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.

[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.

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.

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 = 2Ω_b):

I make spirographs amongst other things!