Radio signatures of November 1998 leonid meteor on transionospheric VHF satellite signal

This letter presents, to our knowledge for the first time, two cases of sci ntillations of the 244 MHz satellite beacon signal recorded from the geosta tionary satellite FLEETSATCOM (FSC) (Long: 73 degrees E) at the Haringhata Field Station (HFS) (Lat: 22.97 degrees N Long: 88.50 degrees E Dip: 32 deg rees N) of the University of Calcutta on the night of November 16/17, 1998, which corresponds to the peak period of the Leonid meteor shower in terms of its rate and visual magnitude. Scintillations produced by the sporadic-E layer (E-s) generated by meteoric ionization are transient and quasi-perio dic in nature. This type of scintillations have much shorter durations (sim ilar to 30-100s) than those normally observed at night in the equatorial la titudes (similar to5 min to couple of hours). It is characterized by a prim ary deep fade out in field strength, associated with regular ringing patter ns before and after it. Generation of quasi-periodic scintillations is beli eved to be due to a small-scale (scale size similar to 100-1000 m) density enhancement or blob which acts as a radio lens in the path of the transiono spheric signal. Assuming one-dimensional density irregularities, the peak p hase deviation introduced in the radio wave passing through is estimated. T he observed scintillation patterns have been simulated considering a series of isolated ionospheric irregularities of different strengths and scale si zes. Critical frequency of the E-s layer (f(0)E(s)) measured by the Ahmedab ad ionosonde (Lat: 23.03 degreesN Long: 72.40 degreesE Dip: 34 degrees N) f or the same night shows two isolated spikes which may be due to a sudden in crease in plasma density caused by meteoric ionization. In addition, the me teor visual magnitude and cumulative mean flux have been calculated using t he meteor intensity data available on the Internet. (C) 2001 Elsevier Scien ce Ltd. All rights reserved.