EP018-0013
Investigations of Magnetic Field Signals During Pressure Vortices at InSight

Wednesday, 9 December 2020
Poster
Shea Thorne, University of British Columbia, Department of Earth, Ocean and Atmospheric Sciences, Vancouver, BC, Canada, Anna Mittelholz, University of British Columbia, Department of Earth, Ocean and Atmospheric Science, Vancouver, BC, Canada, Catherine Johnson, University of British Columbia, Vancouver, BC, Canada; Planetary Science Institute, Tucson, United States, Ralph D Lorenz, Johns Hopkins University Applied Physics Laboratory, Laurel, MD, United States, Constantinos Charalambous, Imperial College London, London, SW7, United Kingdom, Steven P Joy, University of California Los Angeles, Department of Earth Planetary and Space Sciences, Los Angeles, CA, United States, Aymeric Spiga, LMD/IPSL, Sorbonne Université, Paris, France - Institut Universitaire de France, France, Palaiseau Cedex, France, Suzanne E Smrekar, Jet Propulsion Laboratory, Pasadena, CA, United States and William Bruce Banerdt, JPL/NASA/Caltech, Pasadena, CA, United States
Abstract:
Dust devils are generally a common phenomenon on Mars. At the InSight landing site pressure drops are a frequent occurrence, however dust-carrying vortices, (dust devils), have not been observed in InSight images. Dust devils have been observed on Earth and associated magnetic field signals due to triboelectric charging have been recorded. A passing pressure vortex that carries dust in suspension could be observed in the InSight magnetometer (IFG) data, with the magnetic signal resulting from either triboelectric charging or from shadowing of the solar arrays leading to a drop in the currents. IFG, the first surface magnetometer on Mars, offers a unique opportunity to observe pressure vortices and any concurrent magnetic signals. Previous InSight studies have examined magnetic signatures of a few selected vortices. In some cases, small magnetic field signals were observed, although their origin is unclear. In this study we systematically investigate vortices to identify the percentage that have a resolvable magnetic signature with respect to the background noise level. Using event durations of pressure drops greater than 1 Pa for which 2 Hz magnetometer data are available, we calculate the standard deviation in each magnetic field component during and around the event to obtain a signal-to-noise (SNR) value. The standard deviations are binned in local time for each component. The medians of local time bins during and around events are then compared to the median standard deviation at that local time over the mission. We find that signals during events are typically similar to the ambient variability in the field at the corresponding local time. Of the 699 vortices examined to date, only 4% have an SNR greater than 1 in any component. Events with resolvable magnetic signals show no correlation with specific local times, duration, and pressure drop magnitude. The dearth of clear magnetic field signals is consistent with the lack of observed dust devils at the InSight landing site to date. We analyze events with a high SNR for which high-frequency solar array current data are available to investigate the origin of dust devil associated magnetic field signals.
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