Enceladus as an Internal Plasma Source at Saturn and How this Affects the Global Magnetic Field Structure

Abstract:

It was discovered during the Cassini orbital mission of Saturn that the small moon Enceladus continually emits water vapor from geysers in its southern hemisphere. These neutral particles can become ionised and the newly formed plasma locks onto the magnetic field that is produced within Saturn’s interior. Due to the planet’s rapid rotation, the heavy plasma become centrifugally confined to the equator, thereby radially stretching the magnetic field into what is known as a magnetodisc. This field geometry is supported by an azimuthal current sheet that is carried by the internally sourced plasma.

We discuss some of the key features of the magnetodisc current sheet and how its presence perturbs the global magnetic field structure at Saturn. We identify a variable thickness and strength that suggests spatial and temporal variability are ubiquitous in the current sheet. We further show first evidence of a region where the structure breaks down, known as the cushion region, and suggest a new explanation for why it forms. These results are essential for modelling the Saturnian system and provide insight into the key differences between the gas giants Saturn and Jupiter, as well as the Earth.