Counter-rotating density and current structures in a partially magnetized $\mathbf{E}\times \mathbf{B}$ plasma

Abstract

The first 3D kinetic simulation of a magnetron discharge reproduces the measured rotating spoke and reveals that density and current rotate in opposite directions: the $m=1$ spoke turns in the $\mathbf{E}\times \mathbf{B}$ direction at 90~kHz while $m\simeq 16$ electron-cyclotron-drift-type filaments turn at 1.0~MHz, with no net propagation along $\mathbf{B}$. Magnetic drifts exchange far more energy than they deposit, yet their spoke-front heating sustains the ionization. Following helical paths, the anode-directed current is relayed by de-trapping turbulence at the sheath edge (50\%) and by the spoke channel in the bulk (97\%).