Author name code: berghmans ADS astronomy entries on 2022-09-14 author:"Berghmans, David" ------------------------------------------------------------------------ Title: Two-Spacecraft Detection of Short-period Decayless Kink Oscillations of Solar Coronal Loops Authors: Zhong, Sihui; Nakariakov, Valery M.; Kolotkov, Dmitrii Y.; Verbeeck, Cis; Berghmans, David Bibcode: 2022arXiv220901917Z Altcode: Decayless kink oscillations of an ensemble of loops are captured simultaneously by the High Resolution Imager (HRI) of the Extreme Ultraviolet Imager (EUI) and the Atmospheric Imaging Assembly (AIA) from 22:58 UT on 5 November to 00:27 UT on 6 November 2021. Oscillations are analysed by processing image sequences taken by the two instruments with a motion magnification technique. The analysed loops are around 51 Mm in length, and oscillate with short periods of 1-3 min (1.6 min in average) and displacement amplitudes of 27-83 km. The signals recorded by AIA are delayed by 66 s as compared to HRI, which coincides with the light travel time difference from the Sun to each instrument. After correction of this time difference, the cross-correlation coefficient between the signals from the two data varies from 0.82 to 0.97, indicating that they are well consistent. This work confirms that HRI sees the same oscillations as AIA, which is the necessary first step before proceeding to the detection of shorter time scales by EUI. In addition, our results indicate the robustness of the de-jittering procedure in the study of kink oscillations with HRI. 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: Coronal mass ejection followed by a prominence eruption and a plasma blob as observed by Solar Orbiter Authors: Bemporad, A.; Andretta, V.; Susino, R.; Mancuso, S.; Spadaro, D.; Mierla, M.; Berghmans, D.; D'Huys, E.; Zhukov, A. N.; Talpeanu, D. -C.; Colaninno, R.; Hess, P.; Koza, J.; Jejčič, S.; Heinzel, P.; Antonucci, E.; Da Deppo, V.; Fineschi, S.; Frassati, F.; Jerse, G.; Landini, F.; Naletto, G.; Nicolini, G.; Pancrazzi, M.; Romoli, M.; Sasso, C.; Slemer, A.; Stangalini, M.; Teriaca, L. Bibcode: 2022A&A...665A...7B Altcode: 2022arXiv220210294B Context. On 2021 February 12, two subsequent eruptions occurred above the western limb of the Sun, as seen along the Sun-Earth line. The first event was a typical slow coronal mass ejection (CME), followed ∼7 h later by a smaller and collimated prominence eruption, originating south of the CME, followed by a plasma blob. These events were observed not only by the SOHO and STEREO-A missions, but also by the suite of remote-sensing instruments on board Solar Orbiter.
Aims: We show how data acquired by the Full Sun Imager (FSI), the Metis coronagraph, and the Heliospheric Imager (HI) from the Solar Orbiter perspective can be combined to study the eruptions and different source regions. Moreover, we show how Metis data can be analyzed to provide new information about solar eruptions.
Methods: Different 3D reconstruction methods were applied to the data acquired by different spacecraft, including remote-sensing instruments on board Solar Orbiter. Images acquired by the two Metis channels in the visible light (VL) and H I Ly-α line (UV) were combined to derive physical information about the expanding plasma. The polarization ratio technique was also applied for the first time to Metis images acquired in the VL channel.
Results: The two eruptions were followed in 3D from their source region to their expansion in the intermediate corona. By combining VL and UV Metis data, the formation of a post-CME current sheet (CS) was followed for the first time in the intermediate corona. The plasma temperature gradient across a post-CME blob propagating along the CS was also measured for the first time. Application of the polarization ratio technique to Metis data shows that by combining four different polarization measurements, the errors are reduced by ∼5 − 7%. This constrains the 3D plasma distribution better.

Movies associated to Figs. 4-7 are available at https://www.aanda.org Title: Defining the Middle Corona Authors: West, Matthew J.; Seaton, Daniel B.; Wexler, David B.; Raymond, John C.; Del Zanna, Giulio; Rivera, Yeimy J.; Kobelski, Adam R.; DeForest, Craig; Golub, Leon; Caspi, Amir; Gilly, Chris R.; Kooi, Jason E.; Alterman, Benjamin L.; Alzate, Nathalia; Banerjee, Dipankar; Berghmans, David; Chen, Bin; Chitta, Lakshmi Pradeep; Downs, Cooper; Giordano, Silvio; Higginson, Aleida; Howard, Russel A.; Mason, Emily; Mason, James P.; Meyer, Karen A.; Nykyri, Katariina; Rachmeler, Laurel; Reardon, Kevin P.; Reeves, Katharine K.; Savage, Sabrina; Thompson, Barbara J.; Van Kooten, Samuel J.; Viall, Nicholeen M.; Vourlidas, Angelos Bibcode: 2022arXiv220804485W Altcode: The middle corona, the region roughly spanning heliocentric altitudes from $1.5$ to $6\,R_\odot$, encompasses almost all of the influential physical transitions and processes that govern the behavior of coronal outflow into the heliosphere. Eruptions that could disrupt the near-Earth environment propagate through it. Importantly, it modulates inflow from above that can drive dynamic changes at lower heights in the inner corona. Consequently, this region is essential for comprehensively connecting the corona to the heliosphere and for developing corresponding global models. Nonetheless, because it is challenging to observe, the middle corona has been poorly studied by major solar remote sensing missions and instruments, extending back to the Solar and Heliospheric Observatory (SoHO) era. Thanks to recent advances in instrumentation, observational processing techniques, and a realization of the importance of the region, interest in the middle corona has increased. Although the region cannot be intrinsically separated from other regions of the solar atmosphere, there has emerged a need to define the region in terms of its location and extension in the solar atmosphere, its composition, the physical transitions it covers, and the underlying physics believed to be encapsulated by the region. This paper aims to define the middle corona and give an overview of the processes that occur there. Title: A highly dynamic small-scale jet in a polar coronal hole Authors: Mandal, Sudip; Chitta, Lakshmi Pradeep; Peter, Hardi; Solanki, Sami K.; Cuadrado, Regina Aznar; Teriaca, Luca; Schühle, Udo; Berghmans, David; Auchère, Frédéric Bibcode: 2022A&A...664A..28M Altcode: 2022arXiv220602236M We present an observational study of the plasma dynamics at the base of a solar coronal jet, using high resolution extreme ultraviolet imaging data taken by the Extreme Ultraviolet Imager on board Solar Orbiter, and by the Atmospheric Imaging Assembly on board Solar Dynamics Observatory. We observed multiple plasma ejection events over a period of ∼1 h from a dome-like base that is ca. 4 Mm wide and is embedded in a polar coronal hole. Within the dome below the jet spire, multiple plasma blobs with sizes around 1−2 Mm propagate upwards to the dome apex with speeds of the order of the sound speed (ca. 120 km s−1). Upon reaching the apex, some of these blobs initiate flows with similar speeds towards the other footpoint of the dome. At the same time, high speed super-sonic outflows (∼230 km s−1) are detected along the jet spire. These outflows as well as the intensity near the dome apex appear to be repetitive. Furthermore, during its evolution, the jet undergoes many complex morphological changes, including transitions between the standard and blowout type eruption. These new observational results highlight the underlying complexity of the reconnection process that powers these jets and they also provide insights into the plasma response when subjected to rapid energy injection.

Movies associated to Figs. 1, 2, and 4 are available at https://www.aanda.org Title: The Solaris Solar Polar MIDEX-Class Mission Concept: Revealing the Mysteries of the Sun's Poles Authors: Hassler, Donald M.; Harra, Louise K.; Gibson, Sarah; Thompson, Barbara; Gusain, Sanjay; Berghmans, David; Linker, Jon; Basu, Sarbani; Featherstone, Nicholas; Hoeksema, J. Todd; Viall, Nicholeen; Newmark, Jeffrey; Munoz-Jaramillo, Andres; Upton, Lisa A. Bibcode: 2022cosp...44.1528H Altcode: Solaris is an exciting, innovative & bold mission of discovery to reveal the mysteries of the Sun's poles. Solaris was selected for Phase A development as part of NASA's MIDEX program. Solaris builds upon the legacy of Ulysses, which flew over the solar poles, but Solaris provides an entirely new feature remote sensing, or IMAGING. Solaris will be the first mission to image the poles of the Sun from ~75 degrees latitude and provide new insight into the workings of the solar dynamo and the solar cycle, which are at the foundation of our understanding of space weather and space climate. Solaris will also provide enabling observations for improved space weather research, modeling and prediction with time series of polar magnetograms and views of the ecliptic from above, providing a unique view of the corona, coronal dynamics, and CME eruption. To reach the Sun's poles, Solaris will first travel to Jupiter, and use Jupiter's gravity to slingshot out of the ecliptic plane, and fly over the Sun's poles at ~75 degrees latitude. Just as our understanding of Jupiter & Saturn were revolutionized by polar observations from Juno and Cassini, our understanding of the Sun will be revolutionized by Solaris. Title: A spectral solar irradiance monitor (SoSpIM) on the JAXA Solar-C (EUVST) space mission Authors: Harra, Louise K.; Watanabe, Kyoko; Haberreiter, Margit; Hori, Tomoaki; Hara, Hirohisa; Kretzschmar, Matthieu; Woods, Thomas; Shimizu, Toshifumi; Krucker, Samuel; Berghmans, David; Jin, Hidekatsu; Dominique, Marie; Eparvier, Francis G.; Gissot, Samuel; Leng Yeo, Kok; Pfiffner, Dany; Milligan, Ryan; Thiemann, Edward; Miyoshi, Yoshizumi; Imada, Shinsuke; Kawate, Tomoko; Chamberlin, Phillip; Rozanov, Eugene; Silvio Koller, -.; Barczynski, Krzysztof; Nozomu; Nishitani; Ieda, Akimasa; Langer, Patrick; Meier, Leandro; Tye, Daniel; Alberti, Andrea Bibcode: 2022cosp...44..834H Altcode: The JAXA Solar-C (EUVST) mission (Shimizu et al., 2020) is designed to comprehensively understand how mass and energy are transferred throughout the solar atmosphere. The EUV High-Throughput Spectroscopic Telescope (EUVST) onboard does this by observing all the temperature regimes of the atmosphere from the chromosphere to the corona simultaneously. To enhance the EUVST scientific capabilities, there will be a Solar Spectral Irradiance Monitor (SoSpIM). SoSpIM will work hand-in-hand scientifically with EUVST, by providing the full Sun irradiance at sub-second time cadence combined with the spatially resolved spectroscopy from EUVST. The SoSPIM instrument will specifically address two aspects. These are: · Understand how the solar atmosphere becomes unstable, releasing the energy that drives solar flares - achieved through probing fast time cadence solar flare variations. · Measuring solar irradiance that impacts the Earth's thermosphere and the mesosphere, linking to spatially resolved measurements of the solar atmosphere with EUVST. SoSpIM will provide high time resolution measurements in 2 channels (a) in the corona through channel 1 (EUV) and (b) in the lower atmosphere through channel 2 (Lyman alpha). Each channel impacts different layers of the Earth's atmosphere. Title: Small-scale coronal brightenings as seen by Solar Orbiter Authors: Peter, Hardi; Berghmans, David; Chitta, Lakshmi Pradeep Bibcode: 2022cosp...44.1323P Altcode: The corona of the Sun shows variability over a wide range of scales, in space, time and energy. The power-law-like distributions small-scale coronal brightenings events have been used to propose self-similarity of the involved processes. Already during the cruise phase, Solar Orbiter was close enough to the Sun so that images provided by the Extreme Ultraviolet Imager (EUI) are among the highest resolution coronal data acquired so far. The small brightenings found in the quiet Sun, now often termed campfires, could be considered as the small end of the distribution of coronal transients. Mostly, these coronal brightenings occur very low in the atmosphere, essentially just above the chromosphere. Still they show a variety of morphology, ranging from dot-like to loop-like with propagating disturbances, small jets, or miniature flux-rope eruptions. This variety of the phenomenology on the smallest resolvable scales points towards a conclusion that there is not one single process that can drive small-scale brightenings. This is supported by studies relating the EUV brightenings to the underlying magnetic field: a part of the cases shows a relation to changes of the surface magnetic flux, while in other cases it is very hard to find any connection to the magnetic field. In the quiet Sun these small brightenings are mostly found at the edges of bright elements of the chromospheric network, which they have in common with another class of brightenings seen at lower temperatures in the transition region, namely explosive events. These transients have been proposed as being due to reconnection, have a similar size and lifetime as the small brightenings, but mostly seem to lack a component at high temperatures. It might well be that these explosive events are related to one particular type of the campfires, e.g. the jet-types, but that remains to be studied. Modelling work on small brightenings is not yet very abundant. One 3D MHD model of the quiet Sun shows coronal brightenings that share properties with the observations. Here the brightening is caused (mostly) by component reconnection, but also one case of a twisted flux rope is found in the simulation data, other (future) models most likely will reveal that also different processes could produce similar brightenings. Because of timing and the mission profile, so far remote sensing observations have been taken mostly in regions of quiet Sun. With the perihelion in March 2022 Solar Orbiter will not only be closer than 0.3 AU from the Sun, providing coronal observations at even higher resolution than before, but also active region observations are planned. These might extend the zoo of the small-scale coronal transients to small features in active regions that might show properties similar or different from the quiet Sun coronal brightenings. Either way, this will provide a challenge for our understanding of the small-scale corona. Title: The Magnetic Origin of Solar Campfires: Observations by Solar Orbiter and SDO Authors: Panesar, Navdeep Kaur; Zhukov, Andrei; Berghmans, David; Auchere, Frederic; Müller, Daniel; Tiwari, Sanjiv Kumar; Cheung, Mark Bibcode: 2022cosp...44.2564P Altcode: Solar campfires are small-scale, short-lived coronal brightenings, recently observed in 174 Å images by Extreme Ultraviolet Imager (EUI) on board Solar Orbiter (SolO). Here we investigate the magnetic origin of 52 campfires, in quiet-Sun, using line-of-sight magnetograms from Solar Dynamics Observatory (SDO)/Helioseismic and Magnetic Imager (HMI) together with extreme ultraviolet images from SolO /EUI and SDO/Atmospheric Imaging Assembly (AIA). We find that the campfires are rooted at the edges of photospheric magnetic network lanes; (ii) most of the campfires reside above neutral lines and 77% of them appear at sites of magnetic flux cancelation between the majority-polarity magnetic flux patch and a merging minority-polarity flux patch, with a flux cancelation rate of ∼1018 Mx hr‑1; some of the smallest campfires come from the sites where magnetic flux elements were barely discernible in HMI; (iii) some of the campfires occur repeatedly from the same neutral line; (iv) in the large majority of instances (79%), campfires are preceded by a cool-plasma structure, analogous to minifilaments in coronal jets; and (v) although many campfires have "complex" structure, most campfires resemble small-scale jets, dots, or loops. Thus, "campfire" is a general term that includes different types of small-scale solar dynamic features. They contain sufficient magnetic energy (∼1026-1027 erg) to heat the solar atmosphere locally to 0.5-2.5 MK. Their lifetimes range from about 1 minute to over 1 hour, with most of the campfires having a lifetime of <10 minutes. The average lengths and widths of the campfires are 5400 ± 2500 km and 1600 ± 640 km, respectively. Our observations suggest that (a) the presence of magnetic flux ropes may be ubiquitous in the solar atmosphere and not limited to coronal jets and larger-scale eruptions that make CMEs, and (b) magnetic flux cancelation, most likely driven by magnetic reconnection in the lower atmosphere, is the fundamental process for the formation and triggering of most campfires. Title: Transient small-scale brightenings in the quiet solar corona: a model for campfires observed with Solar Orbiter Authors: Chen, Yajie; Peter, Hardi; Berghmans, David; Tian, Hui; Auchère, Frédéric; Przybylski, Damien Bibcode: 2022cosp...44.2557C Altcode: Recent observations by the Extreme Ultraviolet Imager (EUI) on board Solar Orbiter have revealed prevalent small-scale transient brightenings in the quiet solar corona termed "campfires". To understand the generation mechanism of these coronal brightenings, we constructed a self-consistent and time-dependent quiet-Sun model extending from the upper convection zone to the lower corona using a realistic three-dimensional radiation magnetohydrodynamic simulation. From the model we have synthesized the coronal emission in the EUI 174 passband. We identified several transient coronal brightenings similar to those in EUI observations. The size and lifetime of these coronal brightenings are mostly 0.5-4 Mm and ~2 min, respectively. These brightenings are generally located at a height of 2-4 Mm above the photosphere, and the local plasma is often heated above 1 MK. By examining the magnetic field structures before and after the occurrence of brightenings, we concluded that these coronal brightenings are generated by component magnetic reconnection between interacting bundles of magnetic field lines or neighboring field lines within highly twisted flux ropes. Occurring in the coronal part of the atmosphere, these events generally reveal no obvious signature of flux emergence or cancellation in photospheric magnetograms. These transient coronal brightenings may play an important role in heating of the local coronal plasma. Title: Fine-scale, Dot-like, Brightenings in an Emerging Flux Region: SolO/EUI Observations, and Bifrost MHD Simulations Authors: Tiwari, Sanjiv Kumar; Berghmans, David; De Pontieu, Bart; Hansteen, Viggo; Panesar, Navdeep Kaur Bibcode: 2022cosp...44.2529T Altcode: Numerous tiny bright dots are observed in SolO's EUI/\hri\ data of an emerging flux region (a coronal bright point) in 174 \AA, emitted by the coronal plasma at $\sim$1 MK. These dots are roundish, with a diameter of 675$\pm$300 km, a lifetime of 50$\pm$35 seconds, and an intensity enhancement of 30% $\pm$10% from their immediate surroundings. About half of the dots remain isolated during their evolution and move randomly and slowly ($<$10 \kms). The other half show extensions, appearing as a small loop or surge/jet, with intensity propagations below 30\,\kms. Some dots form at the end of a fine-scale explosion. Many of the bigger and brighter EUI/HRI dots are discernible in SDO/AIA 171 \AA\ channel, have significant EM in the temperature range of 1--2 MK, and are often located at polarity inversion lines observed in HMI LOS magnetograms. Bifrost MHD simulations of an emerging flux region do show dots in synthetic Fe IX/X images, although dots in simulations are not as pervasive as in observations. The dots in simulations show distinct Doppler signatures -- blueshifts and redshifts coexist, or a redshift of the order of 10 \kms\ is followed by a blueshift of similar or higher magnitude. The synthetic images of O V/VI and Si IV lines, which form in the transition region, also show the dots that are observed in Fe IX/X images, often expanded in size, or extended as a loop, and always with stronger Doppler velocities (up to 100 \kms) than that in Fe IX/X lines. Our results, together with the field geometry of dots in the simulations, suggest that most dots in emerging flux regions form in the lower solar atmosphere (at $\approx$1 Mm) by magnetic reconnection between emerging and pre-existing/emerged magnetic field. The dots are smaller in Fe IX/X images (than in O V/VI & Si IV lines) most likely because only the hottest counterpart of the magnetic reconnection events is visible in the hotter emission. Some dots might be manifestations of magneto-acoustic shocks (from the lower atmosphere) through the line formation region of Fe IX/X. A small number of dots could also be a response of supersonic downflows impacting transition-region/chromospheric density. Title: Following prominences eruption from Sun to Parker Solar Probe with multi-spacecraft observations Authors: Niembro, Tatiana; Reeves, Kathy; Berghmans, David; Seaton, Daniel; Andretta, Vincenzo; Hess, Phillip Bibcode: 2022cosp...44.1464N Altcode: In the early hours of 2021 April 25, Solar Probe Cup on-board Parker Solar Probe (PSP) registered the passage of a solar wind structure characterized by a clear and constant alpha to proton density ratio above 6% during three hours that remained present but faint and intermittently within a twelve-hour window. PSP was behind the Sun relative to the Earth, but the spacecraft location was visible to both Solar Orbiter (SO) and STEREO-A (STA). SO and PSP were in nearly perfect quadrature. In this work, we report the helium-enriched plasma structure from the Sun to PSP combining multi-spacecraft remote sensing and in situ measurements. We identify a prominence as the likely source, visible in both STA/EUVI and SO/EUI. The associated CME was observed in STA/COR2, and SO/Metis and SoloHI and reached PSP when it was located at 46 solar radii, 8 hours after the spacecraft registered a crossing of the heliospheric current sheet. Except for the extraordinary alpha ratio enhancement, the CME showed ordinary plasma signatures and a complex magnetic field with an overall enhancement. The PSP/WISPR images show a structure entering the field of view a few hours before the in situ crossing followed by repetitive transient structures that are the result of flying through the CME body. We believe this to be the first example of a CME being imaged by PSP/WISPR directly before and during being detected in situ. Title: How Can Solar-C/SOSPIM Contribute to the Understanding of Quasi-Periodic Pulsations in Solar Flares? Authors: Dominique, Marie; Harra, Louise K.; Watanabe, Kyoko; Hara, Hirohisa; Zhukov, Andrei; Shimizu, Toshifumi; Berghmans, David; Dolla, Laurent; Gissot, Samuel; Pfiffner, Dany; Imada, Shinsuke; Silvio Koller, -.; Meier, Leandro; Tye, Daniel; Alberti, Andrea Bibcode: 2022cosp...44.2524D Altcode: Quasi-periodic pulsations (QPPs) refer to nearly-periodic oscillations that are often observed in irradiance time series during solar flares and have also been reported in several stellar flares. In the last years, several statistical studies based on Soft X-ray measurements have reached the conclusion that QPPs are present in most solar flares of class M and above. Still, as of today, we are still unsure of what causes QPPs. Several models could explain the presence of QPPs with periods matching the ones observed. More detailed analysis of the observational signatures of QPPs might help determine which of those models are actually playing a role in the generation of QPPs. However, as QPPs is a small timescale process (the period of QPPs is often reported to be less than a minute), such an analysis requires instruments with a good signal-to-noise and high sampling rate. In this context, the spectral solar irradiance monitor SOSPIM, that will be part of the JAXA SOLAR C mission and that will complement the EUVST spectrograph measurements, could be a valuable asset. SOSPIM will observe the solar chromosphere and corona in the Lyman-alpha and EUV spectral ranges at high cadence. In this presentation, we review the current knowledge of QPPs and describe what could be the contribution of SOSPIM to push their understanding one step forward. Title: Coronal Microjets in Quiet-sun Regions Observed with the Extreme Ultraviolet Imager Onboard Solar Orbiter Authors: Hou, Zhenyong; He, Jiansen; Berghmans, David; Teriaca, Luca; Wang, Linghua; Schuehle, Udo; Tian, Hui; Chen, Yajie; Chen, Hechao; Gao, Yuhang; Bai, Xianyong Bibcode: 2022cosp...44.2536H Altcode: We report the smallest coronal jets ever observed in the quiet Sun with recent high resolution observations from the High Resolution Telescopes (HRI-EUV and HRI-Lyα) of the Extreme Ultraviolet Imager (EUI) onboard Solar Orbiter. In the HRI-EUV (174 Å) images, these microjets usually appear as nearly collimated structures with brightenings at their footpoints. Their average lifetime, projected speed, width, and maximum length are 4.6 min, 62 km $s^{-1}$, 1.0 Mm, and 7.7 Mm, respectively. Inverted-Y shaped structures and moving blobs can be identified in some events. A subset of these events also reveal signatures in the HRI-Lyα (H I Lyα at 1216 Å) images and the extreme ultraviolet images taken by the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory. Our differential emission measure analysis suggests a multi-thermal nature and an average density of ~1.4x10^9 $cm^{-3}$ for these microjets. Their thermal and kinetic energies were estimated to be ~3.9x10$^{24}$ erg and ~2.9x10$^{23}$ erg, respectively, which are of the same order of the released energy predicted by the nanoflare theory. Most events appear to be located at the edges of network lanes and magnetic flux concentrations, suggesting that these coronal microjets are likely generated by magnetic reconnection between small-scale magnetic loops and the adjacent network field. Title: High frequency oscillations in Solar Orbiter/EUI observations Authors: Petrova, Elena; Berghmans, David; van Doorsselaere, Tom; Magyar, Norbert Bibcode: 2022cosp...44.1348P Altcode: The power required to heat the corona is well established and constitutes 100-200 $W\cdot m^{-2}$ for the Quiet sun regions and approximately $10^4 \: W \cdot m^{-2}$ for the active regions. However, the waves that are resolved using existing instruments do not appear to show enough power to satisfy the condition, though the estimated values are subjected to uncertainty. On the other hand, the frequency range of the observed waves via imaging instruments is limited due to instrumental constraints, making it impossible to observe waves with a higher frequency that can potentially contain a substantial amount of the energy flux. The unprecedented high cadence of the EUI HRI imager onboard the Solar Orbiter allows accessing high cadence and high temporal resolution images of the solar corona. The current talk addresses the transverse oscillations detected in data from the HRIEUV on Feb 23 with a cadence of 2 seconds. It was located at the distance of 0.52 AU, resulting in a spatial resolution of 1 pixel corresponding to 200 km on the Sun. 1 event was analyzed, and transverse oscillations were detected in the two loops with lengths of 11.7 Mm 4.5 Mm. The observed wave phenomenon is interpreted as decayless kink oscillations. The periods of the analyzed oscillations are 30 and 14 s, corresponding to longer and shorter loops, respectively, which lie outside of the range of periods for the previously detected kink oscillations. The waves demonstrate high energy flux values, with 6.5 and 2 $kW \cdot m^{-2}$, which exceeds the radiative losses from these coronal loops. Performed numerical modeling supports the energy estimations derived from the observations. The matter of omnipresence of these oscillations is to be investigated with future HRIEUV observations. However, if the omnipresence is confirmed, detected short-period oscillations could become a potential candidate to play a role in coronal heating. 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: Prominence eruption observed in He II 304 Å up to >6 R⊙ by EUI/FSI aboard Solar Orbiter Authors: Mierla, M.; Zhukov, A. N.; Berghmans, D.; Parenti, S.; Auchère, F.; Heinzel, P.; Seaton, D. B.; Palmerio, E.; Jejčič, S.; Janssens, J.; Kraaikamp, E.; Nicula, B.; Long, D. M.; Hayes, L. A.; Jebaraj, I. C.; Talpeanu, D. -C.; D'Huys, E.; Dolla, L.; Gissot, S.; Magdalenić, J.; Rodriguez, L.; Shestov, S.; Stegen, K.; Verbeeck, C.; Sasso, C.; Romoli, M.; Andretta, V. Bibcode: 2022A&A...662L...5M Altcode: 2022arXiv220515214M
Aims: We report observations of a unique, large prominence eruption that was observed in the He II 304 Å passband of the Extreme Ultraviolet Imager/Full Sun Imager telescope aboard Solar Orbiter on 15-16 February 2022.
Methods: Observations from several vantage points - Solar Orbiter, the Solar-Terrestrial Relations Observatory, the Solar and Heliospheric Observatory, and Earth-orbiting satellites - were used to measure the kinematics of the erupting prominence and the associated coronal mass ejection. Three-dimensional reconstruction was used to calculate the deprojected positions and speeds of different parts of the prominence. Observations in several passbands allowed us to analyse the radiative properties of the erupting prominence.
Results: The leading parts of the erupting prominence and the leading edge of the corresponding coronal mass ejection propagate at speeds of around 1700 km s−1 and 2200 km s−1, respectively, while the trailing parts of the prominence are significantly slower (around 500 km s−1). Parts of the prominence are tracked up to heights of over 6 R⊙. The He II emission is probably produced via collisional excitation rather than scattering. Surprisingly, the brightness of a trailing feature increases with height.
Conclusions: The reported prominence is the first observed in He II 304 Å emission at such a great height (above 6 R⊙).

