地磁活动指数Vr的时空分布特征分析

本文使用2008—2010年三年内的国内41个地磁台站和国外4个地磁台站的地磁水平分量H和磁偏角D的分钟值数据,研究了H和D的Vr指数(以下简称VrH和VrD)与Kp指数的关系及其时空分布特征,发现在时间变化上,VrH和VrD均具有27天太阳自转周变化;VrD呈现出显著的季节变化,而VrH却无,但与太阳风速度(SWS, Solar Wind Speed)变化密切相关,其三年的相关系数分别是0.97、0.70、0.88;去除季节变化后的VrD也表现出与SWS的相关,相关系数分别是0.96、0.77、0.5(2010年相关系数低主要受3月份Vr指数不明原因异常变化影响).在空间变化上,在我国大陆范围内,VrH和VrD均随纬度的增高而增大,并且具有地方时效应和显著的晨-昏不对称性,这种地方时效应和晨昏不对称性可能与部分环电流和场向电流有关系.研究认为Vr指数可以反映地磁场的快速变化,并可以间接反映SWS、部分环电流和场向电流对地磁场变化的影响和控制作用.

Analysis of the temporal-spatial distribution characteristics of geomagnetic activity index Vr

Based on the analysis of Vr index of H and D(VrH and VrD) from data of 41 geomagnetic observatories in China and 4 geomagnetic observatories abroad in 2008—2010,both temporal and spatial variation characteristics of VrH and VrD were observed.For temporal variations,the VrH and VrD showed 27-day solar rotation recurrences,and the VrD showed significant seasonal variation while the VrH did not,VrH was related to solar wind speed(SWS),and their correlation coefficients were 0.97,0.70 and 0.88.VrD with seasonal variation removed was also related to SWS,and their correlation coefficients were 0.96,0.77,and 0.5(The low relative coefficient in 2010 was affected by unexplained anomaly change of Vr in March).For spatial variations,within mainland China,VrH and VrD also increased with latitude.Meanwhile both local-time dependences and an obvious dusk-dawn asymmetry existed,which might be related to the asymmetric ring current,the partial ring current and the field-aligned current.The studies suggested that Vr index could be used for illustrating fast variation of geomagnetic field,and revealing the impact of SWS,partial ring current and field-aligned current on geomagnetic field.