主要内容:
精彩摘抄:
We conclude that initially unmagnetized relativistic shocks in electron-positron plasmas are unable to form persistent downstream magnetic fields.
文章信息:
- · arXiv e-print (arXiv:0801.4583)
- · References in the Article
- ·
- · Translate This Page
| Title: |
| Long Term Evolution of Magnetic Turbulence in Relativistic Collisionless Shocks |
| Authors: |
| Chang, Philip; Spitkovsky, Anatoly; Arons, Jonathan |
| Publication: |
| eprint arXiv:0801.4583 |
| Publication Date: |
| 01/2008 |
| Origin: |
| ARXIV |
| Keywords: |
| Astrophysics |
| Comment: |
| 4 pages, 3 figures, contributed talk at the workshop: High Energy Phenomena in Relativistic Outflows (HEPRO), Dublin, 24-28 September 2007; Downsampled version for arXiv. Full resolution version available at http://astro.berkeley.edu/~pchang/proceedings.pdf |
| Bibliographic Code: |
| 2008arXiv0801.4583C |
Abstract
We study the long term evolution of magnetic fields generated by an initially unmagnetized collisionless relativistic $e^+e^-$ shock. Our 2D particle-in-cell numerical simulations show that downstream of such a Weibel-mediated shock, particle distributions are approximately isotropic, relativistic Maxwellians, and the magnetic turbulence is highly intermittent spatially, nonpropagating, and decaying. Using linear kinetic theory, we find a simple analytic form for these damping rates. Our theory predicts that overall magnetic energy decays like $(\omega_p t)^{-q}$ with $q \sim 1$, which compares favorably with simulations, but predicts overly rapid damping of short wavelength modes. Magnetic trapping of particles within the magnetic structures may be the origin of this discrepancy. We conclude that initially unmagnetized relativistic shocks in electron-positron plasmas are unable to form persistent downstream magnetic fields. These results put interesting constraints on synchrotron models for the prompt and afterglow emission from GRBs.
没有评论:
发表评论