Electric and magnetic signatures of dust devils from the 2000–2001 MATADOR desert tests

Abstract

Dust devils are significant meteorological phenomena on Mars: They are ubiquitous, continually gardening the Martian surface, and may be the primary atmospheric dust‐loading mechanism in nonstorm seasons. Further, dust grains in the swirling dust devils may become electrically charged via triboelectric effects. Electrical effects associated with terrestrial dust devils have been reported previously, but these were isolated measurements (electric fields only) with no corroborating measurements. To study the fluid and electrical forces associated with dust devils, NASA's Human Exploration and Development of Space (HEDS) enterprise sponsored a set of desert field tests with a suite of mutually compatible and complementary instruments in order to determine the relationship between electric, magnetic, and fluid forces. The project (originally a selected flight project) was entitled “Martian ATmosphere And Dust in the Optical and Radio” (MATADOR). In this work, we present a number of interesting examples of the electromagnetic nature of the dust devil. We also describe potential hazards of the dust devil and how similar devil‐ and storm‐related forces on Mars might affect any human occupation.

Quasi‐electrostatic field analysis and simulation of Martian and terrestrial dust devils

“…The time evolution of space charge density is very similar to the initial accumulation of the thunderstorm space charge in the QE heating model before a conventional breakdown is reached [Pasko et al, 1997]. This maximum electric field for a typical terrestrial dust devil is difficult to compare with experimental measurements, all of which have strongly saturated at a few kV/m [Freier, 1960;Crozier, 1964Crozier, , 1970Farrell et al, 2004], but the predicted value of 150 kV/m is not inconsistent with these measurements. Very recently, Jackson and Farrell (submitted man- Melnik and Parrot [1998], the dissipation of dust grain charge due to atmospheric conductivity is fully considered in our FE simulation.…”

“…The modeled terrestrial dust devil electric field reaches breakdown value (3 MV/m) in less than 5 min. This model predicts unlimited growth of dust devil electric fields that are not consistent with past observations of terrestrial dust devils, where only a maximum electric field of a few kV/m has been observed [Crozier, 1970;Farrell et al, 2004]. Most recently, Jackson and Farrell (submitted manuscript, 2005) measured near 120 kV/m QE fields of dust devils with a carefully calibrated electrometer.…”

“…The height and diameter of this generator region can be specified arbitrarily and we assume that the generator region fills the entire dust devil. Although more complicated charge structures can be included in this model, the dipole model of a dust devil is thought to be reasonable and has been used to estimate space charge densities [Crozier, 1964;Farrell et al, 2004]. The dipole charge model has a uniform distribution of negative space charge density at the dust devil top and a uniform distribution of positive space charge density at the dust devil bottom in a modeled cylindrical dust cloud.…”

“…On the basis of the findings in previous work, our goal in this paper is to connect these two different pictures by incorporating the charge dissipation of individual dust grains. Specifically, we derive a maximum electric field within a dust devil in simple terms and develop a realistic numerical model to study the electric fields of Martian and terrestrial dust storms, to predict potential electric discharges that may challenge future human explorations on Mars [Farrell et al, 2004;Beaty et al, 2005].…”

“…[3] Past in situ measurements suggest that large electric fields (bigger than 4 kV/m where many instruments have saturated and has been recently measured to be near 120 kV/m) exist in terrestrial dust devils [Crozier, 1970;Farrell et al, 2004] (see also T. L. Jackson and W. M. Farrell, Electrostatic fields in dust devils: An analog to Mars, submitted to IEEE Transactions on Geoscience Remote Sensing, 2005) (hereinafter referred to as Jackson and Farrell, submitted manuscript, 2005). Recent numerical and analytical studies show that the micro-electro-aerodynamical system of a dust devil is an efficient giant electric generator that may trigger Martian electrical discharges and radio emissions Parrot, 1998, 1999;Farrell et al, , 2003.…”