Equatorial Plasma Bubbles: Occurrence Probability versus Local Time

Abstract

The character of the variability of the LT distributions of the equatorial plasma bubble occurrence probability with an increase of the recording altitude is under consideration. The conditions of the high and maximal solar activity, when the generation of the plasma bubbles is the most active, are examined. For this purpose the detailed comparative analysis of the LT distributions of the equatorial plasma bubble occurrence probability derived from the ISS-b (~972–1220 km), Hinotori (~650 km), ROCSAT-1 (~600 km), AE-E (~300–475 km), and CHAMP (~380–450 km) satellite data was done. The pronounced trend of the local time shift of the bubble occurrence probability maximum with an increase of the altitude is revealed. Thus, if the maximum occurs after sunset (~2030–2200 LT) at the bottom-side of the F-layer, it shifts toward the premidnight (~2100–2400 LT, ~600 km), then to the postmidnight (~0100–0300 LT, ~650 km), and, finally, to the predawn hours (~0300–0400 LT, ~972–1220 km) as the observation altitude increases. The most typical velocities of the equatorial plasma bubble rise are found to be ~150–300 m/s, which correspond to the numerous observational data.