The Effects of Localized Thermal Pressure on Equilibrium Magnetic Fields and Particle Drifts in The Inner Magnetosphere
The Effects of Localized Thermal Pressure on Equilibrium Magnetic Fields and Particle Drifts in The Inner Magnetosphere
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DOI：
10.1029/2018ja026043
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发表时间：
2019-07
期刊：
影响因子：
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通讯作者：
Z. Xia;Lunjin Chen;A. Artemyev;Hui Zhu;V. Jordanova;Liheng Zheng
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文献类型：
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作者：
Z. Xia;Lunjin Chen;A. Artemyev;Hui Zhu;V. Jordanova;Liheng Zheng
热各向异性等离子体片状粒子局域注入内磁层会使静止时间的类偶极子磁场发生显着变形，从而干扰电子和离子的漂移路径和散射率。虽然可以从经验模型中推断出磁场变形的许多细节，但注入等离子体的不同特性对这种变形结构的作用还需要进一步的研究。本文利用二维轴对称平衡模型计算了具有四个输入参数的高斯型热压分布的力平衡中的自洽磁场：压力峰β_0处的等离子体压力与磁压之比(β_0)、压力峰L_0的径向位置、半峰压σ_0的宽度和赤道气压各向异性Ae。利用模拟的磁场，我们发现磁场扰动随着β0的增大和σ0的减小而增大，而磁曲率扰动随着Ae、β0和σ0的增大以及L0的减小而增大。对于高能粒子，磁梯度漂移运动的变化比曲率漂移运动的变化要大得多。磁倾角结构的形成需要一个临界β值，该值随着σ0的增加和L0的减小而增加。尽管现有文献中没有观测来检验磁倾角形成的条件，但作为未来的研究，这种条件将与观测结果相对照。最后，我们还使用了三维环流-大气相互作用模型和自洽磁场模型来说明与非对称环流相关的方位压力分布的影响。
Localized injections of hot anisotropic plasma sheet particles into the inner magnetosphere can significantly deform the quiet time dipole‐like magnetic field and thus disturb electron and ion's drift paths and scattering rates. Although many details of magnetic field deformation can be inferred from empirical models, roles of different characteristics of injected plasma on the structure of such deformation require further investigation. In this study, we use the 2‐D axisymmetric equilibrium model to calculate self‐consistent magnetic field in force balance with a Gaussian thermal pressure distribution characterized by four input parameters: the ratio between plasma pressure and magnetic pressure (β) at the pressure peak β0, the radial location of the pressure peak L0, the width of the half peak pressure σ0, and the equatorial pressure anisotropy Ae. Using the modeled magnetic field, we find that the magnetic field perturbation increases with increasing β0 and decreasing σ0 while the magnetic curvature perturbation increases with increasing Ae, β0, and σ0 and decreasing L0. For energetic particles the change of magnetic gradient drift motion is much greater than that of curvature drift motion. The magnetic dip structure formation requires a critical β value that increases with increasing σ0 and decreasing L0. Despite the unavailability of observations in the existing literatures to check the condition of magnetic dip formation, such condition will be checked against observations as a future study. Finally, we also use 3‐D ring current‐atmosphere interactions model with self‐consistent magnetic field model to illustrate the effect of azimuthal pressure distribution, which is relevant to asymmetric ring current.