Parametric variations of dromion solutions in auroral plasmas

摘要

Recent high resolution measurements of POLAR and FAST satellites have revealed two dimensional coherent structures in the polar cap boundary layer region. The challenge remains to propose an adequate model for those two dimensional structures. The authors' previous work (2002) have revealed exciting possibilities to explain such coherent monopolar and bipolar pulses on the basis of the novel two dimensional nonlinear structures called dromions. Dromions are localized, nonlinear, two dimensional structures with an exponential decay in both space dimensions and are characterized by time-dependent boundary conditions. They arise as exact solutions of a class of two dimensional nonlinear partial differential equations and may be considered as an extension of familiar one dimensional solitons. Considering the nonlinear evolution of electron acoustic waves in two dimensions, the authors were able to find an exact analytical solution for dromions for a relevant set of physical parameters in auroral plasmas.