NOPR Collection:

Precipitation of low energy electrons near the lower edge of inner radiation belt

Sun, 01 Jun 1997 00:00:00 GMT

Title: Precipitation of low energy electrons near the lower edge of inner radiation belt Authors: Prakash, Ram; Singh, R P; Awasthi, R C; Singh, D P Abstract: Considering Landau resonance interaction between energetic electrons and plasmaspheric hiss of natural origin, precipitation of low energy (eV and keV) electrons near the lower edge of the inner radiation belt is studied. The results show that the off-equatorial Landau resonance acts on resonant electrons of energy as low as ~45 eV, whereas the first order cyclotron resonance acts on electrons of higher energy (>10⁴ keV). The maximum flux of precipitating electrons in this region by Landau resonance is found to be ~10^-3 times the trapped flux, which is consistent with the observed spectrum of precipitated energetic electrons in the South Atlantic Magnetic Anomaly (SAMA) region. Thus, the off-equatorial Landau resonance satisfactorily explain the loss of low energy electrons near the lower edge of inner radiation belt, the upper limit of energy of resonant electrons precipitated by this mechanism being ~210 keV. Page(s): 170-174

Effect of magnetic activity on the E- and F-region drifts over Patiala

Sun, 01 Jun 1997 00:00:00 GMT

Title: Effect of magnetic activity on the E- and F-region drifts over Patiala Authors: Singh, Darshan; Gurm, H S Abstract: On comparison of day to day variations of geomagnetic K_p index with variations of midday E-region and midnight F-region drift speed measured over Patiala for the periods 1987-88 and 1989-90, it is seen that the annual mean variations of both the E- and F-region drift speed are independent on K_p index. However, there is a significant seasonal change in the behaviour of the E-region drift speed with variations in K_pindex and it is attributed to seasonal change in the position of S_q focus. The effect of magnetic activity on E-W component of the drift speed is more as compared to its effect on N-S component in both the E- and F-regions Page(s): 163-169

Some studies on elliptical microstrip stacked antenna for circular polarization

Sun, 01 Jun 1997 00:00:00 GMT

Title: Some studies on elliptical microstrip stacked antenna for circular polarization Authors: Vishvakarma, Babau R; Shyamla, G; Vasistha, P Abstract: Experimental investigations conducted to examine the various radiation characteristics of the elliptical microstrip stacked antenna reveal that there is a significant improvement in radiated power level, gain, beamwidth and bandwidth of the antenna when stacked with number of symmetrical parasitic elements. Stacking of antenna with four parasitic elements is found to raise the radiated power level by 4.5 dB, improve the gain by 5 dB, reduce the beamwidth from 80° to 21° and enhance the bandwidth from 0.8% to 4.0% for VSWR 1.5:1 and from 1.3% to 7.0% for VSWR 2:1 as compared to single active element. Page(s): 159-162

Radio wave propagation studies for mobile communications VHF in the south Indian coastal zones

Sun, 01 Jun 1997 00:00:00 GMT

Title: Radio wave propagation studies for mobile communications VHF in the south Indian coastal zones Authors: Prasad, M V S N; Sarma, S B S S; Ahmad, Iqbal Abstract: Field strength measurements at 150 MHz were conducted as a function of distance for various base station antenna heights in the south Indian coastal zones and the observed results are compared with different prediction techniques to identify suitable prediction method for estimating path loss. These are carried out in urban, sub-urban, quasi-open and open regions for various base station antenna heights. These studies will be useful for designing mobile communication systems in these regions. Page(s): 154-158