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Monitoring of GPS signals at NPL, New Delhi, for precise time comparison

1994-12-01T00:00:00Z

Title: Monitoring of GPS signals at NPL, New Delhi, for precise time comparison Authors: Banerjee, P; Goel, G K; Mathur, B S Abstract: The Global Positioning Satellite System (GPS) signals are being extensively used for worldwide time comparison. The National Physical Laboratory (NPL), New Delhi, has also been utilizing GPS signals for comparison of time for a long time and has been contributing to the Coordinated Universal Time (UTC) maintained at BIPM, Paris. This paper explains the experimental setup of the network of international time link via GPS. The detailed analysis of data has been presented. It highlights a quantitative estimate of the deterioration of time accuracy as a result of introduction of selective availability in the GPS system. Page(s): 416-420

Effect of streaming electrons on streaming dust particle instability

1994-12-01T00:00:00Z

Title: Effect of streaming electrons on streaming dust particle instability Authors: Kulkarni, V H; Jayaraman, V; Dhar, V K Abstract: The dispersion relation for acoustic waves in a homogeneous, unmagnetized and uniform plasma consisting of charged streaming dust particles and streaming electrons is solved. The results are used to interpret the interaction between the solar wind plasma and cometary dust particle. Due to this, it is suggested that, small dust particles are likely to be swept by the solar wind and thus assist in the formation of cometary tail. Page(s): 410-415

Wide-band whistler-mode limiting magnetic field intensity and measurement of strength of pitch angle diffusion of resonant electron

1994-12-01T00:00:00Z

Title: Wide-band whistler-mode limiting magnetic field intensity and measurement of strength of pitch angle diffusion of resonant electron Authors: Prakash, Ram; Singh, R P Abstract: Following linear theory and adopting the well known Fokker Planck expression for diffusion coefficient, expressions for the limiting magnetic field intensity of wide-band whistler-mode waves and the diffusion parameter have been derived. The diffusion parameter is shown to be equal to the ratio of the experimentally observed intensity to the limiting intensity. In order to measure diffusion strength, the theoretically calculated limited magnetic field intensities are then compared with the magnetic field intensities observed experimentally both inside and outside the plasmasphere. The results show that strong diffusion is impossible at L 4, implying that the whistler-mode magnetic field intensity can never exceed its limiting value at such L values. The results at 4.5 L 8 both inside and outside the plasmasphere favour strong diffusion without ruling out, however, the occasional possibility of weak diffusion. The region of transition from weak to strong diffusion is found to lie at L = 4.5 ± 0.25. The results also indicate that the diffusion strength increases with increasing L values. Page(s): 403-409

Effect of solar eclipse on VLF propagation

1994-12-01T00:00:00Z

Title: Effect of solar eclipse on VLF propagation Authors: Pant, P; Mahra, H S Abstract: The Phase variations of VLF signals, namely, (i) OMEGA 13.6 kHZ, transmitted from La Reunion and (ii) GBR 16.0 kHz, transmitted from Rugby (UK) were observed during the solar eclipses on 16 Feb. 1980 and 31 July 1981, respectively. The solar obscurations averaged over the entire path length were calculated for both the events and these are compared with the observed phase deviations. The increase in the height of the D-region averaged over the entire path length is estimated to be 2.8 km for Naini Tal-La Reunion path for the eclipse of 16 Feb. 1980 and 2.9 km for Naini Tal-Rugby path for the eclipse of 31 July 1981. Page(s): 399-402