Radar imaging of equatorial F region irregularities with maximum entropy interferometry

Radar interferometry with multiple collinear antenna baselines has been performed at Jicamarca, near Lima, Peru, and high-resolution images of plasma irregularities in equatorial spread F have been constructed from the data. The images represent the brightness distribution of the radar backscatter, which is the Fourier transform of the visibility or spatial cross correlation of the scattered radar signal on the ground. The visibility data are noisy and incompletely sampled, and we have used the maximum entropy method to perform the Fourier transform, making optimal use of the data available. Using the current antenna configuration at Jicamarca, the radar imaging technique is able to resolve structures within the radar beam that are just a few kilometers wide. By animating sequences of images, we can observe the evolution of ionospheric irregularities without confusing spatial and temporal variations.