Solar-terrestrial relations

The inter-relation of phenomena on the sun and in the earth's ionosphere has been studied in order to establish a causal dependence which could result from travelling solar particles. In addition to examining a variety of data from a number of sources, an extensive R.F. noise recording program was undertaken to provide information on those regions of the solar and terrestrial atmospheres from which optical data were not available. The occasions on which there was an influx of such particles into the earth's ionosphere were established from magnetic data, from optical observations of the Polar Aurora, and from H.F. and V.H.F. radio observations close to the Auroral Zone. On the basis of these data the ionospheric disturbances for a 12 month period were related to prior distinctive solar events that were considered capable of producing the high energy particles. The selection was made from the optical, spectroscopic and radio data available. It was found that solar flares, eruptive prominences, and disappearing filaments were the most frequent sources of Earth-reaching particles, and that large sunspots contributed only occasionally to ionospheric disturbances. Moreover, the radio noise data permitted a fairly reliable estimate of the particle velocities in the solar corona, which could be used to predict the probability of subsequent terrestrial effects of the ejected particles. A correlation coefficient of +0.65 was found between probabilities predicted from the solar information and observed ionospheric disturbances which occurred two or three days later. The observational evidence on the solar noise bursts and on ionospheric storms could only be explained on the basis of a considerable distribution of velocities for the particles ejected from the sun. It was shown that a Maxwellian distribution of corpuscular velocities was a probable one. Moreover, the observations indicated that particles are frequently emitted from the sun with a distribution of velocities, but that only in the case of very large phenomena are there sufficient particles with the high energies necessary to overcome the sun's gravitational field and reach the earth.Science, Faculty ofPhysics and Astronomy, Department ofGraduat