Finite Difference-Time Domain Propagation in Randomly Structured Ionization

THE ACCURATE CHARACTERIZATION OF RF SIGNAL STRUCTURE DUE TO PROPAGATION THROUGH THE NUCLEAR DISTURBED IONOSPHERE IS ESSENTIAL FOR THE PERFORMANCE ASSESSMENT OF, AND MITIGATION DEVELOPMENT FOR, COMMUNICATIONS AND RADAR SYSTEMS. TRACTABLE SOLUTIONS TO THE GOVERNING EQUATIONS HAVE BEEN FOUND FOR MANY IMPORTANT PROPAGATION REGIMES BY APPLYING A SERIES OF STANDARD APPROXIMATIONS. WHERE NO SUITABLE APPROXIMATIONS EXIST, THE STANDARD APPROXIMATIONS ARE SPECULATIVELY PUSHED INTO THE INVALID REGIME. EXAMPLES INCLUDE THE APPLICATION OF PARABOLIC EQUATION RESULTS TO HF PROPAGATION (CONTRADICTING THE ASSUMPTION THAT THE WAVELENGTH IS SMALL RELATIVE TO THE FIELD CORRELATION LENGTH) AND THE EXTRAPOLATION IN DNA'S SATCOM AND SPACE RADAR RWC SIGNAL SPECIFICATIONS TO PROPAGATION ALONG THE GEOMAGNETIC FIELD (LIKELY VIOLATING MARKOV AND "THICK MEDIA" ASSUMPTIONS). THE QUESTIONS REMAIN: HOW FAR CAN THE STANDARD APPROXIMATIONS BE PUSHED? DO THE APPROXIMATIONS BREAK DOWN GRACEFULLY? THESE QUESTIONS CAN NOW BE EXPLORED USING THE FINITE DIFFERENCE - TIME DOMAIN (FDTD) METHOD. WE HAVE RECENTLY SHOWN THAT THE FDTD METHOD CAN BE APPLIED TO PROPAGATION IN THE IONOSPHERIC PLASMA AND WE NOW POSSESS THE ONLY ALGORITHM CAPABLE OF ADDRESSING THE ABOVE ISSUES. OUR PHASE I EFFORT WILL ENCOMPASS DEVELOPING THE NECESSARY CODES, PERFORMING INITIAL CALCULATIONS, AND DEFINING THE REQUIREMENTS FOR A FULL PHASE II ANALYSIS.