Author name code: buchlin ADS astronomy entries on 2022-09-14 author:"Buchlin, Eric" ------------------------------------------------------------------------ Title: What drives decayless kink oscillations in active region coronal loops on the Sun? Authors: Mandal, Sudip; Chitta, Lakshmi P.; Antolin, Patrick; Peter, Hardi; Solanki, Sami K.; Auchère, Frédéric; Berghmans, David; Zhukov, Andrei N.; Teriaca, Luca; Cuadrado, Regina A.; Schühle, Udo; Parenti, Susanna; Buchlin, Éric; Harra, Louise; Verbeeck, Cis; Kraaikamp, Emil; Long, David M.; Rodriguez, Luciano; Pelouze, Gabriel; Schwanitz, Conrad; Barczynski, Krzysztof; Smith, Phil J. Bibcode: 2022arXiv220904251M Altcode: We study here the phenomena of decayless kink oscillations in a system of active region (AR) coronal loops. Using high resolution observations from two different instruments, namely the Extreme Ultraviolet Imager (EUI) on board Solar Orbiter and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory, we follow these AR loops for an hour each on three consecutive days. Our results show significantly more resolved decayless waves in the higher-resolution EUI data compared with the AIA data. Furthermore, the same system of loops exhibits many of these decayless oscillations on Day-2, while on Day-3, we detect very few oscillations and on Day-1, we find none at all. Analysis of photospheric magnetic field data reveals that at most times, these loops were rooted in sunspots, where supergranular flows are generally absent. This suggests that supergranular flows, which are often invoked as drivers of decayless waves, are not necessarily driving such oscillations in our observations. Similarly, our findings also cast doubt on other possible drivers of these waves, such as a transient driver or mode conversion of longitudinal waves near the loop footpoints. In conclusion, through our analysis we find that none of the commonly suspected sources proposed to drive decayless oscillations in active region loops seems to be operating in this event and hence, the search for that elusive wave driver needs to continue. Title: FIP fractionation in the turbulent solar chromosphere and corona: incompressible and compressible models Authors: Reville, Victor; Buchlin, Eric; Verdini, Andrea; Rouillard, Alexis; Velli, Marco; Lavarra, Michael; Poirier, Nicolas Bibcode: 2022cosp...44.2576R Altcode: Low first ionisation potential (FIP) elements show enriched abundances in the slow solar wind and coronal loops compared to photospheric values. Turbulence is likely to be a key physical mechanism to explain these abundances. Turbulent mixing is indeed essential to prevent gravitational settling of heavy elements. Moreover, the average turbulent Lorentz force, the ponderomotive force, could explain the preferential lifting of low FIP ions in the upper chromosphere and transition region. In this talk, we use unidimensional models of the solar atmosphere, to compute the turbulent properties around the transition regions in several regimes. We use the incompressible (or reduced) MHD formalism with the SHELL-ATM code, and show that the turbulent field is consistent with both coronal heating and significant FIP fractionation. Then, we use the compressible MHD code PLUTO, and compare the turbulent properties of the two models. In particular, we look at the effect of chromospheric shocks on the propagation of Alfvén waves near the top of the chromosphere that may act to modify wave properties in the ionisation region of heavy elements. This work has been funded by the ERC project SLOW SOURCE - DLV-819189 Title: Elemental composition diagnostics for Hinode/EIS Authors: Zambrana Prado, Natalia; Buchlin, Eric; Pelouze, Gabriel; Young, Peter Bibcode: 2022cosp...44.2581Z Altcode: In order to explore the connection between the solar atmosphere and the solar wind, it is helpful to look at the elemental abundances for they carry evidence of the origin region of the escaping plasma. This is due to the first ionization potential (FIP) effect which results in an enhancement of the abundances of low FIP elements. To provide composition maps, we developed the Linear Combination Ratio (or LCR) method which allows for relative abundance measurements forgoing the need of differential emission measure inversion. This method has been thoroughly tested on synthetic spectra and on spectroscopic data. The proof of concept for the LCR method was published in Zambrana Prado and Buchlin [2019], in that paper we focused on measuring the FIP bias between sulfur and a mixture of iron and silicon. In this paper we consider the most commonly-used EIS studies and identify element pairs that can be used as diagnostics of the FIP effect. We apply the LCR method and obtain FIP bias measurements in sample datasets. This demonstrates that a large portion of the EIS archive can be used for abundance diagnostics, and the LCR method opens the possibility of deriving abundance ratio maps semi-automatically leading to new data products for the community. We developed the LCR method further by designing a numerical procedure based on a statistical approach and the Bayes theorem to compute uncertainties of these FIP bias diagnostics. It can take into account uncertainties in the atomic physics and in the instrument calibration. It provides the probability distribution of the real FIP bias of the plasma given the measurement provided by the LCR method. Hinode has been coordinating with other resources such as ALMA, PSP, Solar Orbiter, and DKIST, just to name a few. These new diagnostics come as an add-on to our tool-belt, opening the possibility to see through an additional perspective over a decade and a half of coronal spectra. Title: Forecasting the Kp index a few days ahead using solar imaging and neural networks alone: is it achievable? Authors: Bernoux, Guillerme; Sicard, Angelica; Buchlin, Eric; Janvier, Miho; Brunet, Antoine Bibcode: 2022cosp...44.3330B Altcode: Over the past decade, data-driven methods using near-Earth solar wind parameters to forecast geomagnetic indices have shown very good performance, mostly outperforming many empirical and physics-based models in terms of accuracy. In addition, these forecasting models have recently shown their relevance to drive various magnetospheric models in space weather pipelines. However, these methods still suffer from many limitations, among which their restriction to a short effective forecasting horizon (often up to approximately 6 hours at best). This is not surprising, as these lead-times are of the same order of magnitude as the solar wind-magnetosphere coupling time-lags. Therefore, in order to increase the forecasting horizon, one solution would be to use more spatially remote data, such as solar imaging. In order to address this issue, we introduce SERENADE, a deep learning-based model driven only by Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) data that can provide probabilistic forecasts of geomagnetic indices such as Kp up to a few days ahead. We evaluate the model and discuss its advantages and drawbacks based on these first results. In particular, we compare it with baseline models and assess the performance of our model according to the solar cycle phase. We show that our method is promising, especially since it is only a first model that can be improved in many aspects. Title: Automatic detection of small-scale EUV brightenings observed by the Solar Orbiter/EUI Authors: Alipour, N.; Safari, H.; Verbeeck, C.; Berghmans, D.; Auchère, F.; Chitta, L. P.; Antolin, P.; Barczynski, K.; Buchlin, É.; Aznar Cuadrado, R.; Dolla, L.; Georgoulis, M. K.; Gissot, S.; Harra, L.; Katsiyannis, A. C.; Long, D. M.; Mandal, S.; Parenti, S.; Podladchikova, O.; Petrova, E.; Soubrié, É.; Schühle, U.; Schwanitz, C.; Teriaca, L.; West, M. J.; Zhukov, A. N. Bibcode: 2022A&A...663A.128A Altcode: 2022arXiv220404027A Context. Accurate detections of frequent small-scale extreme ultraviolet (EUV) brightenings are essential to the investigation of the physical processes heating the corona.
Aims: We detected small-scale brightenings, termed campfires, using their morphological and intensity structures as observed in coronal EUV imaging observations for statistical analysis.
Methods: We applied a method based on Zernike moments and a support vector machine (SVM) classifier to automatically identify and track campfires observed by Solar Orbiter/Extreme Ultraviolet Imager (EUI) and Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA).
Results: This method detected 8678 campfires (with length scales between 400 km and 4000 km) from a sequence of 50 High Resolution EUV telescope (HRIEUV) 174 Å images. From 21 near co-temporal AIA images covering the same field of view as EUI, we found 1131 campfires, 58% of which were also detected in HRIEUV images. In contrast, about 16% of campfires recognized in HRIEUV were detected by AIA. We obtain a campfire birthrate of 2 × 10−16 m−2 s−1. About 40% of campfires show a duration longer than 5 s, having been observed in at least two HRIEUV images. We find that 27% of campfires were found in coronal bright points and the remaining 73% have occurred out of coronal bright points. We detected 23 EUI campfires with a duration greater than 245 s. We found that about 80% of campfires are formed at supergranular boundaries, and the features with the highest total intensities are generated at network junctions and intense H I Lyman-α emission regions observed by EUI/HRILya. The probability distribution functions for the total intensity, peak intensity, and projected area of campfires follow a power law behavior with absolute indices between 2 and 3. This self-similar behavior is a possible signature of self-organization, or even self-organized criticality, in the campfire formation process.

Supplementary material (S1-S3) is available at https://www.aanda.org Title: Simulating the FIP effect in coronal loops using a multi-species kinetic-fluid model. Authors: Poirier, Nicolas; Buchlin, Eric; Verdini, Andrea; Rouillard, Alexis; Velli, Marco; Reville, Victor; Lavarra, Michael; Blelly, Pierre-Louis; Indurain, Mikel Bibcode: 2022cosp...44.2577P Altcode: We investigate abundance variations of heavy ions in coronal loops. We develop and exploit a multi-species model of the solar atmosphere (called IRAP's Solar Atmospheric Model: ISAM) that solves for the transport of neutral and charged particles from the chromosphere to the corona. We investigate the effect of different mechanisms that could produce the First Ionization Potential (FIP) effect. We compare the effects of the thermal, friction and ponderomotive force. The propagation, reflection and dissipation of Alfvén waves is solved using two distinct models, the first one from Chandran et al. (2011) and the second one that is a more sophisticated turbulence model called Shell-ATM. ISAM solves a set of 16-moment transport equations for both neutrals and charged particles with a comprehensive treatment of particle interactions and ionization/recombination processes. Protons and electrons are heated by Alfvén waves, which then heat up the heavy ions via collision processes. We show comparisons of our results with other models and observations, with an emphasis on FIP biases. This work was funded by the European Research Council through the project SLOW SOURCE - DLV-819189. Title: Abundance diagnostics in active regions with Solar Orbiter/SPICE Authors: Giunta, Alessandra; Peter, Hardi; Parenti, Susanna; Buchlin, Eric; Thompson, William; Auchere, Frederic; Kucera, Therese; Carlsson, Mats; Janvier, Miho; Fludra, Andrzej; Hassler, Donald M.; Grundy, Timothy; Sidher, Sunil; Guest, Steve; Leeks, Sarah; Fredvik, Terje; Young, Peter Bibcode: 2022cosp...44.2583G Altcode: With the launch of Solar Orbiter in February 2020, we are now able to fully explore the link between the solar activity on the Sun and the inner heliosphere. Elemental abundance measurements provide a key tracer to probe the source regions of the solar wind and to track it from the solar surface and corona to the heliosphere. Abundances of elements with low first ionisation potential (FIP) are enhanced in the corona relative to high-FIP elements, with respect to the photosphere. This is known as the FIP effect, which is measured as abundance bias (FIP bias) of low and high FIP elements. This effect is vital for understanding the flow of mass and energy through the solar atmosphere. The comparison between in-situ and remote sensing composition data, coupled with modelling, will allow us to trace back the source of heliospheric plasma. Solar Orbiter has a unique combination of in-situ and remote sensing instruments that will help to make such a comparison. In particular, the SPICE (Spectral Imaging of the Coronal Environment) EUV spectrometer records spectra in two wavelength bands, 70.4-79.0 nm and 97.3-104.9 nm. SPICE is designed to provide spectroheliograms using a core set of emission lines arising from ions of both low-FIP and high-FIP elements such as C, N, O, Ne, Mg, S and Fe. These lines are formed over a wide range of temperatures from 20,000 K to over 1 million K, enabling the analysis of the different layers of the solar atmosphere. SPICE spectroheliograms can be processed to produce FIP bias maps, which can be compared to in-situ measurements of the solar wind composition of the same elements. During the Solar Orbiter Cruise Phase, SPICE observed several active regions. We will present some of these observations and discuss the SPICE diagnostic potential to derive relative abundances (e.g., Mg/Ne) and the FIP bias in those regions. Title: The SPICE spectrograph on Solar Orbiter: an introduction and results from the first Orbits Authors: Auchère, Frédéric; Peter, Hardi; Parenti, Susanna; Buchlin, Eric; Thompson, William; Auchere, Frederic; Teriaca, Luca; Kucera, Therese; Carlsson, Mats; Janvier, Miho; Fludra, Andrzej; Giunta, Alessandra; Schuehle, Udo; Hassler, Donald M.; Grundy, Timothy; Sidher, Sunil; Fredvik, Terje; Plowman, Joseph; Aznar Cuadrado, Regina Bibcode: 2022cosp...44.1338A Altcode: The Spectral Imaging of the Coronal Environment (SPICE) instrument is the EUV imaging spectrometer on board the Solar Orbiter mission. With its ability to derive physical properties of the coronal plasma, SPICE is a key component of the payload to establish the connection between the source regions and the in-situ measurements of the solar wind. The spacecraft was successfully launched in February 2020 and completed its cruise phase in December 2021. During this period, the remote sensing instruments were mostly operated during limited periods of time for 'checkout' engineering activities and synoptic observations. Nonetheless, several of these periods provided enough opportunities already to obtain new insights on coronal physics. During the march 2022 perihelion - close to 0.3 AU - SPICE will provide its highest spatial resolution data so far. Coordinated observations between the remote sensing and in-situ instruments will provide the first opportunity to use the full potential of the Solar Orbiter mission. We will review the instrument characteristics and present initial results from the cruise phase and first close encounter. Title: Validation of a Wave Heated 3D MHD Coronal-wind Model using Polarized Brightness and EUV Observations Authors: Parenti, Susanna; Réville, Victor; Brun, Allan Sacha; Pinto, Rui F.; Auchère, Frédéric; Buchlin, Éric; Perri, Barbara; Strugarek, Antoine Bibcode: 2022ApJ...929...75P Altcode: 2022arXiv220310876P The physical properties responsible for the formation and evolution of the corona and heliosphere are still not completely understood. 3D MHD global modeling is a powerful tool to investigate all the possible candidate processes. To fully understand the role of each of them, we need a validation process where the output from the simulations is quantitatively compared to the observational data. In this work, we present the results from our validation process applied to the wave turbulence driven 3D MHD corona-wind model WindPredict-AW. At this stage of the model development, we focus the work to the coronal regime in quiescent condition. We analyze three simulation results, which differ by the boundary values. We use the 3D distributions of density and temperature, output from the simulations at the time of around the first Parker Solar Probe perihelion (during minimum of the solar activity), to synthesize both extreme ultraviolet (EUV) and white-light-polarized (WL pB) images to reproduce the observed solar corona. For these tests, we selected AIA 193 Å, 211 Å, and 171 Å EUV emissions, MLSO K-Cor, and LASCO C2 pB images obtained on 2018 November 6 and 7. We then make quantitative comparisons of the disk and off limb corona. We show that our model is able to produce synthetic images comparable to those of the observed corona. Title: Stereoscopy of extreme UV quiet Sun brightenings observed by Solar Orbiter/EUI Authors: Zhukov, A. N.; Mierla, M.; Auchère, F.; Gissot, S.; Rodriguez, L.; Soubrié, E.; Thompson, W. T.; Inhester, B.; Nicula, B.; Antolin, P.; Parenti, S.; Buchlin, É.; Barczynski, K.; Verbeeck, C.; Kraaikamp, E.; Smith, P. J.; Stegen, K.; Dolla, L.; Harra, L.; Long, D. M.; Schühle, U.; Podladchikova, O.; Aznar Cuadrado, R.; Teriaca, L.; Haberreiter, M.; Katsiyannis, A. C.; Rochus, P.; Halain, J. -P.; Jacques, L.; Berghmans, D. Bibcode: 2021A&A...656A..35Z Altcode: 2021arXiv210902169Z Context. The three-dimensional fine structure of the solar atmosphere is still not fully understood as most of the available observations are taken from a single vantage point.
Aims: The goal of the paper is to study the three-dimensional distribution of the small-scale brightening events ("campfires") discovered in the extreme-UV quiet Sun by the Extreme Ultraviolet Imager (EUI) aboard Solar Orbiter.
Methods: We used a first commissioning data set acquired by the EUI's High Resolution EUV telescope on 30 May 2020 in the 174 Å passband and we combined it with simultaneous data taken by the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory in a similar 171 Å passband. The two-pixel spatial resolution of the two telescopes is 400 km and 880 km, respectively, which is sufficient to identify the campfires in both data sets. The two spacecraft had an angular separation of around 31.5° (essentially in heliographic longitude), which allowed for the three-dimensional reconstruction of the campfire position. These observations represent the first time that stereoscopy was achieved for brightenings at such a small scale. Manual and automatic triangulation methods were used to characterize the campfire data.
Results: The height of the campfires is located between 1000 km and 5000 km above the photosphere and we find a good agreement between the manual and automatic methods. The internal structure of campfires is mostly unresolved by AIA; however, for a particularly large campfire, we were able to triangulate a few pixels, which are all in a narrow range between 2500 and 4500 km.
Conclusions: We conclude that the low height of EUI campfires suggests that they belong to the previously unresolved fine structure of the transition region and low corona of the quiet Sun. They are probably apexes of small-scale dynamic loops heated internally to coronal temperatures. This work demonstrates that high-resolution stereoscopy of structures in the solar atmosphere has become feasible. Title: Full Vector Velocity Reconstruction Using Solar Orbiter Doppler Map Observations. Authors: Podladchikova, Olena; Harra, Louise; Barczynski, Krzysztof; Mandrini, Cristina; Auchere, F.; Berghmans, David; Buchlin, Eric; Dolla, Laurent; Mierla, Marilena; Parenti, Susanna; Rodriguez, Luciano Bibcode: 2021AGUFMNG35B0432P Altcode: The Solar Orbiter mission opens up opportunities forthe combined analysis of measurements obtained by solar imagers and spectrometers. For the first time, different space spectrometerswill be located at wide angles to each other, allowing three-dimensional (3D) spectroscopy of the solar atmosphere.The aim of this work is to prepare the methodology to facilitate the reconstruction of 3D vector velocities from two stereoscopicLOS Doppler velocity measurements using the Spectral Imaging of the Coronal Environment (SPICE) on board the Solar Orbiter andthe near-Earth spectrometers, while widely separated in space. We develop the methodology using the libraries designed earlier for the STEREO mission but applied to spectroscopicdata from the Hinode mission and the Solar Dynamics Observatory. We use well-known methods of static and dynamic solar rotationstereoscopy and the methods of EUV stereoscopic triangulation for optically-thin coronal EUV plasma emissions. We develop new algorithms using analytical geometry in space to determine the 3D velocity in coronal loops. We demonstrate our approach with the reconstruction of 3D velocity vectors in plasma flows along "open" and "closed"magnetic loops. This technique will be applied first to an actual situation of two spacecraft at different separations with spectrometers onboard (SPICE versus the Interface Region Imaging Spectrograph (IRIS) and Hinode imaging spectrometer) during the Solar Orbiternominal phase. We summarise how these observations can be coordinated. Title: Stereoscopy of extreme UV quiet Sun brightenings observed by Solar Orbiter/EUI Authors: Zhukov, Andrei; Mierla, Marilena; Auchere, F.; Gissot, Samuel; Rodriguez, Luciano; Soubrie, Elie; Thompson, William; Inhester, Bernd; Nicula, Bogdan; Antolin, Patrick; Parenti, Susanna; Buchlin, Eric; Barczynski, Krzysztof; Verbeeck, Cis; Kraaikamp, Emil; Smith, Philip; Stegen, Koen; Dolla, Laurent; Harra, Louise; Long, David; Schuhle, Udo; Podladchikova, Olena; Aznar Cuadrado, Regina; Teriaca, Luca; Haberreiter, Margit; Katsiyannis, Athanassios; Rochus, Pierre; Halain, Jean-Philippe; Jacques, Lionel; Berghmans, David Bibcode: 2021AGUFMSH21A..03Z Altcode: We study the three-dimensional distribution of small-scale brightening events (campfires) discovered in the extreme-ultraviolet (EUV) quiet Sun by the EUI telescope onboard the Solar Orbiter mission. We use one of the first commissioning data sets acquired by the HRI_EUV telescope of EUI on 2020 May 30 in the 174 A passband, combined with the simultaneous SDO/AIA dataset taken in the very similar 171 A passband. The spatial resolution of the two telescopes is sufficient to identify the campfires in both datasets. The angular separation between the two spacecraft of around 31.5 degrees allowed for the three-dimensional reconstruction of the position of campfires. This is the first time that stereoscopy was achieved for structures at such a small scale. Manual and automatic triangulation methods were used. The height of campfires is between 1000 km and 5000 km above the photosphere, and there is a good agreement between the results of manual and automatic methods. The internal structure of campfires is mostly not resolved by AIA, but for a large campfire we could triangulate a few pixels, which are all in a narrow height range between 2500 and 4500 km. The low height of campfires suggests that they belong to the previously unresolved fine structure of the transition region and low corona of the quiet Sun. They are probably apexes of small-scale dynamic loops internally heated to coronal temperatures. This work demonstrates that high-resolution stereoscopy of structures in the solar atmosphere has become possible. Title: Extreme-UV quiet Sun brightenings observed by the Solar Orbiter/EUI Authors: Berghmans, D.; Auchère, F.; Long, D. M.; Soubrié, E.; Mierla, M.; Zhukov, A. N.; Schühle, U.; Antolin, P.; Harra, L.; Parenti, S.; Podladchikova, O.; Aznar Cuadrado, R.; Buchlin, É.; Dolla, L.; Verbeeck, C.; Gissot, S.; Teriaca, L.; Haberreiter, M.; Katsiyannis, A. C.; Rodriguez, L.; Kraaikamp, E.; Smith, P. J.; Stegen, K.; Rochus, P.; Halain, J. P.; Jacques, L.; Thompson, W. T.; Inhester, B. Bibcode: 2021A&A...656L...4B Altcode: 2021arXiv210403382B Context. The heating of the solar corona by small heating events requires an increasing number of such events at progressively smaller scales, with the bulk of the heating occurring at scales that are currently unresolved.
Aims: The goal of this work is to study the smallest brightening events observed in the extreme-UV quiet Sun.
Methods: We used commissioning data taken by the Extreme Ultraviolet Imager (EUI) on board the recently launched Solar Orbiter mission. On 30 May 2020, the EUI was situated at 0.556 AU from the Sun. Its High Resolution EUV telescope (HRIEUV, 17.4 nm passband) reached an exceptionally high two-pixel spatial resolution of 400 km. The size and duration of small-scale structures was determined by the HRIEUV data, while their height was estimated from triangulation with simultaneous images from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory mission. This is the first stereoscopy of small-scale brightenings at high resolution.
Results: We observed small localised brightenings, also known as `campfires', in a quiet Sun region with length scales between 400 km and 4000 km and durations between 10 s and 200 s. The smallest and weakest of these HRIEUV brightenings have not been previously observed. Simultaneous observations from the EUI High-resolution Lyman-α telescope (HRILya) do not show localised brightening events, but the locations of the HRIEUV events clearly correspond to the chromospheric network. Comparisons with simultaneous AIA images shows that most events can also be identified in the 17.1 nm, 19.3 nm, 21.1 nm, and 30.4 nm pass-bands of AIA, although they appear weaker and blurred. Our differential emission measure analysis indicated coronal temperatures peaking at log T ≈ 6.1 − 6.15. We determined the height for a few of these campfires to be between 1000 and 5000 km above the photosphere.
Conclusions: We find that `campfires' are mostly coronal in nature and rooted in the magnetic flux concentrations of the chromospheric network. We interpret these events as a new extension to the flare-microflare-nanoflare family. Given their low height, the EUI `campfires' could stand as a new element of the fine structure of the transition region-low corona, that is, as apexes of small-scale loops that undergo internal heating all the way up to coronal temperatures. Title: First observations from the SPICE EUV spectrometer on Solar Orbiter Authors: Fludra, A.; Caldwell, M.; Giunta, A.; Grundy, T.; Guest, S.; Leeks, S.; Sidher, S.; Auchère, F.; Carlsson, M.; Hassler, D.; Peter, H.; Aznar Cuadrado, R.; Buchlin, É.; Caminade, S.; DeForest, C.; Fredvik, T.; Haberreiter, M.; Harra, L.; Janvier, M.; Kucera, T.; Müller, D.; Parenti, S.; Schmutz, W.; Schühle, U.; Solanki, S. K.; Teriaca, L.; Thompson, W. T.; Tustain, S.; Williams, D.; Young, P. R.; Chitta, L. P. Bibcode: 2021A&A...656A..38F Altcode: 2021arXiv211011252F
Aims: We present first science observations taken during the commissioning activities of the Spectral Imaging of the Coronal Environment (SPICE) instrument on the ESA/NASA Solar Orbiter mission. SPICE is a high-resolution imaging spectrometer operating at extreme ultraviolet (EUV) wavelengths. In this paper we illustrate the possible types of observations to give prospective users a better understanding of the science capabilities of SPICE.
Methods: We have reviewed the data obtained by SPICE between April and June 2020 and selected representative results obtained with different slits and a range of exposure times between 5 s and 180 s. Standard instrumental corrections have been applied to the raw data.
Results: The paper discusses the first observations of the Sun on different targets and presents an example of the full spectra from the quiet Sun, identifying over 40 spectral lines from neutral hydrogen and ions of carbon, oxygen, nitrogen, neon, sulphur, magnesium, and iron. These lines cover the temperature range between 20 000 K and 1 million K (10 MK in flares), providing slices of the Sun's atmosphere in narrow temperature intervals. We provide a list of count rates for the 23 brightest spectral lines. We show examples of raster images of the quiet Sun in several strong transition region lines, where we have found unusually bright, compact structures in the quiet Sun network, with extreme intensities up to 25 times greater than the average intensity across the image. The lifetimes of these structures can exceed 2.5 hours. We identify them as a transition region signature of coronal bright points and compare their areas and intensity enhancements. We also show the first above-limb measurements with SPICE above the polar limb in C III, O VI, and Ne VIII lines, and far off limb measurements in the equatorial plane in Mg IX, Ne VIII, and O VI lines. We discuss the potential to use abundance diagnostics methods to study the variability of the elemental composition that can be compared with in situ measurements to help confirm the magnetic connection between the spacecraft location and the Sun's surface, and locate the sources of the solar wind.
Conclusions: The SPICE instrument successfully performs measurements of EUV spectra and raster images that will make vital contributions to the scientific success of the Solar Orbiter mission. Title: An operational approach to forecast the Earth's radiation belts dynamics Authors: Bernoux, Guillerme; Brunet, Antoine; Buchlin, Éric; Janvier, Miho; Sicard, Angélica Bibcode: 2021JSWSC..11...60B Altcode: The Ca index is a time-integrated geomagnetic index that correlates well with the dynamics of high-energy electron fluxes in the outer radiation belts. Therefore, Ca can be used as an indicator for the state of filling of the radiation belts for those electrons. Ca also has the advantage of being a ground-based measurement with extensive historical records. In this work, we propose a data-driven model to forecast Ca up to 24 h in advance from near-Earth solar wind parameters. Our model relies mainly on a recurrent neural network architecture called Long Short Term Memory that has shown good performances in forecasting other geomagnetic indices in previous papers. Most implementation choices in this study were arbitrated from the point of view of a space system operator, including the data selection and split, the definition of a binary classification threshold, and the evaluation methodology. We evaluate our model (against a linear baseline) using both classical and novel (in the space weather field) measures. In particular, we use the Temporal Distortion Mix (TDM) to assess the propensity of two time series to exhibit time lags. We also evaluate the ability of our model to detect storm onsets during quiet periods. It is shown that our model has high overall accuracy, with evaluation measures deteriorating in a smooth and slow trend over time. However, using the TDM and binary classification forecast evaluation metrics, we show that the forecasts lose some of their usefulness in an operational context even for time horizons shorter than 6 h. This behaviour was not observable when evaluating the model only with metrics such as the root-mean-square error or the Pearson linear correlation. Considering the physics of the problem, this result is not surprising and suggests that the use of more spatially remote data (such as solar imaging) could improve space weather forecasts. Title: Stereoscopic measurements of coronal Doppler velocities Authors: Podladchikova, O.; Harra, L.; Barczynski, K.; Mandrini, C. H.; Auchère, F.; Berghmans, D.; Buchlin, É.; Dolla, L.; Mierla, M.; Parenti, S.; Rodriguez, L. Bibcode: 2021A&A...655A..57P Altcode: 2021arXiv210802280P Context. The Solar Orbiter mission, with an orbit outside the Sun-Earth line and leaving the ecliptic plane, opens up opportunities for the combined analysis of measurements obtained by solar imagers and spectrometers. For the first time different space spectrometers will be located at wide angles to each other, allowing three-dimensional (3D) spectroscopy of the solar atmosphere.
Aims: The aim of this work is to prepare a methodology to facilitate the reconstruction of 3D vector velocities from two stereoscopic line of sight (LOS) Doppler velocity measurements using the Spectral Imaging of the Coronal Environment (SPICE) on board the Solar Orbiter and the near-Earth spectrometers, while widely separated in space.
Methods: We developed the methodology using the libraries designed earlier for the STEREO mission, but applied to spectroscopic data from the Hinode mission and the Solar Dynamics Observatory. We used well-known methods of static and dynamic solar rotation stereoscopy and the methods of extreme ultraviolet (EUV) stereoscopic triangulation for optically thin coronal EUV plasma emissions. We developed new algorithms using analytical geometry in space to determine the 3D velocity in coronal loops.
Results: We demonstrate our approach with the reconstruction of 3D velocity vectors in plasma flows along `open' and `closed' magnetic loops. This technique will be applied to an actual situation of two spacecraft at different separations with spectrometers on board during the Solar Orbiter nominal phase: SPICE versus the Interface Region Imaging Spectrograph (IRIS) and Hinode imaging spectrometer. We summarise how these observations can be coordinated.

