The presence of micron and sub-micron size dust in the Earth's summer mesopause are a possible cause of electron density depletion. Whereas electrons in this weakly ionized and weakly magnetized layer are frozen in the magnetic field, the ions and dust are highly diffusive. This relative drift between the plasma particles will cause a current in the medium. The presence of such a current can destabilize the plasma layer with a growth rate of the order of Alfvén frequency. Since required current density for the onset of this instability is on the order of J 0.03 A / m 2, it is quite unlikely that such a strong current is present in the mesosphere. However, owing to the prevailing ambiguity of measurements, the existence of such a current is not completely ruled out.