Impact of transverse magnetic field on electromagnetic electron Kelvin–Helmholtz instability and a new electron Rayleigh–Taylor instability

The effects of transverse magnetic field on the electromagnetic (EM) electron Kelvin–Helmholtz instability (EKHI) in incompressible, inviscid, and collisionless plasma are investigated, assuming step-function electron velocity U0 and density n0 profiles, with a uniform magnetic field that has three components: parallel component that aligns with U0, and two transverse components. It is found that (1) the in-plane (defined as in the plane of the electron streamings and its gradient) transverse magnetic field and its associated out-of-plane electric field have no effects on the EM EKHI. Other components of the magnetic field suppress the growth of EKHI; (2) the in-plane electric field produced by the out-of-plane magnetic guide field can trigger an electron Rayleigh–Taylor instability (ERTI) perpendicular to the electron streaming. However, the tension of the magnetic guide field suppresses the growth of ERTI, causing it to only grow in long wavelengths; (3) when the ERTI criterion is met, the associated electric field can enhance EM EKHI in non-perpendicular direction; and (4) when the system is stable to ERTI, the magnetic guide field generates an electron super-Alfvénic wave and becomes electron Alfvén wave when the density gradient vanishes.