THE EFFECT OF SOLAR-WIND DYNAMIC PRESSURE CHANGES ON LOW AND MIDLATITUDE MAGNETIC RECORDS

Magnetic records from low and mid latitude stations have been examined to determine their response to solar wind pressure changes. The best correlation between ground level changes and the change in the square root of the solar wind dynamic pressure occurs for stations at latitudes from 15-degrees to 30-degrees such as Tahiti, Honolulu, San Juan and Midway. The horizontal component of the field changes on average 16.5 nT for each change of 1(nPa)1/2 of the square root of dynamic pressure. This is 50% greater than the vacuum model of Tsyganenko would predict for a non-conducting Earth and therefore what would be expected for a perfectly conducting interior. Thus, low and mid latitude ground level response to solar wind pressure changes is dominated by the variation of the strength and location of the magnetopause current system and the corresponding induced currents within the Earth rather than ionospheric current sources.