Movies associated to Fig. 1 are available at https://www.aanda.org Title: Magnetic imaging of the outer solar atmosphere (MImOSA) Authors: Peter, H.; Ballester, E. Alsina; Andretta, V.; Auchère, F.; Belluzzi, L.; Bemporad, A.; Berghmans, D.; Buchlin, E.; Calcines, A.; Chitta, L. P.; Dalmasse, K.; Alemán, T. del Pino; Feller, A.; Froment, C.; Harrison, R.; Janvier, M.; Matthews, S.; Parenti, S.; Przybylski, D.; Solanki, S. K.; Štěpán, J.; Teriaca, L.; Bueno, J. Trujillo Bibcode: 2021ExA...tmp...95P Altcode: The magnetic activity of the Sun directly impacts the Earth and human life. Likewise, other stars will have an impact on the habitability of planets orbiting these host stars. Although the magnetic field at the surface of the Sun is reasonably well characterised by observations, the information on the magnetic field in the higher atmospheric layers is mainly indirect. This lack of information hampers our progress in understanding solar magnetic activity. Overcoming this limitation would allow us to address four paramount long-standing questions: (1) How does the magnetic field couple the different layers of the atmosphere, and how does it transport energy? (2) How does the magnetic field structure, drive and interact with the plasma in the chromosphere and upper atmosphere? (3) How does the magnetic field destabilise the outer solar atmosphere and thus affect the interplanetary environment? (4) How do magnetic processes accelerate particles to high energies? New ground-breaking observations are needed to address these science questions. We suggest a suite of three instruments that far exceed current capabilities in terms of spatial resolution, light-gathering power, and polarimetric performance: (a) A large-aperture UV-to-IR telescope of the 1-3 m class aimed mainly to measure the magnetic field in the chromosphere by combining high spatial resolution and high sensitivity. (b) An extreme-UV-to-IR coronagraph that is designed to measure the large-scale magnetic field in the corona with an aperture of about 40 cm. (c) An extreme-UV imaging polarimeter based on a 30 cm telescope that combines high throughput in the extreme UV with polarimetry to connect the magnetic measurements of the other two instruments. Placed in a near-Earth orbit, the data downlink would be maximised, while a location at L4 or L5 would provide stereoscopic observations of the Sun in combination with Earth-based observatories. This mission to measure the magnetic field will finally unlock the driver of the dynamics in the outer solar atmosphere and thereby will greatly advance our understanding of the Sun and the heliosphere. Title: Vector Velocities Measurements with the Solar Orbiter SPICE Spectrometer Authors: Podladchikova, O.; Harra, L.; Barczynski, K.; Mandrini, C.; Auchère, F.; Berghmans, D.; Buchlin, E.; Dolla, L.; Mierla, M.; Parenti, S.; Rodriguez, L. Bibcode: 2021AAS...23831312P Altcode: The Solar Orbiter mission, with an orbit outside the Sun-Earth line and leaving the ecliptic plane, opens up opportunities for the combined analysis of measurements obtained by solar imagers and spectrometers. For the first time, different spectrometers will be located at wide angles to each other, allowing three-dimensional (3D) spectroscopy of the solar atmosphere. Here we develop a methodology to prepare for this kind of analysis, by using data from the Hinode mission and the Solar Dynamics Observatory, respectively. We employ solar rotation to simulate measurements of spectrometers with different views of the solar corona. The resulting data allow us to apply stereoscopic tie-pointing and triangulation techniques designed for the STEREO spacecraft pair, and to perform 3D analysis of the Doppler shifts of a quasi-stationary active region. Our approach allows the accurate reconstruction of 3D velocity vectors in plasma flows along "open" and "closed" magnetic loops. This technique will be applied to the actual situation of two spacecraft at different separations with spectrometers on board (the Solar Orbiter Spectral Imaging of the Coronal Environment versus the Interface Region Imaging Spectrograph (IRIS) and Hinode imaging spectrometer) and we summarise how these observations can be coordinated to assess vector velocity measurements. This 3D spectroscopy method will facilitate the understanding of the complex flows that take place throughout the solar atmosphere. Title: The flare likelihood and region eruption forecasting (FLARECAST) project: flare forecasting in the big data & machine learning era Authors: Georgoulis, Manolis K.; Bloomfield, D. Shaun; Piana, Michele; Massone, Anna Maria; Soldati, Marco; Gallagher, Peter T.; Pariat, Etienne; Vilmer, Nicole; Buchlin, Eric; Baudin, Frederic; Csillaghy, Andre; Sathiapal, Hanna; Jackson, David R.; Alingery, Pablo; Benvenuto, Federico; Campi, Cristina; Florios, Konstantinos; Gontikakis, Constantinos; Guennou, Chloe; Guerra, Jordan A.; Kontogiannis, Ioannis; Latorre, Vittorio; Murray, Sophie A.; Park, Sung-Hong; von Stachelski, Samuelvon; Torbica, Aleksandar; Vischi, Dario; Worsfold, Mark Bibcode: 2021JSWSC..11...39G Altcode: 2021arXiv210505993G The European Union funded the FLARECAST project, that ran from January 2015 until February 2018. FLARECAST had a research-to-operations (R2O) focus, and accordingly introduced several innovations into the discipline of solar flare forecasting. FLARECAST innovations were: first, the treatment of hundreds of physical properties viewed as promising flare predictors on equal footing, extending multiple previous works; second, the use of fourteen (14) different machine learning techniques, also on equal footing, to optimize the immense Big Data parameter space created by these many predictors; third, the establishment of a robust, three-pronged communication effort oriented toward policy makers, space-weather stakeholders and the wider public. FLARECAST pledged to make all its data, codes and infrastructure openly available worldwide. The combined use of 170+ properties (a total of 209 predictors are now available) in multiple machine-learning algorithms, some of which were designed exclusively for the project, gave rise to changing sets of best-performing predictors for the forecasting of different flaring levels, at least for major flares. At the same time, FLARECAST reaffirmed the importance of rigorous training and testing practices to avoid overly optimistic pre-operational prediction performance. In addition, the project has (a) tested new and revisited physically intuitive flare predictors and (b) provided meaningful clues toward the transition from flares to eruptive flares, namely, events associated with coronal mass ejections (CMEs). These leads, along with the FLARECAST data, algorithms and infrastructure, could help facilitate integrated space-weather forecasting efforts that take steps to avoid effort duplication. In spite of being one of the most intensive and systematic flare forecasting efforts to-date, FLARECAST has not managed to convincingly lift the barrier of stochasticity in solar flare occurrence and forecasting: solar flare prediction thus remains inherently probabilistic. Title: First data for abundance diagnostics with SPICE, the EUV spectrometer on-board Solar Orbiter Authors: Zambrana Prado, Natalia; Buchlin, Éric; Peter, Hardi Bibcode: 2021EGUGA..2315555Z Altcode: Linking solar activity on the surface and in the corona to the heliosphere is one of Solar Orbiter"s main goals. Its EUV spectrometer SPICE (SPectral Imaging of the Coronal Environment) will provide relative abundance measurements which will be key in this quest, as different structures on the Sun have different abundances as a consequence of the FIP (First Ionization Potential) effect. From the 16th to the 22nd of November 2020, the Solar Orbiter remote sensing checkout window STP-122 was carried out. During this period of observations, SPICE was lucky to catch a small AR in its field of view. We carried out abundance specific observations in order to provide relative FIP bias measurements with SPICE. Furthermore, data from other types of observations carried out during that same week allow us to identify the spectral lines that could be used for abundance diagnostics. We take the SPICE instrument characteristics into account to give recommendations regarding the types of studies to carry out to obtain such abundance measurements. Title: Modeling Solar Wind Variations over an 11 Year Cycle with Alfvén Wave Dissipation: A Parameter Study Authors: Hazra, Soumitra; Réville, Victor; Perri, Barbara; Strugarek, Antoine; Brun, Allan Sacha; Buchlin, Eric Bibcode: 2021ApJ...910...90H Altcode: 2021arXiv210111511H We study the behavior and properties of the solar wind using a 2.5D Alfvén wave (AW)-driven wind model. We first systematically compare the results of an AW-driven wind model with a polytropic approach. Polytropic magnetohydrodynamic wind models are thermally driven, while AWs act as additional acceleration and heating mechanisms in the AW-driven model. We confirm that an AW-driven model is required to reproduce the observed bimodality of slow and fast solar winds. We are also able to reproduce the observed anticorrelation between the terminal wind velocity and the coronal source temperature with the AW-driven wind model. We also show that the wind properties along an 11 yr cycle differ significantly from one model to the other. The AW-driven model again shows the best agreement with observational data. Indeed, solar surface magnetic field topology plays an important role in the AW-driven wind model, as it enters directly into the input energy sources via the Poynting flux. On the other hand, the polytropic wind model is driven by an assumed pressure gradient; thus, it is relatively less sensitive to the surface magnetic field topology. Finally, we note that the net torque spinning down the Sun exhibits the same trends in the two models, showing that the polytropic approach still correctly captures the essence of stellar winds. Title: Investigating the origin of the FIP effect with a shell turbulence model Authors: Réville, Victor; Rouillard, Alexis P.; Velli, Marco; Verdini, Andrea; Buchlin, Éric; Lavarra, Michael; Poirier, Nicolas Bibcode: 2021FrASS...8....2R Altcode: 2021arXiv210101440R The enrichment of coronal loops and the slow solar wind with elements that have low First Ionization Potential, known as the FIP effect, has often been interpreted as the tracer of a common origin. A current explanation for this FIP fractionation rests on the influence of ponderomotive forces and turbulent mixing acting at the top of the chromosphere. The implied wave transport and turbulence mechanisms are also key to wave-driven coronal heating and solar wind acceleration models. This work makes use of a shell turbulence model run on open and closed magnetic field lines of the solar corona to investigate with a unified approach the influence of magnetic topology, turbulence amplitude and dissipation on the FIP fractionation. We try in particular to assess whether there is a clear distinction between the FIP effect on closed and open field regions. Title: Magnetic Imaging of the Outer Solar Atmosphere (MImOSA): Unlocking the driver of the dynamics in the upper solar atmosphere Authors: Peter, H.; Alsina Ballester, E.; Andretta, V.; Auchere, F.; Belluzzi, L.; Bemporad, A.; Berghmans, D.; Buchlin, E.; Calcines, A.; Chitta, L. P.; Dalmasse, K.; del Pino Aleman, T.; Feller, A.; Froment, C.; Harrison, R.; Janvier, M.; Matthews, S.; Parenti, S.; Przybylski, D.; Solanki, S. K.; Stepan, J.; Teriaca, L.; Trujillo Bueno, J. Bibcode: 2021arXiv210101566P Altcode: The magnetic activity of the Sun directly impacts the Earth and human life. Likewise, other stars will have an impact on the habitability of planets orbiting these host stars. The lack of information on the magnetic field in the higher atmospheric layers hampers our progress in understanding solar magnetic activity. Overcoming this limitation would allow us to address four paramount long-standing questions: (1) How does the magnetic field couple the different layers of the atmosphere, and how does it transport energy? (2) How does the magnetic field structure, drive and interact with the plasma in the chromosphere and upper atmosphere? (3) How does the magnetic field destabilise the outer solar atmosphere and thus affect the interplanetary environment? (4) How do magnetic processes accelerate particles to high energies? New ground-breaking observations are needed to address these science questions. We suggest a suite of three instruments that far exceed current capabilities in terms of spatial resolution, light-gathering power, and polarimetric performance: (a) A large-aperture UV-to-IR telescope of the 1-3 m class aimed mainly to measure the magnetic field in the chromosphere by combining high spatial resolution and high sensitivity. (b) An extreme-UV-to-IR coronagraph that is designed to measure the large-scale magnetic field in the corona with an aperture of about 40 cm. (c) An extreme-UV imaging polarimeter based on a 30 cm telescope that combines high throughput in the extreme UV with polarimetry to connect the magnetic measurements of the other two instruments. This mission to measure the magnetic field will unlock the driver of the dynamics in the outer solar atmosphere and thereby greatly advance our understanding of the Sun and the heliosphere. Title: Stereoscopic Measurements of Coronal Doppler Velocities aboard Solar Orbiter Authors: Podladchikova, Olena; Harra, Louise K.; Mandrini, Cristina H.; Rodriguez, Luciano; Parenti, Susanna; Dolla, Laurent; Buchlin, Eric; Auchere, Frederic; Mierla, Marilena; Barczynski, Krzysztof Bibcode: 2021cosp...43E.957P Altcode: The Solar Orbiter mission, whose orbit is outside the Sun-Earth line, opens up novel opportunities for the combined analysis of measurements by solar imagers and spectrometers. For the first time different spectrometers will be located at wide angles with each other allowing 3D spectroscopy in the solar atmosphere. In order to develop a methodology for these opportunities we make use of the Hinode EUV Imaging Spectrometer (EIS) and Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO) and by employing solar rotation we simulate the measurements of spectrometers that have different views of solar corona. The resulting data allows us to apply stereoscopic tie-pointing and triangulation techniques designed for SECCHI (Sun Earth Connection Coronal and Heliospheric Investigation) imaging suite on the STEREO (Solar Terrestrial Relations Observatory) spacecraft pair and perform three-dimensional analysis of Doppler shifts of quasi-stationary active region.We present a technique that allows the accurate reconstruction of the 3D velocity vector in plasma flows along open and closed magnetic loops. This technique will be applied to the real situation of two spacecraft at different separations with spectrometers onboard. This will include the Solar Orbiter Spectral Imaging of the Coronal Environment (SPICE), the Solar Orbiter Extreme Ultraviolet Imager (EUI), the Interface Region Imaging Spectrograph (IRIS) and Hinode EIS spectrometers and we summarise how these can be coordinated. This 3D spectroscopy is a new research domain that will aid the understanding of the complex flows that take place throughout the solar atmosphere. Title: The MDOR/PDOR on-line module for MISO, the planning software of Solar Orbiter instruments Authors: Volpicelli, Cosimo; Landini, Federico; Pancrazzi, Maurizio; Straus, Thomas; Susino, Roberto; Nicolini, Gianalfredo; Sasso, Clementina; Fabi, Michele; De Leo, Yara; Casini, Chiara; Naletto, Giampiero; Nicolosi, Piergiorgio; Spadaro, Daniele; Andretta, Vincenzo; Antonucci, Ester; Fineschi, Silvano; Da Deppo, Vania; Zuppella, Paola; Frassetto, Fabio; Slemer, Alessandra; Mercier, Claude; Kouliche, Dimitri; Caminade, Stephane; Picard, David; Buchlin, Eric; Auchère, Frédéric; Romoli, Marco Bibcode: 2020SPIE11452E..0SV Altcode: Solar Orbiter is a solar mission that will approach the Sun down to a minimum perihelion of 0.28 AU and will increase its orbit inclination with respect to the ecliptic up to a maximum angle of 34 deg. For imagers aboard Solar Orbiter there will be three 10-days remote sensing windows per orbit. Observations shall be carefully planned at least 6 months in advance. The Multi Instrument Sequence Organizer (MISO) is a web based platform developed by the SPICE group and made available to support Solar Orbiter instruments teams in planning observations by assembling Mission Database sequences. Metis is the UV and visible light coronagraph aboard Solar Orbiter. Metis is a complex instrument characterized by a rich variety of observing modes, which required a careful commissioning activity and will need support for potential maintenance operations throughout the mission. In order to support commissioning and maintenance activities, the Metis team developed a PDOR (Payload Direct Operation Request) and MDOR (Memory Direct Operation Request) module integrated in MISO and made available to all Solar Orbiter instruments. An effort was made in order to interpret the coding philosophy of the main project and to make the additional module as homogeneous as possible both to the web interface and to the algorithm logic, while integrating characteristics which are peculiar to PDORs and MDORs. An user friendly web based interface allows the operator to build the operation request and to successively modify or integrate it with further or alternative information. In the present work we describe the PDOR/MDOR module for MISO by addressing its logic and main characteristics. Title: Relative coronal abundance diagnostics with Solar Orbiter/SPICE Authors: Zambrana Prado, N.; Buchlin, E.; Peter, H.; Young, P. R.; Auchere, F.; Carlsson, M.; Fludra, A.; Hassler, D.; Aznar Cuadrado, R.; Caminade, S.; Caldwell, M.; DeForest, C.; Fredvik, T.; Harra, L.; Janvier, M.; Kucera, T. A.; Giunta, A. S.; Grundy, T.; Müller, D.; Parenti, S.; Schmutz, W. K.; Schühle, U.; Sidher, S.; Teriaca, L.; Thompson, W. T.; Williams, D. Bibcode: 2020AGUFMSH038..09Z Altcode: Linking solar activity on the surface and in the corona to the inner heliosphere is one of Solar Orbiter's main goals. Its UV spectrometer SPICE (SPectral Imaging of the Coronal Environment) will provide relative abundance measurements which will be key in this quest as different structures on the Sun have different abundances as a consequence of the FIP (First Ionization Potential) effect. Solar Orbiter's unique combination of remote sensing and in-situ instruments coupled with observation from other missions such as Parker Solar Probe will allow us to compare in-situ and remote sensing composition data. With the addition of modeling, these new results will allow us to trace back the source of heliospheric plasma. As high telemetry will not always be available with SPICE, we have developed a method for measuring relative abundances that is both telemetry efficient and reliable. Unlike methods based on Differential Emission Measure (DEM) inversion, the Linear Combination Ratio (LCR) method does not require a large number of spectral lines. This new method is based on linear combinations of UV spectral lines. The coefficients of the combinations are optimized such that the ratio of two linear combinations of radiances would yield the relative abundance of two elements. We present some abundance diagnostics tested on different combinations of spectral lines observable by SPICE. Title: Dynamics and thermal structure in the quiet Sun seen by SPICE Authors: Peter, H.; Aznar Cuadrado, R.; Schühle, U.; Teriaca, L.; Auchere, F.; Carlsson, M.; Fludra, A.; Hassler, D.; Buchlin, E.; Caminade, S.; Caldwell, M.; DeForest, C.; Fredvik, T.; Harra, L. K.; Janvier, M.; Kucera, T. A.; Giunta, A. S.; Grundy, T.; Müller, D.; Parenti, S.; Schmutz, W. K.; Sidher, S.; Thompson, W. T.; Williams, D.; Young, P. R. Bibcode: 2020AGUFMSH038..03P Altcode: We will present some of the early data of the Spectral Imaging of the Coronal Environment (SPICE) instrument on Solar Orbiter. One of the unique features of SPICE is its capability to record a wide range of wavelengths in the extreme UV with the possibility to record spectral lines giving access to a continuous plasma temperature range from 10.000 K to well above 1 MK. The data taken so far were for commissioning purposes and they can be used for a preliminary evaluation of the science performance of the instrument. Here we will concentrate on sample spectra covering the whole wavelength region and on the early raster maps acquired in bright lines in the quiet Sun close to disk center. Looking at different quiet Sun features we investigate the thermal structure of the atmosphere and flow structures. For this we apply fits to the spectral profiles and check the performance in terms of Doppler shifts and line widths to retrieve the structure of the network in terms of dynamics. While the amount of data available so far is limited, we will have a first look on how quiet Sun plasma responds to heating events. For this, we will compare spectral lines forming at different temperatures recorded at strictly the same time. Title: First Results From SPICE EUV Spectrometer on Solar Orbiter Authors: Fludra, A.; Caldwell, M.; Giunta, A. S.; Grundy, T.; Guest, S.; Sidher, S.; Auchere, F.; Carlsson, M.; Hassler, D.; Peter, H.; Aznar Cuadrado, R.; Buchlin, E.; Caminade, S.; DeForest, C.; Fredvik, T.; Harra, L. K.; Janvier, M.; Kucera, T. A.; Leeks, S.; Mueller, D.; Parenti, S.; Schmutz, W. K.; Schühle, U.; Teriaca, L.; Thompson, W. T.; Tustain, S.; Williams, D.; Young, P. R. Bibcode: 2020AGUFMSH038..02F Altcode: SPICE (Spectral Imaging of Coronal Environment) is one of the remote sensing instruments onboard Solar Orbiter. It is an EUV imaging spectrometer observing the Sun in two wavelength bands: 69.6-79.4 nm and 96.6-105.1 nm. SPICE is capable of recording full spectra in these bands with exposures as short as 1s. SPICE is the only Solar Orbiter instrument that can measure EUV spectra from the disk and low corona of the Sun and record all spectral lines simultaneously. SPICE uses one of three narrow slits, 2"x11', 4''x11', 6''x11', or a wide slit 30''x14'. The primary mirror can be scanned in a direction perpendicular to the slit, allowing raster images of up to 16' in size.

