Applications of Electrified Dust and Dust Devil Electrodynamics to Martian Atmospheric Electricity

Abstract

Atmospheric transport and suspension of dust frequently brings electrification, which may be substantial. Electric fields of 10 kV m −1 to 100 kV m −1 have been observed at the surface beneath suspended dust in the terrestrial atmosphere, and some electrification has been observed to persist in dust at levels to 5 km, as well as in volcanic plumes. The interaction between individual particles which causes the electrification is incompletely understood, and multiple processes are thought to be acting. A variation in particle charge with particle size, and the effect of gravitational separation explains to, some extent, the charge structures observed in terrestrial dust storms. More extensive flow-based modelling demonstrates that bulk electric fields in excess of 10 kV m −1 can be obtained rapidly (in less than 10 s) from rotating dust systems (dust devils) and that terrestrial breakdown fields can be obtained. Modelled profiles of electrical conductivity in the Martian atmosphere suggest the possibility of dust electrification, and dust devils have been suggested as a mechanism of charge separation able to maintain current flow between one region of the atmosphere and another, through a global circuit. Fundamental new understanding of Martian atmospheric electricity will result from the ExoMars mission, which carries the DREAMS (Dust characterization, Risk Assessment, and Environment Analyser on the Martian Surface)-B R.G. Harrison

Long‐term variability of dust optical depths on Mars during MY24–MY32 and their impact on subtropical lower ionosphere: Climatology, modeling, and observations

“…The dust particles can absorb ions in the troposphere, which can produce large electric fields during dust storms [ Harrison et al ., ; Haider et al ., ]. To study the effect of dust on ions, we have calculated positive and negative ion densities of 14 ions viz., O 2 + CO 2 , H 3 O + , H 3 O + H 2 O, H 3 O + (H 2 O) 2 , H 3 O + (H 2 O) 3 , H 3 O + (H 2 O) 4 , CO 3 − , CO 4 − , CO 3 − (H 2 O), CO 3 − (H 2 O) 2 , NO 2 − (H 2 O), NO 2 − (H 2 O) 2 , NO 3 − (H 2 O), and NO 3 − (H 2 O) 2 between altitude 0 km and 70 km in the presence of first major dust storm ( τ = 1.7), second major dust storm ( τ = 1.2), regional dust storm ( τ = 0.5), and the absence of dust storm ( τ = 0.1) at Ls = 210°, 280°, 220°, and 150°, respectively.…”

“…The dust particles can absorb ions in the troposphere, which can produce large electric fields during dust storms [Harrison et al, 2016;Haider et al, 2010] tude 0 km and 70 km in the presence of first major dust storm (τ = 1.7), second major dust storm (τ = 1.2), regional dust storm (τ = 0.5), and the absence of dust storm (τ = 0.1) at Ls = 210°, 280°, 220°, and 150°, respectively. The total positive ion density is obtained from the sum of major ions, and 150°and τ = 1.7, 1.2, 0.5, and 0.1, respectively.…”

“…Dust particles become charged in dust devils, due to friction with each other. Smaller particles become negatively charged, while larger particles attain positive charge [ Michael et al ., ; Harrison et al ., ]. Dust devil winds carry the small, negatively charged particles high into the air, while the heavier positively charged particles remain near the base of the dust devil.…”

The role of turbulence in thunderstorm, snowstorm, and dust storm electrification

“…The calculation results correspond in general to the experimental data for thunderstorms [ Marshall et al , ; Bateman et al , ; Stolzenburg et al , ; Harrison et al , ], snowstorms [ Latham and Stow , ; Wishart , ; Shio , ; Schmidt and Dent , ], and dust storms [ Gorchakov et al , ; Farrell et al , ; Harrison et al , ; Gorchakov et al , ], showing the intensification of charging processes at high speeds facilitating turbulence development. However, to understand better the role of turbulence in electrification processes in the atmosphere, further observations of electric field variations are needed.…”

Field Measurements of Terrestrial and Martian Dust Devils

“…A more detailed study of the results will show if the instrument is able to detect single particle collisions with the electrode, thus giving access to the particle electric charge during such events. A more detailed overview of the Micro-ARES and the results gathered during the 2014 West Sahara Campaign is presented in Harrison et al (2016) in this issue.…”