Sudden Absorption of Atmospherics due to Increase in Cosmic Ray Intensity

Journal/Book: Reprinted from Nature Vol. 178 pp. 277-278 August 4 1956. 1956;

Abstract: Electronics Research Directorate Air Force Cambridge Research Center L. G. Hanscom Field Bedford Mass. June 11. An effect of the solar flare and cosmic ray increase of February 23 reported by several observers1-4 was recorded an the atmospheric noise study apparatus located at the U.S. Air Force Cambridge Research Center site at Fourth Cliff in Scituate Mass. The sudden absorption of energy that occurred is of interest because it was recorded during the night. The night-time absorption appears to be directly related to the cosmic ray increase. The apparatus consisted of a whip antenna feeding a receiver set at a frequency of 49 kc./s. The output of the intermediate-frequency amplifier was fed into a probability computer designed and built by the University of Florida. A milliammeter recorded the percentage of time that the electric field intensity exceeded the threshold voltage set an the computer. The level an the accompanying illustration is such that an Input of 2 µ.V. exceeds the threshold voltage 50 per cent of the time when the chart time reads at the middle of the scale. The time constant of the unit was 16 sec. Fig. 1 illustrates the absorption of signal taking place at approximately the time of observation of the flare. The exact sequence of time was as follows: The flare was observed in Tokyo at 0334 U.T. February 23. At 0340 U.T. an S.I.D. was reported. The drop in signal-level of the 49 kc./s. atmospherics started at 0344 a few minutes earlier than the beginning of the cosmic ray increase noted at 0348 at Cheltenham 0350 3 at Chicago and 0353 at Godhavn Greenland. At 0343 Pierce and Moritz4 observed at Cambridge Mass. an increase in the rate of change of phase of 16 kc./s. signals from Rugby England. The time lapse involved between the S.I.D. and the sudden absorption of atmospherics (4 min.) and the fact that the event occurred at 2244 local time seems to indicate that the disturbance observed was produced by the cosmic ray increase rather than being connected with the S.LD. produced by the ultraviolet. Considering the geometry of the situation it seems unlikely that the decrease in signal-level was due to the increase in absorption of atmospherics in the sunlit portion of the globe because observations were made around the period of local midnight. ... ___MH

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