We present an overview of the first SPICE data taken on several days during the instrument commissioning carried out by the RAL Space team between 2020 April 21 and 2020 June 14. We also include results from SPICE observations at the first Solar Orbiter perihelion at 0.52AU, taken between June 16-21st. We give examples of full spectra from the quiet Sun near disk centre and provide a list of key spectral lines emitted in a range of temperatures between 10,000 K and over 1 million K, from neutral hydrogen and ions of carbon, oxygen, nitrogen, neon, sulphur and magnesium. We show examples of first raster images in several strong lines, obtained with different slits and a range of exposure times between 5s and 180s. We describe the temperature coverage and density diagnostics, determination of plasma flows, and discuss possible applications to studies of the elemental abundances in the corona. We also show the first off-limb measurements with SPICE, as obtained when the spacecraft pointed at the limb. Title: Observation of Smallest Ever Detected Brightening Events with the Solar Orbiter EUI HRI-EUV Imager Authors: Parenti, S.; Berghmans, D.; Buchlin, E.; Teriaca, L.; Auchere, F.; Harra, L.; Long, D.; Rochus, P. L.; Schühle, U.; Aznar Cuadrado, R.; Gissot, S.; Kraaikamp, E.; Smith, P.; Stegen, K.; Verbeeck, C. Bibcode: 2020AGUFMSH038..01P Altcode: The Extreme Ultraviolet Imager (EUI) suite on board Solar Orbiter acquired its first images in May 2020. The passband of the 17.4 nm High Resolution Imager (HRI-EUV) is dominated by emission lines of Fe IX and Fe X, that is the 1 million degree solar corona. The solar atmosphere at this temperature is dynamic at all scales, down to the highest spatial resolution available from instruments priori to Solar Orbiter. During the Commissioning phase, HRI-EUV acquired several high temporal resolution (a few seconds) sequences at quiet Sun regions at disk center. The instrument revealed a multitude of brightenings at the smallest-ever detectable spatial scales which, at that time, was about 400 km (two pixels). These events appear to be present everywhere all the time. We present the first results of the analysis of these sequences with the aim of understanding the role of these small scale events in the heating of the solar corona. Title: Stereoscopic Measurements of Coronal Doppler Velocities Authors: Podladchikova, O.; Harra, L. K.; Barczynski, K.; Mandrini, C. H.; Auchere, F.; Buchlin, E.; Dolla, L.; Mierla, M.; Rodriguez, L. Bibcode: 2020AGUFMSH038..07P Altcode: The Solar Orbiter mission, whose orbit is outside the Sun-Earth line, opens up novel opportunities for the combined analysis of measurements by solar imagers and spectrometers. For the first time different spectrometers will be located at wide angles with each other allowing 3D spectroscopy in the solar atmosphere. In order to develop a methodology for these opportunities we make use of the Hinode EUV Imaging Spectrometer (EIS) and Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO) and by employing solar rotation we simulate the measurements of two spectrometers that have different views of solar corona. The resulting data allows us to apply stereoscopic tie-pointing and triangulation techniques designed for SECCHI (Sun Earth Connection Coronal and Heliospheric Investigation) imaging suite on the STEREO (Solar Terrestrial Relations Observatory) spacecraft pair and perform three-dimensional analysis of Doppler shifts of quasi-stationary active region. We present a technique that allows the accurate reconstruction of the 3D velocity vector in plasma flows along open and closed magnetic loops. This technique will be applied to the real situation of two spacecraft at different separations with spectrometers onboard. This will include the Solar Orbiter Spectral Imaging of the Coronal Environment (SPICE), the Solar Orbiter Extreme Ultraviolet Imager (EUI),the Interface Region Imaging Spectrograph (IRIS) and Hinode EIS spectrometers and we summarise how these can be coordinated. This 3D spectroscopy is a new research domain that will aid the understanding of the complex flows that take place throughout the solar atmosphere. Title: Calibrating optical distortions in the Solar Orbiter SPICE spectrograph Authors: Thompson, W. T.; Schühle, U.; Young, P. R.; Auchere, F.; Carlsson, M.; Fludra, A.; Hassler, D.; Peter, H.; Aznar Cuadrado, R.; Buchlin, E.; Caldwell, M.; DeForest, C.; Fredvik, T.; Harra, L. K.; Janvier, M.; Kucera, T. A.; Giunta, A. S.; Grundy, T.; Müller, D.; Parenti, S.; Caminade, S.; Schmutz, W. K.; Teriaca, L.; Williams, D.; Sidher, S. Bibcode: 2020AGUFMSH0360029T Altcode: The Spectral Imaging of the Coronal Environment (SPICE) instrument on Solar Orbiter is a high-resolution imaging spectrometer operating at extreme ultraviolet (EUV) wavelengths from 70.4-79.0 nm and 97.3-104.9 nm. A single-mirror off-axis paraboloid focuses the solar image onto the entrance slit of the spectrometer section. A Toroidal Variable Line Space (TVLS) grating images the entrance slit onto a pair of MCP-intensified APS detectors. Ray-tracing analysis prior to launch showed that the instrument was subject to a number of small image distortions which need to be corrected in the final data product. We compare the ray tracing results with measurements made in flight. Co-alignment with other telescopes on Solar Orbiter will also be examined. Title: First results from the EUI and SPICE observations of Alpha Leo near Solar Orbiter first perihelion Authors: Buchlin, E.; Teriaca, L.; Giunta, A. S.; Grundy, T.; Andretta, V.; Auchere, F.; Peter, H.; Berghmans, D.; Carlsson, M.; Fludra, A.; Harra, L.; Hassler, D.; Long, D.; Rochus, P. L.; Schühle, U.; Aznar Cuadrado, R.; Caldwell, M.; Caminade, S.; DeForest, C.; Fredvik, T.; Gissot, S.; Heerlein, K.; Janvier, M.; Kraaikamp, E.; Kucera, T. A.; Müller, D.; Parenti, S.; Schmutz, W. K.; Sidher, S.; Smith, P.; Stegen, K.; Thompson, W. T.; Verbeeck, C.; Williams, D.; Young, P. R. Bibcode: 2020AGUFMSH0360024B Altcode: On June 16th 2020 Solar Orbiter made a dedicated observing campaign where the spacecraft pointed to the solar limb to allow some of the high resolution instruments to observe the ingress (at the east limb) and later the egress (west limb) of the occultation of the star Alpha Leonis by the solar disk. The star was chosen because its luminosity and early spectral type ensure high and stable flux at wavelengths between 100 and 122 nanometers, a range observed by the High Resolution EUI Lyman alpha telescope (HRI-LYA) and by the long wavelength channel of the SPICE spectrograph. Star observations, when feasible, allow to gather a great deal of information on the instrument performances, such as the radiometric performance and the instrument optical point spread function (PSF).

