A method for establishing a region of a high density, high energy plasma at an altitude of at least about 1500 kilometers above the earth’s surface. Circularly polarized electromagnetic radiation is transmitted at a first frequency substantially parallel to an earth’s magnetic field line to excite electron cyclotron resonance heating in normally occurring plasma at an altitude of at least about 250 kilometers to generate a mirror force which lifts said plasma to said altitude of at least about 1500 kilometers. Heating is continued at a second frequency to expand the plasma to the apex of said field line whereupon at least some of the plasma is trapped and oscillates between mirror points on said lines. The plasma will be contained within adjacent field lines and will drift to form a shell of relativistic particles around a portion of the earth.