Magnetic Storm Characterizations during Solar Cycle 24 Based on DST and AA Indices

Abstract

We analyzed the occurrence and characteristics of various types of magnetic storms during solar cycle 24. The annual mean total sunspot number (SSN) was used to quantify solar cycle activity. The intensity and classification of magnetic storms, by type and rank, were assessed using two geomagnetic indices: Dst (Disturbance Storm Time Index) and aa (global geomagnetic activity index), respectively. Based on the minimum Dst values, we identified a total of 130 magnetic storm events, comprising 104 moderate and 26 intense storms. Using the maximum aa values, we further classified these events by type and rank. Among them, 54 storms displayed sudden commencement (S-storms), while 76 storms exhibited gradual commencement (G-storms). Additionally, the types of storms were categorized by five ranks. According to established literature, the main common sources of storms are issued from interplanetary coronal mass ejections (ICMEs) and corotating interaction regions (CIRs). Our findings revealed that 76% of storms associated with ICME sources were S-storms, typically occurring near the peak of solar activity. Conversely, 60% of storms related to CIR sources were G-storms, most commonly observed during the declining phase of the solar cycle. This study contributes to the broader understanding of magnetic storm behavior during solar cycle 24, in terms of both intensity and classification. Lastly, we compared the distribution of storms in solar cycle 24 with those of previous cycles to contextualize the overall activity level.