The overall goal of Solar Orbiter is to understand how the Sun creates and controls the heliosphere. The valuable data set provided so far by the spacecraft’s comprehensive remote-sensing and in-situ instrument payload allows for coordinated observation campaigns including multi-spacecraft analyses.
This session invites contributions that boost the Solar Orbiter objectives, including observations from Solar Orbiter’s unique vantage point, combinations with other operational spacecraft, numerical simulations and theory developments that enhance our understanding of the connections between the Sun and the Heliosphere.
Orals: Tue, 29 Apr | Room L1
This talk will report on the mission status and highlight recent science results of the ESA/NASA Solar Orbiter mission. Solar Orbiter’s science return is significantly enhanced by coordinated observations with other space missions, including Parker Solar Probe, SDO, SOHO, STEREO, Hinode and IRIS, as well as ground-based telescopes like DKIST and SST. This talk with present examples of such collaborative efforts and outline future opportunities. Starting in February 2025, Solar Orbiter’s highly elliptical orbit will get progressively more inclined to the ecliptic plane, which will enable the first detailed observations of the Sun’s unexplored polar regions. I will summarise the observing plans for the first year of the high-latitude phase and describe opportunities for participation of the science community.
How to cite: De Groof, A., Mueller, D., Zouganelis, Y., Janvier, M., Walsh, A., Williams, D., Osuna, P., and Fischer, C.: Solar Orbiter: Mission Status, Science Highlights and Look-out for the High-Latitude Phase, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12901, https://doi.org/10.5194/egusphere-egu25-12901, 2025.
Solar Orbiter's coordinated observations with space-based and ground-based instruments are game changers in studying the connection between the Sun and the heliosphere. Our aim is to present the results and challenges of coordinated observations obtained with the Solar Orbiter and other instruments and highlight the advantages of using coordinated observations obtained with the Solar Orbiter and various telescopes.
We received two groups of unique coordinated observations:
1) We successfully coordinated observation campaigns between Solar Orbiter and the Daniel K. Inouye Solar Telescope (DKIST) in October 2022 and October 2023. These two telescopes provide a stereoscopic view with unprecedented high resolution. The scientific aim of these observations was related to active region studies from different vantage points (four proposals) and polar magnetic field regions (one proposal). The next observation session is planned for April 2025 and will focus on the upflow regions at the borders of active regions.
2) In October 2024, we successfully coordinated observations between the Solar Orbiter, the Interface Region Imaging Spectrograph (IRIS), and Hinode. The uniqueness of the obtained observations lies in the highest temporal cadence, 1 sec, of a solar atmosphere image ever achieved. These images were recorded by the Extreme Ultraviolet Imager (EUI) onboard Solar Orbiter. These coordinated observations from October 2024 show an active region with flaring activity.
The presented data are publicly available, and their interpretation is provided among others under the ISSI Team titled: "Active Region Evolution Under the Spotlight, with Unprecedented Coordinated High-Resolution Stereoscopic Observations and Numerical Simulations.” In conclusion, the coordinated observations from two different vantage points with imaging, spectroscopy and magnetic field instrument opened a new era in investigating structures in the solar atmosphere.
How to cite: Barczynski, K., Janvier, M., Nelson, C., Lim, D., Tritschler, A., Schad, T., Harra, L., and Müller, D.: Coordinated observation with Solar Orbiter, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16849, https://doi.org/10.5194/egusphere-egu25-16849, 2025.
Interplanetary (IP) shocks are important sites of particle acceleration in the Heliosphere and can be observed in-situ utilizing spacecraft measurements. Solar Orbiter provides observations of interplanetary shocks at different locations in the inner heliosphere with unprecedented time and energy resolution in the suprathermal (usually above 50 keV) energy range, thus opening a new observational window to study particle acceleration.
We first discuss the behaviour of a strong IP shock observed as close as 0.07 AU by Parker Solar Probe and then by Solar Orbiter at 0.7, highlighting how the shock and energetic particle production change for different evolutionary stages/locations across the event.
Then, we discuss the case the strongest shock observed by Solar Orbiter so far, associated with efficient production of very high energy electrons (up to 18 MeV) and protons (up to 30 MeV).
How to cite: Trotta, D. and the co-authors: Solar Orbiter observations of interplanetary shocks in the inner heliosphere, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6668, https://doi.org/10.5194/egusphere-egu25-6668, 2025.
