http://nopr.niscpr.res.in/handle/123456789/36527 2026-10-11T14:02:48Z http://nopr.niscpr.res.in/handle/123456789/36553 Title: Instabilities of Left Circularly Polarized Waves in a Plasma Containing Cold & Hot Species in the Earth's Magnetosphere Authors: Renuka, G Abstract: Expression for the growth/decay rate of left circularly polarized (LCP) waves propagating along the static magnetic field through a hot ion plasma with a loss cone structure containing a small proportion of a stream of either cold ions or electrons with a δ-distribution has been studied. It is shown that the presence of streaming particle can have pronounced effect on the wave propagation near the ion cyclotron frequency. It is also shown that the wave propagation depends on the plasma β-parameter and the Mcllwain parameter <i>L</i>, but no dependence on loss cone index <i>j</i> is observed. Page(s): 119-123 1986-06-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/36552 Title: Equatorial Counter Electrojet-Solution of Some Dilemma Authors: Alex, S; Patil, A; Rastogi, R G Abstract: The examination of horizontal geomagnetic fields at Huancayo and Fuquene with corresponding <i>f</i>Esq at Huancayo at intervals of each 5 min during storms, revealed that any disappearance of Esq corresponded to the negative ∆<i>H</i> (Huancayo) ∆<i>H</i> (Fuquene) with reference to the value at midnight. The occurrences of Esq and the upwards vertical F-region electron drift had excellent correlation with positive ∆<i>H</i> (equator) - ∆<i>H</i> (low latitude) and not with ∆<i>H</i> (equator) or ∆<i>H</i>_ST proposed by Rao et al. [Rao M M, Sethuraman R &amp; <i>Alamelu V. Indian J Radio &amp; Space Phys</i>, 13 (1984) 71.] Some of the dilemma pointed out by Kane [Kane R P, <i>Indian J Radio &amp; Space Phys.</i> 5 (1976) 6] have been either due to the choice of the hourly mean geomagnetic data or due to using some non-q type sporadic-E layer data for the analyses. There is no dilemma if instantaneous values of the <i>H</i> field at equatorial and low latitude stations and only the equatorial (q) type of sporadic-E layer data are used to study the effect of counter electrojet on the equatorial ionosphere. Page(s): 114-118 1986-06-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/36551 Title: Microwave Radiometer Measurements of Soil Moisture Content Authors: Vyas, A D; Trivedi, A J; Calla, O P N; Rana, S S Abstract: Ground-based microwave radiometer experiments have been performed to investigate the effect of moisture on microwave emission from bare field. Measurements were made at 19.1 GHz using tower mounted dual polarized (vertical and horizontal) microwave radiometer to observe prepared soil site in the Gujarat University Campus, Ahmedabad. Increasing the soil moisture content from 5 to 20% by weight resulted in brightness temperature decrease of 40 K, depending, to a lesser extent, on polarization and viewing angle. The observed brightness temperatures over a bare field are higher than those calculated from an emissivity model. Page(s): 110-113 1986-06-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/36550 Title: Variation in Ground Electric Field due to Various Forms of Intracloud Lightning Discharges Authors: Singh, Pratap; Verma, T S; Mathpal, K C; Varshneya, N C Abstract: The calculations for instantaneous and total changes in ground electric field due to various forms of intracloud lightning discharges are presented. To place in perspective the significance of the individual form of intra cloud discharge, three possible cases, namely, propagation of positive, negative and complex streamers have been studied separately. The important aspects of thunderclouds such as spatially inhomogeneous charge distribution, redistribution of charge due to propagation of streamers, and concept of finite dimensions of streamers and thunderclouds have been taken into account. The present study points out the incapability of the electric field variation dependent hypothesis to distinguish between a negative and a complex streamer because both these streamers produce negative changes in ground electric field. Our theoretical findings suggest that a more convincing hypothesis to classify the nature of intracloud discharges should incorporate magnitudes of electric field variations along with the nature of electric field changes. Plots of total electric field change against distance of observing point show a reasonable agreement with the observed magnitude variations and electric field sign reversal distances at ground. Page(s): 104-109 1986-06-01T00:00:00Z