EFFECTS OF SOLAR 10.7 CM RADIO FLUX AND SOLAR MAGNETIC-FIELD ON LOW-FREQUENCY SIGNAL PROPAGATION

Correlations of 40 kHz radio signal propagated over a long distance wi th the solar microwave radiation, geomagnetic activity and solar magne tic field have been studied. Superposed epoch method of analyses revea ls that (i) the day-to-day variations of the midday and midnight LF ea st-west propagation do not follow the day-to-day variation of the slow ly varying component of the 10.7 cm solar flux; however, the year-to-y ear solar cycle variation of this LF propagation with index of solar a ctivity, i.e. sunspot number is evident, (ii) the amplitude of LF sign al does not possess characteristic variation as that of geomagnetic ac tivity. (iii) the LF signal received does not exhibit satisfactory cor relation with the positive maximum of the mean solar magnetic field, b ut (iv) the amplitude of the 40 kHz signal shows a minimum around the negative maximum (dip) of the mean solar magnetic field. The correlati on coefficient between the negative solar magnetic field and the 40 kH z signal is found to be as high as 0.89.