Observation of Very Short Period Atmospheric Gravity Waves in the Lower Ionosphere Using Very Low Frequency Waves

We present observations of very short period (<5 min) wavy fluctuations (WFs) in the lower ionosphere (75-85 km) on the night of 21 January 2016, using subionospherically propagating very low frequency signals. Four out of six transmitter signals recorded by the very low frequency/low frequency receiver at the Pisgah Astronomical Research Institute showed WFs simultaneously. However, their time of occurrence and intensities were different. Power spectral analysis indicates a period of 3-4 mins, largely associated with the two regions of strong convective and lightning activity in the lower troposphere. Background wind (at 15 and 80 km) direction shows westward propagation, suggesting important role of the convective storm located east of Pisgah Astronomical Research Institute. The GPS total electron content analysis also divulges similar WFs at upper ionospheric altitude ( 300 km) on the GPS total electron content stations around the two storms. The observational analysis suggests atmospheric gravity waves from the convective regions propagate upward up into the ionospheric altitudes. Hence, the present study reinforces the strong coupling of troposphere and ionosphere through the convectively generated very short period waves.