The Sun produces eruptive events that release energetic particles, such as protons and electrons, into the heliosphere. These solar energetic particles (SEPs) can reach exceptionally high energies and pose risks to satellite technology and astronauts in space, particularly those outside the protective shield of Earth’s magnetic field. Identifying the mechanisms that accelerate SEPs remains a significant challenge in current research, which hampers our ability to predict SEP events effectively. Even cutting-edge space missions such as Solar Orbiter and Parker Solar Probe often do not reach close enough distances to the Sun to make direct observations of the acceleration processes without interference from transport effects.
Analyzing the spectra of SEPs is essential for understanding the acceleration mechanisms involved, as different phenomena should exhibit unique spectral features. However, it is also recognized that transport effects can significantly alter these spectral shapes, and the intricacies of these processes are still not fully understood.
Our research targets a subset of SEPs, solar energetic electrons (SEEs). We utilize the advanced measurements obtained from the Energetic Particle Detector (EPD) onboard the Solar Orbiter spacecraft. EPD boasts unparalleled time and energy resolution, detecting energetic particles at a 1-second interval across energies ranging from suprathermal to relativistic. This data, combined with Solar Orbiter's varying proximity to the Sun, enables us to analyze SEE energy spectra with unprecedented detail and to better understand the transport effects involved.
In this study, we investigate the peak intensity spectra of the most intense SEE events recorded by Solar Orbiter/EPD at 43 keV from December 2020 to December 2022. The spectral characteristics are derived by fitting the spectra using various mathematical models. We will present the findings of our statistical analysis and compare them with previous research outcomes.
How to cite: Fedeli, A., Dresing, N., Vainio, R., Gieseler, J., Gómez Herrero, R., Espinosa Lara, F., Warmuth, A., and Schuller, F.: Spectral Analysis of the most intense Solar Energetic Electron Events Observed with Solar Orbiter from December 2020 to December 2022, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11505, https://doi.org/10.5194/egusphere-egu25-11505, 2025.
We present a comprehensive catalogue of solar energetic electron (SEE) events, derived from joint observations by remote-sensing and in-situ instruments aboard the Solar Orbiter spacecraft. The Energetic Particle Detector (EPD) is used to characterise the properties of energetic electrons in situ and to estimate their injection times at the Sun. The timing, location, and intensity of associated X-ray flares is obtained using the Spectrometer/Telescope for Imaging X-rays (STIX), while the Extreme Ultraviolet Imager (EUI) provides complementary observations of the flare evolution and eruptive phenomena. The Solar Orbiter coronagraph (Metis) and heliospheric imager (SoloHI) are employed to characterise potential associated coronal mass ejections (CMEs). Type III radio bursts detected by the Radio and Plasma Waves (RPW) instrument are used to connect the eruptive solar events to the SEE events observed in situ. We present the catalogue's contents, and the methodology employed to determine key parameters. Finally, we discuss statistical results from the catalogue.
How to cite: Warmuth, A. and the STIX-EPD-RPW-EUI-Metis-SoloHI joint analysis team: Solar Orbiter's Comprehensive Solar Energetic Electron event Catalogue (CoSEE-Cat): a new resource for studying particle acceleration and transport in the heliosphere, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13913, https://doi.org/10.5194/egusphere-egu25-13913, 2025.
Solar flares and associated eruptions are a known source of solar energetic particles (SEPs). Yet, it is often challenging to establish a precise link between individual flares and SEP events measured in-situ throughout the heliosphere. The Solar Orbiter mission with its Spectrometer/Telescope for Imaging X-rays (STIX ) and Energetic Particle Detector (EPD) provide new measurements for a systematic investigation of these phenomena. Based on these data, we developed an algorithm that automatically links solar flares to SEP events using a STIX flare list, model prediction of magnetic connectivity between the Sun and the spacecraft, and SEP electron measurements from EPD. A first evaluation shows that 50% of the links produced by the algorithm are actual physical links, while inversely 26% of all manually identified physical links were detected by the algorithm for the two-years test period in 2021 and 2022. This can be considered as a modest success rate for a fully automatic linkage between solar and in-situ events, but it provides a very helpful pre-selection of about 100 SEP-related flares compared to more than 5000 flares detected with STIX.
How to cite: Janitzek, N., Kistler, F., Stiefel, M., Barczynski, K., Zhu, Y., Harra, L., Gomez-Herrero, R., Rodriguez-Pacheco, J., Roco-Moraleda, M., Battaglia, A., Collier, H., and Krucker, S.: An automated approach to link solar flares and energetic particle events based on measurements from Solar Orbiter and modelled magnetic connectivity, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19476, https://doi.org/10.5194/egusphere-egu25-19476, 2025.
