Ramirez-Ruiz 2007 数值模拟正负电子对进入外部介质时的激波和磁场产生

主要内容:
数值模拟正负电子对进入外部介质时的激波和磁场产生。 可解释激波化区上游的强磁能密度。

精彩摘抄:


文章信息:

arXiv:0707.4381 [pdf, other]

Title: Electron-Positron Pair Loading and the Origin of the Upstream Magnetic Field in GRB Shocks

Authors: Enrico Ramirez-Ruiz, Ken-Ichi Nishikawa, Christian B. Hededal

Comments: ApJ in press, 13 pages, 9 figs

Subjects: Astrophysics (astro-ph)

We investigate here the effects of plasma instabilities driven by rapid electron/positron pair cascades, which arise in the environment of GRB sources as a result of back-scattering of a seed fraction of the original spectrum. The injection of electron/positron pairs induces strong streaming motions in the ambient medium. One therefore expects the pair-enriched medium ahead of the forward shock to be strongly sheared on length scales comparable to the radiation front thickness. Using three-dimensional particle-in-cell simulations, we show that plasma instabilities driven by these streaming electron/positron pairs are responsible for the excitation of near-equipartition, turbulent magnetic fields. Our results reveal the importance of the electromagnetic filamentation instability in ensuring an effective coupling between electron/positron pairs and ions, and may help explain the origin of large upstream fields in GRB shocks.