Movies are available at https://www.aanda.org Title: Observation of Magnetic Switchback in the Solar Corona Authors: Telloni, Daniele; Zank, Gary P.; Stangalini, Marco; Downs, Cooper; Liang, Haoming; Nakanotani, Masaru; Andretta, Vincenzo; Antonucci, Ester; Sorriso-Valvo, Luca; Adhikari, Laxman; Zhao, Lingling; Marino, Raffaele; Susino, Roberto; Grimani, Catia; Fabi, Michele; D'Amicis, Raffaella; Perrone, Denise; Bruno, Roberto; Carbone, Francesco; Mancuso, Salvatore; Romoli, Marco; Da Deppo, Vania; Fineschi, Silvano; Heinzel, Petr; Moses, John D.; Naletto, Giampiero; Nicolini, Gianalfredo; Spadaro, Daniele; Teriaca, Luca; Frassati, Federica; Jerse, Giovanna; Landini, Federico; Pancrazzi, Maurizio; Russano, Giuliana; Sasso, Clementina; Berghmans, David; Auchère, Frédéric; Aznar Cuadrado, Regina; Chitta, Lakshmi P.; Harra, Louise; Kraaikamp, Emil; Long, David M.; Mandal, Sudip; Parenti, Susanna; Pelouze, Gabriel; Peter, Hardi; Rodriguez, Luciano; Schühle, Udo; Schwanitz, Conrad; Smith, Phil J.; Verbeeck, Cis; Zhukov, Andrei N. Bibcode: 2022arXiv220603090T Altcode: Switchbacks are sudden, large radial deflections of the solar wind magnetic field, widely revealed in interplanetary space by the Parker Solar Probe. The switchbacks' formation mechanism and sources are still unresolved, although candidate mechanisms include Alfvénic turbulence, shear-driven Kelvin-Helmholtz instabilities, interchange reconnection, and geometrical effects related to the Parker spiral. This Letter presents observations from the Metis coronagraph onboard Solar Orbiter of a single large propagating S-shaped vortex, interpreted as first evidence of a switchback in the solar corona. It originated above an active region with the related loop system bounded by open-field regions to the East and West. Observations, modeling, and theory provide strong arguments in favor of the interchange reconnection origin of switchbacks. Metis measurements suggest that the initiation of the switchback may also be an indicator of the origin of slow solar wind. Title: High frequency decayless waves with significant energy in Solar Orbiter/EUI observations Authors: Petrova, Elena; Magyar, Norbert; Van Doorsselaere, Tom; Berghmans, David Bibcode: 2022arXiv220505319P Altcode: High-frequency wave phenomena present a great deal of interest as one of the possible candidates to contribute to the energy input required to heat the corona as a part of the AC heating theory. However, the resolution of imaging instruments up until the Solar Orbiter have made it impossible to resolve the necessary time and spatial scales. The present paper reports on high-frequency transverse motions in a small loop located in a quiet Sun region of the corona. The oscillations were observed with the HRIEUV telescope (17.4 nm) of the EUI instrument onboard the Solar Orbiter. We detect two transverse oscillations in short loops with lengths of 4.5 Mm and 11 Mm. The shorter loop displays an oscillation with a 14 s period and the longer a 30 s period. Despite the high resolution, no definitive identification as propagating or standing waves is possible. The velocity amplitudes are found to be equal to 72 km/s and 125 km/s, respectively, for the shorter and longer loop. Based on that, we also estimated the values of the energy flux contained in the loops - the energy flux of the 14 s oscillation is 1.9 kW m^-2 and of the 30 s oscillation it is 6.5 kW m^-2 . While these oscillations have been observed in the Quiet Sun, their energy fluxes are of the same order as the energy input required to heat the active solar corona. Numerical simulations were performed in order to reproduce the observed oscillations. The correspondence of the numerical results to the observations provide support to the energy content estimates for the observations. Such high energy densities have not yet been observed in decayless coronal waves, and this is promising for coronal heating models based on wave damping. Title: SolO/EUI Observations of Ubiquitous Fine-scale Bright Dots in an Emerging Flux Region: Comparison with a Bifrost MHD Simulation Authors: Tiwari, Sanjiv K.; Hansteen, Viggo H.; De Pontieu, Bart; Panesar, Navdeep K.; Berghmans, David Bibcode: 2022ApJ...929..103T Altcode: 2022arXiv220306161T We report on the presence of numerous tiny bright dots in and around an emerging flux region (an X-ray/coronal bright point) observed with SolO's EUI/HRIEUV in 174 Å. These dots are roundish and have a diameter of 675 ± 300 km, a lifetime of 50 ± 35 s, and an intensity enhancement of 30% ± 10% above their immediate surroundings. About half of the dots remain isolated during their evolution and move randomly and slowly (<10 km s-1). The other half show extensions, appearing as a small loop or surge/jet, with intensity propagations below 30 km s-1. Many of the bigger and brighter HRIEUV dots are discernible in the SDO/AIA 171 Å channel, have significant emissivity in the temperature range of 1-2 MK, and are often located at polarity inversion lines observed in SDO/HMI LOS magnetograms. Although not as pervasive as in observations, a Bifrost MHD simulation of an emerging flux region does show dots in synthetic Fe IX/X images. These dots in the simulation show distinct Doppler signatures-blueshifts and redshifts coexist, or a redshift of the order of 10 km s-1 is followed by a blueshift of similar or higher magnitude. The synthetic images of O V/VI and Si IV lines, which represent transition region radiation, also show the dots that are observed in Fe IX/X images, often expanded in size, or extended as a loop, and always with stronger Doppler velocities (up to 100 km s-1) than that in Fe IX/X lines. Our observation and simulation results, together with the field geometry of dots in the simulation, suggest that most dots in emerging flux regions form in the lower solar atmosphere (at ≍ 1 Mm) by magnetic reconnection between emerging and preexisting/emerged magnetic field. Some dots might be manifestations of magnetoacoustic shocks through the line formation region of Fe IX/X emission. Title: The magnetic drivers of campfires seen by the Polarimetric and Helioseismic Imager (PHI) on Solar Orbiter Authors: Kahil, F.; Hirzberger, J.; Solanki, S. K.; Chitta, L. P.; Peter, H.; Auchère, F.; Sinjan, J.; Orozco Suárez, D.; Albert, K.; Albelo Jorge, N.; Appourchaux, T.; Alvarez-Herrero, A.; Blanco Rodríguez, J.; Gandorfer, A.; Germerott, D.; Guerrero, L.; Gutiérrez Márquez, P.; Kolleck, M.; del Toro Iniesta, J. C.; Volkmer, R.; Woch, J.; Fiethe, B.; Gómez Cama, J. M.; Pérez-Grande, I.; Sanchis Kilders, E.; Balaguer Jiménez, M.; Bellot Rubio, L. R.; Calchetti, D.; Carmona, M.; Deutsch, W.; Fernández-Rico, G.; Fernández-Medina, A.; García Parejo, P.; Gasent-Blesa, J. L.; Gizon, L.; Grauf, B.; Heerlein, K.; Lagg, A.; Lange, T.; López Jiménez, A.; Maue, T.; Meller, R.; Michalik, H.; Moreno Vacas, A.; Müller, R.; Nakai, E.; Schmidt, W.; Schou, J.; Schühle, U.; Staub, J.; Strecker, H.; Torralbo, I.; Valori, G.; Aznar Cuadrado, R.; Teriaca, L.; Berghmans, D.; Verbeeck, C.; Kraaikamp, E.; Gissot, S. Bibcode: 2022A&A...660A.143K Altcode: 2022arXiv220213859K Context. The Extreme Ultraviolet Imager (EUI) on board the Solar Orbiter (SO) spacecraft observed small extreme ultraviolet (EUV) bursts, termed campfires, that have been proposed to be brightenings near the apexes of low-lying loops in the quiet-Sun atmosphere. The underlying magnetic processes driving these campfires are not understood.
Aims: During the cruise phase of SO and at a distance of 0.523 AU from the Sun, the Polarimetric and Helioseismic Imager on Solar Orbiter (SO/PHI) observed a quiet-Sun region jointly with SO/EUI, offering the possibility to investigate the surface magnetic field dynamics underlying campfires at a spatial resolution of about 380 km.
Methods: We used co-spatial and co-temporal data of the quiet-Sun network at disc centre acquired with the High Resolution Imager of SO/EUI at 17.4 nm (HRIEUV, cadence 2 s) and the High Resolution Telescope of SO/PHI at 617.3 nm (HRT, cadence 2.5 min). Campfires that are within the SO/PHI−SO/EUI common field of view were isolated and categorised according to the underlying magnetic activity.
Results: In 71% of the 38 isolated events, campfires are confined between bipolar magnetic features, which seem to exhibit signatures of magnetic flux cancellation. The flux cancellation occurs either between the two main footpoints, or between one of the footpoints of the loop housing the campfire and a nearby opposite polarity patch. In one particularly clear-cut case, we detected the emergence of a small-scale magnetic loop in the internetwork followed soon afterwards by a campfire brightening adjacent to the location of the linear polarisation signal in the photosphere, that is to say near where the apex of the emerging loop lays. The rest of the events were observed over small scattered magnetic features, which could not be identified as magnetic footpoints of the campfire hosting loops.
Conclusions: The majority of campfires could be driven by magnetic reconnection triggered at the footpoints, similar to the physical processes occurring in the burst-like EUV events discussed in the literature. About a quarter of all analysed campfires, however, are not associated to such magnetic activity in the photosphere, which implies that other heating mechanisms are energising these small-scale EUV brightenings. Title: Comparing the Heliospheric Cataloging, Analysis, and Techniques Service (HELCATS) Manual and Automatic Catalogues of Coronal Mass Ejections Using Solar Terrestrial Relations Observatory/Heliospheric Imager (STEREO/HI) Data Authors: Rodriguez, L.; Barnes, D.; Hosteaux, S.; Davies, J. A.; Willems, S.; Pant, V.; Harrison, R. A.; Berghmans, D.; Bothmer, V.; Eastwood, J. P.; Gallagher, P. T.; Kilpua, E. K. J.; Magdalenic, J.; Mierla, M.; Möstl, C.; Rouillard, A. P.; Odstrčil, D.; Poedts, S. Bibcode: 2022SoPh..297...23R Altcode: We present the results of a comparative study between automatic and manually compiled coronal mass ejection (CME) catalogues based on observations from the Heliospheric Imagers (HIs) onboard NASA's Solar Terrestrial Relations Observatory (STEREO) spacecraft. Using the Computer Aided CME Tracking software(CACTus), CMEs are identified in HI data using an automatic feature-detection algorithm, while the Heliospheric Imagers Catalogue(HICAT) includes CMEs that are detected by visual inspection of HI images. Both catalogues were compiled as part of the EU FP7 Heliospheric Cataloguing, Analysis and Techniques Service (HELCATS) project (www.helcats-fp7.eu). We compare observational parameters of the CMEs from CACTus to those listed in HICAT, such as CME frequency, position angle (PA), and PA-width. We also compare CACTus-derived speeds to speeds derived from applying geometric modelling to the majority of the HICAT CMEs, the results of which are listed in the HELCATS Heliospheric Imagers Geometric Catalogue(HIGeoCAT). We find that both CACTus and HICAT catalogues contain a similar number of events when we exclude events narrower than 20∘, which are not included in the HICAT catalogue but are found to be identified by CACTus. PA-distributions are strongly peaked around 90∘ and 270∘, with a slightly larger CME frequency northwards of the equatorial plane (particularly for the STEREO-A versions of both catalogues). The CME PA-widths in both HICAT and CACTus catalogues peak at approximately 60∘. Manually derived speeds from HIGeoCAT and automatically derived speeds by CACTus correlate well for values lower than 1000 km s−1, in particular when CMEs are propagating close to the plane of the sky. 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: How Can Solar-C/SOSPIM Contribute to the Understanding of Quasi-Periodic Pulsations in Solar Flares? Authors: Dominique, Marie; Dolla, Laurent; Zhukov, Andrei; Alberti, Andrea; Berghmans, David; Gissot, Samuel; Hara, Hirohisa; Harra, Louise; Imada, Shinsuke; Koller, Silvio; Meier, Leandro; Pfiffner, Daniel; Shimizu, Toshifumi; Tye, Daniel; Watanabe, Kyoko Bibcode: 2021AGUFMSH25E2124D Altcode: Quasi-periodic pulsations (QPPs) refer to nearly-periodic oscillations that are often observed in irradiance time series during solar flares and have also been reported in several stellar flares. In the last years, several statistical studies based on Soft X-ray measurements have reached the conclusion that QPPs are present in most solar flares of class M and above. Still, the mechanism at the origin of QPPs is under debate. Are they caused by waves or periodic fluctuations of the magnetic reconnection driving the flare? Analyzing the characteristics of QPPs and their evolution during the flare could help identifying their origin. However, QPPs sometimes exhibit very different periodicities, and do not always happen during the same phase of the flare. All this could point to the coexistence of QPPs with different origin mechanism, and indicates the need for more observations. In this context, the spectral solar irradiance monitor SOSPIM, that will be part of the JAXA SOLAR C mission and that will complement the EUVST spectrograph measurements, could be a valuable asset. SOSPIM will observe the solar chromosphere and corona in the Lyman-alpha and EUV spectral ranges at high cadence. In this presentation, we review the current knowledge of QPPs and describe what could be the contribution of SOSPIM to push their understanding one step forward. 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: Campfires observed by EUI: What have we learned so far? Authors: Berghmans, David; Auchere, F.; Zhukov, Andrei; Mierla, Marilena; Chen, Yajie; Peter, Hardi; Panesar, Navdeep; Chitta, Lakshmi Pradeep; Antolin, Patrick; Aznar Cuadrado, Regina; Tian, Hui; Hou, Zhenyong; Podladchikova, Olena Bibcode: 2021AGUFMSH21A..02B Altcode: Since its very first light images of the corona, the EUI/HRIEUV telescope onboard Solar Orbiter has observed small localised brightenings in the Quiet Sun. These small localised brightenings, have become known as campfires, and are observed with length scales between 400 km and 4000 km and durations between 10 sec and 200 sec. The smallest and weakest of these HRIEUV brightenings have not been previously observed. Simultaneous observations from the EUI High-resolution Lyman- 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. Some of the larger campfires have the appearance of small interacting loops with the brightening expanding from the contact point of the loops. Our differential emission measure (DEM) analysis indicated coronal temperatures. We determined the height for a few of these campfires to be between 1 and 5 Mm above the photosphere. 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. 3D MHD simulations with the MURaM code revealed brightenings that are in many ways similar to the campfires by EUI. The brightenings in the simulations suggest that campfires are triggered by component reconnection inside flux bundles rather than flux emergence or cancellation. Nevertheless, some of the observed campfires can be clearly linked to flux cancellation events and, intriguingly, are preceded by an erupting cool plasma structure. Analysis of the dynamics of campfires revealed that some have the appearance of coronal microjets, the smallest coronal jets observed in the quiet Sun. The HRIEUV images also reveal transient jets on a somewhat bigger scale with repeated outflows on the order of 100 km s1. In this paper we will provide an overview of the campfire related phenomena that EUI has observed and discuss the possible relevance for coronal heating. 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: Capturing transient plasma flows and jets in the solar corona Authors: Chitta, L. P.; Solanki, S. K.; Peter, H.; Aznar Cuadrado, R.; Teriaca, L.; Schühle, U.; Auchère, F.; Berghmans, D.; Kraaikamp, E.; Gissot, S.; Verbeeck, C. Bibcode: 2021A&A...656L..13C Altcode: 2021arXiv210915106C Intensity bursts in ultraviolet (UV) to X-ray wavelengths and plasma jets are typical signatures of magnetic reconnection and the associated impulsive heating of the solar atmospheric plasma. To gain new insights into the process, high-cadence observations are required to capture the rapid response of plasma to magnetic reconnection as well as the highly dynamic evolution of jets. Here, we report the first 2 s cadence extreme-UV observations recorded by the 174 Å High Resolution Imager of the Extreme Ultraviolet Imager on board the Solar Orbiter mission. These observations, covering a quiet-Sun coronal region, reveal the onset signatures of magnetic reconnection as localized heating events. These localized sources then exhibit repeated plasma eruptions or jet activity. Our observations show that this spatial morphological change from localized sources to jet activity could occur rapidly on timescales of about 20 s. The jets themselves are intermittent and are produced from the source region on timescales of about 20 s. In the initial phases of these events, plasma jets are observed to exhibit speeds, as inferred from propagating intensity disturbances, in the range of 100 km s−1 to 150 km s−1. These jets then propagate to lengths of about 5 Mm. We discuss examples of bidirectional and unidirectional jet activity observed to have been initiated from the initially localized bursts in the corona. The transient nature of coronal bursts and the associated plasma flows or jets along with their dynamics could provide a benchmark for magnetic reconnection models of coronal bursts and jets.

Movies are available at https://www.aanda.org Title: Propagating brightenings in small loop-like structures in the quiet-Sun corona: Observations from Solar Orbiter/EUI Authors: Mandal, Sudip; Peter, Hardi; Chitta, Lakshmi Pradeep; Solanki, Sami K.; Aznar Cuadrado, Regina; Teriaca, Luca; Schühle, Udo; Berghmans, David; Auchère, Frédéric Bibcode: 2021A&A...656L..16M Altcode: 2021arXiv211108106M Brightenings observed in solar extreme-ultraviolet images are generally interpreted as signatures of micro- or nanoflares occurring in the transition region or at coronal temperatures. Recent observations with the Extreme Ultraviolet Imager (EUI) on board Solar Orbiter have revealed the smallest of such brightenings (called campfires) in the quiet-Sun corona. Analyzing EUI 174 Å data obtained at a resolution of about 400 km on the Sun with a cadence of 5 s on 30 May 2020, we report here a number of cases in which these campfires exhibit propagating signatures along their apparently small (3-5 Mm) loop-like structures. The measured propagation speeds are generally between 25 km s−1 and 60 km s−1. If the loop plasma is assumed to be at a million Kelvin, these apparent motions would be slower than the local sound speed. Furthermore, these brightenings exhibit nontrivial propagation characteristics such as bifurcation, merging, reflection, and repeated plasma ejections. We suggest that these features are manifestations of the internal dynamics of these small-scale magnetic structures and could provide important insights into the dynamic response (∼40 s) of the loop plasma to the heating events and also into the locations of the heating events themselves.

Movies associated to Figs 2-5, A.1, and B.1 are available at https://www.aanda.org Title: The first coronal mass ejection observed in both visible-light and UV H I Ly-α channels of the Metis coronagraph on board Solar Orbiter Authors: Andretta, V.; Bemporad, A.; De Leo, Y.; Jerse, G.; Landini, F.; Mierla, M.; Naletto, G.; Romoli, M.; Sasso, C.; Slemer, A.; Spadaro, D.; Susino, R.; Talpeanu, D. -C.; Telloni, D.; Teriaca, L.; Uslenghi, M.; Antonucci, E.; Auchère, F.; Berghmans, D.; Berlicki, A.; Capobianco, G.; Capuano, G. E.; Casini, C.; Casti, M.; Chioetto, P.; Da Deppo, V.; Fabi, M.; Fineschi, S.; Frassati, F.; Frassetto, F.; Giordano, S.; Grimani, C.; Heinzel, P.; Liberatore, A.; Magli, E.; Massone, G.; Messerotti, M.; Moses, D.; Nicolini, G.; Pancrazzi, M.; Pelizzo, M. -G.; Romano, P.; Schühle, U.; Stangalini, M.; Straus, Th.; Volpicelli, C. A.; Zangrilli, L.; Zuppella, P.; Abbo, L.; Aznar Cuadrado, R.; Bruno, R.; Ciaravella, A.; D'Amicis, R.; Lamy, P.; Lanzafame, A.; Malvezzi, A. M.; Nicolosi, P.; Nisticò, G.; Peter, H.; Plainaki, C.; Poletto, L.; Reale, F.; Solanki, S. K.; Strachan, L.; Tondello, G.; Tsinganos, K.; Velli, M.; Ventura, R.; Vial, J. -C.; Woch, J.; Zimbardo, G. Bibcode: 2021A&A...656L..14A Altcode: Context. The Metis coronagraph on board Solar Orbiter offers a new view of coronal mass ejections (CMEs), observing them for the first time with simultaneous images acquired with a broad-band filter in the visible-light interval and with a narrow-band filter around the H I Ly-α line at 121.567 nm, the so-called Metis UV channel.
Aims: We show the first Metis observations of a CME, obtained on 16 and 17 January 2021. The event was also observed by the EUI/FSI imager on board Solar Orbiter, as well as by other space-based coronagraphs, such as STEREO-A/COR2 and SOHO/LASCO/C2, whose images are combined here with Metis data.
Methods: Different images are analysed here to reconstruct the 3D orientation of the expanding CME flux rope using the graduated cylindrical shell model. This also allows us to identify the possible location of the source region. Measurements of the CME kinematics allow us to quantify the expected Doppler dimming in the Ly-α channel.
Results: Observations show that most CME features seen in the visible-light images are also seen in the Ly-α images, although some features in the latter channel appear more structured than their visible-light counterparts. We estimated the expansion velocity of this event to be below 140 km s−1. Hence, these observations can be understood by assuming that Doppler dimming effects do not strongly reduce the Ly-α emission from the CME. These velocities are comparable with or smaller than the radial velocities inferred from the same data in a similar coronal structure on the east side of the Sun.
Conclusions: The first observations by Metis of a CME demonstrate the capability of the instrument to provide valuable and novel information on the structure and dynamics of these coronal events. Considering also its diagnostics capabilities regarding the conditions of the ambient corona, Metis promises to significantly advance our knowledge of such phenomena.

Movies are available at https://www.aanda.org Title: SWAP and the Middle Corona Authors: West, Matthew; Seaton, Daniel; D'Huys, Elke; Berghmans, David; Mierla, Marilena; Rachmeler, Laurel Bibcode: 2021AGUFMSH15D2053W Altcode: The SWAP instrument on PROBA2 has been observing the Middle Corona for over a solar cycle, it has helped shape our understanding of this previously understudied region, and enabled research into the region by providing the first uncompressed, high-cadence, large field-of-view EUV observations of the region. In this presentation we provide an overview of SWAPs imaging capabilities, techniques used to observe and enhance observations of the region, and a review of the unique observations made by SWAP. We present an overview of the phenomena that passes through and interacts with the region, and how these structures are affected by the ambient plasma properties, and in turn how the structures change the region. Both dynamic and long-lived structures are discussed. We look at the solar cycle dependence of structures observed in this region, and we present some of the open questions pertaining to the region and what needs to be done to further our understanding of the Middle Corona. Title: Evidence for local particle acceleration in the first recurrent galactic cosmic ray depression observed by Solar Orbiter. The ion event on 19 June 2020 Authors: Aran, A.; Pacheco, D.; Laurenza, M.; Wijsen, N.; Lario, D.; Benella, S.; Richardson, I. G.; Samara, E.; Freiherr von Forstner, J. L.; Sanahuja, B.; Rodriguez, L.; Balmaceda, L.; Espinosa Lara, F.; Gómez-Herrero, R.; Steinvall, K.; Vecchio, A.; Krupar, V.; Poedts, S.; Allen, R. C.; Andrews, G. B.; Angelini, V.; Berger, L.; Berghmans, D.; Boden, S.; Böttcher, S. I.; Carcaboso, F.; Cernuda, I.; De Marco, R.; Eldrum, S.; Evans, V.; Fedorov, A.; Hayes, J.; Ho, G. C.; Horbury, T. S.; Janitzek, N. P.; Khotyaintsev, Yu. V.; Kollhoff, A.; Kühl, P.; Kulkarni, S. R.; Lees, W. J.; Louarn, P.; Magdalenic, J.; Maksimovic, M.; Malandraki, O.; Martínez, A.; Mason, G. M.; Martín, C.; O'Brien, H.; Owen, C.; Parra, P.; Prieto Mateo, M.; Ravanbakhsh, A.; Rodriguez-Pacheco, J.; Rodriguez Polo, O.; Sánchez Prieto, S.; Schlemm, C. E.; Seifert, H.; Terasa, J. C.; Tyagi, K.; Verbeeck, C.; Wimmer-Schweingruber, R. F.; Xu, Z. G.; Yedla, M. K.; Zhukov, A. N. Bibcode: 2021A&A...656L..10A Altcode: Context. In mid-June 2020, the Solar Orbiter (SolO) mission reached its first perihelion at 0.51 au and started its cruise phase, with most of the in situ instruments operating continuously.
Aims: We present the in situ particle measurements of the first proton event observed after the first perihelion obtained by the Energetic Particle Detector (EPD) suite on board SolO. The potential solar and interplanetary (IP) sources of these particles are investigated.
Methods: Ion observations from ∼20 keV to ∼1 MeV are combined with available solar wind data from the Radio and Plasma Waves (RPW) instrument and magnetic field data from the magnetometer on board SolO to evaluate the energetic particle transport conditions and infer the possible acceleration mechanisms through which particles gain energy. We compare > 17-20 MeV ion count rate measurements for two solar rotations, along with the solar wind plasma data available from the Solar Wind Analyser (SWA) and RPW instruments, in order to infer the origin of the observed galactic cosmic ray (GCR) depressions.
Results: The lack of an observed electron event and of velocity dispersion at various low-energy ion channels and the observed IP structure indicate a local IP source for the low-energy particles. From the analysis of the anisotropy of particle intensities, we conclude that the low-energy ions were most likely accelerated via a local second-order Fermi process. The observed GCR decrease on 19 June, together with the 51.8-1034.0 keV nuc−1 ion enhancement, was due to a solar wind stream interaction region (SIR). The observation of a similar GCR decrease in the next solar rotation favours this interpretation and constitutes the first observation of a recurrent GCR decrease by SolO. The analysis of the recurrence times of this SIR suggests that it is the same SIR responsible for the 4He events previously measured in April and May. Finally, we point out that an IP structure more complex than a common SIR cannot be discarded, mainly due to the lack of solar wind temperature measurements and the lack of a higher cadence of solar wind velocity observations.

Movies associated to Figs. B.1 and B.2 are available at https://www.aanda.org Title: Transient small-scale brightenings in the quiet solar corona: A model for campfires observed with Solar Orbiter Authors: Chen, Yajie; Przybylski, Damien; Peter, Hardi; Tian, Hui; Auchère, F.; Berghmans, D. Bibcode: 2021A&A...656L...7C Altcode: 2021arXiv210410940C Context. Recent observations by the Extreme Ultraviolet Imager (EUI) on board Solar Orbiter have characterized prevalent small-scale transient brightenings in the corona above the quiet Sun termed campfires.
Aims: In this study we search for comparable brightenings in a numerical model and then investigate their relation to the magnetic field and the processes that drive these events.
Methods: We used the MURaM code to solve the 3D radiation magnetohydrodynamic equations in a box that stretches from the upper convection zone to the corona. The model self-consistently produces a supergranular network of the magnetic field and a hot corona above this quiet Sun. For the comparison with the model, we synthesized the coronal emission as seen by EUI in its 174 Å channel, isolated the seven strongest transient brightenings, and investigated the changes of the magnetic field in and around these in detail.
Results: The transients we isolated have a lifetime of about 2 min and are elongated loop-like features with lengths around 1 Mm to 4 Mm. They tend to occur at heights of about 2 Mm to 5 Mm above the photosphere, a bit offset from magnetic concentrations that mark the bright chromospheric network, and they reach temperatures of above 1 MK. As a result, they very much resemble the larger campfires found in observations. In our model most events are energized by component reconnection between bundles of field lines that interact at coronal heights. In one case, we find that untwisting a highly twisted flux rope initiates the heating.
Conclusions: Based on our study, we propose that the majority of campfire events found by EUI are driven by component reconnection and our model suggests that this process significantly contributes to the heating of the corona above the quiet Sun.

Movies associated to Figs. 2, 4, 5, and A1 are available at https://www.aanda.org 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: The Magnetic Origin of Solar Campfires Authors: Panesar, Navdeep K.; Tiwari, Sanjiv K.; Berghmans, David; Cheung, Mark C. M.; Müller, Daniel; Auchere, Frederic; Zhukov, Andrei Bibcode: 2021ApJ...921L..20P Altcode: 2021arXiv211006846P Solar campfires are fine-scale heating events, recently observed by Extreme Ultraviolet Imager (EUI) on board Solar Orbiter. Here we use EUI 174 Å images, together with EUV images from Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA), and line-of-sight magnetograms from SDO/Helioseismic and Magnetic Imager (HMI) to investigate the magnetic origin of 52 randomly selected campfires in the quiet solar corona. We find that (i) the campfires are rooted at the edges of photospheric magnetic network lanes; (ii) most of the campfires reside above the neutral line between majority-polarity magnetic flux patch and a merging minority-polarity flux patch, with a flux cancelation rate of ~1018 Mx hr-1; (iii) some of the campfires occur repeatedly from the same neutral line; (iv) in the large majority of instances, campfires are preceded by a cool-plasma structure, analogous to minifilaments in coronal jets; and (v) although many campfires have "complex" structure, most campfires resemble small-scale jets, dots, or loops. Thus, "campfire" is a general term that includes different types of small-scale solar dynamic features. They contain sufficient magnetic energy (~1026-1027 erg) to heat the solar atmosphere locally to 0.5-2.5 MK. Their lifetimes range from about 1 minute to over 1 hr, with most of the campfires having a lifetime of <10 minutes. The average lengths and widths of the campfires are 5400 ± 2500 km and 1600 ± 640 km, respectively. Our observations suggest that (a) the presence of magnetic flux ropes may be ubiquitous in the solar atmosphere and not limited to coronal jets and larger-scale eruptions that make CMEs, and (b) magnetic flux cancelation is the fundamental process for the formation and triggering of most campfires. Title: Coronal Microjets in Quiet-Sun Regions Observed with the Extreme Ultraviolet Imager on Board the Solar Orbiter Authors: Hou, Zhenyong; Tian, Hui; Berghmans, David; Chen, Hechao; Teriaca, Luca; Schühle, Udo; Gao, Yuhang; Chen, Yajie; He, Jiansen; Wang, Linghua; Bai, Xianyong Bibcode: 2021ApJ...918L..20H Altcode: 2021arXiv210808718H We report the smallest coronal jets ever observed in the quiet Sun with recent high-resolution observations from the High Resolution Telescopes (HRIEUV and HRILyα) of the Extreme Ultraviolet Imager on board the Solar Orbiter (SO). In the HRIEUV (174 Å) images, these microjets usually appear as nearly collimated structures with brightenings at their footpoints. Their average lifetime, projected speed, width, and maximum length are 4.6 minutes, 62 km s-1, 1.0 Mm, and 7.7 Mm, respectively. Inverted-Y shaped structures and moving blobs can be identified in some events. A subset of these events also reveal signatures in the HRILyα (H I Lyα at 1216 Å) images and the extreme ultraviolet images taken by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). Our differential emission-measure (EM) analysis suggests a multithermal nature and an average density of ~1.4 × 109 cm-3 for these microjets. Their thermal and kinetic energies were estimated to be ~3.9 × 1024 erg and ~2.9 × 1023 erg, respectively, which are of the same order of the released energy predicted by the nanoflare theory. Most events appear to be located at the edges of network lanes and magnetic flux concentrations, suggesting that these coronal microjets are likely generated by magnetic reconnection between small-scale magnetic loops and the adjacent network field. 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: Signatures of coronal hole substructure in the solar wind: combined Solar Orbiter remote sensing and in situ measurements Authors: Horbury, T. S.; Laker, R.; Rodriguez, L.; Steinvall, K.; Maksimovic, M.; Livi, S.; Berghmans, D.; Auchere, F.; Zhukov, A. N.; Khotyaintsev, Yu. V.; Woodham, L.; Matteini, L.; Stawarz, J.; Woolley, T.; Bale, S. D.; Rouillard, A.; O'Brien, H.; Evans, V.; Angelini, V.; Owen, C.; Solanki, S. K.; Nicula, B.; Muller, D.; Zouganelis, I. Bibcode: 2021arXiv210414960H Altcode: Context. The Sun's complex corona is the source of the solar wind and interplanetary magnetic field. While the large scale morphology is well understood, the impact of variations in coronal properties on the scale of a few degrees on properties of the interplanetary medium is not known. Solar Orbiter, carrying both remote sensing and in situ instruments into the inner solar system, is intended to make these connections better than ever before. Aims. We combine remote sensing and in situ measurements from Solar Orbiter's first perihelion at 0.5 AU to study the fine scale structure of the solar wind from the equatorward edge of a polar coronal hole with the aim of identifying characteristics of the corona which can explain the in situ variations. Methods. We use in situ measurements of the magnetic field, density and solar wind speed to identify structures on scales of hours at the spacecraft. Using Potential Field Source Surface mapping we estimate the source locations of the measured solar wind as a function of time and use EUI images to characterise these solar sources. Results. We identify small scale stream interactions in the solar wind with compressed magnetic field and density along with speed variations which are associated with corrugations in the edge of the coronal hole on scales of several degrees, demonstrating that fine scale coronal structure can directly influence solar wind properties and drive variations within individual streams. Conclusions. This early analysis already demonstrates the power of Solar Orbiter's combined remote sensing and in situ payload and shows that with future, closer perihelia it will be possible dramatically to improve our knowledge of the coronal sources of fine scale solar wind structure, which is important both for understanding the phenomena driving the solar wind and predicting its impacts at the Earth and elsewhere. Title: The Extreme ultraviolet imager onboard Solar Orbiter Authors: Berghmans, David; Harra, Louise K.; Zhukov, Andrei; Auchere, Frederic; Long, David; Schuehle, Udo; Rochus, Pierre Bibcode: 2021cosp...43E.949B Altcode: 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. 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. The EUI consists of three telescopes, the Full Sun Imager (FSI) and two High Resolution Imagers (HRIs), which are optimised to image in Lyman-$\alpha$ and EUV (174 \AA, 304 \AA) to provide a coverage from chromosphere up to corona. The EUI instrument design will be reviewed, and its scientific objectives and plans will be discussed. Early results of the EUI commissioning will be presented. 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: 3D Visualisation of Solar Data with JHelioviewer Authors: Mueller, D.; Nicula, B.; Verstringe, F.; Bourgoignie, B.; Csillaghy, A.; Laube, S.; Berghmans, D.; Ireland, J.; Fleck, B. Bibcode: 2020AGUFMSH0360001M Altcode: The Solar Orbiter and Parker Solar Probe missions focus on exploring the linkage between the Sun and the heliosphere. These new missions are collecting unique data that will allow us to study the coupling between macroscopic physical processes to those on kinetic scales, the generation of solar energetic particles and their propagation into the heliosphere and the origin and acceleration of solar wind plasma.

The scientific community now has access to large volumes of complex remote-sensing and in-situ observations from different vantage points, complemented by petabytes of simulation data. Answering overarching science questions like "How do solar transients drive heliospheric variability and space weather?" will only be possible if the science community has the necessary tools at hand to visualize these data and assimilate them into sophisticated models.

