Response of the Sub-Ionospheric VLF Signals to the Super Cyclonic Storm Amphan: First Observation from Indian Subcontinent

Abstract

The lower ionospheric disturbances associated with the Super Cyclonic Storm Amphan over the Bay of Bengal have been presented in this paper. The disturbances were observed by sub-ionospheric Very Low Frequency (VLF) radio signals from two navigational transmitters VTX and NWC, received at Cooch Behar, India. Strong variations of the nighttime signal amplitudes exceeding three times their standard deviations have been observed during the peak intensity phase of the cyclone. Morning terminator time in the VLF signal was influenced just after the cyclone peak and evening terminator time was influenced significantly after landfall. The radius of the strongly perturbed ionospheric region associated with the cyclone during its peak intensity has been estimated approximately between 500 and 1000 km from VLF observations.