Gradient-drift instability in space dusty plasmas

Possible effects of negatively charged dust on the gradient-drift instability in the lower ionosphere are investigated. The presence of localized regions of charged dust with short-scale variations in the dust charge density may lead to the generation of small-scale electron density gradients which can enhance the growth of the instability. In addition, negatively charged dust can influence the instability through its effect on equilibrium charge neutrality, which affects the phase speed of the waves. Using linear kinetic theory, critical electron drifts are estimated. It is found that, if there are perpendicular (to the ambient magnetic field direction) electron density gradients with scale size ∼ several tens of meters in the daytime ionosphere at altitudes ∼90 km, owing to the presence of vertical variations of the dust charge density, waves with wavelengths ∼ a few meters may be driven unstable by electron drifts on the order of the ion thermal speed. Possible applications to dusty plasmas in the low E-region, such as polar mesosphere summer echo regions, are discussed.