Plasma upflows with a Doppler shift exceeding 20 km/s at active region (AR) boundaries are considered potential sources of nascent slow solar wind. These upflows are often located at the footpoints of large-scale fan-like loops, showing temperature-dependent Doppler shifts from the transition region to the lower corona. In this study, we identified two upflow regions in the vicinity of an active region by analyzing the blueshifts of the Fe XII 195 line observed by Hinode/EIS. Context images for the two regions were obtained by the High Resolution Imager (HRI) telescope of the Extreme Ultraviolet Imager (EUI) on board the Solar Orbiter. The region to the west of the AR appears as typical fan-like loops, while the eastern upflow region is near AR moss, revealing moss-like features but with lower intensity from the upper transition region into the corona. Free from the potential contamination of fan-like loops, the east region provides unique insights into the flow properties from the chromosphere into the corona and the coupling between the atmospheric layers in the upflow region. Carefully addressing the point spread function issue with the SPectral Imaging of the Coronal Environment (SPICE), we derive the Doppler shifts of Ne VIII, emitted by cooler plasma compared to Fe XII, in these two regions. The fan-like loops in the west show downflows (redshifts) of approximately 20 km/s, whereas the eastern region shows upflows (blueshifts) from 20 to 30 km/s. This suggests the actual upflows might develop in the upper transition region (~0.6 MK), challenging the typical conclusion of a coronal upflow (> 1 MK), which is affected by downflows in fan-like loops. Observations from the Interface Region Imaging Spectrograph (IRIS) satellite confirm the coronal upflows influence the velocity field in the lower transition region (Si IV). However, the critical transition temperature from a net redshift into a blueshift is still unclear due to the lack of temperature coverage. Combined with potential field extrapolations, we confirm the driver of the major upflow component might be persistent reconnections between over-pressure AR loops and ambient low-pressure field lines. However, the small-scale dynamics in upflows by observed HRIEUV, e.g., dynamic fibrils and jetlet, may still contribute passively to the upflow plasma in the coupled atmosphere. Preliminary differential emission measure (DEM) analysis reveals a photospheric abundance in both upflow regions, which is compared to the in-situ solar wind measurements when the Solar Orbiter was predicted to connect to the west upflow region by the Connectivity tool.
How to cite: Zhu, Y., Harra, L., Barczynski, K., Janitzek, N., Plowman, J., Mzerguat, S., Auchère, F., Thompson, W., Parenti, S., Chitta, L. P., Peter, H., Fredvik, T., Grundy, T., Ni, Y.-W., and Chen, P.-F.: Upflows in a Decaying Active Region and its Potential Contribution to the Solar Wind , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18322, https://doi.org/10.5194/egusphere-egu25-18322, 2025.
Intermittency is a common feature of solar wind turbulence where it presents itself as non-Gaussian fluctuations and embedded coherent structures. Small-scale magnetic field fluctuations in interplanetary coronal mass ejections (ICMEs) have a behaviour matching the presence of intermittency but properties and significance of intermittency in ICMEs are not yet known. We use data from Solar Orbiter and Parker Solar Probe to study intermittency in 49 ICMEs and the related upstream and downstream solar wind periods and sheath regions at heliospheric distances of 0.25-1 au. For comparing the different plasma environments, the gradient of kurtosis is used to measure intermittency with larger values being an indication of faster increase of kurtosis towards smaller scales and thus higher level of intermittency. Kurtosis is seen to behave similarly in all studied plasma environments, but the largest gradients are seen in the upstream solar wind at the lower end of the inertial range. The downstream solar wind, sheaths and ICMEs show similar values and behaviour for the gradient. The connection between kurtosis and common plasma parameters is studied with some differences found in different intervals but with no strong correlations.
How to cite: Ruohotie, J., Good, S., Möstl, C., and Kilpua, E.: Statistical analysis of intermittency in solar wind transients: Solar Orbiter and Parker Solar Probe observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9722, https://doi.org/10.5194/egusphere-egu25-9722, 2025.
