Statistical study on the HF radar multi-frequency autocorrelation functions

To fit the autocorrelation functions (ACFs) of HF radar ionospheric backscattered signal to an analytical function, which is obtained theoretically by introducing a Lagrangian description of turbulent motion, can estimate directly the turbulent parameters of the scatters. We use this method to analyze the HF radar ACFs. A statistical study has been performed with the multi-frequency data, and shown that the statistical results are not the same in different frequency bands. We found that the influences of the limit radar time resolution and the received noise played the important roles in causing this inconsistency, both of them result in an additional expansion to the spectral width, and cause more Lorentzian behavior to ACFs; these two limitations affect the form of ACFs more seriously in the higher frequency band. We verified this by a simple simulation.