A key piece needed to bridge the gap between observables, derived quantities like magnetic field extrapolations and model output is a tool to routinely and intuitively visualise large heterogeneous, multidimensional, time-dependent data sets. The open-source JHelioviewer software, which is part of the ESA/NASA Helioviewer Project, is addressing this need. This contribution highlights recent extensions of JHelioviewer's functionality, in particular those of interest for Solar Orbiter. Title: The LUCI instrument Authors: West, M. J.; Kintziger, C.; Haberreiter, M.; Berghmans, D.; Gissot, S.; Golub, L.; Shestov, S.; Davies, J. A.; Luntama, J. P. Bibcode: 2020AGUFMSH0300007W Altcode: LUCI (Lagrange eUv Coronal Imager) is a solar imager in the Extreme UltraViolet (EUV) that is being developed as part of the Lagrange mission, a mission designed to be positioned at the L5 Lagrangian point to monitor space weather from its source on the Sun, through the heliosphere, to the Earth. LUCI will provide solar coronal images at a 2-3 minute cadence in a pass-band centred on 19.5 nm. Observations made through this pass-band allow for the detection and monitoring of semi-static coronal structures such as coronal holes, prominences, and active regions; as well as transient phenomena such as solar flares, limb Coronal Mass Ejections (CMEs), EUV waves, and coronal dimmings.

In this presentation I will discuss LUCI's latest design characteristics and the rationale behind several of the design decisions. I will present the observational advantages for space-weather monitoring from the L5 point, especially with an instrument such as LUCI, which will have a novel off-axis 'wide' field-of-view, designed to observe the solar disk extending out in to the middle corona, close to the the Sun-Earth line. I will present proxy data highlighting structures that can be seen in this region and the current roadmap for the instrument development. Title: Long-term Evolution of the Solar Corona Using PROBA2 Data Authors: West, M. J.; Mierla, M.; Janssens, J.; D'Huys, E.; Wauters, L.; Seaton, D. B.; Berghmans, D.; Podladchikova, O. Bibcode: 2020AGUFMSH0300011W Altcode: We use the SWAP imager onboard PROBA2 mission to study the evolution of large-scale EUV structures in the solar corona observed throughout Solar Cycle 24 (from 2010 to 2019). We look at the evolution of the coronal features on-disk and at different heights above the solar surface and compare them at different phases of the solar cycle, as well as with sunspot number evolution and with the PROBA2/LYRA signal. We find that the three time series (SWAP on-disk average brightness, sunspot number and LYRA irradiance) are very well correlated, with correlation coefficients around 0.9. Large-scale off-limb structures were visible from around March 2010 to around March 2016, meaning that they were absent at the minimum phase of solar activity. 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: 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: Solar Orbiter: connecting remote sensing and in situ measurements Authors: Horbury, T. S.; Auchere, F.; Antonucci, E.; Berghmans, D.; Bruno, R.; Carlsson, M.; del Toro Iniesta, J. C.; Fludra, A.; Harra, L.; Hassler, D.; Heinzel, P.; Howard, R. A.; Krucker, S.; Livi, S. A.; Long, D.; Louarn, P.; Maksimovic, M.; Mueller, D.; Owen, C. J.; Peter, H.; Rochus, P. L.; Rodriguez-Pacheco, J.; Romoli, M.; Schühle, U.; Solanki, S. K.; Teriaca, L.; Wimmer-Schweingruber, R. F.; Zouganelis, Y.; Laker, R. Bibcode: 2020AGUFMSH038..10H Altcode: A key science goal of the Solar Orbiter mission is to make connections between phenomena on the Sun and their manifestations in interplanetary space. To that end, the spacecraft carries a carefully tailored payload of six remote sensing instruments and four making in situ measurements. During June 2020, while the spacecraft was around 0.5 AU from the Sun, the remote sensing instruments operated for several days. While this was primarily an engineering activity, the resulting observations provided outstanding measurements and represent the ideal first opportunity to investigate the potential for making connections between the remote sensing and in situ payloads on Solar Orbiter.

We present a preliminary analysis of the available remote sensing and in situ observations, showing how connections can be made, and discuss the potential for further, more precise mapping to be performed as the mission progresses. Title: First Images and Initial In-Flight Performance of the Extreme Ultraviolet Imager On-Board Solar Orbiter. Authors: Auchere, F.; Gissot, S.; Teriaca, L.; Berghmans, D.; Harra, L.; Long, D.; Rochus, P. L.; Smith, P.; Schühle, U.; Stegen, K.; Aznar Cuadrado, R.; Heerlein, K.; Kraaikamp, E.; Verbeeck, C. Bibcode: 2020AGUFMSH0360025A Altcode: The Extreme Ultraviolet Imager (EUI) on board Solar Orbiter is composed of two High Resolution Imagers working at 121.6 (HRI-LYA, H I, chromosphere) and 17.4 nm (HRI-EUV, Fe IX/X, corona) and one dual-band Full Sun Imager (FSI) working at 30.4 nm (He II, transition region) and 17.4 nm (Fe IX/X, corona). During the commissioning period following the launch of Solar Orbiter and two and a half months of outgassing, EUI acquired its first solar images on May 12th, 2020 at about 0.67 AU. Most of the capabilities of the instrument have been tested during the following weeks, which revealed excellent overall performance. HRI-EUV already provided images with an angular resolution equivalent to ~0.6" (2 pixels) at 1 A.U. HRI-LYA will routinely provide images of the Sun at Lyman alpha, which have been otherwise relatively rare, with sub-second cadence capability. FSI will provide context for connection science but it will also explore regions of the corona never imaged before at EUV wavelengths, owing to its 3.8° field of view. EUI uses a complex on-board image processing system including advanced image compression and event detection algorithms. In particular, commissioning tests confirm the good performance of the compression, which is critical given the limited total telemetry volume imposed by the mission profile. In this paper, we present the main characteristics of the first images taken in each channel and we provide an initial assessment of the in-flight performance. 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: Very high-resolution observations of the solar atmosphere in H I Lyman alpha and Fe IX-X at 17.4 nm as seen by EUI aboard Solar Orbiter Authors: Aznar Cuadrado, R.; Berghmans, D.; Teriaca, L.; Gissot, S.; Schühle, U.; Auchere, F.; Harra, L.; Long, D.; Rochus, P. L.; Heerlein, K.; Kraaikamp, E.; Smith, P.; Stegen, K.; Verbeeck, C. Bibcode: 2020AGUFMSH0360026A Altcode: The Extreme Ultraviolet Imager (EUI) aboard Solar Orbiter consists of three telescopes, the Full Sun Imager (FSI) and two High Resolution Imagers (HRIs). The two HRI telescopes provide images of the base of the corona, near to the chromosphere, and of the 1 million K corona. In fact, the HRI-EUV telescope operates around 17.4 nm to obtain images dominated by emission from lines generated from Fe-IX and X ions, formed at about 1 MK, while the HRI-LYA telescope provides narrow band images dominated by the H I Lyman alpha line at 121.6 nm, formed in the upper chromosphere/lower transition region of the solar atmosphere around 20,000 K. Thus, the two imagers provide a powerful diagnostics of the solar structural organization, in terms of loop hierarchies and connectivity. Here we present an analysis of the first two near-simultaneous (within 15s) high-resolution images of the solar quiet atmosphere obtained near disk center by the two high-resolution telescopes on May 30th 2020, during the commissioning phase of the mission , when Solar Orbiter was at about 0.56 AU from the Sun. 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: Understanding the origins of the heliosphere: integrating observations and measurements from Parker Solar Probe, Solar Orbiter, and other space- and ground-based observatories Authors: Velli, M.; Harra, L. K.; Vourlidas, A.; Schwadron, N.; Panasenco, O.; Liewer, P. C.; Müller, D.; Zouganelis, I.; St Cyr, O. C.; Gilbert, H.; Nieves-Chinchilla, T.; 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.; Wimmer-Schweingruber, R. F.; Bale, S.; Kasper, J.; McComas, D. J.; Raouafi, N.; Martinez-Pillet, V.; Walsh, A. P.; De Groof, A.; Williams, D. Bibcode: 2020A&A...642A...4V Altcode: Context. The launch of Parker Solar Probe (PSP) in 2018, followed by Solar Orbiter (SO) in February 2020, has opened a new window in the exploration of solar magnetic activity and the origin of the heliosphere. These missions, together with other space observatories dedicated to solar observations, such as the Solar Dynamics Observatory, Hinode, IRIS, STEREO, and SOHO, with complementary in situ observations from WIND and ACE, and ground based multi-wavelength observations including the DKIST observatory that has just seen first light, promise to revolutionize our understanding of the solar atmosphere and of solar activity, from the generation and emergence of the Sun's magnetic field to the creation of the solar wind and the acceleration of solar energetic particles.
Aims: Here we describe the scientific objectives of the PSP and SO missions, and highlight the potential for discovery arising from synergistic observations. Here we put particular emphasis on how the combined remote sensing and in situ observations of SO, that bracket the outer coronal and inner heliospheric observations by PSP, may provide a reconstruction of the solar wind and magnetic field expansion from the Sun out to beyond the orbit of Mercury in the first phases of the mission. In the later, out-of-ecliptic portions of the SO mission, the solar surface magnetic field measurements from SO and the multi-point white-light observations from both PSP and SO will shed light on the dynamic, intermittent solar wind escaping from helmet streamers, pseudo-streamers, and the confined coronal plasma, and on solar energetic particle transport.
Methods: Joint measurements during PSP-SO alignments, and magnetic connections along the same flux tube complemented by alignments with Earth, dual PSP-Earth, and SO-Earth, as well as with STEREO-A, SOHO, and BepiColumbo will allow a better understanding of the in situ evolution of solar-wind plasma flows and the full three-dimensional distribution of the solar wind from a purely observational point of view. Spectroscopic observations of the corona, and optical and radio observations, combined with direct in situ observations of the accelerating solar wind will provide a new foundation for understanding the fundamental physical processes leading to the energy transformations from solar photospheric flows and magnetic fields into the hot coronal plasma and magnetic fields and finally into the bulk kinetic energy of the solar wind and solar energetic particles.
Results: We discuss the initial PSP observations, which already provide a compelling rationale for new measurement campaigns by SO, along with ground- and space-based assets within the synergistic context described above. Title: The Solar Orbiter mission. Science overview Authors: Müller, D.; St. Cyr, O. C.; Zouganelis, I.; Gilbert, H. R.; Marsden, R.; Nieves-Chinchilla, T.; Antonucci, E.; Auchère, F.; Berghmans, D.; Horbury, T. S.; Howard, R. A.; Krucker, S.; Maksimovic, M.; Owen, C. J.; Rochus, P.; Rodriguez-Pacheco, J.; Romoli, M.; Solanki, S. K.; Bruno, R.; Carlsson, M.; Fludra, A.; Harra, L.; Hassler, D. M.; Livi, S.; Louarn, P.; Peter, H.; Schühle, U.; Teriaca, L.; del Toro Iniesta, J. C.; Wimmer-Schweingruber, R. F.; Marsch, E.; Velli, M.; De Groof, A.; Walsh, A.; Williams, D. Bibcode: 2020A&A...642A...1M Altcode: 2020arXiv200900861M
Aims: Solar Orbiter, the first mission of ESA's Cosmic Vision 2015-2025 programme and a mission of international collaboration between ESA and NASA, will explore the Sun and heliosphere from close up and out of the ecliptic plane. It was launched on 10 February 2020 04:03 UTC from Cape Canaveral and aims to address key questions of solar and heliospheric physics pertaining to how the Sun creates and controls the Heliosphere, and why solar activity changes with time. To answer these, the mission carries six remote-sensing instruments to observe the Sun and the solar corona, and four in-situ instruments to measure the solar wind, energetic particles, and electromagnetic fields. In this paper, we describe the science objectives of the mission, and how these will be addressed by the joint observations of the instruments onboard.
Methods: The paper first summarises the mission-level science objectives, followed by an overview of the spacecraft and payload. We report the observables and performance figures of each instrument, as well as the trajectory design. This is followed by a summary of the science operations concept. The paper concludes with a more detailed description of the science objectives.
Results: Solar Orbiter will combine in-situ measurements in the heliosphere with high-resolution remote-sensing observations of the Sun to address fundamental questions of solar and heliospheric physics. The performance of the Solar Orbiter payload meets the requirements derived from the mission's science objectives. Its science return will be augmented further by coordinated observations with other space missions and ground-based observatories.

ARRAY(0x207ce98) 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: LUCI onboard Lagrange, the next generation of EUV space weather monitoring Authors: West, Matthew J.; Kintziger, Christian; Haberreiter, Margit; Gyo, Manfred; Berghmans, David; Gissot, Samuel; Büchel, Valeria; Golub, Leon; Shestov, Sergei; Davies, Jackie A. Bibcode: 2020JSWSC..10...49W Altcode: 2020arXiv200904788W Lagrange eUv Coronal Imager (LUCI) is a solar imager in the Extreme UltraViolet (EUV) that is being developed as part of the Lagrange mission, a mission designed to be positioned at the L5 Lagrangian point to monitor space weather from its source on the Sun, through the heliosphere, to the Earth. LUCI will use an off-axis two mirror design equipped with an EUV enhanced active pixel sensor. This type of detector has advantages that promise to be very beneficial for monitoring the source of space weather in the EUV. LUCI will also have a novel off-axis wide field-of-view, designed to observe the solar disk, the lower corona, and the extended solar atmosphere close to the Sun-Earth line. LUCI will provide solar coronal images at a 2-3 min cadence in a pass-band centred on 19.5. Observations made through this pass-band allow for the detection and monitoring of semi-static coronal structures such as coronal holes, prominences, and active regions; as well as transient phenomena such as solar flares, limb coronal mass ejections (CMEs), EUV waves, and coronal dimmings. The LUCI data will complement EUV solar observations provided by instruments located along the Sun-Earth line such as PROBA2-SWAP, SUVI-GOES and SDO-AIA, as well as provide unique observations to improve space weather forecasts. Together with a suite of other remote-sensing and in-situ instruments onboard Lagrange, LUCI will provide science quality operational observations for space weather monitoring. Title: Long-Term Evolution of the Solar Corona Using PROBA2 Data Authors: Mierla, Marilena; Janssens, Jan; D'Huys, Elke; Wauters, Laurence; West, Matthew J.; Seaton, Daniel B.; Berghmans, David; Podladchikova, Elena Bibcode: 2020SoPh..295...66M Altcode: 2020arXiv200409785M We use The Sun Watcher with Active Pixel System detector and Image Processing (SWAP) imager onboard the Project for Onboard Autonomy 2 (PROBA2) mission to study the evolution of large-scale EUV structures in the solar corona observed throughout Solar Cycle 24 (from 2010 to 2019). We discuss the evolution of the on-disk coronal features and at different heights above the solar surface based on EUV intensity changes. We also look at the evolution of the corona in equatorial and polar regions and compare them at different phases of the solar cycle, as well as with sunspot-number evolution and with the PROBA2/Large Yield RAdiometer (LYRA) signal. The main results are as follows: The three time series (SWAP on-disk average brightness, sunspot number, and LYRA irradiance) are very well correlated, with correlation coefficients around 0.9. The average rotation rate of bright features at latitudes of +15∘, 0∘, and −15∘ was around 15 degree day−1 throughout the period studied. A secondary peak in EUV averaged intensity at the poles was observed on the descending phase of SC24. These peaks (at North and South Poles, respectively) seem to be associated with the start of the development of the (polar) coronal holes. Large-scale off-limb structures were visible from around March 2010 to around March 2016, meaning that they were absent at the minimum phase of solar activity. A fan at the North Pole persisted for more than 11 Carrington rotations (February 2014 to March 2015), and it could be seen up to altitudes of 1.6 R⊙. Title: The Solaris Solar Polar Mission Authors: Hassler, Donald M.; Newmark, Jeff; Gibson, Sarah; Harra, Louise; Appourchaux, Thierry; Auchere, Frederic; Berghmans, David; Colaninno, Robin; Fineschi, Silvano; Gizon, Laurent; Gosain, Sanjay; Hoeksema, Todd; Kintziger, Christian; Linker, John; Rochus, Pierre; Schou, Jesper; Viall, Nicholeen; West, Matt; Woods, Tom; Wuelser, Jean-Pierre Bibcode: 2020EGUGA..2217703H Altcode: The solar poles are one of the last unexplored regions of the solar system. Although Ulysses flew over the poles in the 1990s, it did not have remote sensing instruments onboard to probe the Sun's polar magnetic field or surface/sub-surface flows.We will discuss Solaris, a proposed Solar Polar MIDEX mission to revolutionize our understanding of the Sun by addressing fundamental questions that can only be answered from a polar vantage point. Solaris uses a Jupiter gravity assist to escape the ecliptic plane and fly over both poles of the Sun to >75 deg. inclination, obtaining the first high-latitude, multi-month-long, continuous remote-sensing solar observations. Solaris will address key outstanding, breakthrough problems in solar physics and fill holes in our scientific understanding that will not be addressed by current missions.With focused science and a simple, elegant mission design, Solaris will also provide enabling observations for space weather research (e.g. polar view of CMEs), and stimulate future research through new unanticipated discoveries. Title: The Solar Orbiter EUI instrument: The Extreme Ultraviolet Imager Authors: Rochus, P. L.; Auchere, F.; Berghmans, D.; Harra, L.; Schmutz, W. K.; Schühle, U. Bibcode: 2019AGUFMSH21D3291R Altcode: 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.

EUI aims at improving our understanding of the structure and dynamics of the solar atmosphere. EUI will take images of the solar atmosphere, globally as well as at high resolution, and from high solar latitude perspectives.

EUI consists of 3 telescopes that are optimized to image in Lyman-a and EUV 17.4nm and 30.4 nm to provide a coverage from chromosphere up to corona. EUI is designed to cope with the strong constraints that Solar Orbiter has as a deep space mission. Limited telemetry availability is compensated by state-of-the-art image compression, on board image processing and event selection. The imposed power limitations and potentially harsh radiation environment lead to the usage of novel CMOS sensors. As the unobstructed field of view of the telescopes needs to protrude through the spacecraft heat shield, the apertures were kept as small as possible. This lead to a systematic effort to optimize the throughput of every optical element and the reduction of noise levels in the sensor.

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 on board software, the intended operations, the ground software and the foreseen data products.

EUI will bring unique science opportunities thanks to its specific design, its viewpoint and thanks to the planned synergies with the other Solar Orbiter instruments. We highlight in particular 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: From PROBA2/SWAP to Solar Orbiter/EUI: exploring the outer edge of the EUV corona. Authors: Berghmans, D.; D'Huys, E.; Zhukov, A.; Auchere, F. Bibcode: 2019AGUFMSH13A..01B Altcode: SWAP is a small coronal EUV imager onboard the ESA microsatellite PROBA2. Thanks to its large field of view (54 arcmin), spacecraft offpoints and applied image processing, SWAP has been able to show the structures of the EUV corona more than 1 Rsun above the limb. This "middle corona" is in between the classical off limb EUV corona as seen by e.g. SDO/AIA and the much further white light corona as seen by e.g. the LASCO coronagraphs and is thus a poorly observed region. The Middle Corona harbours interesting physics, as it is here where the solar wind accelerates and the topology of streamers and pseudo-streamers fade in the solar wind. SWAP imagery has shown how 'coronal fan' structures in the middle corona survive many solar rotations and how the extended corona above the solar poles reverses polarity. The Full Sun Imager (FSI, part of Extreme Ultraviolet Imager EUI onboard Solar Orbiter) will take this further with a field of view of 228 arcmin. Furthermore, as embarked on the Solar Orbiter mission (launch 2020) FSI will be the first to image all this from out of the ecliptic. In this paper we will review the Middle Corona results of SWAP and provide an outlook on what to expect from EUI/FSI. Title: PECASUS, European Space Weather Service Network for Aviation Authors: Harri, A. M.; Kauristie, K.; Andries, J.; Gibbs, M.; Beck, P.; Berdermann, J.; Perrone, L.; van den Oord, B.; Berghmans, D.; Bergeot, N.; De Donder, E.; Latocha, M.; Dierckxsens, M.; Haralambous, H.; Stanislawska, I. M.; Wilken, V.; Romano, V.; Kriegel, M.; Österberg, K. Bibcode: 2019AGUFMSA33D3168H Altcode: The PECASUS Consortium (European Consortium for Aviation Space weather User Services) will provide a space weather service focusing on the dissemination of warning messages ('advisories') towards aviation actors and corresponds to extreme space weather events with impact on aviation GNSS systems, HF communication and radiation levels at flight altitudes. In November 2018 ICAO (International Civil Aviation Organization) designated three global space weather service centers to be operated by the European PECASUS consortium, by United States and by the consortium of Australia, Canada, France and Japan.

PECASUS was set-up as a consortium bringing together a number of European partners with proven space weather service capabilities. The PECASUS consortium is coordinated by FMI (Finland) who is also the ultimate responsible for communications towards the aviation sector. The Advisory Messages are produced by STCE (Belgium) on the basis of expert interpretation and data streams produced by DLR (Germany), INGV (Italy), Seibersdorf Laboratories (Austria), STCE (Belgium), SRC (Poland) and FU (Cyprus). In addition, the MetOffice (UK) will act as a resilience node in case of a major failure in the network, while the KNMI (The Netherlands) will take care of user liaison and monitor the PECASUS performance.

The PECASUS Consortium was audited in February 2018 by space weather and operational management experts, nominated by the World Meteorological Organisation (WMO). The audit addressed a broad spectrum of criteria under Institutional, Operational, Technical and Communication/ Dissemination categories. PECASUS was declared fully compliant in all ICAO/WMO criteria with no areas for improvement identified.

