The polar ionosphere at Zhongshan Station on May 11, 1999, the day the solar wind almost disappeared  

作　　者：胡红桥 刘瑞源 刘勇华 杨惠根 刘顺林 张北辰 艾勇 N. Sato B. J. Fraser 

机构地区：[1]Polar Research Institute of China, Shanghai 200129, China [2]College of Electronic Information, Wuhan University, Wuhan 430072, China [3]National Institute of Polar Research, Tokyo 173, Japan [4]Department of Physics, University of Newcastle, Australia

出　　处：《Science China Mathematics》2002年第z1期161-166,共6页中国科学：数学（英文版）

基　　金：the National Natural Science Foundation of China (Grant Nos. 40104009, 40074038);the Major Scientific Project of Chinese Academy of Sciences (655951-1-305);the National Social Commonweal Program (2001DIA50040-04); the Youth Foundation of the State Oceanic Administration of China (2000903).

摘　　要：The solar wind almost disappeared on May 11,1999: the solar wind plasma density and dynamic pressure were less than 1cm^(-3) and 0.1 nPa respectively, while the interplanetary mag- netic field was northward. The polar ionospheric data observed by the multi-instruments at Zhong- shan Station in Antarctica on such special event day was compared with those of the control day (May 14). It was shown that geomagnetic activity was very quiet on May 11 at Zhongshan. The magnetic pulsation, which usually occurred at about magnetic noon, did not appear. The iono- sphere was steady and stratified, and the F_2 layer spread very little. The critical frequency of day- side F_2 layer, f_0F_2, was larger than that of control day, and the peak of f_0F_2 appeared 2 hours earlier. The ionospheric drift velocity was less than usual. There were intensive auroral E_s appearing at magnetic noon. All this indicates that the polar ionosphere was extremely quiet and geomagnetic field was much more dipolar on May 11. There were some signatures of auroral substorm before midnight, such as the negative deviation of the geomagnetic H component, accompanied with auroral E_s and weak Pc3 pulsation.The solar wind almost disappeared on May 11,1999: the solar wind plasma density and dynamic pressure were less than 1cm-3 and 0.1 nPa respectively, while the interplanetary magnetic field was northward. The polar ionospheric data observed by the multi-instruments at Zhongshan Station in Antarctica on such special event day was compared with those of the control day (May 14). It was shown that geomagnetic activity was very quiet on May 11 at Zhongshan. The magnetic pulsation, which usually occurred at about magnetic noon, did not appear. The ionosphere was steady and stratified, and the F2 layer spread very little. The critical frequency of dayside F2 layer, foF2, was larger than that of control day, and the peak of foF2 appeared 2 hours earlier. The ionospheric drift velocity was less than usual. There were intensive auroral Es appearing at magnetic noon. All this indicates that the polar ionosphere was extremely quiet and geomagnetic field was much more dipolar on May 11. There were some signatures of auroral substorm before midnight, such as the negative deviation of the geomagnetic H component, accompanied with auroral Es and weak Pc3 pulsation.

关 键 词：solar wind  Antarctica  ZHONGSHAN Station  polar ionosphere  GEOMAGNETIC pulsation. 

分 类 号：P182[天文地球—天文学]