Optical characterization of the growth and spatial structure of a substorm onset arc
Optical characterization of the growth and spatial structure of a substorm onset arc
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DOI：
10.1029/2010ja015376
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发表时间：
2010-10-12
影响因子：
2.8
通讯作者：
Angelopoulos, V.
中科院分区：
文献类型：
--
作者：
Rae, I. J.;Watt, C. E. J.;Angelopoulos, V.
我们提出了一个详细的案例研究的极光形式的特点，构成亚暴膨胀阶段开始的第一个电离层签名。光学频率和沿弧（方位角）波数谱的分析提供了最强的约束到目前为止的潜在机制和不稳定性，在近地磁层伴随极光的开始和之前向极弧扩张和极光解体。我们评估的频率和增长率的极光形式作为方位角波数的函数，以确定这些波的特性是否与目前的模型的亚暴发病机制是一致的。我们发现，极光形式的频率，空间尺度和增长率是最一致的交叉场电流不稳定性或气球不稳定性，最有可能触发靠近离子等离子体片的内边缘。这一结果是支持的亚暴膨胀阶段的近地等离子体片启动。我们还提出的证据表明，极光波动的频率和相位特性可能会产生通过共振过程操作沿着地磁场。我们的观测提供了最强大的约束，迄今为止的电离层表现的物理过程中运作的前几分钟左右的极光亚暴开始。
We present a detailed case study of the characteristics of auroral forms that constitute the first ionospheric signatures of substorm expansion phase onset. Analysis of the optical frequency and along-arc (azimuthal) wave number spectra provides the strongest constraint to date on the potential mechanisms and instabilities in the near-Earth magnetosphere that accompany auroral onset and which precede poleward arc expansion and auroral breakup. We evaluate the frequency and growth rates of the auroral forms as a function of azimuthal wave number to determine whether these wave characteristics are consistent with current models of the substorm onset mechanism. We find that the frequency, spatial scales, and growth rates of the auroral forms are most consistent with the cross-field current instability or a ballooning instability, most likely triggered close to the inner edge of the ion plasma sheet. This result is supportive of a near-Earth plasma sheet initiation of the substorm expansion phase. We also present evidence that the frequency and phase characteristics of the auroral undulations may be generated via resonant processes operating along the geomagnetic field. Our observations provide the most powerful constraint to date on the ionospheric manifestation of the physical processes operating during the first few minutes around auroral substorm onset.