Measurements of large irregularities in the total electron content of the daytime ionosphere

Abstract

Irregular variations in the measured position angle of the polarisation of 108 Mc/s transmissions from Vanguard I (1958 β2) are ascribed to large scale irregularities in the total electron content of the ionosphere which produce variations in the amount of Faraday rotation on ray paths traversing them. Estimates of the size of the irregular horizontal gradients of total electron content are made assuming a mean height for the irregularities. Results for three daytime observation periods are given in the form of distributions of occurrence frequency versus size of irregular gradients. An average size is a variation of 0.25 × 10 12electrons/cm 2 in total electron content over a horizontal distance of 100 km; this is of a similar magnitude to regular latitude and local time gradients of total electron content. The results are consistent with observations by other workers of travelling ionospheric disturbances having velocities close to 10 km/min.