A very fast coronal mass ejection (CME) was ejected on September 5, 2022, which was measured in situ by Parker Solar Probe (PSP) and Solar Orbiter, and observed remotely by Stereo-A, SOHO and PSP. Here, we carry out the reconstruction of the CME in the corona by using SOHO/LASCO, STEREO-A/COR2, and PSP/WISPR data. The obtained CME parameters are used as input for an MHD simulation with the PLUTO code of an erupting flux rope propagating into the Parker spiral reconstructed with RIMAP, a method which reconstructs the heliosphere on the ecliptic plane from in situ measurements acquired by spacecraft with heliocentric orbits. Then we analyze in-situ Solar Orbiter measurements at 0.7 AU to check the results of the RIMAP simulation, to study the CME-driven shock properties and how they compare with the simulated ones. The level of magnetic turbulence around the shock and the transport of energetic particles are also considered: large fluxes of energetic particles accelerated in situ are measureded by Solar Orbiter/EPD instrument in the energy range 111 keV-3.7 MeV, causing an amplification of magnetic fluctuations. Analyzing the upstream energetic particle time profiles, the transport regime of accelerated particles is found to be normal, although non Gaussian features are also present. As a surprising results, we find that the energetic particles differential flux at Solar Orbiter has a spectral index harder than that predicted by diffusive shock acceleration for the measured compression ratio. The possible reasons for such a discrepancy are discussed.
How to cite: Zimbardo, G., Bemporad, A., Biondo, R., Frassati, F., Mancuso, S., Nisticò, G., Pagano, P., Perri, S., Prete, G., Reale, F., and Susino, R.: Joint investigation of the September 5, 2022, coronal mass ejection event with remote observations, numerical simulations, and in situ measurements, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7018, https://doi.org/10.5194/egusphere-egu25-7018, 2025.
On October 28, 2021 the first X-class solar flare of Solar Cycle 25 occurred in active region NOAA AR 12887 with a peak at 15:35 UT. It produced the rare event of ground-level enhancement of the solar relativistic proton flux and a global extreme ultraviolet wave, along with a fast halo coronal mass ejection (CME) as seen from Earth's perspective. A few hours before the flare, a slower CME had erupted from a quiet Sun region just behind the northwestern solar limb. Solar Orbiter was almost aligned with the Sun-Earth line and, during a synoptic campaign, its coronagraph Metis detected the two CME events in both Visible Light (VL) and UltraViolet (UV) channels. The earlier CME took place in the northwest (NW) sector of Metis field of view, while several bright features of the flare-related event appeared mostly to the southeast (SE).
The NW and SE events have two distinct origins, but were both characterized by a very bright emission in HI Ly-alpha visible in the UV images of Metis up to 8 solar radii. This work is a follow-up study of two out of the six events analyzed by Russano et al. 2024 (A&A, 683, A191), aimed at investigating the evolution of these two almost co-temporal CMEs but originating in such distinct source regions. To that end, we extensively inspect data sets from numerous remote-sensing instruments observing the Sun in several spatial and spectral regimes. We characterize several aspects of these CMEs, including their three-dimensional properties, kinematics, mass, and temporal evolution of those quantities.
Results of this work point to notable differences between these two events showing significant UV emission in the corona.
How to cite: De Leo, Y., Cremades, H., Iglesias, F. A., Teriaca, L., Aznar Cuadrado, R., López, F. M., di Lorenzo, L., Temmer, M., Romoli, M., and Spadaro, D.: Two distinct eruptive events observed by Metis on October 28, 2021, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8631, https://doi.org/10.5194/egusphere-egu25-8631, 2025.
How to cite: Wang, R.: High-resolution Observations of Clustered Dynamic Extreme-Ultraviolet Bright Tadpoles (CEBTs) near the Footpoints of Corona Loops, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3015, https://doi.org/10.5194/egusphere-egu25-3015, 2025.
The ESAC Science Data Centre (ESDC) plays a crucial role in preserving and providing long-term access to data from all ESA space science missions. Recent enhancements to the Solar Orbiter Archive (SOAR) aim to provide researchers with more intuitive and powerful tools for data access. These updates include the ability to search data by solar distance and utilize Field of View (FoV) tables. The contents of the Solar Orbiter mission orbit file have been ingested and is available via our standard TAP interface. This allows users to search a rich set of metadata based on Distance and Latitude. Integration with commonly used tools like Python, TOPCAT, and SunPy has further streamlined data access and interoperability. Other upcoming features will be presented.
How to cite: Middleton, H., Masson, A., Cook, J., and Janitzek, N.: New Highlights from the Solar Orbiter Archive, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6493, https://doi.org/10.5194/egusphere-egu25-6493, 2025.
