Flares Associated with the 1960 November Event and the Flare Nimbus Phenomenon

Abstract

Outstanding flares occurred on November 10, 12, 15, and spot group which had its central meridian passage on November 12. The last three of these flares projected into space showers of cosmic rays which were registered on the earth by neutron monitors at ground level within 30 minutes after the flare flash, bringing up to ten the number of these events so recorded since February 28, 1942. Geomagnetic storms of unusual intensity also occurred on November 12 and 13, and again on November 15. The fiares of November 10 and 12 were photographed under excellent conditions on films taken at 1-minute intervals with the Lyot H alpha heliograph. These results are analyzed and flare light-curves are plotted. A new phenomenon--the flare nimbus ---was found in association with some Class 3 and 3 - flares recorded with the heliograph. This is a dark absorbing halo which begins to surround the flare some few minutes after the filaments have reached:heir maximum light intensity: its duration is>l-2 hours and its diameter is about 3 10,000 km. The characteristic properties of the nimbus are described for the five observed cases---July 16, 1959, April 1, June 1, November 10 and 12, 1960---and possible causes aremore » discussed. There is a strong presumption that the phenomenon is the optical counterpart of the cloud of relativistic electrons whose occurrence in the flare region was postulated in order to account for the radio emission continuum of Type IV. (auth)« less