Nonlinear Regularization of Parker Sonic Critical Point in Parker's Unsteady Solar Wind Model

This paper presents the first ever systematic theoretical formulation addressing the long-standing open issue of regularization of the singularity associated with the Parker sonic critical point in the linear perturbation problem for Parker's unsteady solar wind model. This development recognizes the necessity to go outside the framework of the linear perturbation problem and incorporate the dominant nonlinearities in this dynamical system. This task is accomplished by constructing a whole new theoretical formulation of Parker's unsteady solar wind model based on the potential flow theory in ideal gas dynamics, which provides an appropriate optimal theoretical framework for this purpose. The stability of Parker's steady solar wind solution is shown to extend also to the neighborhood of the Parker sonic critical point by going to the concomitant nonlinear problem.