Weakening of magnetohydrodynamic interchange instabilities by Alfvén waves

Alfvén waves, made to propagate along an ambient magnetic field and polarized transverse to a gravitational field $g$⁠, with wave amplitude stratified along $g$⁠, are shown to reduce the growth rate of interchange instability by increasing the effective inertia by a factor of $1+(B¯y′∕B¯zkz)2$⁠, where $B¯z$ is the ambient magnetic field, $kz$ is the wavenumber, and $B¯y′$ is the wave amplitude shear. Appropriately placed Alfvén wave power could thus be used to enhance the stability of interchange and ballooning modes in tokamaks and other interchange-limited magnetically confined plasmas.