The variance and spectra of angle-of-arrival and Doppler fluctuations were estimated by using 105- and 400-MHz transmissions from the low-orbiting U.S. Navy navigation satellites observed at the Millstone Hill radar facility. A theoretical model for the variance and spectra was also construced by using the Rytov approximation and a power law power spectrum model for the electron density fluctuation. The model provided a means for the estimation of both the axial ratio and the location of the lower edge of the irregularity region, using only angle-of-arrival and Doppler observations made at a single location. Good agreement was obtained between the model estimates and observations. Analysis of data from two magnetic storms revealed simultaneous occurrences of E region and F region irregularities at invariant latitudes north of 56¿,