Heating and deceleration of minor ions in the extended fast solar wind by oblique Alfvén waves

Abstract

Using one‐dimensional hybrid simulations, the interaction between oblique propagating Alfvén waves and minor ions in the fast solar wind stream is investigated in this paper. In typical fast solar wind conditions, these waves and the drifting minor ions satisfy the ion cyclotron resonance condition: ω = −Ωi + k∥v∥. (Here ω is the wave angular frequency, Ωi is the gyration frequency of an ion species i, k∥ is the wave number component along the background magnetic field B0, and v∥ is the particle velocity component of the ion species parallel to B0.) These waves are able to heat minor ions while decelerating them at the same time. The heating is primarily in the direction perpendicular to the background magnetic field, and the deceleration helps to restrict minor ion and proton beam‐drifting speed at or just lower than the local Alfvén speed (in relative to the speed of the core proton component).