Uhm 2014 在有密度跳变的时候的余辉动力学-又一篇基础动力学的文章

主要内容:
跳变可以是突然变密或者变稀。
在这些复杂的环境中，反向激波响应的变化更大，可以解释flares，dips，shallow decay等。

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Title:		Dynamics and Afterglow Light Curves of GRB Blast Waves Encountering a Density Bump or Void
Authors:		Uhm, Z. Lucas; Zhang, Bing
Publication:		eprint arXiv:1401.6758
Publication Date:		01/2014
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Comment:		32 pages, 17 figures, submitted to ApJ
Bibliographic Code:		2014arXiv1401.6758U

Abstract

We investigate the dynamics and afterglow light curves of gamma-ray burst (GRB) blast waves that encounter various density structures (such as bumps, voids, or steps) in the surrounding ambient medium. We present and explain the characteristic response features that each type of density structures in the medium leaves on the forward shock (FS) and reverse shock (RS) dynamics, for blast waves with either a long-lived or short-lived RS wave. We show that, when the ambient medium density drops, the blast waves exhibit in some cases a period of an actual acceleration (even during their deceleration stage), due to adiabatic cooling of blast waves. Comparing numerical examples that have different shapes of bumps or voids, we propose a number of consistency tests that correct modeling of blast waves needs to satisfy. Our model results successfully pass these tests. Employing a Lagrangian description of blast waves, we perform a sophisticated calculation of afterglow emission. We show that, as a response to density structures in the ambient medium, the RS light curves produce more significant variations than the FS light curves. Some observed features (such as re-brightenings, dips, or slow wiggles) can be more easily explained within the RS model. We also discuss on the origin of these different features imprinted on the FS and RS light curves.

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