NOPR Collection:

Influence of the Equatorial Counter-Electrojet on the Diurnal Variation of N_mF2

2016-11-09T09:53:33Z

Title: Influence of the Equatorial Counter-Electrojet on the Diurnal Variation of N_mF2 Authors: Rao, B A; Rao, D R K Abstract: The association between the occurrence of the counter electrojet phenomenon and the diurnal variation of the maximum electron density of the F2-layer (N_mF2) in the equatorial electrojet region is investigated by a simple technique. It is shown that there is a significant influence of the counter-electrojet on the magnitude of the afternoon peak in the equatorial N_mF2. Page(s): 247-248

Instabilities of Obliquely Propagating Electromagnetic Modes in the Magnetosphere

2016-11-09T09:51:39Z

Title: Instabilities of Obliquely Propagating Electromagnetic Modes in the Magnetosphere Authors: Renuka, G; Viswanathan, K S Abstract: The oblique propagation of the ordinary and the extraordinary electromagnetic modes in the magnetosphere and the instabilities in these modes arising from temperature anisotropy are studied. The dispersion equation is solved numerically using a TDC 316 computer for (i) McIIwain parameter L = 2 and 3; (ii) temperature anisotropy ratio δ (= T/T_II ) values varying from 10 to 0.1 and (iil) for wavelength of waves of the order of a kilometer. The computer calculations are carried out for frequencies in the range ω₁, to 3 ω₁, and ω₂ to 3 ω_2, where ω₁, and ω₂, are the left-hand and right-hand cut-off frequencies, and both the real as well as the imaginary parts of the wave vector are calculated. It is found that both the ordinary and the extraordinary electromagnetic waves are unstable and the instability shows a strong dependence on the propagation angle θ, McIlwain parameter L, propagation frequency and also on the temperature anisotropy ratio δ. Page(s): 242-246

Diffraction of 140 MHz ATS-6 Signal by Lenslike Ionospheric Irregularities

2016-11-09T09:45:13Z

Title: Diffraction of 140 MHz ATS-6 Signal by Lenslike Ionospheric Irregularities Authors: Dabas, R S; Tyagi, T R; Somayajulu, Y V; Lal, J B Abstract: Using the theoretical modelling of diffraction patterns produced by isolated ionospheric irregularities at E-region height, the scale sizes and maximum electron density enhancements are determined for the events observed at Delhi (lat., 28.6° N; long., 77.2°E) on 140 MHz radio beacon transmission from ATS-6 geostationary satellite. Some model calculations are done to see the effect of scale size and electron density on the characteristics of observed diffraction pattern. Simulation of some of the events observed on 140 MHz radio beacon transmission by isolated ionospheric irregularities at the E-region heights suggests that these are produced by the one dimensional Gaussian fluctuations in electron density. The scale sizes and maximum electron density enhancements of the isolated irregularities determined are found to vary from 30 to 300 m and 4.3 x 10¹¹ to 1.4 X 10¹² eI./m³, respectively. The results are compared with those of other workers. Page(s): 234-241

HF Doppler Observations during the Total Solar Eclipse of 16 February 1980

2016-11-09T09:42:30Z

Title: HF Doppler Observations during the Total Solar Eclipse of 16 February 1980 Authors: Murthy, C S V Ramana; Rao, A S Mohana; Rao, B R Abstract: HF Doppler observations were made at Waltair on 10 MHz ATA standard time and frequency CW signal from New Delhi during the total solar eclipse of 16 Feb. 1980 across South India. The Doppler record showed characteristic frequency variations particularly observable on an eclipse day, which throw some light on reflection height changes in the ionosphere during an eclipse. The record also exhibits a quasi-periodic structure of 6-min period which would not be present normally for this time of the day. This feature could be an eclipse generated phenomenon. Page(s): 230-233

NOPR Collection:

Influence of the Equatorial Counter-Electrojet on the Diurnal Variation of NmF2

Instabilities of Obliquely Propagating Electromagnetic Modes in the Magnetosphere

Diffraction of 140 MHz ATS-6 Signal by Lenslike Ionospheric Irregularities

HF Doppler Observations during the Total Solar Eclipse of 16 February 1980

Influence of the Equatorial Counter-Electrojet on the Diurnal Variation of N_mF2