http://nopr.niscpr.res.in/handle/123456789/35265 2026-10-12T21:15:16Z http://nopr.niscpr.res.in/handle/123456789/35317 Title: Long term variations of solar wind and geomagnetic disturbances Authors: Dubey, S C; Mishra, A P Abstract: The average behaviour of solar wind speed and planetary geomagnetic index <em>A</em>_p, during 22nd solar cycle, have been discussed. It is found that the annual mean global geomagnetic disturbances show a solar cycle dependence, while annual mean value of solar wind velocity does not show any significant correlation with minimum and maximum phase during 22nd solar cycle. Page(s): 244-246 1998-10-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/35316 Title: Estimation of error in the determination of temperature using MST radar Authors: Revathy, K; Nayar, S R Prabhakaran; Murthy, B V Krishna Abstract: The Indian MST radar at Gadanki is a very powerful system for the study of atmospheric dynamics providing good altitude and time resolution in the measurement of atmospheric wind. A method has been developed to evaluate the temperature profile of the troposphere-stratosphere region from the nature of the spectrum of vertical velocity oscillations. In this communication, the errors involved in the estimation of temperature are presented. Page(s): 241-243 1998-10-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/35315 Title: Effect of solar poloidal magnetic field reversal on diurnal anisotropy of cosmic ray intensity on quiet days Authors: Kumar, Santosh; Shrivastava, S K; Dubey, S K; Richharia, M k; Gulati, Umesh Abstract: Using the Deep River neutron monitor (NM) data for the period 1964-95 covering three solar cycles, namely 20, 21 and 22, the long term trend and the effect of reversal of polarity of the solar magnetic field (PSMF) on the diurnal anisotropy of cosmic ray (CR) intensity on quiet days (QDs) have been investigated. The phase of the diurnal anisotropy on the QD has started regaining its usual corotational direction after 1976, acquiring it in 1985 and remains statistically invariant till 1991. The phase of the diurnal anisotropy on QD has shown a significant shift to early hours when the PSMF in the northern hemisphere (NH) is positive during the periods 1971-79 and 1992-95 as compared to that during the periods 1964-70 and 1980-89 when the PSMF in the NH is negative, confirming again the earlier results of 22-yr periodicity. Page(s): 236-240 1998-10-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/35314 Title: Fluctuations in vertical plasma drift and magnetic activity Authors: George, T M; Joymon, D; Sebastian, Somi; Rajesh, P K; Nayar, R Prabhakaran; Revathy, K Abstract: The fluctuations in vertical plasma drift velocity at the magnetic equator are studied using the high resolution HF Doppler digital data recorded during 1994-95. The observations show a large variety of fluctuations in the vertical plasma drift during the post-sunset period. The spectrum of vertical velocity with periods less than 1 h is also investigated. It is observed that, in general, the mean frequency of the fluctuations shows an inverse relation with the magnetic activity index <em>A</em>_p. Page(s): 233-235 1998-10-01T00:00:00Z