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首页> 外文期刊>Journal of Geophysical Research, A. Space Physics: JGR >Thin filament simulations for Earth's plasma sheet: Tests of validity of the quasi-static convection approximation
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Thin filament simulations for Earth's plasma sheet: Tests of validity of the quasi-static convection approximation

机译：薄丝模拟地球的等离子体表:准静态的测试效度对流近似

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The main goal of this paper is to estimate the errors involved in applying a quasi-static convection model such as the Rice Convection Model (RCM) or its equilibrium version (RCM-E), which neglect inertial currents, to treat the injection of fresh particles into the inner magnetosphere in a substorm expansion phase. The approach is based on the idea that the dipolarization process involves earthward motion of a bubble that consists of flux tubes that have lower values of the entropy parameter than the surrounding medium. Our tests center on comparing MHD simulations with RCM- and RCM-E-like quasi-static approximations, for cases where the bubble is considered to be a thin ideal-MHD filament. Those quasi-static solutions miss the interchange oscillations that are often a feature of the MHD results. RCM and, to a lesser extent, RCM-E calculations tend to overestimate the westward electric field at the ionospheric footprint of the bubble and underestimate its duration. However, both get the time integral of the E × B drift velocity right as well as the net energization of the particles in the filament. The quasi-static approximation is most accurate if its computed value of the braking time of the bubble's earthward motion is long compared to the period of the relevant interchange oscillation. Comparison of MHD filament simulations of interchange instability with corresponding RCM calculations suggests a similar validity criterion. For plasma sheet conditions, the quasi-static approximation is typically best if the background medium has low β, worst if it consists of highly stretched field lines.
机译：本文的主要目的是估计参与应用静态错误比如大米对流对流模型模型(RCM)或其平衡版本(RCM-E),忽略惯性电流治疗注入新鲜的颗粒进入内部磁层亚暴扩张阶段。方法是基于的想法dipolarization过程包括向地球的运动的泡沫,由磁流管中低熵参数的值周围的介质。磁流体动力仿真与RCM RCM-E-like准静态近似的情况下被认为是薄ideal-MHD泡沫灯丝。交换振荡,往往一个特性磁流体动力的结果。倾向于高估RCM-E计算西在电离层电场足迹的泡沫和低估了它持续时间。E×B以及净漂移速度激发粒子的灯丝。准静态近似是最准确的如果它的制动时间的计算值泡沫的向地面运动是长相比段有关交换振荡。比较磁流体动力灯丝的模拟交换不稳定性与相应的RCM计算表明类似的有效性标准。准静态近似通常是最好的背景中有低β,最差由高度拉伸电场线。

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