Excitation of whistler mode chorus from global ring current simulations
Excitation of whistler mode chorus from global ring current simulations
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DOI：
10.1029/2009ja014810
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发表时间：
2010-05
影响因子：
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通讯作者：
V. Jordanova;R. Thorne;Wen Li;Y. Miyoshi
中科院分区：
文献类型：
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作者：
V. Jordanova;R. Thorne;Wen Li;Y. Miyoshi
[1] 我们使用扩展到相对论能量和电子的全球环流-大气相互作用模型 (RAM) 模拟 2001 年 4 月 22 日地磁风暴 (Dstmin = −102 nT) 期间的环流动力学。该模型通过求解作为赤道面径向距离、磁本地时间 (MLT)、能量和俯仰角函数的弹跳平均动力学方程，保留了四个维度。 RAM 包括时间相关的对流传输和径向扩散、所有主要损失过程，并与动态二维等离子体层模型相结合。全球电场以及地球同步轨道的边界条件是根据莱斯对流模型 (RCM) 指定的，该模型由取决于行星际条件的等离子体片源群驱动。在风暴主阶段 4 ≤ L ≤ 6.5 期间，用 RAM 模拟的 1–30 keV 电子通量与 THEMIS 活动时间统计数据 (AE* > 300 nT) 相当吻合。我们计算了在 L ≤ 6.5 和所有 MLT 条件下环电流电子的俯仰角各向异性和赤道面内哨声模式合唱的线性增长率。在当地时间午夜前到黎明时区，由具有 ~5 keV 共振能量的环形电流电子在等离子体层外 (L > 4) 产生强烈的合唱波。向阳面的合唱强度较小，是由较高能量~10 keV电子引起的。我们展示了通过 HOTRAY 代码在选定位置使用 RAM 输出获得的合唱路径积分放大的第一个结果。在从等离子体片重新注入环流电子后，在当地午夜附近获得了波增益 G ≥ 200 dB 的显着合唱放大。夜侧增强合唱波的全球分布与最近对卫星近赤道等离子体波数据的调查显示出良好的一致性。
[1] We simulate ring current dynamics during the 22 April 2001 geomagnetic storm (Dstmin = −102 nT) using our global ring current–atmosphere interactions model (RAM) extended to relativistic energies and electrons. The model retains four dimensions by solving the bounce-averaged kinetic equation as a function of radial distance in the equatorial plane, magnetic local time (MLT), energy, and pitch angle. RAM includes time-dependent convective transport and radial diffusion, all major loss processes, and is coupled with a dynamic 2-D plasmasphere model. The global electric fields, as well as the boundary conditions at geosynchronous orbit, are specified from the Rice Convection Model (RCM) driven by a plasma sheet source population that depends on interplanetary conditions. The 1–30 keV electron fluxes simulated with RAM during the main phase of the storm at 4 ≤ L ≤ 6.5 agree reasonably well with THEMIS statistical data for active times (AE* > 300 nT). We calculate the pitch angle anisotropy of ring current electrons and the linear growth rate of whistler mode chorus in the equatorial plane at L ≤ 6.5 and for all MLT. Intense chorus waves are generated outside the plasmasphere (L > 4) in the premidnight to dawn local time sector by ring current electrons with ∼5 keV resonant energy. The chorus intensification on the dayside is smaller, and it is caused by higher-energy ∼10 keV electrons. We present first results of the path-integrated amplification of chorus obtained with the HOTRAY code using RAM outputs at selected locations. Significant chorus amplification with wave gain G ≥ 200 dB is obtained near local midnight after the fresh injections of ring current electrons from the plasma sheet. The global distribution of enhanced chorus waves on the nightside shows good agreement with recent surveys of near-equatorial plasma wave data from satellites.