Contaminated effect of Geomagnetic storm on pre-seismic atmospheric and ionospheric anomalies during Imphal earthquake

Understanding of Seismo-ionospheric coupling mechanism requires a quiet geomagneticcondition to eliminate any kind of contamination in the lower atmospheric and ionospheric parameters. We present the evidence of such event during a strong earthquake happened in Imphal on January 4, 2016 (M=6.7). We studied the lower ionospheric irregularities using Very Low Frequency radio wave characteristics as observed from fixed frequency transmitter JJI (22.2 kHz) in Japan by using the conventional nighttime fluctuation methods. We also studied the presence of Atmospheric Gravity Wave (AGW) in VLF data and also computed from SABER/TIMED satellite observation. Two geomagnetic storms occurred on December 21, 2015 and January 1, 2016. By the conventional analysis, we found there are significant decrease in nighttime trend and increase in nighttime fluctuations, but seismo-genic effects are quite contaminated due to the storm. The AGW variation shows similar effects but less prominent. By analysis of SABER data, we found enhancement of AGW, but effects are rather post-storm effect instead of pre-seismic. The same results obtained when the presence of wavelike structure are computed from the Fast Fourier Transform of the nighttime VLF data. So, this paper shows a significant example of elimination of contamination of pre-seismic phenomena from other terrestrial solar energetic sources.