Interplanetary origin of intense geomagnetic storms (Dst < - 100 nT) during solar cycle 23

Abstract

We study the interplanetary causes of intense geomagnetic storms (Dst < - 100 nT) that occurred during solar cycle 23 (1997-2005). It was found that the most common interplanetary structures leading to the development of an intense storm were: magnetic clouds, sheath fields, sheath fields followed by a magnetic cloud and corotating interaction regions leading high speed streams. However, the relative importance of each of those driving structures was found to vary with the solar cycle phase. We divide the cycle in three phases (rising, maximum and declining) and explain the differences. We also discuss about the geoeffectiveness of each of the four main interplanetary driving structures. Copyright 2007 by the American Geophysical Union.