The Use of Radio Stars to Study Irregular Refraction of Radio Waves in the Ionosphere

The observations and the theory of radio star scintillation are reviewed, and the following conclusions are reached. 1) The frequency variation of amplitude and phase scintillations agrees with theory. 2) All observers agree that there is a marked increase of amplitude scintillation with increase in zenith angle. The Cambridge data agrees with theory, but the Manchester data does not. No available zenith angle data is adequate to determine the height of scintillation. 3) The available observations of phase scintillation are inadequate for almost all purposes. 4) At present, the Hewish method of locating height by comparing amplitude and phase scintillation is seriously hampered by lack of satisfactory observations. On existing data the method gives heights that are spread over a range of about five to one; all of these heights are above the E region and refer to nighttime scintillation. 5) All observers agree that there is a maximum of amplitude scintillation in the middle of the night. 6) In addition, Australian observers report a maximum of amplitude scintillation at midday. This is only weakly observed, if at all, in the northern hemisphere, where, however, observational conditions are different. 7) Australian observers report maxima of amplitude scintillation at the solstices and minima at the equinox, but observers in the northern hemisphere report little seasonal variation. 8) The rate of scintillation increases under magnetically disturbed conditions, due to increased drift velocity. 9) There is a good general correlation between the occurrence of radio star scintillation and spread F reflections.