Open AccessNon adiabatic electron behavior through a supercritical perpendicular collisionless shock: Impact of the shock front turbulence
Author(s) -
Savoini P.,
Lembege B.
Publication year - 2010
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2010ja015381
Subject(s) - physics , adiabatic process , shock (circulatory) , population , electron , shock wave , radius , turbulence , mechanics , computational physics , nuclear physics , quantum mechanics , computer security , sociology , computer science , medicine , demography
Adiabatic and nonadiabatic electrons transmitted through a supercritical perpendicular shock wave are analyzed with the help of test particle simulations based on field components issued from 2 − D full‐particle simulation. A previous analysis (Savoini et al., 2005) based on 1 − D shock profile, including mainly a ramp (no apparent foot) and defined at a fixed time, has identified three distinct electron populations: adiabatic, overadiabatic , and underadiabatic , respectively, identified by μ ds / μ us ≈ 1, >1 and <1, where μ us and μ ds are the magnetic momenta in the upstream and downstream regions. Presently, this study is extended by investigating the impact of the time evolution of 2 − D shock front dynamics on these three populations. Analysis of individual time particle trajectories is performed and completed by statistics based on the use of different upstream velocity distributions (spherical shell of radius v shell and a Maxwellian with thermal velocity v the ). In all statistics, the three electron populations are clearly recovered. Two types of shock front nonstationarity are analyzed. First, the impact of the nonstationarity along the shock normal (due to the front self‐reformation only) strongly depends on the values of v shell or v the . For low values, the percentages of adiabatic and overadiabatic electrons are almost comparable but become anticorrelated under the filtering impact of the self‐reformation; the percentage of the underadiabatic population remains almost unchanged. In contrast, for large values, this impact becomes negligible and the adiabatic population alone becomes dominant. Second, when 2 − D nonstationarity effects along the shock front (moving rippling) are fully included, all three populations are strongly diffused, leading to a larger heating; the overadiabatic population becomes largely dominant (and even larger than the adiabatic one) and mainly contributes to the energy spectrum.