2008/08/23 by Yutaka Ohira, Fumio Takahara · 1 citation
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Atomic physics #Electron #Instability #Ion #Ionosphere and magnetosphere dynamics #Mechanics #Nuclear physics #Physics #Plasma #Solar and Space Plasma Dynamics #Two-stream instability #Weibel instability #astro-ph
paper · pdf · doi:10.1086/592182
20 pages, 9 figures, accepted for publication in ApJ
arxiv created 2008/08/23 · openalex publication_date 2008/11/07 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The electrostatic behavior of a collisionless plasma in the foot region of high Mach number perpendicular shocks is investigated through a two-dimensional linear analysis and electrostatic particle-in-cell (PIC) simulations. The simulations are double periodic and taken as a proxy for the situation in the foot region. The linear analysis for relatively cold unmagnetized plasmas with a reflected proton beam shows that the obliquely propagating Buneman instability is strongly excited. We also found that when the electron temperature is much higher than the proton temperature, the most unstable mode is the highly obliquely propagating ion two-stream instability excited through the resonance between ion plasma oscillations of the background protons and of the beam protons, rather than the ion acoustic instability that is dominant for parallel propagation. To investigate nonlinear behavior of the ion two-stream instability, we have made PIC simulations for the shock foot region in which the initial state satisfies the Buneman instability condition. In the first phase, electrostatic waves grow two-dimensionally by the Buneman instability to heat electrons. In the second phase, highly oblique ion two-stream instability grows to heat mainly ions. This result is in contrast to previous studies based on one-dimensional simulations, for which the ion acoustic instability further heats electrons. The present result implies that the overheating problem of electrons for shocks in supernova remnants is resolved by considering the ion two-stream instability propagating highly obliquely to the shock normal and that multidimensional analysis is crucial to understand the particle heating and acceleration processes in shocks.