In this presentation we will describe the coordinated action of three ICAO Space Weather Centers, PECASUS network and its operations, and the vision of the PECASUS team to move forward. User interactions such as education and training, user feedback at ESWW, product and performance verification are part of PECASUS operations. Title: Assessment and recommendations for a consolidated European approach to space weather - as part of a global space weather effort Authors: Opgenoorth, Hermann J.; Wimmer-Schweingruber, Robert F.; Belehaki, Anna; Berghmans, David; Hapgood, Mike; Hesse, Michael; Kauristie, Kirsti; Lester, Mark; Lilensten, Jean; Messerotti, Mauro; Temmer, Manuela Bibcode: 2019JSWSC...9A..37O Altcode: Over the last 10-20 years there has been an ever-increasing international awareness of risks to modern society from adverse and potentially harmful - and in extreme cases even disastrous - space weather events. Many individual countries and even international organisations like the United Nations (UN) have begun to increase their activities in preparing for and mitigating effects of adverse space weather. As in the rest of the world there is also in Europe an urgent need for coordination of Space Weather efforts in individual countries as well as in and among European organisations such as the European Space Agency (ESA) and the European Union (EU). This coordination should not only improve our ability to meet space weather risks, but also enable Europe to contribute to on-going global space weather efforts. While space weather is a global threat, which needs a global response, it also requires tailored regional and trans-regional responses that require coordination at all levels. Commissioned by the European Space Science Committee (ESSC) of the European Science Foundation, the authors - together with ex-officio advice from ESA and the EU - have over two years assessed European activities in the realm of space weather and formulated a set of recommendations to ESA, the EU and their respective member states, about how to prepare Europe for the increasing impact of adverse space weather effects on man-made infrastructure and our society as a whole. We have also analysed parallel international activities worldwide, and we give advice how Europe could incorporate its future activities into a global scheme. Title: The EUI instrument onboard Solar Orbiter: the EUV corona imaged differently Authors: Berghmans, David; Rochus, Pierre; Auchère, Frédéric; Harra, Louise; Schmutz, Werner; Schühle, Udo Bibcode: 2018csc..confE..73B Altcode: The ESA Solar Orbiter mission is designed to determine how the Sun creates and controls the heliosphere. The spacecraft will bring a combination of in situ and remote sensing instruments out of the ecliptic (>30°) and close to the sun (0.3 solar-radii). The launch of Solar Orbiter is expected (not earlier than) Feb 2019. The Extreme Ultraviolet Imager is part of the remote-sensing package of Solar Orbiter, to be operating during 3 ten-day periods of each orbit around the Sun, which last roughly half a year. These 3 periods will correspond to perihelion and maximal solar latitude north and south. The Extreme Ultraviolet Imager is itself a suite of three UV and EUV telescopes that observe the solar atmosphere both globally as well as at very high resolution. The two high-resolution imagers (HRIs) will image the solar atmosphere in the chromospheric Lyman alpha line and the coronal 17nm pass band with a resolution of 0.5 arcsec. From perihelion, this will correspond to a pixel footprint on the solar disc of (110km)^2 . The Full Sun Imager (FSI), working at the 17.4 nm and 30.4 nm EUV passbands, will provide a global view of the solar atmosphere and is therefore an essential building block for the "connection science" of the Solar Orbiter mission. The FSI field of view is large enough (228arcmin) that, even at perihelion and at maximal off-points by Solar Orbiter, the full solar disk remains in the field of view. This large FOV and the FSI's high sensitivity will allow to image the "transition corona" where the topology of streamers and pseudo-streamers fades in the solar wind. Furthermore, FSI will be the first to image all this from out of the ecliptic. In this talk we will give an overview of the EUI instrument. We will focus on the novel aspects of EUI that will allow it to image beyond what previous EUV imagers could show us: EUV imaging from the highest solar latitude, with the widest field-of-view and at highest spatial resolution. Title: Long-term evolution of the solar corona using SWAP data Authors: Mierla, Marilena; D'Huys, Elke; Seaton, Daniel B.; Berghmans, David; West, Matt; Podladchikova, Elena; Wauters, Laurence; Janssens, Jan Bibcode: 2018csc..confE..78M Altcode: In this work, we use the PROBA2/SWAP images to study the evolution of the large-scale structures of the solar corona observed in the EUV during the solar cycle 24 (from 2010 to 2018). We will discuss the evolution of the corona at different heights above the solar surface and the evolution of the corona over the poles. We compare it with the sunspot number evolution. Title: Space Weather JHelioviewer in a Heterogeneous World Authors: West, Matthew; Berghmans, David; Mueller, Daniel; Jiggens, Piers; Verstringe, Freek; Nicula, Bogdan; Bourgoignie, Bram Bibcode: 2018cosp...42E3643W Altcode: The Space Weather JHelioviewer project aims to augment the freely available services of the Helioviewer project with space weather relevant capabilities. As such, it merges the output of several networked software services by combining the display of 1D data (timelines), 2D data (solar images and spectrograms), 3D data (multispacecraft imaging, magnetic field lines mod- elling), solar event detections (e.g., HEK), and space weather alerts. This talk will highlight the experiences gathered while incorporating this system with several diverse datasets and services. Title: The EUI flight instrument of Solar Orbiter: from optical alignment to end-to-end calibration Authors: Halain, J. -P.; Renotte, E.; Auchère, F.; Berghmans, D.; Delmotte, F.; Harra, L.; Schmutz, W.; Schühle, U.; Aznar Cuadrado, R.; Dumesnil, C.; Gyo, M.; Kennedy, T.; Verbeeck, C.; Barbay, J.; Giordanengo, B.; Gissot, S.; Gottwald, A.; Heerlein, K.; Hellin, M. -L.; Hermans, A.; Hervier, V.; Jacques, L.; Laubis, C.; Mazzoli, A.; Meining, S.; Mercier, R.; Philippon, A.; Roose, S.; Rossi, L.; Scholze, F.; Smith, P.; Teriaca, L.; Zhang, X.; Rochus, P. Bibcode: 2018SPIE10699E..0HH Altcode: The Extreme Ultraviolet Imager (EUI) instrument for the Solar Orbiter mission will image the solar corona in the extreme ultraviolet (17.1 nm and 30.4 nm) and in the vacuum ultraviolet (121.6 nm) spectral ranges. The development of the EUI instrument has been successfully completed with the optical alignment of its three channels' telescope, the thermal and mechanical environmental verification, the electrical and software validations, and an end-toend on-ground calibration of the two-units' flight instrument at the operating wavelengths. The instrument has been delivered and installed on the Solar Orbiter spacecraft, which is now undergoing all preparatory activities before launch. Title: The detection of ultra-relativistic electrons in low Earth orbit Authors: Katsiyannis, Athanassios C.; Dominique, Marie; Pierrard, Viviane; Rosson, Graciela Lopez; Keyser, Johan De; Berghmans, David; Kruglanski, Michel; Dammasch, Ingolf E.; Donder, Erwin De Bibcode: 2018JSWSC...8A...1K Altcode: 2017arXiv171004653K
Aims: To better understand the radiation environment in low Earth orbit (LEO), the analysis of in-situ observations of a variety of particles, at different atmospheric heights, and in a wide range of energies, is needed.
Methods: We present an analysis of energetic particles, indirectly detected by the large yield radiometer (LYRA) instrument on board ESA's project for on-board autonomy 2 (PROBA2) satellite as background signal. Combining energetic particle telescope (EPT) observations with LYRA data for an overlapping period of time, we identified these particles as electrons with an energy range of 2 to 8 MeV.
Results: The observed events are strongly correlated to geo-magnetic activity and appear even during modest disturbances. They are also well confined geographically within the L = 4-6 McIlwain zone, which makes it possible to identify their source.
Conclusions: Although highly energetic particles are commonly perturbing data acquisition of space instruments, we show in this work that ultra-relativistic electrons with energies in the range of 2-8 MeV are detected only at high latitudes, while not present in the South Atlantic Anomaly region. Title: 3D Visualization of Solar Data: Preparing for Solar Orbiter and Parker Solar Probe Authors: Mueller, D.; Nicula, B.; Felix, S.; Verstringe, F.; Bourgoignie, B.; Csillaghy, A.; Berghmans, D.; Jiggens, P.; Ireland, J.; Fleck, B. Bibcode: 2017AGUFMSH23D2686M Altcode: Solar Orbiter and Parker Solar Probe will focus on exploring the linkage between the Sun and the heliosphere. These new missions will collect unique data that will allow us to study, e.g., the coupling between macroscopic physical processes to those on kinetic scales, the generation of solar energetic particles and their propagation into the heliosphere and the origin and acceleration of solar wind plasma. Combined with the several petabytes of data from NASA's Solar Dynamics Observatory, the scientific community will soon have access to multi­dimensional remote-sensing and complex in-situ observations from different vantage points, complemented by petabytes of simulation data. Answering overarching science questions like "How do solar transients drive heliospheric variability and space weather?" will only be possible if the community has the necessary tools at hand. In this contribution, we will present recent progress in visualizing the Sun and its magnetic field in 3D using the open-source JHelioviewer framework, which is part of the ESA/NASA Helioviewer Project. Title: Performances of swap on-board PROBA-2 Authors: Halain, J. -P.; Berghmans, D.; Defise, J. -F.; Rochus, P.; Nicula, B.; de Groof, A.; Seaton, D. Bibcode: 2017SPIE10565E..0SH Altcode: The PROBA2 mission has been launched on 2nd November2009 with a Rockot launcher to a Sunsynchronous orbit at an altitude of 725 km. Its nominal operation duration is two years with possible extension of 2 years. PROBA2 is a small satellite developed under an ESA General Support Technology Program (GSTP) contract to perform an in-flight demonstration of new space technologies and support a scientific mission for a set of selected instruments. The mission is tracked by the ESA Redu Mission Operation Center. Title: EUV high resolution imager on-board solar orbiter: optical design and detector performances Authors: Halain, J. P.; Mazzoli, A.; Rochus, P.; Renotte, E.; Stockman, Y.; Berghmans, D.; BenMoussa, A.; Auchère, F. Bibcode: 2017SPIE10564E..3VH Altcode: The EUV high resolution imager (HRI) channel of the Extreme Ultraviolet Imager (EUI) on-board Solar Orbiter will observe the solar atmospheric layers at 17.4 nm wavelength with a 200 km resolution. The HRI channel is based on a compact two mirrors off-axis design. The spectral selection is obtained by a multilayer coating deposited on the mirrors and by redundant Aluminum filters rejecting the visible and infrared light. The detector is a 2k x 2k array back-thinned silicon CMOS-APS with 10 μm pixel pitch, sensitive in the EUV wavelength range. Due to the instrument compactness and the constraints on the optical design, the channel performance is very sensitive to the manufacturing, alignments and settling errors. A trade-off between two optical layouts was therefore performed to select the final optical design and to improve the mirror mounts. The effect of diffraction by the filter mesh support and by the mirror diffusion has been included in the overall error budget. Manufacturing of mirror and mounts has started and will result in thermo-mechanical validation on the EUI instrument structural and thermal model (STM). Because of the limited channel entrance aperture and consequently the low input flux, the channel performance also relies on the detector EUV sensitivity, readout noise and dynamic range. Based on the characterization of a CMOS-APS back-side detector prototype, showing promising results, the EUI detector has been specified and is under development. These detectors will undergo a qualification program before being tested and integrated on the EUI instrument. Title: JHelioviewer. Time-dependent 3D visualisation of solar and heliospheric data Authors: Müller, D.; Nicula, B.; Felix, S.; Verstringe, F.; Bourgoignie, B.; Csillaghy, A.; Berghmans, D.; Jiggens, P.; García-Ortiz, J. P.; Ireland, J.; Zahniy, S.; Fleck, B. Bibcode: 2017A&A...606A..10M Altcode: 2017arXiv170507628M Context. Solar observatories are providing the world-wide community with a wealth of data, covering wide time ranges (e.g. Solar and Heliospheric Observatory, SOHO), multiple viewpoints (Solar TErrestrial RElations Observatory, STEREO), and returning large amounts of data (Solar Dynamics Observatory, SDO). In particular, the large volume of SDO data presents challenges; the data are available only from a few repositories, and full-disk, full-cadence data for reasonable durations of scientific interest are difficult to download, due to their size and the download rates available to most users. From a scientist's perspective this poses three problems: accessing, browsing, and finding interesting data as efficiently as possible.
Aims: To address these challenges, we have developed JHelioviewer, a visualisation tool for solar data based on the JPEG 2000 compression standard and part of the open source ESA/NASA Helioviewer Project. Since the first release of JHelioviewer in 2009, the scientific functionality of the software has been extended significantly, and the objective of this paper is to highlight these improvements.
Methods: The JPEG 2000 standard offers useful new features that facilitate the dissemination and analysis of high-resolution image data and offers a solution to the challenge of efficiently browsing petabyte-scale image archives. The JHelioviewer software is open source, platform independent, and extendable via a plug-in architecture.
Results: With JHelioviewer, users can visualise the Sun for any time period between September 1991 and today; they can perform basic image processing in real time, track features on the Sun, and interactively overlay magnetic field extrapolations. The software integrates solar event data and a timeline display. Once an interesting event has been identified, science quality data can be accessed for in-depth analysis. As a first step towards supporting science planning of the upcoming Solar Orbiter mission, JHelioviewer offers a virtual camera model that enables users to set the vantage point to the location of a spacecraft or celestial body at any given time. Title: Multi-instrument observations of the solar eclipse on 20 March 2015 and its effects on the ionosphere over Belgium and Europe Authors: Stankov, Stanimir M.; Bergeot, Nicolas; Berghmans, David; Bolsée, David; Bruyninx, Carine; Chevalier, Jean-Marie; Clette, Frédéric; De Backer, Hugo; De Keyser, Johan; D'Huys, Elke; Dominique, Marie; Lemaire, Joseph F.; Magdalenić, Jasmina; Marqué, Christophe; Pereira, Nuno; Pierrard, Viviane; Sapundjiev, Danislav; Seaton, Daniel B.; Stegen, Koen; Van der Linden, Ronald; Verhulst, Tobias G. W.; West, Matthew J. Bibcode: 2017JSWSC...7A..19S Altcode: A total solar eclipse occurred on 20 March 2015, with a totality path passing mostly above the North Atlantic Ocean, which resulted in a partial solar eclipse over Belgium and large parts of Europe. In anticipation of this event, a dedicated observational campaign was set up at the Belgian Solar-Terrestrial Centre of Excellence (STCE). The objective was to perform high-quality observations of the eclipse and the associated effects on the geospace environment by utilising the advanced space- and ground-based instrumentation available to the STCE in order to further our understanding of these effects, particularly on the ionosphere. The study highlights the crucial importance of taking into account the eclipse geometry when analysing the ionospheric behaviour during eclipses and interpreting the eclipse effects. A detailed review of the eclipse geometry proves that considering the actual obscuration level and solar zenith angle at ionospheric heights is much more important for the analysis than at the commonly referenced Earth's surface or at the plasmaspheric heights. The eclipse occurred during the recovery phase of a strong geomagnetic storm which certainly had an impact on (some of) the ionospheric characteristics and perhaps caused the omission of some "low-profile" effects. However, the analysis of the ionosonde measurements, carried out at unprecedented high rates during the eclipse, suggests the occurrence of travelling ionospheric disturbances (TIDs). Also, the high temporal and spatial resolution measurements proved very important in revealing and estimating some finer details of the delay in the ionospheric reaction and the ionospheric disturbances. Title: Provision of space weather bulletins in support to ESA missions Authors: Kruglanski, Michel; Devos, Andy; Calders, Stijn; De Donder, Erwin; Berghmans, David; Andries, Jesse; Crosby, Norma; Dierckxsens, Mark; Glover, Alexi Bibcode: 2017EGUGA..1918071K Altcode: The SSCC (SSA Space Weather Coordination Centre) is the focal point for user support of the ESA Space Situational Awareness (SSA) Program Space Weather Service Network (http://swe.ssa.esa.int/) and offers first line support to end-users. Its activities are gradually expanding as more products and tools are incorporated in the associated Network. Here we report on the tailoring of the network resources at the SSCC in order to produce space weather forecast notifications in support to selected ESA missions. With the help of forecasters from the Expert Service Centres (ECSs) for Solar Weather and for Space Radiation, the SSCC already has provided dedicated notifications for various missions including the launch window and the L2 insertion manoeuvre of the GAIA mission, for the last aerobraking campaign of Venus Express, during the trajectory around Comet 67P/Churyumov-Gerasimenko of the Rosetta mission and the landing of Philae lander, for the flight of the experimental IXV space plane, and for the launch LISA Pathfinder mission and during the operations phase at L1. Examples of space weather notification will be given. Those exercises are performed in a test and evaluation context helping to evaluate the network capabilities and to identify recommendations for improvement. Title: Solar signatures and eruption mechanism of the August 14, 2010 coronal mass ejection (CME) Authors: D'Huys, Elke; Seaton, Daniel B.; De Groof, Anik; Berghmans, David; Poedts, Stefaan Bibcode: 2017JSWSC...7A...7D Altcode: 2017arXiv170108814D On August 14, 2010 a wide-angled coronal mass ejection (CME) was observed. This solar eruption originated from a destabilized filament that connected two active regions and the unwinding of this filament gave the eruption an untwisting motion that drew the attention of many observers. In addition to the erupting filament and the associated CME, several other low-coronal signatures that typically indicate the occurrence of a solar eruption were associated with this event. However, contrary to what was expected, the fast CME (v > 900 km s-1) was accompanied by only a weak C4.4 flare. We investigate the various eruption signatures that were observed for this event and focus on the kinematic evolution of the filament in order to determine its eruption mechanism. Had this solar eruption occurred just a few days earlier, it could have been a significant event for space weather. The risk of underestimating the strength of this eruption based solely on the C4.4 flare illustrates the need to include all eruption signatures in event analyses in order to obtain a complete picture of a solar eruption and assess its possible space weather impact. Title: The discovery of an electron current at Earth's McIlwain L=6 Authors: Katsiyannis, A. C.; Dominique, M.; Pierrard, V.; Borremans, K.; De Keyser, J.; Berghmans, D.; Kruglanski, M.; Dammasch, I.; De Donder, E. Bibcode: 2016usc..confE..44K Altcode: The Large Yield RAdiometer (LYRA) is an ultraviolet solar radiometer on-board ESA's PROBA2 micro-satellite. Since its launch in 2009 to an altitude of 735km, one of the most peculiar and intriguing results of LYRA is the detection of short, strong, bursts that do not directly correlate with solar coronal events, nor with pointing of the instrument to Earth's upper atmosphere, but correlate well with high a_p index on Earth's surface and the crossing by the satellite of the L=6 shell. Very similar detections were more recently made by the Energetic Particles Telescope (EPT) on board the PROBA-V micro-satellite, establishing the identification of the detections as relativistic electrons of the 2.4-8 MeV energy range. Several attributes of those detections, including their dependency to various space weather indexes (ap, D_st, etc), their geographical distribution, a dawn/dusk asymmetry and others will be presented. Open questions related to the discovery of this phenomenon will also be discussed. Title: The qualification campaign of the EUI instrument of Solar Orbiter Authors: Halain, J. -P.; Rochus, P.; Renotte, E.; Hermans, A.; Jacques, L.; Mazzoli, A.; Auchère, F.; Berghmans, D.; Harra, L.; Schühle, U.; Schmutz, W.; Aznar Cuadrado, R.; Dumesnil, C.; Gyo, M.; Kennedy, T.; Verbeeck, C.; Smith, P. Bibcode: 2016SPIE.9905E..2XH Altcode: The Extreme Ultraviolet Imager (EUI) instrument is one of the ten scientific instruments on board the Solar Orbiter mission to be launched in October 2018. It will provide full-sun and high-resolution images of the solar corona in the extreme ultraviolet (17.1 nm and 30.4 nm) and in the vacuum ultraviolet (121.6 nm). The validation of the EUI instrument design has been completed with the Assembly, Integration and Test (AIT) of the instrument two-units Qualification Model (QM). Optical, electrical, electro-magnetic compatibility, thermal and mechanical environmental verifications were conducted and are summarized here. The integration and test procedures for the Flight Model (FM) instrument and sub-systems were also verified. Following the Qualification Review, the flight instrument activities were started with the assembly of the flight units. The mechanical and thermal acceptance tests and an end-to-end final calibration in the (E)UV will then be conducted before delivery for integration on the Solar Orbiter Spacecraft by end of 2016. Title: The Effect of Limited Sample Sizes on the Accuracy of the Estimated Scaling Parameter for Power-Law-Distributed Solar Data Authors: D'Huys, Elke; Berghmans, David; Seaton, Daniel B.; Poedts, Stefaan Bibcode: 2016SoPh..291.1561D Altcode: 2016arXiv160506972D; 2016SoPh..tmp...82D Many natural processes exhibit a power-law behavior. The power-law exponent is linked to the underlying physical process, and therefore its precise value is of interest. With respect to the energy content of nanoflares, for example, a power-law exponent steeper than 2 is believed to be a necessary condition for solving the enigmatic coronal heating problem. Studying power-law distributions over several orders of magnitudes requires sufficient data and appropriate methodology. In this article we demonstrate the shortcomings of some popular methods in solar physics that are applied to data of typical sample sizes. We use synthetic data to study the effect of the sample size on the performance of different estimation methods. We show that vast amounts of data are needed to obtain a reliable result with graphical methods (where the power-law exponent is estimated by a linear fit on a log-transformed histogram of the data). We revisit published results on power laws for the angular width of solar coronal mass ejections and the radiative losses of nanoflares. We demonstrate the benefits of the maximum likelihood estimator and advocate its use. Title: Observing the Unobservable: Identification and Characterisation of Stealth Coronal Mass Ejections Authors: D'Huys, Elke; Seaton, Daniel B.; Poedts, Stefaan; Berghmans, David Bibcode: 2016SPD....4740401D Altcode: I will present my doctoral thesis research on stealth CMEs: solar coronal mass ejections that are clearly observed in coronagraph data but do not show significant low-coronal or on-disk signatures of eruption. This lack of coronal signatures makes it challenging to determine their source region and predict their trajectory throughout interplanetary space. We identified 40 such events and investigated their properties both observationally and statistically. We found that our sample size was insufficient to determine the scaling law for the CME angular width reliably. We therefore analyzed in general what the effect is of a limited sample size on the estimation of a power law parameter. Armed with this knowledge, we returned to our sample of stealth CMEs, re-analyzed the power law for their angular widths and compared the results to the power law found for normal CMEs. Title: Validation of Earth atmosphere models using solar EUV observations from the CORONAS and PROBA2 satellites in occultation mode Authors: Slemzin, Vladimir; Ulyanov, Artyom; Gaikovich, Konstantin; Kuzin, Sergey; Pertsov, Andrey; Berghmans, David; Dominique, Marie Bibcode: 2016JSWSC...6A...7S Altcode: Aims: Knowledge of properties of the Earth's upper atmosphere is important for predicting the lifetime of low-orbit spacecraft as well as for planning operation of space instruments whose data may be distorted by atmospheric effects. The accuracy of the models commonly used for simulating the structure of the atmosphere is limited by the scarcity of the observations they are based on, so improvement of these models requires validation under different atmospheric conditions. Measurements of the absorption of the solar extreme ultraviolet (EUV) radiation in the upper atmosphere below 500 km by instruments operating on low-Earth orbits (LEO) satellites provide efficient means for such validation as well as for continuous monitoring of the upper atmosphere and for studying its response to the solar and geomagnetic activity. Method: This paper presents results of measurements of the solar EUV radiation in the 17 nm wavelength band made with the SPIRIT and TESIS telescopes on board the CORONAS satellites and the SWAP telescope on board the PROBA2 satellite in the occulted parts of the satellite orbits. The transmittance profiles of the atmosphere at altitudes between 150 and 500 km were derived from different phases of solar activity during solar cycles 23 and 24 in the quiet state of the magnetosphere and during the development of a geomagnetic storm. We developed a mathematical procedure based on the Tikhonov regularization method for solution of ill-posed problems in order to retrieve extinction coefficients from the transmittance profiles. The transmittance profiles derived from the data and the retrieved extinction coefficients are compared with simulations carried out with the NRLMSISE-00 atmosphere model maintained by Naval Research Laboratory (USA) and the DTM-2013 model developed at CNES in the framework of the FP7 project ATMOP. Results: Under quiet and slightly disturbed magnetospheric conditions during high and low solar activity the extinction coefficients calculated by both models agreed with the measurements within the data errors. The NRLMSISE-00 model was not able to predict the enhancement of extinction above 300 km observed after 14 h from the beginning of a geomagnetic storm whereas the DTM-2013 model described this variation with good accuracy. Title: PROBA2: a Micro-Satellite Observing the Sun Authors: Katsiyannis, A.; Dominique, M.; Seaton, D. B.; Berghmans, D.; West, M. J.; Dolla, L.; Ryan, D.; Bonte, K.; Kretzschmar, M.; Dammasch, I. E.; Wauters, L.; Rachmeler, L. A. Bibcode: 2015AGUFMSH21B2415K Altcode: PROBA2 (http://proba2.oma.be) is an ESA micro-satellite that was launched in November 2009. It carries two solar-observing instruments: SWAP, an EUV imager observing the one-million-degree corona, and LYRA, a UV-EUV radiometer acquiring time-series in four broadband channels. The characteristics of both instruments make them highly complementary to bigger missions such as SDO for the observation of solar eruptions and flares. SWAP benefits from a large field-of-view and flexible off-pointing capabilities that allow the instrument to fill part of the observational gap between imagers and coronographs and to shed a new light on eruptive events (see e.g. West and Seaton, 2015; Kumar and Cho, 2014; Byrne et al., 2014) LYRA acquires at a very fast cadence (20 Hz nominally) and with a high signal-to-noise ratio, and can therefore be used for the detailed analysis of the short-timescale variations of solar irradiance, such as the so-called quasi-periodic pulsations appearing in flares that could be intrinsically related to the nature of the flaring process (see e.g. Dolla et al., 2012). The two instruments provide data suitable for the detection of space weather related events such as flares, CMEs, dimmings, EUV waves, etc. Automated tools (e.g. SOFAST, see Bonte et al. 2012) are already operational and are used daily in the frame of space weather services such as the ESA's Space Weather Coordination Centre (SSCC). These tools should be soon enriched with new capabilities. Title: Detection of EUV/Soft X-ray bremsstrahlung emission at terrestrial altitudes above 750 km Authors: Katsiyannis, A.; Dominique, M.; De Keyser, J.; Berghmans, D.; Michel, K.; Dammasch, I. E.; Borremans, K.; De Donder, E.; Ben Moussa, A. Bibcode: 2015AGUFMSM41F2560K Altcode: LYRA is a fast radiometer on-board the PROBA-2 mission designed to observe the solar activity from UV to Soft X-rays and consists of three redundant units of four different optical bandpasses each. Since the start of operation in 2010, LYRA regularly observes disturbances with a characteristic signature that have no direct solar origin. Instead the frequency of occurrence correlates with the ApA_p index of geomagnetic activity on Earth's surface and the location of these detections coincides with the McIlwain L ≈ 3 zon. By comparing the wavelength sensitivity of the main PROBA-2 instruments, the wavelength range of the detected photons can be narrowed down to the range of 0.07-1 KeV (1-17 nm) and the altitudes of their source to those above PROBA-2's orbit (~750 km). A discussion on the magnetospheric origins of this emission is included. Title: The extreme UV imager telescope on-board the Solar Orbiter mission: overview of phase C and D Authors: Halain, J. -P.; Rochus, P.; Renotte, E.; Hermans, A.; Jacques, L.; Auchère, F.; Berghmans, D.; Harra, L.; Schühle, U.; Schmutz, W.; Zhukov, A.; Aznar Cuadrado, R.; Delmotte, F.; Dumesnil, C.; Gyo, M.; Kennedy, T.; Smith, P.; Tandy, J.; Mercier, R.; Verbeeck, C. Bibcode: 2015SPIE.9604E..0GH Altcode: The Solar Orbiter mission is composed of ten scientific instruments dedicated to the observation of the Sun's atmosphere and its heliosphere, taking advantage of an out-of ecliptic orbit and at perihelion reaching a proximity close to 0.28 A.U. On board Solar Orbiter, the Extreme Ultraviolet Imager (EUI) will provide full-Sun image sequences of the solar corona in the extreme ultraviolet (17.1 nm and 30.4 nm), and high-resolution image sequences of the solar disk in the extreme ultraviolet (17.1 nm) and in the vacuum ultraviolet (121.6 nm). The EUI concept uses heritage from previous similar extreme ultraviolet instrument. Additional constraints from the specific orbit (thermal and radiation environment, limited telemetry download) however required dedicated technologies to achieve the scientific objectives of the mission. The development phase C of the instrument and its sub-systems has been successfully completed, including thermomechanical and electrical design validations with the Structural Thermal Model (STM) and the Engineering Model (EM). The instrument STM and EM units have been integrated on the respective spacecraft models and will undergo the system level tests. In parallel, the Phase D has been started with the sub-system qualifications and the flight parts manufacturing. The next steps of the EUI development will be the instrument Qualification Model (QM) integration and qualification tests. The Flight Model (FM) instrument activities will then follow with the acceptance tests and calibration campaigns. Title: PROBA2/SWAP EUV images of the large-scale EUV corona up to 3 solar radii: Can we close the gap in coronal magnetic field structure between 1.3 and 2.5 solar radii? Authors: De Groof, Anik; Seaton, Daniel B.; Rachmeler, Laurel; Berghmans, David Bibcode: 2015TESS....140901D Altcode: The EUV telescope PROBA2/SWAP has been observing the solar corona in a bandpass near 17.4 nm since February 2010. SWAP's wide field-of-view provides a unique and continuous view of the extended EUV corona up to 2-3 solar radii. By carefully processing and combining multiple SWAP images, low-noise composites were produced that reveal large-scale, EUV-emitting, coronal structures. These extended structures appear mainly above or at the edges of active regions and typically curve towards the poles. As they persist for multiple Carrington rotations and cannot easily be related to white-light features, they give an interesting view on how the coronal magnetic field is structured between 1.3 and 2-3 solar radii, in the gap between SDO/AIA’s FOV and typical lower boundaries of coronagraph FOVs. With the help of magnetic field models, we analyse the geometry of the extended EUV structures in more detail and compare with sporadic EUV coronagraph measurements up to as close as 1.5Rs. The opportunities that Solar Orbiter’s future observations will bring are explored. Title: 3D Visualization of Solar Data: Preparing for Solar Orbiter and Solar Probe Plus Authors: Mueller, D.; Felix, S.; Meier, S.; Csillaghy, A.; Nicula, B.; Verstringe, F.; Bourgoignie, B.; Berghmans, D.; Jiggens, P. Bibcode: 2014AGUFMSH21B4098M Altcode: The next generation of ESA/NASA heliophysics missions, Solar Orbiter and Solar Probe Plus, will focus on exploring the linkage between the Sun and the heliosphere. These new missions will collect unique data that will allow us to study, e.g., the coupling between macroscopic physical processes to those on kinetic scales, the generation of solar energetic particles and their propagation into the heliosphere and the origin and acceleration of solar wind plasma. Since 2010, NASA's Solar Dynamics Observatory returns 1.4 TB/day of high-resolution solar images, magnetograms and EUV irradiance data. Within a few years, the scientific community will thus have access to petabytes of multi­dimensional remote­sensing and complex in-situ observations from different vantage points, complemented by petabytes of simulation data. Answering overarching science questions like "How do solar transients drive heliospheric variability and space weather?" will only be possible if the community has the necessary tools at hand. As of today, there is an obvious lack of capability to both visualize these data and assimilate them into sophisticated models to advance our knowledge. A key piece needed to bridge the gap between observables, derived quantities like magnetic field extrapolations and model output is a tool to routinely and intuitively visualize large heterogeneous, multidimensional, time­dependent data sets. As of today, the space science community is lacking the means to do this (i) on a routine basis, (ii) for complex multi­dimensional data sets from various instruments and vantage points and (iii) in an extensible and modular way that is open for future improvements and interdisciplinary usage. In this contribution, we will present recent progress in visualizing the Sun and its magnetic field in 3D using the open-source JHelioviewer framework, which is part of the ESA/NASA Helioviewer Project. Among other features, JHelioviewer offers efficient region-of-interest-based data streaming, metadata and event catalog integration, as well as an interface to access science-quality data. In addition to its usage by the solar physics community, JHelioviewer has already been successfully adapted for application in planetary sciences and medical imaging. Title: Observational Characteristics of Coronal Mass Ejections without Low-coronal Signatures Authors: D'Huys, E.; Seaton, D. B.; Poedts, S.; Berghmans, D. Bibcode: 2014ApJ...795...49D Altcode: 2014arXiv1409.1422D Solar eruptions are usually associated with a variety of phenomena occurring in the low corona before, during, and after the onset of eruption. Though easily visible in coronagraph observations, so-called stealth coronal mass ejections (CMEs) do not obviously exhibit any of these low-coronal signatures. The presence or absence of distinct low-coronal signatures can be linked to different theoretical models to establish the mechanisms by which the eruption is initiated and driven. In this study, 40 CMEs without low-coronal signatures occurring in 2012 are identified. Their observational and kinematic properties are analyzed and compared to those of regular CMEs. Solar eruptions without clear on-disk or low-coronal signatures can lead to unexpected space weather impacts, since many early warning signs for significant space weather activity are not present in these events. A better understanding of their initiation mechanism(s) will considerably improve the ability to predict such space weather events. Title: The extreme UV imager of solar orbiter: from detailed design to flight model Authors: Halain, J. -P.; Rochus, P.; Renotte, E.; Auchère, F.; Berghmans, D.; Harra, L.; Schühle, U.; Schmutz, W.; Zhukov, A.; Aznar Cuadrado, R.; Delmotte, F.; Dumesnil, C.; Gyo, M.; Kennedy, T.; Mercier, R.; Verbeeck, F.; Thome, M.; Heerlein, K.; Hermans, A.; Jacques, L.; Mazzoli, A.; Meining, S.; Rossi, L.; Tandy, J.; Smith, P.; Winter, B. Bibcode: 2014SPIE.9144E..08H Altcode: The Extreme Ultraviolet Imager (EUI) on-board the Solar Orbiter mission will provide full-sun and high-resolution image sequences of the solar atmosphere at selected spectral emission lines in the extreme and vacuum ultraviolet. After the breadboarding and prototyping activities that focused on key technologies, the EUI project has completed the design phase and has started the final manufacturing of the instrument and its validation. The EUI instrument has successfully passed its Critical Design Review (CDR). The process validated the detailed design of the Optical Bench unit and of its sub-units (entrance baffles, doors, mirrors, camera, and filter wheel mechanisms), and of the Electronic Box unit. In the same timeframe, the Structural and Thermal Model (STM) test campaign of the two units have been achieved, and allowed to correlate the associated mathematical models. The lessons learned from STM and the detailed design served as input to release the manufacturing of the Qualification Model (QM) and of the Flight Model (FM). The QM will serve to qualify the instrument units and sub-units, in advance of the FM acceptance tests and final on-ground calibration. Title: Validation of the Earth atmosphere models using the EUV solar occultation data from the CORONAS and PROBA 2 instruments Authors: Slemzin, Vladimir; Kuzin, Sergey; Berghmans, David; Pertsov, Andrey; Dominique, Marie; Ulyanov, Artyom; Gaikovich, Konstantin Bibcode: 2014cosp...40E3125S Altcode: Absorption in the atmosphere below 500 km results in attenuation of the solar EUV flux, variation of its spectra and distortion of solar images acquired by solar EUV instruments operating on LEO satellites even on solar synchronous orbits. Occultation measurements are important for planning of solar observations from these satellites, and can be used for monitoring the upper atmosphere as well as for studying its response to the solar activity. We present the results of the occultation measurements of the solar EUV radiation obtained by the CORONAS-F/SPIRIT telescope at high solar activity (2002), by the CORONAS-Photon/TESIS telescope at low activity (2009), and by the SWAP telescope and LYRA radiometer onboard the PROBA 2 satellite at moderate activity (2010). The measured attenuation profiles and the retrieved linear extinction coefficients at the heights 200-500 km are compared with simulations by the NRLMSIS-00 and DTM2013 atmospheric models. It was shown that the results of simulations by the DTM2013 model are well agreed with the data of measurements at all stages of solar activity and in presence of the geomagnetic storm, whereas the results of the NRLMSISE-00 model significantly diverge from the measurements, in particular, at high and low activity. The research leading to these results has received funding from the European Union’s Seventh Programme for Research, Technological Development and Demonstration under Grant Agreement “eHeroes” (project No.284461, www.eheroes.eu). Title: The SWAP EUV imager onboard PROBA2: 3 years of observations Authors: West, Matthew; Berghmans, David; Seaton, Daniel Bibcode: 2014cosp...40E3622W Altcode: The Sun Watcher with Active Pixels and Image Processing (SWAP) imager is an EUV solar telescope on board ESA's Project for Onboard Autonomy 2 (PROBA2) mission launched on 2 November 2009. SWAP has a spectral bandpass centered on 17.4 nm and provides images of the low solar corona over a 54x54 arcmin field-of-view with 3.2 arcsec pixels and an imaging cadence of about two minutes. SWAP is designed to monitor all space-weather-relevant events and features in the low solar corona. The SWAP telescope is designed with various innovative technologies, including an off-axis optical design and a CMOS-APS detector. I will present what has been learnt from 3 years of SWAP operations, the advantages of the CMOS detector and SWAPs setup, and a few unique PROBA2/SWAP observations. Title: The EUI Data Center at the Royal Observatory of Belgium: challenges and solutions Authors: Verbeeck, Cis; Stegen, Koen; Berghmans, David; West, Matthew; Kraaikamp, Emil; Gissot, Samuel; Giordanengo, Boris; Nicula, Bogdan Bibcode: 2014cosp...40E3498V Altcode: ESA’s Solar Orbiter mission is conceived to perform a close-up study of the Sun and the inner heliosphere. With a perihelion close at 0.29 AU and a maximum aphelion at about 0.85 AU, Solar Orbiter ventures closer to the Sun than any spacecraft before. Furthermore, about 3 years after launch, the spacecraft will begin an out-of-ecliptic phase, with inclinations gradually increasing up to 30 degrees. Solar Orbiter will be launched in 2017 and its nominal mission will last until 2024 (with the possibility of an extended mission until 2026). It will provide unique data and imagery of the Sun. The Extreme Ultraviolet Imager (EUI) suite onboard Solar Orbiter is composed of two High Resolution Imagers (HRI, one at Lyman-alpha and one at 174 Angstrom), and one dual band Full-Sun imager (FSI) working alternatively at the 174 and 304 Angstrom EUV passbands. The EUI Data Center (EDC), under PI supervision and located at the Royal Observatory of Belgium (Brussels), will be the single point of contact for instrument planning activities and for data deliveries to the Solar Orbiter archive at ESAC (Madrid), and is currently in its design phase. The EUI Data Center will be responsible for delivery to ESAC and the maintenance of the pipeline software that will process EUI data from telemetry packets to higher level data products. It will also ensure the delivery of these data products to the Solar Orbiter Data Archive, and maintain the instrument user manual that documents the processing of EUI non-science TM packets at ESOC (Darmstadt). The EDC will monitor any anomaly affecting the EUI instrument and produce on a regular basis the Instrument Operations Reports including an instrument health and science performance review. Here, we present an overview of the EDC and how it envisages to tackle some specific challenges. Since EUI will only observe during three “science windows” of 10 days each