Preliminary impulse of the geomagnetic storm sudden commencement of November 18, 1993
Preliminary impulse of the geomagnetic storm sudden commencement of November 18, 1993
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1993年11月18日突然爆发的地磁风暴的初步冲动
DOI：
10.1029/2000ja000226
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发表时间：
2001
影响因子：
--
通讯作者：
J. Watermann
中科院分区：
文献类型：
--
作者：
J. Sastri;T. Takeuchi;T. Araki;K. Yumoto;S. Tsunomura;H. Tachihara;H. Luehr;J. Watermann
利用几个地磁台网的高时间分辨率资料，研究了1993年11月18日1211时30UT长时间静止后发生的地磁突然启动的特征。根据不同经度(当地时间)扇区的同步观测，我们首次给出了赤道附近Sc的H分量的初步反向冲量(PRI)行为的结果。初步的反向冲量只出现在距磁赤道(倾角0.6°)很近的前月(0912LT)区域。在更远的位置(倾角6.0°~7.2°)但在同一经络上，初始反向冲动的幅度减小，并导致SC的主冲动(MI)延迟开始。无论是下午(1300LT)还是接近黄昏(1740LT)，初步反向冲量在靠近磁赤道(倾角1.2°-2.7°)的位置都不明显。相反，这里看到的是H分量增长率的明确减小，与上午扇区的初步反向冲量一致。高频多普勒雷达对黄昏附近磁赤道(倾角4.9°)附近F层等离子体垂直漂移的测量表明，与SC有关的扰动是环境向上漂移的减少，具有相当大的时间结构，这表明电场是向西施加的。初步的反向冲量出现在亚极光至极区(MLAT 56.8°-76°)的午后侧，同时也出现在临空倾角赤道附近，并且在MLAT范围66°-76°范围内，幅度和持续时间随纬度的增加而显著增大。理论计算表明，由一对位于80°纬度的场向电流建立并移动到晨边(中心位于1300和0300LT)的全球海流系统总体上可以解释观测到的初步反向冲量的行为，但在接近黄昏时的赤道倾角区域除外。
The characteristics of the geomagnetic sudden commencement (SC) that occurred at 1211:30 UT on November 18, 1993, following an interval of prolonged geomagnetic quietness are studied using high time resolution data of several magnetometer networks. We present the first results concerning the behavior of the preliminary reverse impulse (PRI) of the H component of the SC near the dip equator from simultaneous observations in different longitude (local time) sectors. It is found that the preliminary reverse impulse appeared only in the prenoon (0912 LT) sector very close to the magnetic equator (dip 0.6°). At locations farther away (dip 6.0°_7.2°) but on the same meridian, the preliminary reverse impulse diminished in amplitude and led to a delayed onset of the main impulse (MI) of the SC. The preliminary reverse impulse is not apparent at locations close to the magnetic equator (dip 1.2°-2.7°) in either the afternoon (1300 LT) or the near-dusk (1740 LT) sectors. What is seen instead here is an unambiguous reduction in the rate of increase of H component coincident with the preliminary reverse impulse in the forenoon sector. HF Doppler radar measurements of F layer vertical plasma drift close to the magnetic equator (dip 4.9°) near the dusk sector showed the SC-related disturbance to be a decrease in ambient upward drift with considerable temporal structure, which indicates the imposition of a westward electric field. The preliminary reverse impulse is seen in the subauroral to polar region (MLAT 56.8°- 76°) on the afternoon side simultaneous with that near the prenoon dip equator and with a conspicuous increase in amplitude and duration with latitude over MLAT range 66°-76°. Theoretical calculations suggest that the global current system set up by a pair of field-aligned currents at 80° latitude and shifted to morningside (centers at 1300 and 0300 LT) could, in general, account for the observed behavior of the preliminary reverse impulse, except in the dip equatorial region near dusk.
影响因子：
5.2
作者：
M. Abdu;J. Sastri;H. Luhr;H. Tachihara;T. Kitamura;N. Trivedi;J. Sobral
通讯作者：
M. Abdu;J. Sastri;H. Luhr;H. Tachihara;T. Kitamura;N. Trivedi;J. Sobral