By treating the heavily-damped ion Bernstein wave as a driven response to the fast Alfven wave

we have derived a second-order mode-conversion equation describing the wave-plasma interaction in ion cyclotron resonance heating in three-ion species plasma.The structure of fast wave electron field E

y

is derived from this numerically analytical solution of this equation and the mode-conversion on the domain of resonance

and reflection is also obtained.The results are in good agreement with those obtained from higher order equations.The hot alpha particle power absorption is important only when the damping is weak.