Effect of Coherent Structures on Energetic Particle Intensity in the Solar Wind at 1 AU

Tuesday, 16 December 2014
Jeffrey Tessein1, David J Ruffolo2, Minping Wan1, William H Matthaeus1, Marcia Neugebauer3 and Joe Giacalone3, (1)University of Delaware, Newark, DE, United States, (2)Mahidol University, Bangkok, Thailand, (3)University of Arizona, Tucson, AZ, United States
We present results from an analysis of ACE observations of energetic
particles in the 0.047-4.75 MeV range associated with shocks and discontinuities in the solar wind. In
our previous work, Tessein et al. 2013, we found a high correlation between
discontinuities, identified using the PVI statistic (essentially a normalized vector
increment) and the intensity of energetic
particles measured by ACE/EPAM. Our previous study was primarily a superposed
epoch analysis using 12 years worth of data. In this study we look more closely at what causes
this correlation by examining individual events to determine what
causes the association between the intensity and the location of the discontinuity.
We find that in many cases the discontinuity is located at the rising or trailing
edge of an energetic particle peak which reveals
that the discontinuities may act as barriers which inhibit the motion of
energetic particles across the boundaries, rather than as sources of particle
acceleration. We also find that the energetic particle peak is often associated
with strong interplanetary shocks that are not documented in the ACE shock
list. The distinction between weak shocks and other discontinuities, which can appear
similar in the observations, is a further complication that we address in this study.