Efficient ray tracing through a realistic ionosphere

An algorithm for accurate threehdimensional ray tracing is presented for realistic, nonspherical ionospheric electron density distributions, ignoring effects of the magnetic field. At the start of each ray path increment a truncated Taylor series expansion of the electron density results in a computationally efficient, closedhform solution of the EulerhLagrange equations for the increment. The technique is applied to computations of ray paths in a nonspherical ionosphere which is specified by a climatological model used for HF overhthehhorizon lOTHr radar studies. The effects of tilts in a sunrise transition region on signal losses and ray path deviations are found to be substantial. Results of various ionospheric approximations used for singlehsite transmitter location are calculated.