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 current on geomagnetic field.