Energetic Particles Associated with a Coronal Mass Ejection Shock Interacting with a Convected Magnetic Structure

On 2020 November 30, Parker Solar Probe (PSP) was crossed by a coronal mass ejection (CME)-driven shock, which we suggest was also crossing a convected, isolated magnetic structure (MS) at about the same time. By analyzing PSP/FIELDS magnetic field measurements, we find that the leading edge of the MS coincided with the crossing of the shock, while its trailing edge, identified as a crossing of a current sheet, overtook PSP about 7 minutes later. Prior to the arrival of the shock, the flux of 30 keV-3 MeV ions and electrons, as measured by PSP/Integrated Science Investigation of the Sun (ISOIS)/Energetic Particle Instrument (EPI-Lo), increased gradually, peaking at the time of the shock passage. However, during the crossing of the MS downstream of the shock, the energetic-ion flux dropped dramatically, before recovering at about the time of the crossing of the trailing edge of the MS. Afterwards, the ion fluxes remained approximately constant within the sheath region of the CME shock. We interpret this depletion of energetic ions within the MS as the result of insufficient time to accelerate particles at the shock within the MS, given that the structure moves along the shock surface owing to its advection with the solar wind. We present results from a quantitative numerical model of the interaction of an idealized MS with a shock, which supports this interpretation.

Automated summary

The Parker Solar Probe crossed a coronal mass ejection-driven shock and an isolated magnetic structure, experiencing changes in ion fluxes as the shock front and back edge passed. This suggests that the movement of the magnetic structure may contribute to variations in energetic particles during solar wind interactions.