Ionospheric disturbance features in ionograms associated with low-latitude aurorae

Ionospheric disturbance features in ionograms during low-latitude aurorae was studied for two auroral events on 21 October and 17 November, 1989. Large scale periodic traveling ionospheric disturbances were observed by Japanese ionosonde chain with three remarkable wave fronts during the aurora on 21 October 1989. The growing phase of the waves was found from the variations in h\u27F values. This TIDs was estimated to originate from approximately 55-60 degrees in geographic latitude to the northwards of Japan. An increase of foF2 values due to an equatorial anomaly appeared from Okinawa to Akita for the magnetic storms on 21 October 1989. Concerning the spread-F phenomena it was peculiar that the ionospheric scintillations were rather weaker at northern station than southern station for both cases of ionospheric disturbance associated with auroral substorms on 21 October and 17 November, 1989