Observation and modeling of magnetospheric cold electron heating by electromagnetic ion cyclotron waves
Observation and modeling of magnetospheric cold electron heating by electromagnetic ion cyclotron waves
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DOI：
10.1002/2013ja019263
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发表时间：
2013-11
期刊：
影响因子：
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通讯作者：
Qinghua Zhou;F. Xiao;Chang Yang;Yihua He;L. Tang
中科院分区：
文献类型：
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作者：
Qinghua Zhou;F. Xiao;Chang Yang;Yihua He;L. Tang
观测并模拟了与电磁离子回旋(EMIC)波相关的冷电子加热事件。粒子和波的观测数据是由亚暴航天器在当地时间17.0-17.2期间的事件和宏观相互作用的时间历史收集的。在此过程中，激发了峰值频率为0.25 Hz的He+带EMIC波，对应于观测到的不同各向异性离子的相空间密度(PSD)。同时，观测到冷电子(1-10 eV)的能量通量在同一时期有显著的增强。低于10 eV的电子的能流增加了几到几十倍。我们用Kappa分布分量之和来拟合观测到的离子PSD，然后计算各向异性热质子驱动的波的增长率。计算结果与现场观测结果吻合较好。然后，我们研究了激发的EMIC波是否可以通过朗道共振吸收将能量转移到冷电子，从而产生电子加热。利用典型的冷电子麦克斯韦分布，我们计算了冷电子与EMIC波回旋共振时的波阻尼率。模拟结果表明，各向异性离子在He+带引起的强波增长区对应于冷电子驱动的强波阻尼区。此外，冷电子可以在大波法向角下被有效加热。目前的结果为EMIC驱动的冷电子加热提供了直接的观测证据--这是导致稳定极光红弧的潜在机制。
A cold electron heating event associated with electromagnetic ion cyclotron (EMIC) waves is observed and modeled. The observational data of particles and waves are collected by the Time History of Events and Macroscale Interactions during Substorms spacecraft at magnetic local time 17.0–17.2. During this event, intense He+ band EMIC waves with the peak frequency 0.25 Hz are excited, corresponding to the observed phase space density (PSD) of distinct anisotropic ions. Meanwhile, substantial enhancements in energy flux of cold (1–10 eV) electrons are observed in the same period. The energy flux of electrons below 10 eV is increased by several to tens of times. We use a sum of kappa distribution components to fit the observed ion PSD and then calculate the wave growth rate driven by the anisotropic hot protons. The calculated result is in good agreement with the in situ observation. Then, we investigate whether the excited EMIC waves can transfer energy to cold electrons by Landau resonant absorption and yield electron heating. Using the typical Maxwellian distribution for cold electrons, we evaluate the wave damping rates resulted from the cold electrons in gyroresonance with EMIC waves. The simulating results show that the strong wave growth region in the He+ band induced by anisotropic ions corresponds to the strong wave damping region driven by cold electrons. Moreover, cold electrons can be heated efficiently at large wave normal angles. The current results provide a direct observational evidence for EMIC‐driven cold electron heating—a potential mechanism responsible for stable auroral red arc.