Simulating the effect of Jupiter’s plasma torus on the volcanic plumes of Io

Jupiter is surrounded by a ring-shaped cloud of ions and electrons called a plasma torus, which plays a major role in the planet’s magnetosphere. Its moon Io has an orbit which is encompassed by and also supplies the material for the plasma torus. As a result of Io’s hundreds of volcanoes, giant plumes of mostly sulfur dioxide rise up hundreds of kilometers off its surface.

A new article investigates the interaction between this neutral gas from Io and the ions from Jupiter’s plasma torus. For instance, the Pele plume is a 300-kilometer tall volcanic plume whose sulfurous fallout leaves a giant red deposition ring on Io’s surface. The researchers wanted to model the bombardment of such plumes by incoming ions from the plasma torus to explain their features and the geometry of deposition rings.

They used a three-dimensional direct simulation Monte Carlo (DSMC) method to model Io’s plumes and Jupiter’s plasma torus. DSMC simulates the behavior of gas flow by extrapolating from the computed motions of a number of representative particles, whose collisions are statistically based.

The findings demonstrate that plasma bombarding the plume canopy has the effect of inflating it. Rather than a thin, dense layer of gas on top of the plume, the simulation showed a thicker, less dense cloud. The resulting deposition ring has a fuzzy appearance, which matches well with what has been observed on Io. The plume is also dense enough to shield the underlying surface from plasma bombardment.

The researchers conclude that plasma can significantly impact the gas dynamics above Io’s surface and should be included in future simulations.

Source: “Simulation of Io’s plumes and Jupiter’s plasma torus,” by William J. McDoniel, David B. Goldstein, Philip L. Varghese, and Laurence M. Trafton, Physics of Fluids (2019). The article can be accessed at http://doi.org/10.1063/1.5097961 .