Ion cyclotron resonant instability of RH waves propagating at an angle to the interplanetary magnetic field

The anomalous Doppler-shift interaction between positive ions and right-hand (RH) polarized E.M. waves propagating at a small angle to a static magnetic field is investigated. The linear rate of growth of the resulting instability is obtained and compared with the growth rate for the parallel propagation case. For conditions typical of the solar wind at about 1 AU, the rate of growth always decreases with increasing propagation angle. For very large ion pressures (β_{{norm of matrix}}≫1) and temperature anisotropies (T_{{norm of matrix}}T_⊥≫1), the rate of growth may increase with increasing propagation angle.