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首页> 外文期刊>Journal of Geophysical Research, A. Space Physics: JGR >Dipole Tilt Effect on Magnetopause Reconnection and the Steady-State Magnetosphere-Ionosphere System: Global MHD Simulations
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Dipole Tilt Effect on Magnetopause Reconnection and the Steady-State Magnetosphere-Ionosphere System: Global MHD Simulations

机译：偶极子对磁重联倾斜的影响和稳态Magnetosphere-Ionosphere系统:全球磁流体动力模拟

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The Earth's dipole tilt angle changes both diurnally and seasonally and introduces numerous variabilities in the coupled magnetosphere-ionosphere system. By altering the location and intensity of magnetic reconnection, the dipole tilt influences convection on a global scale. However, due to the nonlinear nature of the system, various other effects like dipole rotation, varying interplanetary magnetic field (IMF) orientation, and nonuniform ionospheric conductance can smear tilt effects arising purely from changes in coupling with the solar wind. To elucidate the underlying tilt angle dependence, we perform magnetohydrodynamic (MHD) simulations of the steady-state magnetosphere-ionosphere system under purely southward IMF conditions for tilt angles from 0-90°. We identify the location of the magnetic separator in each case and find that an increasing tilt angle shifts the 3-D X line southward on the magnetopause due to changes in magnetic shear angle. The separator is highly unsteady above 50° tilt angle, characteristic of regular flux transfer event (FTE) generation on the magnetopause. The reconnection rate drops as the tilt angle becomes large, but remains continuous across the dayside such that the magnetosphere is open even for 90°. These trends map down to the ionosphere, with the polar cap contracting as the tilt angle increases, and region I field-aligned current (FAC) migrating to higher latitudes with changing morphology. The tilt introduces a north-south asymmetry in magnetospheric convection, thus driving more FAC in the Northern (sunward facing) hemisphere for large tilt angles than in the Southern independent of conductance. These results highlight the strong sensitivity to onset time in the potential impact of a severe space weather event.
机译：地球的偶极子倾角的变化每日和季节性,介绍了许多在耦合magnetosphere-ionosphere系统。磁场重联的位置和强度,偶极子倾斜对流在全球的影响规模。这个系统,其他各种影响像偶极子旋转,不同的行星际磁场(IMF)取向和非均匀电离层电导可以涂片倾斜产生纯粹的影响从耦合与太阳风的变化。阐明潜在的倾角的依赖,我们执行磁流体动力(磁流体动力)模拟的稳态magnetosphere-ionosphere系统向南纯粹的国际货币基金组织的条件从0 - 90°倾斜角度。在每种情况下,磁分离器和发现这越来越倾角变化3 d X对磁层线向南的变化在磁剪切角。不稳定高于50°倾角,的特点常规通量传输事件(FTE)一代磁层。倾角变大,但仍然存在连续的光面,磁气圈是开放甚至90°。映射到电离层,极地冰冠随着倾角的增加,收缩和地区我field-aligned活期(FAC)迁移高纬度地区和形态学变化。介绍了南北不对称倾斜磁性层的对流,从而导致更多的前沿空中管制官在北方(朝着太阳面临)半球比南方大倾斜角度独立于电导。突出的强烈敏感度起始时间严重的太空天气的潜在影响事件。

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