Study of Early/slow VLF perturbations observed at Agra, India
Thursday, 4 September 2014
Regency Ballroom (Hyatt Regency)
Uma Pandey1,2, Ashutosh K Singh3,4, O. P. Singh3, Birbal Singh2 and V K Saraswat1, (1)Bansthali University, Physics, Bansthali, India, (2)Raja Balwant Singh Engineering Tech. Campus, Bichpuri Agra, Electronics and Communication Engineering, Agra, India, (3)Raja Balwant Singh Engineering Tech. Campus, Bichpuri Agra, Physics, Agra, India, (4)Banaras Hindu University, Physics, Varanasi, India
Abstract:
Initial results of sub-ionospheric VLF perturbations observed on NWC (19.8 kHz) transmitter signal propagating in the Earth-ionosphere waveguide, monitored at our low latitude station Agra (Geomag. Lat 27°E, long.78°N). During the period of observation (June, 2011 to December, 2011), we found 74 cases of abrupt amplitude/phase perturbations showing early character. The onset duration of these early VLF perturbations is up to ~ 5 sec, showing early/slow character. Most of the observed early events show amplitude change lying between ±3.0 dB, and phase change ±12 degree respectively and found to occur mainly during nighttime. One of the interesting result we found that the events with larger recovery time lies far away from the VLF propagation path, while events with smaller duration of recovery are within the ±50-100 km of signal path. The World Wide Lightning Location Network (WWLLN) data is analysed to find the location of causative lightning and temporal variation. The lightning discharge and associated processes that leads to early VLF events are discussed.
