Non-propagating electric and density structures formed through non-linear interaction of Alfvén waves

摘要

In the auroral zone of the Earth, the electron acceleration by Alfvén wavesis sometimes seen as a precursor of the non-propagating accelerationstructures. In order to investigate how Alfvén waves could generatenon-propagating electric fields, a series of simulations ofcounter-propagating waves in a homogeneous medium is presented. The wavespropagate along the ambient magnetic field direction. It is shown that non-propagating electric fields are generated at the locus of the Alfvén wavescrossing. These electric fields have a component orientated along thedirection of the ambient magnetic field, and they generate a significantperturbation of the plasma density. The non-linear interaction of down andup-going Alfvén waves might be a cause of plasma density fluctuations (withgradients along the magnetic field) on a scale comparable to those of theAlfvén wavelengths. The present paper is mainly focused on the creationprocess of the non-propagating parallel electric field.