Investigation of Total Absorption of Radio Waves in High Latitude Ionosphere

Using the digisonde data observed at ionospheric station Norilsk (Dip lat. 60 o N) in 2006, a statistical study on the characteristics of the ionospheric plasma total absorption of radio waves (IPTAR) was performed. In the winter and some months of equinox, the IPTAR mainly occurred in the nighttime and the highest occurrence rate could be up to 90%. In the summer, the occurrence was relatively low and the differences between nighttime and daytime occurrence reduced. The total duration of IPTAR seemed longer around the winter than that around the summer. The occurrence of IPTAR events ascended as the Kp index increased. The frequent precipitation of energetic particles into the ionospheric plasma in the auroral belt may be the main cause of the IPTAR events.