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Recently, Universal Software Radio Peripherals were installed at the McMurdo, Antartica, and Kodiak, Alaska, Super Dual Auroral Radar Network (SuperDARN) radars to replace existing synthesizer and receiver electronics. Each antenna in the radar arrays was connected to its own Universal Software Radio Peripherals input, which enables controlling the phase of the transmitted signal and sampling the received signals on each antenna. Received data are written to disk and simultaneously combined using beam forming to produce the standard SuperDARN data stream. The raw signal data from the individual antennas is retrieved from the radar sites and analyzed using an algorithm that fits a model signal based on the assumption of individual plane waves arriving from discrete angle bins in the field of view. With this analysis the target amplitudes and Doppler frequencies can be determined as a function of angle. In this paper, the theory behind the algorithm is developed, and synthetic test data are presented, as are real observations. Finally, the line‐of‐sight velocities determined from the data are used to estimate maps of the vector velocity field that produced them.

Frictional heating, frequently termed Joule heating, results from the difference in ion and neutral flows in the Earth's upper atmosphere and is a major energy sink for the coupled magnetosphere‐ionosphere‐thermosphere system. During disturbed geomagnetic conditions, energy input from the Earth's magnetosphere can strongly enhance ion velocities and densities, which will generally increase the rate of Joule heating. Previous theoretical and experimental studies have shown that small‐scale variations in Joule heating can be quite significant in the overall energy budget. In this study, we employ high‐resolution fitting of ion velocities obtained by Super Dual Auroral Radar Network (SuperDARN) coherent scatter, along with spatially resolved neutral wind data from the Poker Flat Scanning Doppler Imager, to examine the spatial and temporal structure ofFregion ion temperature enhancements, as well as changes in Joule heating rates due to the neutral wind. These results are compared to those obtained using Poker Flat Incoherent Scatter Radar in order to assess the validity of this analysis, with the objective of developing a method that can be applied to any current or future neutral measurements worldwide, thanks to the global coverage of SuperDARN. We examine the agreement between the ion temperatures predicted using the Scanning Doppler Imager‐SuperDARN method and the temperatures measured directly by Poker Flat Incoherent Scatter Radar and discuss possible reasons for any discrepancies. We observe significant spatial structure in both the ion temperature and Joule heating rates during periods of magnetic activity.

We examined the source region of dayside large‐scale traveling ionospheric disturbances (LSTIDs) and their relation to cusp energy input. Aurora and total electron content (TEC) observations show that LSTIDs propagate equatorward away from the cusp and demonstrate the cusp region as the source region. Enhanced energy input to the cusp initiated by interplanetary magnetic field (IMF) southward turning triggers the LSTIDs, and each LSTID oscillation is correlated with a TEC enhancement in the dayside oval with tens of minutes periodicity. Equatorward‐propagating LSTIDs are likely gravity waves caused by repetitive heating in the cusp. The cusp source can explain the high LSTID occurrence on the dayside during geomagnetically active times. Poleward‐propagating ΔTEC patterns in the polar cap propagate nearly at the convection speed. While they have similar ΔTEC signatures to gravity wave‐driven LSTIDs, they are suggested to be weak polar cap patches quasiperiodically drifting from the cusp into the polar cap via dayside reconnection.