Characteristics of decametric hectometric (DH) type IIs, CMEs and flares of geoeffective and non-geoeffective storm events in Solar Cycle 24

Abstract

In this paper, a statistical study on geoeffectiveness of CMEs integrated with decametric hectometric (DH) type-II radio bursts, association of Dst with plasma and interplanetary field parameters (T,V,P, β, Bz,Bt,E) and their product function BzV for solar cycle 24 is presented. We have selected 119 DH-CME events from March 2008 to December 2015. Based on minimum Dst index ≤‑50 nT of geomagnetic storm, the events are assorted into two groups, specifically (i) Geoeffective events (ii) Non-geoeffective events. The geoeffective events are found to have high start frequency, low end frequency, broad bandwidth, long duration, slower drift rate than non-geoeffective events. CME speed and flare flux for geoeffective events are moderately correlated(r=0.50) which shows that flares may be related to geomagnetic storms through CMEs. Higher speed of CMEs associated with geoeffective events suggests that CME speed is an important parameter for geoeffectiveness. A large fraction of CME associated with DH-type-II radio bursts are linked with geomagnetic storm which again indicates that CMEs accompanied by DH-type-II radio bursts are effectively responsible for producing geomagnetic storms. A good correlation of Dst with BzV(r>0.5) reflects that interplanetary field and plasma parameters also play an important role in the occurrence of geomagnetic storms.