3D numerical simulations of propagating two-fluid, torsional Alfvén waves and heating of a partially ionized solar chromosphere

We present a new insight into the propagation, attenuation, and dissipation of two-fluid, torsional Alfvén waves in the context of heating of the lower solar atmosphere. By means of numerical simulations of the partially ionized plasma, we solve the set of two-fluid equations for ion plus electron and neutral fluids in 3D Cartesian geometry. We implement initially a current-free magnetic field configuration, corresponding to a magnetic flux-tube that is rooted in the solar photosphere and expands into the chromosphere and corona. We put the lower boundary of our simulation region in the low chromosphere, where ions and neutrals begin to decouple, and implement there a monochromatic driver that directly generates Alfvén waves with a wave period of 30 s. As the ion-neutral drift increases with height, the two-fluid effects become more significant and the energy carried by both Alfvén and magneto-acoustic waves can be thermalized in the process of ion–neutral collisions there. In fact, we observe a significant increase in plasma temperature along the magnetic flux-tube. In conclusion, the two-fluid torsional Alfvén waves can potentially play a role in the heating of the solar chromosphere.