CoSEE-Cat: A Comprehensive Solar Energetic Electron event Catalogue obtained from combined in situ and remote-sensing observations from Solar Orbiter

Catalogue description and first statistical results

¹ Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
² Universidad de Alcalá, Space Research Group, 28805 Alcalá de Henares, Spain
³ Postdoctoral Program Fellow, NASA Goddard Space Flight Center, Greenbelt, MD, USA
⁴ Heliospheric Physics Laboratory, Heliophysics Science Division, NASA Goddard Space Flight Center, 8800 Greenbelt Rd., Greenbelt, MD, 20770 USA
⁵ Goddard Planetary Heliophysics Institute, University of Maryland, Baltimore County, Baltimore, MD, 21250 USA
⁶ Applied Physics Laboratory, Johns Hopkins University, Laurel, MD, 20723 USA
⁷ Department of Physics and Astronomy, 20014 University of Turku, Finland
⁸ Deep Space Exploration Laboratory/School of Earth and Space Sciences, University of Science and Technology of China, Hefei, 230026 China
⁹ European Space Agency (ESA), European Space Astronomy Centre (ESAC), Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain
¹⁰ Institut de Recherche en Astrophysique et Planétologie (IRAP), CNRS, Université de Toulouse III-Paul Sabatier, Toulouse, France
¹¹ Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing (IAASARS), National Observatory of Athens (NOA), Penteli, Greece
¹² LPC2E UMR7328, OSUC/Université d’Orléans/CNRS/CNES, 3a av de la recherche scientifique, 45071 Orléans, France
¹³ Physikalisch-Meteorologische Observatorium (PMOD/WRC), Dorfstrasse 33, 7260 Davos Dorf, Switzerland
¹⁴ ETH-Zurich, Hönggerberg Campus, HIT Building, Wolfgang-Pauli-Str. 27, 8093 Zürich, Switzerland
¹⁵ Solar-Terrestrial Centre of Excellence – SIDC, Royal Observatory of Belgium, Avenue Circulaire 3, 1180 Brussels, Belgium
¹⁶ LIRA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Université, Université Paris Cité, 5 place Jules Janssen, 92195 Meudon, France
¹⁷ INAF – Astronomical Observatory of Capodimonte, Salita Moiariello 16, I-80131 Napoli, Italy
¹⁸ INAF – Astrophysical Observatory of Torino, Via Osservatorio 20, I-10025 Pino Torinese, Italy
¹⁹ University of Urbino Carlo Bo, Department of Pure and Applied Sciences, Via Santa Chiara 27, I-61029 Urbino, Italy
²⁰ INFN, Section in Florence, Via Bruno Rossi 1, I-50019 Florence, Italy
²¹ The Catholic University of America, Washington, DC, 20064 USA
²² Department of Physics and Astronomy, Queen Mary University of London, Mile End Road, London, E1 4NS UK
²³ Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey, RH5 6NT UK
²⁴ Ruhr University Bochum, Bochum, Germany
²⁵ Radboud Radio Lab, Department of Astrophysics, Radboud University, Nijmegen, The Netherlands
²⁶ Space Research Center of Polish Academy of Sciences, Warsaw, Bartycka str., 18A, 00-716 Poland
²⁷ Institute of Radio Astronomy of National Academy of Sciences of Ukraine, Kharkiv, Mystetstv str., 4, 61002 Ukraine
²⁸ University of Applied Sciences and Arts Northwestern Switzerland (FHNW), Bahnhofstrasse 6, 5210 Windisch, Switzerland
²⁹ University of Florence, Department of Physics and Astronomy, Via Giovanni Sansone 1, I-50019 Sesto Fiorentino, Italy
³⁰ INAF-Astrophysical Observatory of Arcetri, Largo Enrico Fermi 5, I-50125 Firenze, Italy
³¹ Institute of Experimental and Applied Physics, Kiel University, D-24118 Kiel, Germany

^⋆ Corresponding author: awarmuth@aip.de

Received: 28 March 2025
Accepted: 28 May 2025

Abstract

Context. The acceleration of particles at the Sun and their propagation through interplanetary space are key topics in heliophysics. Specifically, solar energetic electrons (SEEs) measured in situ can be linked to solar events such as flares and coronal mass ejections (CMEs) since they are also observed remotely in a broad range of electromagnetic emissions such as in radio and X-rays. Solar Orbiter, equipped with a wide range of remote-sensing and in situ detectors, provides an excellent opportunity to investigate SEEs and their solar origin from the inner heliosphere.

Aims. We aim to record all SEE events measured in situ by Solar Orbiter, and to identify and characterise their potential solar counterparts. The results have been compiled in the Comprehensive Solar Energetic Electron event Catalogue (CoSEE-Cat), which will be updated regularly as the mission progresses. The catalogue contains key parameters of the SEEs, as well as the associated flares, CMEs, and radio bursts. In this paper, we describe the catalogue and provide a first statistical analysis.

Methods. The Energetic Particle Detector (EPD) was used to identify and characterise SEE events, infer the electron release time at the Sun, and determine the composition of related energetic ions. Basic parameters of associated X-ray flares (timing, intensity, source location) were provided by the Spectrometer/Telescope for Imaging X-rays (STIX). This was complemented by the Extreme Ultraviolet Imager (EUI), which added information on eruptive phenomena. CME observations were contributed by the coronagraph Metis and the Solar Orbiter Heliospheric Imager (SoloHI). Type III radio bursts observed by the Radio and Plasma Waves (RPW) instrument provided a link between the SEEs detected at Solar Orbiter and their potential solar sources. The conditions in interplanetary space were characterised using Solar Wind Analyzer (SWA) and Solar Orbiter Magnetometer (MAG) measurements. Finally, data-driven modelling with the Magnetic Connectivity Tool provided an independent estimate of the solar source position of the SEEs.

Results. The first data release of the catalogue contains 303 SEE events observed in the period from November 2020 until the end of December 2022. Based on the timing and magnetic connectivity of their solar counterparts, we find a very clear distinction between events with an impulsive ion composition and ones with a gradual one. These results support the flare-related origin of impulsive events and the association of gradual events with extended structures such as CME-driven shocks or erupting flux ropes. We also show that the commonly observed delays of the solar release times of the SEEs relative to the associated X-ray flares and type III radio burst are at least partially due to propagation effects and not exclusively due to an actual delayed injection. This effect is cumulative with heliocentric distance and is probably related to turbulence and cross-field transport.