripathi, D.; Mason, H. E.; Young, P. R.; Del Zanna, G. Bibcode: 2008A&A...481L..53T Altcode: 2008arXiv0802.3311T Context: Studying the problem of active region heating requires precise measurements of physical plasma parameters such as electron density, temperature, etc. It is also important to understand the relationship of coronal structures with the magnetic field. The Extreme-ultraviolet Imaging Spectrometer (EIS) aboard Hinode provides a rare opportunity to derive electron density simultaneously at different temperatures.
Aims: We study the density structure and characterise plasma in active regions and associated moss regions. In addition, we study its relationship to the photospheric magnetic field.
Methods: We used data recorded by the EIS, together with magnetic field measurements from the Michelson Doppler Imager (MDI) aboard SoHO and images recorded with the Transition Region And Coronal Explorer (TRACE) and X-Ray Telescope (XRT/Hinode).
Results: We find that the hot core of the active region is densest with values as high as 1010.5 cm-3. The electron density estimated in specific regions in the active region moss decreases with increasing temperature. The moss areas were located primarily on one side of the active region, and they map the positive polarity regions almost exactly. The density within the moss region was highest at log T=5.8{-}6.1, with a value around 1010.0{-10.5} cm-3. The moss densities were highest in the strong positive magnetic field region. However, there was no such correlation for the negative polarity areas, where there was a large sunspot. Title: An active region jet observed with Hinode Authors: Chifor, C.; Young, P. R.; Isobe, H.; Mason, H. E.; Tripathi, D.; Hara, H.; Yokoyama, T. Bibcode: 2008A&A...481L..57C Altcode: Aims:We study the physical properties of an active region (AR) jet in order to probe the mechanisms responsible for it.
Methods: We report 2007 January 15/16 observations of a recurring jet situated on the west side of NOAA AR 10938. Multi-wavelength data from all three instruments onboard Hinode were analysed. This paper focuses on one instance of a jet observed with the Hinode/EUV Imaging Spectrometer (EIS). Using EIS raster data we measured the temperatures, Doppler shifts, density, and filling factor.
Results: A strong blue-shifted component and an indication of a weak red-shifted component at the base of the jet was observed around Log Te = 6.2. The up-flow velocities exceeded 150 km s-1. The jet component was seen over a range of temperatures between 5.4 and 6.4 in Log T_e. Using Fe XII λ186 and λ195 line ratios, we measured densities above Log Ne = 11 for the high-velocity up-flow component. We found that the density of the high-velocity up-flow increases with velocity. We estimate the filling factor in the jet up-flow to be <0.03. With the Hinode/Solar Optical Telescope (SOT), we observed recurrent (quasi periodic) magnetic flux cancelations just before the recurrent jet emission was seen in images taken with the X-ray Telescope (XRT).
Conclusions: The high-velocity up-flows, together with the density dependence on velocity, support an evaporation scenario for the acceleration of this jet. The high density and small filling factor, coupled with the high Doppler velocities are strongly suggestive of multiple small-scale magnetic reconnection events being responsible for the production of both EUV and X-ray jets. Title: Computation of Non-Maxwellian Electron Excitation Rates for Ions of Astrophysical Interest: Fe XV - A Test Case Authors: Dzifčáková, Elena; Mason, Helen Bibcode: 2008SoPh..247..301D Altcode: 2008SoPh..tmp...14D Dzifčáková previously developed a method for calculating the influence of nonthermal electron-velocity distributions on the intensities of spectral lines (Solar Phys.234, 243, 2006; In: Lacoste, H., Ouwehand, L. (eds.) SOHO-17. 10 Years of SOHO and Beyond, SP-617, ESA, Noordwijk, 89, 2006). Here, we study this method in detail for the test case: Fe XV. It involves fitting a parametric form to the electron-excitation data in the CHIANTI atomic database. We assess the reliability of these fits by comparing them with the source atomic data, both Upsilons (Maxwellian-averaged collision strengths) and the original collision strengths. An accuracy for the method of better than 15% is deduced for all transitions, with a much higher accuracy than this for the strong electric-dipole transitions. A κ-distribution, which has an increased number of electrons in the high-energy tail of the distribution, is considered as an example. The shape of the κ-distribution affects the electron-excitation rate and thus the relative intensities of the spectral lines. Since the shape of the electron distribution function also influences the ionization balance of Fe, both effects change the final intensities of the lines. Synthetic spectra for Fe XV and Fe XVI in the wavelength range 50 - 80 Å are presented for a κ-distribution and compared with solar observations. Title: Solar Transition Region Features Observed with Hinode/EIS Authors: Young, Peter R.; Del Zanna, Giulio; Mason, Helen E.; Doschek, George A.; Culhane, Len; Hara, Hirohisa Bibcode: 2007PASJ...59S.727Y Altcode: 2007arXiv0706.1856Y Two types of solar active region feature prominent at transition region temperatures are identified in Hinode/EIS data of AR 10938 taken on 2007 January 20. The footpoints of 1 MK TRACE loops are shown to emit strongly in emission lines formed at log T = 5.4-5.8, allowing the temperature increase along the footpoints to be clearly seen. A density diagnostic of Mg VII yields the density in the footpoints, with one loop showing a decrease from 3 × 109 cm-3 at the base to 1.5 × 109 cm-3 at a projected height of 20 Mm. The second feature is a compact active region transition region brightening which is particularly intense in O V emission (log T = 5.4) but also has a signature at temperatures up to log T = 6.3. The Mg VII diagnostic gives a density of 4 × 1010 cm-3, and emission lines of Mg VI and Mg VII show line profiles broadened by 50kms-1 and wings extending beyond ± 200kms-1. Continuum emission in the short wavelength band is also found to be enhanced, and is suggested to be free-bound emission from recombination onto He+. Title: The Temperature and Density Structure of an Active Region Observed with the Extreme-Ultraviolet Imaging Spectrometer on Hinode Authors: Doschek, George A.; Mariska, John T.; Warren, Harry P.; Culhane, Len; Watanabe, Tetsuya; Young, Peter R.; Mason, Helen E.; Dere, Kenneth P. Bibcode: 2007PASJ...59S.707D Altcode: The Extreme-Ultraviolet Imaging Spectrometer (EIS) on Hinode produces high resolution spectra that can be combined via rasters into monochromatic images of solar structures, such as active regions. Electron temperature and density maps of the structures can be obtained by imaging the structures in different spectral lines with ratios sensitive to either temperature or density. Doppler maps and ion temperature maps can be made from spectral line wavelengths and profiles, respectively. In this paper we discuss coronal temperature and density distributions within an active region, illustrating the power of EIS for solar plasma diagnostics. Title: EUV Emission Lines and Diagnostics Observed with Hinode/EIS Authors: Young, Peter R.; Del Zanna, Giulio; Mason, Helen E.; Dere, Ken P.; Landi, Enrico; Landini, Massimo; Doschek, George A.; Brown, Charles M.; Culhane, Len; Harra, Louise K.; Watanabe, Tetsuya; Hara, Hirohisa Bibcode: 2007PASJ...59S.857Y Altcode: 2007arXiv0706.1857Y Quiet Sun and active region spectra from the Hinode/EIS instrument are presented, and the strongest lines from different temperature regions discussed. A list of emission lines recommended to be included in EIS observation studies is presented based on analysis of blending and diagnostic potential using the CHIANTI atomic database. In addition we identify the most useful density diagnostics from the ions covered by EIS. Title: Application of CHIANTI to Solar-B Authors: Dere, K.; Landi, E.; Del Zanna, G.; Young, P.; Mason, H.; Landini, M. Bibcode: 2007ASPC..369...35D Altcode: CHIANTI (http://wwwsolar.nrl.navy.mil/chianti.html) has been developed to support the interpretation of solar and astrophysical spectroscopic measurements. The most recent release, version 5.0 (Landi et al. 2005) presents an improvement over previous versions by including new large scale datasets for Fe ions from Fe XVII to Fe XXIV for X-ray emission and improved atomic data for EUV line emission. We will demonstrate how this can be applied to the analysis of XRT and EIS data, in particular. For example, new excitation rates for Fe XII have resolved a long standing problem in the use of Fe XII line ratios as accurate density diagnostics. Current work involves improvements to ionization and recombination rates which will also be useful in the interpretation of Solar-B data Title: Nonthermal Velocities in Solar Active Regions Observed with the Extreme-Ultraviolet Imaging Spectrometer on Hinode Authors: Doschek, G. A.; Mariska, J. T.; Warren, H. P.; Brown, C. M.; Culhane, J. L.; Hara, H.; Watanabe, T.; Young, P. R.; Mason, H. E. Bibcode: 2007ApJ...667L.109D Altcode: We discuss nonthermal velocities in an active region as revealed by the Extreme-Ultraviolet Imaging Spectrometer (EIS) on the Hinode spacecraft. The velocities are derived from spectral line profiles in the extreme-ultraviolet (EUV) from a strong line of Fe XII at 195.12 Å by fitting each line profile to a Gaussian function. We compare maps of the full width at half-maximum values, the Fe XII spectral line intensity, the Fe XII Doppler shift, the electron temperature, and electron density. We find that the largest widths in the active region do not occur in the most intense regions, but seem to concentrate in less intense regions, some of which are directly adjacent to coronal loops, and some of which concentrate in regions which also exhibit relative Doppler outflows. The increased widths can also occur over extended parts of the active region. Title: A bright coronal downflow seen in multi-wavelength observations: evidence of a bifurcating flux-rope? Authors: Tripathi, D.; Solanki, S. K.; Mason, H. E.; Webb, D. F. Bibcode: 2007A&A...472..633T Altcode: 2008arXiv0802.3616T Aims:We study the origin and characteristics of a bright coronal downflow seen after a coronal mass ejection associated with erupting prominences on 5 March 2000.
Methods: This study extends that of Tripathi et al. (2006b, A&A, 449, 369) based on the Extreme-ultraviolet Imaging Telescope (EIT), the Soft X-ray Telescope (SXT) and the Large Angle Spectrometric Coronagraph (LASCO) observations. We combined those results with an analysis of the observations taken by the Hα and the Mk4 coronagraphs at the Mauna Loa Solar Observatory (MLSO). The combined data-set spans a broad range of temperature as well as continuous observations from the solar surface out to 30 R⊙.
Results: The downflow started at around 1.6 R⊙ and contained both hot and cold gas. The downflow was observed in the Hα and the Mk4 coronagraphs as well as the EIT and the SXT and was approximately co-spatial and co-temporal providing evidence of multi-thermal plasma. The Hα and Mk4 images show cusp-shaped structures close to the location where the downflow started. Mk4 observations reveal that the speed of the downflow in the early phase was substantially higher than the free-fall speed, implying a strong downward acceleration near the height at which the downflow started.
Conclusions: The origin of the downflow was likely to have been magnetic reconnection taking place inside the erupting flux rope that led to its bifurcation.

Movies are available in electronic form at http://www.aanda.org Title: X-ray precursors to flares and filament eruptions Authors: Chifor, C.; Tripathi, D.; Mason, H. E.; Dennis, B. R. Bibcode: 2007A&A...472..967C Altcode: Aims:To study preflare X-ray brightenings as diagnostics of the destabilisation of flare-associated erupting filaments/prominences.
Methods: We combine new observations from the Transition Region and Coronal Explorer (TRACE) and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), as well as revisit events reported in the literature to date, in order to scrutinise the preflare activity during eight flare-associated filament eruptions.
Results: The preflare activity occurs in the form of discrete, localised X-ray brightenings observed between 2 and 50 min before the impulsive phase of the flare and filament acceleration. These transient preflare brightenings are situated on or near (within 10{ arcsec} of) the polarity inversion line (PIL), coincident with emerging and/or canceling magnetic flux. The filaments begin to rise from the location of the preflare brightenings. In five out of eight events, the preflare brightenings were observed beneath the filament channel, close to the filament footpoint first observed to rise. Both thermal and nonthermal hard X-ray emissions during the preflare enhancement were detected with RHESSI, suggesting that both plasma heating and electron acceleration occurred at this time. The main energy release during the impulsive phase of the flare is observed close to (within 50{ arcsec} of) the preflare brightenings. The fast-rise phase of the filament eruption starts at the same time as the onset of the main flare or up to 5 min later.
Conclusions: The preflare brightenings are precursors to the flare and filament eruption. These precursors represent distinct, localised instances of energy release, rather than a gradual energy release prior to the main flare. The X-ray precursors represent clearly observable signatures in the early stages of the eruption. Together with the timing of the filament fast-rise at or after the main flare onset, the X-ray precursors provide evidence for a tether-cutting mechanism initially manifested as localised magnetic reconnection being a common trigger for both flare emission and filament eruption.

Movies and Appendix A are only available in electronic form at http://www.aanda.org Title: Coronal Loops: Isothermal or Multithermal? Authors: Kimble, Jason; Schmelz, J. T.; Nasraoui, K.; Cirtain, J. W.; Del Zanna, G.; DeLuca, E. E.; Mason, H. E. Bibcode: 2007AAS...210.9120K Altcode: 2007BAAS...39..207K The coronal loop data used for this analysis were taken on 2003 January 17 at 14:24:45 UT by the Coronal Diagnostic Spectrometer (CDS) aboard the Solar and Heliospheric Observatory. We use the Chianti atomic physics data base and the hybrid coronal abundances to determine temperatures and densities for positions along several loops. The traditional method used to create our differential emission measure (DEM) curves has been forward folding, but we are now using both emission measure loci plots and DEM automatic inversion to support and confirm the original conclusions. In this poster, we will look specifically at the emission measure loci analysis of three loops visible in the CDS data set. We find different results for each of these loops. One of the loops seems to be composed of isothermal plasma with Log T = 5.8 MK. The temperature does not appear to change with position, from the footpoint to the loop leg. Unfortunately, the loop top is outside the CDS field of view. Each pixel examined in the second loop seems to require a multithermal DEM distribution. For the third loop, the temperature increases and the density appears to decrease with loop height, reminiscent of traditional hydrostatic loop models. Solar physics research at the University of Memphis is supported by NSF ATM-0402729 and NASA NNG05GE68G. Title: SOHO-CDS: Thermal and Density Analysis of Coronal Loops Authors: Rightmire, Lisa; Schmelz, J. T.; Cirtain, J. W.; Del Zanna, G.; DeLuca, E. E.; Mason, H. E. Bibcode: 2007AAS...210.9121R Altcode: 2007BAAS...39..207R Data was obtained using the Coronal Diagnostic Spectrometer (CDS) instrument on the Solar and Heliospheric Observatory (SOHO). The goal of this project is to analyze the data obtained by the CDS instrument in order to determine the behavior of temperature and density of the coronal loop progressing from the foot point and moving up the loop. The loop being analyzed was observed by CDS on 2003 January 17 and the foot point was located at solar coordinates (585,-472) arcsecs. A background pixel and several pixels on the loop were selected. The background pixel intensity was then subtracted from each loop pixel intensity in order to isolate the emission from each loop pixel. The spectral line intensities of each loop pixel were analyzed to determine which spectral lines had any significant contribution to the loop intensity. The predicted and observed intensities of these significant lines were then used to create a differential emission measure (DEM) curve to best fit each loop pixel emission. Comparison of the DEM curves for each loop pixel indicates that the temperature increases and the density decreases, while progressing up the loop. Solar physics research at the University of Memphis is supported by NSF ATM-0402729 and NASA NNG05GE68G. Title: Are Coronal Loops Isothermal Or Multithermal? Yes! Authors: Schmelz, Joan T.; Nasraoui, K.; Rightmire, L.; Garst, J.; Kimble, J.; Cirtain, J.; DeLuca, E. E.; Del Zanna, G.; Mason, H. Bibcode: 2007AAS...210.9431S Altcode: 2007BAAS...39..222S Analysis of loops observed with the Coronal Diagnostics Spectrometer (CDS) and the Transition Region and Coronal Explorer (TRACE) reveal examples of both isothermal and multithermal plasma. These data were taken on 2003 January 17, and since the loops are on the disk, a lot of work was done on the details of background subtraction. The background-subtracted CDS intensities were analyzed using three methods: (1) Emission Measure Loci, (2) Forward-Folding DEM, and (3) Automatic-Inversion DEM. The first loop appears to be isothermal, with Log T = 5.8 MK. The forward-folding DEM shows a spike at this temperature and the EM Loci curves all intersect at this point. The automatic-inversion DEM results are broadened, however, as a result of the smoothing required for this method. This loop has a uniform temperature along the segment visible in the CDS field of view, and this result is confirmed using the TRACE data. The pixels along the second loop do not appear to be isothermal. The EM Loci curves do not intersect at a single point and both DEM methods show a broad curve. Other loops in this data set as well as loop evolution will be investigated if time permits. Solar physics research at the University of Memphis is supported by NSF ATM-0402729 and NASA NNG05GE68G. Title: Differential Emission Measurements on Sparse Raster Data from SOHO-CDS Authors: Garst, Jennifer W.; Schmelz, J. T.; Nasraoui, K.; Cirtain, J. W.; DeLuca, E. E.; Del Zanna, G.; Mason, H. E. Bibcode: 2007AAS...210.2517G Altcode: 2007BAAS...39..133G Two types of rasters were taken on 2003 January 17 with the Solar and Heliospheric Observatory’s Coronal Diagnostic Spectrometer. The first type contains a continuous image of coronal loops under investigation while the second, the ‘sparse raster,’ was taken at spatial intervals in order to simulate enhanced time resolution. With this technique, intensities in 14 passbands were collected at fixed positions on the solar disk every 7 minutes. The start time for the CDS observations was 06:51:27 UT and the observing sequences ran for 7 hours. The continuous rasters were interspersed with the sparse rasters. All the rasters were then co-aligned and a loop pixel and a background pixel were selected for detailed analysis. Differential emission measure was performed on the background-subtracted CDS intensities to determine the temporal evolution of the loop pixel plasma. Solar physics research at the University of Memphis is supported by NSF ATM-0402729 and NASA NNG05GE68G. Title: Coronal Diagnostics Spectrometer Observations of Coronal Loops Authors: Nasraoui, Kaouther; Schmelz, J. T.; Cirtain, J. W.; Del Zanna, G.; DeLuca, E. E.; Mason, H. E. Bibcode: 2007AAS...210.9122N Altcode: 2007BAAS...39..207N Two side by side loops from the solar disk were analyzed. These two loops were observed with the Coronal Diagnostics Spectrometer on SOHO on 2003 January 17. The first loop was best seen in Mg IX at a wavelength of 368 angstroms and a peak formation temperature of Log T = 6.0. Seven pixels on the loop and one background pixel were chosen. The intensity of the background pixel was subtracted from each of the loop pixels. Only the lines that had a significant intensity after background subtraction were considered. A differential emission measure (DEM) curve was constructed for the background subtracted data using the forward folding technique. The DEM for most of these pixels had a spike shape at Log T equal to 5.85. This result shows that the loop is isothermal at most of these pixels. The second loop was best seen in Si XII at a wavelength of 520 angstroms and a peak formation temperature of Log T = 6.3. The same procedure was followed for the data analysis. After background subtraction only some hot lines had a significant intensity and a DEM curve was constructed for each loop pixel. This time the DEM is broader with a shape that shows that the loop plasma is multithermal with a log temperature range of 6.1 to 6.5.

