Theory for Resonant Ion Acceleration by Nonlinear Magnetosonic Fast and Slow Waves in Finite beta Plasmas

摘要

A Korteweg de-Vries equation that is applicable to both the nonlinear magnetosonic fast and slow waves is derived from a two-fluid model with finite ion and electron pressures. As in the cold plasma theory, the fast wave has a critical angle theta(c). For propagation angles greater than theta(c) (quasi-perpendicular propagation), the fast wave has a positive soliton, whereas for angles smaller than theta(c), it has a negative soliton. Finite Beta effects decrease the value of theta(c). The slow wave has a positive soliton for all angles of propagation. The magnitude of resonant ion acceleration (the upsilon (p) x B acceleration) by the nonlinear fast and slow waves is evaluated. In the fast wave, the electron pressure makes the acceleration stronger for all propagation angles. The decrease in theta(c) due to finite Beta effects results in broadening of the region of extremely strong acceleration. It is also found that strong ion acceleration can occur in the nonlinear slow wave in high Beta plasmas. Possibility of unlimited acceleration of ions by quasi-perpendicular magnetosonic fast waves is discussed.