Electron-Cyclotron Maser Driven by Charged-Particle Acceleration from Magnetic Field-aligned Electric Fields
Electron-Cyclotron Maser Driven by Charged-Particle Acceleration from Magnetic Field-aligned Electric Fields
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DOI：
10.1086/309094
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发表时间：
2000-07
期刊：
影响因子：
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通讯作者：
R. Ergun;C. Carlson;J. Mcfadden;G. Delory;R. Strangeway;P. Pritchett
中科院分区：
文献类型：
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作者：
R. Ergun;C. Carlson;J. Mcfadden;G. Delory;R. Strangeway;P. Pritchett
我们提出了一个详细的描述的极光公里辐射（AKR）源区域的基础上从快速极光快照（FAST）卫星的观测，并讨论这些新的结果可能涉及到太阳和恒星的无线电源。FAST卫星观测直接在AKR源区域内，具有前所未有的空间和时间分辨率。他们证实了许多基本要素的电子回旋脉塞机制，但有实质性的修改。最重要的修改是，辐射不是从损失锥不稳定性中获得能量，而是从不稳定的“马蹄形”或“壳”分布中获得能量。最深远的影响是，电子回旋脉塞直接与一种特殊类型的带电粒子加速有关，即偶极磁场中的磁场对齐（平行）电场。这些发现改变了电子回旋脉泽机制的几个特征，可能需要重新分析一些天体物理射电源。在壳层不稳定性条件下，亮温约为1014 K的射电辐射可能是连续的，这是损失锥不稳定性的稳态极限。通过观测，我们证明了源亮度在稳态下可能高达1020 K。中等或强相对论性光束可导致宽带发射。不需要损失锥，因此辐射源可能在恒星或行星表面上方。虽然这一代是在X模式与k|| = 0时，我们建议由平行电场产生的密度腔引导的辐射有效地转换为R模式，该模式在高次谐波处经历显著较低的吸收。这些发现还表明，平行电场可能是天体物理等离子体中基本的粒子加速机制。
We present a detailed description of the auroral kilometric radiation (AKR) source region based on observations from the Fast Auroral SnapshoT (FAST) satellite and discuss how these new results may pertain to solar and stellar radio sources. FAST satellite observations are directly within the AKR source region and have unprecedented spatial and temporal resolution. They confirm many of the fundamental elements of the electron-cyclotron maser mechanism but with substantial modification. The most important modification is that the emissions do not draw their energy from a loss-cone instability; rather, the radiation results from an unstable "horseshoe" or "shell" distribution. The most far-reaching implication is that the electron-cyclotron maser is directly associated with a particular type of charged particle acceleration, a magnetic field-aligned (parallel) electric field in a dipole magnetic field. These findings change several of the characteristics of the electron-cyclotron maser mechanism and may necessitate reanalysis of some astrophysical radio sources. Under the shell instability, radio emissions with brightness temperatures ~1014 K, the steady state limit of the loss-cone instability, may be continuous. Through observations, we demonstrate that source brightness may be as high as 1020 K in steady state. A moderately or strongly relativistic beam may result in broadband emissions. A loss cone is not required, so the radiation source may be high above the stellar or planetary surface. Although the generation is in the X mode with k|| = 0, we suggest that the radiation, guided by a density cavity that is created by the parallel electric field, efficiently converts to the R mode, which experiences substantially lower absorption at higher harmonics. These findings also suggest that parallel electric fields may be a fundamental particle acceleration mechanism in astrophysical plasmas.