Laboratory astrophysics: Investigation of planetary and astrophysical maser emission
Laboratory astrophysics: Investigation of planetary and astrophysical maser emission
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DOI：
10.1007/s11214-013-9963-z
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发表时间：
2013-03
影响因子：
10.3
通讯作者：
R. Bingham;R. Bingham;D. Speirs;B. Kellett;I. Vorgul;S. McConville;R. A. Cairns;A. Cross;
中科院分区：
文献类型：
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作者：
R. Bingham;R. Bingham;D. Speirs;B. Kellett;I. Vorgul;S. McConville;R. A. Cairns;A. Cross;
本文描述了一个适用于行星极光射电辐射、鲸鱼座UV星和室女座CU星、耀变体喷流和天体物理冲击的回旋脉泽辐射模型。这些发射可能是由于高能电子移动到会聚磁场中，这些磁场通常与偶极类行星磁层或冲击有关。据发现，磁压缩导致形成的速度分布具有马蹄形的电子磁矩守恒的结果。在等离子体局部电子等离子体频率ω pe远小于回旋频率ω ce的条件下，发现这种分布对脉泽型辐射是不稳定的。我们已经建立了一个实验室为基础的设施，已经验证了我们原来的理论描述的许多细节，并同意与数值模拟。实验表明，马蹄形分布产生的回旋辐射的频率略低于本地电子回旋频率，与极化接近X模式和传播几乎垂直于电子束运动。我们讨论的不稳定性，包括解决辐射逃逸问题的理论和模拟的最新发展，并与这些实验室，空间和天体物理观测。实验表明，强窄带电磁辐射的频率略低于冷等离子体回旋频率的理论预测。转换效率，模式和光谱内容的测量是在密切的协议与预测的数值模拟进行的粒子在细胞的代码，也与卫星观测确认马蹄微波激射器作为一个重要的发射机制，在地球物理/天体物理等离子体。在每种情况下，我们解决如何辐射可以逃脱等离子体，而不会遭受强烈的吸收在第二谐波层。
This paper describes a model for cyclotron maser emission applicable to planetary auroral radio emission, the stars UV Ceti and CU Virginus, blazar jets and astrophysical shocks. These emissions may be attributed to energetic electrons moving into convergent magnetic fields that are typically found in association with dipole like planetary magnetospheres or shocks. It is found that magnetic compression leads to the formation of a velocity distribution having a horseshoe shape as a result of conservation of the electron magnetic moment. Under certain plasma conditions where the local electron plasma frequencyωpeis much less than the cyclotron frequencyωcethe distribution is found to be unstable to maser type radiation emission. We have established a laboratory-based facility that has verified many of the details of our original theoretical description and agrees well with numerical simulations. The experiment has demonstrated that the horseshoe distribution produces cyclotron emission at a frequency just below the local electron cyclotron frequency, with polarisation close to X-mode and propagating nearly perpendicularly to the electron beam motion. We discuss recent developments in the theory and simulation of the instability including addressing radiation escape problems, and relate these to the laboratory, space, and astrophysical observations. The experiments showed strong narrow band EM emissions at frequencies just below the cold-plasma cyclotron frequency as predicted by the theory. Measurements of the conversion efficiency, mode and spectral content were in close agreement with the predictions of numerical simulations undertaken using a particle-in-cell code and also with satellite observations confirming the horseshoe maser as an important emission mechanism in geophysical/astrophysical plasmas. In each case we address how the radiation can escape the plasma without suffering strong absorption at the second harmonic layer.