Comparison of geomagnetic storm and non-storm periods mid-latitude Pc1 pulsations characteristics

Abstract

Pc1 pulsations are infrequently observed at mid-latitude ground stations. Previous studies have shown that these pulsations near the ground are commonly observed during dawn and geomagnetic storms, particularly in the storm recovery phase. However, few studies have directly compared the characteristics of Pc1 pulsations during storm and non-storm times using long-term ground-based data. In this study, we conducted a comparative analysis of storm-related and non-storm-related Pc1 pulsations detected at a mid-latitude ground station located at Bohyun mountain in Korea (BOH, L~1.34). Our findings reveal notable distinctions between the two groups. Pc1 pulsations during the non-storm period exhibit a sharper peak in the local time distribution of the occurrence, relatively well indicating daytime wave power attenuation during propagation. Additionally, during the non-storm period, Pc1 pulsations show relatively lower frequencies (0.6~1 Hz) with predominantly linear polarization. In contrast, storm-related Pc1 pulsations exhibit higher and broader frequencies (up to 3 Hz) with more frequent left-handed polarization. These results suggest that storm-related Pc1 pulsations might originate from a more diverse range of spatial sources.

Keywords

• pc1 pulsations
• geomagnetic storm
• diurnal variation
• wave frequency
• polarization ellipticity