NOPR Community:

A study on the accuracy of time comparison via geostationary satellite in a common view mode

1995-12-01T00:00:00Z

Title: A study on the accuracy of time comparison via geostationary satellite in a common view mode Authors: Banerjee, P; Saxena, Mithlesh; Mathur, B S Abstract: A detailed analysis relating to the errors in the prediction of satellite coordinates to time comparison accuracy using geostationary satellite in a common view or differential mode is presented. The findings are directly applicable in the use of satellite-TV signal in a passive mode. With the present capability of prediction of satellite coordinates, an accuracy better than 2 s over India is expected. A comparison of the corresponding error in the case of time signal dissemination via satellite is one way mode has been made. Some experimental observations related to this has also been studied thoroughly to corroborate the analytical findings. Page(s): 333-339

Theoretical ratios for EUV emission lines of Na VI ion

1995-12-01T00:00:00Z

Title: Theoretical ratios for EUV emission lines of Na VI ion Authors: Gupta, A K; Dwivedi, B N Abstract: Theoretical line ratios for Na VI ion have been investigated using an atomic model including the first fifteen energy levels and taking account of various physical processes. The line emissivities as a function of electron density have been computed. Density-dependent theoretical line emissivity ratios are presented and their diagnostic applications in the solar atmosphere are discussed with the help of theoretical line intensities computed using an atmospheric model for the quiet sun. This study also indicated EUV emission lines of Na VI ion, hitherto not observed, for future observations. Page(s): 328-332

Precipitation efficiency of coherent whistler mode waves during non-linear cyclotron resonance

1995-12-01T00:00:00Z

Title: Precipitation efficiency of coherent whistler mode waves during non-linear cyclotron resonance Authors: Singh, D P Abstract: Non-linear cyclotron resonance between coherent whistler mode waves and energetic electrons is studies. It is found that there is a range of electron velocities, below and above which no interaction is possible. The maximum velocity of hot electrons (V_max) decreases with increasing wave frequency, suggesting that lower frequencies are more able to drag energetic radiation belt electrons into the loss cone to the dumped into the lower ionosphere. The V- space ( being the resonant pitch angle) decreases as frequency and L value increase, but then the resonant pitch angle range increases. The precipitation efficiency is found to increase with L and wave frequency. The results are consistent with the findings of earlier workers and experimental observations recorded aboard Injun-3 and ÄTS-1 satellites. Page(s): 323-327

Role of electron density gradients on wind-induced currents in the equatorial electrojet

1995-12-01T00:00:00Z

Title: Role of electron density gradients on wind-induced currents in the equatorial electrojet Authors: Selvamurugan, R; Devasia, C V Abstract: The role of electron density gradient changes in producing significant effects on the wind generated currents in the equatorial electrojet region at different times of the day is presented. Using the electron density profiles obtained by rocket-borne Langmuir probes at different times of the day and typical model wind profiles pertaining to equatorial electrojet region, it is shown that the sharp vertical electron density gradients in combination with wind profiles characterized by large wind shears can give rise to large magnitudes of wind generated currents at least on some occasions. Page(s): 314-322