A plasma consists of electrons and protons with equal number densities, n, with a uniform magnetic field along the x-axis with z the vertical direction.
(a) Calculate the current density, J, due to the gravitational drift of electrons and protons, where the gravitational acceleration, g, is along the negative z-axis.
(b) Calculate the force per unit volume, J × B, due to this current density.
(c) Give a physical interpretation of your answer.