The Energetic Solar Eruptions: Data and Analysis Tools (SOLER) project (2024–2027) will investigate the most energetic phenomena occurring at the Sun using the newly expanded unprecedented heliospheric spacecraft fleet including Solar Orbiter, Parker Solar Probe, BepiColombo, STEREO A, and near-Earth spacecraft. We investigate energetic solar eruptions starting from three perspectives: fast (speed > 1000 km/s) coronal mass ejections (CMEs), strong (GOES class > M5) X-ray flares, and large (detected at >25 MeV proton energies) solar energetic particle events. Key parameters of the various eruption phenomena will be determined and their interrelations examined to make significant leaps in our understanding on how the eruptive phenomena are linked to each other, how they interact with each other, and how they result in acceleration and release of high energy particles from the solar corona into interplanetary space. Because of their direct link to particle energisation, large-amplitude coronal waves and shocks related to these events will be in focus as well. Magnetic connections of sources with each other and with the in-situ observers will be determined. In addition to producing significant amounts of new scientific knowledge in the field, SOLER will provide the wider scientific community a wide array of advanced data products, and novel data analysis and visualisation tools that will be openly distributed.
This poster will present an overview of SOLER, its objectives and plans, and the first results of the project.
SOLER has received funding from the European Union's Horizon Europe research and innovation programme under grant agreement No 101134999.
How to cite: Vainio, R., Briand, C., Dresing, N., Kilpua, E., Morosan, D., Pomoell, J., Price, D., Veronig, A., and Warmuth, A.: The Horizon Europe SOLER project (2024-2027): project objectives and first results, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11202, https://doi.org/10.5194/egusphere-egu25-11202, 2025.
Ion beams are non Maxwellian features frequently observed in solar wind ion distribution functions. These beams appear as two distinct populations of ions with the same charge state but different bulk velocities. While various mechanisms – such as magnetic reconnection and resonant wave-particle interactions – have been proposed to explain their formation, their origin remains an open question and a subject of ongoing debate.
To better understand the kinetic processes driving particle acceleration, it is essential to identify and isolate the double streams in the particle measurements. To achieve this, we have developed a novel numerical method that leverages clustering techniques commonly used in machine learning. This approach enables the successful separation of up to four ion populations: the proton core and beam, as well as the alpha particle core and beam.
We present case studies in which proton and alpha beams were identified during specific events, such as magnetic switchbacks and interplanetary disturbances associated with solar eruptions. By isolating these beams, we examine their density, temperature, and velocity, and provide a detailed characterization of how the different distribution functions respond to such dynamic conditions.
These findings offer valuable insights into the intricate behavior of solar wind ions, shedding light on the underlying acceleration mechanisms and deepening our understanding of the complex processes shaping the solar wind.
How to cite: De Marco, R., Laurenza, M., D'Amicis, R., Bruno, R., Torda, T., Perrone, D., Marcucci, M. F., Owen, C. J., Louarn, P., and Fedorov, A.: Decoding Ion Beams in the Solar Wind: Insights into Kinetic Processes and Acceleration Mechanisms, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10791, https://doi.org/10.5194/egusphere-egu25-10791, 2025.
Proper characterization of particle energization in the solar wind requires observations from thermal through energetic particles of multiple elements. Observations of in situ particles in different energy ranges require different instruments that must be properly intercalibrated. Solar Orbiter’s Heavy Ion Sensor (HIS) is a time-of-flight ion mass spectrometer that observes the heavy ion composition of the thermal solar wind. Orbiter’s Suprathermal Ion Spectrograph (SIS) is an energy time-of-flight detector that observes particles from suprathermal energies to the lower range of energetic particles. We report on the intercalibration between these two instruments in six isotropic, quiet intervals when both instruments provide reliable, high-quality observations. These results will enable analysis of more complex events where transient processes locally modify the distributions.
How to cite: Alterman, B., Allen, R., Dewey, R., Livi, S., Raines, J., Lepri, S., Spitzer, S., Bert, C., Owen, C., Ho, G., Galvin, A., Kistler, L., Allegrini, F., Ogasawara, K., Wurz, P., Philips, M., Damicis, R., Mason, G., Wimmer-Schweingruber, R., and Rodríguez-Pacheco, J. and the Inter-Calibration of Solar Orbiter's Heavy Ion Sensor and Suprathermal Ion Spectrograph team: Inter-Calibration of Solar Orbiter's Heavy Ion Sensor and Suprathermal Ion Spectrograph, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21838, https://doi.org/10.5194/egusphere-egu25-21838, 2025.
The wave-particle resonance is fundamental for mediating energy transfer, thereby facilitating particle heating and acceleration in the plasma universe. Cyclotron resonance between ion cyclotron waves and solar wind ions offers a compelling explanation for the long-standing solar wind heating problem.
Additionally, this resonance can drive wave excitation, although direct observational evidence remains limited. The Solar Orbiter spacecraft provides high-resolution three-dimensional ion velocity distributions, enabling detailed investigations of wave-particle interactions. Here, we present two events featuring counterpropagating ion cyclotron waves, in which the ion gyro-phase spectra exhibit phase-bunched signatures, providing solid evidence of cyclotron resonance. The anisotropic core and beam populations resonate with outward- and inward-propagating waves, respectively. The ion distributions denote pronounced agyrotropy, highlighting the pivotal role of nonlinear wave-particle resonances in driving wave excitation and particle energization in the solar wind.
