不同起源地磁扰动期间极光沉降能量的统计研究

尽管对极光沉降能量(HP)的研究已经开展很久,但是关于不同行星际扰动源对HP影响的研究仍然很少.本文基于2001—2008年NOAA极轨卫星数据,对三类不同扰动源,即盔状冕流共转相互作用区(CIRs)、伪冕流CIRs和行星际日冕物质抛射(ICMEs)驱动的中等磁暴期间HP的变化进行时序叠加统计分析,讨论了相关太阳风背景参数、地磁活动强度以及耦合函数的有效性;研究了三类磁暴事件期间HP的南北半球不对称性.结果表明,在磁暴之前盔状冕流CIR磁暴的HP明显低于伪冕流CIR磁暴和ICME磁暴,盔状冕流"磁暴前的平静期"与Newell耦合函数关系密切,而与Russell-McPherron效应关系较小.盔状冕流CIR磁暴主相HP高于伪冕流CIR磁暴和ICME磁暴,可能与盔状冕流相应行星际|Bz|和太阳风数密度均较高有关.此外,在Kp≤4时,冬夏季半球HP的差别随着Kp增加而增加,相应的变化规律符合电导率反馈机制的预测;在Kp>4时,盔状冕流磁暴和ICME磁暴冬季半球的HP大于夏季半球的,伪冕流磁暴事件夏季半球的HP大于冬季半球的或与冬季半球的相近.

Auroral hemispheric power during geomagnetic storms driven by different interplanetary disturbances

Although it has been a long time since the beginning of research on the auroral hemispheric power (HP), less has been done on the differences of HP among storms driven by different interplanetary disturbances. According to different drivers, all the storm events during 2001—2008 are divided into three categories, namely helmet streamer corotating interaction regions (CIRs), pseudostreamer CIRs and interplanetary coronal mass ejection(ICMEs) driven events. A superposed epoch analysis is performed to investigate the relative differences of HP during geomagnetic storms driven by different disturbances. The background solar wind parameters, geomagnetic activity and the effectiveness of coupling function have been studied. In addition, we have investigated the hemispheric asymmetry of HP in the three types of storms. The statistic results show that HP favors storms driven by pseudostreamer CIRs and ICMEs than storms driven by helmet streamer CIRs before the storm onset. It is inferred that the occurring of the so-called "calm before the storm" effect is less correlated with the Russell-McPherron effect, but might be a result of the Newell coupling function. The maximum of HP during helmet streamer CIR storms is greater than that during pseudostreamer CIR and ICME storms. The possible reason is larger interplanetary magnetic field component |B_z| and higher solar wind number density related to helmet streamer CIRs. The difference value of HP between two hemisphere(winter minus summer) increases with Kp when Kp is less than or equal to 4, which is consistent with the prediction of the ionospheric conductivity feedback model. For Kp>4, HP favors winter hemisphere during storms driven by helmet streamer CIRs and ICMEs, but summer HP is larger or close to winter HP during storms driven by pseudostreamer CIRs.