Remote sensing of atmospheric gravity waves (GWs) and planetary wave type oscillations (PWTOs) in the upper mesosphere-lower ionosphere system using the very low frequency transmitter data

We present the use of VLF radio data to study the short-period (~min to hrs) GWs and long-period (~days) PWTOs. To show the presence of GWs, we analyse the VLF data from several places obtained by ICSP-VLF network during the solar eclipse of July, 2009. We find dominant wave periods ranging from 10 minutes to 1 hour around the time of maximum eclipse phase which could be associated with atmospheric gravity waves excited due to the solar eclipse. We also analyse nearly 4 years of VLF amplitude data received at ICSP, Kolkata from the VTX (18.2 kHz) transmitter and also from the NWC (19.8 kHz) transmitter for planetary wave type oscillations (PWTOs) in the mesosphere-lower ionosphere system. Fourier and wavelet analysis show the presence of PWTOs in both the radio paths having periodicity in the range 5-27 days. The PW spectrum of VLF data are also correlated with the PW spectrum of Ozone data.