Solar physics research at the University of Memphis is supported by NSF ATM-0402729 and NASA NNG05GE68G. Title: Coronal Diagnostic Spectrometer Observations of Isothermal and Multithermal Coronal Loops Authors: Schmelz, J. T.; Nasraoui, K.; Del Zanna, G.; Cirtain, J. W.; DeLuca, E. E.; Mason, H. E. Bibcode: 2007ApJ...658L.119S Altcode: A data set obtained on 2003 January 17 with the Coronal Diagnostic Spectrometer (CDS) shows two loops sitting side by side on the solar disk. These loops are oriented along the CDS slit, so all pixels in each loop were observed simultaneously. So, although the instrument has a relatively slow time cadence, changes as a function of time that may occur during the CDS raster buildup will not affect the loop temperature results. Differential emission measure (DEM) analysis using a forward-folding technique shows different results for the two loops. For the first loop, the intensities of the lines that remain after background subtraction are well fit with a DEM curve that collapses to a single spike. In other words, the loop plasma at this location is isothermal. This analysis is confirmed with an emission measure loci method and agrees with the results obtained recently by other authors that show that the moderate spatial resolution of CDS can detect isothermal structures. For the second loop, the background-subtracted line intensities require a broad DEM, not consistent with isothermal plasma. This conclusion is confirmed with an automatic-inversion DEM method. In this Letter, we specifically address some of the concerns raised about CDS temperature analysis: the slow CDS temporal resolution, the moderate CDS spatial resolution, the inherent smoothing associated with DEM inversion, and line-of-sight effects on the DEM distribution. Title: Active Region Loops: Temperature Measurements as a Function of Time from Joint TRACE and SOHO CDS Observations Authors: Cirtain, J. W.; Del Zanna, G.; DeLuca, E. E.; Mason, H. E.; Martens, P. C. H.; Schmelz, J. T. Bibcode: 2007ApJ...655..598C Altcode: In this paper, we aim to quantitatively investigate the structure and time variation of quiescent active region loop structures. We coordinated a joint program of observations (JOP 146) using TRACE, to obtain high-cadence EUV images, and SOHO CDS, to obtain spectroscopic data. Loop intensities are used to determine temperature as a function of time for a single loop, taking full account of the background emission. In many locations, the emission measure loci are consistent with an isothermal structure. However, the results indicate significant changes in the loop temperature (between 1 and 2 MK) over the 6 hr observing period. It is possible that the loop structures are composed of multiple, independently heated strands with sizes less than the resolution of the imager and spectrometer. Title: A benchmark study for CHIANTI based on RESIK solar flare spectra Authors: Chifor, C.; Del Zanna, G.; Mason, H. E.; Sylwester, J.; Sylwester, B.; Phillips, K. J. H. Bibcode: 2007A&A...462..323C Altcode: Aims:To perform a benchmark analysis for the recent version of the CHIANTI atomic database (v. 5.2) based on high-resolution solar flare X-ray spectra in the range 3.4-6.1 Å from the RESIK crystal spectrometer on the CORONAS-F spacecraft.
Methods: A C5.8 flare occurring on 2003 February 22 was chosen for analysis. RESIK spectra of this flare include emission lines of He-like and H-like K, Ar, S, and Si, with some dielectronic lines. Initially, two independent plasma diagnostic techniques are employed: an emission measure (EM) loci analysis using the line flux and the line contribution function G(T_e, N_e), and a new method based on continuum fluxes and contribution functions. We further apply a differential emission measure (DEM) analysis, from which CHIANTI synthetic spectra are derived. The continuum from RESIK spectra is checked against simultaneous RHESSI and GOES observations. Comparisons of CHIANTI synthetic spectra with those from the MEKAL code in the 3.4-6.1 Å range are also presented.
Results: The emitting plasma appears multi-thermal, having one dominant temperature component determined independently from the line and continuum EM loci and DEM analyses. Consistency between line and continuum emissions requires photospheric elemental abundances (Asplund et al. 2005), with a depleted sulphur abundance. With the exception of RESIK channel 4 (5.0-6.1 Å), we find overall very good agreement between the calculated and observed intensities. From comparisons with other instruments, RESIK's precision in the continuum level is confirmed to be within the estimated 20% uncertainties in the intensity calibration. We find general agreement between CHIANTI and MEKAL isothermal spectra, but we note that the atomic data for the Si xii and Si xiii ions contained in CHIANTI are more complete.
Conclusions: .RESIK observations of both lines and continua are suitable for characterising the properties of the flaring plasma such as temperature, emission measure and elemental abundance. These spectra can be used to evaluate any atomic database. Title: EIT and TRACE responses to flare plasma Authors: Tripathi, D.; Del Zanna, G.; Mason, H. E.; Chifor, C. Bibcode: 2006A&A...460L..53T Altcode: 2008arXiv0802.3852T Aims.To understand the contribution of active region and flare plasmas to the λ195 channels of SOHO/EIT (Extreme-ultraviolet Imaging Telescope) and TRACE (Transition Region and Coronal Explorer).
Methods: .We have analysed an M8 flare simultaneously observed by the Coronal Diagnostic Spectrometer (CDS), EIT, TRACE and RHESSI. We obtained synthetic spectra for the flaring region and an outer region using the differential emission measures (DEM) of emitting plasma based on CDS and RHESSI observations and the CHIANTI atomic database. We then predicted the EIT and TRACE count rates.
Results: .For the flaring region, both EIT and TRACE images taken through the λ195 filter are dominated by Fe XXIV (formed at about 20 MK). However, in the outer region, the emission was primarily due to the Fe XII, with substantial contributions from other lines. The average count rate for the outer region was within 25% the observed value for EIT, while for TRACE it was a factor of two higher. For the flare region, the predicted count rate was a factor of two (in case of EIT) and a factor of three (in case of TRACE) higher than the actual count rate.
Conclusions: .During a solar flare, both TRACE and EIT λ195 channels are found to be dominated by Fe XXIV emission. Reasonable agreement between predictions and observations is found, however some discrepancies need to be further investigated. Title: The Gradual Phase of the X17 Flare on October 28, 2003 Authors: del Zanna, G.; Schmieder, B.; Mason, H.; Berlicki, A.; Bradshaw, S. Bibcode: 2006SoPh..239..173D Altcode: 2006SoPh..239..173Z; 2006SoPh..tmp...74Z We present SOHO/CDS observations taken during the gradual phase of the X17 flare that occurred on October 28, 2003. The CDS data are supplemented with TRACE and ground-based observations. The spectral observations allow us to determine velocities from the Doppler shifts measured in the flare loops and in the two ribbon kernels, one hour and a half after the flare peak. Strong downflows (>70 km s-1) are observed along the loop legs at transition-region temperatures. The velocities are close to those expected for free fall. Observations and results from a hydrodynamic simulation are consistent with the heating taking place for a short time near the top of the arcade. Slight upflows are observed in the outer edges of the ribbons (<60 km s-1) in the EUV lines formed at log T < 6.3. These flows could correspond to the so-called “gentle evaporation.” At “flare” temperatures (Fe xix, log T = 6.9), no appreciable flows are observed. The observations are consistent with the general standard reconnection models for two-ribbons flares. Title: The early phases of a solar prominence eruption and associated flare: a multi-wavelength analysis Authors: Chifor, C.; Mason, H. E.; Tripathi, D.; Isobe, H.; Asai, A. Bibcode: 2006A&A...458..965C Altcode: Aims.We aim to examine the precursor phases and early evolution of a prominence eruption associated with a M4-class flare and a partial halo coronal mass ejection (CME) observed on 2005 July 27. Our main goal is to investigate the precursor eruption signatures observed in EUV, X-ray and microwave emission and their relation to the prominence destabilisation.
Methods: .We perform a multi-wavelength study of the prominence morphology and motion using high-cadence and spatial resolution EUV 171 Å images from the TRACE satellite. The high-temperature flare radiative emission in soft and hard X-rays are analysed through imaging and spectral modeling with RHESSI. Complementary microwave images (17 GHz and 34 GHz) from NoRH are also investigated.
Results: .The activation of the filament proceeds from one anchored footpoint. We observe "pre-eruption" brightenings in X-ray and EUV images, close to the erupting footpoint of the prominence, being temporally correlated to the point when the prominence first enters a slow-rise phase, and then an accelerated fast-rise phase. The brightness temperature (T_b) of the prominence at 34 GHz is increasing during the eruption. We also find very good correlation between the prominence height-time profile and the spatially integrated soft X-ray (SXR) emission.
Conclusions: .We discuss the observed precursor brightenings with respect to possible mechanisms that might be responsible for the prominence destabilisation and acceleration. Our observations suggest that reconnection events localised beneath the erupting footpoint may eventually destabilise the entire prominence, causing the eruption. Title: Phosphorus distribution in calcite speleothems from solid-state NMR and AFM Authors: Mason, H. E.; Hausner, D.; Frisia, S.; Tang, Y.; Reeder, R. J.; Strongin, D. R.; Phillips, B. L. Bibcode: 2006GeCAS..70Q.399M Altcode: No abstract at ADS Title: Multi-Wavelength Investigation of a Sigmoidal Active Region Authors: Tripathi, D.; Mason, H. E.; Young, P. R. Bibcode: 2006ESASP.617E.148T Altcode: 2006soho...17E.148T No abstract at ADS Title: Asymmetric Prominence Eruption: A "Domino Effect"? Authors: Chifor, C.; Mason, H. E.; Tripathi, D.; Isobe, H.; Asai, A. Bibcode: 2006ESASP.617E.121C Altcode: 2006soho...17E.121C No abstract at ADS Title: On the propagation of brightening after filament/prominence eruptions, as seen by SoHO-EIT Authors: Tripathi, D.; Isobe, H.; Mason, H. E. Bibcode: 2006A&A...453.1111T Altcode: Aims.To study the relationship between the propagation of brightening and erupting filaments/prominences in order to get some insight into the three-dimensional picture of magnetic reconnection.
Methods: .Analysis of the observations taken with the EIT (Extreme-ultraviolet Imaging Telescope) aboard SoHO (Solar and Heliospheric Observatory).
Results: .When the prominences/filaments erupted having one point fixed - asymmetric eruption - the brightening propagated along the neutral line together with the expansion/separation from the polarity inversion line (PIL) as expected from the standard models. However in case of symmetric eruptions, the brightening propagated towards both end points starting at the middle. When the prominence/filament erupted faster then the speed of the propagating brightening was faster and vice-versa.
Conclusions: .Based on these observations we conclude that the eruption and magnetic reconnection - propagation (along the PIL) and separation (away from PIL) of the brightening - are dynamically coupled phenomena. These observations can be explained by a simple extension of the 2D models illustrating eruption and magnetic reconnection to a 3D model. Title: SOHO/CDS Observations of Quiescent Active Region Loops Authors: Del Zanna, G.; Mason, H. E.; Cirtain, J. Bibcode: 2006ESASP.617E..86D Altcode: 2006soho...17E..86D No abstract at ADS Title: The Coronal Loop Controversy: Resolved! Authors: Schmelz, Joan T.; Nasraoui, K.; Cirtain, J.; DeLuca, E.; Del Zanna, G.; Mason, H. Bibcode: 2006SPD....37.1701S Altcode: 2006BAAS...38..245S Critics have pointed out the shortcomings of CDS coronal loop temperature analysis - the large pixel size and the slow time cadence. It is these limitations, some say, that have produced multithermal results for the loop observed with CDS on 1998 April 20, both along the line of sight and along the loop length. Analysis of the CDS observations of AR 10250 from 2003 January 17, however, seem to contradict these critics. Two loops sit side-by-side right along the slit in this raster, so all pixels in each loop were observed at the same time. As a result changes as a function of time will not affect the temperature results. The first loop is observed primarily in Mg IX (Log T = 6.0) and the second in Si XII (Log T = 6.3). Differential Emission Measure (DEM) analysis of background subtracted line intensities of pixels in each loop show distinctly different results. For the first loop, the intensities of the lines that remain after background subtraction are well fit with a DEM that collapses to a single spike. In other words, the loop plasma at this location is isothermal. This proves that it is neither the DEM method nor the CDS pixel size that produced the multithermal distributions for the 1998 April 20 loop plasma. In addition the DEM distribution for the second loop is similar to those produced for the 1998 April 20 loop and is clearly inconsistent with isothermal plasma. Both distributions change as a function of position along the loop, with the temperatures increasing with loop height. Solar physics research at the University of Memphis is supported by grants from NSF and NASA. Title: Exploring High Time Resolution Coronal Dynamics with the Rapid Acquisition Imaging Spectrograph (RAISE) Sounding Rocket Program Authors: Hassler, Donald W.; DeForest, C. E.; McIntosh, S.; Slater, D.; Ayres, T.; Thomas, R.; Scheuhle, U.; Michaelis, H.; Mason, H. Bibcode: 2006SPD....37.3706H Altcode: The Rapid Acquisition Imaging Spectrograph (RAISE) is a next-generation high resolution imaging spectrograph to study the dynamics of the solar chromosphere and corona on time scales as short as 100 ms. High speed imaging from TRACE has shown that rapid motions and reconnection are central to the physics of the transition region and corona, but cannot resolve the differences between propagating phenomena and bulk motion. SoHO/CDS and SoHO/SUMER have yielded intriguing measurements of motion and heating in the solar atmosphere, and Solar-B/EIS will capture EUV spectra of flares in progress; but no currently planned instrument can capture spectral information in the chromosphere, transition region, or cool corona on the 1-10 Hz time scale required for few-second cadence spectral imaging or rapid wave motion studies. RAISE is uniquely suited to exploring this hard-to-reach domain.The first flight of RAISE is scheduled for October 24, 2006 (Flight 36.219 US) and will focus on the study of high frequency, small-scale dynamics of active region structures and the high frequency wave structure associated with these active regions. Title: A Multi-Wavelength Study of the Compact M1 Flare on October 22, 2002 Authors: Zanna, G. Del; Berlicki, A.; Schmieder, B.; Mason, H. E. Bibcode: 2006SoPh..234...95Z Altcode: In this paper we present a further study of the Ml class flare observed on October 22, 2002. We focus on the SOHO Coronal Diagnostic Spectrometer (CDS) spectral observations performed during a multi-wavelength campaign with TRACE and ground-based instruments (VTT, THEMIS). Strong blue-shifts are observed in the CDS coronal lines in flare kernels during the impulsive phase of this flare. From a careful wavelength calibration we deduce upflows of 140 km/s for the Fe XIX flare emission, with a pattern of progressively smaller flows at lower temperatures. Large line-widths were observed, especially for the Fe XIX line, which indicate the existence of turbulent velocities. The strong upflows correspond to full shifts of the line profiles. These flows are observed at the initial phase of the flare, and correspond to the "explosive evaporation". The regions of the blueshifted kernels, a few arc seconds away from the flare onset location, could be explained by the chain reaction of successive magnetic reconnections of growing emerging field line with higher and higher overlying field. This interpretation is evidenced by the analysis of the magnetic topology of the active region using a linear force-free-field extrapolation of THEMIS magnetograms. Title: A Multi-Wavelength Study of the Compact M1 Flare on October 22, 2002 Authors: del Zanna, G.; Berlicki, A.; Schmieder, B.; Mason, H. E. Bibcode: 2006SoPh..234...95D Altcode: 2006SoPh..234...95Z In this paper we present a further study of the Ml class flare observed on October 22, 2002. We focus on the SOHO Coronal Diagnostic Spectrometer (CDS) spectral observations performed during a multi-wavelength campaign with TRACE and ground-based instruments (VTT, THEMIS). Strong blue-shifts are observed in the CDS coronal lines in flare kernels during the impulsive phase of this flare. From a careful wavelength calibration we deduce upflows of 140 km/s for the Fe XIX flare emission, with a pattern of progressively smaller flows at lower temperatures. Large line-widths were observed, especially for the Fe XIX line, which indicate the existence of turbulent velocities. The strong upflows correspond to full shifts of the line profiles. These flows are observed at the initial phase of the flare, and correspond to the “explosive evaporation”. The regions of the blueshifted kernels, a few arc seconds away from the flare onset location, could be explained by the chain reaction of successive magnetic reconnections of growing emerging field line with higher and higher overlying field. This interpretation is evidenced by the analysis of the magnetic topology of the active region using a linear force-free-field extrapolation of THEMIS magnetograms. Title: X-ray emission from PTT stars Authors: Del Zanna, G.; Worters, H. L.; Bromage, G. E.; Foley, C. A.; Mason, H. E.; Landini, M.; Whiting, A. Bibcode: 2006AdSpR..38.1475D Altcode: We present preliminary results on an XMM-Newton observation dedicated to Post-T-Tauri (PTT) stars. We observed the visual binary 2RE J0241-53 of the Horologium association of nearby PTT stars. The XMM observations have been complemented with ground-based optical spectroscopy and photometry. Several flares have been observed. The X-ray spectrum of the brightest star during quiescence indicates a rather cool corona (with no emission at temperatures ⩾10 MK) more similar to that of the Classical T-Tauri star TW Hya (observed with Chandra and XMM-Newton) and at variance with that of another PTT Star (PZ Tel) observed with Chandra. Approximate analysis shows large Ne/Fe, N/Fe, C/Fe abundances (compared to solar photospheric values). Title: CHIANTI-An Atomic Database for Emission Lines. VII. New Data for X-Rays and Other Improvements Authors: Landi, E.; Del Zanna, G.; Young, P. R.; Dere, K. P.; Mason, H. E.; Landini, M. Bibcode: 2006ApJS..162..261L Altcode: The CHIANTI atomic database contains atomic energy levels, wavelengths, radiative transition probabilities, and collisional excitation data for a large number of ions of astrophysical interest. CHIANTI also includes a suite of IDL routines to calculate synthetic spectra and carry out plasma diagnostics. Version 5 has been released, which includes several new features, as well as new data for many ions. The new features in CHIANTI are as follows: the inclusion of ionization and recombination rates to individual excited levels as a means to populate atomic levels; data for Kα and Kβ emission from Fe II to Fe XXIV; new data for high-energy configurations in Fe XVII to Fe XXIII; and a complete reassessment of level energies and line identifications in the X-ray range, multitemperature particle distributions, and photoexcitation from any user-defined radiation field. New data for ions already in the database, as well as data for ions not present in earlier versions of the database, are also included. Version 5 of CHIANTI represents a major improvement in the calculation of line emissivities and synthetic spectra in the X-ray range and expands and improves theoretical spectra calculations in all other wavelength ranges. Title: Dynamics of Active Region Loops: Temperature Measurements as a function of Time Authors: Cirtain, J. J.; del Zanna, G.; Mason, H.; Deluca, E.; Martens, P. Bibcode: 2005AGUFMSH44A..03C Altcode: The combination of moderate resolution EUV spectroscopy and high resolution narrow band filter images provides the most accurate measure of temperature and density for coronal loops to date. We will demonstrate our technique for combining the data sets from the Coronal Diagnostic Spectrometer on SoHO and the Transition Region and Coronal Explorer. Background subtracted spectral intensities are used to determine the temperature of coronal loops and the TRACE images help determine the loop cross-section, temporal variability, and filling factor. The resulting temperature profiles for multiple positions along a loop leg are determined using the EM LOCI method, and a technique for determining whether a single temperature can characterize the plasma is also presented. We compare the results of our study to current models. Title: Flows and Heating of the Solar Atmosphere during Solar Flares Authors: Schmieder, B.; Berlicki, A.; Li, H.; Del Zanna, G.; Mason, H. Bibcode: 2005ESASP.592..543S Altcode: 2005soho...16E.102S; 2005ESASP.592E.102S No abstract at ADS Title: Recent developments of the CHIANTI database in the X-ray wavelength range Authors: Landi, E.; Dere, K. P.; Young, P. R.; del Zanna, G.; Mason, H. E.; Landini, M. Bibcode: 2005AIPC..774..409L Altcode: CHIANTI is a database of atomic data and transition probabilities that allows the calculation of synthetic spectra and plasma diagnostics of optically thin plasmas. It is primarily suited for wavelengths shorter than 2000 Å but in principle can also be used at longer wavelengths. In the present paper we illustrate the latest development of the CHIANTI database, that include a huge expansion of the database in the X-ray wavelength range, the renewal of several data in the EUV range, and the inclusion of ionization and recombination in the level population calculation. This enhanced database will constitute the Version 5 of CHIANTI. Title: EUV Observations of Active Region Dynamics Authors: Deluca, E. E.; Cirtain, J. W.; del Zanna, G.; Mason, H. E.; Martens, P. C.; Schmelz, J.; Golub, L. Bibcode: 2005AGUSMSP33A..03D Altcode: Data collected during SoHO JOP 146, in collaboration with TRACE, is used to investigate the physical characteristics of coronal active region loops as a function of time and position along and across loop structures. These data include TRACE images in all three EUV passbands, and simultaneous CDS spectroscopic observations. Preliminary measurements of the loop temperature both along the loop half-length and loop cross-section are presented as a function of time. We will show the temperature and density profiles of several structures as a function of position, show changes in temperature and density with time and characterize the coronal background emission. Questions raised by these results will be greatly advanced with the high resolution spectra available from the EIS on Solar-B. Title: Benchmarking atomic data for astrophysics: Fe XII Authors: Del Zanna, G.; Mason, H. E. Bibcode: 2005A&A...433..731D Altcode: We use recently calculated electron collisional data by [CITE] for ion{Fe}{xii} (n=3 configurations) to build a model ion to compare to spectroscopic observations of the solar corona and laboratory measurements. We review all the line identifications of the brightest lines, by comparing both wavelengths and line intensities. The presence of blends in different plasma conditions is highlighted. A large number of new energy levels and line identifications are proposed. In particular, we identify the electric quadrupole ^4P{5/2}^e-^4F{9/2}e transition with the bright coronal line observed at 592.6 Å, previously unidentified. This line, when observed with the 1242.0, 1349.5 UV forbidden lines, is a good density diagnostic over a large range of electron densities. We also indicate the best spectral lines to be used for density diagnostics or instrument calibration. From various combinations of lines we obtain electron densities that are significantly different from those published in the previous literature. Some examples are provided. The agreement between theory and experimental data in terms of wavelengths, line intensities and level lifetimes is excellent.

The full datasets of energies (Table 2) and radiative data (Table 3) are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/433/731 Title: Atomic data from the IRON Project Authors: Storey, P. J.; Del Zanna, G.; Mason, H. E.; Zeippen, C. J. Bibcode: 2005A&A...433..717S Altcode: A new calculation of rate coefficients for electron collisional excitation of ion{Fe}{xii} is presented and compared to earlier calculations. Significant differences are found with all earlier work due to the inclusion of resonance processes that have not previously been considered and to the use of the intermediate coupling frame transformation method. The resulting dataset of collision strengths is shown to resolve many of the outstanding discrepancies between theory and solar observations. In particular, density sensitive line ratios in ion{Fe}{xii} now indicate electron densities close to those derived from other ions of comparable ionization potential.

