Frequency-and-angular HF sounding and ISR diagnostics of TIDs

A single digisonde, used as a receiver for ionospheric high frequency signals from broadcast stations, was able to determine the wave characteristics of traveling ionospheric disturbances (TIDs) using frequency shift and arrival angle measurements. During a measurement campaign, aimed at recovering large‐scale wave‐like processes in the upper atmosphere, in March 2001 at the MIT Haystack Observatory (Millstone Hill, MA), a Digisonde Portable Sounder (DPS) made simultaneous observations with the incoherent scatter radar (ISR). The DPS was upgraded to include the frequency and angular sounding (FAS) technique previously developed at the Institute of Radio Astronomy in Kharkov, Ukraine, for TID diagnostics. The DPS with four spaced receive antennas received the radio signals at 3.33 MHz and 7.335 MHz from Radio CHU of the Canadian Time Service (Ottawa, Ontario). The FAS technique recovered the basic parameters of TIDs, i.e., amplitude, speed, and the direction of the propagation vector by modeling the ionosphere as a perfectly reflecting surface. For three days during the campaign the Millstone Hill ISR monitored the ionospheric midpoint using a triangulation mode to identify the direction of motion and speed of the wave‐like ionospheric disturbances. Comparison of the results from the two diagnostic techniques showed good agreement. The wave directions were within 10 to 15 degrees, and speed and wavelength were within 10 to 12%.