Cold Ion Heating by Magnetosonic Waves in a Density Cavity of the Plasmasphere
Cold Ion Heating by Magnetosonic Waves in a Density Cavity of the Plasmasphere
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DOI：
10.1002/2017ja024919
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发表时间：
2018-02
期刊：
影响因子：
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通讯作者：
Z. Yuan;Xiongdong Yu;Shiyong Huang;Zheng Qiao;Fei Yao;H. Funsten
中科院分区：
文献类型：
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作者：
Z. Yuan;Xiongdong Yu;Shiyong Huang;Zheng Qiao;Fei Yao;H. Funsten
快磁声（MS）波在内磁层的动力学中发挥着重要作用。理论预测和模拟已经证明MS波可以加热冷离子。然而，迄今为止，MS 波加热冷离子的直接观测证据仍然难以捉摸。在本文中，我们通过 2013 年 8 月 22 日范艾伦探测器任务的观测，展示了等离子体层密度腔中磁声波加热冷离子的典型事件。在密度腔中 MS 波强度增强期间，观察到能量为 10-100 eV 的捕获 H+ 和 He+ 离子通量增加，这意味着冷等离子体层离子被加热通过 与 MS 波的高阶共振。基于对环流质子的同步观测，我们计算了局部线性增长率，这表明磁声波可以在密度腔中局部产生。我们的结果为环流与等离子体层之间的能量耦合过程提供了直接的观测证据；即通过激发MS波，释放出具有环分布的环流质子中储存的自由能。在等离子体层的密度腔中，冷 H+ 和 He+ 离子均被 MS 波加热。结果，环形电流的能量可以转移到等离子体层中。
Fast magnetosonic (MS) waves play an important role in the dynamics of the inner magnetosphere. Theoretical prediction and simulation have demonstrated that MS waves can heat cold ions. However, direct observational evidence of cold ion heating by MS waves has so far remained elusive. In this paper, we show a typical event of cold ion heating by magnetosonic waves in a density cavity of the plasmasphere with observations of the Van Allen Probe mission on 22 August 2013. During enhancements of the MS wave intensity in the density cavity, the fluxes of trapped H+ and He+ ions with energies of 10–100 eV were observed to increase, implying that cold plasmaspheric ions were heated through high‐order resonances with the MS waves. Based on simultaneous observations of ring current protons, we have calculated local linear growth rates, which demonstrate that magnetosonic waves can be locally generated in the density cavity. Our results provide a direct observational proof of the energy coupling process between the ring current and plasmasphere; that is, through exciting MS waves, the free energy stored in the ring current protons with ring distributions is released. In the density cavity of the plasmasphere, both cold H+ and He+ ions are heated by MS waves. As a result, the energy of the ring current can be transferred into the plasmasphere.