PITCH ANGLE SCATTERING OF COMETARY IONS INTO MONOSPHERICAL AND BISPHERICAL DISTRIBUTIONS

Low frequency magnetic fluctuations generated by solar wind/cometary ion distributions cause pitch-angle scattering of cometary ions. The nature of this pitch angle scattering is examined by means of one-dimensional hybrid simulations, in which newborn ions are created at a constant rate, and for various injection angles, alpha, relative to the magnetic field. Pitch angle scattering in the quasi-perpendicular regime (alpha > 60-degrees) results in a bispherical velocity distribution while in the quasi-parallel regime (0 less-than-or-equal-to alpha less-than-or-equal-to 60-degrees), pitch angle scattering can result in either a mono or bispherical distribution depending on the injection angle and initial beam velocity.