The Position and Movement on the Solar Disk of Sources of Radiation at a Frequency of 97 Mc/s. III. Outbursts

Abstract

The apparent position and polarization of the source of solar radiation at 97 Mc/s. have been measured during six outbursts, for five of which data on the accompanying solar flares are available. Initially the apparent position of outburst and flare almost coincide, the outbursts usually being rather closer to the solar limb than the flare. As the outburst proceeds, its position rapidly changes, the apparent movement usually being towards, and sometimes off, the solar limb. The initial apparent displacement towards the solar limb and the subsequent movement can be explained if we assume that the outburst radiation is excited by some physical agency originating at the same time, and in the same region, as the flare, and moving outward through the corona. The velocity of such an agency would need to be between 500 and 3000 km./sec., and it is suggested that the corpuscular streams associated with sudden-commencement terrestrial magnetic storms are the initiators of outbursts. The polarization of the outbursts in the early stages is random. Often a second increase occurs, with elliptical, usually circular, polarization. On two occasions linear polarization has been observed in this later stage of an outburst. The relation between the changes in polarization and the associated changes in apparent position conform to the rule given in Part II of this series, that right-hand circular polarization arises in the region above a south magnetic pole and left-hand above a north pole, while linear polarization appears to originate above the central region of a bipolar group, the E-vector having a direction approximately along the axis of the spot-group.