Estimating traveling ionospheric disturbance propagation direction and speed using bistatic high-frequency oceanographic radars

The purpose of this investigation is to demonstrate how observations from a network of Coastal Ocean Dynamics Applications Radars (CODARs) can be used to derive the parameters of a traveling ionospheric disturbance (TID) in the mid-latitudes. It has previously been shown that the CODAR system could be used as bistatic single-frequency oblique ionospheric sounders capable of deriving suitable virtual height variations. However, the previous study did not attempt to estimate any TID parameters from those variations. Therefore, this investigation expands on their initial findings. We present results from 06 October 2020 to show a generalized derivation of the standard TID parameters of a possible Large Scale TID. This is done by comparing virtual height variations across four different CODAR stations located in New Jersey, North Carolina, Florida, and Texas, U.S. with transmission frequencies of approximately 4 MHz. The signal for each link is bistatically observed at Clemson University in South Carolina, U.S. This study also compares the four CODAR stations to three ionosondes located in Virginia, Florida, and Texas, U.S. Previous studies have shown similar derivations for speed and propagation direction; however, this work expands on those to include n stations rather than the standard three. This generalized solution to solve for horizontal velocity is derived from first principles to include n stations with n − 1 time delays. This problem is then solved using a linear least-squares solution. To validate our generalized technique, we compare it with two previously accepted methods to show that our technique gives nearly the same values for propagation velocity and direction.