Long-period pulsations in electron precipitation associated with hydromagnetic waves in the auroral zone

Abstract

In recent years X-ray fluxes at balloon altitude from electron precipitation on the auroral zone have come to be associated with geomagnetic disturbances resulting from current systems at ionospheric levels, such as those responsible for bays [Barcus and Brown, 1962] and micropulsations in the 5–30 second period range [Campbell, 1961; Campbell and Matsushita, 1962]. This letter calls attention to the association of another type of geomagnetic variation with electron bombardment of the atmosphere. The observations on which the letter is based were obtained during a high-altitude balloon flight launched from Macquarie Island, Australia, on January 10, 1962. The balloon instrument was at ceiling altitude (15 mb) from 1315 UT to 0350 UT of January 11, 1962, late in the geomagnetic storm which began at 0216 UT on January 10, 1962, and ended at 09XX on January 11,1962. With the onset of a major electron precipitation event at 1920 UT, the balloon instrument 300 km west-southwest of Macquarie Island recorded a substantial flux of X rays while a 27.6-Mc/s riometer on Macquarie Island recorded ionospheric absorption of cosmic radio noise amounting to 5.1 db. The time variations of the counting rate of the balloon-borne NaI scintillation counter and the ionospheric absorption are shown in Figure 1.