Table 10 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/433/717 Title: Multialtitude Observations of a Coronal Jet during the Third Whole Sun Month Campaign Authors: Ko, Y. -K.; Raymond, J. C.; Gibson, S. E.; Alexander, D.; Strachan, L.; Holzer, T.; Gilbert, H.; Cyr, O. C. St.; Thompson, B. J.; Pike, C. D.; Mason, H. E.; Burkepile, J.; Thompson, W.; Fletcher, L. Bibcode: 2005ApJ...623..519K Altcode: On 1999 August 26, a coronal jet occurred at the northwest limb near a sigmoid active region (AR 8668) that was the target for a joint observation plan (SOHO joint observing program 106) during the third Whole Sun Month Campaign. This jet was observed by several instruments at the limb (SOHO/CDS, SOHO/EIT, TRACE, and Mauna Loa Solar Observatory CHIP and PICS) and at 1.64 Rsolar (SOHO/UVCS). At the limb, this jet event displayed both low- and high-temperature components. Both high- and low-temperature components were evident during the early phase (first 20 minutes) of the event. However, the low-temperature component is maintained for ~1 hr after the higher temperature component is gone. There is a second brightening (a possible second jet) seen by EIT and TRACE about 50 minutes after the onset of the first jet. The line-of-sight motion at the limb began with a 300 km s-1 redshift and evolved to a 200 km s-1 blueshift. At 1.64 Rsolar, the intensities of Lyα and Lyβ in the jet increased by a factor of several hundred compared with the background corona. The C III λ977 line also brightened significantly. This indicates low-temperature [~(1-2)×105 K] emission in the jet, while the intensities of O VI λ1032 and O VI λ1037 increased by as much as a factor of 8. The UVCS data show evidence of heating at the early phase of the event. The Doppler shift in the lines indicates that the line-of-sight (LOS) velocity in the jet started from ~150 km s-1 in blueshift and ended at ~100 km s-1 in redshift. This LOS motion seen at 1.64 Rsolar was apparently opposite to what was observed when the jet emerged from the limb. The Doppler dimming analysis indicates that the radial outflow speed correlates with the magnitude of the LOS speed. Interestingly, UVCS observations at 2.33 and 2.66 Rsolar show no trace of the jet and SOHO/LASCO observations also yield no firm detection. We find that a simple ballistic model can explain most of the dynamical properties of this jet, while the morphology and the thermal properties agree well with reconnection-driven X-ray jet models. Title: Benchmarking atomic data for astrophysics: Fe XXIII Authors: Del Zanna, G.; Chidichimo, M. C.; Mason, H. E. Bibcode: 2005A&A...432.1137D Altcode: Recent scattering calculations for Fe XXIII are benchmarked against laboratory and astrophysical observations. The collisional data are supplemented by radiative data obtained with empirical adjustments that take into account observed wavelengths. All previous line identifications and energy levels are reviewed and assessed in light of these new calculations. Most of the previous identifications, in particular of the astrophysically-important spectral lines are confirmed. However, some identification are rejected or questioned, and new ones proposed. The agreement between theoretical and experimental data in terms of wavelengths, line intensities and level lifetimes is very good. Observations of Fe XXIII L-shell emission lines provide a great opportunity to directly measure electron temperatures for a wide range of astrophysical sources. Examples from solar (SMM, SOLEX) and stellar (Chandra, EUVE) observations are provided.

The full set of energies (cf. Table 2), wavelengths and A-values (cf. Table 3) are available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/432/1137 . Title: VizieR Online Data Catalog: Fe XXIII Benchmarking (Del Zanna+, 2005) Authors: Del Zanna, G.; Chidichimo, M. C.; Mason, H. E. Bibcode: 2005yCat..34321137D Altcode: Recent scattering calculations for Fe XXIII are benchmarked against laboratory and astrophysical observations. The collisional data are supplemented by radiative data obtained with empirical adjustments that take into account observed wavelengths. All previous line identifications and energy levels are reviewed and assessed in light of these new calculations. Most of the previous identifications, in particular of the astrophysically-important spectral lines are confirmed. However, some identification are rejected or questioned, and new ones proposed. The agreement between theoretical and experimental data in terms of wavelengths, line intensities and level lifetimes is very good. Observations of Fe XXIII L-shell emission lines provide a great opportunity to directly measure electron temperatures for a wide range of astrophysical sources. Examples from solar (SMM, SOLEX) and stellar (Chandra, EUVE) observations are provided.

************************************************************************** * * * Sorry, but the author(s) never supplied the tabular material * * announced in the paper * * * **************************************************************************

(1 data file). Title: VizieR Online Data Catalog: Atomic data from the IRON Project. LVI. (Chidichimo+, 2005) Authors: Chidichimo, M. C.; Del Zanna, G.; Mason, H. E.; Badnell, N. R.; Tully, J. A.; Berrington, K. A. Bibcode: 2005yCat..34300331C Altcode: Collision strengths for electron induced transitions in the beryllium-like ion Fe+22 are calculated using the intermediate coupling frame transformation (ICFT) version of the R-matrix programs. Our target has 98 fine structure states ls2 nl n'l'SLJ corresponding to n=2 and n'=2, 3, 4. The present calculation is for electron impact energies in the range 3.15 to 380Ry.

************************************************************************** * * * Sorry, but the author(s) never supplied the tabular material * * announced in the paper * * * **************************************************************************

(1 data file). Title: VizieR Online Data Catalog: Fe X Benchmarking atomic data (Del Zanna+, 2004) Authors: Del Zanna, G.; Berrington, K. A.; Mason, H. E. Bibcode: 2005yCat..34220731D Altcode: This is the first in a series of papers in which we benchmark recent atomic data available for astrophysical applications. We review various issues related to the completeness and accuracy of both theoretical and experimental data. In this paper, the available experimental and atomic data for Fe X (n=3 configurations) are reviewed and assessed. New collisional and radiative data are calculated to supplement published data. The radiative calculations are done with empirical adjustements that take into account observed wavelengths. Previous line identifications are also reviewed and assessed. Our approach focuses on the brightest spectral lines, and uses both wavelengths and line intensities to assess the line identifications on a quantitative basis. Although many previous line identifications are confirmed, some are rejected (e.g. the coronal line observed at 1582.35{AA}). We confirm previously suggested identifications (e.g. 257.262{AA},1028.02{AA}), and we present new ones, (e.g. the lines of the 3s2 3p4 3d-3s 3p5 3d transition array). In addition, we highlight the presence of blends and we review which spectral lines are best for density diagnostics or for instrument calibration. The theoretical data (line intensities and level lifetimes) are benchmarked against well-calibrated spectroscopic observations of the solar corona and laboratory measurements. The agreement between theoretical and experimental data which we achieve with our new model ion is very good.

(3 data files). Title: The CHIANTI database Authors: Landi, E.; Dere, K. P.; Young, P. R.; Landini, M.; Mason, H. E.; Del Zanna, G. Bibcode: 2005HiA....13..653L Altcode: CHIANTI is a database of atomic data and transition rates necessary for calculating synthetic spectra and carrying out plasma diagnostics of astrophysical sources in the X-ray EUV and UV wavelength ranges. CHIANTI includes both line and continuum emission from all astrophysically abundant elements in the universe. All data are taken from refereed literature and are critically assessed. CHIANTI also includes a suite of IDL programs that allow spectroscopic analysis to be carried out. CHIANTI data and software are freely distributed over the internet.

In the present talk I will describe the contents of the CHIANTI database its current status and the areas where CHIANTI is being developed and I will also present a comparison of CHIANTI predictions with the X-ray emission from astrophysical sources. Title: Atomic data from the IRON Project = 2, 3, 4 configurations. LVI. Electron excitation of Be-like Fe XXIII for the n = 2,3,4 configurations Authors: Chidichimo, M. C.; Del Zanna, G.; Mason, H. E.; Badnell, N. R.; Tully, J. A.; Berrington, K. A. Bibcode: 2005A&A...430..331C Altcode: Collision strengths for electron induced transitions in the beryllium-like ion Fe+22 are calculated using the intermediate coupling frame transformation (ICFT) version of the R-matrix programs. Our target has 98 fine structure states 1s2 nl n'l' SLJ corresponding to n = 2 and n' = 2, 3, 4 . The present calculation is for electron impact energies in the range 3.15 to 380 Ry. When T exceeds about ten million degrees one needs to take account of contributions to the thermally averaged collision strength Υ coming from electrons with energies in excess of 380 Ry. We discuss a way of allowing for these contributions. Values of Υ for all the transitions between the ground state and the excited states 1s2 2l n l n'l' S'L'J', with n'=2,3,4 are tabulated as a function of log T. The temperature range 6.3 ≤log T ≤8.1 is centred on log T = 7.1 which is approximately where Fe+22 has maximum abundance in ionization equilibrium. To the best of our knowledge these are the first R-matrix calculations for Fe+22 for excitations to the n = 3,4 levels. Good agreement with previous distored-wave calculations is found. However, the resonance contributions have an important effect on the effective collision strengths and in turn on the level populations.

Full Tables 2, 4 and 6 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/430/331. The full datasets of wavelengths and gf values (Table 4) and of effective collision strengths (Table 7) are only available at the same address. The same data are also available at the TIPbase (http://vizier.u-strasbg.fr/tipbase/home.html) database and as an `adf04' file at the Oak Ridge National Laboratory's database via http://www-cfadc.phy.ornl.gov/ Title: Spectral diagnostic capabilities of Solar-B EIS Authors: Zanna, G. Del; Mason, H. E. Bibcode: 2005AdSpR..36.1503Z Altcode: In this paper, we provide simulated intensities for Solar-B EIS to aid in the scientific planning for Solar-B. These simulations are obtained with the latest atomic data and EIS response functions. We also report on our progress in reviewing and benchmarking atomic data for the Fe coronal ions, that are of particular importance for spectral and instrument calibration purposes. We highlight the most prominent lines that can be used for plasma diagnostics. Title: VizieR Online Data Catalog: Fe XII Benchmarking atomic data (Del Zanna+, 2005) Authors: Del Zanna, G.; Mason, H. E. Bibcode: 2005yCat..34330731D Altcode: We use recently calculated electron collisional data by Storey et al. (2005A&A...433..717S) for Fe XII (n=3 configurations) to build a model ion to compare to spectroscopic observations of the solar corona and laboratory measurements. We review all the line identifications of the brightest lines, by comparing both wavelengths and line intensities. The presence of blends in different plasma conditions is highlighted. A large number of new energy levels and line identifications are proposed. In particular, we identify the electric quadrupole 4P5/2-4^F9/2 transition with the bright coronal line observed at 592.6{AA}, previously unidentified. This line, when observed with the 1242.0, 1349.5 UV forbidden lines, is a good density diagnostic over a large range of electron densities. We also indicate the best spectral lines to be used for density diagnostics or instrument calibration. From various combinations of lines we obtain electron densities that are significantly different from those published in the previous literature. Some examples are provided. The agreement between theory and experimental data in terms of wavelengths, line intensities and level lifetimes is excellent.

(2 data files). Title: Remote Sensing of Plasma Diagnostics Relating to Coronal Heating Authors: Mason, H. E.; Del Zanna, G.; Bradshaw, S. Bibcode: 2004ESASP.575..312M Altcode: 2004soho...15..312M No abstract at ADS Title: Synthesised Radiative Emission from a Nanoflare Heated Elemental Solar Loop Authors: Bradshaw, S. J.; Del Zanna, G.; Mason, H. E.; Cargill, P. J. Bibcode: 2004ESASP.575..539B Altcode: 2004soho...15..539B No abstract at ADS Title: On the consequences of a non-equilibrium ionisation balance for compact flare emission and dynamics Authors: Bradshaw, S. J.; Del Zanna, G.; Mason, H. E. Bibcode: 2004A&A...425..287B Altcode: We carry out a hydrodynamic simulation of a compact flare and find significant non-equilibrium distributions for the ionisation balance during the impulsive and gradual phases, which can strongly alter the radiative emission. This has major implications for attempts to derive the theoretical intensities of emission lines used for spectroscopic diagnostic analyses of the plasma properties.

During the impulsive phase we find that the emissivities of He I, He II and C IV in the transition region can be strongly enhanced above their expected equilibrium values, followed by a significant reduction which increases the amount of chromospheric plasma ablated into the corona. Furthermore, during the flare heating the overall charge state of the coronal ions can be significantly lower than is suggested by an equilibrium ionisation balance and, therefore, line ratio measurements will yield plasma temperatures that are much greater than the formation temperature of the emitting ion.

During the gradual phase the emissivity at transition region temperatures remains suppressed, compared with its equilibrium value, with correspondingly reduced downflow velocities and increased radiative cooling time-scales.

Finally, we synthesise the emission as it would be detected by TRACE in its 171 Å and 195 Å wavelength bands, and find that the filter ratio technique can give reasonably good estimates of the plasma temperature in quiescence, though when the populations of Fe VIII, Fe IX, Fe X and Fe XII exhibit departures from equilibrium the temperatures derived from filter ratio measurements become unreliable.

Figures \ref{fig4}-\ref{fig39} are only available in electronic form at http://www.edpsciences.org Title: Benchmarking atomic data for astrophysics: Fe X Authors: Del Zanna, G.; Berrington, K. A.; Mason, H. E. Bibcode: 2004A&A...422..731D Altcode: This is the first in a series of papers in which we benchmark recent atomic data available for astrophysical applications. We review various issues related to the completeness and accuracy of both theoretical and experimental data. In this paper, the available experimental and atomic data for Fe X (n=3 configurations) are reviewed and assessed. New collisional and radiative data are calculated to supplement published data. The radiative calculations are done with empirical adjustements that take into account observed wavelengths. Previous line identifications are also reviewed and assessed. Our approach focuses on the brightest spectral lines, and uses both wavelengths and line intensities to assess the line identifications on a quantitative basis. Although many previous line identifications are confirmed, some are rejected (e.g. the coronal line observed at 1582.35 Å). We confirm previously suggested identifications (e.g. 257.262 Å, 1028.02 Å), and we present new ones, (e.g. the lines of the 3s23p43d-3s 3p53d transition array). In addition, we highlight the presence of blends and we review which spectral lines are best for density diagnostics or for instrument calibration. The theoretical data (line intensities and level lifetimes) are benchmarked against well-calibrated spectroscopic observations of the solar corona and laboratory measurements. The agreement between theoretical and experimental data which we achieve with our new model ion is very good.

Table 1 and full Tables 3 and \ref{tab:lines} are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/422/731

Appendix is only available in electronic form at http://www.edpsciences.org Title: High Time Cadence Observations with the Rapid Acquisition Imaging Spectrograph (RAISE) Rocket Program Authors: Ayres, T. R.; Hassler, D. M.; Slater, D.; DeForest, C. E.; Mason, H.; McIntosh, S.; Thomas, R. J. Bibcode: 2004AAS...204.9704A Altcode: 2004BAAS...36..828A The Rapid Acquisition Imaging Spectrograph (RAISE) is a next-generation high resolution imaging spectrograph scheduled to fly on a NASA sounding rocket in 2006 to study the dynamics of the solar chromosphere and corona on time scales as short as 100 ms. High speed imaging from TRACE has shown that rapid motions and reconnection are central to the physics of the transition region and corona, but cannot resolve the differences between propagating phenomena and bulk motion. SoHO/CDS and SoHO/SUMER have yielded intriguing measurements of motion and heating in the solar atmosphere, and Solar-B/EIS will capture EUV spectra of flares in progress; but no currently planned instrument can capture spectral information in the chromosphere, transition region, or cool corona on the ∼ 1-10 Hz time scale required for few-second cadence spectral imaging or rapid wave motion studies. RAISE is uniquely suited to exploring this hard-to-reach domain.

This work is supported by NASA Grant NNG04WC01G to the Southwest Research Institute. Title: Recent development of the CHIANTI database in the X-ray wavelength range Authors: Landi, E.; Dere, K. P.; Mason, H. E.; Del Zanna, G.; Landini, M.; Young, P. R. Bibcode: 2004AAS...204.7310L Altcode: 2004BAAS...36R.801L CHIANTI consists of a database of critically assessed atomic data and transition rates to calculate line and continuum emission from astrophysical plasmas.

During the last year the CHIANTI database has been substantially expanded in the X-ray wavelength region by including a large number of new configurations and lines, and by including ionization and recombination processes in the level population calculations.

We will describe these improvements, the data we used, and illustrate examples of 1) their effects on predicted emissivities and on plasma diagnostics 2) applications to the study of flares in solar active regions Title: Spectral diagnostic capabilities of Solar-B EIS Authors: del Zanna, G.; Mason, H. E. Bibcode: 2004cosp...35.3002D Altcode: 2004cosp.meet.3002D We briefly review the main spectral diagnostics that will be available with Solar-B EIS, and what kind of scientific questions could be best addressed, based on our experience with SOHO/CDS observations. We then report on our progress in reviewing and benchmarking atomic data for the Fe coronal ions, that are of particular importance for spectral and instrument calibration purposes. Title: Future Observations with the Rapid Acquisition Imaging Spectrograph (RAISE) Authors: Hassler, D. M.; Deforest, C. E.; Slater, D.; Ayres, T.; Mason, H.; McIntosh, S.; Thomas, R. Bibcode: 2004cosp...35.2280H Altcode: 2004cosp.meet.2280H The Rapid Acquisition Imaging Spectrograph (RAISE) is a next-generation high resolution imaging spectrograph scheduled to fly on a NASA sounding rocket in 2006 to study the dynamics of the solar chromosphere and corona on time scales as short as 100 ms. High speed imaging from TRACE has shown that rapid motions and reconnection are central to the physics of the transition region and corona, but cannot resolve the differences between propagating phenomena and bulk motion. SoHO/CDS and SoHO/SUMER have yielded intriguing measurements of motion and heating in the solar atmosphere, and Solar-B/EIS will capture EUV spectra of flares in progress; but no currently planned instrument can capture spectral information in the chromosphere, transition region, or cool corona on the ~1-10 Hz time scale required for few-second cadence spectral imaging or rapid wave motion studies. RAISE is uniquely suited to exploring this hard-to-reach domain. Title: X-ray emission from PTT stars Authors: del Zanna, G.; Bromage, G.; Foley, C.; Worters, H.; Mason, H.; Landini, M. Bibcode: 2004cosp...35.2995D Altcode: 2004cosp.meet.2995D We present preliminary results on new X-ray spectroscopic XMM/RGS observations of the visual binary nicknamed `Horace Horologii' (2RE J0241-53). The two stars are strong and very active X-ray emitters, and are members of an association of Post-T-Tauri stars. A detailed study (in particular in terms of chemical composition) is important for our understanding of the evolution from the T-Tauri phase, and to explain the origin of the X-ray emission in very young stars. The physical characteristics of the quiescent X-ray emission are described, and related to other stellar parameters such as photospheric abundances and the rotational period. Simultaneous ground-based optical spectroscopy and U-band photometric monitoring observations were obtained at the South African Astronomical Observatory. Title: Spectroscopic observations of compact solar flares Authors: del Zanna, G.; Mason, H. E. Bibcode: 2004cosp...35.2998D Altcode: 2004cosp.meet.2998D We present SOHO/Coronal Diagnostic Spectrometer observations of solar flares, complemented with data from other instruments (such as high-resolution images from TRACE, magnetograms from SOHO/MDI, and Yohkoh SXT). We show that CDS provides essential spectroscopic information which adds complexity into our understanding of the dynamics of solar flares. We give a description of the main observational features, and what types of measurements (densities, temperatures, flows) are obtained. These observations provide constraints for flare modeling, and indications on what types of spectroscopic observations future instruments should provide. Title: CHIANTI -- An Atomic Database for UV and X-ray Cool star spectroscopy Authors: Young, P. R.; Landi, E.; Bromage, G. E.; del Zanna, G.; Dere, K. P.; Landini, M.; Mason, H. E. Bibcode: 2003csss...12.1119Y Altcode: The CHIANTI atomic database was first released in 1996 and has since become the standard resource for the interpretation of UV spectra from the transition regions and coronae of the Sun and other cool stars. We describe the contents of the most recent release (v.3) and some of the uses that have been found for the database. Title: The radiative response of solar loop plasma subject to transient heating Authors: Bradshaw, S. J.; Mason, H. E. Bibcode: 2003A&A...407.1127B Altcode: In Bradshaw & Mason (\cite{Bradshaw2003}) we carried out a hydrodynamic simulation of a cooling solar loop and investigated the nonequilibrium response of the population of C VII ions to the changing conditions in the plasma. We also compared equilibrium and nonequilibrium calculations of the total plasma emissivity. In this paper we present two simulations of a solar loop subject to a transient heating process delivering energy on the nanoflare scale at its apex. One simulation treats the ion populations and the energy radiated from the loop plasma entirely as though the system were in equilibrium and the other simulation performs a full nonequilibrium treatment by coupling the time-dependent ion populations to the hydrodynamic equations through the radiative energy loss. Our radiative model accounts for the 15 most abundant elements of the solar atmosphere including C, O, Ne, Mg, Si and Fe.

