Long‐period magnetospheric‐ionospheric perturbations during northward interplanetary magnetic field
Long‐period magnetospheric‐ionospheric perturbations during northward interplanetary magnetic field
复制标题
北行行星际磁场期间的长周期磁层-电离层扰动
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
W. Hughes
中科院分区：
文献类型：
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作者：
Chaosong Huang;G. Sofko;A. Koustov;J. MacDougall;R. Greenwald;J. Ruohoniemi;J. Villain;M. Lester;J. Watermann;V. Papitashvili;W. Hughes
在本文中，我们提出的观测结果的长周期磁层电离层扰动期间向北行星际磁场（IMF）。1998年11月10日至11日，IMF北上29小时。太阳风和IMF参数相对稳定。在IMF向北飞行14小时后，冰岛西部高频雷达在午夜/黎明后的扇区观测到了强烈的电离层速度（或电场）扰动。速度扰动的周期范围为50-60分钟，平均值为-54分钟。超级双极光雷达网观测到了电离层对流的周期性变化。在每个循环中，磁纬70 °附近的磁地方时0200左右形成一个大尺度对流单体，并持续发展约30 min，然后以平均速度-1.4km·s-·向东移动。细胞焦点的最终位置在0600 MLT附近的磁纬77 °。地面磁力仪记录到弱磁扰动，在午夜前和午夜后的部门周期为50-60分钟。GOES 8卫星还在夜侧L-6处观测到了具有类似周期的磁层磁场扰动。观测到对流振荡的卫星和关键雷达几乎是磁共轭的，因此卫星和雷达数据之间良好的时间相关性表明磁层和电离层扰动具有共同的来源。我们认为磁层-电离层扰动起源于磁层。在向北的IMF期间，磁层尾部从扩展到更偶极形状的转变与40-60 min周期的全球尾部振荡有关，这些振荡最终导致在X=-10 Re附近产生场向电流和夜侧电离层对流涡旋。如果所提出的机制是正确的，它将有可能推断出的磁层腔的形状从测量周期的尾部振荡在向北IMF。
In this paper we present observations of long-period magnetospheric-ionospheric perturbations during northward interplanetary magnetic field (IMF). On November 10-11, 1998, the IMF was northward for 29 hours. The solar wind and IMF parameters were relatively steady. After the IMF had been northward for 14 hours, strong ionospheric velocity (or electric field) perturbations were observed by the Iceland West HF radar in the postmidnight/dawn sector. The velocity perturbations showed periods in the range 50-60 min, with a mean value-54 min. The Super Dual Auroral Radar Network observed periodic changes of nightside ionospheric convection. For each cycle a large-scale convection cell formed around 0200 magnetic local time (MLT) near magnetic latitude 70 o and grew for-30 min. The convection cell then moved eastward with a mean velocity of-l.4 km s-•. The final position of the cell focus was around 0600 MLT near magnetic latitude 77 o. Ground magnetometers recorded weak magnetic perturbations with periods 50-60 min in both the premidnight and postmidnight sectors. The GOES 8 satellite also observed magnetospheric magnetic field perturbations with similar periods at L-6 on the nightside. The satellite and the key radars which observed the convection oscillations are nearly magnetically conjugate, so the good temporal correlation between the satellite and radar data indicates that the magnetospheric and ionospheric perturbations have a common source. We propose that the magnetospheric-ionospheric perturbations originated within the magnetosphere. The transformation of the magnetospheric tail from an extended to a more dipolar shape during northward IMF is associated with 40-60 min period global tail oscillations which ultimately result in the generation of field-aligned currents and nightside ionospheric convection vortices near X=-10 Re. If the proposed mechanism is correct, it will be possible to infer the magnetospheric cavity shape from the measured periodicity of the tail oscillations during northward IMF.