2000年4月磁暴期间武汉地区F电离层突然抬升现象

２０００年４月６－７日的大磁暴（Ｄｓｔ最小值达到－３１７ｎＴ），急始（ＳＳＣ）在６月１６４０ＵＴ左右出现，随后磁暴主相开始，约在７月００１３ＵＴ进入恢复相。磁暴主相前期武汉地区Ｆ区电离层出现「突然抬高现象，在２ｈ内ｈ’Ｆ和ｈｍＦ２分别较暴前日增加约２００ｋｍ。此期间台湾中沥也几乎同时也现了Ｆ区电离层突增现象。磁暴主相前期ｆ０Ｆ２较暴前日下降１．６ＭＨｚ，其变化幅度在ｆ０Ｆ２逐日变化起伏范围内，但７

THE LARGE NIGHTTIME INCREASE IN IONOSPHERIC HEIGHTS AT WUHAN DURING THESTORM OF APRIL 2000

A great geomagnetic storm occurred around 1640 UT on April 6, 2000, with a Value of -317nT in Dst index. The responses of the ionosphere at Wuhan during the first stage of this storm were reported in this paper. Soon after the sudden storm commencement (SSC) at 1640 UT, the main phase of the geomagnetic storm appeared, and the storm stepped into its recovery phase at the beginning of the next day. A rapid and large increase in the ionospheric heights at Wuhan occurred at the beginning of the main phase, and the lifts in h'F and hmF2 lasted for about 2 hours. The value of f0F2 decreased about 1.6 MHz at the beginning of the main phase, and the maximum value of f0F2 on the next day was less than that on April 5 more than 3 MHz at Wuhan. The almost simultaneous increase in h'F was also observed at Chungli, Taiwan. The near simultaneity of the h'F disturbances at the two stations suggested that an E x B plasma drift due to an east-west electric field of storm origin was the cause of the rapid and large lifts in the nighttime ionospheric heights after the SSC.