Sprecher/in: Annamaria Fedeli (University of Turku, Finland)

Titel: Energy spectra of intense Solar Energetic Electron events observed with Solar Orbiter/EPD

Zusammenfassung: The Sun is the most efficient natural particle accelerator in our solar system, capable of accelerating particles such as electrons and protons to relativistic energies, i.e., tens of MeV or GeV. Solar Energetic Particles (SEPs) are known to be accelerated at solar flare reconnection sites, as well as by shocks driven by Coronal Mass Ejections. Distinguishing between shock-driven and flare-driven SEP components remains a major challenge in understanding Solar Energetic Electron (SEE) events. One way to distinguish between these two acceleration processes of SEPs is through their energy spectra, either fluence or peak intensity. Numerous studies of in situ measurements of SEE spectra have found that more often than not, the energy spectrum presents a spectral break. The break in the observed energy spectrum could be a signature of the acceleration process itself, but it has been proposed that it is more likely caused by transport effects -- specifically, the development of beam–plasma instabilities that drive electrostatic turbulence, or particle pitch-angle scattering.
With the state of the art instruments onboard Solar Orbiter, we are able to study energy spectra better than ever before. Fedeli et al. (2025) analyse the 50 most intense events measured with Solar Orbiter/EPD between December 2020 and December 2022 to shed light on the spectral features of SEE events. Their analysis is performed with a newly developped methodology, which includes Orthogonal Distance Regression (ODR) to fit energy spectra with various different mathematical models. Their results suggest that SEE energy spectra is affected by transport and can present multiple spectral breaks. Interestingly, the spectral features do not appear to have as strong a dependence on distance as they do on longitudinal separation angles, suggesting that a good magnetic connectivity is important.

• Datum:
  26. September 2025, 11:00 – 12:00
  
  
• Ort:

  AIP; Kirch-Haus, Konferenzraum

  
  
• Kontakt:
  Frédéric Schuller
  fschuller@aip.de