We find some pronounced differences between the populations of certain transition region ions and the corresponding plasma emissivity curves in the equilibrium and nonequilibrium simulations. Though the apex heating event is relatively weak in comparison to energy released on the microflare and flare scales, nonetheless a significant amount of energy reaches the loop footpoint region to heat the plasma there and we find a nonequilibrium spike in emissivity. However, more surprisingly we find considerable differences between some of the coronal ions in the equilibrium and nonequilibrium simulations, with important consequences for the plasma emissivity curves. In particular, we find that the total plasma emissivity calculated assuming equilibrium conditions is up to a factor of 5 lower than the nonequilibrium emissivity and this is due almost entirely to the response of the coronal Fe ions.

Finally, we suggest possible observational signatures of nonequilibrium ionisation and ways in which one might identify it. This is important because an invalid assumption of equilibrium ion populations may well lead one to incorrect conclusions about the properties of the plasma in both a broad-band and narrow-band/emission line based analysis.

Figures 11 to 13 and Appendix A are only available in electronic form at http://www.edpsciences.org Title: Solar active regions: SOHO/CDS and TRACE observations of quiescent coronal loops Authors: Del Zanna, G.; Mason, H. E. Bibcode: 2003A&A...406.1089D Altcode: This study focuses on the diagnostic capabilities of the TRACE and SOHO-CDS instruments to describe the physical characteristics of quiescent solar active regions. In particular we concentrate on the 1 MK loops, best seen in the TRACE EUV 173 Å passband. These are high-lying structures which can remain stable over timescales of hours to days. We present simultaneous observations of off-limb active region 1 MK loops performed with TRACE (173 Å and 195 Å bands) and the SOHO-CDS. The CDS spectral capabilities complement the TRACE observations well and allow an in-depth study of the plasma properties. Some important new results are presented here. In terms of cross-field characteristics, we find that these loops are isothermal and much cooler (T =~ 0.7-1.1 x 106 K) than the surrounding diffuse high-lying active region emission (T =~ 2 x 106 K). We show that the diffuse background-foreground constitutes the bulk of the high-lying quiescent active region emission. We explain some of the discrepancies found by various authors (based on SOHO and TRACE observations) with an overestimation of loop temperatures and densities. This was caused by inaccurate or neglected background subtraction in the data analysis. We studied the leg of a 1 MK loop and found that along its length temperatures and densities have steeper profiles compared to those derived from previous studies based on TRACE observations. The observations are consistent with an element abundance FIP effect of about 4, filling factors close to unity, and a constant density across the loop. We find a remarkable consistency between the CDS and TRACE observations, although we also find severe limitations to the use of TRACE diagnostic techniques. Title: A self-consistent treatment of radiation in coronal loop modelling Authors: Bradshaw, S. J.; Mason, H. E. Bibcode: 2003A&A...401..699B Altcode: We perform a hydrodynamic simulation of a cooling coronal loop and calculate the time-dependent ion populations of the most abundant elements of the solar atmosphere at each time-step. We couple the time-dependent ion balance equations to the hydrodynamic equations in order to treat the energy loss through radiation in a self-consistent way by allowing for the emission from a potentially nonequilibrium ion population.

We present results for the response to the changing conditions in the loop of the population of C VII ions and find significant deviations from equilibrium in the coronal and footpoint regions of the loop. The former is due to the tenuous nature of the coronal plasma causing recombinations to be rare and the latter is due to the strong downflows that develop as the loop cools, which carry persistent C VII ions into the lower regions of the loop. We also present a comparison between total plasma emissivity curves calculated during this simulation and an almost identical simulation that assumed an equilibrium ion population for the calculation of the radiation term. As a result of the nonequilibrium ion populations we find significant differences between the emissivity curves of each simulation and the loop cooling times.

We suggest that a consideration of nonequilibrium ionisation and radiation might help to (a) explain the thermal broadening observed in some emission lines during explosive events, and (b) reconcile differences between theory and observations relating to the longevity of some loops observed in the TRACE filters. Title: Spectroscopic characteristics of polar plumes Authors: Del Zanna, G.; Bromage, B. J. I.; Mason, H. E. Bibcode: 2003A&A...398..743D Altcode: Extreme ultraviolet observations of plumes in polar coronal holes are presented and their spectroscopic signatures discussed. The study focuses on the base of plumes seen on the disk of the Sun with the Coronal Diagnostic Spectrometer (CDS) on the Solar and Heliospheric Observatory (SOHO) satellite. Spectroscopic diagnostic techniques are applied to characterise the plumes in terms of density, temperature, emission measure and element abundance. Attention is drawn to the particular limitations of some of the techniques when applied to plume structures. In particular, we revisit the Widing & Feldman (1992) findings of a plume having a large first ionization potential (FIP) effect of 10, showing that instead the Skylab data are consistent with no FIP effect. We present for the first time CDS-GIS (grazing incidence spectrometer) observations of a plume. These observations have been used to confirm the results obtained from normal incidence (NIS) observations. We find that polar plumes exhibit the same characteristics as the Elephant's Trunk equatorial plume. The most striking characteristic of the plume bases is that they are near-isothermal with a peak emission measure at transition region temperatures =~ 8 x 105 K. At these temperatures, plumes have averaged densities Nlo {e} =~ 1.2 x 109 cm-3, about twice the value of the surrounding coronal hole region. Element abundances in the plumes are found to be close to photospheric, with the exception of neon which appears to be depleted by 0.2 dex relative to oxygen. The absence of a significant FIP effect in plumes is consistent with fast solar wind plasma, although it is not sufficient to prove a link between the two. Finally, we present a comparison between GIS spectra and the SOHO EIT (EUV Imaging Telescope) broad-band images, showing that temperatures derived from the EIT ratio technique are largely overestimated, for plumes and coronal holes. This is partly due to the fact that the so called ``Fe XII 195 Å'' and ``Fe XV 284 Å'' filters are not isothermal, and in coronal holes and plumes lower-temperature lines dominate the EIT signal. Title: CHIANTI-An Atomic Database for Emission Lines. VI. Proton Rates and Other Improvements Authors: Young, P. R.; Del Zanna, G.; Landi, E.; Dere, K. P.; Mason, H. E.; Landini, M. Bibcode: 2003ApJS..144..135Y Altcode: 2002astro.ph..9493Y The CHIANTI atomic database contains atomic energy levels, wavelengths, radiative transition probabilities, and electron excitation data for a large number of ions of astrophysical interest. Version 4 has been released, and proton excitation data are now included, principally for ground configuration levels that are close in energy. The fitting procedure for excitation data, both electrons and protons, has been extended to allow nine-point spline fits in addition to the previous five-point spline fits. This allows higher quality fits to data from close-coupling calculations where resonances can lead to significant structure in the Maxwellian-averaged collision strengths. The effects of photoexcitation and stimulated emission by a blackbody radiation field in a spherical geometry on the level balance equations of the CHIANTI ions can now be studied following modifications to the CHIANTI software. With the addition of H I, He I, and N I, the first neutral species have been added to CHIANTI. Many updates to existing ion data sets are described, while several new ions have been added to the database, including Ar IV, Fe VI, and Ni XXI. The two-photon continuum is now included in the spectral synthesis routines, and a new code for calculating the relativistic free-free continuum has been added. The treatment of the free-bound continuum has also been updated. Title: CHIANTI - An Atomic Database for XUV Emission Lines Authors: Landi, Enrico; Dere, Ken P.; Landini, Massimo; Young, Peter R.; Mason, Helen E.; del Zanna, Giulio Bibcode: 2003IAUJD..17E..10L Altcode: CHIANTI is a database of atomic data and transition rates necessary for calculating synthetic spectra and carrying out plasma diagnostics of astrophysical sources in the X-ray EUV and UV wavelength ranges. CHIANTI includes both line and continuum emission from all astrophysically abundant elements in the universe. All data are taken from refereed literature and are critically assessed. CHIANTI also includes a suite of IDL programs that allow spectroscopic analysis to be carried out. CHIANTI data and software are freely distributed over the internet.