per orbit of about 165 days and in view of a severely limited telemetry, it is important to implement observing strategies that maximize the science return on the targets: active regions, coronal hole boundaries, quiet Sun, and flares. In order to allow scientists to select a proper target region on the Sun, precursor observations will be downlinked with low latency before the start of the science windows. The spacecraft can then be pointed towards the selected region such that high resolution instruments such as HRI contain this region within their field of view. Given the limited telemetry and delayed ground contacts, it is especially hard to decide when to observe and store high-cadence data in order to catch a large flare. To address this challenge, the EUI consortium has developed a dedicated automatic onboard trigger that detects large flares. Title: SWAP Observations of the Long-term, Large-scale Evolution of the Extreme-ultraviolet Solar Corona Authors: Seaton, Daniel B.; De Groof, Anik; Shearer, Paul; Berghmans, David; Nicula, Bogdan Bibcode: 2013ApJ...777...72S Altcode: 2013arXiv1309.1345S The Sun Watcher with Active Pixels and Image Processing (SWAP) EUV solar telescope on board the Project for On-Board Autonomy 2 spacecraft has been regularly observing the solar corona in a bandpass near 17.4 nm since 2010 February. With a field of view of 54 × 54 arcmin, SWAP provides the widest-field images of the EUV corona available from the perspective of the Earth. By carefully processing and combining multiple SWAP images, it is possible to produce low-noise composites that reveal the structure of the EUV corona to relatively large heights. A particularly important step in this processing was to remove instrumental stray light from the images by determining and deconvolving SWAP's point-spread function from the observations. In this paper, we use the resulting images to conduct the first-ever study of the evolution of the large-scale structure of the corona observed in the EUV over a three year period that includes the complete rise phase of solar cycle 24. Of particular note is the persistence over many solar rotations of bright, diffuse features composed of open magnetic fields that overlie polar crown filaments and extend to large heights above the solar surface. These features appear to be related to coronal fans, which have previously been observed in white-light coronagraph images and, at low heights, in the EUV. We also discuss the evolution of the corona at different heights above the solar surface and the evolution of the corona over the course of the solar cycle by hemisphere. Title: On-Orbit Degradation of Solar Instruments Authors: BenMoussa, A.; Gissot, S.; Schühle, U.; Del Zanna, G.; Auchère, F.; Mekaoui, S.; Jones, A. R.; Walton, D.; Eyles, C. J.; Thuillier, G.; Seaton, D.; Dammasch, I. E.; Cessateur, G.; Meftah, M.; Andretta, V.; Berghmans, D.; Bewsher, D.; Bolsée, D.; Bradley, L.; Brown, D. S.; Chamberlin, P. C.; Dewitte, S.; Didkovsky, L. V.; Dominique, M.; Eparvier, F. G.; Foujols, T.; Gillotay, D.; Giordanengo, B.; Halain, J. P.; Hock, R. A.; Irbah, A.; Jeppesen, C.; Judge, D. L.; Kretzschmar, M.; McMullin, D. R.; Nicula, B.; Schmutz, W.; Ucker, G.; Wieman, S.; Woodraska, D.; Woods, T. N. Bibcode: 2013SoPh..288..389B Altcode: 2013arXiv1304.5488B We present the lessons learned about the degradation observed in several space solar missions, based on contributions at the Workshop about On-Orbit Degradation of Solar and Space Weather Instruments that took place at the Solar Terrestrial Centre of Excellence (Royal Observatory of Belgium) in Brussels on 3 May 2012. The aim of this workshop was to open discussions related to the degradation observed in Sun-observing instruments exposed to the effects of the space environment. This article summarizes the various lessons learned and offers recommendations to reduce or correct expected degradation with the goal of increasing the useful lifespan of future and ongoing space missions. Title: The SWAP EUV Imaging Telescope Part I: Instrument Overview and Pre-Flight Testing Authors: Seaton, D. B.; Berghmans, D.; Nicula, B.; Halain, J. -P.; De Groof, A.; Thibert, T.; Bloomfield, D. S.; Raftery, C. L.; Gallagher, P. T.; Auchère, F.; Defise, J. -M.; D'Huys, E.; Lecat, J. -H.; Mazy, E.; Rochus, P.; Rossi, L.; Schühle, U.; Slemzin, V.; Yalim, M. S.; Zender, J. Bibcode: 2013SoPh..286...43S Altcode: 2012SoPh..tmp..217S; 2012arXiv1208.4631S The Sun Watcher with Active Pixels and Image Processing (SWAP) is an EUV solar telescope onboard ESA's Project for Onboard Autonomy 2 (PROBA2) mission launched on 2 November 2009. SWAP has a spectral bandpass centered on 17.4 nm and provides images of the low solar corona over a 54×54 arcmin field-of-view with 3.2 arcsec pixels and an imaging cadence of about two minutes. SWAP is designed to monitor all space-weather-relevant events and features in the low solar corona. Given the limited resources of the PROBA2 microsatellite, the SWAP telescope is designed with various innovative technologies, including an off-axis optical design and a CMOS-APS detector. This article provides reference documentation for users of the SWAP image data. Title: Preface Authors: Berghmans, D.; De Groof, A.; Dominique, M.; Hochedez, J. -F.; Leibacher, J. W. Bibcode: 2013SoPh..286....1B Altcode: No abstract at ADS Title: SoFAST: Automated Flare Detection with the PROBA2/SWAP EUV Imager Authors: Bonte, K.; Berghmans, D.; De Groof, A.; Steed, K.; Poedts, S. Bibcode: 2013SoPh..286..185B Altcode: 2012SoPh..tmp..288B The Sun Watcher with Active Pixels and Image Processing (SWAP) EUV imager onboard PROBA2 provides a non-stop stream of coronal extreme-ultraviolet (EUV) images at a cadence of typically 130 seconds. These images show the solar drivers of space-weather, such as flares and erupting filaments. We have developed a software tool that automatically processes the images and localises and identifies flares. On one hand, the output of this software tool is intended as a service to the Space Weather Segment of ESA's Space Situational Awareness (SSA) program. On the other hand, we consider the PROBA2/SWAP images as a model for the data from the Extreme Ultraviolet Imager (EUI) instrument prepared for the future Solar Orbiter mission, where onboard intelligence is required for prioritising data within the challenging telemetry quota. In this article we present the concept of the software, the first statistics on its effectiveness and the online display in real time of its results. Our results indicate that it is not only possible to detect EUV flares automatically in an acquired dataset, but that quantifying a range of EUV dynamics is also possible. The method is based on thresholding of macropixelled image sequences. The robustness and simplicity of the algorithm is a clear advantage for future onboard use. Title: The SWAP EUV Imaging Telescope. Part II: In-flight Performance and Calibration Authors: Halain, J. -P.; Berghmans, D.; Seaton, D. B.; Nicula, B.; De Groof, A.; Mierla, M.; Mazzoli, A.; Defise, J. -M.; Rochus, P. Bibcode: 2013SoPh..286...67H Altcode: 2012SoPh..tmp..317H; 2012arXiv1210.3551H The Sun Watcher with Active Pixel System detector and Image Processing (SWAP) telescope was launched on 2 November 2009 onboard the ESA PROBA2 technological mission and has acquired images of the solar corona every one to two minutes for more than two years. The most important technological developments included in SWAP are a radiation-resistant CMOS-APS detector and a novel onboard data-prioritization scheme. Although such detectors have been used previously in space, they have never been used for long-term scientific observations on orbit. Thus SWAP requires a careful calibration to guarantee the science return of the instrument. Since launch we have regularly monitored the evolution of SWAP's detector response in-flight to characterize both its performance and degradation over the course of the mission. These measurements are also used to reduce detector noise in calibrated images (by subtracting dark-current). Because accurate measurements of detector dark-current require large telescope off-points, we also monitored straylight levels in the instrument to ensure that these calibration measurements are not contaminated by residual signal from the Sun. Here we present the results of these tests and examine the variation of instrumental response and noise as a function of both time and temperature throughout the mission. Title: The Projects for Onboard Autonomy (PROBA2) Science Centre: Sun Watcher Using APS Detectors and Image Processing (SWAP) and Large-Yield Radiometer (LYRA) Science Operations and Data Products Authors: Zender, J.; Berghmans, D.; Bloomfield, D. S.; Cabanas Parada, C.; Dammasch, I.; De Groof, A.; D'Huys, E.; Dominique, M.; Gallagher, P.; Giordanengo, B.; Higgins, P. A.; Hochedez, J. -F.; Yalim, M. S.; Nicula, B.; Pylyser, E.; Sanchez-Duarte, L.; Schwehm, G.; Seaton, D. B.; Stanger, A.; Stegen, K.; Willems, S. Bibcode: 2013SoPh..286...93Z Altcode: 2012SoPh..tmp..142Z The PROBA2 Science Centre (P2SC) is a small-scale science operations centre supporting the Sun observation instruments onboard PROBA2: the EUV imager Sun Watcher using APS detectors and image Processing (SWAP) and Large-Yield Radiometer (LYRA). PROBA2 is one of ESA's small, low-cost Projects for Onboard Autonomy (PROBA) and part of ESA's In-Orbit Technology Demonstration Programme. The P2SC is hosted at the Royal Observatory of Belgium, co-located with both Principal Investigator teams. The P2SC tasks cover science planning, instrument commanding, instrument monitoring, data processing, support of outreach activities, and distribution of science data products. PROBA missions aim for a high degree of autonomy at mission and system level, including the science operations centre. The autonomy and flexibility of the P2SC is reached by a set of web-based interfaces allowing the operators as well as the instrument teams to monitor quasi-continuously the status of the operations, allowing a quick reaction to solar events. In addition, several new concepts are implemented at instrument, spacecraft, and ground-segment levels allowing a high degree of flexibility in the operations of the instruments. This article explains the key concepts of the P2SC, emphasising the automation and the flexibility achieved in the commanding as well as the data-processing chain. Title: Temperature Response of the 171 Å Passband of the SWAP Imager on PROBA2, with a Comparison to TRACE, SOHO, STEREO, and SDO Authors: Raftery, Claire L.; Bloomfield, D. Shaun; Gallagher, Peter T.; Seaton, Daniel B.; Berghmans, David; De Groof, Anik Bibcode: 2013SoPh..286..111R Altcode: We calculated the temperature response of the 171 Å passbands of the Sun Watcher using APS detectors and image Processing (SWAP) instrument onboard the PRoject for OnBoard Autonomy 2 (PROBA2) satellite. These results were compared to the temperature responses of the Extreme Ultraviolet Imaging Telescope (EIT) onboard the Solar and Heliospheric Observatory (SOHO), the Transition Region and Coronal Explorer (TRACE), the twin Extreme Ultraviolet Imagers (EUVI) onboard the Solar TErrestrial RElations Observatory (STEREO) A and B spacecraft, and the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). Multiplying the wavelength-response functions for each instrument by a series of isothermal synthetic spectra and integrating over the range 165 - 195 Å produced temperature-response functions for the six instruments. Each temperature response was then multiplied by sample differential emission-measure functions for four different solar conditions. For any given plasma condition (e.g. quiet Sun, active region), it was found that the overall variation with temperature agreed remarkably well across the six instruments, although the wavelength responses for each instrument have some distinctly different features. Deviations were observed, however, when we compared the response of any one instrument to different solar conditions, particularly for the case of solar flares. Title: Signatures of Slow Solar Wind Streams from Active Regions in the Inner Corona Authors: Slemzin, V.; Harra, L.; Urnov, A.; Kuzin, S.; Goryaev, F.; Berghmans, D. Bibcode: 2013SoPh..286..157S Altcode: 2012arXiv1203.6756S; 2012SoPh..tmp..144S The identification of solar-wind sources is an important question in solar physics. The existing solar-wind models (e.g., the Wang-Sheeley-Arge model) provide the approximate locations of the solar wind sources based on magnetic field extrapolations. It has been suggested recently that plasma outflows observed at the edges of active regions may be a source of the slow solar wind. To explore this we analyze an isolated active region (AR) adjacent to small coronal hole (CH) in July/August 2009. On 1 August, Hinode/EUV Imaging Spectrometer observations showed two compact outflow regions in the corona. Coronal rays were observed above the active-region coronal hole (ARCH) region on the eastern limb on 31 July by STEREO-A/EUVI and at the western limb on 7 August by CORONAS-Photon/TESIS telescopes. In both cases the coronal rays were co-aligned with open magnetic-field lines given by the potential field source surface model, which expanded into the streamer. The solar-wind parameters measured by STEREO-B, ACE, Wind, and STEREO-A confirmed the identification of the ARCH as a source region of the slow solar wind. The results of the study support the suggestion that coronal rays can represent signatures of outflows from ARs propagating in the inner corona along open field lines into the heliosphere. Title: Study of a Prominence Eruption using PROBA2/SWAP and STEREO/EUVI Data Authors: Mierla, M.; Seaton, D. B.; Berghmans, D.; Chifu, I.; De Groof, A.; Inhester, B.; Rodriguez, L.; Stenborg, G.; Zhukov, A. N. Bibcode: 2013SoPh..286..241M Altcode: 2012SoPh..tmp...66M; 2012arXiv1203.6732M Observations of the early rise and propagation phases of solar eruptive prominences can provide clues about the forces acting on them through the behavior of their acceleration with height. We have analyzed such an event, observed on 13 April 2010 by SWAP on PROBA2 and EUVI on STEREO. A feature at the top of the erupting prominence was identified and tracked in images from the three spacecraft. The triangulation technique was used to derive the true direction of propagation of this feature. The reconstructed points were fitted with two mathematical models: i) a power-law polynomial function and ii) a cubic smoothing spline, in order to derive the accelerations. The first model is characterized by five degrees of freedom while the second one is characterized by ten degrees of freedom. The results show that the acceleration increases smoothly, and it is continuously increasing with height. We conclude that the prominence is not accelerated immediately by local reconnection, but rather is swept away as part of a large-scale relaxation of the coronal magnetic field. Title: Solar TErrestrial Relations Observatory-A (STEREO-A) and PRoject for On-Board Autonomy 2 (PROBA2) Quadrature Observations of Reflections of Three EUV Waves from a Coronal Hole Authors: Kienreich, I. W.; Muhr, N.; Veronig, A. M.; Berghmans, D.; De Groof, A.; Temmer, M.; Vršnak, B.; Seaton, D. B. Bibcode: 2013SoPh..286..201K Altcode: 2012SoPh..tmp..138K We investigate the interaction of three consecutive large-scale coronal waves with a polar coronal hole, simultaneously observed on-disk by the Solar TErrestrial Relations Observatory (STEREO)-A spacecraft and on the limb by the PRoject for On-Board Autonomy 2 (PROBA2) spacecraft on 27 January 2011. All three extreme ultraviolet (EUV) waves originate from the same active region, NOAA 11149, positioned at N30E15 in the STEREO-A field of view and on the limb in PROBA2. For the three primary EUV waves, we derive starting velocities in the range of ≈ 310 km s−1 for the weakest up to ≈ 500 km s−1 for the strongest event. Each large-scale wave is reflected at the border of the extended coronal hole at the southern polar region. The average velocities of the reflected waves are found to be smaller than the mean velocities of their associated direct waves. However, the kinematical study also reveals that in each case the ending velocity of the primary wave matches the initial velocity of the reflected wave. In all three events, the primary and reflected waves obey the Huygens-Fresnel principle, as the incident angle with ≈ 10° to the normal is of the same magnitude as the angle of reflection. The correlation between the speed and the strength of the primary EUV waves, the homologous appearance of both the primary and the reflected waves, and in particular the EUV wave reflections themselves suggest that the observed EUV transients are indeed nonlinear large-amplitude MHD waves. Title: Space Weather and Particle Effects on the Orbital Environment of PROBA2 Authors: West, Matthew; Seaton, Dan; Dominique, Marie; Berghmans, David; Nicula, Bogdan; Pylyser, Erik; Stegen, Koen; De Keyser, Johan Bibcode: 2013EGUGA..1510865W Altcode: Data from the EUV imager SWAP and UV/EUV radiometer LYRA on board the PROBA2 spacecraft are regularly affected by space weather conditions along the spacecraft's orbital path. While these effects are generally removed from calibrated data intended for scientific analysis, they provide an interesting opportunity to characterize the evolution near-Earth space environment as the result of changing space weather conditions. Here we present an analysis of these space weather effects on PROBA2 observations and some conclusions about both the long-term evolution of the inner magnetosphere and short-term events driven by the active sun. Title: Quasi-Periodic Pulsations during the onset of solar flares: multi-instrumental comparison Authors: West, M. J.; Dolla, L.; Marque, C.; Seaton, D. B.; Van Doorsselaere, T.; Dominique, M.; Berghmans, D.; Cabanas, C.; De Groof, A.; Schmutz, W.; Verdini, A.; Zender, J.; Zhukov, A. N. Bibcode: 2013enss.confE..82W Altcode: Quasi-periodic pulsations have been observed in the rising phase of solar flares for many years. Observations have been made over a wide spectral range, extending from X-rays to radio wavelengths. The current generation of spacebourne instruments, especially SDO, EVE and ESP, have exceptionally high sampling rates and allow us to make more detailed observations of this phenomena. In this work, we compare short-period oscillations (around 10 s) observed in flare events by multiple instruments: the radiometer channels of SDO/EVE-ESP (soft X-ray, coronal and chromospheric passbands), the EUV channels of the radiometer PROBA2/LYRA, the RHESSI passbands and short-wavelength radio observations. Title: The EUI instrument on board the Solar Orbiter mission: from breadboard and prototypes to instrument model validation Authors: Halain, J. -P.; Rochus, P.; Renotte, E.; Appourchaux, T.; Berghmans, D.; Harra, L.; Schühle, U.; Schmutz, W.; Auchère, F.; Zhukov, A.; Dumesnil, C.; Delmotte, F.; Kennedy, T.; Mercier, R.; Pfiffner, D.; Rossi, L.; Tandy, J.; BenMoussa, A.; Smith, P. Bibcode: 2012SPIE.8443E..07H Altcode: The Solar Orbiter mission will explore the connection between the Sun and its heliosphere, taking advantage of an orbit approaching the Sun at 0.28 AU. As part of this mission, the Extreme Ultraviolet Imager (EUI) will provide full-sun and high-resolution image sequences of the solar atmosphere at selected spectral emission lines in the extreme and vacuum ultraviolet. To achieve the required scientific performances under the challenging constraints of the Solar Orbiter mission it was required to further develop existing technologies. As part of this development, and of its maturation of technology readiness, a set of breadboard and prototypes of critical subsystems have thus been realized to improve the overall instrument design. The EUI instrument architecture, its major components and sub-systems are described with their driving constraints and the expected performances based on the breadboard and prototype results. The instrument verification and qualification plan will also be discussed. We present the thermal and mechanical model validation, the instrument test campaign with the structural-thermal model (STM), followed by the other instrument models in advance of the flight instrument manufacturing and AIT campaign. Title: Plasmoid Ejection at a Solar Total Eclipse Authors: Koutchmy, S.; Bazin, C.; Berghmans, D.; De Groof, A.; Druckmüller, M.; Tavabi, E.; Engell, A.; Filippov, B.; Golub, L.; Lamy, Ph.; Linker, J.; Mikic, Z.; Mouette, J.; Nitschelm, Ch.; Seaton, D.; Slemzin, V. Bibcode: 2012EAS....55..223K Altcode: The existence of coronal plasmoids has been postulated for many years in order to supply material to streamers and possibly to the solar wind (SW). The W-L SoHO C2 Lasco coronagraph observations were made under the 2.2 solar radii (R0) occulting disk to look at the ultimate sources of the SW; EUV imagers are preferably devoted to the analysis of the corona on and very near the solar disk. Here, in addition to eclipse white-light (W-L) snapshots, we used the new SWAP space-borne imager designed for the systematic survey of coronal activity in the EUV lines near 17.4 nm, over a field of view (FOV) up to 2 R0. Using summed and co-aligned images, the corona can then be evaluated for the 1st time up to the limit of this FOV. At the time of the July 11, 2010, solar total eclipse a 20h continuous run of observations was collected, including images taken during eclipse totality from several ground observing locations where W-L data were collected. A plasmoid-like off-limb event was followed using the SWAP summed Title: A Collaborative Research Environment for Heliophysics Authors: Bentley, R. D.; Berghmans, D.; Csillaghy, A. Bibcode: 2012EGUGA..1412873B Altcode: Heliophysics is the study of the effect of the Sun on the Solar System; it is a relatively new science that combines the solar, heliospheric, geophysics and planetary communities. The subject is an example of the increasing desire to address science problems that span disciplinary boundaries and provides a good example of the issues involved. The communities that constitute heliophysics have grown up independently and there are differences in the way that their data are stored and used. Although a number of capabilities relevant to heliophysics have been established under auspices of various projects and organisations, the fact that they have not followed any underlying strategy is now inhibiting our ability to do this type of science. The Heliophysics Integrated Observatory (HELIO), a research infrastructure funded under Capacities programme of the EC's 7th Framework Programme (FP7), was designed around a service-oriented architecture with needed capabilities that support metadata curation and search, data location and retrieval, and data processing and storage being established as independent services. In addition, a number of virtual observatories have been established that address aspects of the overall problem of heliophysics within the NASA's Heliophysics Science Division. We examine the capabilities of these resources and look at where their strengths and weaknesses lie. We identify some of the steps that are needed to improve interoperability between the initiatives and consider how they could be brought together to form a Collaborative Research Environment for Heliophysics (CREH). The Coordination Action for the integration of Solar System Infrastructure and Science (CASSIS) has the objective of exploring ways to improve interoperability for all aspects of Solar System Science. CASSIS is funded under Capacities specific programme of the European Commission's Seventh Framework Programme (FP7) and grew out of the HELIO, Europlanet RI and SOTERIA projects; it also includes other key partners such as NASA, ESA, and NOAA. We welcome participation by other interested organisations Title: STEREO-A and PROBA2 Quadrature Observations of Reflections of three EUV Waves from a Coronal Hole Authors: Kienreich, Ines Waltraud; Muhr, Nicole; Veronig, Astrid; Berghmans, David; de Groof, Anik; Temmer, Manuela; Vršnak, Bojan; Seaton, Dan Bibcode: 2012arXiv1204.6472K Altcode: 2012arXiv1204.6472W We investigate the interaction of three consecutive large-scale coronal waves with a polar coronal hole, simultaneously observed on-disk by the Solar TErrestrial Relations Observatory (STEREO)-A spacecraft and on the limb by the PRoject for On-Board Autonomy 2 (PROBA2) spacecraft on January 27, 2011. All three extreme-ultraviolet(EUV) waves originate from the same active region NOAA 11149 positioned at N30E15 in the STEREO-A field-of-view and on the limb in PROBA2. We derive for the three primary EUV waves start velocities in the range of ~310 km/s for the weakest up to ~500 km/s for the strongest event. Each large-scale wave is reflected at the border of the extended coronal hole at the southern polar region. The average velocities of the reflected waves are found to be smaller than the mean velocities of their associated direct waves. However, the kinematical study also reveals that in each case the end velocity of the primary wave matches the initial velocity of the reflected wave. In all three events the primary and reflected waves obey the Huygens-Fresnel principle, as the incident angle with ~10° to the normal is of the same size as the angle of reflection. The correlation between the speed and the strength of the primary EUV waves, the homologous appearance of both the primary and the reflected waves, and in particular the EUV wave reflections themselves implicate that the observed EUV transients are indeed nonlinear large-amplitude MHD waves. Title: Time Delays in Quasi-periodic Pulsations Observed during the X2.2 Solar Flare on 2011 February 15 Authors: Dolla, L.; Marqué, C.; Seaton, D. B.; Van Doorsselaere, T.; Dominique, M.; Berghmans, D.; Cabanas, C.; De Groof, A.; Schmutz, W.; Verdini, A.; West, M. J.; Zender, J.; Zhukov, A. N. Bibcode: 2012ApJ...749L..16D Altcode: 2012arXiv1203.6223D We report observations of quasi-periodic pulsations (QPPs) during the X2.2 flare of 2011 February 15, observed simultaneously in several wavebands. We focus on fluctuations on timescale 1-30 s and find different time lags between different wavebands. During the impulsive phase, the Reuven Ramaty High Energy Solar Spectroscopic Imager channels in the range 25-100 keV lead all the other channels. They are followed by the Nobeyama RadioPolarimeters at 9 and 17 GHz and the extreme-ultraviolet (EUV) channels of the Euv SpectroPhotometer (ESP) on board the Solar Dynamic Observatory. The zirconium and aluminum filter channels of the Large Yield Radiometer on board the Project for On-Board Autonomy satellite and the soft X-ray (SXR) channel of ESP follow. The largest lags occur in observations from the Geostationary Operational Environmental Satellite, where the channel at 1-8 Å leads the 0.5-4 Å channel by several seconds. The time lags between the first and last channels is up to ≈9 s. We identified at least two distinct time intervals during the flare impulsive phase, during which the QPPs were associated with two different sources in the Nobeyama RadioHeliograph at 17 GHz. The radio as well as the hard X-ray channels showed different lags during these two intervals. To our knowledge, this is the first time that time lags are reported between EUV and SXR fluctuations on these timescales. We discuss possible emission mechanisms and interpretations, including flare electron trapping. Title: Preliminary Results on Irradiance Measurements from Lyra and Swap Authors: Kumara, S. T.; Kariyappa, R.; Dominique, M.; Berghmans, D.; Damé, L.; Hochedez, J. F.; Doddamani, V. H.; Chitta, Lakshmi Pradeep Bibcode: 2012AdAst2012E...5K Altcode: 2012AdAst2012E..10K No abstract at ADS Title: Hierarchical approach to forecasting recurrent solar wind streams Authors: Shugay, Yu. S.; Veselovsky, I. S.; Seaton, D. B.; Berghmans, D. Bibcode: 2011SoSyR..45..546S Altcode: The hierarchical approach to predicting quasi-stationary, high-speed solar wind (SW) streams is described. This approach integrates various types of data into a single forecasting system by means of an ensemble of experts. The input data included the daily values of the coronal hole areas, which were calculated from the ultraviolet images of the Sun, and the speed of the SW streams during the previous solar rotations. The coronal hole areas were calculated from the images taken by the SWAP instrument aboard the PROBA2 satellite in the spectral interval centered at a wavelength of 17.4 nm and by the AIA instrument aboard the SDO spacecraft in the interval of wavelengths centered at 19.3 and 17.1 nm. The forecast was based on the data for 2010, corresponding to the rising phase of the 24th solar cycle. On the first hierarchical level, a few simple model estimates were obtained for the speed of the SW streams from the input data of each type. On the second level of hierarchy, the final 3 day ahead forecast of the SW velocity was formulated on the basis of the obtained estimates. The proposed hierarchical approach improves the accuracy of forecasting the SW velocity. In addition, in such a method of prediction, the data gaps in the records of one instrument do not crucially affect the final result of forecasting of the system as a whole. Title: LYRA and SWAP, the two Solar Instruments on-board PROBA2 Authors: Dominique, M.; Berghmans, D.; Schmutz, W. K.; Dammasch, I.; De Groof, A.; Halain, J.; Hochedez, J.; Kretzschmar, M.; Seaton, D. B. Bibcode: 2011AGUFMSH13B1949D Altcode: PROBA2 (http://proba2.sidc.be) is an ESA micro-satellite that was launched in November 2009. Two instruments on-board, SWAP and LYRA, are devoted to solar observations. SWAP (PI: D. Berghmans) is an EUV imager observing the corona with a bandpass centered on 174 Å at a cadence of 1-2 min. Its high contrast images, large FOV and flexible off-pointing capabilities make SWAP particularly well suited for the study of coronal eruptions. LYRA (PI: M. Dominique) is a UV-EUV radiometer observing in four spectral channels, chosen for their relevance in solar physics and aeronomy. Its very fast acquisition cadence (up to 100 Hz) allows scientists to perform detailed analysis of solar flares. We discuss the characteristics of both instruments, review their performance and evolution, and highlight their complementarity to other missions. We also present the data products that can be downloaded from the mission website and give an overview of the various investigations for which SWAP and LYRA data are currently used (CMEs, flares, solar variability, and many others). Title: LYRA Observations of Two Oscillation Modes in a Single Flare Authors: Van Doorsselaere, T.; De Groof, A.; Zender, J.; Berghmans, D.; Goossens, M. Bibcode: 2011ApJ...740...90V Altcode: We analyze light curves from the LYRA irradiance experiment on board PROBA2 during the flare of 2010 February 8. We see both long- and short-period oscillations during the flare. The long-period oscillation is interpreted in terms of standing slow sausage modes; the short-period oscillation is thought to be a standing fast sausage mode. The simultaneous presence of two oscillation modes in the same flaring structure allows for new coronal seismological applications. The periods are used to find seismological estimates of the plasma-β and the density contrast of the flaring loop. Also the wave mode number is estimated from the observed periods. Title: Validation of CME Detection Software (CACTus) by Means of Simulated Data, and Analysis of Projection Effects on CME Velocity Measurements Authors: Bonte, K.; Jacobs, C.; Robbrecht, E.; De Groof, A.; Berghmans, D.; Poedts, S. Bibcode: 2011SoPh..270..253B Altcode: 2011SoPh..tmp...52B; 2011SoPh..tmp...72B In the context of space weather forecasting, an automated detection of coronal mass ejections (CMEs) becomes more and more important for efficiently handling a large data flow which is expected from recently-launched and future solar missions. In this paper we validate the detection software package "CACTus" by applying the program to synthetic data from our 3D time-dependent CME simulations instead of observational data. The main strength of this study is that we know in advance what should be detected. We describe the sensitivities and strengths of automated detection, more specific for the CACTus program, resulting in a better understanding of CME detection on one hand and the calibration of the CACTus software on the other hand, suggesting possible improvements of the package. In addition, the simulation is an ideal tool to investigate projection effects on CME velocity measurements. Title: SWAP-SECCHI Observations of a Mass-loading Type Solar Eruption Authors: Seaton, Daniel B.; Mierla, Marilena; Berghmans, David; Zhukov, Andrei N.; Dolla, Laurent Bibcode: 2011ApJ...727L..10S Altcode: 2010arXiv1011.1144S We present a three-dimensional reconstruction of an eruption that occurred on 2010 April 3 using observations from SWAP on board PROBA2 and SECCHI on board STEREO. The event unfolded in two parts: an initial flow of cooler material confined to a height low in the corona, followed by a flux rope eruption higher in the corona. We conclude that mass off-loading from the first part triggered a rise and, subsequently, catastrophic loss of equilibrium of the flux rope. Title: SWAP: An EUV Imager for Solar Monitoring on Board of the PROBA2 Micro-Satellite Authors: Katsiyannis, A. C.; Berghmans, D.; Swap Consortium Bibcode: 2010ASPC..424..104K Altcode: PROBA2 is a ESA technology demonstration mission successfully launched in November 2nd 2009. The prime instrument on board of PROBA2 is SWAP (Sun Watcher using Active Pixel System detector and Image Processing), a full disk solar imager with a narrow bandpass filter centered at 17.4 nm (Fe IX - XI) and a fast cadence of ≍1 min. The telescope is an extreme ultraviolet (EUV), high cadence (of up to 1 frame per minute) imager based on an enchanted APS CMOS detector. The field of view will be wider than EIT’s by ≍20% allowing SWAP to observe a larger portion of the lower corona and bridge the gap between EIT and LASCO-C2. Title: The technical challenges of the Solar-Orbiter EUI instrument Authors: Halain, Jean-Philippe; Rochus, Pierre; Appourchaux, Thierry; Berghmans, David; Harra, Louise; Schühle, Udo; Auchère, Frédéric; Zhukov, Andrei; Renotte, Etienne; Defise, Jean-Marc; Rossi, Laurence; Fleury-Frenette, Karl; Jacques, Lionel; Hochedez, Jean-François; Ben Moussa, Ali Bibcode: 2010SPIE.7732E..0RH Altcode: 2010SPIE.7732E..20H The Extreme Ultraviolet Imager (EUI) onboard Solar Orbiter consists of a suite of two high-resolution imagers (HRI) and one dual-band full Sun imager (FSI) that will provide EUV and Lyman-α images of the solar atmospheric layers above the photosphere. The EUI instrument is based on a set of challenging new technologies allowing to reach the scientific objectives and to cope with the hard space environment of the Solar Orbiter mission. The mechanical concept of the EUI instrument is based on a common structure supporting the HRI and FSI channels, and a separated electronic box. A heat rejection baffle system is used to reduce the Sun heat load and provide a first protection level against the solar disk straylight. The spectral bands are selected by thin filters and multilayer mirror coatings. The detectors are 10μm pitch back illuminated CMOS Active Pixel Sensors (APS), best suited for the EUI science requirements and radiation hardness. This paper presents the EUI instrument concept and its major sub-systems. The current developments of the instrument technologies are also summarized. Title: First light of SWAP on-board PROBA2 Authors: Halain, Jean-Philippe; Berghmans, David; Defise, Jean-Marc; Renotte, Etienne; Thibert, Tanguy; Mazy, Emmanuel; Rochus, Pierre; Nicula, Bogdan; de Groof, Anik; Seaton, Dan; Schühle, Udo Bibcode: 2010SPIE.7732E..0PH Altcode: 2010SPIE.7732E..18H The SWAP telescope (Sun Watcher using Active Pixel System detector and Image Processing) is an instrument launched on 2nd November 2009 on-board the ESA PROBA2 technological mission. SWAP is a space weather sentinel from a low Earth orbit, providing images at 174 nm of the solar corona. The instrument concept has been adapted to the PROBA2 mini-satellite requirements (compactness, low power electronics and a-thermal opto-mechanical system). It also takes advantage of the platform pointing agility, on-board processor, Packetwire interface and autonomous operations. The key component of SWAP is a radiation resistant CMOS-APS detector combined with onboard compression and data prioritization. SWAP has been developed and qualified at the Centre Spatial de Liège (CSL) and calibrated at the PTBBessy facility. After launch, SWAP has provided its first images on 14th November 2009 and started its nominal, scientific phase in February 2010, after 3 months of platform and payload commissioning. This paper summarizes the latest SWAP developments and qualifications, and presents the first light results. Title: Space Weather data and services at SIDC / RWC Belgium Authors: van der Linden, Ronald; Ben Moussa, Ali; Berghmans, David; Boulvin, Olivier; Boyes, David; Cabanas Parada, Carlos; Callebaut, Benoit; Clette, Frédéric; Dammasch, Ingolf; Delouille, Veronique; D'Huys, Elke; Dolla, Laurent; Dominique, Marie; Dufond, Jean-Luc; Ergen, Aydin; Giordanengo, Boris; Gissot, Samuel; Goryaev, Farid; Hochedez, Jean-Francois; Lemaâtre, Olivier; Lisnichenko, Pavel; Magdalenic, Jas-Mina; Mampaey, Benjamin; Marque, Christophe; Nicula, Bogdan; Podladchikova, Elena; Pylyser, Erik; Raynal, Sophie; Rodriguez, Luciano; Seaton, Daniël; van der Linden, Ronald; Vandersyppe, Anne; Vanlommel, Petra; Vanraes, Stéphane; Verbeeck, Cis; Verdini, Andrea; Wauters, Laurence; West, Matthew; Willems, Sarah; Zhukov, Andrei Bibcode: 2010cosp...38.4202V Altcode: 2010cosp.meet.4202V The SIDC of the Royal Observatory of Belgium is a very active center for solar physics research, but also provides an operational service for data and services related to solar activity and space weather. In this poster we present the currently available data sets and products, with a focus on recent additions and new developments. Title: Solar observations from PROBA2: ready for space weather operations Authors: Berghmans, David; Hochedez, Jean-François Bibcode: 2010cosp...38.4184B Altcode: 2010cosp.meet.4184B The ESA micro satellite PROBA2 was launched on November 2, 2009. It carries two solar instruments, the radiometer LYRA and the coronal imager SWAP whose commissioning ended in March 2010. LYRA (PI: J.-F. Hochedez) observes the solar irradiance in 4 wavelengths chosen for their relevance to space weather, solar physics and Earth aeronomy. LYRA is able to follow the time evolution of solar flares at very high temporal resolution. SWAP (PI: D. Berghmans) takes an image of the EUV corona of the sun every minute in an extended field of view. SWAP is able to image all space weather significant events such as flares, coronal holes, dimmings, etc. We will present the technical capabilities of the two instruments and show their complementarity with e.g. SDO. We will discuss the SWAP and LYRA data products and how to make use of them in an operational space weather context. More information is available at http://proba2.sidc.be. Title: On 3D Reconstruction of Coronal Mass Ejections: I. Method Description and Application to SECCHI-COR Data Authors: Mierla, M.; Inhester, B.; Marqué, C.; Rodriguez, L.; Gissot, S.; Zhukov, A. N.; Berghmans, D.; Davila, J. Bibcode: 2009SoPh..259..123M Altcode: The data from SECCHI-COR1 and SECCHI-COR2 coronagraphs onboard the STEREO mission, which was launched in October 2006, provide us with the first-ever stereoscopic images of the Sun's corona. These observations were found to be useful in inferring the three-dimensional structure of coronal mass ejections (CMEs) and their propagation direction in space. We apply four methods for reconstructing CMEs: i) Forward modeling technique; ii) Local correlation tracking (to identify the same feature in COR Ahead and COR Behind images) plus tie-point reconstruction technique; iii) Center of mass of the structures in a given epipolar plane plus tie-point reconstruction technique; iv) Polarization ratio technique. The four techniques are applied to three structured CMEs observed by COR1 and COR2 instruments, respectively, on 15 May 2007, 31 August 2007, and 25 March 2008. A comparison of the results obtained from the application of the four reconstruction algorithms is presented and discussed. Title: On 3D Reconstruction of Coronal Mass Ejections using SECCHI-COR Data Authors: Mierla, M.; Inhester, B.; Marque, C.; Rodriguez, L.; Gissot, S.; Zhukov, A.; Berghmans, D.; Davila, J. Bibcode: 2009EGUGA..11.1145M Altcode: The data from SECCHI-COR1 and SECCHI-COR2 coronagraphs onboard STEREO mission which was launched in October 2006 provided us with the first-ever stereoscopic images of the Sun's corona. These observations were found to be extremely useful in reconstructing the 3D structure of coronal mass ejections (CMEs). We apply four methods for reconstructing the CMEs: 1) Local correlation tracking (to identify the same feature in COR Ahead and COR Behind images) plus tie-point reconstruction technique; 2) Center of mass of the structures along the line of sight (i.e. along each epipolar lines) plus tie-point reconstruction technique; 3) Polarization ratio technique (see for e.g. Moran and Davila 2004); 4) Forward modelling technique (see Thernisien et al. 2006). The four techniques are applied on three structured CMEs observed by COR1 and COR2 instruments on 15 May 2007, 31 August 2007 and 25 March 2008. A comparison of results obtained from the application of the four reconstruction algorithms is presented and discussed. Title: Automated LASCO CME Catalog for Solar Cycle 23: Are CMEs Scale Invariant? Authors: Robbrecht, E.; Berghmans, D.; Van der Linden, R. A. M. Bibcode: 2009ApJ...691.1222R Altcode: 2008arXiv0810.1252R In this paper, we present the first automatically constructed LASCO coronal mass ejection (CME) catalog, a result of the application of the Computer Aided CME Tracking software (CACTus) on the LASCO archive during the interval 1997 September-2007 January. We have studied the CME characteristics and have compared them with similar results obtained by manual detection (CDAW CME catalog). On average, CACTus detects less than two events per day during solar minimum, up to eight events during maximum, nearly half of them being narrow (<20°). Assuming a correction factor, we find that the CACTus CME rate is surprisingly consistent with CME rates found during the past 30 years. The CACTus statistics show that small-scale outflow is ubiquitously observed in the outer corona. The majority of CACTus-only events are narrow transients related to previous CME activity or to intensity variations in the slow solar wind, reflecting its turbulent nature. A significant fraction (about 15%) of CACTus-only events were identified as independent events, thus not related to other CME activity. The CACTus CME width distribution is essentially scale invariant in angular span over a range of scales from 20° to 120° while previous catalogs present a broad maximum around 30°. The possibility that the size of coronal mass outflows follow a power-law distribution could indicate that no typical CME size exists, i.e., that the narrow transients are not different from the larger well defined CMEs. Title: Meeting contribution: The history of the Sunspot Index Authors: Berghmans, D. Bibcode: 2008JBAA..118..348B Altcode: No abstract at ADS Title: SWAP onboard PROBA2: An Innovative EUV Imager Designed for Space Weather Authors: de Groof, A.; Berghmans, D.; Defise, J. M.; Nicula, B.; Schuehle, U. Bibcode: 2008ESPM...122.116D Altcode: PROBA2 (PRoject for OnBoard Autonomy) is an ESA micro-satellite that is being prepared for launch in 2009. Its primary goal is the demonstration of new technologies in the space environment. Furthermore, the satellite carries an ambitious suite of both in-situ and remote sensing instruments for monitoring space weather, despite the modest onboard resources. Both the spacecraft and the remote sensing instruments are mainly developed within Belgium.