We report here the first results from the above campaign for the two instruments. Title: First results from combined EUI and SPICE observations of Lyman lines of Hydrogen and He II Authors: Teriaca, L.; Aznar Cuadrado, R.; Giunta, A. S.; Grundy, T.; Parenti, S.; Auchere, F.; Vial, J. C.; Fludra, A.; Berghmans, D.; Carlsson, M.; Harra, L.; Hassler, D.; Long, D.; Peter, H.; Rochus, P. L.; Schühle, U.; Buchlin, E.; Caldwell, M.; Caminade, S.; DeForest, C.; Fredvik, T.; Gissot, S.; Heerlein, K.; Janvier, M.; Kraaikamp, E.; Kucera, T. A.; Mueller, D.; Schmutz, W. K.; Sidher, S.; Smith, P.; Stegen, K.; Thompson, W. T.; Verbeeck, C.; Williams, D.; Young, P. R. Bibcode: 2020AGUFMSH0360003T Altcode: The Solar Orbiter spacecraft carries a powerful set of remote sensing instruments that allow studying the solar atmosphere with unprecedented diagnostic capabilities. Many such diagnostics require the simultaneous usage of more than one instrument. One example of that is the capability, for the first time, to obtain (near) simultaneous spatially resolved observations of the emission from the first three lines of the Lyman series of hydrogen and of He II Lyman alpha. In fact, the SPectral Imaging of the Coronal Environment (SPICE) spectrometer can observe the Lyman beta and gamma lines in its long wavelength (SPICE-LW) channel, the High Resolution Lyman Alpha (HRI-LYA) telescope of the Extreme Ultraviolet Imager (EUI) acquires narrow band images in the Lyman alpha line while the Full Disk Imager (FSI) of EUI can take images dominated by the Lyman alpha line of ionized Helium at 30.4 nm (FSI-304). Being hydrogen and helium the main components of our star, these very bright transitions play an important role in the energy budget of the outer atmosphere via radiative losses and the measurement of their profiles and radiance ratios is a fundamental constraint to any comprehensive modelization effort of the upper solar chromosphere and transition region. Additionally, monitoring their average ratios can serve as a check out for the relative radiometric performance of the two instruments throughout the mission. Although the engineering data acquired so far are far from ideal in terms of time simultaneity (often only within about 1 h) and line coverage (often only Lyman beta was acquired by SPICE and not always near simultaneous images from all three telescopes are available) the analysis we present here still offers a great opportunity to have a first look at the potential of this diagnostic from the two instruments. In fact, we have identified a series of datasets obtained at disk center and at various positions at the solar limb that allow studying the Lyman alpha to beta radiance ratio and their relation to He II 30.4 as a function of the position on the Sun (disk center versus limb and quiet Sun versus coronal holes). Title: Differential Emission Measure Evolution as a Precursor of Solar Flares Authors: Gontikakis, C.; Kontogiannis, I.; Georgoulis, M. K.; Guennou, C.; Syntelis, P.; Park, S. H.; Buchlin, E. Bibcode: 2020arXiv201106433G Altcode: We analyse the temporal evolution of the Differential Emission Measure (DEM) of solar active regions and explore its usage in solar flare prediction. The DEM maps are provided by the Gaussian Atmospheric Imaging Assembly (GAIA-DEM) archive, calculated assuming a Gaussian dependence of the DEM on the logarithmic temperature. We analyse time-series of sixteen solar active regions and a statistically significant sample of 9454 point-in-time observations corresponding to hundreds of regions observed during solar cycle 24. The time-series analysis shows that the temporal derivatives of the Emission Measure dEM/dt and the maximum DEM temperature dTmax/dt frequently exhibit high positive values a few hours before M- and X-class flares, indicating that flaring regions become brighter and hotter as the flare onset approaches. From the point-in-time observations we compute the conditional probabilities of flare occurrences using the distributions of positive values of the dEM/dt, and dTmax/dt and compare them with corresponding flaring probabilities of the total unsigned magnetic flux, a conventionally used, standard flare predictor. For C-class flares, conditional probabilities have lower or similar values with the ones derived for the unsigned magnetic flux, for 24 and 12 hours forecast windows. For M- and X-class flares, these probabilities are higher than those of the unsigned flux for higher parameter values. Shorter forecast windows improve the conditional probabilities of dEM/dt, and dTmax/dt in comparison to those of the unsigned magnetic flux. We conclude that flare forerunner events such as preflare heating or small flare activity prior to major flares reflect on the temporal evolution of EM and Tmax. Of these two, the temporal derivative of the EM could conceivably be used as a credible precursor, or short-term predictor, of an imminent flare. Title: Coordination within the remote sensing payload on the Solar Orbiter mission Authors: Auchère, F.; Andretta, V.; Antonucci, E.; Bach, N.; Battaglia, M.; Bemporad, A.; Berghmans, D.; Buchlin, E.; Caminade, S.; Carlsson, M.; Carlyle, J.; Cerullo, J. J.; Chamberlin, P. C.; Colaninno, R. C.; Davila, J. M.; De Groof, A.; Etesi, L.; Fahmy, S.; Fineschi, S.; Fludra, A.; Gilbert, H. R.; Giunta, A.; Grundy, T.; Haberreiter, M.; Harra, L. K.; Hassler, D. M.; Hirzberger, J.; Howard, R. A.; Hurford, G.; Kleint, L.; Kolleck, M.; Krucker, S.; Lagg, A.; Landini, F.; Long, D. M.; Lefort, J.; Lodiot, S.; Mampaey, B.; Maloney, S.; Marliani, F.; Martinez-Pillet, V.; McMullin, D. R.; Müller, D.; Nicolini, G.; Orozco Suarez, D.; Pacros, A.; Pancrazzi, M.; Parenti, S.; Peter, H.; Philippon, A.; Plunkett, S.; Rich, N.; Rochus, P.; Rouillard, A.; Romoli, M.; Sanchez, L.; Schühle, U.; Sidher, S.; Solanki, S. K.; Spadaro, D.; St Cyr, O. C.; Straus, T.; Tanco, I.; Teriaca, L.; Thompson, W. T.; del Toro Iniesta, J. C.; Verbeeck, C.; Vourlidas, A.; Watson, C.; Wiegelmann, T.; Williams, D.; Woch, J.; Zhukov, A. N.; Zouganelis, I. Bibcode: 2020A&A...642A...6A Altcode: Context. To meet the scientific objectives of the mission, the Solar Orbiter spacecraft carries a suite of in-situ (IS) and remote sensing (RS) instruments designed for joint operations with inter-instrument communication capabilities. Indeed, previous missions have shown that the Sun (imaged by the RS instruments) and the heliosphere (mainly sampled by the IS instruments) should be considered as an integrated system rather than separate entities. Many of the advances expected from Solar Orbiter rely on this synergistic approach between IS and RS measurements.
Aims: Many aspects of hardware development, integration, testing, and operations are common to two or more RS instruments. In this paper, we describe the coordination effort initiated from the early mission phases by the Remote Sensing Working Group. We review the scientific goals and challenges, and give an overview of the technical solutions devised to successfully operate these instruments together.
Methods: A major constraint for the RS instruments is the limited telemetry (TM) bandwidth of the Solar Orbiter deep-space mission compared to missions in Earth orbit. Hence, many of the strategies developed to maximise the scientific return from these instruments revolve around the optimisation of TM usage, relying for example on onboard autonomy for data processing, compression, and selection for downlink. The planning process itself has been optimised to alleviate the dynamic nature of the targets, and an inter-instrument communication scheme has been implemented which can be used to autonomously alter the observing modes. We also outline the plans for in-flight cross-calibration, which will be essential to the joint data reduction and analysis.
Results: The RS instrument package on Solar Orbiter will carry out comprehensive measurements from the solar interior to the inner heliosphere. Thanks to the close coordination between the instrument teams and the European Space Agency, several challenges specific to the RS suite were identified and addressed in a timely manner. Title: The Solar Orbiter Science Activity Plan. Translating solar and heliospheric physics questions into action Authors: Zouganelis, I.; De Groof, A.; Walsh, A. P.; Williams, D. R.; Müller, D.; St Cyr, O. C.; Auchère, F.; Berghmans, D.; Fludra, A.; Horbury, T. S.; Howard, R. A.; Krucker, S.; Maksimovic, M.; Owen, C. J.; Rodríguez-Pacheco, J.; Romoli, M.; Solanki, S. K.; Watson, C.; Sanchez, L.; Lefort, J.; Osuna, P.; Gilbert, H. R.; Nieves-Chinchilla, T.; Abbo, L.; Alexandrova, O.; Anastasiadis, A.; Andretta, V.; Antonucci, E.; Appourchaux, T.; Aran, A.; Arge, C. N.; Aulanier, G.; Baker, D.; Bale, S. D.; Battaglia, M.; Bellot Rubio, L.; Bemporad, A.; Berthomier, M.; Bocchialini, K.; Bonnin, X.; Brun, A. S.; Bruno, R.; Buchlin, E.; Büchner, J.; Bucik, R.; Carcaboso, F.; Carr, R.; Carrasco-Blázquez, I.; Cecconi, B.; Cernuda Cangas, I.; Chen, C. H. K.; Chitta, L. P.; Chust, T.; Dalmasse, K.; D'Amicis, R.; Da Deppo, V.; De Marco, R.; Dolei, S.; Dolla, L.; Dudok de Wit, T.; van Driel-Gesztelyi, L.; Eastwood, J. P.; Espinosa Lara, F.; Etesi, L.; Fedorov, A.; Félix-Redondo, F.; Fineschi, S.; Fleck, B.; Fontaine, D.; Fox, N. J.; Gandorfer, A.; Génot, V.; Georgoulis, M. K.; Gissot, S.; Giunta, A.; Gizon, L.; Gómez-Herrero, R.; Gontikakis, C.; Graham, G.; Green, L.; Grundy, T.; Haberreiter, M.; Harra, L. K.; Hassler, D. M.; Hirzberger, J.; Ho, G. C.; Hurford, G.; Innes, D.; Issautier, K.; James, A. W.; Janitzek, N.; Janvier, M.; Jeffrey, N.; Jenkins, J.; Khotyaintsev, Y.; Klein, K. -L.; Kontar, E. P.; Kontogiannis, I.; Krafft, C.; Krasnoselskikh, V.; Kretzschmar, M.; Labrosse, N.; Lagg, A.; Landini, F.; Lavraud, B.; Leon, I.; Lepri, S. T.; Lewis, G. R.; Liewer, P.; Linker, J.; Livi, S.; Long, D. M.; Louarn, P.; Malandraki, O.; Maloney, S.; Martinez-Pillet, V.; Martinovic, M.; Masson, A.; Matthews, S.; Matteini, L.; Meyer-Vernet, N.; Moraitis, K.; Morton, R. J.; Musset, S.; Nicolaou, G.; Nindos, A.; O'Brien, H.; Orozco Suarez, D.; Owens, M.; Pancrazzi, M.; Papaioannou, A.; Parenti, S.; Pariat, E.; Patsourakos, S.; Perrone, D.; Peter, H.; Pinto, R. F.; Plainaki, C.; Plettemeier, D.; Plunkett, S. P.; Raines, J. M.; Raouafi, N.; Reid, H.; Retino, A.; Rezeau, L.; Rochus, P.; Rodriguez, L.; Rodriguez-Garcia, L.; Roth, M.; Rouillard, A. P.; Sahraoui, F.; Sasso, C.; Schou, J.; Schühle, U.; Sorriso-Valvo, L.; Soucek, J.; Spadaro, D.; Stangalini, M.; Stansby, D.; Steller, M.; Strugarek, A.; Štverák, Š.; Susino, R.; Telloni, D.; Terasa, C.; Teriaca, L.; Toledo-Redondo, S.; del Toro Iniesta, J. C.; Tsiropoula, G.; Tsounis, A.; Tziotziou, K.; Valentini, F.; Vaivads, A.; Vecchio, A.; Velli, M.; Verbeeck, C.; Verdini, A.; Verscharen, D.; Vilmer, N.; Vourlidas, A.; Wicks, R.; Wimmer-Schweingruber, R. F.; Wiegelmann, T.; Young, P. R.; Zhukov, A. N. Bibcode: 2020A&A...642A...3Z Altcode: 2020arXiv200910772Z Solar Orbiter is the first space mission observing the solar plasma both in situ and remotely, from a close distance, in and out of the ecliptic. The ultimate goal is to understand how the Sun produces and controls the heliosphere, filling the Solar System and driving the planetary environments. With six remote-sensing and four in-situ instrument suites, the coordination and planning of the operations are essential to address the following four top-level science questions: (1) What drives the solar wind and where does the coronal magnetic field originate?; (2) How do solar transients drive heliospheric variability?; (3) How do solar eruptions produce energetic particle radiation that fills the heliosphere?; (4) How does the solar dynamo work and drive connections between the Sun and the heliosphere? Maximising the mission's science return requires considering the characteristics of each orbit, including the relative position of the spacecraft to Earth (affecting downlink rates), trajectory events (such as gravitational assist manoeuvres), and the phase of the solar activity cycle. Furthermore, since each orbit's science telemetry will be downloaded over the course of the following orbit, science operations must be planned at mission level, rather than at the level of individual orbits. It is important to explore the way in which those science questions are translated into an actual plan of observations that fits into the mission, thus ensuring that no opportunities are missed. First, the overarching goals are broken down into specific, answerable questions along with the required observations and the so-called Science Activity Plan (SAP) is developed to achieve this. The SAP groups objectives that require similar observations into Solar Orbiter Observing Plans, resulting in a strategic, top-level view of the optimal opportunities for science observations during the mission lifetime. This allows for all four mission goals to be addressed. In this paper, we introduce Solar Orbiter's SAP through a series of examples and the strategy being followed. Title: Models and data analysis tools for the Solar Orbiter mission Authors: Rouillard, A. P.; Pinto, R. F.; Vourlidas, A.; De Groof, A.; Thompson, W. T.; Bemporad, A.; Dolei, S.; Indurain, M.; Buchlin, E.; Sasso, C.; Spadaro, D.; Dalmasse, K.; Hirzberger, J.; Zouganelis, I.; Strugarek, A.; Brun, A. S.; Alexandre, M.; Berghmans, D.; Raouafi, N. E.; Wiegelmann, T.; Pagano, P.; Arge, C. N.; Nieves-Chinchilla, T.; Lavarra, M.; Poirier, N.; Amari, T.; Aran, A.; Andretta, V.; Antonucci, E.; Anastasiadis, A.; Auchère, F.; Bellot Rubio, L.; Nicula, B.; Bonnin, X.; Bouchemit, M.; Budnik, E.; Caminade, S.; Cecconi, B.; Carlyle, J.; Cernuda, I.; Davila, J. M.; Etesi, L.; Espinosa Lara, F.; Fedorov, A.; Fineschi, S.; Fludra, A.; Génot, V.; Georgoulis, M. K.; Gilbert, H. R.; Giunta, A.; Gomez-Herrero, R.; Guest, S.; Haberreiter, M.; Hassler, D.; Henney, C. J.; Howard, R. A.; Horbury, T. S.; Janvier, M.; Jones, S. I.; Kozarev, K.; Kraaikamp, E.; Kouloumvakos, A.; Krucker, S.; Lagg, A.; Linker, J.; Lavraud, B.; Louarn, P.; Maksimovic, M.; Maloney, S.; Mann, G.; Masson, A.; Müller, D.; Önel, H.; Osuna, P.; Orozco Suarez, D.; Owen, C. J.; Papaioannou, A.; Pérez-Suárez, D.; Rodriguez-Pacheco, J.; Parenti, S.; Pariat, E.; Peter, H.; Plunkett, S.; Pomoell, J.; Raines, J. M.; Riethmüller, T. L.; Rich, N.; Rodriguez, L.; Romoli, M.; Sanchez, L.; Solanki, S. K.; St Cyr, O. C.; Straus, T.; Susino, R.; Teriaca, L.; del Toro Iniesta, J. C.; Ventura, R.; Verbeeck, C.; Vilmer, N.; Warmuth, A.; Walsh, A. P.; Watson, C.; Williams, D.; Wu, Y.; Zhukov, A. N. Bibcode: 2020A&A...642A...2R Altcode: Context. The Solar Orbiter spacecraft will be equipped with a wide range of remote-sensing (RS) and in situ (IS) instruments to record novel and unprecedented measurements of the solar atmosphere and the inner heliosphere. To take full advantage of these new datasets, tools and techniques must be developed to ease multi-instrument and multi-spacecraft studies. In particular the currently inaccessible low solar corona below two solar radii can only be observed remotely. Furthermore techniques must be used to retrieve coronal plasma properties in time and in three dimensional (3D) space. Solar Orbiter will run complex observation campaigns that provide interesting opportunities to maximise the likelihood of linking IS data to their source region near the Sun. Several RS instruments can be directed to specific targets situated on the solar disk just days before data acquisition. To compare IS and RS, data we must improve our understanding of how heliospheric probes magnetically connect to the solar disk.
Aims: The aim of the present paper is to briefly review how the current modelling of the Sun and its atmosphere can support Solar Orbiter science. We describe the results of a community-led effort by European Space Agency's Modelling and Data Analysis Working Group (MADAWG) to develop different models, tools, and techniques deemed necessary to test different theories for the physical processes that may occur in the solar plasma. The focus here is on the large scales and little is described with regards to kinetic processes. To exploit future IS and RS data fully, many techniques have been adapted to model the evolving 3D solar magneto-plasma from the solar interior to the solar wind. A particular focus in the paper is placed on techniques that can estimate how Solar Orbiter will connect magnetically through the complex coronal magnetic fields to various photospheric and coronal features in support of spacecraft operations and future scientific studies.
Methods: Recent missions such as STEREO, provided great opportunities for RS, IS, and multi-spacecraft studies. We summarise the achievements and highlight the challenges faced during these investigations, many of which motivated the Solar Orbiter mission. We present the new tools and techniques developed by the MADAWG to support the science operations and the analysis of the data from the many instruments on Solar Orbiter.
Results: This article reviews current modelling and tool developments that ease the comparison of model results with RS and IS data made available by current and upcoming missions. It also describes the modelling strategy to support the science operations and subsequent exploitation of Solar Orbiter data in order to maximise the scientific output of the mission.
Conclusions: The on-going community effort presented in this paper has provided new models and tools necessary to support mission operations as well as the science exploitation of the Solar Orbiter data. The tools and techniques will no doubt evolve significantly as we refine our procedure and methodology during the first year of operations of this highly promising mission. Title: The Solar Orbiter SPICE instrument. An extreme UV imaging spectrometer Authors: SPICE Consortium; Anderson, M.; Appourchaux, T.; Auchère, F.; Aznar Cuadrado, R.; Barbay, J.; Baudin, F.; Beardsley, S.; Bocchialini, K.; Borgo, B.; Bruzzi, D.; Buchlin, E.; Burton, G.; Büchel, V.; Caldwell, M.; Caminade, S.; Carlsson, M.; Curdt, W.; Davenne, J.; Davila, J.; Deforest, C. E.; Del Zanna, G.; Drummond, D.; Dubau, J.; Dumesnil, C.; Dunn, G.; Eccleston, P.; Fludra, A.; Fredvik, T.; Gabriel, A.; Giunta, A.; Gottwald, A.; Griffin, D.; Grundy, T.; Guest, S.; Gyo, M.; Haberreiter, M.; Hansteen, V.; Harrison, R.; Hassler, D. M.; Haugan, S. V. H.; Howe, C.; Janvier, M.; Klein, R.; Koller, S.; Kucera, T. A.; Kouliche, D.; Marsch, E.; Marshall, A.; Marshall, G.; Matthews, S. A.; McQuirk, C.; Meining, S.; Mercier, C.; Morris, N.; Morse, T.; Munro, G.; Parenti, S.; Pastor-Santos, C.; Peter, H.; Pfiffner, D.; Phelan, P.; Philippon, A.; Richards, A.; Rogers, K.; Sawyer, C.; Schlatter, P.; Schmutz, W.; Schühle, U.; Shaughnessy, B.; Sidher, S.; Solanki, S. K.; Speight, R.; Spescha, M.; Szwec, N.; Tamiatto, C.; Teriaca, L.; Thompson, W.; Tosh, I.; Tustain, S.; Vial, J. -C.; Walls, B.; Waltham, N.; Wimmer-Schweingruber, R.; Woodward, S.; Young, P.; de Groof, A.; Pacros, A.; Williams, D.; Müller, D. Bibcode: 2020A&A...642A..14S Altcode: 2019arXiv190901183A; 2019arXiv190901183S
Aims: The Spectral Imaging of the Coronal Environment (SPICE) instrument is a high-resolution imaging spectrometer operating at extreme ultraviolet wavelengths. In this paper, we present the concept, design, and pre-launch performance of this facility instrument on the ESA/NASA Solar Orbiter mission.
Methods: The goal of this paper is to give prospective users a better understanding of the possible types of observations, the data acquisition, and the sources that contribute to the instrument's signal.
Results: The paper discusses the science objectives, with a focus on the SPICE-specific aspects, before presenting the instrument's design, including optical, mechanical, thermal, and electronics aspects. This is followed by a characterisation and calibration of the instrument's performance. The paper concludes with descriptions of the operations concept and data processing.
Conclusions: The performance measurements of the various instrument parameters meet the requirements derived from the mission's science objectives. The SPICE instrument is ready to perform measurements that will provide vital contributions to the scientific success of the Solar Orbiter mission. Title: The Solar Orbiter EUI instrument: The Extreme Ultraviolet Imager Authors: Rochus, P.; Auchère, F.; Berghmans, D.; Harra, L.; Schmutz, W.; Schühle, U.; Addison, P.; Appourchaux, T.; Aznar Cuadrado, R.; Baker, D.; Barbay, J.; Bates, D.; BenMoussa, A.; Bergmann, M.; Beurthe, C.; Borgo, B.; Bonte, K.; Bouzit, M.; Bradley, L.; Büchel, V.; Buchlin, E.; Büchner, J.; Cabé, F.; Cadiergues, L.; Chaigneau, M.; Chares, B.; Choque Cortez, C.; Coker, P.; Condamin, M.; Coumar, S.; Curdt, W.; Cutler, J.; Davies, D.; Davison, G.; Defise, J. -M.; Del Zanna, G.; Delmotte, F.; Delouille, V.; Dolla, L.; Dumesnil, C.; Dürig, F.; Enge, R.; François, S.; Fourmond, J. -J.; Gillis, J. -M.; Giordanengo, B.; Gissot, S.; Green, L. M.; Guerreiro, N.; Guilbaud, A.; Gyo, M.; Haberreiter, M.; Hafiz, A.; Hailey, M.; Halain, J. -P.; Hansotte, J.; Hecquet, C.; Heerlein, K.; Hellin, M. -L.; Hemsley, S.; Hermans, A.; Hervier, V.; Hochedez, J. -F.; Houbrechts, Y.; Ihsan, K.; Jacques, L.; Jérôme, A.; Jones, J.; Kahle, M.; Kennedy, T.; Klaproth, M.; Kolleck, M.; Koller, S.; Kotsialos, E.; Kraaikamp, E.; Langer, P.; Lawrenson, A.; Le Clech', J. -C.; Lenaerts, C.; Liebecq, S.; Linder, D.; Long, D. M.; Mampaey, B.; Markiewicz-Innes, D.; Marquet, B.; Marsch, E.; Matthews, S.; Mazy, E.; Mazzoli, A.; Meining, S.; Meltchakov, E.; Mercier, R.; Meyer, S.; Monecke, M.; Monfort, F.; Morinaud, G.; Moron, F.; Mountney, L.; Müller, R.; Nicula, B.; Parenti, S.; Peter, H.; Pfiffner, D.; Philippon, A.; Phillips, I.; Plesseria, J. -Y.; Pylyser, E.; Rabecki, F.; Ravet-Krill, M. -F.; Rebellato, J.; Renotte, E.; Rodriguez, L.; Roose, S.; Rosin, J.; Rossi, L.; Roth, P.; Rouesnel, F.; Roulliay, M.; Rousseau, A.; Ruane, K.; Scanlan, J.; Schlatter, P.; Seaton, D. B.; Silliman, K.; Smit, S.; Smith, P. J.; Solanki, S. K.; Spescha, M.; Spencer, A.; Stegen, K.; Stockman, Y.; Szwec, N.; Tamiatto, C.; Tandy, J.; Teriaca, L.; Theobald, C.; Tychon, I.; van Driel-Gesztelyi, L.; Verbeeck, C.; Vial, J. -C.; Werner, S.; West, M. J.; Westwood, D.; Wiegelmann, T.; Willis, G.; Winter, B.; Zerr, A.; Zhang, X.; Zhukov, A. N. Bibcode: 2020A&A...642A...8R Altcode: Context. The Extreme Ultraviolet Imager (EUI) is part of the remote sensing instrument package of the ESA/NASA Solar Orbiter mission that will explore the inner heliosphere and observe the Sun from vantage points close to the Sun and out of the ecliptic. Solar Orbiter will advance the "connection science" between solar activity and the heliosphere.
Aims: With EUI we aim to improve our understanding of the structure and dynamics of the solar atmosphere, globally as well as at high resolution, and from high solar latitude perspectives.
Methods: The EUI consists of three telescopes, the Full Sun Imager and two High Resolution Imagers, which are optimised to image in Lyman-α and EUV (17.4 nm, 30.4 nm) to provide a coverage from chromosphere up to corona. The EUI is designed to cope with the strong constraints imposed by the Solar Orbiter mission characteristics. Limited telemetry availability is compensated by state-of-the-art image compression, onboard image processing, and event selection. The imposed power limitations and potentially harsh radiation environment necessitate the use of novel CMOS sensors. As the unobstructed field of view of the telescopes needs to protrude through the spacecraft's heat shield, the apertures have been kept as small as possible, without compromising optical performance. This led to a systematic effort to optimise the throughput of every optical element and the reduction of noise levels in the sensor.
Results: In this paper we review the design of the two elements of the EUI instrument: the Optical Bench System and the Common Electronic Box. Particular attention is also given to the onboard software, the intended operations, the ground software, and the foreseen data products.
Conclusions: The EUI will bring unique science opportunities thanks to its specific design, its viewpoint, and to the planned synergies with the other Solar Orbiter instruments. In particular, we highlight science opportunities brought by the out-of-ecliptic vantage point of the solar poles, the high-resolution imaging of the high chromosphere and corona, and the connection to the outer corona as observed by coronagraphs. Title: Relative abundance diagnostics with SPICE, the EUV spectrometer on-board Solar Orbiter Authors: Zambrana Prado, Natalia; Buchlin, Eric; Peter, Hardi Bibcode: 2020EGUGA..2220154Z Altcode: With the launches of Parker Solar Probe and Solar Orbiter, we are closer than ever to linking solar activity on the surface and in the corona to the inner heliosphere. In this quest, relative abundance measurements will be key as different structures on the Sun have different abundances as a consequence of the FIP (First Ionization Potential) effect.Comparing in-situ and remote sensing composition data, coupled with modeling, will allow us to trace back the source of heliospheric plasma. Solar Orbiter has a unique combination of in-situ and remote sensing instruments that will hopefully allow us to make such comparisons.High telemetry will not always be available with SPICE (SPectral Imaging of the Coronal Environment), the EUV spectrometer on board Solar Orbiter. We have therefore developed a method for measuring relative abundances that is both telemetry efficient and reliable. Unlike methods based on Differential Emission Measure (DEM) inversion, the Linear Combination Ratio (LCR) method does not require a large number of spectral lines. This new method is based on optimized linear combinations of only a few UV spectral lines. We present some abundance diagnostics applied to synthesized radiances of spectral lines observable by SPICE. Title: Measuring relative abundances in the solar corona with optimized linear combinations of spectral lines Authors: Zambrana Prado, N.; Buchlin, E. Bibcode: 2019sf2a.conf..383Z Altcode: Elemental abundances in some coronal structures differ significantly from photospheric abundances, with a dependence on the First Ionization Potential (FIP) of the element. Measuring these FIP-dependent abundance biases is important for coronal and heliospheric physics. We aim at building a method for optimal determination of FIP biases in the corona from spectroscopic observations, in a way that is in practice independent from Differential Emission Measure (DEM) inversions. We optimize linear combinations of spectroscopic lines of low-FIP and high-FIP elements so that the ratio of the corresponding radiances yields the relative FIP bias with a good accuracy, for any DEM in a small set of typical DEMs. These optimized linear combinations of lines allow to retrieve a test FIP bias map with a good accuracy, for all DEMs in the map. The method provides a convenient, fast, and accurate way of computing relative FIP bias maps. It could be used to optimize the use of existing observations and the design of new observations and instruments. Title: Measuring relative abundances in the solar corona with optimised linear combinations of spectral lines Authors: Zambrana Prado, Natalia; Buchlin, Éric Bibcode: 2019A&A...632A..20Z Altcode: 2019arXiv191002886Z Context. Elemental abundances in some coronal structures differ significantly from photospheric abundances, with a dependence on the first ionization potential (FIP) of the element. Measuring these FIP-dependent abundance biases is important for coronal and heliospheric physics.
Aims: We aim to build a method for optimal determination of FIP biases in the corona from spectroscopic observations in a way that is in practice independent from differential emission measure (DEM) inversions.
Methods: We optimised linear combinations of spectroscopic lines of low-FIP and high-FIP elements so that the ratio of the corresponding radiances yields the relative FIP bias with good accuracy for any DEM in a small set of typical DEMs.
Results: These optimised linear combinations of lines allow retrieval of a test FIP bias map with good accuracy for all DEMs in the map. The results also compare well with a FIP bias map obtained from observations using a DEM-dependent method.
Conclusions: The method provides a convenient, fast, and accurate way of computing relative FIP bias maps. It can be used to optimise the use of existing observations and the design of new observations and instruments. Title: Some relationships between radiative and atmospheric quantities through 1D NLTE modeling of prominences in the Mg II lines Authors: Vial, J. -C.; Zhang, P.; Buchlin, É. Bibcode: 2019A&A...624A..56V Altcode: Context. With more than four years of IRIS observations, and in order to avoid building customized diagnostics for each observation, it is useful to derive some simple relations between spectra and physical quantities. This is even more useful for the k and h lines of Mg II, which require complex non-local-thermodynamic-equilibrium NLTE treatments.
Aims: The aim of this work concerning prominences is to correlate observable spectral features in h and k lines of Mg II to physical quantities such as the density and the emission measure (EM) in the same way as similar correlations have been obtained in the hydrogen lines. In this way, and within approximations done on some parameters such as temperature, it is possible to build pixel by pixel an IRIS map of the above-mentioned quantities.
Methods: In order to simplify and shorten the modeling, we chose to compute one-dimensional (1D) isothermal and isobaric models that are treated with the PROM7 NLTE code available at MEDOC (IAS). We built a set of models with large ranges of temperature, pressure, and thickness. At all altitudes considered, we paid attention to the exact computation of the incident radiation. Then we compared the emergent Mg II h and k intensities with the corresponding hydrogen and electron densities and EMs.
Results: From the NLTE computation, we derive correlations between the k and h emergent intensities on one hand and the densities and EM on the other hand. With some assumptions on the temperature, we obtain a unique relation between the k (and h) intensities and the EM that should be useful for deriving either the hydrogen and electron densities or the effective thickness of an observed prominence.
Conclusions: From NLTE modeling, we have provided a relationship between observable integrated intensities of the Mg II resonance lines and prominence plasma EM, which will contribute to a first-order analysis of long time series of spectroscopic observations, for example, with IRIS. We anticipate building more complex relations between the profiles and other plasma quantities. Title: Launch of a CME-associated eruptive prominence as observed with IRIS and ancillary instruments Authors: Zhang, P.; Buchlin, É.; Vial, J. -C. Bibcode: 2019A&A...624A..72Z Altcode:
Aims: In this paper we focus on the possible observational signatures of the processes which have been put forward for explaining eruptive prominences. We also try to understand the variations in the physical conditions of eruptive prominences and estimate the masses leaving the Sun versus the masses returning to the Sun during eruptive prominences.
Methods: As far as velocities are concerned, we combined an optical flow method on the Atmospheric Imaging Assembly (AIA) 304 Å and Interface Region Imaging Spectrograph (IRIS). Mg II h&k observations in order to derive the plane-of-sky velocities in the prominence, and a Doppler technique on the IRIS Mg II h&k profiles to compute the line-of-sight velocities. As far as densities are concerned, we compared the absolute observed intensities with values derived from non-local thermodynamic equilibrium radiative transfer computations to derive the total (hydrogen) density and consequently compute the mass flows.
Results: The derived electron densities range from 1.3 × 109 to 6.0 × 1010 cm-3 and the derived total hydrogen densities range from 1.5 × 109 to 2.4 × 1011 cm-3 in different regions of the prominence. The mean temperature is around 1.1 × 104 K, which is higher than in quiescent prominences. The ionization degree is in the range of 0.1-10. The total (hydrogen) mass is in the range of 1.3 × 1014-3.2 × 1014 g. The total mass drainage from the prominence to the solar surface during the whole observation time of IRIS is about one order of magnitude smaller than the total mass of the prominence.

The movie associated to Fig. 2 is available at https://www.aanda.org Title: Solar data, dataproducts, and tools at MEDOC Authors: Buchlin, Eric; Caminade, Stéphane; Dufourg, Nicolas; Auchère, Frédéric; Baudin, Frédéric; Bocchialini, Karine; Boumier, Patrick; Janvier, Miho; Parenti, Susanna; Alingery, Pablo; Ballans, Hervé; Chane-Yook, Martine; Dexet, Marc; Mercier, Claude; Poulleau, Gilles Bibcode: 2019EGUGA..2117362B Altcode: MEDOC (Multi-Experiment Data and Operation Centre), initially created as a European data and operation centre for the SOHO mission, has grown with data from other solar physics space missions, from STEREO to SDO. Derived data products such as DEM maps from SDO/AIA, synoptic EUV intensity maps from SOHO/EIT, and catalogues of solar structures are also automatically produced and redistributed. Both the data and the derived data products are publicly available from web interfaces and from programmatic interfaces (with clients for IDL and Python), allowing classical data analysis as well as automatic queries, data download, and processing to be made on large datasets. Title: Nonlinear diffusion models for gravitational wave turbulence Authors: Galtier, Sébastien; Nazarenko, Sergey V.; Buchlin, Éric; Thalabard, Simon Bibcode: 2019PhyD..390...84G Altcode: 2018arXiv180907623G A fourth-order and a second-order nonlinear diffusion model in spectral space are proposed to describe gravitational wave turbulence in the approximation of strongly local interactions. We show analytically that the model equations satisfy the conservation of energy and wave action, and reproduce the power law solutions previously derived from the kinetic equations with a direct cascade of energy and an explosive inverse cascade of wave action. In the latter case, we show numerically by computing the second-order diffusion model that the non-stationary regime exhibits an anomalous scaling which is understood as a self-similar solution of the second kind with a front propagation following the law kf ∼(t∗ - t) 3 . 296, with t <t∗. These results are relevant to better understand the dynamics of the primordial universe where potent sources of gravitational waves may produce space-time turbulence. Title: A New Method for Measuring Relative Abundances in the Solar Corona Authors: Zambrana Prado, Natalia; Buchlin, Eric Bibcode: 2018csc..confE..79Z Altcode: 2018csc..confE..79P Linking the Solar Wind to its origin in the solar atmosphere is a difficult task. One way forward is to use composition data measured in situ and remotely. Indeed, different structures on the Sun have different abundances, that become frozen at a certain height, and therefore we can determine where certain wind plasma detected in situ comes from. However, systematically determining these abundances from remote-sensing observations is difficult because it usually first requires an accurate determination of the Differential Emission Measure (DEM). We present a new method to measure relative abundances using UV spectroscopy, which aims at being independent from the DEM. This method relies on optimizing linear combinations of spectral lines. We test this method using DEMs obtained from AIA observations and creating synthetic intensities with them. This allows us to test the method accurately and to find the best linear combinations. This method could be used semi-automatically for optimal abundance determinations from existing observations as well as for designing new observations such as those from the SPICE spectrometer from the future Solar Orbiter mission. Title: The SDO AIA and HMI archive at MEDOC Authors: Alingery, Pablo; Buchlin, Éric; Caminade, Stéphane; Ballans, Hervé; Baudin, Frédéric; Parenti, Susanna; Bocchialini, Karine Bibcode: 2018csc..confE.113A Altcode: MEDOC, created as the European data and operations center for SoHO, hosts also data from STEREO, SDO, and various other solar physics missions. The SDO archive at MEDOC represents more than 415TB of data, and covers the full length of the mission. It includes aia.lev1 data at a minimum cadence of 60s in the EUV channels (12s at specific periods of interest), and most of the 720s-cadence HMI series. It is complemented by a database of DEM maps derived from AIA. MEDOC provides a reliable, convenient, and fast (especially for European users) access to these SDO data, by a web interface and webservices. We also provide IDL and Python clients to these webservices, allowing complex queries and automated analyses on large datasets to be made. Title: SPICE Operations and Scientific Exploitation Authors: Buchlin, Eric Bibcode: 2018cosp...42E.454B Altcode: The SPICE spectrometer will address key science goals of the Solar Orbiter mission, including science questions on the origin of CMEs, the acceleration of energetic particles, and the connectivity to the heliosphere.The SPICE Operations and Scientific Exploitation Team Consortium was selected by ESA in 2016. Support for the operations and scientific exploitation of SPICE is shared between 4 main agencies in Europe (CNES, UKSA, the Norwegian Space Center, and DLR) and NASA in the United States. The lead funding agency is CNES, responsible for providing leadership and coordinating the collective efforts to ensure that the SPICE operations activities are conducted smoothly.The Consortium will operate SPICE and provide operations support to the Solar Orbiter project to fulfill the mission's science objectives, including:

Planning of SPICE operations, in coordination with other Solar Orbiter instruments.

