Nonlinear kinetic Alfvén wave with Poisson equation correction in the low aurora (Q1368956)

Properties of solitary kinetic Alfvén wave (KAW) with and without Poisson equation correction are discussed. As is known, KAW is that Alfvén wave form in which ions cannot follow the magnetic lines in their motion (their frozen-in status is not valid), because the wavelength perpendicular to the magnetic field is comparable to the gyroradius. So the polarization drift begins to be important. This causes a deviation from quasi-neutrality which is governed by the Poisson equation, an effect either neglected or taken into account only in the practice. Here the velocity of the solitary KAW is evaluated for both cases, and it is shown that it is much larger than the ion-acoustic velocity under conditions of the upper ionosphere in the auroral zone. Further, the electric and magnetic fields of solitary KAW have a kink-like structure, which causes a dominant electric field appearing in the small-amplitude depressive density soliton propagating perpendicularly to the magnetic field. For parallel propagation, the Poisson equation correction is shown to be important.