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Ninety degrees pitch angle enhancements of suprathermal electrons associated with interplanetary shocks
Author(s) -
Kajdič P.,
Lavraud B.,
Zaslavsky A.,
BlancoCano X.,
Sauvaud J.A.,
Opitz A.,
Jian L. K.,
Maksimovic M.,
Luhmann J. G.
Publication year - 2014
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2014ja020213
Subject(s) - physics , interplanetary spaceflight , electron , pitch angle , shock (circulatory) , computational physics , plasma , upstream (networking) , shock wave , adiabatic process , solar wind , astrophysics , mechanics , astronomy , nuclear physics , medicine , thermodynamics , computer network , computer science
Abstract We report the results of the first systematic analysis of 90° pitch angle (PA) enhancements or the ring distributions of suprathermal ( E ∼70 eV–2 keV) electrons at interplanetary (IP) shocks. We analyze 2 h time intervals around 232 IP shocks observed by the two STEREO spacecraft between 2007 and 2011. The ring distributions were detected downstream of 114 events (49%). In 52 (22.4%) cases they were detected at the shock ramp. We also found 90° enhancements upstream of 11 (4.7%) events. Statistical analysis of basic shock properties did not reveal substantial differences between the shocks that are associated with the enhancements and those that are not. The data from the STEREO/WAVES instruments revealed that the 90° PA enhancements tend to be associated with magnetic and electric field fluctuations. Although at this point we do not have a satisfactory explanation for the mechanism that produces these distributions, our findings suggest that wave‐particle interactions play a role, while pure focusing and mirroring effects due to adiabatic motion of electrons across the shock fronts cannot fully account for the observations.