抄録
During the total solar eclipse in India on July 22, 2009, we measured the amplitude of the fixed frequency VLF transmitter signals (f =19.8 kHz, NWC, Australia) at Agra (Geographic Lat. 27.2°N, Long. 78°NE), using a SoftPAL (Software based phase and amplitude logger) receiver. It was the longest total solar eclipse in the 21st century seen in India ever since 18 August, 1968. We analysed the VLF data for a period of fifteen days (±7 days from the date of the event) and found that the amplitude of the signal decreased on 22 July in the time sector of 2 hrs between 0530 and 0730 hours LT with the maximum depletion during the period of total solar eclipse. The result is interpreted in terms of depletion of electron density in the D region of the ionosphere caused by the solar eclipse.
