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首页> 外文期刊>Journal of Geophysical Research, A. Space Physics: JGR >Magnetic fluctuations embedded in dipolarization inside geosynchronous orbit and their associated selective acceleration of O~+ ions
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Magnetic fluctuations embedded in dipolarization inside geosynchronous orbit and their associated selective acceleration of O~+ ions

机译：嵌入dipolarization磁场波动在地球同步轨道及其相关O ~ +离子的选择性加速度

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We study magnetic fluctuations embedded in dipolarizations in the inner magnetosphere (a geocentric distance of ≤6.6 R_E) and their associated ion flux changes, using the Engineering Test Satellite VIII and Active Magnetospheric Particle Tracer Explorers/CCE satellites. We select seven events of dipolarization that occur during the main phase of magnetic storms having a minimum value of the Dst index less than ?40 nT. It is found that (1) all of the dipolarization events are accompanied by strong magnetic fluctuations with the major frequency close to the local O~+ gyrofrequency; (2) the magnetic fluctuations appear with significant amplitude in the component nearly parallel to the local magnetic field; (3) the strong flux enhancement is seen in the energy range of 1–10 keV only for O~+ ions. In terms of frequency and dominant components of the magnetic fluctuations, they are considered to be excited by the drift-driven electromagnetic ion cyclotron (EMIC) instability that is recently identified with the linear theory. We perform particle tracing for H~+ and O~+ ions in the electromagnetic fields modeled by the linear dispersion relation of the drift-driven EMIC instability. Results show that the O~+ ions are accelerated to the energy range of 0.5–5 keV and undergo a significant modification of the spectral shape, while the H~+ ions have no clear change of spectral shape, being consistent with the observations. We therefore suggest that the electromagnetic fluctuations associated with the dipolarizations can accelerate O~+ ions locally and nonadiabatically in the inner magnetosphere. This selective acceleration of O~+ ions may play a role in enhancing the O~+ energy density in the storm time ring current.
机译：我们研究嵌入在磁场波动dipolarizations内磁层(a地心的距离≤6.6 R_E)和他们的相关的离子通量变化,使用工程试验卫星八世和活跃磁层粒子示踪探险家/ CCE卫星。dipolarization期间发生的主要阶段磁性风暴的最小值Dst指数小于? 40元。发现(1)所有的陪同dipolarization事件通过强大的磁场波动大频率接近当地O ~ +旋转频率;(2)磁场波动出现近显著振幅组件平行于当地磁场;强大的增强的能量通量1 keV范围仅为O ~ +离子。频率和磁场的主要组件波动,他们被认为是兴奋由drift-driven电磁离子回旋(位)最近确认的不稳定与线性理论。跟踪H ~ +和O ~ +离子的电磁场建模的线性的drift-driven特有的色散关系不稳定。加速到0.5 - 5 keV的能量范围进行重大修改光谱的形状,而H ~ +离子没有明确光谱形状的变化,是一致的观察。电磁波动相关在本地dipolarizations可以加速O ~ +离子和nonadiabatically内部磁气圈。这个O ~ +离子的选择性加速度可能玩一个角色在提高O ~ +能量密度风暴时间环电流。

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