Whistler waves and electron‐whistler scattering in astrophysical plasmas

In shocked astrophysical plasmas, whislter waves can act as scattering centers for electrons in the turbulent fluid, resonantly interacting with electrons of much lower speeds than Alfvén waves scatter with. They therefore show great potential to energize electrons from shocked thermal gas and thereby effect electron injection in the usual diffusive shock acceleration process. In this context, whistlers as a source of electron scattering have received only limited attention in the literature, so here a study of the basic properties of whistler waves in warm plasmas and electron‐whistler scattering is presented. Including the effects of finite plasma temperature T is a significant advance on previous research. The whistler dispersion relation is found in the limit of small wave damping, and it is observed that the range of whistler frequencies depends strongly on T: for high temperatures, whistlers can have low frequencies and phase velocities below the Alfvén speed. The spatial diffusion coefficient for electron‐whistler scattering from quasi‐linear theory is also presented.