Ionospheric Amplitude & Phase Scintillations at Multiple Frequencies

Abstract

Simultaneous scintillation observations for both amplitude and phase from the ATS-6 beacon experiments for signals at 40 and 140 MHz, recorded at Lindau (51'6°N; 10'1°E) have been analyzed. It has been found that a combination of 1 sec sampling period and a value of about 200 for the filter-coefficient for a digital high pass filter give reasonable value of scintillation index <i>S</i>4<i>. </i> The average value of spectral index <i>n </i> varies from 1'4 to 1'5 both in case of weak as well as strong scintillation cases. For a power-law irregularity spectrum of the form <i>K^-P, </i> the value of <i>p </i> derived from actual spectra varies from 3'5 to 4'9 for 40 MHz and from 3'2 to 4'2 for 140 MHz against the value of 3'6 predicted by <i>n </i> based on weak scintillation theory. The autocorrelation functions behave quite well in accordance with the expectations of the theory. For strong scintillation cases the data show broadening of spectrum and a relative difference in the behaviour of autocorrelation functions. The high frequency roll-off rate is sometimes smaller at 140 MHz than at 40 MHz which is contrary to the results published in literature. In the case of phase scintillations the slope of the spectrum varies from 2'1 to 2'6 and does not show any systematic trend as we pass from weak scintillations to strong ones.