Providing ESA with a data processing pipeline for low-latency data, and operating a processing pipeline up to calibrated data products.

Maintaining the SPICE instrument, including monitoring and troubleshooting instrument health and safety.

Providing software and support to the scientific community to work with SPICE data.

We will present the tasks to be performed by the consortium, the consortium team structure and responsibilities, as well as an overview of the capabilities of the instrument and its contributions to the Solar Orbiter science goals. Title: An analysis of simultaneous observations of a CME-associated eruptive prominence with IRIS, AIA/SDO, EUVI/STEREO and K-COR Authors: Zhang, Ping; Vial, Jean-Claude; Buchlin, Eric Bibcode: 2018cosp...42E3836Z Altcode: We present the simultaneous observations of a CME-associated eruptive prominence which have been made by the Interface Region Imaging Spectrograph (IRIS), Atmospheric Imaging Assembly (AIA) of SDO, EUVI of STEREO and the ground-based K-COR coronagraph. IRIS observations started on 2014 May 28 at 11:25 UT, lasted for about 4.5 hours. With the aim of deriving the velocity vector, we first combined an optical flow method on the AIA 304 observations to compute the POS velocities in the prominence and a Doppler technique with the IRIS observations to compute the LOS velocities. Then we characterized the Mg h and k profiles (time and space-dependent) and compared with the signatures of various (1000) prominence models through NLTE radiative transfer computations (I.A.S. PROM7 code). We paid much attention to the exact incident radiation in various lines and continua. The model parameters include pressure, temperature, height, thickness, radial and turbulence velocities. Having selected the best (fitting) models, we were able to derive the total (hydrogen) density and compute the mass flows. We also used the STEREO observations to derive the 3D geometry of the prominence and K-COR to derive the density later on in the process of eruption. Applying this method to more prominences observed by IRIS could help to reduce the large range of thermodynamic parameters in eruptive prominences and to improve their MHD modeling. Title: Physical conditions in a prominence eruption during its pre-eruption and acceleration Authors: Zhang, Ping; Vial, Jean-Claude; Buchlin, Eric Bibcode: 2018cosp...42E3837Z Altcode: We rely upon the simultaneous observations of a CME-associated eruptive prominence which have been made by the Interface Region Imaging Spectrograph (IRIS), Atmospheric Imaging Assembly (AIA) of SDO, EUVI of STEREO and the ground-based K-COR coronagraph. We focus on the determination of mass flows in order to detect a possible mass loading. In order to derive the full velocity vector, we combine an optical flow method on the AIA 304 and IRIS SJI observations to compute the POS velocities in the prominence and a Doppler technique with the IRIS observations to compute the LOS velocities. Then we focus on the determination of densities through the combination of spectroscopic observations and NLTE modelling. We first characterize the Mg II h and k profiles (time and space-dependent!) through a grid of 6 typical profiles (reversed and unreversed). Then we compare them with the signatures of hundreds of prominence models through NLTE radiative transfer computations (I.A.S. PROM7 code). Much attention is paid to the exact incident radiation in various lines and continua. Having selected the best (fitting) models, we are able to derive the total (hydrogen) density and compute the mass flows. The derivation of physical parameters (e.g. velocity) also takes into account the STEREO observations to derive the 3D geometry of the prominence and K-COR to derive the density later on in the process of eruption. Title: Understanding the usage of the Helioviewer Project clients and services Authors: Ireland, Jack; Zahniy, Serge; Mueller, Daniel; Nicula, Bogdan; Verstringe, Freek; Bourgoignie, Bram; Buchlin, Eric; Alingery, Pablo Bibcode: 2018tess.conf30286I Altcode: The Helioviewer Project enables visual exploration of the Sun and the inner heliosphere for everyone, everywhere via intuitive interfaces and novel technology. The project mainly develops two clients, helioviewer.org and JHelioviewer, and the server-side capabilities accessed via those clients. Images from many different ground and space-based sources are currently available from multiple servers. Solar and heliospheric feature and event information, magnetic field extrapolations and important time-series can also be browsed and visualized using Helioviewer Project clients. Users of the Helioviewer Project have made over two million movies and many millions of screenshots since detailed (and anonymous) logging of Helioviewer Project usage was implemented in February 2011. These usage logs are analyzed to give a detailed breakdown on user interaction with solar and heliospheric data via Helioviewer Project clients and services. We present summary statistics on how our users are using our clients and services, which data they are interested in, and how they choose to interact with different data sources. At the poster presentation we will also be soliciting ideas from the community to improve our clients and services. Title: On the Occurrence of Thermal Nonequilibrium in Coronal Loops Authors: Froment, C.; Auchère, F.; Mikić, Z.; Aulanier, G.; Bocchialini, K.; Buchlin, E.; Solomon, J.; Soubrié, E. Bibcode: 2018ApJ...855...52F Altcode: 2018arXiv180204010F Long-period EUV pulsations, recently discovered to be common in active regions, are understood to be the coronal manifestation of thermal nonequilibrium (TNE). The active regions previously studied with EIT/Solar and Heliospheric Observatory and AIA/SDO indicated that long-period intensity pulsations are localized in only one or two loop bundles. The basic idea of this study is to understand why. For this purpose, we tested the response of different loop systems, using different magnetic configurations, to different stratifications and strengths of the heating. We present an extensive parameter-space study using 1D hydrodynamic simulations (1020 in total) and conclude that the occurrence of TNE requires specific combinations of parameters. Our study shows that the TNE cycles are confined to specific ranges in parameter space. This naturally explains why only some loops undergo constant periodic pulsations over several days: since the loop geometry and the heating properties generally vary from one loop to another in an active region, only the ones in which these parameters are compatible exhibit TNE cycles. Furthermore, these parameters (heating and geometry) are likely to vary significantly over the duration of a cycle, which potentially limits the possibilities of periodic behavior. This study also confirms that long-period intensity pulsations and coronal rain are two aspects of the same phenomenon: both phenomena can occur for similar heating conditions and can appear simultaneously in the simulations. Title: IRIS Observations of Spicules and Structures Near the Solar Limb Authors: Alissandrakis, C. E.; Vial, J. -C.; Koukras, A.; Buchlin, E.; Chane-Yook, M. Bibcode: 2018SoPh..293...20A Altcode: 2018arXiv180102082A We have analyzed Interface Region Imaging Spectrograph (IRIS) spectral and slit-jaw observations of a quiet region near the South Pole. In this article we present an overview of the observations, the corrections, and the absolute calibration of the intensity. We focus on the average profiles of strong (Mg II h and k, C II and Si IV), as well as of weak spectral lines in the near ultraviolet (NUV) and the far ultraviolet (FUV), including the Mg II triplet, thus probing the solar atmosphere from the low chromosphere to the transition region. We give the radial variation of bulk spectral parameters as well as line ratios and turbulent velocities. We present measurements of the formation height in lines and in the NUV continuum from which we find a linear relationship between the position of the limb and the intensity scale height. We also find that low forming lines, such as the Mg II triplet, show no temporal variations above the limb associated with spicules, suggesting that such lines are formed in a homogeneous atmospheric layer and, possibly, that spicules are formed above the height of 2″. We discuss the spatio-temporal structure of the atmosphere near the limb from images of intensity as a function of position and time. In these images, we identify p-mode oscillations in the cores of lines formed at low heights above the photosphere, slow-moving bright features in O I and fast-moving bright features in C II. Finally, we compare the Mg II k and h line profiles, together with intensity values of the Balmer lines from the literature, with computations from the PROM57Mg non-LTE model, developed at the Institut d' Astrophysique Spatiale, and estimated values of the physical parameters. We obtain electron temperatures in the range of ∼8000 K at small heights to ∼20 000 K at large heights, electron densities from 1.1 ×1011 to 4 ×1010cm−3 and a turbulent velocity of ∼24 kms−1. Title: CDPP supporting tools to Solar Orbiter and Parker Solar Probe data exploitation Authors: Genot, V. N.; Cecconi, B.; Dufourg, N.; Gangloff, M.; André, N.; Bouchemit, M.; Jacquey, C.; Pitout, F.; Rouillard, A.; Nathanaël, J.; Lavraud, B.; Durand, J.; Tao, C.; Buchlin, E.; Witasse, O. G. Bibcode: 2017AGUFMSH23D2677G Altcode: In recent years the French Centre de Données de la Physique des Plasmas (CDPP) has extended its data analysis capability by designing a number of new tools. In the solar and heliospheric contexts, and in direct support to the forthcoming solar ESA and NASA missions in these fields, these tools comprise of the Propagation Tool which helps linking solar perturbations observed both in remote and in-situ data; this is achieved through direct connection to the companion solar database MEDOC and the CDPP AMDA database. More recently, in the frame of Europlanet 2020 RI, a 1D MHD solar wind propagation code (Tao et al., 2005) has been interfaced to provide real time solar wind monitors at cruising probes and planetary environments using ACE real time data as inputs (Heliopropa service). Finally, simulations, models and data may be combined and visualized in a 3D context with 3DView. This presentation will overview the various functionalities of these tools and provide examples, in particular a 'CME tracking' case recently published (Witasse et al., 2017). Europlanet 2020 RI has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 654208. Title: The Next Level in Automated Solar Flare Forecasting: the EU FLARECAST Project Authors: Georgoulis, M. K.; Bloomfield, D.; Piana, M.; Massone, A. M.; Gallagher, P.; Vilmer, N.; Pariat, E.; Buchlin, E.; Baudin, F.; Csillaghy, A.; Soldati, M.; Sathiapal, H.; Jackson, D.; Alingery, P.; Argoudelis, V.; Benvenuto, F.; Campi, C.; Florios, K.; Gontikakis, C.; Guennou, C.; Guerra, J. A.; Kontogiannis, I.; Latorre, V.; Murray, S.; Park, S. H.; Perasso, A.; Sciacchitano, F.; von Stachelski, S.; Torbica, A.; Vischi, D. Bibcode: 2017AGUFMSA21C..07G Altcode: We attempt an informative description of the Flare Likelihood And Region Eruption Forecasting (FLARECAST) project, European Commission's first large-scale investment to explore the limits of reliability and accuracy achieved for the forecasting of major solar flares. We outline the consortium, top-level objectives and first results of the project, highlighting the diversity and fusion of expertise needed to deliver what was promised. The project's final product, featuring an openly accessible, fully modular and free to download flare forecasting facility will be delivered in early 2018. The project's three objectives, namely, science, research-to-operations and dissemination / communication, are also discussed: in terms of science, we encapsulate our close-to-final assessment on how close (or far) are we from a practically exploitable solar flare forecasting. In terms of R2O, we briefly describe the architecture of the FLARECAST infrastructure that includes rigorous validation for each forecasting step. From the three different communication levers of the project we finally focus on lessons learned from the two-way interaction with the community of stakeholders and governmental organizations. The FLARECAST project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No. 640216. Title: Understanding the usage of the Helioviewer Project clients and services Authors: Ireland, J.; Zahniy, S.; Mueller, D.; Nicula, B.; Verstringe, F.; Bourgoignie, B.; Buchlin, E.; Alingery, P. Bibcode: 2017AGUFMSH51C2507I Altcode: The Helioviewer Project enables visual exploration of the Sun and the inner heliosphere for everyone, everywhere via intuitive interfaces and novel technology. The project mainly develops two clients, helioviewer.org and JHelioviewer, and the server-side capabilities accessed via those clients. Images from many different ground and space-based sources are currently available from multiple servers. Solar and heliospheric feature and event information, magnetic field extrapolations and important time-series can also be browsed and visualized using Helioviewer Project clients. Users of the Helioviewer Project have made over two million movies and many millions of screenshots since detailed (and anonymous) logging of Helioviewer Project usage was implemented in February 2011. These usage logs are analyzed to give a detailed breakdown on user interaction with solar and heliospheric data via Helioviewer Project clients and services. We present summary statistics on how our users are using our clients and services, which data they are interested in, and how they choose to interact with different data sources. At the poster presentation we will also be soliciting ideas from the community to improve our clients and services. Title: A propagation tool to connect remote-sensing observations with in-situ measurements of heliospheric structures Authors: Rouillard, A. P.; Lavraud, B.; Génot, V.; Bouchemit, M.; Dufourg, N.; Plotnikov, I.; Pinto, R. F.; Sanchez-Diaz, E.; Lavarra, M.; Penou, M.; Jacquey, C.; André, N.; Caussarieu, S.; Toniutti, J. -P.; Popescu, D.; Buchlin, E.; Caminade, S.; Alingery, P.; Davies, J. A.; Odstrcil, D.; Mays, L. Bibcode: 2017P&SS..147...61R Altcode: 2017arXiv170200399R The remoteness of the Sun and the harsh conditions prevailing in the solar corona have so far limited the observational data used in the study of solar physics to remote-sensing observations taken either from the ground or from space. In contrast, the 'solar wind laboratory' is directly measured in situ by a fleet of spacecraft measuring the properties of the plasma and magnetic fields at specific points in space. Since 2007, the solar-terrestrial relations observatory (STEREO) has been providing images of the solar wind that flows between the solar corona and spacecraft making in-situ measurements. This has allowed scientists to directly connect processes imaged near the Sun with the subsequent effects measured in the solar wind. This new capability prompted the development of a series of tools and techniques to track heliospheric structures through space. This article presents one of these tools, a web-based interface called the 'Propagation Tool' that offers an integrated research environment to study the evolution of coronal and solar wind structures, such as Coronal Mass Ejections (CMEs), Corotating Interaction Regions (CIRs) and Solar Energetic Particles (SEPs). These structures can be propagated from the Sun outwards to or alternatively inwards from planets and spacecraft situated in the inner and outer heliosphere. In this paper, we present the global architecture of the tool, discuss some of the assumptions made to simulate the evolution of the structures and show how the tool connects to different databases. Title: Validating coronal magnetic field reconstruction methods using solar wind simulations and synthetic imagery Authors: Pinto, Rui; Rouillard, Alexis; Génot, Vincent; Amari, Tahar; Buchlin, Eric; Arge, Nick; Sasso, Clementina; Andretta, Vincenzo; Bemporad, Alessandro Bibcode: 2017EGUGA..1913650P Altcode: We present an ongoing effort within the ESA Modeling and Data Analysis Working Group (MADAWG) to determine automatically the magnetic connectivity between the solar surface and any point in interplanetary space. The goal is to produce predictions of the paths and propagation delays of plasma and energetic particle propagation. This is a key point for the data exploitation of the Solar Orbiter and Solar Probe Plus missions, and for establishing connections between remote and in-situ data. The background coronal magnetic field is currently determined via existing surface magnetograms and PFSS extrapolations, but the interface is ready to include different combinations of coronal field reconstruction methods (NLFFF, Solar Models), wind models (WSA, MULTI-VP), heliospheric models (Parker spiral, ENLIL, EUHFORIA). Some model realisations are also based on advanced magnetograms based on data assimilation techniques (ADAPT) and the HELCATS catalogue of simulations. The results from the different models will be combined in order to better assess the modelling uncertainties. The wind models provide synthetic white-light and EUV images which are compared to coronographic imagery, and the heliospheric models provide estimations of synthetic in-situ data wich are compared to spacecraft data. A part of this is work (wind modelling) is supported by the FP7 project #606692 (HELCATS). Title: Erratum: “On the Fourier and Wavelet Analysis of Coronal Time Series” (2016, ApJ, 825, 110) Authors: Auchère, F.; Froment, C.; Bocchialini, K.; Buchlin, E.; Solomon, J. Bibcode: 2017ApJ...838..166A Altcode: No abstract at ADS Title: Long-period Intensity Pulsations in Coronal Loops Explained by Thermal Non-equilibrium Cycles Authors: Froment, C.; Auchère, F.; Aulanier, G.; Mikić, Z.; Bocchialini, K.; Buchlin, E.; Solomon, J. Bibcode: 2017ApJ...835..272F Altcode: 2017arXiv170101309F In solar coronal loops, thermal non-equilibrium (TNE) is a phenomenon that can occur when the heating is both highly stratified and quasi-constant. Unambiguous observational identification of TNE would thus permit us to strongly constrain heating scenarios. While TNE is currently the standard interpretation of coronal rain, the long-term periodic evolution predicted by simulations has never been observed. However, the detection of long-period intensity pulsations (periods of several hours) has been recently reported with the Solar and Heliospheric Observatory/EIT, and this phenomenon appears to be very common in loops. Moreover, the three intensity-pulsation events that we recently studied with the Solar Dynamics Observatory/Atmospheric Imaging Assembly (AIA) show strong evidence for TNE in warm loops. In this paper, a realistic loop geometry from linear force-free field (LFFF) extrapolations is used as input to 1D hydrodynamic simulations. Our simulations show that, for the present loop geometry, the heating has to be asymmetrical to produce TNE. We analyze in detail one particular simulation that reproduces the average thermal behavior of one of the pulsating loop bundle observed with AIA. We compare the properties of this simulation with those deduced from the observations. The magnetic topology of the LFFF extrapolations points to the presence of sites of preferred reconnection at one footpoint, supporting the presence of asymmetric heating. In addition, we can reproduce the temporal large-scale intensity properties of the pulsating loops. This simulation further strengthens the interpretation of the observed pulsations as signatures of TNE. This consequently provides important information on the heating localization and timescale for these loops. Title: Space-weather assets developed by the French space-physics community Authors: Rouillard, A. P.; Pinto, R. F.; Brun, A. S.; Briand, C.; Bourdarie, S.; Dudok De Wit, T.; Amari, T.; Blelly, P. -L.; Buchlin, E.; Chambodut, A.; Claret, A.; Corbard, T.; Génot, V.; Guennou, C.; Klein, K. L.; Koechlin, L.; Lavarra, M.; Lavraud, B.; Leblanc, F.; Lemorton, J.; Lilensten, J.; Lopez-Ariste, A.; Marchaudon, A.; Masson, S.; Pariat, E.; Reville, V.; Turc, L.; Vilmer, N.; Zucarello, F. P. Bibcode: 2016sf2a.conf..297R Altcode: We present a short review of space-weather tools and services developed and maintained by the French space-physics community. They include unique data from ground-based observatories, advanced numerical models, automated identification and tracking tools, a range of space instrumentation and interconnected virtual observatories. The aim of the article is to highlight some advances achieved in this field of research at the national level over the last decade and how certain assets could be combined to produce better space-weather tools exploitable by space-weather centres and customers worldwide. This review illustrates the wide range of expertise developed nationally but is not a systematic review of all assets developed in France. Title: Thermal Non-Equilibrium Revealed by Periodic Pulses of Random Amplitudes in Solar Coronal Loops Authors: Auchère, F.; Froment, C.; Bocchialini, K.; Buchlin, E.; Solomon, J. Bibcode: 2016usc..confE.131A Altcode: We recently detected variations in extreme ultraviolet intensity in coronal loops repeating with periods of several hours. Models of loops including stratified and quasi-steady heating predict the development of a state of thermal non-equilibrium (TNE): cycles of evaporative upflows at the footpoints followed by falling condensations at the apex. Based on Fourier and wavelet analysis, we demonstrate that the observed periodic signals are indeed not signatures of vibrational modes. Instead, superimposed on the power law expected from the stochastic background emission, the power spectra of the time series exhibit the discrete harmonics and continua expected from periodic trains of pulses of random amplitudes. These characteristics reinforce our earlier interpretation of these pulsations as being aborted TNE cycles. Title: The SDO AIA and HMI archive at MEDOC Authors: Alingery, P.; Wang, G.; Buchlin, E.; Caminade, S.; Ballans, H.; Baudin, F.; Parenti, S. Bibcode: 2016usc..confE..97A Altcode: MEDOC, created as the European data and operations center for SoHO, hosts also data from STEREO, SDO, and various other solar physics missions. The SDO archive at MEDOC represents more than 250TB of data, and covers the full length of the mission. It includes aia.lev1 data at a minimum cadence of 60s in the EUV channels (12s at specific periods of interest), and most of the 720s-cadence HMI series. It is complemented by a database of DEM maps derived from AIA, that will be presented at the mini-workshop on thermal diagnostics. MEDOC provides a reliable, convenient, and fast (especially for European users) access to these SDO data, by a web interface and webservices. We also provide IDL and Python clients to these webservices, allowing complex queries and automated analyses on large datasets to be made. Title: The SDO AIA and HMI archive at MEDOC Authors: Buchlin, Eric Bibcode: 2016usc..confE..97B Altcode: MEDOC, created as the European data and operations center for SoHO, hosts also data from STEREO, SDO, and various other solar physics missions. The SDO archive at MEDOC represents more than 250TB of data, and covers the full length of the mission. It includes aia.lev1 data at a minimum cadence of 60s in the EUV channels (12s at specific periods of interest), and most of the 720s-cadence HMI series. It is complemented by a database of DEM maps derived from AIA, that will be presented at the mini-workshop on thermal diagnostics. MEDOC provides a reliable, convenient, and fast (especially for European users) access to these SDO data, by a web interface and webservices. We also provide IDL and Python clients to these webservices, allowing complex queries and automated analyses on large datasets to be made. Title: Energetic characterisation and statistics of solar coronal brightenings Authors: Buchlin, Eric Bibcode: 2016usc..confE.102B Altcode: To explain the high temperature of the corona, much attention has been paid to the distribution of energy in dissipation events. Indeed, if the event energy distribution is steep enough, the smallest, unobservable events could be the largest contributors to the total energy dissipation in the corona. Previous observations have shown a wide distribution of energies but remain inconclusive about the precise slope. Furthermore, these results rely on a very crude estimate of the energy. On the other hand, more detailed spectroscopic studies of structures such as coronal bright points do not provide enough statistical information to derive their total contribution to heating. We aim at getting a better estimate of the distributions of the energy dissipated in coronal heating events using high-resolution, multi-channel EUV data. To estimate the energies corresponding to heating events and deduce their distribution, we detected brightenings in five EUV channels of SDO/AIA. We combined the results of these detections and used maps of temperature and emission measure derived from the same observations to compute the energies. We obtain distributions of areas, durations, intensities, and energies (thermal, radiative, and conductive) of events. These distributions are power laws and we also find power-law correlations between event parameters. The energy distributions indicate that the energy from a population of events like the ones we detect represents a small contribution to the total coronal heating, even when extrapolating to smaller scales. The main explanations for this are how heating events can be extracted from observational data, and the incomplete knowledge of the thermal structure and processes in the coronal plasma attainable from available observations. Title: Fourier and Wavelet Analysis of Coronal Time Series Authors: Auchère, F.; Froment, C.; Bocchialini, K.; Buchlin, E.; Solomon, J. Bibcode: 2016usc..confE.130A Altcode: Using Fourier and wavelet analysis, we critically re-assess the significance of our detection of periodic pulsations in coronal loops. We show that the proper identification of the frequency dependence and statistical properties of the different components of the power spectra provies a strong argument against the common practice of data detrending, which tends to produce spurious detections around the cut-off frequency of the filter. In addition, the white and red noise models built into the widely used wavelet code of Torrence & Compo cannot, in most cases, adequately represent the power spectra of coronal time series, thus also possibly causing false positives. Both effects suggest that several reports of periodic phenomena should be re-examined. The Torrence & Compo code nonetheless effectively computes rigorous confidence levels if provided with pertinent models of mean power spectra, and we describe the appropriate manner in which to call its core routines. We recall the meaning of the default confidence levels output from the code, and we propose new Monte-Carlo-derived levels that take into account the total number of degrees of freedom in the wavelet spectra. These improvements allow us to confirm that the power peaks that we detected have a very low probability of being caused by noise. Title: Energetic characterisation and statistics of solar coronal brightenings Authors: Joulin, V.; Buchlin, E.; Solomon, J.; Guennou, C. Bibcode: 2016usc..confE.102J Altcode: To explain the high temperature of the corona, much attention has been paid to the distribution of energy in dissipation events. Indeed, if the event energy distribution is steep enough, the smallest, unobservable events could be the largest contributors to the total energy dissipation in the corona. Previous observations have shown a wide distribution of energies but remain inconclusive about the precise slope. Furthermore, these results rely on a very crude estimate of the energy. On the other hand, more detailed spectroscopic studies of structures such as coronal bright points do not provide enough statistical information to derive their total contribution to heating. We aim at getting a better estimate of the distributions of the energy dissipated in coronal heating events using high-resolution, multi-channel EUV data. To estimate the energies corresponding to heating events and deduce their distribution, we detected brightenings in five EUV channels of SDO/AIA. We combined the results of these detections and used maps of temperature and emission measure derived from the same observations to compute the energies. We obtain distributions of areas, durations, intensities, and energies (thermal, radiative, and conductive) of events. These distributions are power laws and we also find power-law correlations between event parameters. The energy distributions indicate that the energy from a population of events like the ones we detect represents a small contribution to the total coronal heating, even when extrapolating to smaller scales. The main explanations for this are how heating events can be extracted from observational data, and the incomplete knowledge of the thermal structure and processes in the coronal plasma attainable from available observations. Title: Long-period Intensity Pulsations as the Manifestation of the Heating Stratification and Timescale in Coronal Loops Authors: Froment, Clara; Auchère, Frédéric; Aulanier, Guillaume; Mikić, Zoran; Bocchialini, Karine; Buchlin, Eric; Solomon, Jacques Bibcode: 2016usc..confE..47F Altcode: In solar coronal loops, thermal non-equilibrium (TNE) is a phenomenon that can occur when the heating is both highly-stratified and quasi-constant. Unambiguous observational identification of TNE would thus permit to strongly constrain heating scenarios. Up to now, while TNE is the standard interpretation of coronal rain, it was not believed to happen commonly in warm coronal loops. Recently, the detection of long-period intensity pulsations (periods of several hours) has been reported with SoHO/EIT. This phenomenon appears to be very common in loops (Auchère et al. 2014). In Froment et al. 2015, three intensity-pulsation events studied with SDO/AIA, show strong evidence for TNE in warm loops. We use realistic loop geometries from LFFF extrapolations for one of these events are used as input to a 1D hydrodynamic simulation of TNE. A highly-stratified heating function is chosen to reproduce the observed period of pulsation and temperature of the loops. With these conditions, the heating function has to be asymmetric. The magnetic topology of the LFFF extrapolations points to the presence of sites of preferred reconnection at one footpoint, supporting the presence of asymmetric heating. We compared the properties of the simulated loop with the properties deduced from observations. We found that the 1D hydrodynamic simulation can reproduce the large temporal scale intensity properties of the pulsating loops (Froment et al. 2016, submitted). This simulation further strengthen the interpretation of the observed pulsations as signatures of TNE. This implies that the heating for these loops is highly-stratified and that the frequency of the heating events must be high compared to the typical cooling time. Title: GAIA-DEM: a database providing AIA/SDO DEM maps Authors: Buchlin, Eric Bibcode: 2016usc..confE.108B Altcode: The Gaussian AIA DEm Maps (GAIA-DEM) database at MEDOC (IAS) provides through a simple and intuitive web interface DEM inversions of the SDO/AIA data, computed every 30min. The Gaussian approximation is used to describe the main features of the true DEM(log T) by its first moments. For each date, maps of the three Gaussian fit parameters (central temperature, total emission measure and Gaussian width) and of the chi^2 are available in FITS format. Users can preview the maps before downloading them. In addition, users can display the initial SDO/AIA images using Helioviewer, and query the database through webservices accessible from IDL and Python clients. This presentation is for the "Thermal Diagnostics with SDO/AIA" mini-workshop. Title: Automated detection, characterization, and tracking of filaments from SDO data Authors: Buchlin, E.; Mercier, C.; Vial, J. -C. Bibcode: 2016usc..confE.100B Altcode: Thanks to the cadence and continuity of AIA and HMI observations, SDO offers unique data for detecting, characterizing, and tracking solar filaments, until their eruptions, which are often associated with coronal mass ejections. Because of the requirement of short latency when aiming at space weather applications, and because of the important data volume, only an automated detection can be worked out. We present the code "FILaments, Eruptions, and Activations detected from Space" (FILEAS) that we have developed for the automated detection and tracking of filaments. Detections are based on the analysis of AIA 30.4 nm He II images and on the magnetic polarity inversion lines derived from HMI. Following the tracking of filaments as they rotate with the Sun, filament characteristics are computed and a database of filaments parameters is built. We are currently building a database of filament detections by this code, covering the full SDO mission, and that will be made available to the community. Title: Thermal Non-equilibrium Revealed by Periodic Pulses of Random Amplitudes in Solar Coronal Loops Authors: Auchère, F.; Froment, C.; Bocchialini, K.; Buchlin, E.; Solomon, J. Bibcode: 2016ApJ...827..152A Altcode: 2016arXiv160803789A We recently detected variations in extreme ultraviolet intensity in coronal loops repeating with periods of several hours. Models of loops including stratified and quasi-steady heating predict the development of a state of thermal non-equilibrium (TNE): cycles of evaporative upflows at the footpoints followed by falling condensations at the apex. Based on Fourier and wavelet analysis, we demonstrate that the observed periodic signals are indeed not signatures of vibrational modes. Instead, superimposed on the power law expected from the stochastic background emission, the power spectra of the time series exhibit the discrete harmonics and continua expected from periodic trains of pulses of random amplitudes. These characteristics reinforce our earlier interpretation of these pulsations as being aborted TNE cycles. Title: The SPICE Spectral Imager on Solar Orbiter: Linking the Sun to the Heliosphere Authors: Fludra, Andrzej; Haberreiter, Margit; Peter, Hardi; Vial, Jean-Claude; Harrison, Richard; Parenti, Susanna; Innes, Davina; Schmutz, Werner; Buchlin, Eric; Chamberlin, Phillip; Thompson, William; Gabriel, Alan; Morris, Nigel; Caldwell, Martin; Auchere, Frederic; Curdt, Werner; Teriaca, Luca; Hassler, Donald M.; DeForest, Craig; Hansteen, Viggo; Carlsson, Mats; Philippon, Anne; Janvier, Miho; Wimmer-Schweingruber, Robert; Griffin, Douglas; Davila, Joseph; Giunta, Alessandra; Waltham, Nick; Eccleston, Paul; Gottwald, Alexander; Klein, Roman; Hanley, John; Walls, Buddy; Howe, Chris; Schuehle, Udo Bibcode: 2016cosp...41E.607F Altcode: The SPICE (Spectral Imaging of the Coronal Environment) instrument is one of the key remote sensing instruments onboard the upcoming Solar Orbiter Mission. SPICE has been designed to contribute to the science goals of the mission by investigating the source regions of outflows and ejection processes which link the solar surface and corona to the heliosphere. In particular, SPICE will provide quantitative information on the physical state and composition of the solar atmosphere plasma. For example, SPICE will access relative abundances of ions to study the origin and the spatial/temporal variations of the 'First Ionization Potential effect', which are key signatures to trace the solar wind and plasma ejections paths within the heliosphere. Here we will present the instrument and its performance capability to attain the scientific requirements. We will also discuss how different observation modes can be chosen to obtain the best science results during the different orbits of the mission. To maximize the scientific return of the instrument, the SPICE team is working to optimize the instrument operations, and to facilitate the data access and their exploitation. Title: Energetic characterisation and statistics of solar coronal brightenings Authors: Buchlin, Eric; Solomon, Jacques; Joulin, Vincent; Guennou, Chloé Bibcode: 2016cosp...41E.257B Altcode: To explain the high temperature of the corona, much attention has been paid to the distribution of energy in dissipation events, which might be caused by turbulent reconnection. Indeed, if the event energy distribution is steep enough, the smallest, unobservable events could be the largest contributors to the total energy dissipation in the corona. Previous observations have shown a wide distribution of energies but remain inconclusive about the precise slope. Furthermore, these results rely on a very crude estimate of the energy. On the other hand, more detailed spectroscopic studies of structures such as coronal bright points do not provide enough statistical information to derive their total contribution to heating. We aim at getting a better estimate of the distributions of the energy dissipated in coronal heating events using high-resolution, multi-channel Extreme Ultra-Violet (EUV) data. To estimate the energies corresponding to heating events and deduce their distribution, we detect brightenings in five EUV channels of the Atmospheric Imaging Assembly (AIA) on-board the Solar Dynamics Observatory (SDO). We combine the results of these detections and we use maps of temperature and emission measure derived from the same observations to compute the energies. We obtain distributions of areas, durations, intensities, and energies (thermal, radiative, and conductive) of events. These distributions are power-laws, and we find also power-law correlations between event parameters. The energy distributions indicate that the energy from a population of events like the ones we detect represents a small contribution to the total coronal heating, even when extrapolating to smaller scales. The main explanations for this are how heating events can be extracted from observational data, and the incomplete knowledge of the thermal structure and processes in the coronal plasma attainable from available observations. Title: Enabling Solar Flare Forecasting at an Unprecedented Level: the FLARECAST Project Authors: Georgoulis, Manolis K.; Pariat, Etienne; Massone, Anna Maria; Vilmer, Nicole; Jackson, David; Buchlin, Eric; Csillaghy, Andre; Bommier, Veronique; Kontogiannis, Ioannis; Gallagher, Peter; Gontikakis, Costis; Guennou, Chloé; Murray, Sophie; Bloomfield, D. Shaun; Alingery, Pablo; Baudin, Frederic; Benvenuto, Federico; Bruggisser, Florian; Florios, Konstantinos; Guerra, Jordan; Park, Sung-Hong; Perasso, Annalisa; Piana, Michele; Sathiapal, Hanna; Soldati, Marco; Von Stachelski, Samuel; Argoudelis, Vangelis; Caminade, Stephane Bibcode: 2016cosp...41E.657G Altcode: We attempt a brief but informative description of the Flare Likelihood And Region Eruption Forecasting (FLARECAST) project, European Commission's first large-scale investment to explore the limits of reliability and accuracy for the forecasting of major solar flares. The consortium, objectives, and first results of the project - featuring an openly accessible, interactive flare forecasting facility by the end of 2017 - will be outlined. In addition, we will refer to the so-called "explorative research" element of project, aiming to connect solar flares with coronal mass ejections (CMEs) and possibly pave the way for CME, or eruptive flare, prediction. We will also emphasize the FLARECAST modus operandi, namely the diversity of expertise within the consortium that independently aims to science, infrastructure development and dissemination, both to stakeholders and to the general public. Concluding, we will underline that the FLARECAST project responds squarely to the joint COSPAR - ILWS Global Roadmap to shield society from the adversities of space weather, addressing its primary goal and, in particular, its Research Recommendations 1, 2 and 4, Teaming Recommendations II and III, and Collaboration Recommendations A, B, and D. The FLARECAST project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No. 640216. Title: Solar abundances with the SPICE spectral imager on Solar Orbiter Authors: Giunta, Alessandra; Haberreiter, Margit; Peter, Hardi; Vial, Jean-Claude; Harrison, Richard; Parenti, Susanna; Innes, Davina; Schmutz, Werner; Buchlin, Eric; Chamberlin, Phillip; Thompson, William; Bocchialini, Karine; Gabriel, Alan; Morris, Nigel; Caldwell, Martin; Auchere, Frederic; Curdt, Werner; Teriaca, Luca; Hassler, Donald M.; DeForest, Craig; Hansteen, Viggo; Carlsson, Mats; Philippon, Anne; Janvier, Miho; Wimmer-Schweingruber, Robert; Griffin, Douglas; Baudin, Frederic; Davila, Joseph; Fludra, Andrzej; Waltham, Nick; Eccleston, Paul; Gottwald, Alexander; Klein, Roman; Hanley, John; Walls, Buddy; Howe, Chris; Schuehle, Udo; Gyo, Manfred; Pfiffner, Dany Bibcode: 2016cosp...41E.681G Altcode: Elemental composition of the solar atmosphere and in particular abundance bias of low and high First Ionization Potential (FIP) elements are a key tracer of the source regions of the solar wind. These abundances and their spatio-temporal variations, as well as the other plasma parameters , will be derived by the SPICE (Spectral Imaging of the Coronal Environment) EUV spectral imager on the upcoming Solar Orbiter mission. SPICE is designed to provide spectroheliograms (spectral images) using a core set of emission lines arising from ions of both low-FIP and high-FIP elements. These lines are formed over a wide range of temperatures, enabling the analysis of the different layers of the solar atmosphere. SPICE will use these spectroheliograms to produce dynamic composition maps of the solar atmosphere to be compared to in-situ measurements of the solar wind composition of the same elements (i.e. O, Ne, Mg, Fe). This will provide a tool to study the connectivity between the spacecraft (the Heliosphere) and the Sun. We will discuss the SPICE capabilities for such composition measurements. Title: Automated detection, characterization, and tracking of filaments from SDO data Authors: Buchlin, Eric; Vial, Jean-Claude; Mercier, Claude Bibcode: 2016cosp...41E.258B Altcode: Thanks to the cadence and continuity of AIA and HMI observations, SDO offers unique data for detecting, characterizing, and tracking solar filaments, until their eruptions, which are often associated with coronal mass ejections. Because of the requirement of short latency when aiming at space weather applications, and because of the important data volume, only an automated detection can be worked out. We present the code "FILaments, Eruptions, and Activations detected from Space" (FILEAS) that we have developed for the automated detection and tracking of filaments. Detections are based on the analysis of AIA 30.4 nm He II images and on the magnetic polarity inversion lines derived from HMI. Following the tracking of filaments as they rotate with the Sun, filament characteristics are computed and a database of filaments parameters is built. We present the algorithms and performances of the code, and we compare its results with the filaments detected in Hα and already present in the Heliophysics Events Knowledgebase. We finally discuss the possibility of using such a code to detect eruptions in real time. Title: On the Fourier and Wavelet Analysis of Coronal Time Series Authors: Auchère, F.; Froment, C.; Bocchialini, K.; Buchlin, E.; Solomon, J. Bibcode: 2016ApJ...825..110A Altcode: 2016arXiv160605251A Using Fourier and wavelet analysis, we critically re-assess the significance of our detection of periodic pulsations in coronal loops. We show that the proper identification of the frequency dependence and statistical properties of the different components of the power spectra provides a strong argument against the common practice of data detrending, which tends to produce spurious detections around the cut-off frequency of the filter. In addition, the white and red noise models built into the widely used wavelet code of Torrence & Compo cannot, in most cases, adequately represent the power spectra of coronal time series, thus also possibly causing false positives. Both effects suggest that several reports of periodic phenomena should be re-examined. The Torrence & Compo code nonetheless effectively computes rigorous confidence levels if provided with pertinent models of mean power spectra, and we describe the appropriate manner in which to call its core routines. We recall the meaning of the default confidence levels output from the code, and we propose new Monte-Carlo-derived levels that take into account the total number of degrees of freedom in the wavelet spectra. These improvements allow us to confirm that the power peaks that we detected have a very low probability of being caused by noise. Title: Energetic characterisation and statistics of solar coronal brightenings Authors: Joulin, V.; Buchlin, E.; Solomon, J.; Guennou, C. Bibcode: 2016A&A...591A.148J Altcode: 2016arXiv160502780J Context. To explain the high temperature of the corona, much attention has been paid to the distribution of energy in dissipation events. Indeed, if the event energy distribution is steep enough, the smallest, unobservable events could be the largest contributors to the total energy dissipation in the corona. Previous observations have shown a wide distribution of energies but remain inconclusive about the precise slope. Furthermore, these results rely on a very crude estimate of the energy. On the other hand, more detailed spectroscopic studies of structures such as coronal bright points do not provide enough statistical information to derive their total contribution to heating.
Aims: We aim at getting a better estimate of the distributions of the energy dissipated in coronal heating events using high-resolution, multi-channel extreme ultraviolet (EUV) data.
Methods: To estimate the energies corresponding to heating events and deduce their distribution, we detected brightenings in five EUV channels of the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). We combined the results of these detections and used maps of temperature and emission measure derived from the same observations to compute the energies.
Results: We obtain distributions of areas, durations, intensities, and energies (thermal, radiative, and conductive) of events. These distributions are power laws and we also find power-law correlations between event parameters.
Conclusions: The energy distributions indicate that the energy from a population of events like the ones we detect represents a small contribution to the total coronal heating, even when extrapolating to smaller scales. The main explanations for this are how heating events can be extracted from observational data, and the incomplete knowledge of the thermal structure and processes in the coronal plasma attainable from available observations.

