A new inversion algorithm for backscatter ionogram and its experimental validation

Abstract. Oblique backscatter sounding is a powerful tool for detecting and monitoring the ionosphere continuously at a remote distance. High-frequency (HF) backscatter ionograms provide the amplitudes of backscatter signals with respect to group path or time delay against operating frequency. Application of inversion algorithm to a backscatter ionogram can extract useful information regarding the ionospheric electron density along the propagation paths. The present study proposes a new inversion algorithm on basis of simulated annealing method to acquire the leading edge of sweep-frequency ionogram, which is subsequently validated by ionospheric vertical sounding data. Quantitative comparisons between the vertical sounding measurements and the inversion results obtained from oblique backscatter sounding indicate that the new algorithm enables us to overcome the instability issue that traditional inversion algorithm faces and output reliable information of ionospheric inversion with satisfactory efficiency, thus providing a robust alternative for ionospheric detection based on oblique backscatter ionograms especially when the ionosphere is calm with slow changes.