Dissipation range dynamics: Kinetic Alfvén waves and the importance of ße

R. J. Leamon, C. W. Smith, N. F. Ness, and H. K. Wong

Bartol Research Institute, University of Delaware, Newark, DE


In a previous paper we argued that the damping of obliquely propagating Kinetic Alfvén waves, chiefly by resonant mechanisms, was a likely explanation for the formation of the dissipation range for interplanetary magnetic field fluctuations. This suggestion was based largely upon observations of the dissipation range at 1 AU as recorded by the Wind spacecraft. We pursue this suggestion here with both a general examination of the damping of obliquely propagating Kinetic Alfvén waves and an additional examination of the observations. We explore the damping rates of Kinetic Alfvén waves under a wide range of interplanetary conditions using numerical solutions of the linearized Maxwell-Vlasov equations and demonstrate that these waves display the nearly isotropic dissipation properties inferred from the previous paper. Using these solutions, we present a simple model to predict the onset of the dissipation range and compare these predictions to the observations. In the process we demonstrated that electron Landau damping plays a significant role in the damping of IMF fluctuations which leads to significant heating of the thermal electrons.

Submitted to J. Geophys. Res., 1999