Generation and propagation of cyclotron maser emissions in the finite auroral kilometric radiation source cavity
Generation and propagation of cyclotron maser emissions in the finite auroral kilometric radiation source cavity
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DOI：
10.1029/2002ja009403
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发表时间：
2002-12
影响因子：
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通讯作者：
P. Pritchett;R. Strangeway;R. Ergun;C. Carlson
中科院分区：
文献类型：
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作者：
P. Pritchett;R. Strangeway;R. Ergun;C. Carlson
[1]利用二维粒子模拟和快速极光快照探测器（FAST）观测，研究了极光千米辐射（AKR）源腔中产生的电子回旋脉塞辐射特性。模拟假设人口的初级极光电子与下行壳层分布。在有限磁场梯度的椭圆平面上的驱动模拟表明，微波激射辐射随着高度的降低而迅速增强，并且在注入水平以下仅5-6公里处产生时间尺度为0.5 ms的辐射爆发。在纵向平面中的初始值模拟表明，在垂直入射时撞击腔边界的辐射分量通过粒子吸收和转换到Z模式而衰减。相比之下，纵向传播分量能够沿着延伸的路径长度被放大。在源区域中的电场的FAST观测揭示，在垂直于环境磁场的平面中的极化在近似各向同性到具有“沿轨道”极化的实质性增强（多达100倍）之间变化。没有证据表明，“跨轨道”的极化是占主导地位的，因此AKR的排放不形成腔边界之间的驻波结构。
[1] The properties of the electron-cyclotron maser radiation produced in the auroral kilometric radiation (AKR) source cavity are investigated by means of two-dimensional particle-in-cell simulations and observations made by the Fast Auroral SnapshoT (FAST) Explorer. The simulations assume a population of primary auroral electrons with a downgoing shell distribution. Driven simulations in a meridional plane with a finite magnetic field gradient demonstrate that the maser radiation builds up very rapidly with decreasing altitude and that bursts of radiation with timescales of the order of 0.5 ms are produced at only 5–6 km below the injection level. Initial value simulations in a longitudinal plane show that the radiation component striking the cavity boundary at normal incidence is damped away via particle absorption and conversion to the Z mode. In contrast, the longitudinally propagating component is able to be amplified along an extended path length. The FAST observations of the electric field in the source region reveal that the polarization in the plane perpendicular to the ambient magnetic field varies between being approximately isotropic to having a substantial (as much as a factor of 100) enhancement of the “along-track” polarization. No evidence is found that the “across-track” polarization is ever dominant, and thus the AKR emissions do not form a standing wave structure between the cavity boundaries.