Numerical study of density cavitations by inertial Alfvén waves

Abstract

In this manuscript, we study the localization and density cavitations using inertial Alfven wave (AW) and fast AW in the auroral ionosphere. We first develop a system of equations semi-analytically for both wave modes by using two-fluid model and then solve the model equations numerically using two-dimensional pseudo-spectral approach to analyze the localized structures and cavity formation at different instant of time. The ponderomotive force associated with the pump wave changes the background density and as the inertial AWs propagate through the modified density channel it gets localized. Therefore, the inertial AW splits up into filamentary/localized structures. A low frequency fast AW traveling through these complex structures created by inertial AW, is intensified having its own filamentary structures. The filamentary structures grow with time until the instability acquires steady state. We notice that the density cavities are also accompanied by the high amplitude magnetic fields. The amplitude of the strongest density cavity is estimated as ∼0.26n 0 (n 0 is unperturbed plasma number density). We also discuss the implications of the present study in the context of auroral ionosphere.