September 16, 2019
A new article recently published in Physics of Fluid and authored by alumnus William McDoniel and ASE/EM Professors David Goldstein and Philip Varghese, investigates the interaction between Jupiter’s large plasma torus and the atmosphere of its Galilean moon, Io. The article was featured in Scilight this July.
Jupiter’s plasma torus—a ring-shaped cloud of ions and electrons—plays a large role in the planet’s magnetosphere. Its innermost moon, Io, which is encompassed by Jupiter’s torus, is highly volcanic, creating plumes that rise hundreds of kilometers from the moon’s surface. Mostly made up of sulfur dioxide, these neutral gas plumes emitted from Io supply material for Jupiter’s plasma torus.
One example is Pele, a 300-kilometer tall volcanic plume that creates a sulfurous fallout, depositing an enormous red ring on Io’s surface. Investigating the bombardment of these plumes by incoming ions from the plasma torus using computer models helped researchers explain the geometry and features of these deposition rings.
The team modeled Jupiter’s plasma torus and Io’s volcanic plumes using their own code developed at UT—appropriately named PLANET—and implemented the 3D direct simulation Monte Carlo (DSMC) method into their code. This computational method simulates the behavior of gas flow by tracking the motions and statistically based collisions of many millions of representative particles, which are still a very small fraction of the astronomically large number of real particles in the flow.
According to McDoniel, the major question the research group wanted to address is how Jupiter’s plasma torus is supplied with new ions. These research simulations demonstrated that the volcanic canopy becomes inflated when plasma bombards it.
“The most significant finding from this research is that the plasma hitting Io’s plume canopies can create a huge diffuse cloud of gas,” said McDoniel. “This gas can be ionized by interactions, such as with photons or electrons in the plasma, and the new ions would get picked up by Jupiter’s magnetic field.”
He says it’s also important to note that it’s not clear whether this is the dominant mechanism that resupplies the torus, and that sublimation of the atmosphere may also play a large role.
Using simulation models, the research team concluded that Jupiter’s plasma torus can significantly impact Io’s atmosphere and that the torus also explains the thickness of the red deposition rings observed on Io.
McDoniel says that Io’s interaction with Jupiter’s plasma torus is an interesting question that bears on the entire Jovian magnetosphere, which extends almost out to Saturn’s orbit, and that Io’s disturbance also plays a huge role in radio signals sent out from Jupiter. Answers to these kinds of questions could help scientists better understand the gas dynamics of planetary atmospheres.
View the full publication: Simulation of Io’s plumes and Jupiter’s plasma torus.
