NOPR Collection:

Recovery Effect in the Field Intensity of Atmospherics

Tue, 01 Feb 1983 00:00:00 GMT

Title: Recovery Effect in the Field Intensity of Atmospherics Authors: Bhattacharya, A B; Bhattacharya, R Abstract: Integrated field intensity of atmospherics at 10, 20 and 30 kHz observed over Calcutta for a 3-yr period is analyzed to explore the recovery effect. The results exhibit a significant seasonal change in the amplitude of the recovery effect as well as the time difference between the occurrences of the peak value of this effect and the start of the sunrise fall. The duration of the effect and its frequency spectrum are also considered. The results are interpreted by considering the existing knowledge of source activity and propagation effect. Page(s): 30-32

Development of a New Rubber-based Microwave Absorbing Material

Tue, 01 Feb 1983 00:00:00 GMT

Title: Development of a New Rubber-based Microwave Absorbing Material Authors: Mathew, K T; Nair, K G Abstract: A study on a set of rubber compounds with graphite, carbon, ferrite, nylon and coir-fibre reveals that absorption of 99% of the input power is possible with compound containing 35% graphite, 25% carbon and 40% dry rubber. Experimental data at different frequencies are provided. Page(s): 28-29

Height Distribution of Refractivity Structure Constant from Radiosonde Observations

Tue, 01 Feb 1983 00:00:00 GMT

Title: Height Distribution of Refractivity Structure Constant from Radiosonde Observations Authors: Pasricha, P K; Mohan, Mahendra; Tiwari, D K; Reddy, B M Abstract: Radio refractivity structure constant C and its height distribution under varied meteorological conditions are evaluated from routine radiosonde observations. The mixing length theory in conjunction with Tatarskii's theoretical formulation permits C evaluation from mean meteorological fields. The C values so deduced are normalized to the existing turbulence conditions, obtained through an empirical relationship between thermal atmospheric stability and a parameter that characterizes turbulence. Page(s): 23-27

Dispersion in Ionospheric Drift Records

Tue, 01 Feb 1983 00:00:00 GMT

Title: Dispersion in Ionospheric Drift Records Authors: Sardesai, D V; Rai, R K; Vyas, G D; Chandra, H Abstract: Cross-spectrum method of analysis is applied to nearly 500 F-region drift records obtained over Udaipur (geogr. lat. 24ᵒ 35'N), a low latitude station. It has been found that 21% records show a positive dispersion. The negative dispersion is rarely found though 15%, of the records show such tendency. Approximately 18% cause yield no dispersion. In most of the cases, the velocity is found to vary randomly with fading Fourier frequency. By introducing artificial positive velocity dispersion with time in a statistically sationary record, it is found that the resampled record, through its cross-spectral analysis. leads to positive dispersion of velocity with Fourier fading frequency which is proportional to the artificial dispersion introduced in it. This suggests that variation of velocity may be a cause for observed dispersion in drift records. The reliability fo skewness parameter in deciding dispersion in a drift record is also examined. Page(s): 18-22