Magnetosphere Magnetic Field Wobble Effects on the Dynamics of the Jovian Magnetosphere

Abstract

The Jovian magnetosphere is complicated by the multiple plasma sources and ion species present within it, as well as fast rotation with its dipole axis titled from its rotational axis. To date global models of Jovian have neglected the presence of the different ion species as well as the tilted nature of the dipole axis. This paper reports the results of the first multi-fluid global modeling of these effects in a single self-consistent study for processes occurring in the outer magnetosphere. In the inner magnetosphere the model densities are shown to be comparable to observed densities with much of the density variables due to the wobble. The wobble enables plasma to be transported to higher latitudes and then centrifugal acceleration leads to radial transport of the plasma. At the interface between the middle and outer magnetosphere, the wobble produces a sinusoidal modulation of the plasma properties, which yields at a fixed observing point two density peaks, each with the planetary period. However, because of solar wind forcing and the fast rotation of Jupiter, torques are exerted on the outer magnetospheric plasma such that the azimuthal speed between the southern and northern hemispheres are unequal. This leads to the asymmetric square wave modulation of the plasma properties in the outer magnetosphere such that only one density peak is seen each planetary period in the outer magnetosphere. This differential speed leads to reconnection in the tail at the planetary period and enhanced ejection of plasma down the tail at the planetary period. These processes could explain the periodicity seen in the New Horizons' data without the need for invoking arbitrary solar wind conditions. The energetic particles generated by these processes are shown to map to the arc-like structures seen in the dusk side auroral features.