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arXiv 0902.2481astro-ph.HE
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超新星遗迹中扩散激波加速对非平衡电离的作用

The Role of Diffusive Shock Acceleration on Non-Equilibrium Ionization in Supernova Remnants

Daniel J. Patnaude, Donald C. Ellison, Patrick Slane

摘要:

我们提出的半解析计算结果显示出明确的证据,在非平衡电离背后的超新星遗迹正向冲击波进行有效的扩散冲击加速(DSA)的变化。粒子的有效加速(即,宇宙射线)降低了冲击温度并提高了冲击气体的密度,从而与测试粒子近似相比改变了等离子体的电离状态,在测试粒子近似中,宇宙射线获得的冲击能量的分数微不足道。测试粒子和有效加速情况之间的差异是实质性的,并且发生在慢和快的温度平衡速率下:在加速效率较高的情况下,特定的离子状态在较低的电子温度下更多地被填充。我们还提出的结果表明,在有效的冲击加速的情况下,更高的电离分数达到显着更接近冲击波前比在测试粒子的情况下,清楚地表明,DSA可能会提高热X射线的生产。我们把这归因于更高的postshock密度,导致更快的电子温度平衡和更高的电离率。这些空间差异应该是可解决的与当前和未来的X射线任务,并可用于诊断在宇宙射线修改冲击的加速效率估计。

英文摘要:

We present results of semi-analytic calculations which show clear evidence for changes in the non-equilibrium ionization behind a supernova remnant forward shock undergoing efficient diffusive shock acceleration (DSA). The efficient acceleration of particles (i.e., cosmic rays) lowers the shock temperature and raises the density of the shocked gas, thus altering the ionization state of the plasma in comparison to the test particle approximation where cosmic rays gain an insignificant fraction of the shock energy. The differences between the test particle and efficient acceleration cases are substantial and occur for both slow and fast temperature equilibration rates: in cases of higher acceleration efficiency, particular ion states are more populated at lower electron temperatures. We also present results which show that, in the efficient shock acceleration case, higher ionization fractions are reached noticeably closer to the shock front than in the test-particle case, clearly indicating that DSA may enhance thermal X-ray production. We attribute this to the higher postshock densities which lead to faster electron temperature equilibration and higher ionization rates. These spatial differences should be resolvable with current and future X-ray missions, and can be used as diagnostics in estimating the acceleration efficiency in cosmic-ray modified shocks.

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