Reversed Hall effect and plasma conductivity in the presence of charged impurities

Abstract

The Hall conductivity of magnetized plasma can be strongly suppressed by the contribution of negatively charged particulates (referred further as “dust”). Once the charge density accumulated by the dust exceeds a certain threshold, the Hall component becomes negative, providing a reversal in the Hall current. Such an effect is unique for dust-loaded plasmas, and it can hardly be achieved in electronegative plasmas. Further growth of the dust density leads to an increase in both the absolute value of the Hall and Pedersen conductivities, while the field-aligned component is decreased. These modifications enhance the role of transverse electric currents and reduce the anisotropy of a magnetized plasma when loaded with charged impurities. The findings provide an important basis for studying the generation of electric currents and transport phenomena in magnetized plasma systems containing small charged particulates. They can be relevant for a wide range of applications from naturally occurring space plasmas in planetary magnetospheres and astrophysical objects to laboratory dusty plasmas (Magnetized Dusty Plasma Experiment) and to technological and fusion plasmas.

Discovery of Double Hall Pattern Associated with Collisionless Magnetic Reconnection in Dusty Plasmas

“…In some dusty plasmas, the depletion of electrons and the increase of negatively charged dusts reverse the Hall effect and render the Hall conductivity negative. The reversed Hall effect was found both analytically (Yaroshenko & Lühr 2018) and numerically (Kriegel et al 2011), and is supported by Cassini observations in Enceladus plasma (Simon et al 2011). It is therefore natural to conjecture that when electron and dust grains both play important roles and scale separations are clear among electron, ion and dust diffusion regions, a complicated double Hall pattern may emerge.…”

“…Negatively charged dust grains by absorbing electrons are typically micron-and submicron-sized. The charges and masses of dust grains can vary in a large range for different scenarios (Yaroshenko & Lühr 2018), where the dust grains serves as immobile background when it is very heavy or moving particles otherwise. The dust component therefore influences the plasma by introducing new modes to waves and instabilities (Merlino et al 1998) as well as modifying the traditional mode properties (Morfill & Ivlev 2009;Ghosh et al 2002;Debnath & Bandyopadhyay 2020).…”

Dust modification of the plasma conductivity in the Earth's mesosphere

“…Since the direction of the Hall electric field in this case will be opposite to the case discussed above where it was the plasma particles that was drifting against the negatively charged dust, the sign of the Hall term in the induction equation ( 16) will become positive. Such a reversal of sign of the Hall term is well known in the dusty plasmas [31] and has recently been investigated in the plume region of the Saturnś moon Enceladus [49].…”