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1999年5月11日太阳风几乎消失,其等离子体密度不到1 cm~(-3),动压不到0.1nPa,而行星际磁场持续北向.对这一特殊事件日和控制日(1999年5月14日)南极中山站极区电离层多手段观测结果进行了对比分析.结果表明中山站在1999年5月11日地磁活动极为宁静,通常在地磁当地时的中午前后出现的地磁脉动在这一天几乎没有;电离层成层明显而稳定,F_2层扩展很小;日侧F_2层临界频率明显高于控制日,且f_oF_2的峰值早约2 h出现;电离层漂移速度有所减小;在地磁当地时的中午附近出现了很强的极光E层,这一切都说明极区电离层异常平静,地磁场的偶极化更为明显.但子夜前出现有类似极光亚暴的征兆,如地磁H分量明显的负扰,同时伴随着极光E_s和微弱的Pc_3脉动等
On May 11, 1999, the solar wind almost disappeared with a plasma density of less than 1 cm -3 and a dynamic pressure of less than 0.1 nPa, while the interplanetary magnetic field continued northward. For this special event day and control day (1999 May 14) The results of observational results of multiple observations in the polar region of the Zhongshan Station in the Antarctic show that the geomagnetic activity in Zhongshan Station was extremely quiet on May 11, 1999. The geomagnetic pulsations usually occurred around noon in the geomagnetic time There was almost no ionosphere stratification; the F_2 layer was very small; the critical frequency of F_2 layer on day was obviously higher than that of control day, and the peak value of f_oF_2 appeared about 2 h earlier; the ionospheric drift velocity decreased slightly; A very strong aurora E layer appeared near noon in the geomagnetic area, all of which showed that the polar ionosphere was extremely calm and the dipole of the geomagnetic field was more obvious, but similar signs of auroral subplot appeared before midnight, Geomagnetic H component obvious negative interference, accompanied by Aurora E_s and weak Pc_3 pulse, etc.