2nd URSI AT-RASC, Gran Canaria, 28 May – 1 June 2018 A Comparative Analysis of Strong Scintillation I: Configuration-Space Simulations Charles L. Rino* (1) ,Charles S. Carrano (1) , Nicolay N. Zernov (2) , and Vadim E. Germ (2) (1) Institute for Scientific Research, Boston College, USA (2) University of St. Petersburg, St. Petersburg, Russia Abstract The parabolic wave equation (PWE) characterizes the inter- action of propagating electromagnetic waves with the iono- sphere. Equatorial plasma bubble (EPB) environments are particularly challenging because they present an extended highly inhomogeneous, anisotropic, structure. It is gen- erally assumed that developed intermediate-scale structure can be characterized by a spectral density function (SDF). However, structured regions that are sufficient homoge- neous to support an SDF characterization are embedded in larger background structures that define EPBs Numerical simulations of the propagation of an electromag- netic wave in an EPB environment generate realizations that potentially accommodate both background and stochastic components of the environment. However, this presupposes that one has a good representation of the environment. Fur- thermore, the objective is to obtain tractable characteriza- tions of observables that can be used for remote ionospheric sensing and evaluating or predicting the effects of propaga- tion disturbances on satellite communication and naviga- tion systems. Recent studies by Zernov and Gherm [1 - 3] have addressed these issues within the framework of hybrid analytical solutions to the problem. An alternative approach to the problem by Carrano and Rino [4] uses an equivalent phase screen, effectively to ab- sorb the complexity of the EPB environment. Further sim- plification is achieved by constraining the propagation ef- fects to a two-dimensional plane defined by the propaga- tion vector and the scan direction defined by the transla- tion of the propagation vector through the medium. The results are supported by an exact solution of the PWE for two-dimensional propagation of the field created by a two- component inverse-power-law phase SDF. The equivalent- phase-screen theory provides complete characterization of any intensity scintillation record in terms of 5 parameters. The best-fit parameters can be determined by the irregular- ity parameter estimation (IPE) procedure described in Car- rano and Rino [4]. This paper and a companion paper by Gherm, Zernov and Rino present a comparative analysis of the two approaches. Common configuration-space structure realizations with specified two-component inverse-power-law SDFs are used for the comparisons. The parameters selected for compari- son were derived from analysis of high-resolution EPB sim- ulation by Yokoyama [5]. 1 Configuration-Space Models Configuration-space models use scale-dependent field- aligned structure elements referred to as striations. The structure can be an ionization enhancement or a void in a background structure. Let ζ s − ζ k s represent distance along the k th field line. The initiation point is placed in a cross- field. Vector components parallel and normal to the field line in the plane of curvature, namely ζ k ‖ , and ζ k ⊥ , can be constructed at any point along a field line. Striations shapes are defined by monotonically decreasing functions of ei- ther distance along the field line, p s (ζ ), or radial distance, p ⊥ (|ζ |). The defining equation for a striation includes a fractional strength parameter, F k : ΔN k (ζ s , ζ τ )/N 0 = F k p s (   ζ s − ζ k s    /σ s ) × p ⊥ (   ζ τ − ζ k τ    /σ k ). (1) The parameter σ k determines the cross-field dimension or scale of the striation. A complete structure realization is generated by summing the contributions striations with specified fractional strengths, F k , sizes, σ k and reference locations ζ k s and ζ k τ : ΔN(ζ s , ζ τ )/N 0 = 1 N s ∑ k F k p s (   ζ s − ζ k s    /σ s ) × p ⊥ (   ζ τ − ζ k τ    /σ k ), (2) where N s is the total number of striations. Successive bifurcation is often invoked to describe the EPB structuring. Steep gradients are broken up by generating depletions flanked by higher density regions. Each new structure component bifurcates similarly, forming a struc- ture cascade. Successive bifurcation is captured by the fol- lowing scaling relation for σ j and the number of striations at each scale: σ j = σ max 2 −(J max − j) N j = 2 d− j for j = 1, 2, ··· , J max . (3)