In the present talk I will describe the contents of the CHIANTI database its current status and the areas where CHIANTI is being developed and I will also present a comparison of CHIANTI predictions with the X-ray emission from astrophysical sources. Title: Active Region Studies with SOHO-CDS Authors: Mason, H. E.; Del Zanna, G. Bibcode: 2002ASPC..277...37M Altcode: 2002sccx.conf...37M No abstract at ADS Title: EUV spectral observations of active region flares Authors: Del Zanna, G.; Mason, H. E.; Foley, C. Bibcode: 2002ESASP.506..585D Altcode: 2002svco.conf..585D; 2002ESPM...10..585D We present EUV spectral observations of C-M class flares performed with the Coronal Diagnostic Spectrometer (CDS) onboard SOHO during the Cambridge active region (AR) campaigns in 1999 and 2001. With the CDS spectral data, complemented by other space observations (mainly TRACE, YOHKOH SXT), we investigate the physical properties of ARs, and study the development of small-scale flares. We discuss the importance of spectral observations in relation to the correct interpretation of broad band images. In particular, we present co-spatial simultaneous YOHKOH SXT and CDS flare observations and discuss the validity of the temperatures derived from the SXT filter ratios. In addition, we present sample results that can only be obtained with spectral data, such as measurements of densities, elemental abundances and post-flare flows, associated with slow chromospheric evaporation. All these results are important observational constraints for flare modeling. Title: Solar and stellar high-resolution X-ray spectra: plasma diagnostics with the CHIANTI atomic database Authors: Del Zanna, G.; Mason, H. E. Bibcode: 2002ASPC..277..333D Altcode: 2002sccx.conf..333D No abstract at ADS Title: The Structure and Evolution of a Sigmoidal Active Region Authors: Gibson, S. E.; Fletcher, L.; Del Zanna, G.; Pike, C. D.; Mason, H. E.; Mandrini, C. H.; Démoulin, P.; Gilbert, H.; Burkepile, J.; Holzer, T.; Alexander, D.; Liu, Y.; Nitta, N.; Qiu, J.; Schmieder, B.; Thompson, B. J. Bibcode: 2002ApJ...574.1021G Altcode: Solar coronal sigmoidal active regions have been shown to be precursors to some coronal mass ejections. Sigmoids, or S-shaped structures, may be indicators of twisted or helical magnetic structures, having an increased likelihood of eruption. We present here an analysis of a sigmoidal region's three-dimensional structure and how it evolves in relation to its eruptive dynamics. We use data taken during a recent study of a sigmoidal active region passing across the solar disk (an element of the third Whole Sun Month campaign). While S-shaped structures are generally observed in soft X-ray (SXR) emission, the observations that we present demonstrate their visibility at a range of wavelengths including those showing an associated sigmoidal filament. We examine the relationship between the S-shaped structures seen in SXR and those seen in cooler lines in order to probe the sigmoidal region's three-dimensional density and temperature structure. We also consider magnetic field observations and extrapolations in relation to these coronal structures. We present an interpretation of the disk passage of the sigmoidal region, in terms of a twisted magnetic flux rope that emerges into and equilibrates with overlying coronal magnetic field structures, which explains many of the key observed aspects of the region's structure and evolution. In particular, the evolving flux rope interpretation provides insight into why and how the region moves between active and quiescent phases, how the region's sigmoidicity is maintained during its evolution, and under what circumstances sigmoidal structures are apparent at a range of wavelengths. Title: Spectroscopic diagnostics of stellar transition regions and coronae in the XUV: AU Mic in quiescence Authors: Del Zanna, G.; Landini, M.; Mason, H. E. Bibcode: 2002A&A...385..968D Altcode: In this paper we review the spectroscopic diagnostic techniques that can be applied to XUV observations of active stars. In particular, we discuss methods for the determination of electron densities, emission measures and the chemical composition of the stellar transition regions and coronae. We pay particular attention to the atomic data used and we revise several previous analyses with the most recent atomic data (from CHIANTI). We find severe limitations to some of the commonly used methods and atomic data and we obtain results which are significantly different from other authors. We illustrate this with a number of examples. We analyse a combined set of multi-wavelength observations (EUVE, HST/STIS, FUSE) for the quiescent phase of the dMe star AU Mic. A major conclusion of this paper is that the use of spectral lines from the Li and Na isoelectronic sequences, common in previous literature, produces erroneous results in the determination of emission measures, elemental abundances and transition region densities. Title: EUV Spectroscopic Observations of Spray Ejecta from an X2 Flare Authors: Pike, C. D.; Mason, H. E. Bibcode: 2002SoPh..206..359P Altcode: An X2.3 class flare was reported on 10 April 2001 in AR 9415. A halo coronal mass ejection (CME) was associated with this flare. The Coronal Diagnostic Spectrometer (CDS) on board the Solar and Heliospheric Observatory (SOHO), which was running in its daily synoptic mode, recorded a very high-velocity ejection of plasma associated with this activity. The spatial scanning and spectral capabilities of CDS allow the measurement of both transverse and line-of-sight velocities. Components of the plasma, as seen in emission from O v at around 2.5×105 K, reached transverse velocities in excess of 800 km s−1. The nature of the spectral line profiles suggests that a rotational motion of ± 350 km s−1 was superimposed upon the general outward expansion of approximately 150 km s−1. The ejection detected using CDS was found to have a constant acceleration and is thought to be a spray of plasma with a helical structure driven by the magnetic topology. Title: SOHO-CDS Observations of an X2 Flare Spray Injection Authors: Mason, H. E.; Pike, C. D. Bibcode: 2002mwoc.conf...89M Altcode: Spectral observations with SOHO-CDS provide an opportunity to study the development of active region structures. In particular, it is possible to determine the plasma properties: temperature and electron density distribution, elemental abundances and mass motions. The nature of enhancements in the transition region emission is investigated. Title: Sigmoidal diagnostics with SOHO/CDS Authors: Del Zanna, G.; Gibson, S. E.; Mason, H. E.; Pike, C. D.; Mandrini, C. H. Bibcode: 2002AdSpR..30..551D Altcode: During the third Whole Sun Month Campaign (August 18 - September 14, 1999), the evolution of the active region NOAA 8668 was followed during its meridian passage and at the limb (Sigmoid JOP 106), with simultaneous observations with the Solar and Heliospheric Observatory (SOHO), and with other instruments, both satellite and ground-based. On August 21st, a small flare, associated with a brightening of the sigmoidal structure, occurred. SOHO Coronal Diagnostic Spectrometer (CDS) observations of this small flare are presented. Coronal temperatures and densities of the sigmoid are estimated. High transition region densities (in the range 2.5-7 × 10 11 cm -3), obtained using O IV, are present in the brightenings associated with the flare. At coronal level, high temperatures of at least 8 MK were reached, as shown by strong Fe XIX emission. After this small flare, relatively strong blue-shifts (⋍ 30 km/s) are observed in coronal lines, located at the two ends of a small loop system associated with the sigmoid. Title: The CHIANTI Atomic Database and Instrument Calibration: a Symbiosis Authors: Mason, H. E.; Del Zanna, G.; Dere, K. P.; Landi, E.; Landini, M.; Young, P. R. Bibcode: 2002ISSIR...2..271M Altcode: 2002ESASR...2..271M; 2002rcs..conf..271M The CHIANTI atomic database comprises a comprehensive, accurate and up-to-date database of atomic parameters, necessary for emission-line spectroscopy. The suite of user-friendly software allows plasma diagnostics to be carried out. Since its release in 1996, CHIANTI has become a standard resource for the analysis of solar spectra. Accurate atomic data can provide the foundation for in-flight instrument calibrations. Conversely, an accurate instrument calibration can provide a check on atomic parameters. The internal consistency of spectral-line intensities can be used to highlight specific anomalies. In this paper, we illustrate how CHIANTI has been used to validate the calibration of solar EUV instruments: SOHO-CDS, -SUMER, -EIT and SERTS. In addition, we show how anomalous spectral-line intensities indicate the need for more accurate atomic calculations. Title: A Relationship Between Transition Region Brightenings, Abundances, and Magnetic Topology Authors: Fletcher, Lyndsay; López Fuentes, Marcelo C.; Mandrini, Cristina H.; Schmieder, Brigitte; Démoulin, Pascal; Mason, Helen E.; Young, Peter R.; Nitta, Nariaki Bibcode: 2001SoPh..203..255F Altcode: We present multi-instrument observations of active region (AR) 8048, made between 3 June and 5 June 1997, as part of the SOHO Joint Observing Program 33. This AR has a sigmoid-like global shape and undergoes transient brightenings in both soft X-rays and transition region (TR) lines. We compute a magneto-hydrostatic model of the AR magnetic field, using as boundary condition the photospheric observations of SOHO/MDI. The computed large-scale magnetic field lines show that the large-scale sigmoid is formed by two sets of coronal loops. Shorter loops, associated with the core of the SXT emission, coincide with the loops observed in the hotter CDS lines. These loops reveal a gradient of temperature, from 2 MK at the top to 1 MK at the ends. The field lines most closely matching these hot loops extend along the quasi-separatrix layers (QSLs) of the computed coronal field. The TR brightenings observed with SOHO/CDS can also be associated with the magnetic field topology, both QSL intersections with the photosphere, and places where separatrices issuing from bald patches (sites where field lines coming from the corona are tangent to the photosphere) intersect the photosphere. There are, furthermore, suggestions that the element abundances measured in the TR may depend on the type of topological structure present. Typically, the TR brightenings associated with QSLs have coronal abundances, while those associated with BP separatrices have abundances closer to photospheric values. We suggest that this difference is due to the location and manner in which magnetic reconnection occurs in two different topological structures. Title: Elemental abundances of the low corona as derived from SOHO/CDS observations Authors: Del Zanna, G.; Bromage, B. J. I.; Mason, H. E. Bibcode: 2001AIPC..598...59D Altcode: 2001sgc..conf...59D No abstract at ADS Title: A comparison between theoretical and solar FeXII UV line intensity ratios UV line intensity ratios Authors: Binello, A. M.; Landi, E.; Mason, H. E.; Storey, P. J.; Brosius, J. W. Bibcode: 2001A&A...370.1071B Altcode: A new set of radiative and electron collisional data for Fe XII was presented in two earlier papers. In the present work, we derive level populations and theoretical line intensities for a range of plasma densities and temperatures. Observations of Fe XII lines obtained with the Solar EUV Rocket Telescope and Spectrograph are analysed both as a check the quality of the new atomic data and to determine the electron density in active regions and the quiet Sun. The discrepancy between the electron density values determined from Fexii line intensity ratios and those obtained from other ions is investigated. Tables 2-5 are also available in electronic form at the CDS via anonymous ftp to cdarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/370/1071} Title: VizieR Online Data Catalog: Fe XII UV line intensity ratios (Binello+, 2001) Authors: Binello, A. M.; Landi, E.; Mason, H. E.; Storey, P. J.; Brosius, J. W. Bibcode: 2001yCat..33701071B Altcode: A new set of radiative and electron collisional data for Fe XII was presented in two earlier papers. In the present work, we derive level populations and theoretical line intensities for a range of plasma densities and temperatures. Observations of Fe XII lines obtained with the Solar EUV Rocket Telescope and Spectrograph are analysed both as a check on the quality of the new atomic data and to determine the electron density in active regions and the quiet Sun. The discrepancy between the electron density values determined from Fe XII line intensity ratios and those obtained from other ions is investigated. (2 data files). Title: CDS UV Brightenings Explained by Quasi-separatrices and Bald Patches in an S-shape active region Authors: Schmieder, B.; Démoulin, P.; Fletcher, L.; López Fuentes, M. C.; Mandrini, C. H.; Mason, H. E.; Young, P. R.; Nitta, N. Bibcode: 2001IAUS..203..314S Altcode: We present multi-instrument observations of AR 8048, made between June 3 and June5 1997 as part of SoHO JOP033. This active region has a sigmoid-like global shape and undergoes transient erupting phenomena which releases the stored energy. Using a force free field approach, we defined coronal magnetic field lines which fit with the observations. The large-scale magnetic field lines confirms the sigmoid characteristics of the active region. The study in 3D of the configuration explained where and how the energy is released at different places. The Ne VI brightenings correspond to the location of tangent to the photosphere field lines, named "bald patch", they are localized in the low transition region and represent feet of field lines. The Si XII brightenings at coronal temperature are at the top of coronal loops joining quasi-separatrices. Title: Solar Spectroscopy and Diagnostics Authors: Mason, H. Bibcode: 2000eaa..bookE1985M Altcode: Solar spectroscopy and diagnostics provide the opportunity for determining the physical parameters in different parts of the solar atmosphere.... Title: Solar Spectroscopy: Atomic Processes Authors: Mason, H. Bibcode: 2000eaa..bookE2229M Altcode: A Greek philosopher called DEMOCRITUS (c. 460-370 BC) first introduced the concept of atoms (which means indivisible). His atoms do not precisely correspond to our atoms of today, which are not indivisible, but made up of a nucleus (protons with positive charge and neutrons which have no charge) and orbiting electrons (with negative charge). Indeed, in the solar atmosphere, the temperature is suc... Title: Seeking the magnetic roots of a sample of SOHO coronal bright points. Authors: Saba, J. L. R.; Zamkoff, E. B.; Mason, H. E.; Pike, C. D.; Moses, J. D.; Covington, J. F. Bibcode: 2000BAAS...32..808S Altcode: No abstract at ADS Title: SUMER observations of transition region fine structures Authors: Landi, E.; Mason, H. E.; Lemaire, P.; Landini, M. Bibcode: 2000A&A...357..743L Altcode: The SUMER (Solar Ultraviolet Measurements of Emitted Radiation) instrument on SOHO (Solar and Heliospheric Observatory) provides an opportunity to observe and study the solar transition region with high spatial and spectral resolution. We present new evidence to confirm that the emission from the quiet Sun at 2x 105 K is dominated by cool loop-like fine structures which cluster across the chromospheric network boundaries. The electron density of these structures is found to be around 1010 cm-3. The red-shifts in spectral line profiles and the non-thermal widths from lines formed at this temperature are found to be correlated with intensity. The properties of explosive events with irregular profiles are explored. A large jet-like structure is analysed. The results of our analysis are compared with recent predictions from numerical models. Title: Seeking the Magnetic Roots of a Sample of SOHO Coronal Bright Points Authors: Saba, J. L. R.; Zamkoff, E. B.; Mason, H. E.; Pike, C. D.; Moses, J. D.; Covington, J. F. Bibcode: 2000SPD....31.0143S Altcode: As part of an ongoing study of X-ray/EUV bright points (XBPs) in synoptic data from the Coronal Diagnostic Spectrometer (CDS) on the Solar and Heliospheric Observatory (SoHO), we consider six CDS XBP detections for which there are concurrent high-cadence, high-spatial-resolution magnetogram data from the SoHO Michelson Doppler Imager (MDI). All six cases occurred at solar minimum or in the early rise phase of solar cycle 23 (Jul 1996 - Jan 1998). They sample a factor of 10 range in size of XBPs as detected by CDS in an Fe XVI coronal emission line, with peak formation temperature of about 2.5 MK. MDI data are available for over 1.5 hr leading up to each CDS observation, and for at least 0.4 hr after; this allows a detailed study of the magnetic field evolution under the XBP site, including detection of flux emergence or cancellation. EIT data are used to monitor the evolution and persistence of these XBPs in the corona before and after the CDS detections. The nature of the jointly observed XBPs is investigated, in particular the relationship of the plasma parameters and size found with CDS, and the timescales for coronal evolution inferred from EIT, to the character of the underlying magnetic field and its changes as observed with MDI. This work was supported by the SOI/MDI project at Stanford and LMSAL (grant NAG5-3077). HEM and CDP acknowledge the financial support of PPARC. Title: SunBlock '99- An Educational Resource Authors: Pike, C. D.; Mason, H. E.; Walsh, R. W. Bibcode: 2000ASPC..205..141P Altcode: 2000ltse.conf..141P SunBlock `99 is a web-based Public Understanding of Science and educational project which presents the very latest solar research as seen through the eyes of young British scientists. It seeks both to increase public awareness of solar physics and to provide an educational resource for use in the classroom. Title: Dynamics in Restructuring Active Regions Observed During Soho/Yohkoh/Gbo Campaigns Authors: Schmieder, B.; Deng, Y.; Mandrini, C. H.; Rudawy, P.; Nitta, N.; Mason, H.; Fletcher, L.; Martens, P.; Brynildsen, N. Bibcode: 2000AdSpR..25.1879S Altcode: JOP17 and JOP 33 are SOHO Joint Observing Programs in collaboration with Yohkoh/SXT and ground based observatories (GBO's), dedicated to observe dynamical events through the atmosphere. During runs of these programs we observed in restructuring active regions (ARs), surges, subflares, bright knots, but not large flares and jets. From these observations we have been able to derive some of the responses of the coronal and chromospheric plasma to the evolution of the photospheric magnetic field. Emerging flux in an AR led to the formation of Arch Filament Systems in the chromosphere, hot loops and knots in the transition region, and X-ray loops. Frequent surges have been observed in relation to parasitic or mixed polarities, but coronal jets have not yet been found. We discuss the possible mechanisms acting during the restructuring of the active regions (reconnection or ``sea-serpent'' geometries) Title: Atomic data from the IRON Project. XL. Electron impact excitation of the Fe XIV EUV transitions Authors: Storey, P. J.; Mason, H. E.; Young, P. R. Bibcode: 2000A&AS..141..285S Altcode: We calculate collision strengths and thermally averaged collision strengths for electron excitation between the forty energetically lowest levels of Fe13+. The scattering calculation is more complete than any previous work on this ion and significant differences are found in the excitation rates for many of the extreme ultra-violet (EUV) transitions, compared to earlier work. A detailed comparison is made between predicted line intensity ratios and those observed in solar coronal spectra which shows that several outstanding discrepancies are resolved by the new atomic data. Title: Commission 14: Atomic and Molecular Data: (Donnees Atomiques et Moleculaires) Authors: Rostas, F.; Smith, P. L.; Berrington, K. A.; Feautrier, N.; Grevesse, N.; Johansson, S.; Jørgensen, U. G.; Martin, W. C.; Mason, H.; Parkinson, W.; Tchang-Brillet, W. -Ü. L. Bibcode: 2000IAUTA..24..380R Altcode: No abstract at ADS Title: CHIANTI: A database for astrophysical emission line spectroscopy Authors: Del-Zanna, Giulio; Young, Peter; Dere, Ken; Landini, Massimo; Landi, Enrico; Mason, Helen Bibcode: 1999ascl.soft11004D Altcode: CHIANTI consists of a critically evaluated set of atomic data necessary to calculate the emission line spectrum of astrophysical plasmas. The data consists of atomic energy levels, atomic radiative data such as wavelengths, weighted oscillator strengths and A values, and electron collisional excitation rates. A set of programs that use these data to calculate the spectrum in a desired wavelength range as a function of temperature and density are also provided. These programs have been written in Interactive Data Language (IDL) and descriptions of these various programs are provided on the website. Title: Temperature and density in a polar plume - measurements from CDS/SOHO Authors: Young, P. R.; Klimchuk, J. A.; Mason, H. E. Bibcode: 1999A&A...350..286Y Altcode: A detailed analysis of a particularly intense polar plume observed on the 25th of October, 1996, by the Coronal Diagnostic Spectrometer (CDS) on board the Solar and Heliospheric Observatory (SOHO) is presented. Above the limb, emission measure distributions derived for both the plume and a section of coronal hole background are found to be sharply peaked at approximately 1.0-1.1 million degrees in both regions. The temperature rises with height in the background, but no evidence is found for a rising temperature in the plume. The density of the background is approximately 10(8) electrons/cm(3) and falls with height. In the plume the density is between 3.8 and 9.5x 10(8) electrons/cm(3) , and exhibits no decrease with height up to 70 000 km. The plume base is visible on the solar surface and shows a strong brightening lying directly below the main body of the plume. This brightening has a temperature of 2 000 000 K, and a density of 2.5-5.6x 10(9) electrons/cm(3) . Images from lines formed at different temperatures suggest that the morphology of the base is consistent with an emerged bipole in a region of unipolar magnetic flux. A measurement of the Mg/Ne relative abundance is made at two transition region brightenings at the base of the plume. An enhancement of only 1.5 is found over the photospheric value. Considerations of the geometry of both the high temperature brightening at the base of the plume and the off-limb section give filling factors of 0.5 and 1.0, respectively. Title: Variation of Thermal Structure with Height of a Solar Active Region Derived from SOHO CDS and YOHKOH BCS Observations Authors: Sterling, Alphonse C.; Pike, C. D.; Mason, Helen E.; Watanabe, Tetsuya; Antiochos, Spiro K. Bibcode: 1999ApJ...524.1096S Altcode: We present observations of NOAA solar Active Region 7999 when it was near the west solar limb on 1996 December 2 and 3, using data from the Coronal Diagnostic Spectrometer (CDS) experiment on the SOHO satellite. Ratios of intensities of 2 MK material (as observed in CDS Fe XVI images) to 1 MK material (from CDS Mg IX images) indicate that there is a drop in the ratio of the hotter to the cooler material with height in the region, up to an altitude of about 105 km. At low altitudes the relative amount of 2 MK emission measure to 1 MK emission measure ranges from 8 to 10, while the ratio is minimum near 105 km, ranging from 1.3 to 3.5. The decrease with height of the CDS ratio qualitatively resembles the decrease in S XV election temperature with height (measurable up to ~85,000 km) in the same active region obtained from the Bragg crystal spectrometer instrument on Yohkoh. The CDS images indicate that the highest S XV temperatures and largest CDS ratios correspond to regions of microflares, and somewhat lower S XV temperatures and CDS ratios correspond to diffuse regions. Above 105 km, the trend of the CDS ratios changes, either increasing or remaining approximately constant with height. At these altitudes the CDS images show faint, large-scale diffuse structures. Title: SunBlock '99: Young Scientists Investigate the Sun Authors: Walsh, R. W.; Pike, C. D.; Mason, H.; Young, P.; Ireland, J.; Galsgaard, K. Bibcode: 1999ESASP.446..693W Altcode: 1999soho....8..693W SunBlock `99 is a Web-based Public Understanding of Science and educational project which seeks to present the very latest solar research as seen through the eyes of young British scientists. These ``solar guides'' discuss not only their scientific interests, but also their extra-curricular activities and the reasons they chose scientific careers; in other words the human face of scientific research. The SunBlock '99 pages gather a range of solar images and movies from current solar space observatories and discuss the underlying physics and its relationship to the school curriculum. The instructional level is pitched at UK secondary school children (aged 13-16 years). It is intended that the material should not only provide a visually appealing introduction to the study of the Sun, but that it should help bridge the often wide gap between classroom science lessons and the research scientist `out in the field'. SunBlock '99 is managed by a team from the Rutherford Appleton Laboratory and the Universities of St Andrews and Cambridge, together with educational consultants. The production has, in part, been sponsored by PPARC and the Millennium Mathematics Project. Web site addresss: http://www.sunblock99.org.uk Title: Searching for Sigmoids in SOHO/CDS Authors: Gibson, Sarah; Mason, Helen; Pike, Dave; Young, Peter Bibcode: 1999ESASP.446..331G Altcode: 1999soho....8..331G Sigmoidal structures observed in X-rays have been shown to be precursors to CMEs, existing in some cases for several days before an eruption (Sterling and Hudson 1997,ApJ,491,L55; Canfield et al, 1999, GRL, 26, 6, 627). While these S-shaped structures are most apparent in X-ray active region observations, they may be manifestations of a more general helical magnetic structure having observational signatures at other wavelengths. We will present preliminary results of a survey search for sigmoidal structures and other CME tracers in archived SOHO/CDS data for a series of active regions known to contain erupting sigmoidal structures in X-ray observations. We are particularly interested in determining the relative locations and temperatures of these tracers, and will see to what extent the data answers questions such as, if S shapes are observed at different wavelengths do they line up, or is there a spatial displacement and/or rotation of angle of S that corresponds with height/temperature variation ? How does the appearance of the region vary over the lifetime of the observed x-ray sigmoidal structure ? After an eruption, how much if any of the S shape remains, and at what spatial and spectral locations ? We will use the results of this comparison survey to consider what the implications are for the underlying magnetic field structure, and the location and variation of heating throughout it. Title: Electron density and temperature structure of two limb active regions observed by SOHO-CDS Authors: Mason, H. E.; Landi, E.; Pike, C. D.; Young, P. R. Bibcode: 1999SoPh..189..129M Altcode: The analysis of two active regions on the limb using observations from SOHO-CDS allows us to determine the electron density and temperature distribution of the coronal emission. We find that the active regions have hot cores (3×106 K) with larger cooler (106 K) loop structures extending above the limb. The electron number density, determined using the Si X diagnostic line ratio, is found to be highest in the active region core (greater than 2.3×109 cm−3). Electron number density values are determined for a range of spectral lines from different ions and are found to increase with temperature between 0.8 and 2.5×106 K. These results are consistent with recent models of enhanced heating along the compact core of active regions, where the magnetic field shear is strongest. Title: CHIANTI - an atomic database for emission lines. III. Continuum radiation and extension of the ion database Authors: Landi, E.; Landini, M.; Dere, K. P.; Young, P. R.; Mason, H. E. Bibcode: 1999A&AS..135..339L Altcode: CHIANTI provides a database of atomic energy levels, wavelengths, radiative transition probabilities and electron excitation data for a large number of ions of astrophysical interest. This database allows the calculation of theoretical line emissivities necessary for the analysis of optically thin emission line spectra, and includes also a suite of IDL (Interactive Data Language) programs to calculate optically thin synthetic spectra and to perform spectral analysis and plasma diagnostics. The first version (1.0) of the CHIANTI database was released in 1996 te[(Dere et al. 1997)]{Der97} and has been extensively used for analysis of line spectra from astrophysical sources by the scientific community. The present paper describes the first major update to the CHIANTI database which will subsequently be labeled version 2.0. The update consists of the addition of a large number of new ions, the revision of existing data for some ions and the inclusion of an IDL procedure to calculate the continuum. The CHIANTI atomic database and supporting IDL routines are freely available through the internet. Title: Solar Wind Outflow and the Chromospheric Magnetic Network Authors: Hassler, Donald M.; Dammasch, Ingolf E.; Lemaire, Philippe; Brekke, Pal; Curdt, Werner; Mason, Helen E.; Vial, Jean-Claude; Wilhelm, Klaus Bibcode: 1999Sci...283..810H Altcode: No abstract at ADS Title: Calentamiento de arcos coronales en una región activa por reconfiguración topológica del campo magnético. Authors: López Fuentes, M.; Mandrini, C. H.; Démoulin, P.; Schmieder, B.; Fletcher, L.; Mason, H. Bibcode: 1999BAAA...43...24L Altcode: We study the active region (AR) 8048 observed on June 1997 in several wavelenghts. The combined observations obtained using CDS (SOHO) and SXT (Yohkoh) show the heating of the coronal magnetic loops at different atmospheric altitudes. Extrapolating the magnetic field in the corona from longitudinal magnetograms from MDI (SOHO), we determine the location of Bald Patches in the surroundings of the leading spot. This magnetic feature, the emergence of parasitic magnetic polarities and the observed photospheric motions provide the conditions to explain the observed heating. Title: SOHO - Where has the Quiet Sun gone? Authors: Mason, H. E. Bibcode: 1999ASPC..158..348M Altcode: 1999ssa..conf..348M No abstract at ADS Title: Working Group 4 Report: Composition and Elemental Abundance Variations in the Solar Atmosphere and Solar Wind Authors: Mason, Helen E.; Bochsler, Peter Bibcode: 1999SSRv...87..105M Altcode: This paper contains a summary of the topics treated in the working group on abundance variations in the solar atmosphere and in the solar wind. The FIP bias (overabundance of particles with low First Ionization Potentials over photospheric abundances) in coronal holes and coronal hole associated solar wind amounts to values between 1 and 2. The FIP bias in the slow solar wind is typically a factor 4, consistent with optical observations in streamers. In order to distinguish between different theoretical models which make an attempt to explain the FIP bias, some observable parameters must be provided. Unfortunately, many models are deficient in this respect. In addition to FIP fractionation, gravitational settling of heavy elements has been found in the core of long lived streamers. The so-called electron 'freeze in' temperatures derived from in situ observed ionization states of minor ions in the fast wind are significantly higher than the electron temperatures derived from diagnostic line ratios observed in polar coronal holes. The distinction between conditions in plumes and interplume lanes needs to be further investigated. The 'freeze in' temperatures for the slow solar wind are consistent with the electron temperatures derived for streamers. Title: Observation of Transition Region Fine Structures with Soho/Sumer Authors: Landi, E.; Mason, H. E.; Landini, M. Bibcode: 1999SSRv...87..241L Altcode: We present a preliminary analysis of two quiet Sun transition region areas observed with the SOHO/SUMER spectrometer, using lines from oxygen, nitrogen and silicon. The average quiet Sun physical parameters are studied as a function of line intensity. Systematic variations of line position and width with increasing intensity are found. A large number of small-scale active points have been observed, and preliminary analysis of the physical properties and dynamics of these active features is presented. A jet-like structure, found in an active point, is also investigated and its velocity along the line of sight determined. Title: Rotating Transition Region Features Observed with the SOHO Coronal Diagnostic Spectrometer Authors: Pike, C. D.; Mason, H. E. Bibcode: 1998SoPh..182..333P Altcode: Strong evidence has been found from SOHO-CDS (Solar and Heliospheric Observatory - Coronal Diagnostic Spectrometer) observations to support the hypothesis that rotation plays a major role in the dynamics of transition region features. A comprehensive survey of the CDS daily synoptic rasters has been carried out to select dynamic events by searching for spectral line shifts in the O v emission line at 629.73 Å (formed at a temperature of 2.5×105 K). Unique CDS observations of a macrospicule were reported by Pike and Harrison (1997), and several more macrospicule-like solar features have now been identified in the polar regions both on the limb and disk. These show blue- and red-shifted emission on either side of an axis stretching above the limb from a footpoint region on the disk. These observations are interpreted as indicating the presence of a rotating plasma, a sort of solar tornado. In the examples studied, the rotation velocities increase with height. The implications for coronal heating models are discussed. Title: Atomic data from the IRON project. XXXI. Electron impact excitation of optically allowed and intercombination electric dipole transitions in Fe XII Authors: Binello, A. M.; Mason, H. E.; Storey, P. J. Bibcode: 1998A&AS..131..153B Altcode: A new, accurate set of electron impact collisional data is presented, relating to all electric dipole fine-structure transitions between the ground {3s(2) 3p(3) } and the first two excited {3s 3p(4) }, {3s(2) 3p(2) 3d} configurations in {Fe xii} (Fe(11+) ). Theoretical energies have been obtained with a multi-configuration atomic structure calculation. The {R-matrix} method, coupled with the {Coulomb-Bethe} (CBe) approximation for the high partial wave contributions to the collision strengths, has been employed in the Fe(11+) - e(-) scattering problem. The data presented in this paper form part of the IRON Project effort to provide the most accurate atomic data available to date for all the iron ions (Hummer et al. 1993). Tables 1 to 9 are also available in electronic form at the CDS via ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html Title: A new perspective on the sun from SOHO-challenges for atomic physics Authors: Dere, Kenneth; Mason, Helen Bibcode: 1998AIPC..434..213D Altcode: 1998amda.conf..213D The Solar and Heliospheric Observatory (SOHO) carries several ultraviolet spectrometers to diagnose the plasma conditions of the solar atmosphere in order to address several outstanding questions in solar research: why is the corona hot and how is the solar wind accelerated. Diagnostic techniques for determining the magnetohydrodynamic state (magnetic field, density, temperature, velocity) are discussed. We describe the CHIANTI database which has been designed to provide the necessary spectroscopic diagnostics for these data as well as for other spectroscopic missions. The database is built on 3 main files for each ion: atomic energy levels, radiative data, and electron collisional data. The electron collision strengths are assessed and scaled using the Burgess and Tully scaling laws. Analyses of EUV line intensities often reveal discrepancies between observed and predicted line intensities of about of 2 when considering lines of the same ion. A more recent analysis has shown that it is possible to arrive at a subset of EUV spectral lines where the line intensities are reproducible to within about 25%. For X-ray lines, as will be observed by AXAF, there is still considerable need for energy levels, radiative data and collision strengths, particularly for the Δn>=1 transitions. Title: Atomic Physics for Atmospheric Composition Measurements Authors: Young, P. R.; Mason, H. E. Bibcode: 1998SSRv...85..315Y Altcode: The atomic physics relevant to the interpretation of solar spectra produced by plasmas at temperatures ≳ 105 K are discussed. Methods for determining relative abundance ratios are presented and examples provided from the Coronal Diagnostic Spectrometer on board SOHO. In particular, the Fe/Si ratio in the corona is found to be close to photospheric; the Mg/Ne ratio in the transition region is found to vary by an order of magnitude in different solar features. The Mg/Ne ratios in supergranule cell centres and the network are separated for the first time, although no significant differences are found. Title: VizieR Online Data Catalog: IRON Project XXXI. Fe XII electron excitation (Binello+ 1998) Authors: Binello, A. M.; Mason, H. E.; Storey, P. J. Bibcode: 1998yCat..41310153B Altcode: The following tables list energy levels and electron excitation data for the lowest 41 levels of Fe XII (configurations 3s2 3p^3, 3s 3p4 and 3s2 3p2 3d). The table numbers correspond to the numbering given in the paper

