Identifying atmospheric and ionospheric anomalies based on remote sensing satellites has contributed highly to develop the hypothesis of lithosphere-atmosphere-ionosphere coupling (LAIC) over the Earthquake (EQ) epicenter during the seismic preparation period. This paper has investigated the variations of potential EQ precursor in daytime and nighttime Land Surface Temperature (LST) before and after the 2019 Pakistan EQ from MODIS (Moderate Resolution Imaging Spectroradiometer) satellite. The nighttime LST values of MODIS exhibit temporal anomalies during nighttime period within a time window of 5 days before and after the main shock day. Furthermore, the LST values predicted by Artificial Neural Network (ANN) validate the significant enhancement in nighttime time series of MODIS. The nighttime LST anomalies obtained from the observation and ANN prediction are more than 20% and 7% of normal distribution beyond the confidence bounds, respectively, within 5 days after the main shock. Likewise, the ionospheric anomaly from daily Total Electron Content (TEC) values at Sukkur Global Positioning System (GPS) station confirms the EQ associated ionospheric perturbations on the day after the main shock. The Global Ionospheric Maps (GIMs) also show the TEC anomalies during 1000-1400 LT on September 25, 2019.
Abstract. Scintillations of transionospheric satellite signals during geomagnetic storms can severely threaten navigation accuracy and the integrity of space assets. We analyze vertical Total Electron Content (vTEC) variations from the Global Navigation Satellite System (GNSS) at different latitudes around the world during the geomagnetic storms of June 2015 and August 2018. The resulting ionospheric perturbations at the low-and mid-latitudes are investigated in terms of the prompt penetration electric field (PPEF), the equatorial electrojet (EEJ), and the magnetic H component from INTERMAGNET stations near the equator. East and South-East Asia, Russia, and Oceania exhibited positive vTEC disturbances, while South American stations showed negative vTEC disturbances during both storms. We also analyzed the vTEC from the Swarm satellites and found similar results to the GNSS retrieved vTEC during different phases of both geomagnetic storms. Moreover, we observed that ionospheric plasma tended to increase rapidly during the afternoon in the main phase of the storms. At nighttime, the ionosphere depicted an opposite behavior under similar conditions. The equatorial ionization anomaly (EIA) crest expansion to mid and high latitudes is driven by PPEF during daytime at the main and recovery phases of the storms. The magnetic H component exhibits a longitudinal behavior along with the EEJ enhancement near the magnetic equator.
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