Coupling of Alfvén and magnetosonic waves in rotating Hall magnetoplasmas

Abstract: We study the linear theory of magnetohydrodynamic (MHD) waves, namely the Alfv{\'e}n and the fast and slow magnetosonic modes in a rotating Hall-MHD plasma with the effects of the obliqueness of the external magnetic field and the Coriolis force and show that these waves can be coupled either by the influence of the Coriolis force or the Hall effects. To this end, we derive a general form of the linear dispersion relation for these coupled modes by the combined influence of the Coriolis force and the Hall effects and analyze numerically their characteristics in three different plasma-$\beta$ regimes: $\beta\sim1$, $\beta>1$, and $\beta<1$, including some particular cases. We show that while the coupling between the Alfv{\'e}n and the fast magnetosonic modes is strong in the low-$\beta$ $(\beta\lesssim1)$ regime and the wave dispersion appears in the form of a thumb curve, in the high-$\beta~(\beta>1)$ regime, the strong coupling can occur between the Alfv{\'e}n and the slow magnetosonic modes and the dispersion appears in the form of a teardrop curve. Switching of the coupling in the regime of $\beta\sim1$ can occur, i.e., instead of a thumb curve, a teardrop curve appears when the obliqueness of propagation and rotational angle are close to $70^\circ$ or more (but less than $90^\circ$). Implications of our results to solar and fusion plasmas are briefly discussed.