Mid-and Low-Latitude Ionospheric D Region Remote Sensing by Radio Atmospherics I: Forward Modeling and Field Measurement Validations

Radio atmospherics (sferics for short) are electromagnetic (EM) pulses discharged by lightning return strokes and can be used for D region remote sensing. A frequency-domain full-wave (FDFW) numerical model is developed to simulate sferics propagation in earth ionosphere waveguide (EIWG). For a certain sampling frequency, EM fields of sferics are decomposed into a series of plane waves in the spectral domain via 2-D spatial Fourier transforms. The magnetized cold plasma medium of ionosphere is divided into several thin layers with the arbitrary anisotropic dielectric constant for each layer. The EM fields at the sferics receiver site are evaluated by recursively computing the reflection and transmission matrices in all layer boundaries for all the plane wave components and performing 2-D numerical integration in the spectral domain. The earth flattening technique is adopted and the horizontal wave vector of each plane wave component is directly modified in the spectral domain to compensate for earth curvature effects. Interactions between plane waves and the magnetized cold plasma of ionosphere are analyzed and discussed. Comparisons between the FDFW computation and finite-difference time-domain simulation as well as field measured sferics are implemented to verify the accuracy and reliability of the proposed new model.