One of the main instruments, SWAP (Sun Watcher with APS detectors and image Processing), is a compact EUV imager. It carries the first APS detector with an EUV sensitive scintillator coating to be flown in orbit. In addition to the new detector, the PROBA2/SWAP design is innovative in the sense that the instrument will make heavy use of on-board data processing and autonomous operations. These will range from automatic off-pointing and tracking of appropriate solar events, to pre-downlink data prioritisation, and feature and event recognition procedures.

We discuss the first results of the SWAP pre-flight calibration and the strengths and weaknesses of the instrument [2]. With a narrow spectral bandpass centred around 17.4nm, a FOV of 54 arcmin and an image cadence of 1 min, its design is ideal for monitoring most CME associated phenomena on the solar disk and close to the limb.

[1] Defise J., Halain J., Berghmans D., et al. 2007, In: Proc. SPIE, 6689, 66890S

[2] De Groof A., Berghmans D., Nicula B., et al. 2008, Solar Phys. 249, 147-163 Title: Du nombre de Wolf á l'indice international des taches solaires: 25 ans de SIDC (2e partie) Authors: Clette, Frédéric; Berghmans, David; Vanlommel, Petra; van der Linden, Ronald A. M.; Koeckelenbergh, André; Wauters, Laurence Bibcode: 2008C&T...124...98C Altcode: No abstract at ADS Title: Du nombre de Wolf á l'indice international des taches solaires: 25 ans de SIDC (1e partie) Authors: Clette, Frédéric; Berghmans, David; Vanlommel, Petra; van der Linden, Ronald A. M.; Koeckelenbergh, André; Wauters, Laurence Bibcode: 2008C&T...124...66C Altcode: No abstract at ADS Title: CMOS-APS Detectors for Solar Physics: Lessons Learned during the SWAP Preflight Calibration Authors: De Groof, A.; Berghmans, D.; Nicula, B.; Halain, J. -P.; Defise, J. -M.; Thibert, T.; Schühle, U. Bibcode: 2008SoPh..249..147D Altcode: 2008SoPh..tmp...62D CMOS-APS imaging detectors open new opportunities for remote sensing in solar physics beyond what classical CCDs can provide, offering far less power consumption, simpler electronics, better radiation hardness, and the possibility of avoiding a mechanical shutter. The SWAP telescope onboard the PROBA2 technology demonstration satellite of the European Space Agency will be the first actual implementation of a CMOS-APS detector for solar physics in orbit. One of the goals of the SWAP project is precisely to acquire experience with the CMOS-APS technology in a real-live space science context. Such a precursor mission is essential in the preparation of missions such as Solar Orbiter where the extra CMOS-APS functionalities will be hard requirements. The current paper concentrates on specific CMOS-APS issues that were identified during the SWAP preflight calibration measurements. We will discuss the different readout possibilities that the CMOS-APS detector of SWAP provides and their associated pros and cons. In particular we describe the "image lag" effect, which results in a contamination of each image with a remnant of the previous image. We have characterised this effect for the specific SWAP implementation and we conclude with a strategy on how to successfully circumvent the problem and actually take benefit of it for solar monitoring. Title: Visualization of Distributed Solar Data and Metadata with the Solar Weather Browser Authors: Nicula, B.; Marqué, C.; Berghmans, D. Bibcode: 2008SoPh..248..225N Altcode: 2008SoPh..tmp....7N The Solar Weather Browser (SWB) is a standalone, open-source software tool designed to display solar images with context overlays. It was originally developed for the space-weather forecast activities of the Solar Influence Data analysis Center (SIDC) but it is more generally well suited to display the output of solar-feature recognition methods. The SWB is also useful in the context of distributed solar-image archives, where it could play the role of a quick-look viewer. The SWB allows the user to visually browse large solar data sets and investigate the solar activity for a given date. It has a client - server design that minimizes the bandwidth from the network to the user's monitor. The server processes the data using the SolarSoft library and distributes them through a Web server to which the SWB client connects. The client is readily available for Linux, Mac OS X, and Windows at http://sidc.be/SWB. We discuss the software technology embedded in the SWB as well as its use for solar physics and space weather. Title: SWAP: a novel EUV telescope for space weather Authors: Defise, Jean-Marc; Halain, Jean-Philippe; Berghmans, David; Denis, François; Mazy, Emmanuel; Thibert, Tanguy; Lecat, Jean-Hervé; Rochus, Pierre; Nicula, Bogdan; De Groof, Anik; Hochedez, Jean-François; Schühle, Udo; Ravet, Marie-Françoise; Delmotte, Frank Bibcode: 2007SPIE.6689E..0SD Altcode: 2007SPIE.6689E..24D The SWAP telescope (Sun Watcher using Active Pixel System detector and Image Processing) is being developed to be part of the PROBA2 payload, an ESA technological mission to be launched in early 2008. SWAP is directly derived from the concept of the EIT telescope that we developed in the '90s for the SOHO mission. Several major innovations have been introduced in the design of the instrument in order to be compliant with the requirements of the PROBA2 mini-satellite: compactness with a new of-axis optical design, radiation resistance with a new CMOS-APS detector, a very low power electronics, an athermal opto-mechanical system, optimized onboard compression schemes combined with prioritization of collected data, autonomy with automatic triggering of observation and off-pointing procedures in case of Solar event occurrence, ... All these new features result from the low resource requirements (power, mass, telemetry) of the mini-satellite, but also take advantage of the specificities of a modern technological platform, such as quick pointing agility, new powerful on-board processor, Packetwire interface and autonomous operations. These new enhancements will greatly improve the operations of SWAP as a space weather sentinel from a low Earth orbit while the downlink capabilities are limited. This paper summarizes the conceptual design, the development and the qualification of the instrument, the autonomous operations and the expected performances for science exploitation. Title: Helio-informatics: Preparing For The Future Of Heliophysics Research. Authors: Schrijver, Carolus J.; Hurlburt, N. E.; Cheung, M. C.; Title, A. M.; Delouille, V.; Hochedez, J.; Berghmans, D. Bibcode: 2007AAS...210.2514S Altcode: 2007BAAS...39..133S The rapidly growing data volumes for space- and ground-based observatories for Sun and heliosphere will soon make it impractical, costly, and perhaps effectively impossible for researchers to download and locally inspect substantial portions of the data archives. By the end of 2008, for example, the Solar Dynamics Observatory will downlink over 2TB/day of compressed data; such a large volume would readily saturate internet connections to the archive site if it were exported to a handful of researchers around the world. We envision a revolution in research methodology towards a mode in which researchers run autonomous event-finding algorithms at a primary data archive in order to pre-select relatively small subsets of the data that can subsequently be inspected and analyzed in detail at a researcher's home institution. Teams from the SDO, Hinode, STEREO, and TRACE missions are developing the infrastructure that is needed to make this into a useful research tool: we are (1) defining standardized event attributes compatible with the Virtual Observatory and EGSO concepts, (2) developing a knowledge base supported by a web-based tool for compound queries based on the contents of solar and heliospheric observations, and (3) assembling a group of researchers who are interested in helping us develop a prototype system while beta-testing it in real scientific studies. We invite you to contact us (a) if you have feature-finding algorithms that you would like to see applied to existing data archives, (b) if you would like to contribute expertise in developing the knowledge-base system, or (c) if you would like to participate in the testing of the system for scientific use. More information on our plans, target dates, and contact information can be found at http://www.lmsal.com/helio-informatics/hpkb/.

