Statistics on omega band properties and related geomagnetic variations

Abstract

<div lang="en" class="abs"><p class="abs_header">Abstract</p><p>Using the list of the omega structures based on the Magnetometers-Ionospheric Radars-All-sky Cameras Large Experiment network (Partamies et al., 2017, <a href="https://doi.org/10.5194/angeo-35-1069-2017">https://doi.org/10.5194/angeo-35-1069-2017</a>), we obtained a number of important statistical characteristics describing the surface magnetic field. Based on 438 events, typical magnetic variations associated with the passage of the single omega were obtained. The typical variation, obtained using superposed epoch analysis, is associated with a local bending of the westward electrojet and statistically confirms the distribution of equivalent ionospheric currents obtained in earlier observations of single omegas. It was found that during low and moderate geomagnetic activity, the appearance of the omega structures in the dark morning magnetic local time (MLT) sector results in two times higher than average dB/dt on the ground surface. Also, the velocity, direction of movement, and area of omega structures were calculated. It is shown that faster and bigger omegas produce larger time derivatives of the ground magnetic field. Furthermore, we demonstrate that in the 03–08 MLT sector, superposed magnetic variations for the arbitrary events of very high time derivatives |<em>dB/dt</em>| > 10 nT/s, reveal magnetic signatures similar to omegas. Our findings, together with the results described by Apatenkov et al. (2020, <a href="https://doi.org/10.1029/2019gl086677">https://doi.org/10.1029/2019gl086677</a>), emphasize the important role of omega structures in the formation of large geomagnetically induced currents.</p></div>