Observations of ionospheric radio propagations in the Arctic and the mid-latitude regions

Natural phenomena, such as solar flare and sporadic E layer, have some influences on radio propagation characteristics. Since radio waves are utilized for many broadcasting and communications systems today, it is important to observe the influences of the natural phenomena on radio propagations. And it is also useful to observe the radio propagations for a long term and in different propagation paths from the view points of understanding and investigating mechanisms of natural phenomena.