Geodetic Remote Sensing of Ionosphere in Relation to Space Weather and Seismic Activity in B&H

Abstract

Total electron content (TEC), along GNSS signal’s path in the ionosphere, is spatially and temporally highly variable. In addition, sudden disturbances in the ionosphere may occur on the global, regional or local level from external sources, such as space weather and seismic activity. Results of TEC investigation for mid-latitude ionosphere over B&H (Bosnia and Herzegovina) during seismic activity of medium intensity (4 < M < 5 Richter) and severe geomagnetic storm (St. Patrick’s Day in 2015) are presented. Analyses of relevant parameters such as solar wind, interplanetary magnetic field and geomagnetic activity are performed. Different analyses of TEC variations are carried out. Lower and upper bounds (LB and UB) are determined by 15-day running TEC median prior the day of consideration ± 2*standard deviation. TEC values which exceeded LB and UB are marked as anomalies. TEC_QUIET is calculated as mean TEC for five quietest days in a month regarding geomagnetic conditions to observe TEC residuals due to enhanced geomagnetic activity. Direct comparison of TEC values at different stations is also conducted. TEC deviations were in better agreement concerning GNSS stations located close to the epicentre. Both positive and negative anomalies were registered 2 weeks before the earthquake, with higher deviations during 7 days before, at stations located inside the earthquake preparation zone. The potential causes of these anomalies are discussed. Analysis of TEC response to the strongest geomagnetic storm in solar cycle 24 shows TEC deviations from 50% to even 150% compared to TEC_QUIET, where “positive ionospheric storm” is observed in the main phase and “negative ionospheric storm” in the recovery phase of the geomagnetic storm.