Statistical analysis of interplanetary coronal mass ejections and their geoeffectiveness during the solar cycles 23 and 24

Interplanetary coronal mass ejections (ICMEs) are believed to be the most common and important drivers of the strongest geomagnetic storms. In this work, the geoeffective characteristics of the ICMEs occurred during the last solar cycles 23 and 24 (years 1996-2017) have been studied in detail. The maximum velocity either of the ICME's Sheath region or of the ICME itself, the mean velocity of the ICME, the minimum value of the southward component of the Interplanetary magnetic field Bs and the component of the solar wind convective electric field E=-VxBobserved at L1 point during the pass of the ICME, were used. It was found that, in accordance to past similar studies, the most dominant characteristic of ICMEs in the generation of geomagnetic storms is the Bs component along with the Ey parameter, while the maximum velocity seems to be of less importance. Nevertheless the maximum speed is an good forecasting factor due to the fact that it is much easier to estimate the velocity of an ICME-structure many hours before it arrives at Earth compared with the observations of Bs and Ey that can only be done, for the time being, at the L1 point. That means we can use the velocity of ICME-structure to forecast the possible generation and magnitude of the geomagnetic storms. From a comparison of the ICME-generated geomagnetic storms with the total number of geomagnetic storms generated during the last two solar cycles, it seems that approximately half of the ICMEs (49% for Dst index and 53% for Kp index) produced geomagnetic storms during the solar cycles 23 and 24. Moreover the velocities of ICMEs are more in accordance with the rising and maximum phases of solar cycles 23 and 24 than the geomagnetic activity (storms) are, as well as during the first stages of the declining phases of these cycles, especially during solar cycle 23.