(8 data files). Title: Atomic data from the IRON Project. XXV. Electron impact excitation of fine-structure transitions in the ground configuration of Fe XII Authors: Binello, A. M.; Mason, H. E.; Storey, P. J. Bibcode: 1998A&AS..127..545B Altcode: In the framework of the IRON Project we have performed new, fully quantum mechanical atomic calculations for the Fexii (Fe(11+) ) coronal ion. Energy levels, oscillator strengths and spontaneous decay transition probabilities have been computed by including extensive configuration interaction (CI) and relativistic effects in the solution of the atomic structure problem. The R-matrix approach has been employed to solve the electron scattering problem and generate a new set of collisional atomic data. Results are discussed for the ten fine-structure forbidden transitions in the 3s(23p^3) ground configuration of Fexii, and compared with previous calculations. Title: Atomic Physics for Atmospheric Composition Measurements Authors: Young, P. R.; Mason, H. E. Bibcode: 1998sce..conf..315Y Altcode: No abstract at ADS Title: Surges and filaments in active regions during SOHO campaigns Authors: Schmieder, B.; Deng, Y.; Rudawy, P.; Nitta, N.; Mandrini, C. H.; Fletcher, L.; Martens, P.; Innes, D.; Young, P.; Mason, H. Bibcode: 1998ESASP.421..323S Altcode: 1998sjcp.conf..323S No abstract at ADS Title: Dynamic features observed with SOHO-CDS Authors: Mason, H. Bibcode: 1998ESASP.421...95M Altcode: 1998sjcp.conf...95M No abstract at ADS Title: CHIANTI - an Atomic Database For Emission Lines Paper I: Wavelengths Greater than 50 Angstroms Authors: Dere, K. P.; Landi, E.; Mason, H. E.; Fossi, B. C. M.; Young, P. R. Bibcode: 1998ASPC..143..390D Altcode: 1998sigh.conf..390D No abstract at ADS Title: Plasma Diagnostics for the Solar Atmosphere Authors: Mason, Helen E. Bibcode: 1998LNP...507..143M Altcode: 1998sspt.conf..143M Superb observations are now being obtained with the ESA/NASA Solar Heliospheric Observatory (SOHO). In these lectures, I discuss the spectroscopic diagnostic techniques used to analyse ultraviolet and X-ray spectra. Intensities of the spectral emission lines can be used to determine the electron density and temperature structure, element abundances and dynamic nature of different features in the solar transition region and corona. To ensure that these techniques are accurate it is necessary to model all the important atomic processes with the best available atomic data calculations. I discuss the analysis of SOHO spectra and look towards other astrophysical UV and X-ray observations. Title: New Results from the Coronal Diagnostic Spectrometer Authors: Mason, H. E.; Pike, C. D. Bibcode: 1998ASPC..154..431M Altcode: 1998csss...10..431M The Coronal Diagnostic Spectrometer (CDS) on SOHO has provided some exciting new results on the nature of the solar transition region and corona. CDS has as a scientific goal the determination of the physical parameters of the solar plasma, using spectroscopic diagnostic techniques. Intensity ratios of the EUV spectral emission lines (150-785A) have been used to obtain information on the electron density and temperature structure, element abundance and the dynamic nature of various solar features. An overview of these CDS results is presented here. Title: Solar Active Region Movies seen by the SOHO Extreme-ultraviolet Telescope Authors: Newmark, J. S.; Thompson, B.; Gurman, J. B.; Delaboudiniere, J. P.; Aschwanden, Markus; Mason, Helen Bibcode: 1997AAS...191.7307N Altcode: 1997BAAS...29.1321N The Extreme-ultraviolet Imaging Telescope (EIT) on board the SOHO (SOlar and Heliospheric Observatory) satellite provides wide-field images of the corona and transition region on the solar disc and up to 1.4 solar radii above the limb. Its normal incidence multilayer-coated optics select spectral emission lines from FeIX (171 Ang), FeXII (195 Ang), FeXV (284 Ang), and HeII (304 Ang) with 2.6 arcsecond resolution which allow us to describe Solar activity over a wide temperature range. EIT is providing unique EUV observations of the structure and evolution of active regions. Here we show movies of active region 8059 from July 3-10, 1997. The high temporal variability of the AR loops is very evident. Initial temperature and density diagnostics are explored as well as a comparison with diagnostics from the SOHO-CDS instrument. Title: Active Regions Observed in Extreme Ultraviolet Light by the Coronal Diagnostic Spectrometer on SOHO Authors: Fludra, A.; Brekke, P.; Harrison, R. A.; Mason, H. E.; Pike, C. D.; Thompson, W. T.; Young, P. R. Bibcode: 1997SoPh..175..487F Altcode: We present observations of five active regions made by the Coronal Diagnostic Spectrometer (CDS) on the Solar and Heliospheric Observatory (SOHO). CDS observes the Sun in the extreme ultraviolet range 150-780 Å. Examples of active region loops seen in spectral lines emitted at various temperatures are shown. Several classes of loops are identified: those that are seen in all temperatures up to 2 x 106 K; loops seen at 106 K but not reaching 1.6 x 106 K; those at temperatures 2- 4 x 10-5 K and occasionally at 6 x 10-5 K but not reaching 106 K. An increasing loop size with temperature and the relationship between the cool and hot structures is discussed. CDS observations reveal the existence of loops and other unresolved structures in active regions, at temperatures between 1.5- 4 x 10-5 K, which do not have counterparts in lines emitted above 8 x 10-5 K. Bright compact sources only seen in the transition region lines are investigated. These sources can have lifetimes of up to several days and are located in the vicinity of sunspots. We study the variability of active region sources on time scales from 30 sec to several days. We find oscillatory behaviour of Hei and Ov line intensities in an active region on time scales of 5-10 min. Title: CHIANTI - an atomic database for emission lines Authors: Dere, K. P.; Landi, E.; Mason, H. E.; Monsignori Fossi, B. C.; Young, P. R. Bibcode: 1997A&AS..125..149D Altcode: A comprehensive set of accurate atomic data is required for analyses of astrophysical and solar spectra. CHIANTI provides a database of atomic energy levels, wavelengths, radiative data and electron excitation data for ions which are abundant in cosmic plasmas. The most recent electron excitation data have been assessed and stored following the method of \cite[Burgess \& Tully (1992)]{bur92}. The current version is essentially complete for specifying the emission spectrum at wavelengths greater than 50 Angstroms. A list of observed lines in the spectral region between 50 and 1100 Angstroms has been compiled and compared with the lines predicted by the CHIANTI database. The CHIANTI database reproduces the vast majority of lines observed at these wavelengths. CHIANTI includes IDL (Interactive Data Language) routines to calculate optically thin synthetic spectra for equilibrium conditions. IDL routines to calculate theoretical line intensities required for electron density or temperature diagnostics and emission measure studies are also included. The CHIANTI atomic database and supporting IDL routines are available by anonymous FTP. Title: Soho Cds nis in-flight intensity calibration using a plasma diagnostic method Authors: Landi, E.; Landini, M.; Pike, C. D.; Mason, H. E. Bibcode: 1997SoPh..175..553L Altcode: The internal intensity calibration of the Coronal Diagnostic Spectrometer (CDS) - Normal Incidence Spectrometer (NIS) is studied using the Arcetri diagnostic method. A large number of spectral lines observed by the CDS-NIS 1 and NIS 2 windows in a solar active region is analysed in order to determine the intensity calibration curve for both channels. Title: The Mg/Ne abundance ratio in a recently emerged flux region observed by CDS Authors: Young, P. R.; Mason, H. E. Bibcode: 1997SoPh..175..523Y Altcode: Evidence for the existence of the FIP-effect in the transition region is presented here based on recent observations from the Coronal Diagnostic Spectrometer (CDS) on-board the Solar and Heliospheric Observatory (SOHO). Observations of an emerging flux region in lines of Mgv-vii and Nevi-vii reveal differences in the relative Mg/Ne abundance of a factor of 9.2 between two transition region brightenings separated by less than 1 arc min on the Sun. The lower abundance ratio is approximately equal to the photospheric Mg/Ne value and is associated with a small loop-like feature in the central, hottest part of the active region. The higher abundance ratio is found in spike-like structures at the edge of the active region. A density diagnostic of Oiv is used to derive an electron number density of 1011.3 cm-3 for the low Mg/Ne brightening, while a Mgvii diagnostic gives a density of 109.2 cm for the high Mg/Ne brightening. Title: The Ar/Ca relative abundance in solar coronal plasma. Authors: Young, P. R.; Mason, H. E.; Keenan, F. P.; Widing, K. G. Bibcode: 1997A&A...323..243Y Altcode: The relative abundances of elements with low and high first ionisation potentials (FIP) is a subject of much recent debate. In situ measurements of the solar wind reveal a clear pattern of low FIP enhancement that has been followed up with various spectroscopic measurements of the solar corona. Argon is unique amongst the more abundant high FIP elements in retaining several of its electrons at the high temperatures seen in flares. This allows emission lines of different ions to be compared with more confidence than for, say, hydrogen-like high FIP ions such as OVIII and NeX. In this paper we look at emission lines of the boron-like ion ArXIV; in particular, the optical line at 4412Å, seen in eclipse observations, is compared to the CaXIII 4086Å and CaXV 5445Å & 5694Å lines to yield an Ar/Ca abundance of 0.85+/- 0.20. In the extreme ultra-violet (EUV), the ArXIV lines at 187.94Å and 194.41Å can be compared with CaXIV 193.87 Å - flare data from Skylab giving values of 1.10+/-0.25 and 0.55+/-0.21. Analysis of previous work indicates a photospheric Ar/Ca abundance of 1.31+/-0.30, hence supporting the conclusion that elements with high FIP have lower coronal abundances. Title: VizieR Online Data Catalog: CHIANTI - An Atomic Database For Emission Lines I. (Dere+ 1997) Authors: Dere, K. P.; Landi, E.; Mason, H. E.; Monsignori Fossi, B. C.; Young, P. R. Bibcode: 1997yCat..41250149D Altcode: A comprehensive set of accurate atomic data is required for analyses of astrophysical and solar spectra. CHIANTI provides a database of atomic energy levels, wavelengths, radiative data and electron excitation data for ions which are abundant in cosmic plasmas. The most recent electron excitation data have been assessed and stored following the method of Burgess & Tully (1992A&A...254..436B). The current version is essentially complete for specifying the emission spectrum at wavelengths greater than 50Å. A list of observed lines in the spectral region between 50 and 1100Å has been compiled and compared with the lines predicted by the CHIANTI database. The CHIANTI database reproduces the vast majority of lines observed at these wavelengths. CHIANTI includes IDL (Interactive Data Language) routines to calculate optically thin synthetic spectra for equilibrium conditions. IDL routines to calculate theoretical line intensities required for electron density or temperature diagnostics and emission measure studies are also included. The CHIANTI atomic database and supporting IDL routines are available by anonymous FTP. (1 data file). Title: UV and soft X-ray lines from Fe XVI observed in solar and stellar spectra. Authors: Cornille, M.; Dubau, J.; Mason, H. E.; Blancard, C.; Brown, W. A. Bibcode: 1997A&A...320..333C Altcode: The ion Fe XVI is abundant in solar active regions and flares. Strong spectral lines from this ion have been observed over a wide wavelength range. The transitions 3s-3p and 3p-3d fall between 250 and 365Å and lines from transitions between n=3 to n=4, n=3 to n=5 fall between 30 and 80Å. In this paper, we present distorted wave results for the electron scattering collision strengths from the ground level to all the other levels and discuss previous calculations. We compare our theoretical intensity ratios with solar observations and show that the strongest spectral lines in the X-ray wavelength range do not correspond to the dipole transitions, 3s-4p, 3s-5p, as might be expected. We comment on the approximations which have been generally used in synthetic spectrum programs to simulate the Fe XVI spectral line intensities and the consequences for analyses of solar and stellar spectra. Title: Spectral Line Intensities for n = 3-3 EUV Transitions in Fe XV Authors: Bhatia, A. K.; Mason, H. E. Bibcode: 1997ADNDT..66..119B Altcode: Transition rates and collision strengths between the fine-structure levels of Fe XV have been calculated using the configurations 3s2, 3s3p, 3p2, 3s3d, 3p3d, and 3d2and are compared here with other calculations. The present calculations were carried out using the Superstructure and distorted-wave programs developed at University College, London. Level populations and line intensity ratios are calculated for three temperatures with logTe(K) = 6.2, 6.4, and 6.6 and for electron densitiesNe= 108-1012cm-3. Calculated intensity ratios of the emission lines are compared with those observed by the Solar EUV Rocket Telescope and Spectrograph (SERTS) in an active region of sun. The present results should also be useful in analyzing observations from the Solar Heliospheric Observatory (SOHO). Title: New atomic data for the FeXII coronal ion Authors: Binello, A. M.; Mason, H. E.; Storey, P. J. Bibcode: 1997AdSpR..20.2263B Altcode: Various FeXII spectroscopic lines in the UV and EUV range have been proved to be ideal diagnostic tools for measuring electron temperature, density and iron abundance in the solar corona. In the framework of the ``IRON PROJECT'' we have provided improved theoretical calculations of the atomic data required to analyse the intensity of these lines and to apply the results to SOHO (Solar Heliospheric Observatory) observations. Extensive configuration interaction and relativistic effects have been allowed for in the atomic structure computations which have provided energy levels and an extensive set of radiative data. The e-FeXII collisional problem has been tackled with the multichannel R-matrix method, a close-coupling calculation for the determination of electron impact collision strengths. Final results are presented for FeXII thermally averaged collision strengths, for fine-structure forbidden transitions within the ground configuration. Title: Application of Spectroscopic Diagnostics to Early Observations with the SOHO Coronal Diagnostic Spectrometer Authors: Mason, H. E.; Young, P. R.; Pike, C. D.; Harrison, R. A.; Fludra, A.; Bromage, B. J. I.; Del Zanna, G. Bibcode: 1997SoPh..170..143M Altcode: The Coronal Diagnostic Spectrometer (CDS) has as a scientific goal the determination of the physical parameters of the solar plasma using spectroscopic diagnostic techniques. Absolute intensities and intensity ratios of the EUV spectral emission lines can be used to obtain information on the electron density and temperature structure, element abundances, and dynamic nature of different features in the solar atmosphere. To ensure that these techniques are accurate it is necessary to interface solar analysis programs with the best available atomic data calculations. Progress is reported on this work in relation to CDS observations. Title: Extreme ultraviolet observations of the solar corona: first results from the coronal diagnostic spectrometer on SOHO Authors: Harrison, R. A.; Fludra, A.; Sawyer, E. C.; Culhane, J. L.; Norman, K.; Poland, A. I.; Thompson, W. T.; Kjeldseth-Moe, O.; Aschenbach, B.; Huber, M. C. E.; Gabriel, A. H.; Mason, H. E. Bibcode: 1997AdSpR..20.2239H Altcode: We present first results from the Coronal Diagnostic Spectrometer (CDS) aboard the ESA/NASA Solar and Heliospheric Observatory (SOHO). CDS is a double spectrometer operating in the 151-785 A˚ range. This region of the solar spectrum is rich in emission lines from trace elements in the solar atmosphere, which can be used to derive diagnostic information on coronal and transition region plasma. Early spectra are presented and well identified lines are listed. In addition, examples of images in selected wavelength ranges are shown, for a prominence, a loop system and a bright point, demonstrating well the power of such extreme ultraviolet observations. Title: High Coronal Electron Densities in a Solar Flare from Fe XXI and Fe XXII X-Ray Line Measurements Authors: Phillips, K. J. H.; Bhatia, A. K.; Mason, H. E.; Zarro, D. M. Bibcode: 1996ApJ...466..549P Altcode: New calculations of the intensities of the Fe XXI 2p2-2p4l X-ray lines using the distorted wave method are described and compared with observations made by a crystal spectrometer on the Solar Maximum Mission about 6 minutes after the peak of a very intense flare. The comparison enables the electron density of the flare to be derived, the value being about 2 or 3 × 1012 cm-3. Some nearby Fe XXII X-ray lines, scanned 1 minute after flare peak, give an even higher value, 1013 cm-3. This is the first time corroborated values of such high densities have been obtained from ions emitted at temperatures as high as ∼10 MK. They imply very rapid radiation cooling rates and have other important consequences for flare models. Title: CHIANTI - an Atomic Database for Emission Line Spectroscopy: Version 1 - Wavelengths greater than 50 Angstroms Authors: Dere, K. P.; Monsignori-Fossi, B. C.; Landi, E.; Mason, H. E.; Young, P. R. Bibcode: 1996AAS...188.8501D Altcode: 1996BAAS...28..961D A comprehensive set of accurate atomic data is required for analyses of astrophysical and solar spectra. CHIANTI provides an atomic database of energy levels (wavelengths), radiative data and electron excitation data for ions which are abundant in astrophysical plasmas. The most recent electron excitation data have been assessed and stored following the method of Burgess and Tully (1992). CHIANTI includes IDL (Interactive Data Language) routines to produce optically thin synthetic spectra for lambda > 50 Angstroms, assuming equilibrium conditions. It also includes IDL routines to calculate theoretical line intensities required for electron density or temperature diagnostics and emission measure studies. The CHIANTI atomic database and supporting IDL routines are available by anonymous FTP. Title: Atomic data from the IRON Project. XIV. Electron impact excitation of the Fe XIV fine-structure transition ^2^P^o^_1/2_-^2^P^o^_3/2_ Authors: Storey, P. J.; Mason, H. E.; Saraph, H. E. Bibcode: 1996A&A...309..677S Altcode: We calculate collision strengths and collision rates for electron excitation of the ^2^P^o^_1/2_-^2^P^o^_3/2_ ground term fine-structure transition in Fe xiv, the coronal green line at 5303A. The collision strength for the green line is found to be strongly enhanced by resonances for the first 4 Rydberg above the excitation threshold, and as a result the collision rates are found to be significantly larger than other recently published results, even at coronal temperatures. The calculations are carried out using the R-matrix formulation of the close-coupling approximation. Title: New atomic data for the FeXII coronal ion Authors: Binello, A. M.; Mason, H. E.; Storey, P. J.; Kohl, J. Bibcode: 1996ASPC..109..251B Altcode: 1996csss....9..251B No abstract at ADS Title: EUV density diagnostics in solar and stellar spectra Authors: Young, P. R.; Mason, H. E. Bibcode: 1996ASPC..109..301Y Altcode: 1996csss....9..301Y No abstract at ADS Title: EUV Line Intensities of Fe X Authors: Young, P. R.; Mason, H. E.; Bhatia, A. K.; Doschek, G. A.; Thomas, R. J. Bibcode: 1996aeu..conf..583Y Altcode: 1996IAUCo.152..583Y No abstract at ADS Title: Plasma Emission Codes: Comparisons and Critiques Authors: Mason, Helen E. Bibcode: 1996aeu..conf..561M Altcode: 1996IAUCo.152..561M No abstract at ADS Title: High coronal electron densities in a solar flare from Fe XXI and Fe XXII X-ray line ratios. Authors: Phillips, K. J. H.; Bhatia, A. K.; Mason, H. E.; Zarro, D. M. Bibcode: 1996uxsa.conf...75P Altcode: 1996uxsa.coll...75P New distorted-wave calculations of the intensities of the Fe XXI 2p2 - 2p4l X-ray lines are described and compared with observations made during an unusually intense flare. The density sensitivity of some of the lines implies that Ne is between 1012 and 1013cm-3. An even higher value (1013cm-3) is obtained from nearby Fe XXII 2p - 4d lines. This is the first time such high densities have been measured from ions emitted at temperatures as high as ≡107K. They imply very rapid radiation cooling rates, and have other important consequences for flare models. Title: Atomic data for solar VUV spectroscopy (SOHO). Authors: Mason, H. E. Bibcode: 1996uxsa.conf..213M Altcode: 1996uxsa.coll..213M A great deal of effort in recent years has gone into the development of spectroscopic techniques to probe the physical parameters of the solar atmosphere. One aspect of this work is the calculation of new atomic data and the development of plasma emission codes to study spectral lines. This work is being carried out in preparation for the SOHO (Solar Heliospheric Observatory). In this paper, the author presents an overview of the atomic processes involved and an assessment of the accuracy of the parameters which are required for spectroscopic diagnostics in the EUV and UV wavelength ranges. Title: The Coronal Diagnostic Spectrometer for the Solar and Heliospheric Observatory Authors: Harrison, R. A.; Sawyer, E. C.; Carter, M. K.; Cruise, A. M.; Cutler, R. M.; Fludra, A.; Hayes, R. W.; Kent, B. J.; Lang, J.; Parker, D. J.; Payne, J.; Pike, C. D.; Peskett, S. C.; Richards, A. G.; Gulhane, J. L.; Norman, K.; Breeveld, A. A.; Breeveld, E. R.; Al Janabi, K. F.; Mccalden, A. J.; Parkinson, J. H.; Self, D. G.; Thomas, P. D.; Poland, A. I.; Thomas, R. J.; Thompson, W. T.; Kjeldseth-Moe, O.; Brekke, P.; Karud, J.; Maltby, P.; Aschenbach, B.; Bräuninger, H.; Kühne, M.; Hollandt, J.; Siegmund, O. H. W.; Huber, M. C. E.; Gabriel, A. H.; Mason, H. E.; Bromage, B. J. I. Bibcode: 1995SoPh..162..233H Altcode: The Coronal Diagnostic Spectrometer is designed to probe the solar atmosphere through the detection of spectral emission lines in the extreme ultraviolet wavelength range 150 - 800 å. By observing the intensities of selected lines and line profiles, we may derive temperature, density, flow and abundance information for the plasmas in the solar atmosphere. Spatial and temporal resolutions of down to a few arcseconds and seconds, respectively, allow such studies to be made within the fine-scale structure of the solar corona. Futhermore, coverage of large wavelength