Evolution of the Suprathermal Proton Population at Interplanetary Shocks
Decker, R. B.
Wimmer-Schweingruber, R. F.
Wilson, L. B.
Roelof, E. C.
AffiliationUniv Arizona, Lunar & Planetary Lab
MetadataShow full item record
PublisherIOP PUBLISHING LTD
CitationLario, D., Berger, L., Decker, R. B., Wimmer-Schweingruber, R. F., Wilson III, L. B., Giacalone, J., & Roelof, E. C. (2019). Evolution of the Suprathermal Proton Population at Interplanetary Shocks. The Astronomical Journal, 158(1), 12.
Rights© 2019. The American Astronomical Society. All rights reserved.
Collection InformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at email@example.com.
AbstractWe investigate the evolution of the suprathermal (ST) proton population as interplanetary shocks cross 1 au. The variability of the ST proton intensities and energy spectra upstream of the shocks is analyzed in terms of the shock parameters, upstream magnetic field configurations, and preexisting upstream populations. Propitious conditions for the observation of ST particles at distances far upstream from the shock occur in parallel shock configurations when particles can easily escape from the shock vicinity. In this situation, ST intensity enhancements show onsets characterized by velocity dispersion effects and energy spectra that develop into a "hump" profile peaking around similar to 10 keV just before the arrival of the shock. The observation of field-aligned proton beams at low energies (5-10 keV) is possible under conditions that facilitate the scatter-free propagation of the particles streaming out of the shock. Upstream of perpendicular shocks, ST intensity enhancements are only observed in close proximity to the shock. Power-law proton spectra develop downstream of the shocks. The functional form for the downstream phase-space density proportional to v(-5) is observed only over a limited range of ST energies. The absence of ST populations observed far upstream of interplanetary shocks raises questions about whether ST protons contribute as a seed particle population in the processes of particle acceleration at shocks.
VersionFinal published version
SponsorsNASA-HGI grant [NNX16AF73G]; NASA/LWS grant [NNX15AD03G]; NASA [NNH17ZDA001N-LWS]; NASA under ACE grant [NNX10AT75G]