Seed Population Pre-Conditioning and Acceleration Observed by Parker Solar Probe
Abstract
A series of solar energetic particle (SEP) events were observed at Parker Solar Probe (PSP) by the Integrated Science Investigation of the Sun (\ISOIS) during the period from April 18, 2019 through April 24, 2019. The PSP spacecraft was located near 0.48 au from the Sun on Parker spiral field lines that projected out to 1 au within of near Earth spacecraft. These SEP events, though small compared to historically large SEP events, were amongst the largest observed thus far in the PSP mission and provide critical information about the space environment inside 1 au during SEP events. During this period the Sun released multiple coronal mass ejections (CMEs). One of these CMEs observed was initiated on April 20, 2019 at 01:25 UTC, and the interplanetary CME (ICME) propagated out and passed over the PSP spacecraft. Observations by the Electromagnetic Fields Investigation (FIELDS) show that the magnetic field structure was mostly radial throughout the passage of the compression region and the plasma that followed, indicating that PSP did not directly observe a flux rope internal to the ICME, consistent with the location of PSP on the ICME flank. Analysis using relativistic electrons observed near Earth by the Electron, Proton and Alpha Monitor (EPAM) on the Advanced Composition Explorer (ACE) demonstrates the presence of electron seed populations (40--300 keV) during the events observed. The energy spectrum of the \ISOIS~ observed proton seed population below 1 MeV is close to the limit of possible stationary state plasma distributions out of equilibrium. \ISOIS~ observations reveal the \revise{enhancement} of seed populations during the passage of the ICME, which \revise{likely indicates a key part} of the pre-acceleration process that occurs close to the Sun.
Keywords
Cite
@article{arxiv.1912.02888,
title = {Seed Population Pre-Conditioning and Acceleration Observed by Parker Solar Probe},
author = {N. A. Schwadron and S. Bale and J. Bonnell and A. Case and E. R. Christian and C. M. S. Cohen and A. C. Cummings and A. J. Davis and R. Dudok de Wit and W. de Wet and M. I. Desai and C. J. Joyce and K. Goetz and J. Giacalone and M. Gorby and P. Harvey and B. Heber and M. E. Hill and M. Karavolos and J. C. Kasper and K. Korreck and D. Larson and R. Livi and R. A. Leske and O. Malandraki and R. MacDowall and D. Malaspina and W. H. Matthaeus and D. J. McComas and R. L. McNutt and R. A. Mewaldt and D. G. Mitchell and L. Mays and J. T. Niehof and D. Odstrcil and M. Pulupa and B. Poduval and J. S. Rankin and E. C. Roelof and M. Stevens and E. C. Stone and J. R. Szalay and M. E. Wiedenbeck and R. Winslow and P. Whittlesey},
journal= {arXiv preprint arXiv:1912.02888},
year = {2020}
}