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Relative Contribution of Various Secondary X-ray Components below 100keV at Balloon Altitudes

Wed, 01 Dec 1982 00:00:00 GMT

Title: Relative Contribution of Various Secondary X-ray Components below 100keV at Balloon Altitudes Authors: Manchanda, R K Abstract: A large fraction of total X-ray flux below 100keV at balloon altitudes consists of secondary components. Experimentally derived data for these different components for designing new detector systems for X-ray studies are presented. It is shown that, in case of a crystal scintillator, intrinsic production overtakes the other contribution if the aperture is made too narrow. Page(s): 255-256

Dependence of Ionospheric Drift Speed on Geomagnetic Activity

Wed, 01 Dec 1982 00:00:00 GMT

Title: Dependence of Ionospheric Drift Speed on Geomagnetic Activity Authors: Sardesai, D V; Badala, P; Rai, R K Abstract: Effect of geomagnetic activity on ionospheric drift speed is studied for Udaipur (geomag.lat., 14.55°N).To reduce the effect of solar activity, the study is made with the data obtained during Mar. 1974-Oct. 1975, a low activity period, and only those days for which 10.7 cm solar flux was below 90 have been considered. A negative correlation is found between noontime E-region apparent drift speed and geomagnetic K_p index. An identical relationship is obtained for nighttime apparent drift speed with K_p in case of F-region. The correlation coefficients deduced in the two cases are -0.81 and -0.86, respectively. Page(s): 252-254

Radiation from an Alford Loop Antenna in Two component Warm Plasma

Wed, 01 Dec 1982 00:00:00 GMT

Title: Radiation from an Alford Loop Antenna in Two component Warm Plasma Authors: Kumar, Anil; Gupta, R K Abstract: Expressions for the electromagnetic and the electroacoustic field components of a loop antenna radiating in a two component warm plasma are obtained. Assuming a plausible current distribution, variation of the radiation resistancy of an Alford loop antenna in two-component warm plasma with plasma frequency is compared with the experimentally measured values of the radiation resistance of a loop antenna on the Ariel-3 satellite. It is observed that the theoretically computed values of the radiation resistance are now closer than the values calculated by using earlier theory. Page(s): 247-251

Equatorial Radio Scintillations of ATS-6 Radio Beacons: Phase II-Ootacamund 1975-76

Wed, 01 Dec 1982 00:00:00 GMT

Title: Equatorial Radio Scintillations of ATS-6 Radio Beacons: Phase II-Ootacamund 1975-76 Authors: Rastogi, R G; Chandra, H; Deshpande, M R Abstract: Temporal variations of the amplitude fluctuations of the radio beacon signals on 40, 140 and 360 M Hz transmitted from the ATS-6 satellite (at 34°E longitude) received at Ootacamund (11.4 N, 76.7 E, magnetic dip 6° N) during the second phase ofthe ATS-6 programme (1975-76) are described. For 360 MHz beacon, the mean scintillations index had two minima of about1% (about 0.1 dB) during the sunrise and sunset periods; a flat maximum of about 4% (0.4 dB) around midday and another maximum of about 13% (1.2 dB) around 2100-2200 hrs LT. The mean scintillation index on 140 MHz was minimum (0.6 dB) around sunrise and sunset hours and maxima of about 2 dB were at midday and nighttime. The magnitude of scintillations of 40 MHz was about 3 dB around sunrise and sunset periods and about 5 dB during midday and midnight hours. The nighttime scintillations were strongest in October 1975 (thus during equinoxes) while daytime scintillations did not indicate any definite seasonal variation. Page(s): 240-246