Dispersive Alfvén wave phase mixing and focusing in a collisionless plasma
Laboratoire Lagrange, Observatoire de la Côte d’Azur.
Three-dimensional dynamics of dispersive Alfvén waves propagating in heliospheric plasmas that often support transverse inhomogeneities aligned with the ambient magnetic field are discussed based on amplitude equation modeling and direct numerical simulations of a fluid model that can capture non-collisional effects such as Landau damping and finite Larmor radius corrections. The waves undergo two main competing effects, namely phase mixing and focusing. The influence of the ratios of the pump wavelength to both the inhomogeneity transverse scale and the ion inertial length is in particular studied. It turns out that gradient formation can be enhanced by wave focusing which arises when the pump wavelength is larger than the scale of the transverse inhomogeneity. Consequences on the electron parallel temperature and the generation of a parallel electric field are also discussed.