Two movies attached to Fig. 3 are available in electronic form at http://www.aanda.org Title: Evidence for Evaporation-incomplete Condensation Cycles in Warm Solar Coronal Loops Authors: Froment, C.; Auchère, F.; Bocchialini, K.; Buchlin, E.; Guennou, C.; Solomon, J. Bibcode: 2015ApJ...807..158F Altcode: 2015arXiv150408129F Quasi-constant heating at the footpoints of loops leads to evaporation and condensation cycles of the plasma: thermal non-equilibrium (TNE). This phenomenon is believed to play a role in the formation of prominences and coronal rain. However, it is often discounted as being involved in the heating of warm loops because the models do not reproduce observations. Recent simulations have shown that these inconsistencies with observations may be due to oversimplifications of the geometries of the models. In addition, our recent observations reveal that long-period intensity pulsations (several hours) are common in solar coronal loops. These periods are consistent with those expected from TNE. The aim of this paper is to derive characteristic physical properties of the plasma for some of these events to test the potential role of TNE in loop heating. We analyzed three events in detail using the six EUV coronal channels of the Solar Dynamics Observatory/Atmospheric Imaging Assembly. We performed both a differential emission measure (DEM) and a time-lag analysis, including a new method to isolate the relevant signal from the foreground and background emission. For the three events, the DEM undergoes long-period pulsations, which is a signature of periodic heating even though the loops are captured in their cooling phase, as is the bulk of the active regions. We link long-period intensity pulsations to new signatures of loop heating with strong evidence for evaporation and condensation cycles. We thus simultaneously witness widespread cooling and TNE. Finally, we discuss the implications of our new observations for both static and impulsive heating models. Title: Automated detection, characterization, and tracking of filaments from SDO data Authors: Buchlin, Eric; Vial, Jean-Claude; Mercier, Claude; Goujon, Jean-Baptiste Bibcode: 2014cosp...40E.425B Altcode: Thanks to the cadence and continuity of AIA and HMI observations, SDO offers unique data for detecting, characterizing, and tracking solar filaments, until their eruptions, which are often associated with coronal mass ejections. Because of the requirement of short latency when aiming at space weather applications, and because of the important data volume, only an automated detection can be worked out. We present the code "FILaments, Eruptions, and Activations detected from Space" (FILEAS) that we have developed for the automated detection and tracking of filaments. Detections are based on the analysis of AIA 30.4 nm He II images and on the magnetic polarity inversion lines derived from HMI. Following the tracking of filaments as they rotate with the Sun, filament characteristics are computed and a database of filaments parameters is built. We present the algorithms and performances of the code, and we compare its results with the filaments detected in Halpha and already present in the Heliophysics Events Knowledgebase. We finally discuss the possibility of using such a code to detect eruptions in real time. Title: Energetic characterisation and statistics of solar coronal brightenings Authors: Joulin, Vincent; Solomon, Jacques; Buchlin, Eric Bibcode: 2014cosp...40E1352J Altcode: The high temperature of the corona could be due to a large contribution of the smallest, unobservable events if the energy distribution of heating events is steep enough. Previous observations have shown a wide distribution of energies but remain inconclusive about the precise slope. Furthermore, these results rely on a very crude estimate of the energy. We aim at getting a better estimate of the distributions of the energy dissipated in coronal heating events using high-resolution, multi-channel Extreme Ultra-Violet (EUV) data. To estimate the energies corresponding to heating events and deduce their distribution, we detect brightenings in five EUV channels of the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). We regroup the results of these detections and we use maps of temperature and emission measure derived from the same observations to compute the thermal, conducted, and radiated energies. The distributions of these energies are wide power-laws, but small events seem not to be sufficient to account for the total heating needed to sustain coronal temperatures. Title: Observations and possible interpretations of very long period intensity pulsations in solar coronal loops Authors: Froment, Clara; Solomon, Jacques; Buchlin, Eric; Bocchialini, Karine; Auchere, Frederic; Guennou, Chloe Bibcode: 2014cosp...40E.903F Altcode: We discovered that intensity pulsations with periods ranging from 3 to 16 hours are common in solar coronal loops. Initially developed for EIT/SOHO 195 nm images, the automatic detection algorithm is now running on AIA/SDO data and allows detection of pulsation events in six coronal bands simultaneously. From may 2010 to december 2013, we detected more than 2000 events in the 6 EUV bands. We focus our study on pulsations in active regions and in particular in solar coronal loops where most of events are detected. A multi-wavelength analysis of some characteristic events is presented to help understand their physical nature. We perform a Differential Emission Measure analysis on AIA time series in order to determine the temporal variations of the thermal structure of the pulsating loops. This analysis gives important clues to investigate possible physical interpretations in particular in term of small perturbations of loops in static equilibrium and to study how this can constraint coronal heating models. We will also compare our observations to the results of a MHD turbulence and heating model of coronal loops. Title: Automated detection, characterization, and tracking of filaments from SDO data Authors: Buchlin, E.; Mercier, C.; Vial, -C., J. Bibcode: 2013enss.confE..78B Altcode: Thanks to the cadence and continuity of AIA and HMI observations, SDO offers unique data for detecting, characterizing, and tracking solar filaments, until their eruptions, which can be associated to coronal mass ejections. Because of the requirement of short latency when aiming at space weather applications, and because of the important data volume, only an automated detection can be worked out. We present the code "FILaments, Eruptions, and Activations detected from Space" (FILEAS) that we are developing at IAS for the automated detection and tracking of filaments. Using data either from local files or from DRMS, detections are based on analysis of AIA 30.4 nm He II images and on magnetic polarity inversion lines derived from HMI. Following the tracking of filaments as their rotate with the Sun, filament characteristics are computed. We discuss the algorithms and performances of the code, and we compare its results with the filaments detected in Halpha and already present in the HEK. We finally discuss the possibility of using this code for detecting eruptions in real time. Title: MEDIA : MEDoc Interface for AIA Authors: Alingery, P.; Soubrié, E.; Auchère, F.; Bocchialini, K.; Boignard, J. P.; Buchlin, E.; Malappert, J. C.; Parenti, S. Bibcode: 2013enss.confE..88A Altcode: MEDOC, the space solar data center at Orsay (http://www.ias.u-psud.fr/medoc) is now providing a new web access to the AIA/SDO level 1 images. This interface has the advantage of being simple, intuitive, very stable and fast. The full resolution 4k x 4k AIA level 1 images archived at MEDOC are downloaded from upstream DRMS nodes with a 1 minute cadence at all wavelengths. The dataset will be kept online on a redundant archive for the whole SDO mission duration. The FITS files are accessible via an user friendly web interface (http://medoc-sdo.ias.u-psud.fr) that allows users to request data by selecting a date range, the desired wavelengths and a sampling rate (choosing a cadence from 1 minute to 1 day). For each file, users can preview the image (using the Helioviewer tool) or display the header information before downloading the FITS files (with or without Rice-compression). This web interface was built using Sitools2, a tool developed by CNES, the French space agency, and supports most browsers. For more advanced users, a Search/Get Python module is also available at http://sdo.ias.u-psud.fr/python. The users can use it to build more complex yet more powerful queries. We encourage everyone in Europe and beyond to use these new services! Title: LEMUR: Large European module for solar Ultraviolet Research. European contribution to JAXA's Solar-C mission Authors: Teriaca, Luca; Andretta, Vincenzo; Auchère, Frédéric; Brown, Charles M.; Buchlin, Eric; Cauzzi, Gianna; Culhane, J. Len; Curdt, Werner; Davila, Joseph M.; Del Zanna, Giulio; Doschek, George A.; Fineschi, Silvano; Fludra, Andrzej; Gallagher, Peter T.; Green, Lucie; Harra, Louise K.; Imada, Shinsuke; Innes, Davina; Kliem, Bernhard; Korendyke, Clarence; Mariska, John T.; Martínez-Pillet, Valentin; Parenti, Susanna; Patsourakos, Spiros; Peter, Hardi; Poletto, Luca; Rutten, Robert J.; Schühle, Udo; Siemer, Martin; Shimizu, Toshifumi; Socas-Navarro, Hector; Solanki, Sami K.; Spadaro, Daniele; Trujillo-Bueno, Javier; Tsuneta, Saku; Dominguez, Santiago Vargas; Vial, Jean-Claude; Walsh, Robert; Warren, Harry P.; Wiegelmann, Thomas; Winter, Berend; Young, Peter Bibcode: 2012ExA....34..273T Altcode: 2011ExA...tmp..135T; 2011arXiv1109.4301T The solar outer atmosphere is an extremely dynamic environment characterized by the continuous interplay between the plasma and the magnetic field that generates and permeates it. Such interactions play a fundamental role in hugely diverse astrophysical systems, but occur at scales that cannot be studied outside the solar system. Understanding this complex system requires concerted, simultaneous solar observations from the visible to the vacuum ultraviolet (VUV) and soft X-rays, at high spatial resolution (between 0.1'' and 0.3''), at high temporal resolution (on the order of 10 s, i.e., the time scale of chromospheric dynamics), with a wide temperature coverage (0.01 MK to 20 MK, from the chromosphere to the flaring corona), and the capability of measuring magnetic fields through spectropolarimetry at visible and near-infrared wavelengths. Simultaneous spectroscopic measurements sampling the entire temperature range are particularly important. These requirements are fulfilled by the Japanese Solar-C mission (Plan B), composed of a spacecraft in a geosynchronous orbit with a payload providing a significant improvement of imaging and spectropolarimetric capabilities in the UV, visible, and near-infrared with respect to what is available today and foreseen in the near future. The Large European Module for solar Ultraviolet Research (LEMUR), described in this paper, is a large VUV telescope feeding a scientific payload of high-resolution imaging spectrographs and cameras. LEMUR consists of two major components: a VUV solar telescope with a 30 cm diameter mirror and a focal length of 3.6 m, and a focal-plane package composed of VUV spectrometers covering six carefully chosen wavelength ranges between 170 Å and 1270 Å. The LEMUR slit covers 280'' on the Sun with 0.14'' per pixel sampling. In addition, LEMUR is capable of measuring mass flows velocities (line shifts) down to 2 km s - 1 or better. LEMUR has been proposed to ESA as the European contribution to the Solar C mission. Title: Flows in a Small Active Region as Seen by Hinode and SoHO Authors: Boutry, C.; Buchlin, É.; Vial, J. Bibcode: 2012ASPC..454..233B Altcode: We report on a multi-instrument study performed on Active Region 10943 located at Sun center on 20 Feb. 2007. We use XRT images, magnetic field maps from SoHO/MDI and we focus on EIS spectra from which we build maps of the Doppler shift and intensity of Fe XII 195.12 Å. We paid a special attention to the absolute wavelength calibration taking into account the orbital temperature effect. We observe coronal loops between opposite polarities of the region and straight downflows seen in faint regions. Title: Flows at the Edge of an Active Region: Observation and Interpretation Authors: Boutry, C.; Buchlin, E.; Vial, J. -C.; Régnier, S. Bibcode: 2012ApJ...752...13B Altcode: 2012arXiv1204.1377B Upflows observed at the edges of active regions have been proposed as the source of the slow solar wind. In the particular case of Active Region (AR) 10942, where such an upflow has been already observed, we want to evaluate the part of this upflow that actually remains confined in the magnetic loops that connect AR 10942 to AR 10943. Both active regions were visible simultaneously on the solar disk and were observed by STEREO/SECCHI EUVI. Using Hinode/EIS spectra, we determine the Doppler shifts and densities in AR 10943 and AR 10942 in order to evaluate the mass flows. We also perform magnetic field extrapolations to assess the connectivity between AR 10942 and AR 10943. AR 10943 displays a persistent downflow in Fe XII. Magnetic extrapolations including both ARs show that this downflow can be connected to the upflow in AR 10942. We estimate that the mass flow received by AR 10943 areas connected to AR 10942 represents about 18% of the mass flow from AR 10942. We conclude that the upflows observed on the edge of active regions represent either large-scale loops with mass flowing along them (accounting for about one-fifth of the total mass flow in this example) or open magnetic field structures where the slow solar wind originates. Title: Automated detection of filaments from He II images Authors: Buchlin, E.; Mercier, C.; Vial, J. -C. Bibcode: 2012EAS....55..175B Altcode: For space weather applications, it is important to understand filaments evolution and especially their eruptions associated with coronal mass ejections. In view of the cadence and continuity of SDO observations, AIA and HMI offer a unique tool for such a program. Because of the data volume and the requirement of short latency, only an automated detection can be worked out. We present a new method for the automated detection and tracking of filaments, based on the analysis of AIA 30.4 nm He ii images, with the capability to use also the magnetic field measured by HMI. Title: Flows in the Vicinity of Two Active Regions as Seen by Hinode, STEREO, and SoHO Authors: Boutry, C.; Buchlin, E'.; Vial, J.; Régnier, S. Bibcode: 2012ASPC..455...83B Altcode: We observed active region 10943 located at Sun center on February 20, 2007 and we characterized its interactions with active region 10942 by using a multi-instrument comparison between Hinode/XRT and STEREO/SECCHI images, magnetic field maps from SoHO/MDI, and Hinode/EIS spectra from which we built maps of the Doppler shift and the intensity of the Fe XII 195.12 Å line. The results are consistent with some material exchange between the two regions separated by 400″. Title: Kinematics and helicity evolution of a loop-like eruptive prominence Authors: Koleva, K.; Madjarska, M. S.; Duchlev, P.; Schrijver, C. J.; Vial, J. -C.; Buchlin, E.; Dechev, M. Bibcode: 2012A&A...540A.127K Altcode: 2012arXiv1202.4541K
Aims: We aim at investigating the morphology as well as kinematic and helicity evolution of a loop-like prominence during its eruption.
Methods: We used multi-instrument observations from AIA/SDO, EUVI/STEREO and LASCO/SoHO. The kinematic, morphological, geometrical, and helicity evolution of a loop-like eruptive prominence were studied in the context of the magnetic flux rope model of solar prominences.
Results: The prominence eruption evolved as a height-expanding twisted loop with both legs anchored in the chromosphere of a plage area. The eruption process consisted of a prominence activation, acceleration, and a phase of constant velocity. The prominence body was composed of counter-clockwise twisted threads around the main prominence axis. The twist during the eruption was estimated at 6π (3 turns). The prominence reached a maximum height of 526 Mm before contracting to its primary location and was partially reformed in the same place two days after the eruption. This ejection, however, triggered a coronal mass ejection (CME) observed in LASCO C2. The prominence was located in the northern periphery of the CME magnetic field configuration and, therefore, the background magnetic field was asymmetric with respect to the filament position. The physical conditions of the falling plasma blobs were analysed with respect to the prominence kinematics.
Conclusions: The same sign of the prominence body twist and writhe, as well as the amount of twisting above the critical value of 2π after the activation phase indicate that possibly conditions for kink instability were present. No signature of magnetic reconnection was observed anywhere in the prominence body and its surroundings. The filament/prominence descent following the eruption and its partial reformation at the same place two days later suggest a confined type of eruption. The asymmetric background magnetic field possibly played an important role in the failed eruption.

