Solar wind magnetic field control of magnetospheric response delay and expansion phase onset timing
Solar wind magnetic field control of magnetospheric response delay and expansion phase onset timing
复制标题
太阳风磁场控制磁层响应延迟和膨胀相位开始定时
DOI：
10.1029/1999ja900013
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发表时间：
1999
影响因子：
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通讯作者：
R. Walker
中科院分区：
文献类型：
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作者：
L. Bargatze;T. Ogino;R. McPherron;R. Walker
利用高分辨率的三维全球磁流体动力学（MHD）模型研究了不同行星际磁场（IMF）条件下磁层响应的变异性。MHD模型响应时间延迟的变化是通过执行基于IMF Bz分量强度的参数搜索来发现的，该分量在向南转弯之前和之后保持恒定4小时。参数搜索表明，增长阶段持续时间的变化，以及扩张阶段开始时间的变化，遵循一个简单的模式，由IMF Bz在向南转向前后的相对优势所支配。如果向北和向南的IMF值大小相等，则在日侧合并开始后约60分钟开始膨胀阶段。然而，如果北方向的IMF设置比随后的南向场强小（大），则扩张阶段的开始可能会在更短（更长的）时间延迟后发生。从模拟中发现的开始延迟时间范围为~ 60±30分钟。由于对流系统和亚风暴流楔的太阳风响应时间尺度不同，假设以AL指数为代表的磁层太阳风响应是双峰的，通过实证分析对MHD结果进行了验证。实证分析利用太阳风输入时间序列和相应的AL指数数据等短持续时间间隔。实验结果与MHD模拟结果吻合较好。
Variability in the response of the magnetosphere under different interplanetary magnetic field (IMF) conditions is investigated by utilizing a high-resolution, three-dimensional, global magnetohydrodynamic (MHD) model. Changes in the MHD model response time delay are found by performing a parameter search based on the strength of the IMF Bz component, which is held constant for 4 hours prior to and following southward turnings. The parameter search reveals that variations in the growth phase duration and, thus in the timing of expansion phase onset, follow a simple pattern governed by the relative strengths of IMF Bz before and after the southward turnings. If the IMF northward and southward values are equal in magnitude, the expansion phase onset occurs ∼60 min after dayside merging begins. However, if the north IMF setting is smaller (larger) than the subsequent southward field intensity, the expansion phase onset can occur after a much shorter (longer) time delay. The range of onset delay times found from the simulation is ∼60±30 min. The MHD results are tested by means of an empirical analysis, which is based on the assumption that the solar wind response of the magnetosphere, as represented by the AL index, is bimodal, owing to the different solar wind response timescales of the convection current system and the substorm current wedge. The empirical analysis utilizes short duration time intervals including solar wind input time series and corresponding AL index data. The empirical results agree favorably with the results found via MHD simulation.
影响因子：
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作者：
T. Ogino
通讯作者：
T. Ogino