Riometer absorption during four similar storms

Abstract

Absorption level by riometer was estimated at high-latitudes during four moderate magnetic storms that occurred in 2018 and were similar by several features. The data of riometer absorption at 30 MHz was obtained from Sodankylä Geophysical Observatory in Finland (67.36°N, 26.63°E). Particle precipitations were estimated by POES satellite data. According to our results, the character of development of the magnetic disturbance and the similarity/difference of Space Weather parameter variations (IMF magnitude, solar wind parameters, Dst variation) did not played the leading role in the absorption peak value. The absorption level in the auroral oval during the considered similar moderate magnetic disturbances depended on the combination of factors: simultaneous electron bursts of particular energies, the number of precipitating particles in these bursts and the moment of the storm at which such precipitation bursts occurred. The highest absorption was caused by the large electron precipitations with energies of >40 keV and >130 keV that occurred just after the maximal storm development at the very beginning of the recovery phase of the storm.