Movies showing the temporal evolution are available in electronic form at http://www.aanda.org Title: Intermittent turbulent dynamo at very low and high magnetic Prandtl numbers Authors: Buchlin, E. Bibcode: 2011A&A...534L...9B Altcode: 2011arXiv1109.4442B Context. Direct numerical simulations of plasmas have shown that the dynamo effect is efficient even at low Prandtl numbers, i.e., the critical magnetic Reynolds number Rmc that is necessary for a dynamo to be efficient becomes smaller than the hydrodynamic Reynolds number Re when Re → ∞.
Aims: We test the conjecture that Rmc tends to a finite value when Re → ∞, and we study the behavior of the dynamo growth factor γ at very low and high magnetic Prandtl numbers.
Methods: We use local and nonlocal shell models of magnetohydrodynamic (MHD) turbulence with parameters covering a much wider range of Reynolds numbers than direct numerical simulations, that is of astrophysical relevance.
Results: We confirm that Rmc tends to a finite value when Re → ∞. As Rm → ∞, the limit to the dynamo growth factor γ in the kinematic regime follows Reβ, and, similarly, the limit for Re → ∞ of γ behaves like Rmβ', with β ≈ β' ≈ 0.4.
Conclusions: Our comparison with a phenomenology based on an intermittent small-scale turbulent dynamo, together with the differences between the growth rates in the different local and nonlocal models, indicate that nonlocal terms contribute weakly to the dynamo effect.

Figures 5 and 6 are available in electronic form at http://www.aanda.org Title: Automated detection of filaments in SDO data Authors: Buchlin, É.; Mercier, C.; Engin, S.; Parenti, S.; Vial, J. -C. Bibcode: 2010sf2a.conf..297B Altcode: Solar eruption can eject billions of tons of plasma to the interplanetary space, with geophysical effects and impacts on human activities. The time constraints for space weather application as well as the huge volume of data that needs to be analyzed, especially since the launch of SDO, imply that the detection of solar filaments and their eruptions must be automated. Most current detection codes use Hα data, which are not available frequently enough for these applications. We present a new detection code that we have developed at IAS and that uses the high spatial and temporal-resolution SDO/AIA He II 30.4 nm data. Title: Nonlinear diffusion equation for Alfvén wave turbulence Authors: Galtier, S.; Buchlin, É. Bibcode: 2010sf2a.conf..299G Altcode: We discuss about the possibility to derive rigorously a nonlinear diffusion equation for incompressible MHD turbulence. The background of the analysis is the asymptotic Alfvén wave turbulence equations from which a differential limit is taken. The result is a universal diffusion-type equation in k-space which describes in a simple way and without free parameter the energy transport perpendicular to the external magnetic field B_0 for transverse fluctuations. It is compatible with both the thermodynamic equilibrium and the finite flux spectra derived by Galtier et al. (2000). This new system offers a powerful description of a wide class of astrophysical plasmas. Title: Nonlinear Diffusion Equations for Anisotropic Magnetohydrodynamic Turbulence with Cross-helicity Authors: Galtier, Sébastien; Buchlin, Éric Bibcode: 2010ApJ...722.1977G Altcode: 2010arXiv1008.3515G Nonlinear diffusion equations of spectral transfer are systematically derived for anisotropic magnetohydrodynamics in the regime of wave turbulence. The background of the analysis is the asymptotic Alfvén wave turbulence equations from which a differential limit is taken. The result is a universal diffusion-type equation in k-space which describes in a simple way and without free parameter the energy transport perpendicular to the external magnetic field B0 for transverse and parallel fluctuations. These equations are compatible with both the thermodynamic equilibrium and the finite flux spectra derived by Galtier et al. it improves therefore the model built heuristically by Lithwick & Goldreich for which only the second solution was recovered. This new system offers a powerful description of a wide class of astrophysical plasmas with non-zero cross-helicity. Title: Automated detection of filaments and their eruptions from AIA and HMI/SDO data Authors: Buchlin, Eric; Mercier, Claude; Vial, Jean-Claude Bibcode: 2010cosp...38.2862B Altcode: 2010cosp.meet.2862B The superior temporal, spatial and spectral range of AIA on SDO provides a completely new view of the dynamic nature of coronal loops. In this paper, we will examine preliminary results of a number of loop examples as their evolution is followed closely in time and space across the AIA filters. The implications of these observational results on the heating and cooling mechanisms operating will be discussed. Title: The SDO data centre at IDOC/MEDOC in France Authors: Parenti, Susanna; Bocchialini, Karine; Soubrie, Elie; Auchere, Frederic; Ballans, Herv; Buchlin, Eric; Gabriel, Alan; Mercier, Claude; Poulleau, Gilles; Vial, Jean-Claude Bibcode: 2010cosp...38.2888P Altcode: 2010cosp.meet.2888P The IDOC/MEDOC centre at the Institut d'Astrophysique Spatiale (IAS, Université Paris 11/CNRS) has a long experience in solar data archiving and distribution, including almost 15 years of data from SOHO, STEREO and TRACE. The center is now expanding its activity and becoming a Pˆle Thématique Solaire of the CNES and INSU/CNRS. Part of the new activities of the centre will be linked to the arrival of the enormous volume of the new SDO data. The center will be one of the three European centers to receive and redistribute the data to the community. It will also be the only European site to permanently store about 10% of the data (mainly from AIA). In continuity with its previous activities, SDO data will be included in the data visualization tool FESTIVAL and it will provide new services, like tools for the solar feature identification (filaments, EUV intensity fluctuations). We will present an overview of the facilities and activities of the centre in relation to the SDO data. Title: Turbulent heating and cooling of coronal loops Authors: Buchlin, Eric; Bradshaw, Stephen J.; Cargill, Peter J.; Velli, Marco Bibcode: 2010cosp...38.2834B Altcode: 2010cosp.meet.2834B In the solar corona, MHD turbulence is likely to be the process producing small scales, at which heating processes become efficient and are able to sustain the high coronal temperatures. However, as these small scales are too small to be observable, comparison between models and observations rely on indirect consequences of the heating. For this reason we build a model of a coronal loop including at the same time the heating processes (anisotropic turbulence driven by Alfvén waves), the cooling processes (convection, conduction, and radiation based on atomic physics), and the forward-modeling of spectroscopic observable variables (such as the evolution of UV spectral line profiles). We show that including the feedback of the cooling on the heating processes is important in such models. The heating is intermittent and sufficient to heat the loop at temperatures of more than a million degrees, with realistic values of the amplitude of the forcing (corresponding to motions of the photospheric footpoints of the loop). We discuss the importance of small scale heating in the corona and the relevance of its description by our model. Title: Turbulence in the Sub-Alfvénic Solar Wind Driven by Reflection of Low-Frequency Alfvén Waves (Invited) Authors: Verdini, A.; Velli, M. M.; Buchlin, E. Bibcode: 2009AGUFMSH51C..07V Altcode: We study the formation and evolution of a turbulent spectrum of Alfvén waves driven by reflection off the solar wind density gradients, starting from the coronal base up to 17 solar radii, well beyond the Alfvénic critical point, and using a 2D shell model to describe nonlinear interactions. We find that the turbulent spectra are influenced by the nature of reflected waves. Close to the base, these give rise to a flatter and steeper spectrum for the outgoing and reflected waves respectively. At higher heliocentric distance both spectra evolve toward an asymptotic Kolmogorov spectrum. The turbulent dissipation is found to account for at least half of the heating required to sustain the background imposed solar wind and its shape is found to be determined by the reflection-determined turbulent heating below 1.5 solar radii. Therefore reflection and reflection-driven turbulence are shown to play a key role in the acceleration of the fast solar wind and origin of the turbulent spectrum found at 0.3 AU in the heliosphere. Title: Electron density in the quiet solar coronal transition region from SoHO/SUMER measurements of S VI line radiance and opacity Authors: Buchlin, E.; Vial, J. -C. Bibcode: 2009A&A...503..559B Altcode: 2009arXiv0906.1367B Context: The steep temperature and density gradients that are measured in the coronal transition region challenge the model interpretation of observations.
Aims: We derive the average electron density < ne > in the region emitting the S vi lines. We use two different techniques, which allow us to derive linearly-weighted (opacity method) and quadratically-weighted (emission measure method) electron density along the line-of-sight, to estimate a filling factor or derive the layer thickness at the formation temperature of the lines.
Methods: We analyze SoHO/SUMER spectroscopic observations of the S vi lines, using the center-to-limb variations in radiance, the center-to-limb ratios of radiance and line width, and the radiance ratio of the 93.3-94.4 nm doublet to derive the opacity. We also use the emission measure derived from radiance at disk center.
Results: We derive an opacity τ0 at S vi 93.3 nm line center of the order of 0.05. The resulting average electron density < {ne}>, under simple assumptions concerning the emitting layer, is 2.4 × 1016 m-3 at T = 2 × 105 K. This value is higher than (and inconsistent with) the values obtained from radiance measurements (2 × 1015 m-3). The last value corresponds to an electron pressure of 10-2 Pa. Conversely, taking a classical value for the density leads to a too high value of the thickness of the emitting layer.
Conclusions: The pressure derived from the emission measure method compares well with previous determinations. It implies a low opacity of between 5 × 10-3 and 10-2. It remains unexplained why a direct derivation leads to a much higher opacity, despite tentative modeling of observational biases. Further measurements in S vi and other lines emitted at a similar temperature should be completed, and more realistic models of the transition region need to be used. Title: Turbulence in the Sub-Alfvénic Solar Wind Driven by Reflection of Low-Frequency Alfvén Waves Authors: Verdini, A.; Velli, M.; Buchlin, E. Bibcode: 2009ApJ...700L..39V Altcode: 2009arXiv0905.2618V We study the formation and evolution of a turbulent spectrum of Alfvén waves driven by reflection off the solar wind density gradients, starting from the coronal base up to 17 solar radii, well beyond the Alfvénic critical point. The background solar wind is assigned and two-dimensional shell models are used to describe nonlinear interactions. We find that the turbulent spectra are influenced by the nature of the reflected waves. Close to the base, these give rise to a flatter and steeper spectrum for the outgoing and reflected waves, respectively. At higher heliocentric distance both spectra evolve toward an asymptotic Kolmogorov spectrum. The turbulent dissipation is found to account for at least half of the heating required to sustain the background imposed solar wind and its shape is found to be determined by the reflection-determined turbulent heating below 1.5 solar radii. Therefore, reflection and reflection-driven turbulence are shown to play a key role in the acceleration of the fast solar wind and origin of the turbulent spectrum found at 0.3 AU in the heliosphere. Title: Reflection Driven MHD Turbulence in the Solar Atmosphere and Wind Authors: Verdini, A.; Velli, M.; Buchlin, E. Bibcode: 2009EM&P..104..121V Altcode: 2008EM&P..tmp...33V Alfvénic turbulence is usually invoked and used in many solar wind models (Isenberg and Hollweg, 1982, J. Geophys. Res. 87:5023; Tu et al. 1984, J. Geophys. Res. 89:9695; Hu et al. 2000, J. Geophys. Res. 105:5093; Li 2003, Astron. Astrphys. 406:345; Isenberg 2004, J. Geophys. Res. 109:3101) as a process responsible for the transfer of energy, released at large scale in the photosphere, towards small scale in the corona, where it is dissipated. Usually an initial spectrum is prescribed since the closest constraint to the spectrum is given by Helios measurements at 0.3 AU. With this work we intend to study the efficiency of the reflection as a driver for the nonlinear interactions of Alfvén waves, the development of a turbulent spectrum and its evolution in the highly stratified solar atmosphere inside coronal holes. Our main finding is that the perpendicular spectral slope changes substantially at the transition region because of the steep density gradient. As a result a strong turbulent heating occurs, just above the transition region, as requested by current solar wind models. Title: Turbulence in anisotropic heliospheric plasmas Authors: Buchlin, E.; Verdini, A.; Cargill, P. J.; Velli, M. Bibcode: 2008sf2a.conf..547B Altcode: An alternative approach to Direct Numerical Simulations (DNS) of Magnetohydrodynamics (MHD) is presented, providing insight into the statistical properties of highly-turbulent, intermittent, anisotropic MHD turbulence: a set of shell-models coupled by Alfvén waves travelling along the axial magnetic field and which interact non-linearly, producing perpendicular fluctuations of the fields at small scales. This model can be applied to different physical situations; we present the cases of heating in solar coronal loops, and of turbulence in open coronal regions at the base of the solar wind. Title: Spectroscopic Hinode Observables from Turbulent Heating and Cooling of Coronal Loops Authors: Buchlin, É.; Cargill, P. J.; Bradshaw, S. J.; Velli, M. Bibcode: 2008ASPC..397...83B Altcode: We present a model of coronal loop turbulence allowing the fast computation of heating in a loop at high Reynolds numbers. We also consider the coupling of both heating and cooling processes in loops, including for the first time a feedback of the cooling on the heating: the heating computed by the shell-models used as an input of a hydrodynamic model of a loop with thermal conduction and a self-consistent treatment of radiation. We forward-model spectroscopic variables that can be compared to Hinode observations. Title: Properties of the quiet solar coronal transition region from full-Sun SoHO/SUMER S VI Authors: Buchlin, E.; Vial, J. Bibcode: 2008ESPM...122.117B Altcode: A series of full-Sun SoHO/SUMER observations of the quiet Sun in the transition region lines S VI 933 and 944 (as well as Ly epsilon) has been performed during year 1996. We use this unique data set to derive the opacity of the S VI lines by different methods (following Dumont et al. 1983), taking advantage from the availability of full-Sun data and

of the S VI doublet: 1. using the center-to-limb variations of S VI 933 radiance and peak spectral radiance, 2. using the center-to-limb variations of S VI 933 line width and radiance, and 3. using the S VI 944 - 933 radiance or spectral radiance ratio at disk center. We then deduce an average value for the density in the S VI emitting region (in the coronal transition region). By comparing this value to the average square density obtained by an Emission Measure analysis, we get a tentative estimate of the filling factor in this region. Title: Alfvénic Turbulence and the Acceleration of the Fast Solar Wind Authors: Verdini, A.; Velli, M.; Buchlin, E. Bibcode: 2008ESPM...12.3.69V Altcode: Alfvenic turbulence is usually invoked and used in many solar wind models (Isenberg & Hollweg 1982, Tu et al. 1984, Hu et al. 2000, Li 2003, Isenberg 2004) as a process responsible for the transfer of energy released at large scales in the photosphere towards small scales in the corona, where it is dissipated. Usually an initial spectrum is prescribed since its closest constraint is given by Helios measurements at 0.3 AU.

