Movement of Auroral Echoes and the Magnetic Disturbance Current System

Abstract

A NUMBER of workers have reported systematic movement of very high-frequency radar echoes associated with auroral ionization. Bullough and Kaiser¹ at Jodrell Bank in England interpreted their results as indicating a westward movement before 2100 hr. local time and eastward thereafter. Unwin² at Invercargill in New Zealand, with an aerial directed 20° east of geomagnetic south, recorded radial motions which were northward before about 2230 hr. local time on the average, and southward thereafter. These results are consistent with those of Bullough and Kaiser. Recently, Nichols³ in Alaska has recorded Doppler shifts with two aerials directed 30° each side of geomagnetic north, from which it was possible to determine an absolute direction and velocity. On most occasions the major component was in an east-west direction. Bullough et al. ⁴ at Jodrell Bank and Gadsden⁵ at Invercargill have found a very good correlation between the occurrence of echoes and local magnetic activity. Further, Kaiser⁶ found a good correlation between the mean component of radial velocity of echoes (in a direction 50° west of geomagnetic north) arid the mean vertical component of the magnetic disturbance vector at Eskdalemuir for the days on which echoes were observed at Jodrell Bank.