A study of magnetotail dynamics during substorms using high-time resolution data

使用高时间分辨率数据研究亚暴期间的磁尾动力学

• 批准号: 13640449
• 负责人: SHIOKAWA Kazuo
• 金额: $ 1.34万
• 依托单位: Nagoya University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2001
• 资助国家: 日本
• 起止时间: 2001 至 2003
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13640449/
• 关键词: magnetosphere; substorm; magnetic perturbation; inner magnetosphere; neutral sheet; magnetic reconnection

We have investigated various characteristics of magnetic and plasma fluctuations for 21 events of substorm-associated near-Earth dipolarization at Xgsm=-8 --11 Re and |Ygsm|<5 Re, using high-time-resolution data for the magnetic field (1/16 s), plasma moment (12 s), and electric field (3 s) measured by the GEOTAIL satellite in 1995-2000. The dipolarizations are always accompanied by intense fluctuations of the magnetic field. The amplitude of the fluctuations is larger for smaller B (closer to the cross-tail current sheet). We found several events in which the magnetic field elevation angles decreased rapidly prior to the dipolarization (explosive growth phase (EGP)-like features). The magnetic fluctuations are not sinusoidal curves but are spikes of a sudden decrease and increase with a time scale of seconds. In quite a few cases, the fluctuations are accompanied by Earthward convective plasma flow. The spectral shape of the fluctuations has a steeper slope (f^-2.7) at 1.0-0.2 Hz than at 0.01-0.2 Hz (f^-2.0). From the correlation between plasma velocity and magnetic field fluctuations, we estimate the parallel scale sizes of waves with periods of 60 s and 15 s to be about 10 Re and 5 Re, respectively. For the 60-s waves, the magnetic and plasma pressure variations are clearly anti-phase. The total pressure tends to decrease gradually before the dipolarization and increase during and after the dipolarization.

我们研究了21个与亚暴有关的近地偶极事件的磁场和等离子体涨落的各种特征，|Ygsm| <5 Re，使用GEOTAIL卫星1995-2000年测量的磁场（1/16 s）、等离子体矩（12 s）和电场（3 s）的高时间分辨率数据。偶极化总是伴随着磁场的剧烈波动。对于较小的B（更接近交叉尾电流片），波动的幅度更大。我们发现了几个事件，其中磁场仰角迅速下降之前的双极化（爆炸性增长阶段（EGP）的功能）。磁场波动不是正弦曲线，而是以秒为时间尺度突然减小和增加的尖峰。在相当多的情况下，波动伴随着向地球的对流等离子体流。波动的频谱形状在1.0-0.2 Hz的斜率（f^-2.7）比在0.01-0.2 Hz的斜率（f^-2.0）更陡。根据等离子体速度与磁场涨落的相关性，我们估计周期为60 s和15 s的波的平行尺度分别约为10 Re和5 Re。对于60-s波，磁场和等离子体压力的变化明显是反相的。总压在偶极化之前逐渐减小，在偶极化期间和之后逐渐增大。

项目成果

Shiokawa, K.: "Bi-directional electrons in the near-Earth plasma sheet"Annales Geophysicae. 21. 1497-1507 (2003)

Shiokawa, K.：“近地等离子体片中的双向电子”地球物理学年鉴。

Shiokawa, K., W.Baumjohann, G.Paschmann: "Bi-directional electrons in the near-Earth plasma sheet"Ann.Geophys.. 21. 1497-1507 (2003)

Shiokawa, K.、W.Baumjohann、G.Paschmann：“近地等离子体片中的双向电子”Ann.Geophys.. 21. 1497-1507 (2003)

Shiokawa, K.: "Multiple auroral brightenings and associated Pi 2 pulsations"Geophysical Research Letters. 29(No.11). 2001GL014583 (2002)

Shiokawa, K.：“多次极光增亮和相关的 Pi 2 脉动”地球物理研究快报。

Shiokawa, K., I.Shinohara, T.Mukai, H.Hayakawa: "Substorm-associated magnetic field fluctuations around X=-10 Re"Proceeding of the 6th International Conference on Substorms. 318-325 (2002)

Shiokawa, K.、I.Shinohara、T.Mukai、H.Hayakawa：“X=-10 Re 附近的亚暴相关磁场波动”第六届国际亚暴会议论文集。

Shiokawa, K.: "Substorm-associated magnetic field fluctuations around X=-10Re"Proceeding of the 6th International Conference on Substorms. 318-325 (2002)

Shiokawa, K.：“X=-10Re 周围的亚暴相关磁场波动”第六届国际亚暴会议记录。