With this work we intend to study the efficiency of the reflection as a driver for the nonlinear interactions of Alfven waves, the eventual development of a turbulent spectrum and its evolution in the highly stratified solar atmosphere inside coronal holes.

We start imposing an upcoming flux of Alfven waves in a limited range of perpendicular wave numbers, at the base of the corona.

Open boundary conditions allow the reflected waves to leave the domain form below and to be advected by the solar wind outside the top boundary. The nonlinear interaction in planes perpendicular to that of propagation (assumed to be radial) are treated with a 2D shell model, so that large Reynolds numbers are reached.

Continuous interactions of counter propagating waves form a turbulent spectrum in the low corona, before the sonic point, in very short timescales (compared to the propagation timescales).

Both the location and the value of the maximum of the dissipation (per unit mass) scale with the rms amplitude of the velocity fluctuations at the coronal base (delta u), while they are less sensitive to the frequency of the input flux of Alfven waves, provided it is small enough to power the turbulent cascade by means of reflection.

For values of delta u in agreement with observational constraints, the turbulent dissipation achieves levels capable of sustaining a fast solar wind, with the maximum dissipation located at 2 solar radii, just below the sonic point.

Despite the back reaction of the solar wind is not taken into account, this model shows that, under reasonable assumptions, a turbulent spectrum forms in the corona and it is able to sustain the heating and acceleration of the fast solar wind. Finally, the scaling laws obtained with this simplified 2D turbulence can be further constrained in order to include this mechanism of reflection driven turbulence in more complex solar wind models. Title: Profiles of heating in turbulent coronal magnetic loops Authors: Buchlin, E.; Cargill, P. J.; Bradshaw, S. J.; Velli, M. Bibcode: 2007A&A...469..347B Altcode: 2007astro.ph..2748B Context: The location of coronal heating in magnetic loops has been the subject of a long-lasting controversy: does it occur mostly at the loop footpoints, at the top, is it random, or is the average profile uniform?
Aims: We try to address this question in model loops with MHD turbulence and a profile of density and/or magnetic field along the loop.
Methods: We use the Shell-Atm MHD turbulent heating model described in Buchlin & Velli (2007, ApJ, 662, 701), with a static mass density stratification obtained by the HydRad model (Bradshaw & Mason 2003, A&A, 401, 699). This assumes the absence of any flow or heat conduction subsequent to the dynamic heating.
Results: The average profile of heating is quasi-uniform, unless there is an expansion of the flux tube (non-uniform axial magnetic field) or the variation of the kinetic and magnetic diffusion coefficients with temperature is taken into account: in the first case the heating is enhanced at footpoints, whereas in the second case it is enhanced where the dominant diffusion coefficient is enhanced.
Conclusions: These simulations shed light on the consequences on heating profiles of the complex interactions between physical effects involved in a non-uniform turbulent coronal loop. Title: Shell Models of RMHD Turbulence and the Heating of Solar Coronal Loops Authors: Buchlin, E.; Velli, M. Bibcode: 2007ApJ...662..701B Altcode: 2006astro.ph..6610B A simplified nonlinear numerical model for the development of incompressible magnetohydrodynamics in the presence of a strong magnetic field B∥ and stratification, nicknamed ``Shell-Atm,'' is presented. In planes orthogonal to the mean field, the nonlinear incompressible dynamics is replaced by two-dimensional shell models for the complex variables u and b, allowing one to reach large Reynolds numbers while at the same time carrying out sufficiently long integrations to obtain good statistics at moderate computational cost. The shell models of different planes are coupled by Alfvén waves propagating along B∥. The model may be applied to open or closed magnetic field configurations where the axial field dominates and the plasma pressure is low; here we apply it to the specific case of a magnetic loop of the solar corona heated by means of turbulence driven by photospheric motions, and we use statistics for its analysis. The Alfvén waves interact nonlinearly and form turbulent spectra in the directions perpendicular and, through propagation, also parallel to the mean field. A heating function is obtained and shown to be intermittent; the average heating is consistent with values required for sustaining a hot corona and is proportional to the aspect ratio of the loop to the -1.5 power, and characteristic properties of heating events are distributed as power laws. Cross-correlations show a delay of dissipation compared with energy content. Title: Multiscale Hall-Magnetohydrodynamic Turbulence in the Solar Wind Authors: Galtier, Sébastien; Buchlin, Eric Bibcode: 2007ApJ...656..560G Altcode: 2006astro.ph.10759G The spectra of solar wind magnetic fluctuations exhibit a significant power-law steepening at frequencies f>1 Hz. The origin of this multiple scaling is investigated through dispersive Hall magnetohydrodynamics. We perform three-dimensional numerical simulations in the framework of a highly turbulent shell model and show that the large-scale magnetic fluctuations are characterized by a k-5/3-type spectrum that steepens at scales smaller than the ion inertial length di, to k-7/3 if the magnetic energy overtakes the kinetic energy, or to k-11/3 in the opposite case. These results are in agreement both with a heuristic description à la Kolmogorov and with the range of power-law indices found in the solar wind. Title: Coronal Turbulence And Intermittency From Solar Orbiter Observations Authors: Buchlin, É.; Vial, J. -C. Bibcode: 2007ESASP.641E..23B Altcode: Turbulent motions and magnetic fields are a key component of coronal heating mechanisms. They are indeed likely to produce the small scales at which the mechanisms such as reconnection are efficient enough. The properties of turbulence (and the associated intermit- tency) may thus have an influence on the energy dissipation in the corona, and need to be characterized from observations. Although turbulence is omnipresent from the Sun to the heliosphere, good observations of MHD turbulence have not yet been performed in the corona, in lines emitted at high temperature, where the heating actually occurs. We propose a study of coordinated EUS- EUI-VIM observations, with better resolution and counting statistics than ever before, whose main goal is to get and interpret the spatial statistics (spectra and structure functions) of the velocity field in lines emitted at high temperatures (log10 T ≥ 6.4), together with the plasma and magnetic environment of the observed region. These statistics will help us understand the precise role of coronal turbulence in the coronal heating processes. Title: Modeling the Radiative Signatures of Turbulent Heating in Coronal Loops Authors: Parenti, S.; Buchlin, E.; Cargill, P. J.; Galtier, S.; Vial, J. -C. Bibcode: 2006ApJ...651.1219P Altcode: The statistical properties of the radiative signature of a coronal loop subject to turbulent heating obtained from a three-dimensional (3D) magnetohydrodynamics (MHD) model are studied. The heating and cooling of a multistrand loop is modeled and synthetic spectra for Fe XII 195.12, Fe XV 284.163, and Fe XIX 1118.06 Å are calculated, covering a wide temperature range. The results show that the statistical properties of the thermal and radiative energies partially reflect those of the heating function in that power-law distributions are transmitted, but with very significant changes in the power-law indices. There is a strong dependence on the subloop geometry. Only high-temperature radiation (~107 K) preserves reasonably precise information on the heating function. Title: Alfvén Waves and Turbulence in the Inner Corona Authors: Verdini, A.; Buchlin, E.; Velli, M. Bibcode: 2006ESASP.617E.115V Altcode: 2006soho...17E.115V No abstract at ADS Title: Looking for Signature of Coronal Heating in the Radiative Emission of a Coronal Loop Authors: Parenti, S.; Buchlin, E.; Cargill, P. J.; Caltier, S.; Vial, J. -C. Bibcode: 2006ESASP.617E.104P Altcode: 2006soho...17E.104P No abstract at ADS Title: A statistical study of SUMER spectral images: events, turbulence, and intermittency Authors: Buchlin, E.; Vial, J. -C.; Lemaire, P. Bibcode: 2006A&A...451.1091B Altcode: 2005astro.ph.11042B We analyze a series of full-Sun observations performed with the SoHO/SUMER instrument between March and October 1996. Some parameters (radiance, shift and width) of the S vi 93.3 nm , S vi 94.4 nm , and Ly \varepsilon line profiles were computed on board. Radiances and line-of-sight velocities in a large central region of the Sun are studied statistically: distributions of solar structures, field Fourier spectra and structure functions are obtained. The structures have distributions with power-law tails, the Fourier spectra of the radiance fields also display power laws, and the normalized structure functions of the radiance and velocity fields increase at small scales. These results support the idea of the existence of small scales, created by turbulence, and of intermittency of the observed fields. These properties may provide insight into the processes needed for heating the transition region, or, if confirmed in the corona, the corona itself. The difficulties encountered in this analysis, especially for the velocity data, underline the need for sensitive ultraviolet imaging spectrometers. Title: Heating of the solar corona Authors: Buchlin, E. Bibcode: 2006sf2a.conf..529B Altcode: The mechanisms of transport and dissipation of energy in the corona are the subject of a long-lasting controversy in solar physics, with implications on Solar-Terrestrial physics. I review some classical models of wave or current dissipation, and I discuss the role of turbulence, how it can help providing the small scales at which dissipation is more efficient, what observational and computational difficulties arise, what is being done to overcome them, and what new challenges we meet. Title: Reduced MHD and Shell-Model Simulations of Coronal Heating in Magnetized Loops: Scaling Laws. Authors: Velli, M.; Rappazzo, F.; Buchlin, E.; Einaudi, G. Bibcode: 2005AGUFMSH13B..03V Altcode: We present direct magnetohydrodynamic (MHD) simulations modeling the heating of coronal loops in the solar atmosphere via the tangling of coronal field lines by photospheric footpoint motions within the framework of reduced MHD. We carry out long-time 3D simulations with the highest resolutions to date and compare them to simpler shell-model simulations, in which the non-linear couplings in wave-number space are drastically simplified. The latter reach much larger Reynolds numbers but can not describe the dynamics in physical space, which is driven by the reconnection of induced coronal magnetic fields. In the direct numerical simulations, we reach resolutions sufficient to derive scaling properties with Reynolds numbers, loop length, and ratio of photospheric velocity to coronal Alfven speeds. Line-tying of the axial field lines plays a significant role by inhibiting coalescence and inverse cascades in the loop cross-sections, which dominate dynamics in 2D models. To examine the role of line-tying simulations including gradients in the density from the photosphere to the corona are also included. Shell-model calculations are carried out for much longer time-scales, sufficient to calculate the statistical properties of heating. The scaling properties derived from the shell models and from reduced MHD are compared and contrasted and on this basis we discuss the required role of emerging flux, neglected here, in coronal heating. Title: Radiative Signatures of Coronal Loops Submitted to Turbulent Heating Authors: Parenti, S.; Buchlin, E.; Galtier, S.; Vial, J. -C. Bibcode: 2005ESASP.592..523P Altcode: 2005soho...16E..97P; 2005ESASP.592E..97P No abstract at ADS Title: Shell-Model Simulations of MHD in a Solar Coronal Loop Authors: Buchlin, É.; Velli, M. Bibcode: 2005ESASP.592..153B Altcode: 2005soho...16E..23B; 2005ESASP.592E..23B No abstract at ADS Title: Influence of the definition of dissipative events on their statistics Authors: Buchlin, E.; Galtier, S.; Velli, M. Bibcode: 2005A&A...436..355B Altcode: 2004astro.ph.11592B A convenient and widely used method to study the turbulent plasma in the solar corona is to examine statistics of properties of events (or structures) associated to flares either in observations or in numerical simulations. Numerous papers have followed such a methodology, using different definitions of an event, but the reasons behind the choice of a particular definition is very rarely discussed. We give here a comprehensive set of possible event definitions starting from a one-dimensional data set such as a time-series of energy dissipation. Each definition is then applied to a time-series of energy dissipation obtained from simulations of a shell-model of magnetohydrodynamic turbulence, or from a new model of coupled shell-models designed to represent a magnetic loop in the solar corona. We obtain distributions of the peak dissipation power, total energy, duration and waiting-time associated with each definition. These distributions are then investigated and compared, and the influence of the definition of an event on the statistics is discussed. In particular, power-law distributions are more likely to appear when using a threshold. The sensitivity of the distributions to the definition of an event seems also to be weaker for events found in a highly intermittent time series. Some implications for statistical results obtained from observations are discussed. Title: Shell-Model Simulations of MHD in a Solar Coronal Loop Authors: Buchlin, E.; Velli, M. Bibcode: 2005AGUSMSP14A..05B Altcode: Statistics may be necessary to keep a global view of the complexity of astrophysical turbulence, in particular the effects of non-linear interactions over a wide range of scales. However, from the numerical point of view, a statistical approach to turbulence has the contradictory needs for computing speed and for a good description of the solutions of the MHD equations. This problem can be addressed by simplified models like cellular automata or shell-models. In the shell-models, the low number of well-chosen modes allows to keep the most possible of the complex and non-linear physics of the MHD equations while running sufficiently fast to produce statistics of fields, of structures, and of "events". The model we present here is designed to represent a magnetic loop in the solar corona. It consists of a pile of shell-models, which allows to reach a wide range of wavenumbers in cross-sections of the loop and model the non-linear couplings between these modes. The shell-models are also coupled by Alfvén waves propagating along the loop. We study the statistical properties of intermittent energy dissipation and of the velocity and magnetic fields produced by this model. These statistical properties can be compared to statistics issued from observations, like structure functions or events distributions. Title: Simplified Simulations of MHD in a Coronal Loop by Coupled Shell-Models Authors: Buchlin, É.; Velli, M.; Galtier, S. Bibcode: 2004ESASP.575..120B Altcode: 2004soho...15..120B No abstract at ADS Title: Modelling the Radiative Signatures of Turbulent Heating in Coronal Loops Authors: Parenti, S.; Buchlin, E.; Galtier, S.; Vial, J. -C. Bibcode: 2004ESASP.575..497P Altcode: 2004soho...15..497P No abstract at ADS Title: Simplified simulations of MHD Authors: Buchlin, É.; Velli, Marco; Galtier, Sébastien; Vial, Jean-Claude Bibcode: 2004sf2a.conf...91B Altcode: 2004sf2a.confE.334B Because of the wide range of scales involved in MHD turbulence, a statistical approach may become necessary to keep a global view of this complex phenomenon. In particular, in the framework of the heating of the solar corona, the smallest events are not directly detectable by the current instruments but may be integrated to a statistical study. From the numerical point of view, the contradictory needs for computing speed and good description of MHD solutions may be addressed by simplified models, which keep the most possible of the complex and non-linear physics of the MHD equations but run sufficiently fast to produce statistics of fields, of structures, and of "events". We propose two such models which have been originally developed to represent coronal loops (with forcing and Alfvén wave reflection at the loop's foot-points), but which may be adapted to represent any region with a dominant large-scale magnetic field. The first model consists of a set of cellular automata, in which the non-linear terms of the MHD equations are modelled by a threshold dynamics on current density (Buchlin et al. A&A, 2003). In the second model, the cellular automata are replaced by shell-models of MHD, so as to reach a greater range of wavenumbers and to model more realistically the non-linear couplings between modes at different scales. The results obtained with these models will be presented and consequences of this study for observational statistics and for theory of MHD turbulence will be discussed. Title: Signatures and models of small-scale turbulent coronal heating Authors: Buchlin, E. Bibcode: 2004PhDT........41B Altcode: In solar physics, the complexity and small scales generated by magnetohydrodynamic (MHD) turbulence suggest to tackle the problem of the heating of the corona using statistics. We use therefore spectra of the fields, distributions of probability of structures or events, and structure functions, to analyze observations and numerical simulations, and to detect common signatures of turbulence, intermittency, and small-scale heating.

Our numerical simulations model a coronal magnetic loop, which is excited by the motions of the photosphere, and in which non-linearly interacting Alfvén waves propagate. As we need statistics, we need to simplify these interactions: we have chosen to model these interactions by cellular automata on one hand, and then by shell-models on the other hand. The results of these loop models are consistent with observations, and allow to understand some observational effects. Furthermore, signatures of intermittency can be found in the shell-model-based model, which includes a better representation of the non-linear terms of MHD than the cellular automata model. The analysis of these models and of their parametric behavior gives some information on the heating mechanisms in the corona and some clues about the interpretation of observations.

We also analyze the intensity and velocity fields observed in 1996 on the quiet Sun with the SoHO/SUMER spectrograph. The statistics of these fields (mainly the intensity field, as the velocity field is regrettably too noisy) acquaint us with the turbulent nature of the corona and with its intermittency.

The discrepancy between the distributions of events observed by different authors in the corona leads us finally to interest ourselves to the different possible definitions of an event. We give a comprehensive set of such definitions and we compare them, using lowly and highly intermittent signals. Title: Simplified simulations of non-linear interactions in an anisotropic plasma Authors: Buchlin, E.; Velli, M.; Galtier, S. Bibcode: 2004cosp...35.3555B Altcode: 2004cosp.meet.3555B Statistics may be necessary to keep a global view of the complexity of astrophysical turbulence, in particular the effects of non-linear interactions over a wide range of scales. However, from the numerical point of view, a statistical approach to turbulence has the contradictory needs for computing speed and for a good description of the solutions of the MHD equations. This problem can be addressed by simplified models, for example models with a reduced number of well-chosen modes, which keep the most possible of the complex and non-linear physics of the MHD equations but run sufficiently fast to produce statistics of fields, of structures, and of "events". The model we present here was orginally designed to represent a magnetic loop in the solar corona, but may in fact help to understand turbulence in any region with a dominant magnetic field ěc{B}_0. It consists of a pile of shell-models, which allow to reach a wide range of wavenumbers in the directions orthogonal to ěc{B}_0 and model the non-linear couplings between these modes. The shell-models are also coupled by Alfvén waves propagating along ěc{B}_0. We study the statistical properties of energy dissipation and of the velocity and magnetic fields produced by this model. Title: Signatures et modélisations du chauffage coronal turbulent à micro-échelles Title: Signatures et modélisations du chauffage coronal turbulent à micro-échelles Title: Signatures and modeling of turbulent coronal heating at micro-scales; Authors: Buchlin, Éric Bibcode: 2004PhDT.......315B Altcode: No abstract at ADS Title: Statistical Study of SOHO/SUMER Full-Sun Images Authors: Buchlin, E.; Vial, J. -C.; Lemaire, P.; Galtier, S. Bibcode: 2004ESASP.547..337B Altcode: 2004soho...13..337B A series of full-Sun observations was performed with the SoHO/SUMER instrument between March and October 1996. Some moments of the S VI 93.3nm, S VI 94.4nm, and Ly line profiles were computed on-board. Intensities and line-of-sight velocities in a large central region of the Sun are studied statistically: histograms of intensities are computed, as well as histograms of total intensities of "events", and structure functions of the intensity field. Some statistics of velocities are the first to be obtained from observational data. The aim is to compare these statistics to results previously obtained with SoHO/EIT and by numerical simulations of MHD. Signatures of turbulent intermittency are also researched. Title: Statistical properties of turbulence and intermittency in the solar corona observed in EUV Authors: Buchlin, E.; Vial, J. -C.; Lemaire, P. Bibcode: 2004cosp...35.3556B Altcode: 2004cosp.meet.3556B Statistical properties of the fields observed on the Sun in EUV may help to understand turbulence in the solar corona and give clues to the processes involved in the heating of the corona to millions of degrees. In this study, we use a series of full-Sun images obtained in 1996 by the SUMER spectroheliograph on SoHO. Each observation consists of eight limb-to-limb raster scans in the lines Ly ɛ, S VI 193.3 nm, and S VI 194.4 nm. Intensities, Doppler velocity shifts and line widths were computed on-board. A context spectrum was measured for each observation. Intensities and line-of-sight velocities data in a large central region of the Sun are then studied statistically: histograms of data values and of events, structure functions, and other statistics are computed. They are compared to results obtained by imaging instruments like SoHO/EIT and to numerical simulations of MHD. Structure functions of the velocity field reveal that turbulence in the corona may be intermittent. Title: A solar cellular automata model issued from reduced MHD Authors: Buchlin, E.; Aletti, V.; Galtier, S.; Velli, M.; Vial, J. -C. Bibcode: 2003AIPC..679..335B Altcode: A three-dimensional cellular automata (CA) model inspired by the reduced magnetohydrodynamic equations is presented to describe impulsive events generated along a coronal magnetic loop. It consists of a set of planes, distributed along the loop, between which the information propagates through Alfvén waves. Statistical properties in terms of power laws are obtained in agreement with SoHO observations of X-ray bright points of the quiet Sun. Physical meaning and limits of the model are discussed. Title: A simplified numerical model of coronal energy dissipation based on reduced MHD Authors: Buchlin, E.; Aletti, V.; Galtier, S.; Velli, M.; Einaudi, G.; Vial, J. -C. Bibcode: 2003A&A...406.1061B Altcode: 2002astro.ph.12444B A 3D model intermediate between cellular automata (CA) models and the reduced magnetohydrodynamic (RMHD) equations is presented to simulate solar impulsive events generated along a coronal magnetic loop. The model consists of a set of planes distributed along a magnetic loop between which the information propagates through Alfvén waves. Statistical properties in terms of power-laws for energies and durations of dissipative events are obtained, {and their} agreement with X-ray and UV flares observations {is discussed}. The existence of observational biases is {also} discussed. Title: Distributions of Coronal Events: Simulations and Event Definitions Authors: Buchlin, Éric; Galtier, Sébastien; Velli, Marco; Vial, Jean-Claude Bibcode: 2003ANS...324..109B Altcode: 2003ANS...324..P15B No abstract at ADS Title: A Solar Cellular Automata Model Issued From Reduced MHD Authors: Buchlin, E.; Aletti, V.; Galtier, S.; Velli, M.; Vial, J. -C. Bibcode: 2002sf2a.conf..129B Altcode: A three-dimensional cellular automata model inspired by the reduced magnetohydrodynamic equations is presented to describe impulsive events generated along a coronal magnetic loop. It consists of a set of planes, distributed along the loop, between which the information propagates through Alfven waves. Statistical properties in terms of power laws are obtained in agreement with SoHO observations of X-ray bright points of the quiet Sun. Physical meaning and limits of the model are discussed. Title: Recent SOHO/SUMER Observations of a Polar and Equatorial Coronal Hole Authors: Buchlin, E.; Hassler, D. M. Bibcode: 2000SPD....31.0201B Altcode: 2000BAAS...32..810B SUMER observations have provided new insight into the structure of the source region of the solar wind, and its relationship to the chromospheric magnetic network. Specifically, velocity maps in Ne VIII, formed at the base of the corona, show a relationship between outflow velocity and the underlying network structure (Hassler et al., Science, 1999). However, the time cadence of these observations had to be increased to tell whether these velocity signatures correspond to steady state or transient flows. We present two new observing campaigns that we have organized and performed in 1999 (March 8 and November 3-8) to address this outstanding question while preserving sufficient FOV, involving observations from SOHO (SUMER, EIT, MDI, CDS), TRACE and Kitt Peak. Preliminary analysis of the observations from March 8, 1999 suggest that the majority of the observed flows in both the south polar coronal hole and the equatorial quiet Sun region are relatively quiescent (or slowly evolving) on the time scale of the SUMER observations of 2 hours. However, one significant high speed transient flow (20-30 km/s) was identified in a SUMER scan at the south polar coronal hole, and corresponds to an explosive event or jet observed by TRACE in Fe IX/X 171 which lasted less than an hour. During the November campaign, extensive, coordinated observations were made of an equatorial coronal hole which began on the East limb and rotated across the MDI high resolution FOV at central meridian. Complete coronal hole scans (5 to 9 hours long), several series of three 2-hour long scans and time series with 1 min cadence were made. Intensity, line-of-sight velocity, and line width maps will be presented for emission lines formed at three different heights in the solar atmosphere (Si II 1533, C IV 1548, and Ne VIII 770). This work has been funded in part by NASA under grant NAG5-7815 to Southwest Research Institute.