SEARCH FOR GEOGRAPHIC CONTROL ON THE OCCURRENCE OF MAGNETOSPHERIC ELF EMISSIONS

Search coil magnetometer data obtained directly in the magnetosphere on Ogo 5 and Ogo 6 have been studied extensively for possible evidence of man-induced stimulation of the two dominant electromagnetic emissions, chorus and plasmaspheric hiss. Analysis of chorus obtained during the first year of operation of Ogo 5 exhibits considerable variability with geographic longitude. However, there is little or no correspondence with the longitudinal dependance of Ogo 3 chorus previously reported. This discrepancy is explained in terms of the persistent nature of chorus which can lead to oversampling of the data. When oversampling is eliminated, the longitudinal variability of Ogo 5 chorus is adequately explained by normal statistical fluctuations. A search was also made for enhancements, onsets or quantum jumps in chorus emissions at frequencies related to harmonics of the earth's transmission lines. No significant effect was found. These and other results indicate that the totality of satellite data analyzed to date is consistent with a predominantly natural origin for chorus and plasmaspheric hiss.