How to cite: Li, J., Khotyaintsev, Y., and Graham, D.: Identifying the Ion Cyclotron Wave Excitation via Cyclotron Resonance in the Solar Wind, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9592, https://doi.org/10.5194/egusphere-egu25-9592, 2025.
In this study, we determine the differential emission measures (DEMs) using Solar Orbiter/Extreme Ultraviolet Imager (EUI)/Full Sun Imager (FSI) and AI-generated EUV data. The FSI observes only two full-disk extreme UV (EUV) channels (174 and 304 Å), which poses a limitation for accurately determining DEMs. We address this problem using deep learning models based on Pix2PixCC, trained using the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) dataset. These models successfully generate five-channel (94, 131, 193, 211, and 335 Å) EUV data from 171 and 304 Å EUV observations with high correlation coefficients. We then apply the trained models to the Solar Orbiter/EUI/FSI dataset and generate the five-channel data that the FSI cannot observe. Here we use the regularized inversion method to compare the DEMs from the SDO/AIA dataset with those from the Solar Orbiter/EUI/FSI ones with AI-generated data. First, we demonstrate that, when SDO and Solar Orbiter are at inferior conjunction, the main peaks and widths of both DEMs are well consistent with each other at the same coronal structures. These results reveal that deep learning can make it possible to properly determine the DEMs using Solar Orbiter/EUI/FSI and AI-generated EUV data. Additionally, we determine the DEM when the two instruments are at various angular separations, such as when 60 degrees (L4 and L5) and 180 degrees apart. Our results suggest that the stereoscopic DEM analysis of coronal features using our methodology should be possible.
How to cite: Youn, J., Lee, H., Jeong, H.-J., Lee, J.-Y., Park, E., and Moon, Y.-J.: Exploring the Potential of DEM Analysis Using Solar Orbiter/EUI and AI-Generated Data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11786, https://doi.org/10.5194/egusphere-egu25-11786, 2025.
We study tiny EUV jets jointly observed by the Extreme Ultraviolet Imager (EUI) onboard Solar Orbiter and the high-resolution H-alpha images from the Visible Imaging Spectrometer (VIS) installed on the 1.6 m Goode Solar Telescope (GST) at the Big Bear Solar Observatory (BBSO). The EUV jets repeatedly occurred on 2022-10-29 around 19:10 UT in a quiet sun region (201E, 356N). SDO and IRIS data are used to connect the GST images with the EUI images. A general agreement between the direction of the EUI jets and the alignment of the VIS spicules probably indicates the local magnetic structure. However, the EUI jets show an evolving helical structure, while the H-alpha spicules retain the linear shape. An obvious H-alpha counterpart to the EUI jets is the appearance of red shift concentrated under the EUI jets, while blue shift dominates elsewhere. We use the thin flux tube model to suggest that the morphology of the transient coronal brightening is a manifestation of Alfven wavefronts generated as a result of exchange reconnection, and the red-shifted H-alpha line structure is a downward reconnection outflow from the coronal X-point. The detection of such a sophisticated coronal evolution decoupled from chromospheric dynamics is made possible by the Solar Orbiter's high resolution and a distinctive viewing angle, furthering its goal of understanding how the Sun generates small-scale ejections in the chromosphere and corona.
How to cite: Lee, J.: The First Joint Observation of EUV Jets and spicules with BBSO/GST and Solar Orbiter, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7244, https://doi.org/10.5194/egusphere-egu25-7244, 2025.
The Spectrometer/Telescope for Imaging X-rays (STIX) on board Solar Orbiter continuously measures the Sun in the energy range 4-150 keV. Due to the spacecraft’s peculiar orbit, around 50% of all STIX flares are backside flares and lack a corresponding GOES class. In Stiefel et al. (2025) we describe the correlation between the STIX background detector and GOES measurements where we found a power-law function between the two data sets. This function can be used to get a proxy of the GOES class for large backside flares.
Building up on the approach of using the background detector of STIX, we want to discuss how we can improve the spectral fitting of the thermal emission of large flares (> X1-class) observed by STIX and discuss the occurrence of “super-hot” components (e.g. Caspi et al. (2010)) in these flares. Using imaging and spectral analysis of STIX data, we want to understand the physical origin and the temporal evolution of the super-hot component. This talk will highlight the importance of understanding the thermal emission in solar flares and the richness of information we can gain regarding the thermal emission by combining spectral and spatial observations by various X-ray instruments.