The helio-informatics project is being developed with support from the HINODE/SOT (NNM07AA01C), SDO/AIA (NNG04EA00C), STEREO/SECCHI (N00173-02-C-2035), and TRACE (NAS5-38099) science investigations. Title: From the Wolf number to the International Sunspot Index: 25 years of SIDC Authors: Clette, Frédéric; Berghmans, David; Vanlommel, Petra; Van der Linden, Ronald A. M.; Koeckelenbergh, André; Wauters, Laurence Bibcode: 2007AdSpR..40..919C Altcode: By encompassing four centuries of solar evolution, the sunspot number provides the longest available record of solar activity. Nowadays, it is widely used as the main reference solar index on which hundreds of published studies are based, in various fields of science. In this review, we will retrace the history of this crucial solar index, from its roots at the Zürich Observatory up to the current multiple indices established and distributed by the Solar Influences Data Analysis Center (SIDC), World Data Center for the International Sunspot Index, which was founded in 1981, exactly 25 years ago. We describe the principles now in use for the statistical processing of input data coming from the worldwide observing network (∼80 stations). Among the various SIDC data products and innovations, we highlight some recent ones, including the daily Estimated International Sunspot Number. Taking a wider perspective, we show how the sunspot index stands the test of time versus more recent quantitative indices, but we also consider the prospects and possible options for a future transition from the visual sunspot index heritage towards an equivalent global activity index. Based on past historical flaws, we conclude on the key requirements involved in the maintenance of any robust long-term solar activity index. Title: Current and future space weather services and products from the SIDC- Brussels Authors: Lawrence, G.; Kretzschmar, M.; Berghmans, D.; Clete, F.; Hochedez, J.; van der Linden, R.; Delouille, V.; Gissot, S.; Marque, C.; Nicula, B.; Patoul, J.; Podladchikova, E.; Robbrecht, E.; Vanlommel, P.; Dehant, V. Bibcode: 2006AGUFMSA51A..04L Altcode: The SIDC-Brussels, as WDC for the sunspot index and European RWC of the ISES, is the European hub for solar data and forecasts. Its services and products, while long established and widely recognised and used, are continuously being enhanced and supplemented. We present in detail the current status and outline the imminent improvements and additions. The Solar Weather Browser (SWB) is a free, downloadable, multi-platform visualisation package for real-time browsing of processed solar images from a variety of space and ground based sources, combined with context information (events, regions IDs, etc.) via a wide choice of overlay combinations. The Estimated International Sunspot Number (EISN) has been produced and distributed daily since January 2006 by the SIDC. Intended to support operational model predictions of ionospheric radio propagation, we present some early statistical results. CACTus, the operational Computer-Aided CME Tracking algorithm, now freely available to the community via the SSW software framework, is being tested for its real-time application to the STEREO/SECCHI COR-2 "space weather beacon" coronagraph telemetry stream. Also NEMO, a software package for the automated detection and morphological analysis of EIT waves presently being tested, details the relation between coronal EUV wave fronts and dimmings and characterizes their evolution; we present sample results of both developments. The Velociraptor software processes and interprets movies of the EUV solar corona, an algorithm identifying outstanding motions such as loop openings that are associated to space weather events. Sample results using EIT and TRACE data will be shown. A new flare catalog called B2X is presented, compliled via a method to detect automatically, and characterise according to time, localization, size, EUV flares belonging to classes B to X anywhere on the solar disc and at the limb. In addition we present a summary of the full range of products available from SIDC which can be chosen in any combination tailored to the individual, or group's needs. All products are available via the revamped SIDC website, http://www.sidc.be Title: A Broad Perspective on Automated CME Tracking: Towards Higher Level Space Weather Forecasting Authors: Robbrecht, Eva; Berghmans, David Bibcode: 2006GMS...165...33R Altcode: We discuss our current capabilities to deliver the CME parameters required for the space weather forecasting process. The ever growing importance of space weather has lead to new requirements on the timeliness and objectiveness of CME detection. It has become indispensable to report the occurrence of Earth-directed CMEs and to predict their possible impact on the geospace environment. Early 2005, we are on the eve of a new era in space weather forecasting. We point out the restricted accuracy on the current forecasts and discuss a chance for amelioration. This invokes data-driven models (empirical and numerical), triggered by a real-time CME disturbance, simulating the propagation and interaction of the ejection with the ambient solar wind. We discuss the link between the direct observable parameters (like the CME projected speed and angle around the occulter) and the required input parameters (like radial speed, direction, …). The only way to guarantee the real-time value of the simulations is by employing software which autonomously detect CME parameters in a variety of data. This paper focusses on the automated CME detection algorithms that are currently available. Automated CME tracking is yet in its infancy, therefore this `review' will be an outlook on the potential of this field rather than looking back on already achieved milestones. Title: A broad Perspective on Automated CME Tracking: towards higher level space weather forecasting Authors: Robbrecht, E.; Berghmans, D. Bibcode: 2006GMS...165.....R Altcode: We discuss our current capabilities to deliver the CME parameters required for the space weather forecasting process. The ever growing importance of space weather has lead to new requirements on the timeliness and objectiveness of CME detection. It has become indispensable to report the occurrence of Earth-directed CMEs and to predict their possible impact on the geospace environment. Early 2005, we are on the eve of a new era in space weather forecasting. We point out the restricted accuracy on the current forecasts and discuss a chance for amelioration. This invokes data-driven models (empirical and numerical), triggered by a real-time CME disturbance, simulating the propagation and interaction of the ejection with the ambient solar wind. We discuss the link between the direct observable parameters (like the CME projected speed and angle around the occulter) and the required input parameters (like radial speed, direction, ...). The only way to guarantee the real-time value of the simulations is by employing software which autonomously detect CME parameters in a variety of data. This paper focusses on the automated CME detection algorithms that are currently available. Automated CME tracking is yet in its infancy, therefore this `review' will be an outlook on the potential of this field rather than looking back on already achieved milestones. Title: SWAP: An EUV imager for solar monitoring on board of PROBA2 Authors: Katsiyannis, A. C.; Berghmans, D.; Nicula, B.; Defise, J. -M.; Lawrence, G.; Lecat, J. -H.; Hochedez, J. -F.; Slemzin, V. Bibcode: 2006AIPC..848..847K Altcode: PROBA2 is an ESA technology demonstration mission to be launched in 2007. The prime instrument on board of Proba2 is SWAP (Sun Watcher using Active Pixel System detector and Image Processing), a full disk solar imager with a bandpass filter centred at 17.5 nm (Fe IX-XI) and a fast cadence of ~ 1 min. The telescope is based on an off-axis Ritchey Chretien design while an extreme ultraviolet (EUV) enhanced APS CMOS will be used as a detector. As the prime goal of the SWAP is solar monitoring and advance warning of Coronal Mass Ejections (CME), on-board intelligence will be implemented. Image recognition software using experimental algorithms will be used to detect CMEs during the first phase of eruption so the event can be tracked by the spacecraft without human intervention. Title: History of the Sunspot Index: 25 years SIDC Authors: Berghmans, D.; van der Linden, R. A. M.; Vanlommel, P.; Clette, F.; Robbrecht, E. Bibcode: 2006BGGKP...7..288B Altcode: The sunspot number is the oldest solar activity index. For a long time, it was the only index representative of the solar cycle, and many studies on the cyclical behavior of the Sun were performed using the sunspot number. The Sunspot Index Data Center (SIDC) was founded in January 1981 to continue the work of the Swiss Federal Observatory , when this institution decided to stop computing and publishing the sunspot number. The SIDC now also provides daily activity reports and forecasts of the status of the space environment. This 'space weather' activity is part of the International Space Environment Services (ISES, a permanent service of the FAGS) that co-ordinates 10 regional warning centers (RWC). In this paper we will give an overview of the history of the sunspot number, as well as a short overview of the 25-year history of the SIDC. Title: LYRA and SWAP aboard PROBA2 - heralding future solar VUV observations Authors: Hochedez, J. -F.; Berghmans, D.; Defise, J. -M. Bibcode: 2006cosp...36.3272H Altcode: 2006cosp.meet.3272H Two novel solar VUV instruments will be launched with the PROBA2 mission in the end of 2007 SWAP is a EUV solar imaging telescope and LYRA is a VUV filter radiometer We will discuss the interest of the new observations that can be expected from each of them and show in which sense LYRA and SWAP address the technological and scientific questions of future solar VUV observations Title: Objective CME detection over the solar cycle: A first attempt Authors: Robbrecht, E.; Berghmans, D.; van der Linden, R. A. M. Bibcode: 2006AdSpR..38..475R Altcode: We recently developed a software package to autonomously detect coronal mass ejections (CMEs) in image sequences from large angle spectrometric coronagraph (LASCO). The detection is not done in the original images, instead we detect bright ridges in (time, height) plots using a modified version of the Hough transform. Experimental results on real-time data have shown that the developed technique can achieve excellent results in measuring starting time and principal angle and good results for the angular width and velocity measurement compared to the CMEs listed in the manually assembled catalog. The real-time output of the software can be found online at www.sidc.oma.be/cactus. With the present paper, we report on the first large scale application of the software to the LASCO archive. In an ongoing work, we have applied the software on a first sample of 29 months selected from archive data in the period July 1997 to December 2002. The results in this paper show that relevant characteristics of CMEs over the solar cycle are successfully recovered with the automated procedure. This proves that a completely automatically produced CME catalog is within reach. Title: LYRA, a solar UV radiometer on Proba2 Authors: Hochedez, J. -F.; Schmutz, W.; Stockman, Y.; Schühle, U.; Benmoussa, A.; Koller, S.; Haenen, K.; Berghmans, D.; Defise, J. -M.; Halain, J. -P.; Theissen, A.; Delouille, V.; Slemzin, V.; Gillotay, D.; Fussen, D.; Dominique, M.; Vanhellemont, F.; McMullin, D.; Kretzschmar, M.; Mitrofanov, A.; Nicula, B.; Wauters, L.; Roth, H.; Rozanov, E.; Rüedi, I.; Wehrli, C.; Soltani, A.; Amano, H.; van der Linden, R.; Zhukov, A.; Clette, F.; Koizumi, S.; Mortet, V.; Remes, Z.; Petersen, R.; Nesládek, M.; D'Olieslaeger, M.; Roggen, J.; Rochus, P. Bibcode: 2006AdSpR..37..303H Altcode: LYRA is the solar UV radiometer that will embark in 2006 onboard Proba2, a technologically oriented ESA micro-mission. LYRA is designed and manufactured by a Belgian Swiss German consortium (ROB, PMOD/WRC, IMOMEC, CSL, MPS and BISA) with additional international collaborations. It will monitor the solar irradiance in four UV passbands. They have been chosen for their relevance to Solar Physics, Aeronomy and Space Weather: (1) the 115 125 nm Lyman-α channel, (2) the 200 220 nm Herzberg continuum range, (3) the Aluminium filter channel (17 70 nm) including He II at 30.4 nm and (4) the Zirconium filter channel (1 20 nm). The radiometric calibration will be traceable to synchrotron source standards (PTB and NIST). The stability will be monitored by onboard calibration sources (LEDs), which allow to distinguish between potential degradations of the detectors and filters. Additionally, a redundancy strategy maximizes the accuracy and the stability of the measurements. LYRA will benefit from wide bandgap detectors based on diamond: it will be the first space assessment of a pioneering UV detectors program. Diamond sensors make the instruments radiation-hard and solar-blind: their high bandgap energy makes them insensitive to visible light and, therefore, make dispensable visible light blocking filters, which seriously attenuate the desired ultraviolet signal. Their elimination augments the effective area and hence the signal-to-noise, therefore increasing the precision and the cadence. The SWAP EUV imaging telescope will operate next to LYRA on Proba2. Together, they will establish a high performance solar monitor for operational space weather nowcasting and research. LYRA demonstrates technologies important for future missions such as the ESA Solar Orbiter. Title: A Complete LASCO CME-Catalog based on Automated Detection Authors: Robbrecht, E.; Berghmans, D.; van der Linden, R. A. M. Bibcode: 2006cosp...36.3564R Altcode: 2006cosp.meet.3564R We present our new CME catalog a result of the large scale application of our software CACTus on the LASCO archive We recently improved the algorithm and upgraded the test-version of the catalog available online at www sidc be cactus The automatic detection of a CME is done in two steps and is applied simultaneously on c2 and c3 running difference images 1 detection of bright features moving radially outward 2 clustering detections into CMEs The recent improvements are undertaken in the second step of this process Unique for our detection method is that we use the condition moving radially outward as part of the detection criterion The detection itself is done using the stroboscopic method i e in height time slices where height means radial distance from the sun An outwardly moving feature appears then as a bright ridge extracted by a modified version of the Hough transform Per month the output consists of a table containing the CME characteristics and an overview map in a angle time -coordinate system that clearly shows all detected CMEs As a result of our method we also have for each CME a linear speed profile along the angular width of the CME We studied the characteristics of the CMEs detected with CACTus over the solar cycle and compared them with results obtained from other catalogs This paper shows that relevant characteristics of CMEs over the solar cycle are successfully recovered with the automated procedure Recent tests prove that in general automated procedures detect far more small features than human Title: SWAP onboard PROBA 2, a new EUV imager for solar monitoring Authors: Berghmans, D.; Hochedez, J. F.; Defise, J. M.; Lecat, J. H.; Nicula, B.; Slemzin, V.; Lawrence, G.; Katsyiannis, A. C.; van der Linden, R.; Zhukov, A.; Clette, F.; Rochus, P.; Mazy, E.; Thibert, T.; Nicolosi, P.; Pelizzo, M. -G.; Schühle, U. Bibcode: 2006AdSpR..38.1807B Altcode: SWAP (Sun Watcher using Active Pixel system detector and image processing) is a solar imager in the extreme ultraviolet (EUV) that has been selected to fly in 2007 on the PROBA 2 technological platform, an ESA program. SWAP will use an off-axis Ritchey Chrétien telescope equipped with an EUV enhanced active pixel sensor detector (coated APS). This type of detector has advantages that promise to be very profitable for solar EUV imaging. SWAP will provide solar coronal images at a 1-min cadence in a bandpass centered on 17.5 nm. Observations with this specific wavelength allow detecting phenomena, such as solar flares or EIT-waves, associated with the early phase of coronal mass ejections. Image processing software will be developed that automatically detects these phenomena and sends out space weather warnings. Together with its sister instrument LYRA, also onboard PROBA 2, SWAP will serve as a high performance solar monitoring tool to be used in operational space weather forecasting. The SWAP data will complement the solar observations provided by instruments like SOHO-EIT, and STEREO-SECCHI. Title: Detailed comparison of downflows seen both in EIT 30.4 nm and Big Bear Hα movies Authors: de Groof, A.; Bastiaensen, C.; Müller, D. A. N.; Berghmans, D.; Poedts, S. Bibcode: 2005A&A...443..319D Altcode: An EIT shutterless campaign was conducted on 11 July 2001 and provided 120 high-cadence (68 s) 30.4 nm images of the north-eastern quarter of the Sun. Systematic intensity variations are seen which appear to propagate along an off-disk loop-like structure. In this paper we study the nature of these intensity variations by confronting the EIT observations studied in De Groof et al. (2004, A&A, 415, 1141) with simultaneous Hα images from Big Bear Solar Observatory. With the goal to carefully co-register the two image sets, we introduce a technique designed to compare data of two different instruments. The image series are first co-aligned and later overplotted in order to visualize and compare the behaviour of the propagating disturbances in both data sets. Since the same intensity variations are seen in the EIT 30.4 nm and in the Hα images, we confirm the interpretation of De Groof et al. (2004, A&A, 415, 1141) that we are observing downflows of relatively cool plasma. The origin of the downflows is explained by numerical simulations of "catastrophic cooling" in a coronal loop which is heated predominantly at its footpoints. Title: Solar weather monitoring Authors: Hochedez, J. -F.; Zhukov, A.; Robbrecht, E.; van der Linden, R.; Berghmans, D.; Vanlommel, P.; Theissen, A.; Clette, F. Bibcode: 2005AnGeo..23.3149H Altcode: Space Weather nowcasting and forecasting require solar observations because geoeffective disturbances can arise from three types of solar phenomena: coronal mass ejections (CMEs), flares and coronal holes. For each, we discuss their definition and review their precursors in terms of remote sensing and in-situ observations. The objectives of Space Weather require some specific instrumental features, which we list using the experience gained from the daily operations of the Solar Influences Data analysis Centre (SIDC) at the Royal Observatory of Belgium. Nowcasting requires real-time monitoring to assess quickly and reliably the severity of any potentially geoeffective solar event. Both research and forecasting could incorporate more observations in order to feed case studies and data assimilation respectively. Numerical models will result in better predictions of geomagnetic storms and solar energetic particle (SEP) events. We review the data types available to monitor solar activity and interplanetary conditions. They come from space missions and ground observatories and range from sequences of dopplergrams, magnetograms, white-light, chromospheric, coronal, coronagraphic and radio images, to irradiance and in-situ time-series. Their role is summarized together with indications about current and future solar monitoring instruments. Title: Solar activity: nowcasting and forecasting at the SIDC Authors: Berghmans, D.; van der Linden, R. A. M.; Vanlommel, P.; Warnant, R.; Zhukov, A.; Robbrecht, E.; Clette, F.; Podladchikova, O.; Nicula, B.; Hochedez, J. -F.; Wauters, L.; Willems, S. Bibcode: 2005AnGeo..23.3115B Altcode: The Solar Influences Data analysis Center (SIDC) is the World Data Center for the production and the distribution of the International Sunspot Index, coordinating a network of about 80 stations worldwide. From this core activity, the SIDC has grown in recent years to a European center for nowcasting and forecasting of solar activity on all timescales. This paper reviews the services (data, forecasts, alerts, software) that the SIDC currently offers to the scientific community. The SIDC operates instruments both on the ground and in space. The USET telescope in Brussels produces daily white light and Hα images. Several members of the SIDC are co-investigators of the EIT instrument onboard SOHO and are involved in the development of the next generation of Europe's solar weather monitoring capabilities. While the SIDC is staffed only during day-time (7 days/week), the monitoring service is a 24 h activity thanks to the implementation of autonomous software for data handling and analysis and the sending of automated alerts. We will give an overview of recently developed techniques for visualization and automated analysis of solar images and detection of events significant for space weather (e.g. CMEs or EIT waves). As part of the involvement of the SIDC in the ESA Pilot Project for Space Weather Applications we have developed services dedicated to the users of the Global Positioning System (GPS). As a Regional Warning Center (RWC) of the International Space Environment Service (ISES), the SIDC produces daily forecasts of flaring probability, geomagnetic activity and 10.7 cm radio flux. The accuracy of these forecasts will be investigated through an in-depth quality analysis. Title: Swap: AN EUV Imager for Solar Monitoring on Board of PROBA2 Authors: Katsiyannis, A. C.; Berghmans, D.; Nicula, B.; Defise, J. -M.; Lawrence, G.; Lecat, J. -H.; Hochedez, J. -F.; Slemzin, V. Bibcode: 2005ESASP.596E..70K Altcode: 2005ccmf.confE..70K No abstract at ADS Title: Energetic Dymanics of EIT Wave Structure Analyzed by EIT Wave Detector Authors: Podladchikova, O.; Berghmans, D. Bibcode: 2005ESASP.592..751P Altcode: 2005soho...16E.153P; 2005ESASP.592E.153P No abstract at ADS Title: Space Weather with ESA's PROBA2 Mission Authors: Lawrence, G.; Berghmans, D.; Hochedez, J. -F.; Ben-Moussa, A.; Defise, J. -M.; Delouille, V.; Dominique, M.; Katsitannis, A.; Lecat, J. -H.; Nicula, B.; Schmutz, W.; Slemzin, V.; Theissen, A. Bibcode: 2005ESASP.592..685L Altcode: 2005ESASP.592E.137L; 2005soho...16E.137L No abstract at ADS Title: Interaction of EIT Wave With Active Regions on the Sun Authors: Podladchikova, O.; Berghmans, D. Bibcode: 2005ESASP.592..535P Altcode: 2005soho...16E.100P; 2005ESASP.592E.100P No abstract at ADS Title: SWAP: an EUV imager for solar monitoring on board of PROBA2 Authors: Katsiyannis, Athanassios C.; Berghmans, David; Hochedez, Jean-Francois; Nicula, Bogdan; Lawrence, Gareth; Defise, Jean-Marc; Ben-Moussa, Ali; Delouille, Veronique; Dominique, Marie; Lecat, Jean-Herve; Schmutz, W.; Theissen, Armin; Slemzin, Vladimir Bibcode: 2005SPIE.5901..236K Altcode: PROBA2 is an ESA technology demonstration mission to be launched in early 2007. The two primary scientific instruments on board of PROBA2 are SWAP (Sun Watcher using Active Pixel System detector and Image Processing) and the LYRA VUV radiometer. SWAP provides a full disk solar imaging capability with a bandpass filter centred at 17.5 nm (FeIX-XI) and a fast cadence of ≈1 min. The telescope is based on an off-axis Ritchey Chretien design while an extreme ultraviolet (EUV) enhanced APS CMOS will be used as a detector. As the prime goal of the SWAP is solar monitoring and advance warning of Coronal Mass Ejections (CME), on-board intellige nce will be implemented. Image recognition software using experimental algorithms will be used to detect CMEs during the first phase of eruption so the event can be tracked by the spacecraft without huma n intervention. LYRA will monitor solar irradiance in four different VUV passbands with a cadence of up to 100 Hz. The four channels were chosen for their relevance to solar physics, aeronomy and space weather: 115-125 nm (Lyman-α), 200-220 nm Herzberg continuum, the 17-70 nm Aluminium filter channel (that includes the HeII line at 30.4 nm) and the 1-20 nm Zirconium filter channel. On-board calibration sources will monitor the stability of the detectors and the filters throughout the duration of the mission. Title: Poisson Recoding Of Solar Images For Enhanced Compression Authors: Nicula, Bogdan; Berghmans, David; Hochedez, Jean-François Bibcode: 2005SoPh..228..253N Altcode: The amount of useful scientific data that a space-borne telescope produces is often limited by the available telemetry of the platform. General purpose image compression schemes are usually used to compress the image either lossy or losslessly. These schemes do not take into account the fact that pixel values of typical solar images are only known to within a certain uncertainty range. We present a preprocessing method to enhance the performance (compression ratio) of any subsequent image compression scheme. The method uses estimates of the photon shot and thermal noises to compute a recoding look-up table that maps the initial data into uncertainty intervals. The recoding method is lossy in a mathematical sense but lossless in a physical sense, since the image alterations are guaranteed to be smaller than the Poisson noise. The performance of any further compression algorithm is enhanced while achieving a known guaranteed maximum absolute error for each pixel in the case of lossless compression. Title: Foreword Authors: Gallagher, Peter; Berghmans, David; Aschwanden, Markus Bibcode: 2005SoPh..228....1G Altcode: No abstract at ADS Title: Automated Detection Of Eit Waves And Dimmings Authors: Podladchikova, Olena; Berghmans, David Bibcode: 2005SoPh..228..265P Altcode: Studies of the onset of Earth-directed coronal mass ejections (CMEs) rely on solar disk observations where CME structures are difficult to disentangle because of the diversity and transient character of the phenomena involved. Dimmings and coronal waves are among the best evidence of the large-scale reorganization of coronal magnetic fields associated with the onset of CMEs. The physical mechanism behind EIT waves is still unclear: they are considered as MHD waves and/or as a consequence of plasma compression on the extending border of a dimming. In this paper, we address the problem of automatically detecting and analyzing EIT waves and dimmings in EUV images. This paper presents a "proof of principle" that automated detection of EIT wave and dimmings is indeed possible. At the current stage of work, the method can unambiguously detect dimmings and EIT waves when applied on a typical test-case event. Moreover, we propose a way to extract these events from the data, and determine such parameters as life time, depth, area and volume of dimmings for future catalogs. For EIT waves we unambiguously define, in near solar minimum conditions, the eruption center, the front of EIT wave and its propagation velocity. In addition, we show that the presented methods yield new insights about the geometrical shape of dimmings and the connection with the EIT wave front properties, and the apparent angular rotation of the EIT wave under study. Title: Entering The Era Of Automated Cme Recognition: A Review Of Existing Tools Authors: Robbrecht, E.; Berghmans, D. Bibcode: 2005SoPh..228..239R Altcode: We consider the problem of the observational identification of CMEs. The ever growing importance of space weather has led to new requirements on the timeliness and objectiveness of CME detection. It is not sufficient any more to simply detect CMEs, a complete set of characteristics (speed, direction, mass, chirality) must be reported as soon as possible to estimate its geoeffectiveness. Recent developments in (solar) feature recognition greatly improved the ability to address these new needs. Progress was achieved in automating the detection of CMEs in coronagraphic data. This has led to near-real-time messages alerting the space weather community day and night. In attempting to generate ever-prompter alerts, we can employ a far broader set of solar observations than coronagraphic data alone. At present an extensive set of automatic recognition tools exists for a number of CME-related phenomena occurring in the lower corona. This paper deals with detection techniques for disappearing filaments in Hα images, dimmings, EIT waves and erupting prominences in radio data. We believe that incorporating all automatically generated alerts into one report per CME can provide valuable CME information, especially when no coronagraphic images are available. This paper is thus a quest to reach a maximal success rate with the help of an integrated system of tools acting on a variety of data. Future grid-technology systems will greatly facilitate this. Title: Automated recognition of coronal mass ejections (CMEs) in near-real-time data Authors: Robbrecht, E.; Berghmans, D. Bibcode: 2004A&A...425.1097R Altcode: This paper presents a new method and first applications of software that we have developed to autonomously detect CMEs in image sequences from LASCO (Large Angle Spectrometric Coronagraph). The crux of the software is the detection of CMEs as bright ridges in (time, height) maps using the Hough transform. The next step employs clustering and morphological closing operations to mark out different CMEs. The output is a list of events, similar to the classic catalogs, with starting time, principle angle, angular width and velocity estimation for each CME. In addition we present a new type of CME overview map that clearly shows all detected CMEs in a (principal angle, time of occurrence) coordinate system. In contrast to catalogs assembled by human operators, these CME detections can be done without any human interference on real-time data 24 h per day (see http://sidc.oma.be/cactus for the real-time output with data covering the last 4 days). Therefore the detection is not only more immediate, but, more importantly, also more objective. In this paper we describe the software and validate its performance by comparing its output with the SOHO LASCO CME catalog. Experimental results on real-time data show that the developed technique can achieve excellent results in measuring starting time and principal angle and good results for the angular width and velocity measurement compared to the CMEs listed in the catalog. Its overall success rate is presently about 94%. The software also reveals CMEs or other features that have not been listed in the catalog. Such unreported cases might influence CME statistics and they demonstrate that also the present catalogs do not have a 100% success rate. This inevitably leads to a discussion on the definition of a CME. Prospects for improvement and exploitation are discussed. Title: The Sidc: World Data Center for the Sunspot Index Authors: Vanlommel, P.; Cugnon, P.; Linden, R. A. M. Van Der; Berghmans, D.; Clette, F. Bibcode: 2004SoPh..224..113V Altcode: 2005SoPh..224..113V Since January 1981, the Royal Observatory of Belgium (ROB) has operated the Sunspot Index Data Center (SIDC), the World Data Center for the Sunspot Index. From 2000, the SIDC obtained the status of Regional Warning Center (RWC) of the International Space Environment Service (ISES) and became the "Solar Influences Data analysis Center". As a data analysis service of the Federation of Astronomical and Geophysical data analysis Services (FAGS), the SIDC collects monthly observations from worldwide stations in order to calculate the International Sunspot Number, Ri. The center broadcasts the daily, monthly, yearly sunspot numbers, with middle-range predictions (up to 12 months). Since August 1992, hemispheric sunspot numbers are also provided. Title: SWAP: Sun watcher with a new EUV telescope on a technology demonstration platform Authors: Defise, Jean-Marc; Lecat, Jean-Hervé; Mazy, Emmanuel; Rochus, Pierre; Rossi, Laurence; Thibert, Tanguy; Gillis, Jean-Marie; Berghmans, David; Hochedez, Jean-François; Schühle, Udo Bibcode: 2004ESASP.554..257D Altcode: 2004icso.conf..257D SWAP (SWAP (Sun Watcher using Active Pixel System detector and Image Processing) is an instrument that has been selected to fly on the PROBA-2 technology demonstration platform, a program of the European Space Agency (ESA) to be launched in 2006. SWAP is based on an off-axis degraded Ritchey Chretien telescope that will image the EUV solar corona at 19.5 nm on a specifically fabricated extreme ultraviolet (EUV) sensitivity enhanced CMOS APS detector. The optical design and the optical coatings are derived from the Extreme Ultraviolet Imaging Telescope (EIT) operating on-board SOHO since 1995. It has been adapted for a single wavelength telescope with off-axis optics. It allows to use smaller optics and filters, with simple internal baffles avoiding external protruding parts. The superpolished optics will receive a multilayer coating that provides spectral selection centred on 19.5 nm and EUV reflectivity in normal incidence. This compact design is specifically adapted for accommodation on PROBA-2, where mass and envelope requirements are very stringent The SWAP PROBA-2 program will be an opportunity to demonstrate this new optical concept, while it will also validate space remote sensing with APS detectors, as well as on-board image processing capabilities. On the science outcomes, SWAP will provide solar corona images in the Fe XII line on a baselined 2-min cadence. Observations with this specific wavelength allow detecting phenomena, such as solar flares or 'EIT-waves', associated with the early phase of coronal mass ejections. The SWAP data will complement the observations provided by SOHO-EIT, and STEREO-SECCHI. Title: Intensity variations in EIT shutterless mode: Waves or flows? Authors: De Groof, A.; Berghmans, D.; van Driel-Gesztelyi, L.; Poedts, S. Bibcode: 2004A&A...415.1141D Altcode: On 11 July 2001 an EIT shutterless campaign was conducted which provided 120 high-cadence (68 s) 304 Å images of the north eastern quarter of the Sun. The most interesting feature seen in the data is an off-limb half loop structure along which systematic intensity variations are seen which appear to propagate from the top of the loop towards its footpoint. We investigate the underlying cause of these propagating disturbances, i.e. whether they are caused by waves or by plasma flows. First we identify 7 blobs with the highest intensities and follow them along the loop. By means of a location-time plot, bulk velocities can be measured at several locations along the loop. The velocity curve found this way is then compared with characteristic wave speeds and with the free-fall speed in order to deduce the nature of the intensity variations. Additional information on density and temperature is derived by measuring the relative intensity enhancements and comparing the EIT 304 Å sequence with Big Bear data and 171 Å data (TRACE/EIT). The combination of all these constraints gives us an insight on the nature and origin of these intensity variations. The idea of slow magneto-acoustic waves is rejected, and we find several arguments supporting that these intensity variations are due to flowing/falling plasma blobs. Title: SWAP: Sun watcher using APS detector on-board PROBA-2, a new EUV off-axis telescope on a technology demonstration platform Authors: Defise, Jean-Marc; Berghmans, David; Hochedez, Jean-Francois E.; Lecat, Jean-Herve M.; Mazy, Emmanuel; Rochus, Pierre L.; Thibert, Tanguy; Nicolosi, Piergiorgio; Pelizzo, Maria G.; Schuehle, Udo H.; Van der Linden, Ronald A. M.; Zhukov, Andrei N. Bibcode: 2004SPIE.5171..143D Altcode: SWAP (Sun Watcher using Active Pixel System detector and Image Processing) is an instrument that has been selected to fly on the PROBA-II technology demonstration platform, a program of the European Space Agency (ESA) to be launched in 2006. This paper presents the instrument concept and its scientific goals. SWAP uses an off-axis Ritchey Chretien telescope that will image the EUV solar corona at 19.5 nm on a specifically fabricated extreme ultraviolet (EUV) sensitivity enhanced CMOS APS detector. This type of detector has advantages that promise to be very profitable for solar EUV imaging. The SWAP design is built on a similar concept as the MAGRITTE instrument suite for the NASA Solar Dynamics Observatory (SDO) mission to be launched in 2007. The optics have been adapted to the detector size. The SWAP PROBA-2 program will be an opportunity to demonstrate and validate the optical concept of MAGRITTE, while it will also validate space remote sensing with APS detectors. On the science outcomes, SWAP will provide solar corona images in the Fe XII line on a baselined 1-min cadence. Observations with this specific wavelength allow detecting phenomena, such as solar flares or 'EIT-waves", associated with the early phase of coronal mass ejections. Image recognition software will be developed that automatically detects these phenomena and sends out space weather warnings. Different modules of this software will run both on the ground system as well as on the onboard computer of PROBA II. The SWAP data will complement the observations provided by SOHO-EIT, and STEREO-SECCHI. Title: MAGRITTE: an instrument suite for the solar atmospheric imaging assembly (AIA) aboard the Solar Dynamics Observatory Authors: Rochus, Pierre L.; Defise, Jean-Marc; Halain, Jean-Philippe; Jamar, Claude A. J.; Mazy, Emmanuel; Rossi, Laurence; Thibert, Tanguy; Clette, Frederic; Cugnon, Pierre; Berghmans, David; Hochedez, Jean-Francois E.; Delaboudiniere, Jean-Pierre; Auchere, Frederic; Mercier, Raymond; Ravet, Marie-Francoise; Delmotte, Franck; Idir, Mourad; Schuehle, Udo H.; Bothmer, Volker; Fineschi, Silvano; Howard, Russell A.; Moses, John D.; Newmark, Jeffrey S. Bibcode: 2004SPIE.5171...53R Altcode: The Solar Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory will characterize the dynamical evolution of the solar plasma from the chromosphere to the corona, and will follow the connection of plasma dynamics with magnetic activity throughout the solar atmosphere. The AIA consists of 7 high-resolution imaging telescopes in the following spectral bandpasses: 1215Å. Ly-a, 304 Å He II, 629 Å OV, 465 Å Ne VII, 195 Å Fe XII (includes Fe XXIV), 284 Å Fe XV, and 335 Å Fe XVI. The telescopes are grouped by instrumental approach: the MAGRITTE Filtergraphs (R. MAGRITTE, famous 20th Century Belgian Surrealistic Artist), five multilayer EUV channels with bandpasses ranging from 195 to 1216 Å, and the SPECTRE Spectroheliograph with one soft-EUV channel at OV 629 Å. They will be simultaneously operated with a 10-second imaging cadence. These two instruments, the electronic boxes and two redundant Guide Telescopes (GT) constitute the AIA suite. They will be mounted and coaligned on a dedicated common optical bench. The GTs will provide pointing jitter information to the whole SHARPP assembly. This paper presents the selected technologies, the different challenges, the trade-offs to be made in phase A, and the model philosophy. From a scientific viewpoint, the unique combination high temporal and spatial resolutions with the simultaneous multi-channel capability will allow MAGRITTE / SPECTRE to explore new domains in the dynamics of the solar atmosphere, in particular the fast small-scale phenomena. We show how the spectral channels of the different instruments were derived to fulfill the AIA scientific objectives, and we outline how this imager array will address key science issues, like the transition region and coronal waves or flare precursors, in coordination with other SDO experiments. We finally describe the real-time solar monitoring products that will be made available for space-weather forecasting applications. Title: The expanding space weather services of the SIDC at the Royal Observatory of Belgium Authors: van der Linden, R. A. M.; Berghmans, D.; Vanlommel, P.; Robbrecht, E.; Cugnon, P.; Clette, F.; Wauters, L.; Zhukov, A. Bibcode: 2004cosp...35.2781V Altcode: 2004cosp.meet.2781V Originally founded in 1981 as the World Data Centre for the Sunspot Index, the SIDC (Solar Influences Data analysis Centre) shifted to a higher gear in 2000, when it became a Regional Warning Centre of the ISES (taking over this activity from Meudon). The obvious link between space weather and solar activity - a prime research topic of the solar physics department of the Royal Observatory of Belgium - and the equally obvious relevance of continuous long-term monitoring of solar activity have made the SIDC well-placed to embark on this new future. Thanks to becoming one of the Service Development Activities in the Space Weather Applications Pilot Project recently set up by ESA, the SIDC has been able to further improve and expand these activities. In this paper we discuss some of the new tools, models and data that have been or will be developed to this purpose. It will also be detailed how the scientific and operational involvement of the Royal Observatory of Belgium in many future space missions oriented towards solar physics and solar monitoring will help the SIDC become an independent European space weather monitoring and forecasting centre. Title: Intensity Variations in EIT Shutterless Mode: Waves or Flows? Authors: de Groof, A.; Berghmans, D.; van Driel-Gesztelyi, L.; Poedts, S. Bibcode: 2004ESASP.547..245D Altcode: 2004soho...13..245D On 11 July 2001 an EIT shutterless campaign was conducted which provided 120 high-cadence (68s) 304 Å images of the north eastern quarter of the Sun. The most interesting feature seen in the data is an off-limb half loop structure along which systematic intensity variations appear to propagate from the top of the loop towards its footpoint. We investigate the underlying cause of these propagating disturbances, i.e. whether they are caused by waves or by plasma flows. First we identify 7 blobs with the highest intensities and follow them along the loop. By means of a location-time plot, bulk velocities can be measured at several locations along the loop. The velocity curve found this way is then compared with characteristic wave speeds and with the free-fall speed in order to deduce the nature of the intensity variations. Additional information is derived by measuring the relative intensity enhancements and comparing the EIT 304 Å sequence with Big Bear and 171 Å data. The idea of slow magneto-acoustic waves is rejected, and we find several arguments supporting that these intensity variations are due to flowing/falling plasma blobs. Title: Objective CME detection over the solar cycle Authors: Robbrecht, E.; Berghmans, D. Bibcode: 2004cosp...35.2702R Altcode: 2004cosp.meet.2702R We have developed a software package for 'Computer Aided CME Tracking' (CACTus), that autonomously detects CMEs in image sequences from LASCO. The crux of the CACTus software is the detection of CMEs as bright ridges in [height, time] maps using the Hough transform. The output is a list of events, similar to the classic catalogs, with principle angle, angular width and velocity estimation for each CME. In contrast to catalogs assembled by human operators, these CME detections by software can be faster and possibly also more objective, as the detection criterion is written explicitly in a program. Especially on the timescale of a solar cycle, it is questionnable whether human, visual CME detection is stable, as the operator gains experience or personnel is replaced. In this paper we overview the latest improvements of CACTUS and validate its performance by comparing the CACTus output with the classical, visually assembled CME catalogs. Discrepancies between the classical catalogs and the CACTUS catalogs are discussed. Such discrepancies highlight not only the performance of CACTUS but also the caveats of the classical catalogs. Indeed, CACTUS sometimes finds CMEs that are not listed in the catalogs or interpreted differently (eg halo CME or not). It is important to know these caveats when using the CME catalogs as input for statistical CME studies over the solar cycle. The near realtime output of the software is available on the web(http://sidc.oma.be/cactus) and is updated daily. Title: SWAP onboard PROBA-2, a new EUV imager for solar monitoring Authors: Berghmans, D.; Swap Consortium Bibcode: 2004cosp...35.2747B Altcode: 2004cosp.meet.2747B SWAP (Sun Watcher using Active Pixel System detector and Image Processing) is a solar EUV imager that has been selected to fly in 2006 on the PROBA-2 technological platform, an ESA program. SWAP will use an off-axis Ritchey Chretien telescope equipped with a specifically EUV enhanced CMOS APS detector. This type of detector has advantages that promise to be very profitable for solar EUV imaging. SWAP will provide solar corona images in the Fe XII line (19.5 nm) on a baselined 1-min cadence. Observations with this specific wavelength allow detecting phenomena, such as solar flares or EIT-waves, associated with the early phase of coronal mass ejections. Image recognition software will be developed that automatically detects these phenomena and sends out space weather warnings. Together with its sister instrument LYRA (Lyman-alpha Radiometer) onboard PROBA-2, SWAP will serve as a high performance