Modeling and scientific application of scintillation results


  • E. J. Fremouw,

  • J. A. Secan


Efforts continue to update and improve empirical models of the mean morphological behavior of ionospherically produced scintillation. While often intended for engineering application, these models also can be scientifically useful to the extent that they describe not only the signal fluctuations but also the plasma density irregularities that cause them. Such a model is contained in the computer code called WBMOD, which employs the phase screen propagation theory to calculate the power law spectral index and strength (at a fluctuation frequency of 1 Hz) of phase scintillation and the standard deviation of phase, for a user-specified system. Explicit provision is made for an ionospheric outer scale, but the relevant phase spectrum is cut off by a system parameter in most applications. The intensity scintillation index S4 is calculated from weak-scintillation theory and corrected for the saturating effect of multiple scatter on the basis of Rice statistics. The irregularity model in WBMOD describes three-dimensionally anisotropic (sheetlike) irregularities on the nightside of the high-latitude scintillation zone and axially symmetric (rodlike) irregularities elsewhere. The current status of WBMOD, which is undergoing continued refinement, is described in this paper for all latitude regimes. Plans for future development of its irregularity model are stated, and it is suggested that such models should now move in the direction of incorporating irregularity dynamics.