R P Patel
Articles written in Pramana – Journal of Physics
Volume 55 Issue 5-6 November 2000 pp 685-691 Space And Astrophysical Plasmas, Contributed Papers
Matched filtering-parameter estimation method and analysis of whistlers recorded at Varanasi
R P Singh R P Patel Ashok K Singh D Hamar J Lichtenberger
The matched filtering technique is based on the digital-construction of theoretical whistlers and their comparison with observed whistlers. The parameters estimated from the theoretical and experimental whistler curves are matched to have higher accuracy using digital filters. This yields a resolution ten times better in the time domain. We have tested the applicability of this technique for the analysis of whistlers recorded at Varanasi. It is found that the whistlers have propagated along
Volume 55 Issue 5-6 November 2000 pp 699-705 Space And Astrophysical Plasmas, Contributed Papers
Ionospheric plasma by VHF waves
R P Patel Abhay Kumar Singh R P Singh
The amplitude scintillations of very high frequency electromagnetic wave transmitted from geo-stationary satellite at 244.168 MHz have been recorded at Varanasi (geom. lat. 14′ 55′N) during 1991 to 1999. The data are analyzed to determine the statistical features of overhead ionospheric plasma irregularities which are mostly of small duration <30 minutes and are predominant during pre-midnight period. The increase of solar activity generally increases the depth of scintillation. The auto-correlation functions and power spectra of scintillations predict that the scale length of these irregularities varies from 200–500 m having velocity of movement between 75 m/sec to 200 m/sec. These results agree well with the results obtained by other workers.
Volume 56 Issue 5 May 2001 pp 605-613 Research Articles
VLF emissions from ionospheric/magnetospheric plasma
VLF emissions such as hiss, chorus, oscillating tones, hiss-triggered chorus and whistler triggered emissions have been observed at low latitude Indian stations. In this paper we present dynamic spectra of these emissions and discuss their various observed features. It is argued that most of the emissions are generated during Doppler shifted cyclotron resonance interaction between the whistler mode wave and counter streaming energetic electrons. Resonance energy of the participating electron and interaction length are evaluated to explain the generation mechanism of some of these emissions observed at Indian stations.
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