Three-Dimensional Double Layers Inducing Ion-Cyclotron Oscillations in a Collisionless Plasma

Three-dimensional double layers are generated in a strongly magnetized collisionless plasma column. The position and shape of the double layers are controlled by the formation of mirror configuration of magnetic field, which simulate the magnetic field structure above the Earth's auroral oval. The double layers are found to induce electrostatic oscillations with frequencies above the ion-cyclotron frequency and its harmonics, in contrast to one-dimensional double layers. The oscillations are driven by the large inhomogeneous radial electric field and propagate azimuthally with mode number m=1,2,3,.