Solar Energetic Electron Events Observed by Solar Orbiter and Wind on 2022 March 6

Solar energetic electron (SEE) events are one of the most common solar particle acceleration phenomena in the interplanetary space. Here we present a comprehensive study of SEE events with a fast-rise, fast-decay temporal profile on 2022 March 6, observed both by SolO/EPD at 0.5 AU and by Wind/3DP at 1 AU with a longitudinal separation of ~1° between the two spacecraft. SolO/EPD detect three SEE events at ~4-100 keV during 08:00 UT- 09:15 UT, while Wind/3DP only measures one SEE event at 0.6-66 keV between 08:00 UT and 13:00 UT. According to the velocity dispersion analysis, the solar injection’s start-time (peak-time) of the EPD first (third) event agrees with the solar injection’s start-time (peak-time) of the Wind/3DP event within uncertainties. Three SEE events observed by EPD exhibit, respectively, a single-power-law (SPL) energy spectrum with a power-law spectral index of β=3.4±0.1, a double-power-law (DPL) spectrum with a spectral index of β₁=4.0±0.3 (β₂=5.7±1.5) at energies below (above) a break energy of E_b=23±10 keV, and a DPL spectrum with β₁=2.9±0.9 (β₂=5.5±2.4) at energies below (above) a break energy of E_b=9±3 keV. The 3DP SEE event shows an SPL energy spectrum with β=3.4±0.2. At ~7 keV, the electron pitch angle width at half maximum is about 13-20° during the event peak-time for the three EPD events, while at 4 keV it is about 47° for the 3DP event. On the other hand, the first and third EPD events are likely accompanied by two HXR microflares measured by SolO/STIX, while the third event are probably associated with three EUV jects measured by SDO/AIA; the 3DP event is associated with the two HXR microflares and three jects. All these microflares/jets, as well as the magnetic field lines connecting to SolO and Wind, originate from the same active region (AR12957). Therefore, we can construct a formation scenario of these SEEs: the three events detected by SolO likely arise from different sources/processes at the Sun; as the electrons propagate from 0.5 AU to 1 AU, the three events merged into one event detected by Wind.