等离子体片离子与太阳风及地磁条件的关联研究  

Correlation study of plasmasheet ions with solar wind and geomagnetic conditions

作　　者：郑玲[1] 傅绥燕[1] 王永福[1] 何建森[1] 杨彪[1] 

机构地区：[1]北京大学地球与空间科学学院,空间物理与应用技术研究所,北京100871

出　　处：《地球物理学报》2009年第12期2931-2942,共12页Chinese Journal of Geophysics

基　　金：国家自然科学基金(40425004);国家重点基础研究发展计划(2006CB806305)项目资助.

摘　　要：本文根据搭载于Cluster卫星的CIS/CODIF和RAPID仪器的观测数据,统计研究了等离子体片中的H^+、O^+离子在磁暴期间的时间变化特性,及其对太阳风条件的响应.观测结果表明:(1)磁暴开始前,O^+离子(0～40 keV)数密度保持在较低水平.随着磁暴的发展,O^+数密度缓慢上升,其峰值出现在Dst极小值附近;H^+离子(0～40 keV)数密度在磁暴开始之前的较短时间迅速增加并达到峰值,在磁暴开始之后迅速降低,并在整个主相和恢复相期间保持在相对较低水平.更高能量的离子则在磁暴开始后迅速增多,并在低能O^+离子达到峰值之前达到峰值.因此我们推测磁暴初期从等离子体片注入环电流的主要是H^+离子,主相后期O^+离子可能扮演更为重要的角色.(2)在地磁活动时期,太阳风密度和动压强与等离子体片中的H^+、O^+数密度存在一定相关性.等离子体片中的H^+离子对北向IMF B_z较为敏感,而IMF B_z南向条件下更有利于太阳风参数对等离子体片中O^+数密度的影响.在地磁活动平静期,太阳风条件对等离子体片中的离子没有明显影响.Observations obtained from CIS/CODIF and RAPID instrument onboard Cluster are used to investigate the temporal behavior of H＋ and O＋ ions in the storm time plasmasheet and the relationship between plasmasheet ions and solar wind conditions. It is found that： （1） The number density of O＋ ions （0~40 keV） is quite low before SSC, and increases slowly as Dst decreases, reaching its peak value at the vicinity of Dst minimum. The density of H＋ ions enhances greatly shortly before SSC, and decreases sharply after SSC. It keeps at a relatively low level during the whole main phase and recovery phase. Fluxes of energetic H＋ and O＋ ions enhance greatly after SSC and reach their maximum values before their low energy counterparts. It implies that ions injected into ring current at early storm time are mainly H＋ ions and only at later times O＋ ions could significantly affect the ring current. （2） During geomagnetic active times, solar wind pressure, density and electric field are positively correlated with simultaneous H＋ and O＋ number density in the plasma sheet. The dependence of H＋ number density on solar wind parameters is stronger under northward IMF （Interplanetary Magnetic Field）, while O＋ number density favors southward IMF. During geomagnetic quiet times, there is no clear evidence for a correlation between solar wind conditions and ions in the plasmasheet.

关 键 词：等离子体片离子 磁暴 太阳风参数 行星际磁场 

分 类 号：P353[天文地球—空间物理学]