This proposal will improve techniques used by the fifteen SuperDARN radars to determine in real-time the critical frequency and layer height at the ionospheric reflection point. These observations will be made over large geographical regions that are currently sparsely sampled by ionosondes. This effort represents a new use of the SuperDARN system in "sounding mode." This new mode of operation has been developed and implemented by the PI at the Kodiak radar. The sounding mode exploits the pause time (~10 sec) during the normal azimuth scan mode, making use of ground reflections to determine the skip distance of rays at various frequencies. By determining how the skip distance varies with frequency, it will be possible to find the maximum useable frequency as a function of ground range. The PI's main goals involve six distinct research activities: (1) modification of current SuperDARN software to include angle-of-arrival (AOA) information in the real-time data stream; (2) use of sounding mode data to determine real-time ionospheric critical frequencies and layer heights; (3) use of critical frequency determinations to observe, track, and study the dynamics of large-scale high latitude ionospheric density irregularities; (4) distribution of SuperDARN real-time foF2 values and virtual heights to the space weather community via the internet; (5) continued development of the SuperDARN sounding mode technique; and (6) use of sounding mode data to optimize the operating frequency at each SuperDARN radar.
