Currents in Planetary Magnetospheres

Abstract:

Magnetospheric fields and plasmas confine and guide each other through various forces such as thermal pressure force, inertial force and the centrifugal force. Any imbalance between these forces results in a magnetic Lorentz force expressed through the deformation of the ambient field or equivalently the generation of electric currents in regions occupied by space plasmas. A knowledge of the large-scale current systems in a magnetosphere therefore provides valuable clues about the dominant physical processes operating in that magnetosphere. In addition, field-aligned currents transport linear and angular momentum over long distances such as the ionosphere and the outer magnetospheres of Jupiter and Saturn. An understanding of these current systems is therefore vital in characterizing the magnetosphere-ionosphere coupling processes.

In this presentation I compare and contrast the various current systems observed in planetary magnetospheres. I begin the survey by summarizing our knowledge of the global current systems in the Earth’s magnetosphere and review the contemporary ideas that explain their origin and dynamics.

Next I will explore the current systems present in the magnetospheres of Jupiter, Saturn, Uranus and Neptune. In addition to characterizing the magnetopause current, azimuthal ring currents (ARC) and the corotation enforcement currents (CEC) - which flow in the radial direction - I will also review our knowledge of the field-aligned currents in these magnetospheres. I will pay special attention to local time asymmetries in the distributions and strengths of the major current systems and relate them to internal and external processes.