Seasonal and helio-geomagnetic activity pattern of the ionospheric variability over Russia's Eastern Siberia and Far East region from the GPS/GLONASS data

Abstract

We studied the ionospheric variability based on the analysis of vertical total electron content (TEC) variations over the Eastern Siberia and Far East regions during the period of 2002–2015. TEC data were measured from the phase of dual-frequency GPS/GLONASS receivers located in middle (Irkutsk), sub-auroral (Yakutsk) and high-latitude (Norilsk and Tiksi) regions. As a characteristic of the ionospheric variability high-frequency component, we used the TEC variation coefficient, which is a normalized TEC dispersion in daytime. This coefficient represents the level of internal gravity waves (IGW) activity in the ionosphere. Analysis of seasonal variability changes and those related to solar and geomagnetic activity revealed significant deviations of the TEC variation coefficient throughout a year. The lowest coefficient values of about 5–10% are recorded at all the stations in summer months. Maximum TEC variability was detected in winter, exceeding the summer time variations up to 6 times. These variations are regularly observed from year to year, they are not associated with changes in helio-geomagnetic conditions. The ionospheric variations analyzed are presumably caused by IGW propagating into the thermosphere from the lower atmosphere. The IGW generation sources at strato-mesospheric heights may be associated with shear-layer instabilities in the spatially non-uniform, high-velocity jet stream associated with the winter circumpolar vortex (CPV). Based on ECMWF ERA-Interim reanalysis data, we revealed a significant increase in wave activity at the strato-mesosphere heights from November to February for all the years considered. Wave disturbances generated inside winter CPV area can be partly transmitted upward. Propagating upward, IGWs transfer atmospheric constituents into the mesosphere and lower thermosphere. It leads to the molecular gas inflow or outflow at these heights, thereby altering the [O]/N 2 ] ratio and causing ionospheric variation.