Second-order perturbations in Alfvén waves in finite pressure plasma

It is shown first that in finite pressure plasma, just as in cold plasma, Alfvén waves created by an initial perturbation generate plasma flows and decreases in the magnetic field, which propagate along with these waves. Second, at the stage of their interaction, Alfvén waves generate slow magnetosonic (SMS) waves propagating along the magnetic field. These results suggest that at least some of the fast plasma flows observed in the magnetotail can be one of the manifestations of propagating Alfvén waves both in the magnetosphere regions with cold plasma and in the magnetosphere regions with finite pressure plasma. They also provide potential possibility for determining the position of a source of Alfvén disturbance from observations of Alfvén waves and their induced SMS waves.