Anomalous sudden commencement on March 24, 1991
Anomalous sudden commencement on March 24, 1991
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DOI：
10.1029/96ja03637
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发表时间：
1997-01
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影响因子：
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通讯作者：
T. Araki;S. Fujitani;M. Emoto;K. Yumoto;K. Shiokawa;T. Ichinose;H. Luehr;D. Orr;D. Milling;H. Singer;G. Rostoker;S. Tsunomura;Y. Yamada;C. Liu
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文献类型：
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作者：
T. Araki;S. Fujitani;M. Emoto;K. Yumoto;K. Shiokawa;T. Ichinose;H. Luehr;D. Orr;D. Milling;H. Singer;G. Rostoker;S. Tsunomura;Y. Yamada;C. Liu
1991年3月24日发生了一次异常地磁突然开始（SC），其特点是在中低纬度地区沿正午子午线观察到异常大而尖锐的脉冲。 SC 的分析是利用来自西太平洋 210° 子午线磁力计链、英国和斯堪的纳维亚半岛南部的亚极光磁力计网络 (SAMNET)、斯堪的纳维亚北部和斯瓦尔巴群岛的 EISCAT 十字磁力计、加拿大 Canopus 的高时间分辨率数字数据以及其他地面和卫星（GOES 6、GOES 7、CRRES 和 GMS）数据进行的。分析结果表明，在低纬度地面站观测到的脉冲是由短持续时间（小于1分钟）的强磁层压缩的传播引起的，这在该事件之前从未观测到过。京都当地中午附近的高频多普勒观测似乎与传播压缩磁脉冲相关的双极电场的存在相一致。 SAMNET站和CRRES在清晨也检测到正脉冲，该脉冲比中午区域的脉冲延迟了30-50秒。尽管地面上观察到的脉冲峰值时间的延迟与电离层磁波以有限速度从白天向黑夜传播一致，但地面上脉冲的初始起始时间在各处几乎是同时的，表明电离层下方存在“几乎瞬时”的传播模式。
An anomalous geomagnetic sudden commencement (SC) occurred on March 24, 1991. It is characterized by an exceptionally large and sharp impulse observed in its initial part along the noon meridian in middle and low latitudes. The analysis of the SC was made by using high time resolution digital data from the 210° Meridian Magnetometer Chain in the west Pacific, Sub‐Auroral Magnetometer Network (SAMNET) in the United Kingdom and southern Scandinavia, the EISCAT Magnetometer Cross in northern Scandinavia and Svalbard, and Canopus in Canada together with other ground and satellite (GOES 6, GOES 7, CRRES, and GMS) data. The results of the analysis suggest that the pulse observed at lower‐latitude ground stations was caused by the propagation of a strong magnetospheric compression of short duration (less than l min) which has never been observed before this event. The HF Doppler observation in Kyoto near local noon seems to be consistent with existence of the bipolar electric field associated with the propagating compressional magnetic pulse. The SAMNET stations and CRRES in the early morning also detected positive pulses which delays 30–50 s from the pulses in noon sector. Although the delay in the peak time of the pulse observed on the ground is consistent with ionospheric hydromagnetic wave propagation from the dayside to the nightside with finite speed, the initial onset time of the pulse on the ground was almost simultaneous everywhere suggesting the existence of an “almost instantaneous” propagation mode below the ionosphere.