Comparison of Modelled and Observed Ionospheric HF Radio Propagation over the Polar Cap in Response to Solar Flares and a Weak CME of January 2014

Space weather events can have a range of disruptive effects on the ionosphere, especially in the polar cap. This region is of growing importance for intercontinental air travel, lying across the shortest path between significant destinations, e.g, Washington-Beijing. Following these great-circle routes is increasingly desirable as travel time, cost and pollution is reduced. However, in the polar cap geostationary satellites lie below the horizon and both geographic and geopolitical considerations mean there are at best limited VHF radio air-traffic control facilities. Thus HF radio propagation via the ionosphere is of critical importance in maintaining communications with aircraft flying transpolar routings. Hence adverse space weather conditions, leading to ionospheric disruption which in turn affects HF radio propagation is of critical importance when considering whether a polar routing is viable in the days and hours in advance of a flight. [opening paragraph]