Auroral Absorption of 18-Mc./s. Cosmic Radio Waves on February 11, 1958

Abstract

ON the night of February 10–11, 1958, a spectacular auroral display was widely observed in the United States. Fig. 1 shows the effect of this aurora on 18-Mc./s. cosmic noise from the sky, as observed at the Sampson Station of this Observatory (lat. 42° 47′ N., long. 73° 27′ W.). The vertical scale indicates approximate relative absorption of cosmic noise in decibels as received. The horizontal scale gives Universal Time on February 11. The dotted line represents the record of the following night, February 12, which itself shows at 7hr. U.T. a characteristic dip which we consider to be associated with auroral activity. The peak at 0915 is a calibration mark. We note that the time marks, which are produced every 10 min. from WWV signals at 5 Mc./s., fade out at 0250 for the remainder of the night.