NOPR Collection:

Seasonal & Sunspot-cycle Effects in the Occurrence of Equatorial Spread-F Configurations

2016-11-16T09:13:00Z

Title: Seasonal & Sunspot-cycle Effects in the Occurrence of Equatorial Spread-F Configurations Authors: Sastri, J Hanumath; Sastdharan, K; Subrahmanya, V; Rao, M M Srirama Abstract: A study has been made of the seasonal and solar cycle changes in the occurrence of the range- and frequency-type of spread-F at Kodaikanal (geomag, lat" 0'6o N; dip, 3'5 o N) using ionogram data for the period 1957-69. It is found that the range type of spread-F IS the predominant configuration on ionograms at Kodaikanal at any time o year. The occurrence of the frequency type of spread-F-shows a significant positive correlation with sunspot number irrespective of season while that of range-type spread-F shows such behaviour only during local summer months, A comparison of the behaviour of spread-F configurations at Kodaikanal with those at Huancayo reported recently indicates striking longitudinal dependence of the seasonal and solar cycle effects in the occurrence of the two basic forms of spread-F on equatorial ionograms. Page(s): 135-138

Integrated Production & Loss Rates in the Ionosphere

2016-11-16T09:09:57Z

Title: Integrated Production & Loss Rates in the Ionosphere Authors: Singh, Malkiat; Salaria, B S; Gurm, H S Abstract: Total electron content measurements from radio beacon signals of ATS-6 are used to calculate the integrated production rate and effective loss rates at Patiala, Ahmedabad and Bombay. The integrated production rate of electrons for overhead sun (Q₀) shows a seasonal variation with maxima near equinoxes rate (Q₀) and a minimum in June-July. Mean production rate (Q₀) is (1.2±0.02) x 10¹⁴ el, m^-2 sec^-1 for different months and stations. The mean effective loss rate, just after sunset. is determined to be (1·0 ± 0 3) x 10^-4 sec^-1 and it does not show any marked seasonal dependence. Page(s): 134-135

Fluorescence of Nitrogen Molecules due to Electron Impact

2016-11-16T09:07:16Z

Title: Fluorescence of Nitrogen Molecules due to Electron Impact Authors: Khare, S P; Kumar, Ashok Abstract: Fluorescence efficiencies of electrons for the second positive, first positive and the Vegard-Kaplan band systems of molecular nitrogen have been investigated by employing the Fowler equation and the continuous slowing-down approximation (CSDA). In the calculations the effects of Auger electrons and the cascading effects from higher excited states are considered It has been noticed from the study that in the low-energy region (E < 50 eV) the Fowler equation values are widely different from the CSDA values and show a number of maxima and minima. However, both the methods yield almost the same results at high impact energies. Page(s): 122-133

On the Cause of Day-to-day Variability in the F-region Electron Concentration

2016-11-16T09:05:56Z

Title: On the Cause of Day-to-day Variability in the F-region Electron Concentration Authors: Jain, A R; Mahajan, K K Abstract: The day-to-day variability in the electron concentration in the F-region is examined by analyzing the incoherent scatter data for St Santin (44.6°N; 2.2°E) for hours near midday (1000-1400 hrs LT) when quasi-steady- state conditions can be assumed, Large day-to-day variability, by as much as factor of 3, is noticed in the F-region and topside ionosphere. This variability is studied in relation to simultaneously measured values of ion drift velocities. No definitive correlation is seen between electron concentration changes and ion drift variations, except for winter months, where large downward velocities are correlated with low electron concentration, and -low downward velocities are correlated with high electron concentration. A large variability in electron concentration in the chemical equilibrium region (i.e. below about 200 km) is also observed. Although there is no one-to-one correlation between the electrons concentrations in the chemical equilibrium region with those in the F-region, yet large electron concentration values in the chemical equilibrium region are accompanied by large F-region values and vice versa. The electron concentration changes in the chemical equilibrium region indicate the possibility of neutral composition changes near the turbo pause level. Page(s): 119-221