solar monitoring tool to be used in operational space weather forecasting. The SWAP data will complement the observations provided by SOHO-EIT, and STEREO-SECCHI. Title: Extracting the apparent motion from two successive EIT images Authors: Gissot, Samuel F.; Hochedez, J. -F.; Dibos, F.; Brajša, R.; Jacques, L.; Berghmans, D.; Zhukov, A.; Clette, F.; Wöhl, H.; Antoine, J. -P. Bibcode: 2003ESASP.535..853G Altcode: 2003iscs.symp..853G The EIT observations cover more than seven years of the 23rd solar cycle. The main synoptic dataset, usually refered to as the "CME Watch", is a nearly uninterrupted sequence of images taken in the Fe XII bandpass at a cadence of four images per hour. In this work we study motion tracking methods in order to estimate displacements from frame to frame. We have implemented a novel optical flow algorithm, and tested it on a couple of successive images. We have linked the apparent motion occurring between two frames to the expected rotation rate. On this short time scale (20 minutes), we are able to retrieve the global parameters of the solar differential rotation. A strategy for the extraction of region with reliable motion will be discussed. Title: MAGRITTE / SPECTRE : the Solar Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory Authors: Rochus, P.; Defise, J. M.; Halain, J. P.; Mazy, E.; Jamar, C.; Clette, F.; Cugnon, P.; Berghmans, D.; Hochedez, J. F.; Delaboudiniere, J. P.; Artzner, G.; Auchere, F.; Mercier, R.; Ravet, M. F.; Delmotte, M.; Idir, M.; Fineschi, S.; Antonucci, E.; Harrison, R. A.; Howard, R. A.; Moses, J. D.; Newmark, J. S. Bibcode: 2002AGUFMSH21C..05R Altcode: The Solar Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory will characterize the dynamical evolution of the solar plasma from the chromosphere to the corona, and will follow the connection of plasma dynamics with magnetic activity throughout the solar atmosphere. The AIA consists of 7 high resolution imaging telescopes in the following spectral bandpasses: 1215 \x8F Ly-a, 304 \x8F He II, 629 \x8F OV, 465 \x8F Ne VII, 195 \x8F Fe XII (includes Fe XXIV), 284 \x8F Fe XV, and 335 \x8F Fe XVI. The telescopes are grouped by instrumental approach: the Magritte Filtergraphs (R. Magritte, famous 20th Century Belgian Surrealistic Artist), five multilayer EUV channels with bandpasses ranging from 195 to 1216 \x8F, and the SPECTRE Spectroheliograph with one soft-EUV channel at OV 629 \x8F. They will be simultaneously operated with a 10-second imaging cadence. These two instruments, the electronic boxes and two redundant Guide Telescopes (GT) constitute the AIA suite. They will be mounted and coaligned on a dedicated common optical bench. The GTs will provide pointing jitter information to the whole SHARPP assembly. This poster presents the selected technologies, the different challenges, the trade-offs to be made in phase A, and the model philosophy. From a scientific viewpoint, the unique combination high temporal and spatial resolutions with the simultaneous multi-channel capability will allow Magritte/SPECTRE to explore new domains in the dynamics of the solar atmosphere, in particular the fast small-scale phenomena. We show how the spectral channels of the different instruments were derived to fulfill the AIA scientific objectives, and we outline how this imager array will address key science issues, like the transition region and coronal waves or flare precursors, in coordination with other SDO experiments. We finally describe the real-time solar monitoring products that will be made available for space-weather forecasting applications. Title: The Solar Influences Data Analysis Center: current status of expanding activities Authors: Clette, F.; van der Linden, R.; Cugnon, P.; Berghmans, D.; Foullon, C.; Wouters, L.; Verwichte, E.; Hochedez, J. -F.; Vanlommel, P. Bibcode: 2002ESASP.506..125C Altcode: 2002ESPM...10..125C; 2002svco.conf..125C Over the last 24 months, the activities of the SIDC, which is the European Regional Warning Center of the ISES, have steadily expanded. A 7-day/week service has been implemented, the SIDC Web interface has been reworked and expanded and the number of registered users increased further. New image data have been added, including new photospheric and chromospheric CCD images from the Uccle Station. We summarize here the new services provided to the community and some statistics about the success rate of our forecasts. We also outline the orientations of the future SIDC development. Title: Getting hot by nanoflares Authors: Berghmans, David Bibcode: 2002ESASP.506..501B Altcode: 2002svco.conf..501B; 2002ESPM...10..501B We review the current status of the 'Parker hypothesis' which suggests that the solar corona is heated by a multitude of small flare-like events called nanoflares. Space-borne coronal imagers such as SXT, EIT or TRACE have allowed to test Parker's hypothesis observationally. Combining the results from different authors it seems that we are close to falsifying the hypothesis, i.e. there are not enough nanoflares to heat the corona. The only remaining hope for nanoflare-adepts is the transition region which contains various types of impulsive events such as explosive events or blinkers whose role and mutual relation is not sufficiently understood yet to make a final verdict on Parker's hypothesis. Title: Automated detection of CMEs Authors: Berghmans, D. Bibcode: 2002ESASP.506...85B Altcode: 2002ESPM...10...85B; 2002svco.conf...85B We have developed a shoftware package for 'Computer Aided CME Tracking' (CACTus), that autonomously detects CMEs in image sequences from LASCO. The crux of the CACTus software is the detection of CMEs as bright ridges in [height, time] maps using the Hough transform. The output is a list of events, similar to the classic catalogs, with principle angle, angular width and velocity estimation for each CME. In contrast to catalogs assembled by human operators, these CME detections by software can be faster and possibly also more objective, as the detection criterion is written explicitly in a program. In this paper we discuss two applications of the software. In a first application, we validate the performance by comparing the CACTus output with the classical, visually assembled CME catalogs. We discuss its present success rate (about 75%) and prospects for improvement. By giving an example we show that the software can also reveal CMEs that have been not been listed in the catalogs. Such unreported cases might be of influence on CME stastistics and prove that also the present catalogs do not have a 100% success rate. The second application, is an operational version of CACTus that scans in real time, the last available LASCO images for recent CMEs. Title: The new instrumentation of the SIDC/Uccle station Authors: Clette, F.; Cugnon, P.; Berghmans, D.; van der Linden, R.; Wauters, L. Bibcode: 2002ESASP.506..935C Altcode: 2002svco.conf..935C; 2002ESPM...10..935C New digital 1K×1K CCD cameras have been installed on the solar telescope of the Royal Observatory of Belgium (ROB, Uccle, Brussels), in addition to the visual telescope used for the classical sunspot observations. One camera provides full-disk images of the photosphere and uses an image-selection algorithm to compensate the effects of the seeing. The other camera produces full-disk images of the chromosphere in the Hα line, and will be used for an automated flare patrol work. After completion of the instrument commissioning (August 2002), those images will be made available in near real-time through the SIDC Regional Warning Center web pages (http://sidc.oma.be) and in the form of a FITS file archive. We describe here the instruments and their capabilities. Title: Automated detection of CMEs in LASCO data Authors: Berghmans, D.; Foing, B. H.; Fleck, B. Bibcode: 2002ESASP.508..437B Altcode: 2002soho...11..437B We have developed software that autonomously detects CMEs in image sequences from LASCO. the crux of the software is the detection of CMEs as bright ridges in (height, time) maps using the Hough transform. The output is a list of events, similar to the classic catalogs, with principle angle, angular width and velocity estimation for each CME. In contrast to catalogs assembled by human operators, these CME detections by software can be faster, which is especially important in the context of space weather, and possibly also more objective, as the detection criterion is written explicitly in a program. In this paper we describe the software and validate its performance by comparing its output with the visually assembled CME catalogs. We discuss its present success rate (about 75%) and prospects for improvement. Finally, we show that the software can also reveal CMEs that have not been listed in the catalogs. Such unreported cases might be of influence on CME statistics and prove that also the present catalogs do not have a 100% success rate. Title: Space weather Authors: Glover, Alexi; Daly, Eamonn; Hilgers, Alain; Berghmans, David Bibcode: 2002EuRv...10..249G Altcode: Space weather is caused by conditions on the Sun and in the solar wind, the magnetosphere, ionosphere and thermosphere that can influence the performance and reliability of space-borne and ground-based technological systems and can affect human life or health. It affects man-made systems such as satellite electronics, terrestrial power grids and radio communications. This paper provides an overview of how space weather arises in the solar terrestrial system and how physical processes are able to cause space weather effects. We also discuss European perspectives and activities geared towards the possible initiation of a European Space Weather programme. Title: Multiscale activity observed by EIT/SoHO Authors: Hochedez, J. -F.; Jacques, L.; Verwichte, E.; Berghmans, D.; Wauters, L.; Clette, F.; Cugnon, P. Bibcode: 2002ESASP.477..115H Altcode: 2002scsw.conf..115H The Extreme ultraviolet Imaging Telescope (EIT) of SoHO provides a high-resolution and large sampling of the solar corona in time, space and brightness. To extract the wealth of its physics, it is valuable to adopt a multiscale approach. The Mexican Hat (MH) Continuous Wavelet Transform (CWT) is used for the first time to derive statistically the distribution of scales over 4 Mm. The global behaviour of the small scales offers a powerful way to monitor coronal activity. This is demonstrated with the May 1998 "CME Watch" data. This benefit is of space weather relevance and could improve forecasting of the solar activity. Title: The solar influences data analysis centre Authors: Berghmans, D.; Clette, F.; Cugnon, P.; Gabryl, J. -R.; Hochedez, J. -F.; Van der Linden, R. A. M.; Verwichte, E. Bibcode: 2002JASTP..64..757B Altcode: 2002JATP...64..757B Since 1981, the Royal Observatory of Belgium has operated the Sunspot Index Data Centre, the World Data Centre for the Sunspot Index. Recently, the Space Weather Forecast Centre of Paris-Meudon was transferred and added to the activities of the SIDC. Moreover, a complete archive of all images of the SOHO instrument EIT has become available at the SIDC. Given all these extensions, the new style SIDC has become a `Solar Influences Data Centre' that analyses solar activity and provides services on three different time scales: 1. Fast warnings and real time monitoring. As the Regional Warning Centre (RWC) for Western Europe of the International Space Environment Service (ISES), the SIDC collects and redistributes solar, geomagnetic, and ionospheric data in Western Europe. Short-term predictions (3 days) and alerts are produced on a daily basis. 2. Forecasts and middle term analysis. The SIDC takes care of the calculation of a sunspot index, called the International Sunspot Number. We compute and broadcast the daily, monthly, yearly international sunspot numbers, with middle range predictions (up to 12 months). 3. Post-event analysis and long-term solar cycle analysis. Since the launch of SOHO, EIT offers a global view of the EUV corona over the whole rising phase of the solar activity cycle. Such a long-duration data series is unprecedented and allows the study of the evolution over the solar cycle of objects classes such as active regions, coronal holes, coronal mass ejections or flares. Title: Slow magneto-acoustic waves in coronal loops Authors: Verwichte, E.; Nakariakov, V. M.; Berghmans, D.; Hochedez, J. -F. Bibcode: 2001ESASP.493..395V Altcode: 2001sefs.work..395V No abstract at ADS Title: Slow magnetoacoustic waves in coronal loops: EIT and TRACE Authors: Robbrecht, E.; Verwichte, E.; Berghmans, D.; Hochedez, J. F.; Poedts, S.; Nakariakov, V. M. Bibcode: 2001A&A...370..591R Altcode: On May 13, 1998 the EIT (Extreme ultraviolet Imaging Telescope) on board of SoHO (Solar and Heliospheric Observatory) and TRACE (Transition Region And Coronal Explorer) instruments produced simultaneous high cadence image sequences of the same active region (AR 8218). TRACE achieved a 25 s cadence in the Fe Ix (171 Å) bandpass while EIT achieved a 15 s cadence (operating in ``shutterless mode'', SoHO JOP 80) in the Fe Xii (195 Å) bandpass. These high cadence observations in two complementary wavelengths have revealed the existence of weak transient disturbances in an extended coronal loop system. These propagating disturbances (PDs) seem to be a common phenomenon in this part of the active region. The disturbances originate from small scale brightenings at the footpoints of the loops and propagate along the loops. The projected propagation speeds roughly vary between 65 and 150 km s-1 for both instruments which is close to and below the expected sound speed in the coronal loops. The measured slow magnetoacoustic propagation speeds seem to suggest that the transients are sound (or slow) wave disturbances. This work differs from previous studies in the sense that it is based on a multi-wavelength observation of an entire loop bundle at high cadence by two EUV imagers. The observation of sound waves along the same path shows that they propagate along the same loop, suggesting that loops contain sharp temperature gradients and consist of either concentric shells or thin loop threads, at different temperatures. Title: Active region transient brightenings. A simultaneous view by SXT, EIT and TRACE Authors: Berghmans, D.; McKenzie, D.; Clette, F. Bibcode: 2001A&A...369..291B Altcode: This paper reports on a qualitative study on the weakest flarelike brightenings in active region that can be observed with current coronal imagers. Specificallly, we investigate the correspondence of the ``active region transient brightenings'' (ARTB) first observed almost a decade ago with SXT with similar brightenings in the EUV that are now observed by EIT and TRACE. For this goal, exceptionally high cadence image sequences were acquired of a small but rapidly evolving active region (NOAA 8218), simultaneously by SXT, EIT, and TRACE. Within the timeframe of this coordinated campaign, we detected 41 soft X-ray brightenings and 373 EUV brightenings. We find that the strongest brightenings observed by EIT are indeed the EUV counterparts of the ARTBs seen by SXT. Weaker brightenings seen by EIT often do not have an X-ray counterpart. Among the brightenings detected with SXT we discover a new subpopulation, consisting of events that brighten in soft X-rays only, at a footpoint of a pre-existing SXT loop shortly after an ARTB occurred at the other footpoint. The propagation speed of the perturbation suggests an interpretation in terms of slow mode MHD waves. Title: Long Term Variations in the Extreme UV Corona: the EIT/SoHO perspective Authors: Hochedez, J. -F.; Clette, F.; Verwichte, E.; Berghmans, D.; Cugnon, P. Bibcode: 2001IAUS..203..501H Altcode: Since the start of the SOHO mission, EIT offered a global view of the extreme ultraviolet corona constinuously over the whole rising phase of the solar activity cycle. Such a long-duration data serie is unprecedented. We present here the current results of an ongoing investigation of the entire EIT data set. In this process, numerous classes of magnetic regions of all sizes (active regions, coronal holes, bright points, plumes, transition region network, filaments) as well as many different classes of dynamic events (CME's, flares, jets, blinkers, macrospicules) will be identified in EIT images made in its four bandpasses. The changes in the class properties (location, size, area, topology, lifetime, integrated flux) or in the relationship between different object classes can then be monitored over the fast rise of magnetic activity towards the current maximum. We describe here the image processing techniques developed for this search as well as early results. Title: Slow magnetoacoustic waves in coronal loops Authors: Nakariakov, V. M.; Verwichte, E.; Berghmans, D.; Robbrecht, E. Bibcode: 2000A&A...362.1151N Altcode: A theoretical model interpreting propagating disturbances of EUV emission intensity, recently observed in coronal loops, is constructed in terms of slow magnetoacoustic waves. The model is one-dimensional and incorporates effects of nonlinearity, dissipation due to finite viscosity and thermal conduction, and gravitational stratification of plasma in the loop. It has been found that, for the observationally detected parameters of the waves, the main factors influencing the wave evolution are dissipation and stratification. The upwardly propagating waves of observed periods (5-20 min) are found to decay significantly in the vicinity of the loop apex, explaining the rarity of observational detection of downwardly propagating waves. The model provides a theoretical basis for development of MHD seismology of the coronal loops. Title: Slow magnetoacoustic waves in coronal loops: EIT vs TRACE Authors: Robbrecht, E.; Verwichte, E.; Berghmans, D.; Hochedez, J. F.; Poedts, S. Bibcode: 2000AIPC..537..271R Altcode: 2000wdss.conf..271R On May 13, 1998 the EIT (Extreme-Ultraviolet Imaging Telescope) and TRACE (Transition Region And Coronal Explorer) instruments produced simultaneous high cadence image sequences of the same active region (AR 8218). TRACE achieved a 25 sec cadence in the Fe IX/X (171 Å) bandpass while EIT achieved a 15 sec cadence (operating in `shutterless mode,' SOHO JOP 80) in the Fe XII (195 Å) bandpass. These high cadence observations in two complementary wavelengths have revealed the existence of weak transient disturbances in an extended coronal loop system. These propagating disturbances (PDs) seem to be a common phenomenon in this part of the active region. The disturbances originate from small scale brightenings at the footpoints of the loops and propagate along the loops. The apparent propagation speeds roughly vary between 65 and 150 km s-1 which is close to the expected sound speed of the coronal loops. The measured propagation speeds seem to suggest that the transients are sound (or slow) wave disturbances. . Title: Observations of solar wave/instability phenomena as imaged by EIT/SOHO, TRACE and Yohkoh/SXT Authors: Berghmans, D.; McKenzie, D. Bibcode: 2000AIPC..537..168B Altcode: 2000wdss.conf..168B On May 13 1998, active region NOAA 8218 was observed in the context of the SOHO/JOP80 campaign by an array of 8 different ground-based and space-born instruments. The emphasis was set on imaging of small-scale dynamics in this relatively small but rapidly evolving AR. In particular, SOHO/EIT (195 Å), TRACE (171 Å) and YOHKOH/SXT produced subfield image sequences at their respective highest possible rates. We searched for wave and instability phenomena by using an automated recognition scheme. This result in a wide inventory of propagating disturbances and localized transient brightenings. By comparing the soft X-ray signature as recorded by SXT with the EUV-signature as collected by EIT and TRACE, we are able to distinguish between various types of active region transients. As such we find that the strongest brightenings observed by EIT are indeed the EUV counterparts of the previously reported ARTBs seen by SXT. Weaker brightenings seen by EIT do often not have an X-ray counterpart. Moreover, in an extended system of faint quasi-open loops, we find propagating disturbances, with speeds of the order of 100 km/s, both in EIT and TRACE images. These are interpreted as sonic perturbations. The brightenings will be discussed in this paper while the propagating disturbances are described in the presentation by Eva Robbrecht at this conference. . Title: Mid-Term Variations in the Extreme UV Corona: the EIT/SOHO Perspective Authors: Hochedez, J. F.; Clette, Frederic; Verwichte, Erwin; Berghmans, David; Cugnon, Pierre Bibcode: 2000ESASP.463...79H Altcode: 2000sctc.proc...79H No abstract at ADS Title: Multi-Imager Study of Transients and Propagating Disturbances in Active Region Loops (SOHO JOP80 Campaign) Authors: Berghmans, D.; Clette, F.; Robbrecht, E.; McKenzie, D. Bibcode: 1999ESASP.448..575B Altcode: 1999ESPM....9..575B; 1999mfsp.conf..575B No abstract at ADS Title: Slow Magnetoacoustic Waves in Coronal Loops? Authors: Robbrecht, E.; Berghmans, D.; Nakariakov, V.; Poedts, S. Bibcode: 1999ESASP.446..575R Altcode: 1999soho....8..575R On May 13, 1998 the EIT and TRACE instruments produced simultaneous high cadence image sequences of the same active region (AR 8218). TRACE achieved a 25 sec cadence in the 171 deg passband while EIT achieved a 15 sec cadence (operating in 'shutterless mode', SOHO JOP 80) in the 195 deg passband. These high cadence observations in two complementary wavelengths have revealed the existence of weak disturbances in an extended coronal loop system. The disturbances originate from small scale brightenings at the footpoints of the loops and propagate along the loops at an apparant speed of the order of 150 km/s which is close to the expected sound speed. To conclude whether these propagating disturbances should be interpreted as slow magnetoacoustic waves or as mass motions ('microflows'), we compare our observational findings with theoretical models. Our results suggest that the recent discovery of DeForest and Gurman (1998) of slow MHD waves in polar plumes, are in fact not typical of polar plumes but occur also in extended coronal structures elsewhere. Title: Active Region Transient Brightenings : EIT Versus SXT Authors: Berghmans, D.; McKenzie, D.; Clette, F. Bibcode: 1999ESASP.446..173B Altcode: 1999soho....8..173B On May 13, 1998, the Extreme-Ultraviolet Imaging Telescope (EIT, on board SOHO) has produced a unique image sequence operating in 'shutterless mode' (SOHO JOP 80). In JOP 80, EIT is the leading instrument, followed by several space born instruments (SXT, TRACE, MDI, CDS, SUMER), as well as two observatories on the ground (in La Palma and Sac Peak). The target of the campaign was a relatively small but rapidly evolving active region (AR 8218). For the EIT contribution, a 15 s cadence was achieved in the Fe XII bandpass at 195 deg by leaving EIT's shutter open for 1 hour and operating the CCD in frame transfer mode. We have started the analysis of the huge data set, by making an inventory of the transients observed in the EIT image sequence. These transients range from a B3.5 flare producing a large plasma flow along pre-existing loops, to smaller EUV brightenings of active region loops. In addition, a new class of weaker footpoint brightenings was discovered that produce wave-like disturbances propagating along quasi-open field lines (see the presentation by Eva Robbrecht at this workshop). In this paper we take the opportunity provided by JOP 80, to investigate the correspondence of the transient brightenings observed by EIT in this active region, with the ARTB previously observed by SXT and studied by Shimizu (1992). Within the simultaneous high cadence SOHO JOP 80 image sequences, both EIT and SXT accummulated a few tens of brightening events. At the time of the writing of this abstract, we can say that most of the SXT events have indeed 1 or more EIT counterparts. Typically the SXT events are somewhat bigger than the EIT events where the latter are ussualy located toward the point of origin of the SXT events. Whereas a few brightenings exist in one dataset without any trace in the other dataset (in both directions), we have additionally for a few brightenings in the SXT data, a corresponding EIT darkening as if the plasma is suddenly heated and dissappears from the EIT passband. Title: EIT Micro-Variability Studies : Preliminary Results from the SOHO JOP 80 Campaign Authors: Clette, F.; Berghmans, D. Bibcode: 1999ASPC..184..217C Altcode: The first results from the high-cadence imaging campaign run in May 98, by several space-based instruments with ground support (SOHO JOP80), are presented. General properties and scaling laws are deduced for a fairly large sample of small-amplitude short-lived impulsive brightenings occuring locally in active region loops. From these, we derive some conclusions about similarities with soft-X ray microflares. Several classes of minor transients are distinguished, such as loop-like and twin brightenings. We find also evidence for propagating compressive waves in extended field lines rooted near one magnetic pole of the active region. This study provides a first inventory of small-scale variabilities in view of the full analysis of this huge and rich data set. Title: Active region EUV transient brightenings - First Results by EIT of SOHO JOP 80 Authors: Berghmans, D.; Clette, F. Bibcode: 1999SoPh..186..207B Altcode: On 13 May 1998, the Extreme-Ultraviolet Imaging Telescope (EIT, on board SOHO) has produced a unique image sequence operating in 'shutterless mode' (SOHO JOP 80). In JOP 80, EIT is the lead instrument, followed by several space-born instruments (SXT, TRACE, MDI, CDS, SUMER), as well as two observatories on the ground (in La Palma and Sac Peak). The target of the campaign was a relatively small but rapidly evolving active region (AR 8218). For the EIT contribution, a 15 s cadence was achieved in the Fe xii bandpass at 195 Å by leaving EIT's shutter open for 1 h and operating the CCD in frame-transfer mode. In this paper, we start the analysis of the huge data set, by making an inventory of the transients observed in the EIT image sequence. Besides scatter plots of duration, size and radiative output of the detected EUV brightenings, we discuss in full detail the morphology and evolution of several typical events. These transients range from a B3.5 flare producing a large plasma flow along pre-existing loops, to EUV versions of active region transient brightenings as previously observed by SXT on board Yohkoh. In addition, a new class of weaker footpoint brightenings is discussed that produce wave-like disturbances propagating along quasi-open field lines. This new class of propagating disturbances extends the wide variety of transient phenomena that we discovered in the EIT data, and makes the potential for inter-instrumental studies of the JOP 80 data all the more exciting. We stress the necessity of such forthcoming studies to reach an instrument-independent classification of small-scale solar transients. Title: Quiet Sun EUV transient brightenings and turbulence. A panoramic view by EIT on board SOHO Authors: Berghmans, D.; Clette, F.; Moses, D. Bibcode: 1998A&A...336.1039B Altcode: Since January 1996, the Extreme-Ultraviolet Imaging Telescope (EIT, onboard SOHO) has produced unique image sequences covering a wide field of view with a high temporal resolution, in the He Ii transition region line and in several Fe coronal emission lines. Using two sequences acquired with cadences of the order of one minute and with durations ranging from one hour to several hours, we analyse the dynamical properties of the transition region and corona. We find evidence of turbulence both in spatial and in temporal power spectra suggesting that the plasma of the quiet solar atmosphere is in a permanent state of turbulence. As predicted by numerical simulations, this turbulence has an highly intermittent nature. We find an unexpectedly large number of small-scale brightenings. The coronal brightenings are identified as the low energy counterparts of ``X-ray network flares'' observed with SXT on board Yohkoh. The thousands of brightenings observed by EIT in the transition region include many that are similar to ``blinkers'' observed with CDS, though we find a larger variety. Thanks to EIT's wide spatial coverage, we can perform a large scale statistical study, complementing spectroscopic studies which give access to only a very small subsample of events. We present occurrence distributions of duration, size and radiative output of the brightenings as well as various correlations between these parameters. The energy injected by the brightenings into the solar atmosphere is insufficient to be in itself responsible for coronal heating. We discuss the importance of the ubiquitous small brightenings as perhaps the most visible aspect of yet undetected heating events higher up in the quiet corona. Title: Impulsive Coronal Dynamics as Revealed by EIT Authors: Clette, F.; Berghmans, D. Bibcode: 1998ASPC..155..356C Altcode: 1998sasp.conf..356C No abstract at ADS Title: Quiet Sun EUV Transient Brightenings and Turbulence Authors: Berghmans, D.; Clette, F.; Moses, D. Bibcode: 1998ESASP.417..229B Altcode: 1998cesh.conf..229B No abstract at ADS Title: EIT Observations of Small-Scale Dynamics in the Transition Region and Corona Authors: Clette, F.; Berghmans, D. Bibcode: 1997ESASP.415...95C Altcode: 1997cpsh.conf...95C No abstract at ADS Title: EIT Observations of the Extreme Ultraviolet Sun Authors: Moses, D.; Clette, F.; Delaboudinière, J. -P.; Artzner, G. E.; Bougnet, M.; Brunaud, J.; Carabetian, C.; Gabriel, A. H.; Hochedez, J. F.; Millier, F.; Song, X. Y.; Au, B.; Dere, K. P.; Howard, R. A.; Kreplin, R.; Michels, D. J.; Defise, J. M.; Jamar, C.; Rochus, P.; Chauvineau, J. P.; Marioge, J. P.; Catura, R. C.; Lemen, J. R.; Shing, L.; Stern, R. A.; Gurman, J. B.; Neupert, W. M.; Newmark, J.; Thompson, B.; Maucherat, A.; Portier-Fozzani, F.; Berghmans, D.; Cugnon, P.; Van Dessel, E. L.; Gabryl, J. R. Bibcode: 1997SoPh..175..571M Altcode: The Extreme Ultraviolet Imaging Telescope (EIT) on board the SOHO spacecraft has been operational since 2 January 1996. EIT observes the Sun over a 45 x 45 arc min field of view in four emission line groups: Feix, x, Fexii, Fexv, and Heii. A post-launch determination of the instrument flatfield, the instrument scattering function, and the instrument aging were necessary for the reduction and analysis of the data. The observed structures and their evolution in each of the four EUV bandpasses are characteristic of the peak emission temperature of the line(s) chosen for that bandpass. Reports on the initial results of a variety of analysis projects demonstrate the range of investigations now underway: EIT provides new observations of the corona in the temperature range of 1 to 2 MK. Temperature studies of the large-scale coronal features extend previous coronagraph work with low-noise temperature maps. Temperatures of radial, extended, plume-like structures in both the polar coronal hole and in a low latitude decaying active region were found to be cooler than the surrounding material. Active region loops were investigated in detail and found to be isothermal for the low loops but hottest at the loop tops for the large loops. Title: Wave heating of coronal loops driven by azimuthally polarised footpoint motions. I. Stationary behaviour in dissipative MHD. Authors: Berghmans, D.; Tirry, W. J. Bibcode: 1997A&A...325..318B Altcode: We study the heating of coronal loops by linear resonant Alfven waves that are excited by photospheric footpoint motions of the magnetic field lines. The analysis is restricted to azimuthally polarised footpoint motions so that Alfven waves are excited. At the radii where Alfven waves, travelling back and forth along the loop, are in phase with the footpoint motions the oscillations grow unbounded in ideal MHD. Inclusion of dissipation prevents singular growth and we can look at the steady state in which the energy input at the photosphere is balanced by the energy dissipated at the resonance. The crux of our study is that the azimuthal wave number is taken non-zero which means that also fast waves, including quasi-modes, can be excited by the purely azimuthally polarised footpoint motions. In this case resonant Alfven waves are not only excited directly by the footpoint motions but also indirectly through coupling to fast waves. For some footpoint motions these contributions counteract each other leading to virtually no heating (anti-resonance) while for values corresponding to a quasi-mode the two contributions act in concert leading to enhanced heating. This dramatic influence of the quasi-mode is unexpected since, in contrast to a sideways driven loop, a loop driven at the footpoints by azimuthally polarised footpoint motions does not need quasi-modes as energy carrier waves. In this paper a stationary state is assumed which allows us to determine the optimal footpoint characteristics for heating, but does not give any information on the time scales involved. This item is adressed in a companion paper where an identical system is studied time dependently using ideal MHD. This twin study investigates the attainability of the heating scenarios and provides an enhanced insight in the results of the present paper. Title: Wave heating of coronal loops driven by azimuthally polarised footpoint motions. II. The time-dependent behaviour in ideal MHD. Authors: Tirry, W. J.; Berghmans, D. Bibcode: 1997A&A...325..329T Altcode: We study the heating of coronal loops by linear resonant Alfven waves that are excited by photospheric footpoint motions of the magnetic field lines. The analysis is restricted to azimuthally polarised footpoint motions so that Alfven waves are excited directly. At the radii where Alfven waves, travelling back and forth along the length of the loop, are in phase with the footpoint motions, the oscillations grow unbounded in ideal MHD. In the companion paper (Paper I) dissipation is included and we looked at the steady state in which the energy injected at the photospheric part of the loop is balanced by the energy dissipated in the dissipative layer around the resonance. In this paper we make an analysis in time-dependent ideal linear MHD in order to get more physical insight in the results of Paper I and to get information about the time scales involved. In the present study the azimuthal wave number is taken to be non-zero so that Alfven and fast wave do not exist independently. In this case the heating in the resonance layer becomes a complicated interplay of the influence of the Alfven waves excited directly at the photospheric base of the resonant layer and the influence of the quasi-modes excited indirectly. We find that the presence of these quasi-modes influence the resonance development dramatically. This is unexpected, since in contrast to a sideways driven loop, a loop driven at the footpoints by azimuthally footpoint motions does not need quasi-modes as energy carrier waves. Title: Temporal evolution of resonant absorption in coronal loops. Excitation by footpoint motions normal to the magnetic surfaces. Authors: Tirry, W. J.; Berghmans, D.; Goossens, M. Bibcode: 1997A&A...322..329T Altcode: In this paper we study the temporal evolution of linear MHD waves excited by footpoint motions using an ideal, pressureless slab model for coronal loops. We choose the footpoint motions to be polarised normal to the magnetic flux surfaces such that only fast waves are driven directly, including the so-called quasi-modes. We have derived a formal analytical solution as a superposition of eigenmodes describing the system as a function of time. The corresponding eigenvalue problem is solved numerically. This enables us to study the influence of the characteristics of the footpoint motion on the excitation of the quasi-modes. On the magnetic flux surface where the frequency of these quasi-modes equals the local Alfven frequency, wave energy is transferred from the quasi-modes towards Alfven waves. We investigate the time evolution of this process in which small scale dissipative features are generated which can be relevant in the context of coronal heating. Special attention is given to the question whether this generation of small scale dissipative features takes place on time scales shorter than typical life times of coronal loops. Expressing the dissipation time scale as function of the length scale corresponding to the resonances, an estimate for the time when dissipation becomes important and when our ideal MHD simulation stops to be valid, can be derived. For typical dissipation coefficients and length scales, dissipation becomes important in the resonance layer in a time comparable to the life time of coronal loops. Title: Direct excitation of resonant torsional Alfven waves by footpoint motions. Authors: Ruderman, M. S.; Berghmans, D.; Goossens, M.; Poedts, S. Bibcode: 1997A&A...320..305R Altcode: The present paper studies the heating of coronal loops by linear resonant Alfven waves that are excited by the motions of the photospheric footpoints of the magnetic field lines. The analysis is restricted to torsionally polarised footpoint motions in an axially symmetric system so that only torsional Alfven waves are excited. For this subclass of footpoint motions, the Alfven and cusp singularities are absent from the analysis which means that resonant coupling between global modes of the loop and localised oscillations is avoided. Instead, the focus is on the resonances due to the finite extent of the loop in the longitudinal direction: at the radii where Alfven waves travelling back and forth along the length of the loop are in phase with the footpoint motions, the oscillations grow unbounded in ideal MHD. Inclusion of electrical resistivity and viscosity as dissipation mechanisms prevents singular growth and we can look at the steady state in which the energy injected at the photospheric part of the loop is balanced by the energy dissipated at the dissipative layer around the resonance. In this sense, we show that the direct excitation of Alfven waves by torsionally polarised footpoint motions leads to a very efficient heating mechanism for coronal loops, even without resonant coupling to global modes. Title: Heating of Coronal Loops by MHD Waves Driven by Photospheric Motions Authors: Berghmans, D. Bibcode: 1997ESASP.404..199B Altcode: 1997cswn.conf..199B No abstract at ADS Title: Wave and Small-Scale Dynamics Study Using High-Cadence EIT Image Sequences Authors: Clette, F.; Berghmans, D. Bibcode: 1997ESASP.404..283C Altcode: 1997cswn.conf..283C No abstract at ADS Title: MHD wave heating of coronal loops Authors: Poedts, S.; Tirry, W.; Berghmans, D.; Goossens, M. Bibcode: 1997jena.confE..54P Altcode: The possibility of heating coronal loops by phase-mixing and resonant absorption of MHD waves is discussed. The focus is on the efficiency and time scales of the conversion of the wave energy to heat for typical coronal loop parameter values. Both the sideways excitation of loops by incident waves and the footpoint driving by convective motions are discussed. First, the mechanisms of phase-mixing and resonant absorption are explained in a simple set-up. Next, linear MHD results on solar coronal loop applications are reviewed. In sideways excited loops (by incident waves), `quasi-modes' (or `collective modes') play the crucial role of energy carrier from the external region {through the flux surfaces} to the resonant layers. The quasi-modes are required to obtain a reasonable efficiency unless the resonances are located in the outer region of the loop. In footpoint driven loops, on the other hand, resonant Alfven can be excited directly and the efficiency depends of the polarization of the driving source. Recent results take the variation of plasma density and magnetic field strength {along the loop} into account. For typical coronal loop parameters, the MHD wave heating mechanism turns out to be very efficient, i.e. the coupling of the loop plasma to the external driver is very good and the time scales for dissipation are much smaller than the typical life time of a loop. However, the dynamics in the resonant layers is very nonlinear in the hot (very well conducting) coronal plasma. Computer simulations show that the shear flow in these layers can become unstable. It will be shown that the Kelvin-Helmholtz-like instabilities may destroy the resonant layers and lead to a turbulent state. Finally, some observational results and consequences are discussed. This brings us to the problems of the discrepancy between the observed and the required power spectrum of MHD waves and the distinction between different candidate heating mechanisms. Scientific visualization of the observational consequences of the computer simulated results may lead to different observable features for different candidate heating mechanisms and, hence, to the identification of the mechanism responsible for the heating of the coronal loops. Title: The role of the quasi-modes in the wave-heating of line-tied coronal loops Authors: Tirry, W.; Berghmans, D. Bibcode: 1997jena.confE..58T Altcode: We study the heating of coronal loops by linear resonant Alfven waves that are excited by photospheric footpoint motions of the magnetic field lines. For azimuthally polarised footpoint motions Alfven waves are excited directly. At the radii where Alfven waves, travelling back and forth along the loop, are in phase with the footpoint motions the oscillations grow unbounded in ideal MHD. However, inclusion of dissipation prevents singular growth and we can look at the steady state in which the energy input at the photosphere is balanced by the energy dissipated at the resonance. The crux of our study is that the azimuthal wave number is taken non-zero which means that also fast waves, including quasi-modes, can be excited by the purely azimuthally polarised footpoint motions. In this case resonant Alfven waves are not only excited directly by the footpoint motions but also indirectly through coupling to fast waves. For some footpoint motions these contributions counteract each other leading to virtually no heating (anti-resonance) while for parameter values corresponding to a quasi-mode the two contributions act in concert leading to enhanced heating. In a first study a steady state is assumed, which allows us to determine the optimal footpoint characteristics for heating. In order to get information on the time scales involved we studied the same coronal loop model using a time-dependent ideal approach. This approach also provides us with the physical insight in the phenomena of anti-resonances. Title: The Footpoint-driven Coronal Sausage Wave Authors: Berghmans, David; de Bruyne, Peter; Goossens, Marcel Bibcode: 1996ApJ...472..398B Altcode: We study the excitation of MHD waves in a coronal loop as its field line footpoints are forced to follow the photo spheric convective motions. By focussing on the specific case of cylindrically symmetric footpoint motions, the original problem is reduced to one in which fast waves and Alfvén waves are decoupled. This allows for a full analytical treatment of the photo spheric excitation of both sausage waves and of torsional Alfvén waves. Previously, Berghmans & De Bruyne considered the case of torsional Alfvén waves. In the present paper we extend that analysis to sausage waves that are excited by radially polarized footpoint motions (e.g., typical for granules). The time-dependent solution that we obtain is written as a superposition of body and leaky eigenmodes whose excitation is easily determined from the imposed footpoint motion. This provides analytical insight into the dynamics and energetics of both impulsively and periodically driven sausage waves. In each case, we explain the time evolution of the generated waves and discuss typical "signatures" that can be looked for in numerical simulations and possibly in solar observations. Title: Coronal Loop Oscillations Driven by Footpoint Motions: Analytical Results for a Model Problem Authors: Berghmans, D.; de Bruyne, P. Bibcode: 1996ApL&C..34..157B Altcode: No abstract at ADS Title: Coronal Loop Oscillations Driven by Footpoint Motions: Analytical Results for a Model Problem Authors: Berghmans, David; de Bruyne, Peter Bibcode: 1995ApJ...453..495B Altcode: We study the excitation of MHD waves in a coronal loop as its field-line footpoints are forced to follow the photospheric convective motions. Due to the large photo spheric-coronal density ratio, these waves are reflected back and forth in the loop and thus build up a global oscillation. By focusing on a specific case the problem is reduced to the simplest situation conceivable which still contains the relevant physics of wave propagation, reflections, resonances, and phase mixing. This model problem allows for a fully analytical treatment which greatly helps to understand earlier results found in the literature. It is shown that the classical asymptotic state assumption, in which all perturbed quantities have the same frequency as the driver, is justified only when a wave damping mechanism, such as leakage, is present. Special attention is given to footpoint motions with resonant frequencies and to footpoint motions with finite lifetimes.