The Relation between Radio-Transmission Path and Magnetic-Storm Effects

This paper presents the results of a quantitative study of the relationship between the proximity of great-circle transmission paths to the magnetic pole and of signal stability during terrestrial magnetic disturbances. Reception from Europe as observed at Riverhead, Long Island, and San Juan, Puerto Rico, is compared during normal and disturbed periods. The great-circle path from Europe to San Juan is about 1000 miles farther from the north magnetic pole than a similar path to Riverhead. A brief description of the duplicate equipment and antenna systems employed at the two locations is included. It has been known for some time that the more southerly transmission paths are apparently less susceptible to effects accompanying magnetic disturbances. The results of observations covering a period of years confirm the anticipated relationship between signal stability and proximity of the transmission path to the magnetic pole. The average advantage of San Juan over Riverhead for European signals during disturbed periods is found to be approximately 8 decibels. Evidence of higher ionospheric ionization over the more southerly path is noted in a number of cases by a comparison of nighttime cutoff effects and allied phenomena.