bands provides the capability for simultaneously observing the properties of plasmas across the wide temperature ranges of the solar atmosphere. Title: The application of atomic physics to the study of solar abundances and their variations Authors: Mason, H. E. Bibcode: 1995AdSpR..15g..53M Altcode: 1995AdSpR..15R..53M The determination of elemental abundances in the solar atmosphere depends critically on the accuracy of the atomic physics assumed in the models. Uncertainties in the electron-ion excitation rates, ionisation and recombination rates or other atomic processes can lead to variations in the derived relative abundance values. In this paper, the different methods used in the analyses of UV and X-ray spectra are explored. Particular attention is paid to the accuracy of the atomic parameters and the assumptions made in the atomic model. A summary is given of the most recent theoretical and laboratory work. Implications for analyses of existing solar datasets and proposed observations (SOHO) are discussed. Title: Atomic data and coronal diagnostics Authors: Mason, H. E. Bibcode: 1995HiA....10..303M Altcode: No abstract at ADS Title: EUV and infra-red lines of FE XIII Authors: Young, P. R.; Mason, H. E.; Thomas, R. J. Bibcode: 1994ESASP.373..417Y Altcode: 1994soho....3..417Y No abstract at ADS Title: Spectroscopic diagnostics in the VUV for solar and stellar plasmas Authors: Mason, H. E.; Fossi, B. C. Monsignori Bibcode: 1994A&ARv...6..123M Altcode: The VUV emission spectra from the solar atmosphere and stellar atmospheres have been intensively studied during the past 25 years with several major space programs. In this review we discuss the spectroscopic diagnostic techniques used to study astrophysical plasmas, the atomic processes involved, the recent observations and the plans for future space missions. Title: Spectroscopic diagnostics for CDS and SUMER Authors: Mason, Helen E. Bibcode: 1994SSRv...70..111M Altcode: The CDS and SUMER instruments will make extensive use of spectroscopic diagnostics to determine the physical parameters of the solar transition region and corona. A great deal of effort is going into the development of these techniques to ensure that they are accurate. This requires interfacing solar analysis programs with the best available atomic data calculations. Recent developments in this work will be presented, with specific examples of useful spectral line ratios. Title: An Assessment of Theoretical Electron Excitation Data for Fe IX-Fe XIV Authors: Mason, H. E. Bibcode: 1994ADNDT..57..305M Altcode: The available theoretical electron excitation data for Fe IX-Fe XIV are assessed and recommendations are made for improvement in future work. The averaged collision strengths are obtained using the interactive, graphical programs of Burgess and Tully. Accurate calculations for these ions are very difficult to carry out because of the complexity of the n = 3 target wave functions. It is evident that a substantial amount of work is still required for some of the ions to obtain results with a high accuracy. Title: A New Synthetic XUV Spectrum Authors: Dere, K. P.; Mason, H. E.; Fossi, B. C. Monsignori; Waljeski, K. H. Bibcode: 1993AAS...18311203D Altcode: 1993BAAS...25.1459D We have begun a program to develop a synthetic XUV spectrum for the 70 - 2500 /AA wavelength region based on a critical analysis of the most recent calculations of atomic parameters, in particular, atomic collision strengths and their thermal averages. Ultraviolet spectra returned by the EUVE and HST instruments demonstrate a continued need for the most accurate atomic parameters in order to determine the physical conditions in the emitting plasmas. Most previous synthetic spectra has relied heavily on the gaunt factor approximation which can predict excitation rates only for dipole transitions and only to within a factor of 2 to 3. In many cases, direct calculations of the collision strengths are now available. Burgess and Tully (1992) have developed a technique for critically evaluating collision strength calculations and scaling and compacting the data. Different scalings are available for resonance, intercombination and forbidden excitations. This method will be applied in the construction of our spectrum. In the end, we intend to produce a set of critically evaluated atomic parameters from which the nearly optically thin spectrum of a low density astrophysical plasma can be calculated, together with the programs necessary to perform these calculations. We will include the ability to prescribe elemental abundances and to correct for optical depth and populations of metastable levels as a function of density. The data sets and programs will be made available by anonymous ftp. Title: Nonthermal Velocities in the Solar Transition Zone Observed with the High-Resolution Telescope and Spectrograph Authors: Dere, K. P.; Mason, H. E. Bibcode: 1993SoPh..144..217D Altcode: Data obtained during the first rocket flight of the NRL High Resolution Telescope and Spectrograph (HRTS) have been used to study nonthermal velocities for spectral lines primarily covering the temperature range 104 to 2 × 106 K. The high spectral and spatial resolution, combined with an enhanced dynamic intensity range of the reduced data, has enabled us to study the distribution of the nonthermal velocities for quiet and active regions. Average values of the nonthermal velocities peak at about 27 km s−1 at 105 K for the quiet regions, with a wide distribution of nonthermal velocities for each line. The active region nonthermal velocities have a narrower distribution which is weighted towards higher values. The SiIV and C IV line profiles are not well described by a single Gaussian, indicating that high-velocity components (above 30 km s−1) are present in the quiet-Sun spectra. The radiative losses for all plasma above l05 K have been calculated for the quiet Sun, an active region and a coronal hole. These have been compared with the acoustic wave flux inferred from the nonthermal line widths. There appears to be a sufficient flux of waves to heat these regions of the atmosphere. Title: Atomic data for the SOHO mission. Authors: Burgess, A.; Mason, H. E.; Tully, J. A. Bibcode: 1993uxrs.conf...97B Altcode: 1993uxsa.conf...97B An interactive computer program has been developed by Burgess and Tully (1992) to assess and store electron excitation collision rates. The program is being used to prepare atomic data which is required to analyse solar and astrophysical spectra. In this paper, the authors present work in progress on several solar ions with spectral lines in the UV wavelength region. These will be observed by the CDS and SUMER instruments to be flown on the SOHO mission. Title: UV and soft X-ray lines from Fe XVI observed in solar and stellar spectra. Authors: Cornille, M.; Dubau, J. A.; Mason, H. E.; Blancard, C.; Brown, W. A. Bibcode: 1993uxrs.conf..101C Altcode: 1993uxsa.conf..101C The ion Fe XVI is abundant in solar active regions and flares. Strong spectral lines from this ion have been observed over a wide wavelength range (30-365 Å) both in astrophysical and laboratory plasmas. In this paper, the authors present new electron scattering collision rates and compare their theoretical intensity ratios with solar observations. The authors note that the approximations often used to simulate Fe XVI soft X-ray lines in solar and stellar spectra are inaccurate. Title: Abundance determination in the quiet corona. Authors: Mason, Helen E. Bibcode: 1992ESASP.348..297M Altcode: 1992cscl.work..297M A study is made of the determination of element abundances in the quiet regions of the solar transition zone and corona. The early work with EUV spectral lines, which is cited in the paper by Meyer (1985), is reviewed together with subsequent analyses of Skylab observations. The intention of this paper is to question some of the assumptions which have been made in these analyses and to look critically at the accuracy of past and present atomic data. The overall aim is to assess what further work is required to adapt these methods for use as diagnostic techniques with the SOHO instruments, in particular CDS and SUMER. Mention is also made of the importance of studying the coronal forbidden lines in the visible and infra-red wavelength regions. Title: Atomic Physics Calculations Relevant to Solar Flare Spectra Authors: Mason, Helen E. Bibcode: 1991RSPTA.336..471M Altcode: Solar flare spectra in the ultraviolet and X-ray wavelength regions are rich in emission lines from highly ionized ions, formed at temperatures around 107 K. These lines can be used as valuable diagnostics for probing the physical conditions in solar flares. Such analyses require accurate atomic data for excitation, ionization and recombination processes. In this paper, we present a review of work which has already been carried out, in particular for the Solar Maximum Mission observations, and we look to future requirements for Solar-A. Title: A Critical Assessment of Electron Excitation between the 2s 22p 2 and 2s2p 3 Configurations of MG +6 Authors: Burgess, A.; Mason, H. E.; Tully, J. A. Bibcode: 1991ApJ...376..803B Altcode: Using the programs RMATRX and DSTWAV, which are based, respectively, on the close coupling and distorted wave approximations, we compute and compare partial collision strengths for the optically allowed transitions between the 2s22p2 and 2s2p3 configurations of Mg+6. From this investigation we conclude that the differences between the published results of Mason and Bhatia (DSTWAV) and Aggarwal (RMATRX) arise not simply because they used different target wave functions, but also because the method used by Aggarwal for treating the outer region in his close coupling calculation is inadequate for optically allowed transitions. Title: Nonthermal Velocities in the Solar Transition Region Authors: Dere, K. P.; Mason, H. E. Bibcode: 1991BAAS...23Q1028D Altcode: No abstract at ADS Title: IR Line Radiation : A Program for Interpolating Atomic Collision Data Authors: Burgess, A.; Chidichimo, M. C.; Mason, H. E.; Tully, J. A. Bibcode: 1991isrs.conf..105B Altcode: No abstract at ADS Title: Atomic physics calculations relevant to solar flare spectra. Authors: Mason, H. E. Bibcode: 1991psf..conf..471M Altcode: Solar flare spectra in the ultraviolet and X-ray wavelength regions are rich in emission lines from highly ionized ions, formed at temperatures around 107K. These lines can be used as valuable diagnostics for probing the physical conditions in solar flares. Such analyses require accurate atomic data for excitation, ionization and recombination processes. The author presents a review of work which has already been carried out, in particular for the Solar Maximum Mission observations. Title: Collision Strengths and Oscillator Strengths for Fe IX Authors: Fawcett, B. C.; Mason, H. E. Bibcode: 1991ADNDT..47...17F Altcode: Collision strengths and oscillator strengths are calculated for Fe IX. The three configurations 3 s23 p6, 3 s23 p53 d, and 3 s23 p54 s were included in the computations. The data can be applied to the analysis of spectral lines in the solar spectrum and laboratory sources. The collision calculations were executed with the DISTORTED WAVE collision code and SUPERSTRUCTURE atomic-structure code interfaced via transformation code JAJOM. These codes were written at University College London. As reported in a previous publication, the codes were adapted to enable the adjustment of Slater parameters leading to improved energy levels and eigenvectors. The Cowan suite of atomic-structure codes was used to generate the adopted optimized parameters and also to compute oscillator strenghts. Possible application of the method to more complex atomic structures was investigated. Title: Density measurements in the corona Authors: Mason, Helen E. Bibcode: 1991AdSpR..11a.293M Altcode: 1991AdSpR..11..293M A knowledge of the electron density in the solar atmosphere is fundamental to our understanding of the dominant physical processes. The field of spectroscopic diagnostics is therefore an area of major interest in the analysis of space observations. In this paper, we review techniques which are used for determining the electron density in the corona, with reference to UV and X-ray observations. Particular attention is given to the accuracy of the methods, including an assessment of the atomic parameters. Future projects are discussed, such as the CDS and SUMER instruments on SOHO which will make extensive use of spectroscopic diagnostics. Title: The Interpretation of the Spectral Line Intensities from the Chase Spectrometer on SPACELAB-2 Authors: Lang, J.; Mason, H. E.; McWhirter, R. W. P. Bibcode: 1990SoPh..129...31L Altcode: In this paper we analyse the solar spectral intensities observed with the CHASE grazing incidence telescope and spectrometer flown on NASA's Spacelab 2 Mission in 1985. Our main purpose has been to investigate the sources of error that arise in the application of the differential emission measure technique used to analyse such data. We suggest methods by which these sources of error may be investigated. Title: Spectroscopic diagnostics for ions observed in solar and cosmic plasmas Authors: Mason, Helen E. Bibcode: 1990hrxr.conf...11M Altcode: 1990IAUCo.115...11M The X-ray wavelength region (1-200 A) is rich in spectral lines from highly ionized systems. Spectra from the solar atmosphere have been studied extensively with various instruments covering different wavelength regions. The solar spectral line emission with particular reference to iron ions and helium-like ions observed during solar flares is discussed. The atomic processes involved in the calculation of theoretical intensities for low-density plasmas are outlined together with the diagnostic properties of the emission lines. Comparisons are made with available cosmic X-ray spectra and predicted spectra for future projects, such as AXAF. Title: UV and EUV Spectroscopy of the Upper Solar Atmosphere Authors: Mason, H. E. Bibcode: 1990PDHO....7..232M Altcode: 1990dysu.conf..232M; 1990ESPM....6..232M The UV and EUV wavelength regions are rich in emission lines from the transition region and the corona. Spectroscopic diagnostic techniques have been used extensively to determine the physical conditions in the solar atmosphere for such diverse phenomena as coronal holes, active regions surges, flares. The author reviews diagnostic techniques which have been used in the analyses of space observations (eg Skylab, SMM, HRTS, CHASE) and looks to future projects such as the CDS and SUMER instruments on SOHO which cover the UV and EUV wavelength regions and will provide a wealth of observations with excellent spatial, spectral and temporal resolution. Title: A comparison of theoretical and solar-flare intensity ratios for the Fe XIX X-ray lines Authors: Bhatia, A. K.; Fawcett, B. C.; Phillips, K. J. H.; Lemen, J. R.; Mason, H. E. Bibcode: 1989MNRAS.240..421B Altcode: Atomic data including energy levels, gf-values, and wavelengths are given for the Fe XIX transitions that give rise to lines in solar-flare and active-region X-ray spectra. Collision strengths and theoretical intensity ratios are presented for lines which occur in the 13.2-14.3-A range. Observed spectra are found to be consistent with those derived from the present Fe XIX atomic data. For the case of spectra in which the Fe XIX lines are very strong, such as those at the maxima of hot flares, two observed line features due to Fe XIX are shown to have larger intensities than calculated. The calculated Fe XIX and Ne IX line spectra are used to determine electron densities from Ne IX line ratios. Title: Solar Astrophysics SIG Authors: Mason, Helen Bibcode: 1989StarB...4....9M Altcode: No abstract at ADS Title: Coronal Mg(9+) - Collisional excitation of the 2s-2p multiplet Authors: Burgess, A.; Mason, H. E.; Tully, J. A. Bibcode: 1989A&A...217..319B Altcode: Electron impact excitation of the astrophysically important 2s-2p multiplet in lithium-like Mg(9+) is discussed. The collision strength for this optically allowed transition is computed using a two state model ion with the close coupling approximation. At high impact energies a distorted wave approximation is used. The contribution from distant encounters is determined by the Coulomb Bethe approximation. The Burgess-Tully method is used to interpolate the results and to evaluate the thermally averaged collision strength from which the rate coefficient is readily obtained. Title: A Slater Parameter Optimization Method Applied to the Computation of Collision Strengths for Fe XIII Authors: Fawcett, B. C.; Mason, H. E. Bibcode: 1989ADNDT..43..245F Altcode: Details of a new computational method for calculating collision strengths are presented through an application to Fe XIII. The method, which enables the computation of collision strengths for complex ions, is adapted from long-established optimization techniques previously used for the calculation of atomic energy levels and oscillator strengths. The procedure involves the adjustment of Slater parameters and average energies of configurations so that they result in improved energy levels and eigenvectors. These improved values can then provide a basis for collision strength calculations in ions where ab initio computations break down or result in unnecessarily large errors. The present application is implemented through modifications of the DISTORTED WAVE collision code and SUPERSTRUCTURE atomic-structure code interfaced via a transformation code JAJOM, which also processes their output; these atomic codes were written at University College London. It should be feasible to make similar adaptions to other collision codes. The Cowan suite of atomic-structure codes generated the optimized parameters. Fe XIII collision strengths are tabulated for 3 s23 p2-3 s3 p3 and 3 s23 p2-3 s23 p3 d transitions. Six configurations, 3 s23 p2, 3 p4, 3 s3 p3, 3 s23 p3 d, 3 s3 p3 d2, and 3 p33 d, were included in these computations. Title: Solar Astrophysics Authors: Mason, Helen Bibcode: 1988StarB...2....8M Altcode: No abstract at ADS Title: A New Aid for Interpolating and Assessing Collision Strengths and Rate Coefficients Authors: Burgess, A.; Mason, H. E.; Tully, J. A. Bibcode: 1988JPhys..49..107B Altcode: 1988IAUCo.102..107B No abstract at ADS Title: Spectroscopic techniques for determining electron densities in the solar atmosphere. Authors: Mason, H. E. Bibcode: 1988JPhys..49...13M Altcode: 1988IAUCo.102...13M An overview is given of the methods used for determining electron densities in the solar atmosphere. This includes a discussion of the accuracy of the atomic parameters required in such analyses. Several different approximations are used to calculate electron scattering cross-sections. These are outlined and their accuracy for individual ions is assessed. A lot of effort has gone into the determination of the electron densities in solar flares, particularly during the impulsive phase. Such studies are crucial to distinguish between various theoretical flare models. These problems are discussed in relation to analyses of spectral data from SKYLAB, HRTS, SMM, SOLEX and XSST and with a view to future projects such as SOHO. Title: Spectral Line Profiles of Fe XXI 1354.1 Angstrom from the Solar Maximum Mission Authors: Mason, H. E.; Shine, R. A.; Gurman, J. B.; Harrison, R. A. Bibcode: 1986ApJ...309..435M Altcode: Observations of the Fe XXI 1354.1 A line were obtained for several flares using the SMM-UVSP instrument with varying spectral and spatial resolution. Of special interest are spectral line profiles from the footpoints of flare loops taken during the impulsive phase. These data show blueshifted Fe XXI profiles coincident and cospatial with the impulsive brightening of chromospheric material. The present analysis supports the hypothesis that the blueshifted component of the high temperature emission is an integral part of the flare, possibly associated with chromospheric evaporation. Title: Further atomic calculations for Fe XXIII Authors: Bhatia, A. K.; Mason, H. E. Bibcode: 1986A&A...155..413B Altcode: Electron collision strengths for Fe XXIII have been obtained using the 'distorted wave' approximation. Previous results (Bhatia and Mason, 1981) were obtained including the configurations 2s(2), 2s2p, 2p(2), 2s3s, 2s3p, and 2s3d. In this paper, the correlation configurations 2p3s, 2p3p and 2p3d have also been included in the solution of the electron scattering problem. Title: Electron Density Diagnostics in the 10--100 Angstrom Interval for a Solar Flare Authors: Brown, W. A.; Bruner, M. E.; Acton, L. W.; Mason, H. E. Bibcode: 1986ApJ...301..981B Altcode: Electron density measurements from spectral-line diagnostics are reported for a solar flare on July 13, 1982, 1627 UT. The spectrogram, covering the 10-95 A interval, contained usable lines of helium-like ions C V, N VI, O VII, and Ne IX which are formed over the temperature interval 0.7-3.5 x 10 to the 6th K. In addition, spectral-line ratios of Si IX, Fe XIV, and Ca XV were compared with new theoretical estimates of their electron density sensitivity to obtain additional electron density diagnostics. An electron density of 3 x 10 to the 10th/cu cm was obtained. The comparison of these results from helium-like and other ions gives confidence in the utility of these tools for solar coronal analysis and will lead to a fuller understanding of the phenomena observed in this flare. Title: Theoretical intensity ratios for the X-ray lines from CA XV Authors: Bhatia, A. K.; Mason, H. E. Bibcode: 1986A&A...155..417B Altcode: Electron collision strengths for Ca XV have been obtained using the 'distorted wave' approximation. Previous results (Mason, 1975; Dere et al., 1979) were obtained for the configurations 2s22p2, 2s2p3, 2p4. The authors present results for transitions 2s22p2 → 2s22p3s, 2s22p3d which give rise to lines in the X-ray spectra of solar active regions and flares. Title: Interpretation of EUV spectra from loop structures in an active region at the limb Authors: Doyle, J. G.; Mason, H. E.; Vernazza, J. E. Bibcode: 1985A&A...150...69D Altcode: EUV spectral scans and rasters of an active region observed at the limb are analyzed. These were obtained with the Harvard EUV spectroheliometer on the Apollo Telescope Mount. The spectra were taken following a small flare and an H-alpha surge. Diagnostic line ratios are used to determine electron densities and temperatures from the spectral scans. An electron pressure of 10 to the 15th/cu cm K is derived at 200,000 K. The temperatures derived from the diagnostic ratios indicate that the plasma is in ionization equilibrium, although mass flows of a few kilometers per s could be present. Rasters of the active region taken