How to cite: Stiefel, M. Z., Bajnoková, N., Massa, P., and Krucker, S.: X-ray diagnostics of thermal flare emissions by Solar Orbiter/STIX and GOES, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11967, https://doi.org/10.5194/egusphere-egu25-11967, 2025.
We examine 3He-rich solar energetic particles (SEPs) detected on 2023 October 24-25 by Solar Orbiter at 0.47 au. The measurements revealed heavy-ion enhancement not increasing smoothly with mass. C, and especially N, Si, and S, stand out in the enhancement pattern with large abundances. Except for 3He, heavy ion spectra can only be measured below 0.5 MeV/nucleon. At 0.386 MeV/nucleon, the event showed a huge 3He/4He ratio of 75.2±33.9, larger than ever previously observed. Solar Dynamics Observatory extreme ultraviolet data showed a mini filament eruption at the solar source of 3He-rich SEPs that triggered a straight tiny jet. Located at the boundary of a low-latitude coronal hole, the jet base is a bright, small-scale region with a supergranulation scale size. The emission measure provides relatively cold source temperatures of 1.5 to 1.7 MK between the filament eruption and nonthermal type III radio burst onset. The analysis suggests that the emission measure distribution of temperature in the solar source could be a factor that affects the preferential selection of heavy ions for heating or acceleration, thus shaping the observed enhancement pattern. Including previously reported similar events indicates that the cool material of the filament in the source is a common feature of events with heavy-ion enhancement not ordered by mass. Surprisingly, sources with weak magnetic fields showed extreme 3He enrichment in these events. Moreover, the energy attained by heavy ions seems to be influenced by the size and form of jets.
How to cite: Bucik, R., Mason, G., Mulay, S., Ho, G., Wimmer-Schweingruber, R., and Rodríguez-Pacheco, J.: Origin of Unusual Composition of 3He-Rich Solar Energetic Particles , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13242, https://doi.org/10.5194/egusphere-egu25-13242, 2025.
The Electron Analyser System (EAS), a dual sensor system within the Solar Wind Analyser (SWA) suite, is capable of measuring a full 3D velocity distribution function (VDF) of solar wind electrons with energies of a few eV to ~5 keV in an accumulation time of 1 second. At full energy and angular resolution, telemetry constraints limit the maximum EAS normal mode data return to 1 3D VDF every 10 seconds. However, the SWA DPU includes a rolling buffer capable of storing 1-second full electron VDF data for a period of 5 minutes. Over the last year, during periods in which the telemetry allocation is high, we have been able to freeze this buffer and return this data up to three times per hour, generating a large dataset of very high time resolution electron measurements. Moreover, a trigger detection algorithm is at times operated by the Radio and Plasma Waves (RPW) instrument, combining data from the magnetometer and the SWA Proton and Alpha Sensor in order to detect the passage of a shock passed the spacecraft. Although the operation of the algorithm has suffered from a number of technical issues, receipt of a positive flag is used by SWA to freeze the EAS rolling buffer and add the resulting data to the telemetry stream. This operation has again generated a significant dataset of high resolution electron data which is often associated with a solar wind transient, such as a shock or a current sheet.
In this presentation, we present case studies of periods in which SWA-EAS returned this high resolution data, bringing out new features of electron dynamics that are not captured by normal resolution instruments on Solar Orbiter or other missions. For example, we examine the development of electron distributions across the shock, revealing how the ‘flat-top’ nature of the downstream distribution develops as a function of pitch angle. Moreover, even the manually triggered events can be used to reveal how the electron distribution may vary with less dramatic, but more regular, variations in the solar wind, such as those driven by waves or instabilities.
How to cite: Owen, C. and the Solar Orbiter SWA, MAG and RPW teams: Solar wind electron dynamics revealed by high-time resolution observations of 3D electron velocity distribution functions captured by Solar Orbiter SWA., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13243, https://doi.org/10.5194/egusphere-egu25-13243, 2025.
