Apparent poleward motion of onsets of auroral absorption events

A study is made of nighttime auroral radio absorption events observed by riometers in the latitude range of λ = 67–76°. Individual events are shown to extend over this range with a tendency to occur later at higher latitudes. If the observed onset delay time is interpreted as a poleward expansion of the disturbance, the corresponding average velocity is 0.8 km/s. This velocity is consistent with the poleward motion observed during visual auroral substorms. The absorption events are compared statistically with energetic electron events detected by the Alouette I satellite.