The Generation of Lightning in the Solar Nebula

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

“…[4] Dust particles are electrified in a dust devil when they collide with each other as a result of differences in sizes and contact potentials between compositionally distinct materials [Melnik and Parrot, 1998;Desch and Cuzzi, 2000]. When two particles of similar composition collide, the smaller grain tends to be negatively charged, and the larger grain obtains an equal but opposite charge.…”

“…[5] Desch and Cuzzi [2000] proposed that when two particles with different contact potentials collide, electrons are transferred to the material with a larger contact potential and leave the material with a smaller contact potential positively charged. Upon collision, a significant amount of charge is placed on each particle.…”

“…Most recently, Jackson and Farrell (submitted manuscript, 2005) measured near 120 kV/m QE fields of dust devils with a carefully calibrated electrometer. A selfregulating mechanism as suggested by Crozier [1964], or a saturation mechanism such as the instantaneous charge dissipation and electric field relaxation due to atmosphere electric conductivity should be introduced properly into the analytical or numerical models [Desch and Cuzzi, 2000].…”

“…[6] The saturation of electric field growth depends on numerous factors, such as the atmosphere conductivity, dust grain charge capacity [Desch and Cuzzi, 2000], recombination of grain charges through subsequent collisions [Melnik and Parrot, 1998], possible neutralizing effect of free charge produced by ionizations of gas molecules [Desch and Cuzzi, 2000], and retardation of grain charging similar to the electrification produced by the collision of ice crystals with polarized hail pellets [Mason, 1988]. Therefore the local atmospheric conductivity controlling charge leakage rate is dynamically coupled with the tribo-charging rate.…”

“…To include all the microphysics of dust devil tribocharging into a simplified model is beyond the scope of our present paper. The primary factor limiting the electric field growth, however, is conduction electric current [Mason, 1972] such that space charge in the region decays exponentially over the relaxation time [Desch and Cuzzi, 2000]. To this end, we assume a constant local atmospheric electric conductivity and focus in this paper on the effect of atmosphere conductivity and how it saturates the tribocharging process.…”