极地研究

极地研究 ›› 2000, Vol. 11 ›› Issue (1-English): 53-58.

• 目次 • 上一篇    下一篇

A study on the multi-component substrom current

 Xu Wenyao1 and Sun Wei2   

  1. 1 Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100101, China;
    2 Geophysical Institute, University of Alaska, Fairbanks, Alaska 99775, USA
  • 出版日期:1950-03-30 发布日期:1950-03-30
  • 通讯作者: Xu Wenyao

A study on the multi-component substrom current

 Xu Wenyao1 and Sun Wei2   

  1. 1 Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100101, China;
    2 Geophysical Institute, University of Alaska, Fairbanks, Alaska 99775, USA
  • Online:1950-03-30 Published:1950-03-30
  • Contact: Xu Wenyao

PDF (PC)

690

摘要：

A new technique of eigen mode analysis, Method of Natural Orthogonal Components (MNOC) is used to analyze the ionospheric equivalent current systems obtained on the basis of magnetic data at six meridian magnetometer chains in the northern hemisphere during March 17-19, 1978. The results show that the whole current pattern for any given instant consists of a few eigen modes with different intensities. The first eigen mode exhibits a two-cell current construction, characterizing the large-scale magnetospheric convection and directly driven process, while the second eigen mode shows a concentrated westward electrojet at midnight sector, characterizing the substorm current wedge and the loading-unloading process. The first mode consistently exists whenever during quiet periods or at substorms, and its intensity increases from the beginning of the growth phase of substorms, then quickly intensifies in the expansion phase, followed by a gradual decrease in the recovery phase. On the other hand, the intensity of the second mode remains to be near zero during both quiet time and the growth phase of substorms. Its rapid enhancement occurs in the expansion phase. These characteristics in the current patterns and the intensity variations coincide with the defined physical processes of the directly driven and loading unloading components.

关键词: substorm, equivalent current system, method of natural orthogonal components (MNOC)

Abstract:

A new technique of eigen mode analysis, Method of Natural Orthogonal Components (MNOC) is used to analyze the ionospheric equivalent current systems obtained on the basis of magnetic data at six meridian magnetometer chains in the northern hemisphere during March 17-19, 1978. The results show that the whole current pattern for any given instant consists of a few eigen modes with different intensities. The first eigen mode exhibits a two-cell current construction, characterizing the large-scale magnetospheric convection and directly driven process, while the second eigen mode shows a concentrated westward electrojet at midnight sector, characterizing the substorm current wedge and the loading-unloading process. The first mode consistently exists whenever during quiet periods or at substorms, and its intensity increases from the beginning of the growth phase of substorms, then quickly intensifies in the expansion phase, followed by a gradual decrease in the recovery phase. On the other hand, the intensity of the second mode remains to be near zero during both quiet time and the growth phase of substorms. Its rapid enhancement occurs in the expansion phase. These characteristics in the current patterns and the intensity variations coincide with the defined physical processes of the directly driven and loading unloading components.

Key words: substorm, equivalent current system, method of natural orthogonal components (MNOC)