later show well defined loop structures. The parameters derived from the low temperature lines (100,000 K) and the rasters are inconsistent with those inferred from scaling laws based on static loop models. However, better agreement between the derived parameters and the models is achieved if use is made of the electron density derived from the emission measure of Mg X, and it is assumed that it remains constant up to 5-million K. Title: Multiwavelength Analysis of a Well Observed Flare from Solar Maximum Mission Authors: MacNeice, P.; Pallavicini, R.; Mason, H. E.; Simnett, G. M.; Antonucci, E.; Shine, R. A.; Rust, D. M.; Jordan, C.; Dennis, B. R. Bibcode: 1985SoPh...99..167M Altcode: We describe and analyse observations of an M1.4 flare which began at 17: 00 UT on 12 November, 1980. Ground based Hα and magnetogram data have been combined with EUV, soft and hard X-ray observations made with instruments on-board the Solar Maximum Mission (SMM) satellite. The preflare phase was marked by a gradual brightening of the flare site in Ov and the disappearance of an Hα filament. Filament ejecta were seen in Ov moving southward at a speed of about 60 km s−1, before the impulsive phase. The flare loop footpoints brightened in Hα and the CaXIX resonance line broadened dramatically 2 min before the impulsive phase. Non-thermal hard X-ray emission was detected from the loop footpoints during the impulsive phase while during the same period blue-shifts corresponding to upflows of 200-250 km s−1 were seen in Ca XIX. Evidence was found for energy deposition in both the chromosphere and corona at a number of stages during the flare. We consider two widely studied mechanisms for the production of the high temperature soft X-ray flare plasma in the corona, i.e. chromospheric evaporation, and a model in which the heating and transfer of material occurs between flux tubes during reconnection. Title: Fe XIX transitions within the N = 2 complex Authors: Loulergue, M.; Mason, H. E.; Nussbaumer, H.; Storey, P. J. Bibcode: 1985A&A...150..246L Altcode: The authors calculate the atomic data necessary for the interpretation of the Fe XIX spectra emitted by solar flare and tokamak plasmas. They consider the transitions between the 2s22p4, 2s2p5,and 2p6 configurations. Some of the Fe XIX lines are potentially useful for determining electron density, and for one XUV flare spectrum they find evidence to indicate an electron density in excess of 1013cm-3. Title: Flare Electron Densities Using X-ray Line Ratios Authors: Brown, W. A.; Bruner, M. E.; Acton, L. W.; Mason, H. E. Bibcode: 1985BAAS...17R.629B Altcode: No abstract at ADS Title: Diagnostic Application of Highly Ionised Iron Lines in the Extreme Ultraviolet Spectrum of a Solar Flare Authors: Mason, H. E.; Bhatia, A. K.; Kastner, S. O.; Neupert, W. M.; Swartz, M. Bibcode: 1984SoPh...92..199M Altcode: Recent atomic data have been used to analyze a solar flare spectrum obtained with the Goddard Space Flight Center's grating spectrometer on the OSO-5 satellite. There exist in the wavelength region 90-200 Å strong lines from each of the ions Fe XVIII-Fe XXIV. The Fe XXI lines can be used as an electron density diagnostic for the 107 K plasma. From our analysis of a particular flare, we find a steep positive slope in the emission measure between 106.5 and 107.2 K and an electron density of ∼4 × 1011 cm−3 at 107 K. We emphasise the need for high spectral and spatial resolution observations of solar flares in this wavelength region, which has to date been largely neglected. Title: Evidence for Chromospheric Evaporation in Solar Flares from UV Observations Authors: Shine, R. A.; Mason, H. E. Bibcode: 1984BAAS...16..543S Altcode: No abstract at ADS Title: Atomic Calculations for the Highly Ionized Iron Ions Produced in Solar Flares Authors: Mason, H. E.; Bhatia, A. K. Bibcode: 1984uxsa.coll..141M Altcode: 1984uxsa.conf..141M; 1984IAUCo..86..141M No abstract at ADS Title: Atomic calculations for the Fe XX X-ray lines Authors: Mason, H. E.; Bhatia, A. K. Bibcode: 1983A&AS...52..181M Altcode: The atomic data presented here and in Bhatia and Mason (1980) allow the calculation of theoretical intensity ratios for all the EUV, UV, and X-ray lines from Fe XX. Tabulations are presently given for the transitions between levels in the 2s2 2p3, 2s2 2p2 3s, and 2s2 2p2 3d configurations of Fe(19+), and electron collision strengths are calculated by means of the 'distorted wave' approximation. In addition to the theoretical X-ray line intensity ratios, new spectral line identifications from a solar flare are presented. Title: Atomic calculations for CA XVII - UV and X-ray lines Authors: Bhatia, A. K.; Mason, H. E. Bibcode: 1983A&AS...52..115B Altcode: Doschek et al. (1977) have pointed out the importance of the Ca XVII UV lines as an electron density diagnostic. Energy levels, transition probabilities, and collision strengths, are presently obtained for the 2s2, 2s 2p, 2p2, 2s 3s, 2s 3p, and 2s 3d configurations of Ca XVII, and the theoretical intensity ratios for the UV and X-ray lines are compared with observed intensities in solar flare spectra. Inconsistencies are indicated in the analysis of UV data, and discrepancies between observed and theoretical intensity ratios indicate that further studies are required. New identifications are suggested in the X-ray wavelength region. Title: Solar flare X-ray spectra from the Solar Maximum Mission Flat Crystal Spectrometer Authors: Phillips, K. J. H.; Fawcett, B. C.; Kent, B. J.; Gabriel, A. H.; Leibacher, J. W.; Wolfson, C. J.; Acton, L. W.; Parkinson, J. H.; Culhane, J. L.; Mason, H. E. Bibcode: 1982ApJ...256..774P Altcode: High-resolution solar X-ray spectra obtained with the Flat Crystal Spectrometer aboard the Solar Maximum Mission from two solar flares and a nonflaring active region are analyzed. The 1-22 A region was observed during the flare on 1980 August 25, while smaller spectral regions were repeatedly covered during the 1980 November 5 flare. Voigt profiles were fitted to spectral lines to derive accurate wavelengths and to resolve blends. During the August 25 flare, 205 lines were found in the range 5.68-18.97 A, identifications being provided for all but 40 (mostly weak) lines. Upper limits to flare densities are derived from various line ratios, the hotter (about 10 to the 7th K) ions giving an electron density of less than 10 to the 12th per cu cm for the August 25 flare. Other observed line ratios (e.g., in Fe XVII and Mg XII) indicate a need for revisions in theoretical calculations. Title: Solar physics Authors: Gabriel, A. H.; Mason, H. E. Bibcode: 1982aacp....1..345G Altcode: A review is presented of the two major aspects of the interaction between atomic and solar physics. The first aspect is related to the way in which the various atomic collision processes determine the physical behavior of the plasma, and, thereby, the physical properties of the sun. The second aspect is concerned with diagnostics, taking into account the way in which the spectra emitted are determined by the atomic processes occurring in the observed plasma. Aspects of solar physics involving atomic collisions are examined, giving attention to radial structure, active regions, solar flares, element abundances, and spectroscopic diagnostics. Questions of impact excitation are considered along with ionization and recombination, absolute spectral intensities, and radiation effects. Title: Solar Physics Authors: Gabriel, Alan H.; Mason, Helen E. Bibcode: 1982aacp....1..346G Altcode: No abstract at ADS Title: Atomic calculation for Fe XXIII, UV, and X-ray lines. Authors: Bhatia, A. K.; Mason, H. E. Bibcode: 1981A&A...103..324B Altcode: Electron-ion scattering data have been obtained for the configurations 22, 2s2p, 2p2, 2s3s, 2s3p, and 2s3d of Fe XXIII in the "distorted wave" approximation. Oscillator and collision strengths are compared with other calculations. Wavelengths for various UV and X-ray lines are compared with laboratory measurements. New identifications are given for recent solar spectra based on intensity estimates. A line at 11.737 Å is identified as the strongest Fe XXIII line in the solar X-ray spectrum. Title: Spectroscopic diagnostics of the active region: transition zone and corona. Authors: Dere, K. P.; Mason, H. E. Bibcode: 1981sars.work..129D Altcode: Techniques currently used in the analysis of X-ray and UV spectroscopic data on solar features are reviewed with particular emphasis on those used for studies of active regions in the transition zone and corona. Attention is given to temperature and emission measure diagnostics by the use of line emission from a low-density plasma, broadband X-ray diagnostics, and diagnostics specific to various active region structures, and to electron density diagnostics based on metastable levels and the ratio of emission measure to the volume derived from spatially resolved images. Methods used for calculating atomic structure, electron and proton scattering, the ionization equilibrium and the effects on it of diffusion and flows, and the line profiles and optical depths are also considered. Title: Atomic Data for the Interpretation of EUV Astrophysical Plasmas Authors: Mason, H. E. Bibcode: 1981ebas.conf...81M Altcode: No abstract at ADS Title: The Development of Flares Observed in the Spectral Lines OV 1371 Å, FeXXI 1354 Å, and in Hard X-Rays Authors: Woodgate, B. E.; Bruner, E. C.; Cheng, C. C.; Dennis, B. R.; Gurman, J. B.; Frost, K. J.; Hyder, C. L.; Kiplinger, A.; Mason, H. E.; Orwig, L. E.; Poland, A. I.; Schoolman, S. A.; Shine, R. A.; Tandberg-Hanssen, E. A. Bibcode: 1980BAAS...12..911W Altcode: No abstract at ADS Title: Atomic data for Fe XXII Authors: Mason, H. E.; Storey, P. J. Bibcode: 1980MNRAS.191..631M Altcode: Intermediate coupling energy levels, oscillator strengths and electron collision strengths in the distorted wave approximation have been computed for Fe XXII. Results are tabulated for the configurations 2s22p, 2s 2p2, 2s23s, 2s23d, 2s 2p 3p, 2s24s, 2s24d, 2s 2p 4p. The level population of the excited level in the ground configuration is given as a function of electron density together with theoretical intensity ratios for the strongest transitions from the excited configurations. The theoretical results are compared to available solar flare observations. The intensity ratios observed correspond to electron densities of less than 10 to the 13 per cu cm. Title: Theoretical atomic structure and electron scattering data for ions in the nitrogen isoelectronic sequence - MG VI, SI VIII, S X, A XII and CA XIV Authors: Bhatia, A. K.; Mason, H. E. Bibcode: 1980MNRAS.190..925B Altcode: Intermediate coupling energy levels, oscillator strengths and electron collision strengths have been computed for the configurations 2s22p3, 2s2p4 of Mg VI, Si VIII, S X, Ax II and Ca XIV. The electron scattering problem was solved using the "distorted wave" approximation. The statistical equilibrium equations for level populations were solved including all relevant excitation and de-excitation mechanisms. The level populations for the ground configuration and theoretical intensity ratios for the UV spectral lines are tabulated for conditions appropriate to the solar atmosphere. Title: New atomic data for Fe/+19/ Authors: Bhatia, A. K.; Mason, H. E. Bibcode: 1980A&A....83..380B Altcode: New atomic data are tabulated for Fe(+19). The electron collision strengths are calculated using the 'distorted wave' approximation and results are presented for several energies of the exciting electron. The populations of the ground levels are calculated as a function of electron density under conditions appropriate to solar flares and tokamak plasmas. Theoretical intensity ratios are tabulated for the UV lines. Title: EUV limb spectra of a surge observed from Skylab. Authors: Doschek, G. A.; Feldman, U.; Mason, H. E. Bibcode: 1979A&A....78..342D Altcode: The EUV spectra of a surge observed at plus 8 in. and plus 20 in. above the white light limb from Skylab are examined. The shape of the differential emission measure determined at 8 in. and 20 in. is nearly the same as for a quiet Sun spectrum at 8 in., but the emission measure of the surge at 8 in. is about an order of magnitude greater than for the quiet Sun. At 20 in. the emission measure of the surge is initially close to the quiet Sun distribution, but decreases by a factor of 4 within 6 min. The optically thin lines formed near 10 to the 5th power K show nonthermal broadening at 8 in., and electron densities near this temperature are derived from intersystem to resonance ratios. The volume of the emitting plasma at 8 in. above the limb was determined, concluding that a continuous energy input is required to explain the observations. Title: XUV electron density diagnostics for solar flares. Authors: Dere, K. P.; Mason, H. E.; Widing, K. G.; Bhatia, A. K. Bibcode: 1979ApJS...40..341D Altcode: Potential electron-density diagnostics for the high-temperature component of solar flares are studied with reference to the wavelength region from 171 to 630 A. The specific ions discussed include Fe IX through Fe XV, Ni XI through Ni XVII, and ions in the beryllium, boron, carbon, and nitrogen isoelectronic sequences. Line ratios that could be useful as density indicators under solar-flare conditions are indicated, available data for the ions considered are reviewed, and several theoretical intensity ratios are plotted. The results are employed to determine the electron-density distribution as a function of electron temperature for several spectra from two flares. For these flares it is found that the electron density increases from 10 billion to 500 billion per cu cm for a temperature increase from 1 million to 10 million K. Title: Fe XXI as an electron density diagnostic in solar flares. Authors: Mason, H. E.; Bhatia, A. K.; Doschek, G. A.; Feldman, U. Bibcode: 1979A&A....73...74M Altcode: Atomic data have been calculated for Fe XXI, and the theoretical intensity ratios for many transitions are tabulated. Fe XXI lines in wavelength regions 1-25 A, 90-200 A, and 300-2500 A are discussed with reference to presently available solar and laboratory spectra. It is found that Fe XXI is an excellent density diagnostic for solar-flare and tokamak plasmas, when densities are in the range from 10 to the 11th to 10 to the 15th per cu cm. The theoretical calculations are applied to flare spectra obtained from OSO 5, and an electron density of less than 10 to the 13th per cu cm is deduced for a temperature of 10,000,000 K. The results are somewhat ambiguous in several cases because of the limited spectral and temporal resolution of these earlier spectrometers. However, the calculations will be important for forthcoming solar projects, such as the Solar Maximum Mission. Title: Electron densities in the solar corona from density-sensitive line ratios in the N I isoelectronic sequence. Authors: Feldman, U.; Doschek, G. A.; Mariska, J. T.; Bhatia, A. K.; Mason, H. E. Bibcode: 1978ApJ...226..674F Altcode: Electron densities are derived in the solar inner corona from forbidden lines of S x near 1100 A. The density-sensitive line ratio considered is (4S0312-2D0312)/(4S0312-2D0612). The ratio is calculated as a function of density for four ions of the N I isoelectronic sequence, i.e., Mg VI, Si VIII, S x, and Ar XII. The variation of the ratio (4S0312-2P0312)/(4S0312-2D0312) with density is also calculated. The results are applied to off-limb spectra recorded by the NRL Skylab spectrograph. Densities were found to be the same in five quiet Sun regions and four active regions observed at heights > 8" outside the white-light limb. The average density derived from the S x lines for all regions considered is 1.0 x 10 cm -3. This result applies to plasma at the temperature of formation of S x, i.e., 1.3 x 106 K. At heights greater than 20" outside the limb the average density is 7.7 x 108 cm -3, and between 8" and 12" above the limb the average density is 1.0 x 10 cm 3, for both quiet Sun and active regions. Subject heading: Sun: corona Title: Density sensitivity of the solar EUV emission from boron-like ions. Authors: Vernazza, J. E.; Mason, H. E. Bibcode: 1978ApJ...226..720V Altcode: The paper investigated the level populations and the line emission arising from ions of the boron isoelectronic sequence from C II to Ca XVI. It is found that, under conditions present in the solar corona, some of these ions have pairs of emission lines having intensity ratios which are density-sensitive. The boron-like lines observed in the solar spectrum between 300 and 1350 A are analyzed, and densities for quiet and active regions, coronal holes, sunspots, and flares are derived. Some aspects of the differences in the behavior of the emission from the lithium and boron sequences are also discussed. Title: Densities in the quiet sun and polar coronal holes from EUV line ratios involving O III (1666.15 Å). Authors: Doschek, G. A.; Feldman, U.; Bhatia, A. K.; Mason, H. E. Bibcode: 1978ApJ...226.1129D Altcode: The EUV line intensity ratios C iii (1908.73 A)/o iii (1666.15 A), 0 iii (1666.15 A)/Si iv (1402.77 A), and C iii (1908.73 A)ISi iv (1402.77 A) are shown to be sensitive to variations in the electron density at densities typical of the quiet Sun ( 1010 cm - at 6 x 10 K). Using the 0 iii line, the above ratios can be normalized to observational data and densities in quiet-Sun regions and coronal holes can be determined. The average value of the density determined for three quiet-Sun regions is 1.9 x 1010 cm - . The densities determined from several observations of the north and south polar coronal holes are about the same as in the quiet Sun, with the exception of one set of observations of the north polar hole that indicates a density about a factor of 2 less than that of the quiet Sun. Subject headings: Sun: corona - Sun: spectra - ultraviolet: spectra Title: Theoretical intensity ratios for the UV lines of Mg VII, Si IX and S XI. Authors: Mason, H. E.; Bhatia, A. K. Bibcode: 1978MNRAS.184..423M Altcode: Energy levels, oscillator strengths, and electron collision strengths have been computed for the configurations 2s2 2p2, 2s 2p3, 2p4 of Mg VII, Si IX, and S XI. Level populations for the ground configuration and theoretical intensity ratios for the UV lines are tabulated for electron densities and temperatures appropriate to the solar atmosphere. The identification of the Mg VII, Si IX, and S XI UV lines is discussed. Title: Limb-brightening observations from the OSO-7 satellite. III. Comparison of EUV line intensities of Fe XII, Fe XI, Fe XV, Si X and S XII, Si IX and S XI with predictions. Authors: Kastner, S. O.; Mason, H. E. Bibcode: 1978A&A....67..119K Altcode: Continuing a study of heliocentric dependence of EUV emission line intensities observed by the Goddard OSO-7 spectroheliograph in 1972, the variation of lines of the ions Fe XII, Fe XI, Fe XV, Si X and S XII, Si IX and S XI is compared with the results of individual calculations for these ions, including theoretical intensities presented for Fe XII and Fe XI. Agreement is found to be good for Fe XII and reasonable for some of the lines of the other ions which in general are weaker in intensity. Several apparent anomalies are found however which may be due to unknown line components near the wavelengths observed. Title: On the unidentified forbidden coronal lines. Authors: Mason, H. E.; Nussbaumer, H. Bibcode: 1977A&A....54..547M Altcode: Approximately one quarter of the forbidden coronal lines observed in the visual and EUV regions of the solar spectrum are still unidentified. Evidence is presented showing that some of these unidentified lines originate from Fe X and Fe XI. Population densities of metastable levels in excited configurations of these ions are determined, and emissivities are calculated for transitions from these levels. Based on examination of emissivity ratios, it is proposed that the forbidden coronal lines observed at 4312, 3454, 1918.27, 1603.31, and 1428.76 be attributed to Fe X and that the lines at 5539, 4566, and 264 A be attributed to Fe XI. Title: Density-Sensitive Lines in the EUV Region. Authors: Vernazza, J. E.; Mason, H. E. Bibcode: 1977uxsa.coll...15V Altcode: 1977IAUCo..43...15V No abstract at ADS Title: The interpretation of the forbidden emission lines from a coronal condensation. Authors: Mason, H. E. Bibcode: 1975MNRAS.171..119M Altcode: Theoretical emission rates have recently been computed (Mason) for six lines observed in the visible spectrum of the solar corona. These rates are used to analyse the spectra of a coronal condensation observed by Lyot and Aly at the 1952 eclipse (Aly et al.). Average electron density and temperature conditions for the condensation are deduced and a specific model is proposed, in which electron density and temperature estimates are defined as a function of position within the condensation. Since continuum measurements were also recorded, abundance estimates for iron and calcium relative to hydrogen are obtained. The structure of the model is seen to be consistent with other solar observation. Title: The excitation of several iron and calcium lines in the visible spectrum of the solar corona. Authors: Mason, H. E. Bibcode: 1975MNRAS.170..651M Altcode: New atomic data have been obtained for the coronal ions Fe X, Fe XI, Fe XIV, Ca XII, Ca XIII and Ca XV, using a computer. Energy levels and radiative transition probabilities have been computed allowing for configuration interaction and relativistic effects. The electron scattering problem has been solved using the distorted wave approach. All radiative and collisional processes contributing to the equilibrium equations for the ground configuration were considered, including cascade via the excited configurations and the effect of autoionizing levels on the electron collisional excitation rate. Wherever possible, the accuracy of the atomic parameters has been estimated and the results compared to those of previous authors. The atomic data, level populations and emission rates for the ions studied, are tabulated for various physical conditions appropriate to the solar corona. Title: The interpretation of the forbidden emission lines from a coronal condensation Authors: Mason, Helen Elizabeth Bibcode: 1974PhDT.......256M Altcode: No abstract at ADS Title: Spectrographic Examination of Chromatographic Columns Authors: Dunabin, J. E.; Mason, H.; Seyfang, A. P.; Woodman, F. J. Bibcode: 1949Natur.164..916D Altcode: IN the determination of metallic traces, insufficient attention has been paid either to the advantages of direct spectrography of chromatographic columns, or to the chromatographic behaviour of organic metal complexes, although in the latter sphere the use of oxine1 and of violuric acid2 has been reported.