PhD research

Modelling the dynamics of charged dust in planetary rings

PhD research
PhD research

My research focuses on charged dust dynamics in planetary rings, an example phenomenon being the spokes of Saturn, transient ~radial dust clouds lofted away from the ring plane by electromagnetic forces and shown by Cassini's wide angle camera below.

Cassini movie
[Image credit: NASA/JPL/Space Science Institute]

I use numerical methods and algorithms to model the behaviour of dust in orbit around Saturn, particularly focussing on the phenomenon of ring rain, a cleansing mechanism which could make the rings appear more youthful than they are. I relate the complex orbital outcomes of charged grains to observations of H3+ emission, a proxy for water influx from the rings into the planet's upper atmosphere. Understanding the relative fraction of non-ice to ice grains precipitating along magnetic field lines onto the planet is key to understanding the age of the rings, as this so-called ring rain could be a cleaning mechanism whereby silicate/tholin/haematite material could be preferentially removed from the rings,

A grain's trajectory is solved by simultaneously integrating its position and velocity using an adaptive Runge-Kutta integrator, and the time-variable charge using a stochastic algorithm with binary tree traversal to handle multiple currents in Saturn's plasma environment.

Eg simultaneous integration Eg binary tree Eg grain trajectory
Below I show a batch of simulations reproducing Jontof-Hutter (2012)'s results (LHS) for the orbital outcomes for grains (unstable: collision with planet/escape from system or stable: remain in orbit/reach high elevation) of different charge-to-mass ratios and launch positions in Saturn's dipolar field.
Stability map

Resonant features are also present (the diagonal suite of sims for intermediate charge-to-mass ratios in the q<0 figure above), e.g. when the epicyclic frequency is an integer multiple of the mirror bouncing frequency (κ = 2Ωb):

Eg resonance

I make spirographs amongst other things!