行星际扰动对地磁活动的影响

Effect of interplanetary disturbances on magnetic activities

利用第23太阳活动周中WIND和ACE资料,统计分析行星际扰动对不同水平地磁活动的影响,研究磁暴强度与不同行星际参数之间的相关性,结果发现:①从长期来看,地磁活动指数Dst与太阳风速度的相关性最好,相关性在太阳活动谷年时最高;②多磁暴时序叠加结果证实了导致小、中、强磁暴开始的经验行星际南向磁场条件,磁暴过程中行星际磁场B_z分量、行星际晨昏向电场E_y和Akasofu函数ε的极值出现在Dst最小值前1—3小时之间。个例分析表明,大约90%的弱磁暴、80%的中级磁暴和70%的强磁暴与经验标准相符,引起磁暴的因子中B_z强度的贡献大于其持续时间。B_z<-25 nT是第23太阳活动周中产生大磁暴的充要条件;③磁暴强度与E_y、B_z、ε的相关性很好,相关系数分别达-0.812、0.781和-0.743。E_y和ε与强磁暴相关性最好,B_z与磁暴的相关性随磁暴强度增加而增大。在所有参数中,强磁暴与E_y,大磁暴与B_z的相关性最好。弱磁暴强度与行星际参数的相关性很小。

In this paper, the effect of interplanetary disturbances on magnetic activities of different intensities is analyzed, and the correlations of different interplanetary parameters with the Dst index are shown through statistical analysis of the interplanetary magnetic field data and plasma data from the WIND and ACE spacecrafts during the 23rd solar cycle. The results are as follows： （1） In the long term, of all the interplanetary parameters, the solar wind velocity is the one that correlates best with the Dst index, and the long-term statistical correlation coefficients between them are found to vary during the solar cycle, which are highest during solar minimum. （2） Superposed epoch analyses of storms show that the intensities of south- ward interplanetary magnetic fields which lead to the weak, moderate, or strong storms conform to earlier researches, and that the time at which the B, component of interplanetary magnetic field gets to its minimum, the interplanetary dawn-dusk electric field Eu and the Akasofu energy coupling function ε reach their maximum are ahead of 1--3 hours than that the Dst gets to its minimum during the whole storm. When each storm is analyzed, results show that interplanetary conditions during the 90% weak storms, the 80% moderate storms and the 70% intense storms conform to the experience criterions, and the importance of the intensity of Bz is greater than that of the duration At in creating storms. The condition that Bz-25 nT is necessary and sufficient for creating severe storms. （3） Intensities of storms correlate well with Ey, Bz and ε, and correlation coefficients between the Dst index and Ey, Bz, e are --0. 812, 0. 781, -0. 743, respectively. Ey and e correlate best with intensities of intense storms. The higher intensities of storms are, the higher correlative relationships between Bz and the Dst index are. Of all the interplanetary parameters, Ey is the one that correlates best with intensities of intense storms, while Bz is the one that correlates best with intensities of severe storms. The intensity of weak storms correlates weakly with all the interplanetary parameters.