Abstract
This paper describes scientific subjects important in the middle atmosphere in the polar region, considering the effects of phenomena unique to the high latitudes as well as the coupling processes between the neutral and ionized atmosphere. We are particularly pointing out the relevant application of an MST (mesosphere-stratosphere-troposphere) radar for observations of middle and lower atmospheric structure and dynamics. We briefly summarize fundamental techniques of the MST radar. Then, we survey phenomena that are exclusively detected in the polar atmosphere, such as precipitation of high energy particles, aurora) electrojet, stratospheric sudden warming, the polar vortex or a polar night-jet, PSC (polar stratospheric cloud) associated with ozone depletion and PMSE (polar summer mesospheric echoes), related to NLC (noctilucent clouds). Among these phenomena there are certain topics that need to be studied with an MST radar in addition to the multitude of other complementary experiments which are already applied for these studies in the Arctic and Antarctic. Finally, we discuss a realization of an MST radar operated on 50 MHz, which should be established in conjunction with the Svalbard incoherent scatter radar operated on 500 MHz.
