A comparison between the geoeffectiveness of north-south and south-north magnetic clouds and an associated prediction

摘要

Using 1995–2015 Wind in situ solarwind plasma and magnetic field data, 217magnetic clouds (MCs) were identified. The following pertinent results were found: (i) 120 MCs were N-S type (northward→southward, magnetic field, B rotated from northward to southward), and 97 MCs are S-N type. (ii) S-N MC_(S-N) dominated N-SMCN-S in the periods of 1995–1999, 2001–2002, and 2014–2015. In contrast, N-S MCN-S dominated S-NMC_(S-N) in the periods of 2000 and 2003–2013. (iii) The averages of storm intensity () were -69, -57, and -84 nT for “all 217 MCs,” “120 N-S MCs,” and “97 S-N MCs” types, respectively. (iv) Confirmed with observations, MC type depends on the phase of the magnetic solar cycle. Hence, on average, the S-N types trigger more severe storms (i.e., Dst_(min)<-100 nT). Also, from 1995 to 2009, the percentage of N-S types of MCs keeps increasing and the percentage of S-N types decreasing. The percentage of S-N MCs starts increasing in the interval of 2010–2015. Therefore, we expect to see a predominance of the S-N types of MC for the coming few years. This means on average that more severe geomagnetic storms are expected in the near future. This is an interesting solar wind feature and is going to be stressed in its application to “space weather predictions.”