- 1Kiel University, Institute of Experimental and Applied Physics, Germany (yang@physik.uni-kiel.de)
- 2School of Earth and Space Sciences, Peking University
- 3Center for Space Plasma and Aeronomic Research, University of Alabama in Huntsville, Huntsville
- 4Department of Space and Climate Physics, Mullard Space Science Laboratory, University College London
- 5Universidad de Alcalá, Space Research Group
- 6Johns Hopkins University Applied Physics Laboratory
- 7Southwest Research Institute, San Antonio
Context. The Energetic Particle Detector (EPD) suite onboard Solar Orbiter provides unprecedented high-resolution measurements
of suprathermal and energetic particles in interplanetary space. These data can resolve particle dynamics near interplanetary shocks,
offering new insights into particle acceleration and transport processes.
Aims. We present observations of energetic proton bursts downstream of an interplanetary shock and discuss possible acceleration
and formation processes.
Methods. We combined data from two sensors of EPD, the SupraThermal Electron Proton (STEP) sensor and the Electron-Proton
Telescope (EPT), to investigate the proton bursts across the full energy range. We examined the dynamic energy spectra, temporal
flux profiles, pitch-angle distributions, and spectral features of these proton bursts.
Results. We find that these proton bursts travel anti-parallel to the interplanetary magnetic field (IMF) in a region where the IMF
is pointing southward, substantially out of the ecliptic plane. These bursts typically last for ∼10-20 s and span a wide energy range
from ∼20 to ∼1000 keV. Their energy spectra typically show an evident bump in the ∼20-100 keV range, characterized by a valley at
∼20-30 keV, a peak at ∼40-50 keV, a full width at half maximum of ∼30 keV, and a positive spectral slope of ∼1 between the valley
and peak. These proton bursts exhibit no velocity dispersion feature and their occurrences do not coincide with significant changes in
the IMF direction or with enhancements in the 4-100 kHz electric potential oscillations or the 0.1-4 Hz magnetic field fluctuations.
Conclusions. These results suggest that the proton bursts could originate from a source below the ecliptic plane, probably the part
of the shock situated there. These protons could be accelerated through shock-drift acceleration or shock-surfing acceleration, with
varying efficiencies at different parts of the source. The observed spectral bumps likely result from transport effects affecting the
low-energy ∼10-50 keV protons.
How to cite: Yang, L., Li, X., Heidrich-Meisner, V., Wimmer-Schweingruber, R., Wang, L., Kollhoff, A., Zhu, X., Nicolaou, G., Ding, Z., Berger, L., Liu, H., Rodríguez-Pacheco, J., Mason, G., and Ho, G.: Energetic proton bursts downstream of an interplanetary shock, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5824, https://doi.org/10.5194/egusphere-egu25-5824, 2025.
