SIMULTANEOUS BALLOON MEASUREMENTS OF AURORAL X-RAYS DURING SLOWLY VARYING IONOSPHERIC ABSORPTION EVENTS

In the present paper we report the results of simultaneous balloon measurements of auroral X-rays in northern Scandinavia during slowly varying ionospheric absorption events. It is found that during typical events the electron precipitation starts north of L = 6·5 and spreads southwards to at least L ≈ 4·5 with speeds of about 500 m/s. The events apparently have a large longitudinal extension with the southern border aligned almost geomagnetically east-west. After the expansion the electron precipitation seems to decay uniformly over the area which was covered during the expanding phase. Faster pulsations are often observed superimposed on the general trend of the events and microbursts are probably always present. © 1968.