Stochastic acceleration of large M/Q ions by hydrogen cyclotron waves in the magnetosphere

It is shown that in hydrogen dominated multi-ion plasmas supporting coherent hydrogen cyclotron waves, the minority ion species with large M/Q are preferentially accelerated and the maximum energy achieved scales as (M/M/sub H/+)/sup 5/3/. The importance of this scaling to O+ acceleration in the auroral zones and to other high energy heavy ion observations in the earth's and Jupiter's mangetospheres is discussed