NOPR Community:

Mesospheric Warming/Cooling over Tropics during Jan-Feb 1979

Thu, 01 Dec 1983 00:00:00 GMT

Title: Mesospheric Warming/Cooling over Tropics during Jan-Feb 1979 Authors: Mukherjee, B K; Indira, K; Murty, Bh V Ramana Abstract: Three large warming pulses were reported over the high latitude (80ᵒN) during the last 10 days of January and during February 1979, in the upper stratosphere (~4 mbar) and in the middle stratosphere (~10 mbar). No information about the thermal behaviour of the upper stratosphere and the mesosphere over the tropics was available during the above period. Analysis of the M-100 rocketsonde temperature data for Thumba (lat., 8 32'N; long . 76 52'E) for 8 days in January and for 7 days in February indicated that the mesospheric region over tropics was subjected to a temperature perturbation of more than 15 K. spread through a column of thickness of 13 km (56-69 km), within 6 days (27 Jan-2 Feb). The maximum warming was 29 K at 63 and 64 km. Page(s): 213-214

Solar Flares & Lower Ionospheric Parameters

Thu, 01 Dec 1983 00:00:00 GMT

Title: Solar Flares & Lower Ionospheric Parameters Authors: Yagnik, H K; Rai, R K Abstract: The results of analysis of a large number of solar flare events registered by SMS GOES satellite are presented. In 86% cases of the X-ray events one or more types of SIDs were present. H and radio bursts were present only in about 72% cases of X-ray enhancements. Electron density profiles during the flare events of II Oct. 1980 and 9 Nov 1979 have been proposed considering enhanced production, decreased effective recombination coefficient (eff) and the experimental absorption values. It has been found that the decrease in eff during a solar flare depends upon the severity of the flare. Page(s): 208-212

Study of VHF Satellite Scintillations at a Low Latitude Station

Thu, 01 Dec 1983 00:00:00 GMT

Title: Study of VHF Satellite Scintillations at a Low Latitude Station Authors: Bhardwaj, R K; Lal, J B; Dutra, H N; Dabas, R S Abstract: The amplitude scintillations at 136.1 MHz radio transmission from the geostationary satellite ETS-II at Kurukshetra (29.9 N, 70.8 E) have been recorded during the period Oct. 1978-Sep 1979. Scintillations have been observed to be predominantly a nighttime phenomenon although the scintillation activity is low. Scintillations are also observed during daytime with a secondary maximum of occurrence during midday. The scintillation index (SI) has been found to increase with increase in solar flux during daytime while nighttime scintillations are independent of solar flux. The SI values are in general higher on magnetically quiet days compared to disturbed days. Page(s): 202-207

Unusual Lower & Upper Cut-off Frequency of Whistlers Observed at Nainital

Thu, 01 Dec 1983 00:00:00 GMT

Title: Unusual Lower & Upper Cut-off Frequency of Whistlers Observed at Nainital Authors: Khosa, P N; Lalmani; Ahmad, M M; Singh, B D Abstract: An unusual type of fine structure in the whistler spectra recorded at the low latitude ground station Nainital (geomag. lat., 19°1'N) is reported. The recorded whistler energy is found to be confined to particular frequency band and is characterized by typical periodicity. An attempt has been made to explain by ray-tracing technique the confinement of the whistler energy to the observed frequency band together with its time evolution. Further, the observed smooth decrease in dispersion has been interpreted in terms of the corresponding decrease in the electron content of tubes of ionization. Page(s): 197-201