Implications of nonzero photon mass on plasma equilibria

The Beltrami state in a single-species (electron or ion) ideal plasma in the context of massive electromagnetism has been explored. The inclusion of photon mass, essentially treating the massive photon field as a mobile fluid in the ideal plasma vortical dynamics, has resulted in a triple curl Beltrami state of the magnetic vector potential $\vec{A}$. A variational principle is constructed which shows this state can also be obtained by constrained minimization of the system's energy with appropriate helicity invariants. Such a state is endowed with three different length scales; one of which is the system length, and the other two are species' skin depth and photon Compton wavelength, respectively. An analytical solution of this state in the cylindrical geometry is presented, which is the linear combination of three single Beltrami states. Possible observational signatures of this state in astrophysical and laboratory settings are also discussed.