A method of producing a charge separation in a low density plasma which comprises a plurality of electrons and a plurality of positive ions. The method includes generating a magnetic field and passing the low density plasma along a first axis through the magnetic field. The magnetic field is generated having a component which is perpendicular to the first axis and is configured so as to deflect the plurality of electrons from the first axis and allow the plurality of positive ions to travel substantially undeflected along the first axis. Also provided is a magnetohydrodynamic generator and a low earth orbit thruster making use of the charge separation mechanism.