Solar flares are energetic and dynamic phenomena in the solar system emitting radiation impulsively, and solar energetic electrons (SEEs). Therefore, we investigate the high-energy X-ray emission and SEEs observed by STIX and EPD onboard the Solar Orbiter mission. During September 18-30, 2021, the Solar Orbiter mission - being closer to the Sun (~0.6 AU) and having a moderate separation angle (~30-400) from the Sun-Earth line provided a unique opportunity for an exhaustive multi-wavelength investigation of several weak flares, associated nonthermal X-ray emission, and SEE’s characteristics. A multiwavelength investigation of spectral and imaging-mode observations of the 20 weak (~B-class), but hard X-ray (HXR)-rich flares, revealed a definitive role of pre-flare plasma density in the loops to be responsible for disparate thermal-nonthermal emission partition during flares. We further investigate remote and in-situ observations of three flares (two B-class, and a C1.6 -class) showing different thermal-nonthermal X-ray emission partitions, and associated SEEs. The timing and spatial correlation of the solar events at source and in-situ SEE enhancements revealed agreement in the 1) onset time of HXR emission and SEE enhancement, and 2) power-law spectral indices of HXR emission and SEEs. Interestingly, we find a very weak HXR burst (B3-class; nonthermal electron spectral index ~ 6) to cause a significant SEE enhancement despite an impulsive C3 flare that occurred a mere 15 minutes before it without any SEE enhancement signatures. Therefore, a comprehensive assessment of energy released during flares is only possible by characterising the observed nonthermal emission as well as particles.
How to cite: Awasthi, A. K., Warmuth, A., Mrozek, T., Sylwester, J., Sylwester, B., and Schuller, F.: Investigating weak flares energetics through nonthermal emission and solar energetic electrons: STIX and EPD observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20333, https://doi.org/10.5194/egusphere-egu25-20333, 2025.
Energetic electrons accelerated by solar flares in the corona may propagate downward, produce X-rays in the chromosphere, and upward, producing coherent type III radio bursts in interplanetary space. Previous statistical studies of radio and X-ray flare observations have found a good temporal link between the two wavelengths but only a weak correlation between the intensities, in part due to the different emission mechanisms. Assuming both electron populations share properties from a common acceleration region, theory has predicted a link between the speed of the electron beams travelling outwards (deduced from radio) and the energy density of the electrons travelling downwards (deduced from X-rays). The Solar Orbiter mission is equipped with the STIX and RPW instruments, allowing for simultaneous observations of both X-ray and Radio emissions that can test this theory. We present results derived from the comparison of 38 radio type III bursts detected by RPW (<10 MHz) associated in time with flares observed by STIX in the 4-150 keV range . From X-ray spectroscopy we obtained the electron spectral index and the electron number of the associated HXR peak, from which the power can be estimated. We derived the Type III exciter speed using the rise and peak times of the time-profiles (Vr and Vp , respectively) in the 0.4-4 MHz range. We find the observed ratio Vr/Vp is 0.78 +- 0.07, complementing previous similar studies at higher frequencies (30 – 70 MHz) with a ratio of 0.8+-0.06. We report a correlation between the power of all electrons with energies above 30 keV and Vr (cc=0.47), whilst none is obtained when comparing it with Vp. There is an anticorrelation of the velocities with the electron spectral index as expected, however the anticorrelation coefficients are weak. Relevant correlations are seen when comparing the peak Radio intensity with the electron spectral index (cc=-0.81) and power (E>30keV) (cc=0.59). The energy of the escaping electrons producing the type III radio emission and the ones producing non-thermal HXRs are also compared, showing a significant correlation (cc=0.57). Our results show a clear relation between the most energetic electrons in both populations of beams, supporting the scenario of a common acceleration region. The energy distribution of escaping and confined electrons for some events may depend on other parameters like the geometry of the reconnecting magnetic field.
How to cite: Paipa-Leon, D., Reid, H., Vilmer, N., and Maksimovic, M.: Diagnostics of flare-accelerated electron beams with X-ray and Radio data from Solar Orbiter, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-541, https://doi.org/10.5194/egusphere-egu25-541, 2025.
Nanojets are small-scale jets generated by component reconnection, characterized by their motion perpendicular to the reconnecting magnetic field lines. As an indicator of nanoflare events, they are believed to play a significant role in coronal heating. Using high-resolution EUV imaging observations from the Solar Orbiter/Extreme Ultraviolet Imager (EUI), we identified 27 nanojets during an M7.6 flare on September 30, 2024. Most nanojets exhibit velocities around 1000 km/s, comparable to the typical coronal Alfvén speed. To our knowledge, these speeds are the highest ever reported for small-scale jets. The average kinetic energy of the nanojets is estimated to be 2.3×1025 erg, with events of higher speeds typically displaying greater kinetic energy and longer durations.
How to cite: Gao, Y., Tian, H., Van Doorsselaere, T., and Berghmans, D.: Solar Orbiter/EUI observation of nanojets during a flare with unprecedented high speeds, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4897, https://doi.org/10.5194/egusphere-egu25-4897, 2025.
