Response of the sub-ionospheric VLF/LF signals to the major SSW event of 2009

Abstract

In this paper, sub-ionospheric Very Low Frequency/Low Frequency (VLF/LF) radio signals over the North Atlantic zone and North Pacific zone have been analysed during the major Sudden Stratospheric Warming (SSW) event of January, 2009. Signals from the transmitters like, NAA (24.0 kHz) and NKR (37.5 kHz) received at Germany and signals from the transmitters like, NLK (24.8 kHz) and NPM (21.4 kHz) received at Japan are considered for possible lower ionospheric response to the SSW event. Very clear and significant increase/decrease of average nighttime and daytime VLF/LF amplitudes from the quiet signals have been found associated with the SSW event.