http://nopr.niscpr.res.in/handle/123456789/36921 2026-10-12T11:07:18Z http://nopr.niscpr.res.in/handle/123456789/36985 Title: Electromagnetic Field Strength Measurements during the Solar Eclipse of 16 Feb. 1980 Authors: Sethuraman, R; Jayaraman, R; Alamelu, V; Ravichandran, C Abstract: Observations of signal strengths at frequencies 588 and 1188 kHz from the ionosphere that lies in the path of totality of the total solar eclipse of 16 Feb. 1980 are presented. A sudden increase in signal strengths at medium frequencies during totality is observed while the shortwave signal strength is found to increase sharply with the start of the eclipse and reach the maximum at the time of totality and decrease gradually and approach normal conditions after the eclipse. Page(s): 198-200 1980-10-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/36984 Title: Diurnal Variation Of <i>h_max</i>E Estimated from Absorption Measurements Authors: Parameswaran, K; Murthy, B V Krishna Abstract: The diurnal variation of <i>h_max</i>E has been estimated by matching the observed diurnal variation of absorption on 2.2 MHz with the theoretical estimates and is compared with that expected for a Chapman layer. Page(s): 196-198 1980-10-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/36983 Title: Upper Atmospheric Turbulence Decay over Thumba Authors: Vernekar, K G; Mohan, Brij Abstract: A study of atmospheric turbulence from 20 to 80 km is made using the temperature data obtained from weekly M-100 rocket data over Thumba. The Richardson number is applied to estimate the amplitude of the turbulence. Turbulence was not detected at upper levels and a very stable atmosphere was found to be associated with a very high Richardson number. Page(s): 191-195 1980-10-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/36982 Title: Study of Medium-scale Travelling Ionospheric Disturbances Using Multistation ATS-6 Faraday Rotation Data Authors: Deshpande, M R; Rastogi, R G; Sengupta, A; Nagpal, O P; Setty, C S G K; Jain, A R; Rai, R K; Janve, A V; Patwari, V M; Subbarao, B S Abstract: Faraday rotation of 140 MHz signals from statelIite ATS-6 recorded at four neighbouring stations, namely, Bombay, Rajkot, Ahmedabad and Udaipur, have been used in the present study to find the periods, speeds and azimuth of medium-scale TIDs in the F-region. The study is confined to winter months of 1975-76. AIl the cases considered are daytime events since the winter nighttime TID occurrence is very rare. The speeds are found to vary from 54 to 314 m/sec covering azimuthal directions between 114 and 173° East of North. The general features of the speeds and azimuthal directions of the TIDs seem to indicate their origin in the tropospheric jet streams. Ray-tracing calculations carried out from the observation point (in the ionosphere) to the troposphere support this point strongly. It is believed that dynamic instability associated with vertical wind shear layers within the jet stream may be the chief cause for the generation of gravity waves which produce the observed TIDs. Page(s): 186-190 1980-10-01T00:00:00Z