Nishikawa 2008 相对论性Particle-In-Cell 模拟伽玛暴瞬时和余辉辐射

主要内容:
模拟显示Webel不稳定性导致了磁场的放大。辐射机制是jitter radiation。
貌似jitter radiation只能数值模拟出来，而不能解析解，所以一般都是做数值计算的文章说，但很有可能就是这种机制，因为同步辐射要求大尺度看随机、小尺度看均匀的磁场，而实际磁场应该更有可能是不均匀并且在时间上也是变化的。

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文章信息:

· arXiv e-print (arXiv:0802.2558)

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Title:		Relativistic Particle-In-Cell Simulation Studies of Prompt and Early Afterglows from GRBs
Authors:		Nishikawa, K. -I.; Hardee, P.; Mizuno, Y.; Medvedev, M.; Zhang, B.; Hartmann, D. H.; Fishiman, G. J.
Publication:		eprint arXiv:0802.2558
Publication Date:		02/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		19 pages,7 figures, contributed talk at Seventh European Workshop on Collisionless Shocks, Paris, 7- 9 November 2007. High resolution version can be obtained at http://gammaray.nsstc.nasa.gov/~nishikawa/shockws07.pdf
Bibliographic Code:		2008arXiv0802.2558N

Abstract

Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks e.g. gamma-ray bursts (GRBs) active galactic nuclei (AGNs) and microquasars commonly exhibit power-law emission spectra. Recent PIC simulations of relativistic electron-ion (or electron-positron) jets injected into a stationary medium show that particle acceleration occurs within the downstream jet. In collisionless relativistic shocks particle (electron, positron and ion) acceleration is due to plasma waves and their associated instabilities (e.g. the Weibel (filamentation) instability) created in the shock region. The simulations show that the Weibel instability is responsible for generating and amplifying highly non-uniform small-scale magnetic fields. These fields contribute to the electron's transverse deflection behind the jet head. The resulting ``jitter'' radiation from deflected electrons has different properties compared to synchrotron radiation which assumes a uniform magnetic field. Jitter radiation may be important for understanding the complex time evolution and/or spectra in gamma-ray bursts, relativistic jets in general and supernova remnants.

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