Abstract
Using the list of the omega structures based on the The Magnetometers -
Ionospheric Radars- Allsky Cameras Large Experiment (MIRACLE) network
(Partamies et al. 2017), we obtained a number of important statistical
characteristics describing the surface magnetic field. Based on 438
events, typical magnetic variation 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
western 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, appearance of the omega structures in the dark morning MLT
sector results in twice 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
|dB/dt|>10nT/s, reveal magnetic
signatures similar to omegas. Our findings, together with the results
described in Apatenkov et al., 2020, emphasize the important role of
omega structures in the formation of large geomagnetically induced
currents.