Non-linear interacting Alfven waves in planetary magnetospheres (Invited)

Abstract:

Alfven waves play an important role in planetary magnetospheres as they communicate energy and momentum between the parent planets, the magnetospheres, and the moons within the magnetospheres. At the outer planets the interaction of the planetary moons with the magnetospheric plasma is generally sub-Alfvenic, which results in standing Alfven waves in the rest frame of the moon. The Alfven wave electromagnetically couple the moon to the ionosphere of the parent planet. If the amplitudes of the standing waves are very large, the reflections at the planetary ionosphere are non-linear and the reflected waves interact with the incident waves. This results in filamentation of the waves to smaller spatial and temporal scales. Similar processes occur also in the outer planets magnetospheres, where Alfven waves transport angular momentum from the planets' ionospheres into their magnetospheres. Counter-propagating Alfven waves along the magnetospheric field lines interact non-linearly and establish a turbulent cascade of waves with large spatial and temporal scales to smaller scales. In this presentation, we will review relevant observations, theoretical concepts, and numerical simulations of these phenomenae.