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arXiv 2209.11136astro-ph.HEastro-ph.SR
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磁星耀斑期间强射电脉冲的直接发射

Direct Emission of Strong Radio Pulses During Magnetar Flares

Christopher Thompson

摘要:

研究了耀斑磁星的强射电脉冲发射。小尺度的电流梯度可以通过封闭磁层中火球辐射源的相同过程被印入强磁化流出物中。这种结构是地壳屈服、内部撕裂和湍流级联综合作用的结果。我们认为弱的小尺度电流的准线性发展是(i)它们被相对论膨胀拉伸并冻结,然后(ii)通过激波。特别是,我们推导出寻常波和快波的振幅,这些波出现在相对论磁化激波的下游,以响应被冻结到上游流中的模式(冻结阿尔文波或熵波)。当同向波长超过趋肤深度时,上游模可以线性地转换为在等离子体频率以上传播的次模。一个简单而准确的治疗冲击与极端磁化的发展,并形成内部冲击的流出,从一个爆裂,旋转磁星的概述。这里描述的发射过程不需要强激波或冷的$e^\pm$对(与电磁脉泽激波不稳定性相反)。在某些情况下,高频波被反射回观察者,但幅度很小,使其低于其他发射通道。占主导地位的次级电磁模式在发射时是超光速的,在流出物中受到微弱的诱导散射,并且可以在无线电波段到达观察者。

英文摘要:

The emission of intense radio pulses by flaring magnetars is investigated. Small-scale current gradients can be imprinted into a strongly magnetized outflow by the same processes that source fireball radiation in the closed magnetosphere. This structure arises from a combination of crustal yielding, internal tearing, and turbulent cascade. We consider the quasi-linear development of weak, small-scale currents as (i) they are stretched out and frozen by relativistic expansion and then (ii) pass through a shock. In particular, we derive the amplitudes of the ordinary and fast waves that emerge downstream of a relativistically magnetized shock in response to a mode that is frozen into the upstream flow (a frozen Alfvén wave or entropy wave). An upstream mode with comoving wavelength exceeding the skin depth can linearly convert to a secondary mode propagating above the plasma frequency. A simple and accurate treatment of shocks with extreme magnetization is developed, and the formation of internal shocks in the outflow from a bursting, rotating magnetar is outlined. The emission process described here does not require a strong shock or cool $e^\pm$ pairs (in contrast with the electromagnetic maser shock instability). In some cases, a high-frequency wave is reflected back to the observer, but with a minuscule amplitude that makes it subdominant to other emission channels. The dominant secondary electromagnetic mode is superluminal at emission, is subject to weak induced scattering within the outflow, and can reach the observer in the radio band.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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