Simulating Electric and Magnetic Fields from Dust Devils

Dust storms have been observed to generate significant DC electric fields. Dust devils specifically are a subset of dust storm, with an ordered sense of rotation about a central axis. Observations in Arizona and Nevada have recorded both electric and magnetic fields associated with dust devils. These electromagnetic signatures are important for future space exploration, with charged dust presenting issues for solar power generation and optics as well as the possibility of communication disruption. The likelihood of lightning from dust devils also has implications for the origin of life, and the chemical composition of the Martian surface and atmosphere.Building upon terrestrial observations of dust devils, and other properties of triboelectrically charged particles, a lumped particle methodology for the generation of electromagnetic fields based on fundamental laws of physics is presented. In this model, the particle motion is constrained to a simple harmonic motion, tracing a circle in 2D, with parameterised relationships for the height variation of the dust devil, the charge profile with grain height and the velocity of the rotational motion determined.Results from the simulation of a dust devil with 3.5 metre radius are compared to the measurements from a terrestrial dust devil of the same size. With a tuned surface electron density input to an event-driven tribocharging model, calculated electrical and magnetic fields are within a factor of two of the measured values. An idealised 3.5 m radius dust devil with its centre passing directly over magnetic and electric field sensors, has an electric field approaching the terrestrial breakdown field strength. This is consistent with recent observations of electric discharge in the vicinity of a dust devil in the UAE. The vertical and horizontal variation of the electric and magnetic field in the vicinity of the dust devil can now be predicted, and the model can readibly be used to interpret field observations on Earth, lander measurements on Mars, and predict signals in future instrument deployments to inform sensor design.