Llif yr atmosffer drydanol dros begwn y gogledd: arsylwadau tomograffi radio a SuperDARN

The paper investigates the structure and behaviour of the nighttime ionised (electrified) atmosphere in the polar and auroral regions; the region where the aurora borealis occurs. Of particular interest are plasma structures on horizontal scales of hundreds of kilometres. The observations presented were made by the radiotomography experiment of the University of Wales, Aberystwyth, which has four satellite receiving systems in the high Arctic near the north pole, at Ny Alesund and Longyearbyen on Svalbard, Bjornoya (Bear Island) and Tromso on mainland Norway. Comparisons of tomography images with observations of plasma flow by the international SuperDARN radar suggest that large density plasma produced on the dayside flows across the polar region and into the night sector. The results contribute to the interpretation of physical processes that couple the Earth's environment with space, and are also of interest to users of radio systems where the ionised atmosphere can degrade the propagation of the signals.