Scintillation of a Radio Star at a Subauroral Latitude

Abstract

Scintillations of the radio source Cassiopeia A observed at 113 Mc/s during the period October 1961 through July 1964 were scaled to determine a semiquantitative index ofthe scintillation of source power. For fixed values of local magnetic activity mean diurnal variations were established which peaked about two hours before solar and magnetic midnight. Mean sidereal variation peaked at lower transit; this effect, attributed primarily to latitude, is compared to satellite scintillations. Both diurnal and sidereal variations showed an increase of mean scintillation activity with increase of magnetic index. Detailed examination of low magnetic index periods showed that daytime scintillations were slightly higher on the western side (towards the magnetic pole), while nighttime scintillations showed symmetry. However, with increasing magnetic activity, scintillation indices are considerably higher at night in the west while daytime scintillations are skewed to the east. A comparison of these observations with Penndorfs model of traveling and permanent maxima of spread F is attempted. The general features of the diurnal‐latitude variation of the radio star scintillation index is compared to the diurnal and latitude variation of spread F (topside and bottomside). While there is a general correlation, differences between scintillations and spread F noted in topside sounders are considerable.