On perpendicularly propagating electromagnetic lower hybrid waves and ion Bernstein waves in a multi-component plasma

We systematically analyze waves in the lower hybrid range of frequencies propagating perpendicularly to the magnetic field in a multi-component plasma. We derive a dispersion relation for lower hybrid waves, valid for multiple ion species, in addition to an approximate explicit expression that performs well in a broad parameter range. It is demonstrated under which conditions electrostatic dispersion relations for ion Bernstein waves and lower hybrid waves are applicable and when the electrostatic approximation should be avoided. We show how the electromagnetic response is straightforward to include in electrostatic dispersion relations with high accuracy by adding a cold electromagnetic term. Important features of electromagnetic ion Bernstein waves and electromagnetic lower hybrid waves are discussed, both in a single-ion plasma and in a multi-component plasma. For completeness, all relevant lower hybrid wave and ion Bernstein wave dispersion relations are benchmarked against kinetic particle-in-cell simulations covering a range of plasma parameters. Finally, we discuss the propagation of LH waves in an inhomogeneous plasma and consider the problem of mode conversion between the LH wave and ion Bernstein waves.