Whistler critical Mach number and electron acceleration at the bow shock: Geotail observation
Whistler critical Mach number and electron acceleration at the bow shock: Geotail observation
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DOI：
10.1029/2006gl028156
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发表时间：
2006-12-28
影响因子：
5.2
通讯作者：
Mukai, T.
中科院分区：
文献类型：
--
作者：
Oka, M.;Terasawa, T.;Mukai, T.
哨声临界马赫数M-Crit(W)是表征无碰撞激波的无量纲参数之一。最初，它的引入是为了指示哨声波不会向上游传播的临界点。事实上，我们对地球弓形激波的GeoTail数据的分析表明，在亚临界区域M-A<；M-Crit(W)有强烈的哨声波，但在超临界区域则没有。在这篇文章中，我们进一步报道了M-Crit(W)似乎调节了电子在冲击下的加速效率。在激波过渡层，由f(E)与E-Gamma G成正比的电子能谱的谱指数Gamma在亚临界区分布在3.5-5.0之间，而在超临界区检测到最硬的能谱(Gamma=3-3.5)。我们讨论了M-Crit(W)与电子加速之间的可能关系。
The 'whistler critical Mach number', M-crit(w), is one of the dimensionless parameters that characterizes collisionless shocks. Originally, it was introduced to indicate the critical point above which whistler waves do not propagate upstream. Indeed our analysis of Geotail data at the Earth's bow shock shows intense whistler waves in the sub-critical regime, M-A < M-crit(w), but not in the super-critical regime. In this paper, we further report that M-crit(w) seems to regulate the electron acceleration efficiency at the shocks. At the shock transition layer it is found that the spectral index Gamma of electron energy spectra defined by f(E) proportional to E-Gamma G is distributed between 3.5 and 5.0 in the sub-critical regime, while the hardest energy spectra with Gamma = 3-3.5 are detected in the super-critical regime. We discuss a possible relationship between M-crit(w) and the electron acceleration.