NOPR Collection:

5577 Å Night Airglow Emission from Barth’s and Chapman’s Mechanisms

1989-02-01T00:00:00Z

Title: 5577 Å Night Airglow Emission from Barth’s and Chapman’s Mechanisms Authors: Ghosh, S N; Midya, S K Abstract: Following Barth’s mechanism a theoretical curve of 5577 Å line emission at night with height is presented. An empirical relation between emission and height is then obtained from it. Experimental curve obtained by Kulkarni P V [J Geophys Res (USA), 81 (1976) 3740] gives intensity which agrees with that obtained from the curve of Barth’s mechanism. The intensity of 5577 Å line comes out to be 156 Rayleigh from the Chapman’s curve vis-à-vis 210 Rayleigh from the Barth’s mechanism, the latter value agrees with the accepted value 200 Rayleigh. Page(s): 33-35

Ionospheric drift results obtained using dipole & frame aerials

1989-02-01T00:00:00Z

Title: Ionospheric drift results obtained using dipole & frame aerials Authors: Vyas, B M; Rai, R K Abstract: Ionospheric drift observations have been carried out using separate arrays of dipole and frame aerials. The spaced fading records obtained so far have been subjected to similar fade, full correlation and dispersion methods of analysis. It is observed that on an average the results from dipole aerials give higher values of true drift speed, random drift speed and size of irregularities. Apparent drift speed, apparent drift direction and true drift direction do not show any variation in their values due to the type of antenna used. Page(s): 30-32

Electromagnetic Ion-cyclotron Mechanism in Jovian Magnetosphere

1989-02-01T00:00:00Z

Title: Electromagnetic Ion-cyclotron Mechanism in Jovian Magnetosphere Authors: Ahmad, M M; Lalmani; Khosa, P N Abstract: An attempt has been made to explain the various radio emissions of large frequency range observed in the Jupiter’s magnetosphere by the resonant interaction mechanism between the ion-cyclotron wave propagating along Jovian magnetic field lines and trapped fully ionize hydrogen plasma. The growth rate has been derived by the conservation of energy method for bi-Maxwellian distribution function in an anisotropic plasma. The variation of growth rate with propagation constant has been discussed, and the maximum growth rates for Jovian magnetospheric condition L_J=6 have been estimated for various values of the ratio of kinetic pressure to magnetic pressure and ion anisotropies. Page(s): 27-29

IEC and slab thickness near the peak of equatorial anomaly during sunspot maximum and minimum

1989-02-01T00:00:00Z

Title: IEC and slab thickness near the peak of equatorial anomaly during sunspot maximum and minimum Authors: Modi, R P; Iyer, K N Abstract: Ionospheric electron content (IEC) measurements for the last solar maximum (1980) using Faraday rotation technique at Rajkot (lat., 22.3°N; long., 70.7°E; subionospheric dip lat., 16.5°N) are reported. The diurnal variation shows tendency for post-sunset enhancements in IEC during equinox and winter. The winter daytime IEC values are 29% higher than the summer values indicating seasonal anomaly. Results are compared with earlier measurements during low sunspot year (1975). Contours of IEC and equivalent slab thickness () are presented. Electrojet control of the daytime peak IEC and lack of dependence of IEC on magnetic activity at least for moderate magnetic disturbances are pointed out. The results are discussed in terms of the effect of EXB drift on diurnal variation, particularly for high sunspot year. The role of composition changes in seasonal changes of IEC and and conjugate point plasma transfer and H⁺ O⁺ transition levels in producing pre-sunrise peaks of are presented. Page(s): 23-26