Characteristics of TIDs Observed in the Bottomside Ionospheric F-region Using the TIDDBIT HF Doppler Sounder

HF Doppler sounders represent a low-cost and low-maintenance solution for monitoring wave activity in the F region ionosphere. HF Doppler sounders together with modern data analysis techniques can provide comprehensive traveling ionospheric disturbance (TID) characteristics, including both horizontal and vertical TID velocities and wavelengths across the entire spectrum from periods of 1 min to over an hour. Atmospheric and Space Technology Research Associates LLC has developed a new system called TIDDBIT (TID Detector Built in Texas), and data will be presented from a TIDDBIT system deployed in Virginia. Details of the analysis are provided by Crowley and Rodrigues [2012].

These results reinforce the relationship between atmospheric gravity waves (AGWs) and TIDs. The TID propagation azimuths rotate through 360 deg in 24 h, mimicking the rotation of the thermospheric winds but with approximately a 90 deg offset. The rotation of TID azimuths and thermospheric winds in Virginia is similar to that observed previously by other Northern Hemisphere systems [Crowley and McCrea, 1988] and opposite from the direction observed in Antarctica [Crowley et al., 1987]. These results illustrate the filtering effects that thermospheric neutral winds can have on the propagation of AGW. The completeness of the wave information obtained from the TIDDBIT system makes it possible to reconstruct the vertical displacement of isoionic contours over the 200 km horizontal dimension of the sounder array, and movies revealing the detailed shape and motion of isoionic surfaces will be shown. They resemble the surface of the ocean. Such information will be relevant for understanding the seeding of irregularities, as well as for several operational needs involving navigation, communication, and surveillance systems.