Kinetic Alfvén waves: Linear theory and a particle‐in‐cell simulation

Abstract

An Alfvén‐cyclotron fluctuation of sufficiently short wavelength has a strong proton cyclotron resonance at propagation parallel to the background magnetic field Bo in a homogeneous, collisionless electron‐proton plasma. As k∥, the wavevector component parallel to Bo, decreases, the proton cyclotron wave‐particle interaction becomes nonresonant, and the electron Landau resonance becomes effective at propagation oblique to Bo. Here linear Vlasov theory is used to determine the dispersion and damping properties of Alfvén‐cyclotron fluctuations associated with the transition from the proton cyclotron resonance regime to the electron Landau resonance regime. Also, a particle‐in‐cell plasma simulation is used to examine the electron response to the initial imposition of an Alfvén‐cyclotron wave in the electron Landau resonance regime. The computation shows heating of the electrons in the direction parallel to Bo and the formation of a beam in the direction of the parallel component of k.