Ion acceleration and coherent structures generated by lower hybrid shear-driven instabilities

Abstract

It is shown that if \ensuremath{\kappa}=${\mathrm{\ensuremath{\omega}}}_{\mathit{S}}$/${\mathrm{\ensuremath{\omega}}}_{\mathrm{LH}}$>1 (${\mathrm{\ensuremath{\omega}}}_{\mathit{S}}$ and ${\mathrm{\ensuremath{\omega}}}_{\mathrm{LH}}$ are the shear and lower hybrid frequencies), a sheared electron cross-field flow excites the electron-ion-hybrid mode, causing significant perpendicular ion acceleration. The electric potential develops coherent structures (vortexlike) longer than the electron Larmor radius, ${\mathrm{\ensuremath{\rho}}}_{\mathit{e}}$. For \ensuremath{\kappa}1, a smooth transition occurs where the wavelength becomes of the order of ${\mathrm{\ensuremath{\rho}}}_{\mathit{e}}$, the lower hybid drift instability dominates, and the formation of vortexlike structures is no longer observed. The results are relevant to laboratory, laser-produced, and space plasmas.