The Effect of Sudden Ionospheric Disturbances (S.I.D.'s) on 2·28 Mc/s Pulse Reflections from the Lower Ionosphere

Abstract

The effects of sudden ionospheric disturbances (S.LD.'s) on the complicated structure ()f ionospheric echoes obtained with moderately high sensitivity at 2·28 Mcls are described. The observations indicate that flares of classes 2 and 3 can produce high values of electron density near the base of the ionosphere. Mean electron density can exceed 1000/cm3 over the height range 60-75 km, where the greatest relative increase in ionization occurs. Nevertheless, the greater part of the S.LD. absorption of waves reflected from the E region or above still occurs above 85 km.