Description
Plasmas in various space objects (e.g. the solar lower atmosphere) are not hot enough to ensure a full ionisation, therefore ions, electrons and neutral particles coexist and interact with each other via collisions. Alfvén waves are transversal perturbations in the magnetic field that propagate along field lines and are able to carry large amounts of energy, therefore contributing to the heating and acceleration of the plasma.
We consider a two-fluid (charges-neutrals) solar plasma in the frequency regime of particle collisions and investigate the nature and properties of Alfven waves that can propagate in a steady state plasma, when ions and neutrals are allowed to have different speeds. Our results show that in this case entropy modes become propagating, so flows are able to generate new wave modes. The presence of flows and collisions between particles alter the properties of waves and induce interesting phenomena such as mode conversion and two-steam flow instabilities. The behaviour of waves is strongly regulated by the collisional frequency between particles, especially when this quantity becomes of the same order as the natural frequency of waves.
