Some Characteristic Studies of Sudden Cosmic Noise Absorption Phenomena

Abstract

During solar flares the electron density of the lower ionosphere (at heights between 65 and 100 km) increases considerably thereby increasing the ionospheric absorption (called the SCNA) during the flare event, as a function of time, which is found to be very well associated with the Increase of solar X-ray flux in the wavelength band of 1-10Ǻ. In the period 1963-70 several flare effects occurred on riometers operating at Delhi and these have been investigated (in all about 80 events). It is observed that during these events, the ionized layer thus produced seems to obey an effective attachment law in some cases and an effective recombination law in the rest of the events. Thus, two distinct phenomena are observed. The X-ray flux observed by satellites Explorer 33 and 35 for typical events is utilized to derive the ion production rate and hence absorption, which is compared with the observed absorption. It is observed that the calculated absorption from the X-ray data and the observed absorption during SCNA do not compare well. Also, the solar zenith angle dependence of absorption during some events has been quantitatively studied.