六. 地磁与高空大气物理

(负责人：刘振兴 徐文耀 溥祖荫)

The New Development and Application of Geophysical

(Conveners: LIU Zhenxing XU Wenyao PU Zuyin)

1. Observations of Solar-Terrestrial Physics at Zhongshan Station, Antarctica

Liu Ruiyuan, Yang Huigen, Qian Songlin, He Longsong, Liu Yonghua, Hu Hongqiao, Liu Shunlin

（Polar Research Institute of China, Shanghai 200129, China）

Zhongshan Station (69°22¢S, 76°23¢E) is located under the ionospheric projection of the high latitude magnetospheric cusp region, an idea location for Observations of Solar-Terrestrial Physics. A ground-based composite measurement system has been built, which consists of a digisonde DPS-4, a scanning photometer, an all sky TV camera, a surface ozone detector, a fluxgate magnetometer, an imaging riometer, a CCD monochromatic all sky TV camera and an induction magnetometer. Zhongshan Station has become one of the well-equipped stations on solar-terrestrial observations in Antarctica.

The specifications and data records are introduced for each instrument of the composite measurement system. Based on the measurement data from Zhongshan Station, more than 60 papers have been published in recent 5 years. They are mainly dealing with ionospheric properties, ionospheric drift and its response to the IMF condition, post-noon aurora, quasi-periodical auroral phenomena, magnetic pulsation and plasma waves.

Zhongshan Station will make a significant contribution to high latitude ionospheric and magnetospheric studies.

2. Ionospheric absorption at Zhongshan Station, Antarctica

during magnetic storms in early May,1998

Liu Ruiyuan, He Longsong, Hu Hongqiao, Liu Yonghua

(Polar Research Institute of China, Shanghai,200129)

In the paper the high latitude ionospheric absorption events, monitored by an imaging riometer at Zhongshan Station, Antarctica were examined during magnetic storms in early May, 1998. The strong absorption at ~0630UT on May 2 is mainly an equatorward progressing absorption event, which are associated with a strong negative bay of the magnetic H component and with a large Pc3 range pulsation. There was a time lag of about 1.5 hours between the polar ionosphere disturbance and the IMF southward turning in the solar wind. The event at 2222UT on May 2 was a typical midnight absorption spike event. The absorption region takes the form of an elongated strip with the length of 100~150km and the width of 30~40km. The absorption during 0830~1200UT on May 6 is a polar cap absorption (PCA) event, caused by intense radiation of high-energy protons erupted after a large solar flare explosion.

3. Comparisons of the CNA pulsation in Pc5 range between cusp region and auroral zone

Liu Yonghua¹ Liu Ruiyuan¹ He Longsong¹ Yang Huigen¹ Li Shenggui¹

H. Yamagishi² N. Sato² B.J. Fraser³

1.Polar Research Institute of China, Shanghai 200129, China

2. National Institute of Polar research, Tokyo 173, Japan

3.University of Newcastle, Newcastle 2308, Australia

We Analyze the imaging riometer data in 1998 from five stations at both hemispheres, Zhongshan Station (L~14), Antarctica and its conjugate site, Longyearbyen, Svalbard (L~14), Syowa Station (L~6) and its conjugate site, Husafel and Tjornes (L~6) in Iceland, especially for two typical absorption events in Pc5 band on 31 Aug. and 22 Aug,. We Also check the corresponding magnetometer data from Zhongshan, Syowa and Lonyearbyen, and the corresponding IMF data from WIND satellite. Then we get the features of CNA pulsation in Pc5 range in daytime at L~14 and L~6 as follows:

1. At Zhongshan Station, the CNA pulsation in Pc5 range has larger amplitude than that at Longyearbyen. It is explained from the fact that Longyearbyen is located at higher latitude than Zhongshan. For higher latitude, smaller number of particles is trapped in the L shell, and weaker CNA pulsation is expected on the ground.

2. In general, the CNA pulsation has smaller amplitude and occurrence rate at Zhongshan than at Syowa Station. It is explained that Syowa is located in the auroral zone. In the auroral zone, there is a lot of particle precipitation and CNA pulsation will be formed when the precipitation is modulated by the MHD waves in the magnetosphere.

3. At Zhongshan, the CNA pulsation can be caused by solar wind directly. While at Syowa, the CNA pulsation is caused by wave- particle interaction. Since Zhongshan is located under cusp region at local magnetic noon. At cusp region, the solar wind electric field can mapping to ionosphere through opening field line. Then the CAN pulsation can be observed on the ground.

*Supported by Youth Oceanographic Foundation of National Ocean Administration and National Natural Scientific Foundation.

4. Geo-space effects in the polar region caused by Solar storms

during the early November, 1997

Liu Shunlin, He Longsong, Liu Ruiyuan and Liu Yonghua

(Polar Research Institute of China, Shanghai 200129, China)

During November 4 to November 6,1997, two successive X-class solar flare events, together with CME and Ⅱ、Ⅳtype radio bursts, occurred. The intensity of X-ray solar flare attained X9.4 class on November 6, which is the most intense X- ray solar flare in the upward period of solar cycle 23. At 2248UT of 6^th, sudden magnetic storms commence with Dst=-110nT also occurred. In our paper, we analyzed the geo-effective responses of solar storms during the early November of 1997 by using the experimental data of Zhongshan Station, Antarctica. We argued that the sudden commence on November 6 was caused by the CME event （S14W33）on November 4 which the plasma clouds were collide with earth’s magnetosphere directly. However, the CME event （S18W63）on November 6 lied at the western margin of solar surface, so only polar cap absorption events appeared. Our analyses are also consistent with that of Gosling(1993)^[1].The X-ray flare events resulted in the daytime sudden ionosphere disturbance(SID). No apparent convection movement observed. The intensity and duration of absorption are related with those of X-ray flux.