Speaker
Dr
Yana Maneva
(CmPA at KU Leuven)
Description
We perform 2.5D hybrid simulations to study the turbulent heating and acceleration of protons and minor ions in collisionless homogeneous fast solar wind. The focus of this work is wave-particle interactions at the intermediate ion scales, therefore the small-scale electrons are considered as charge-neutralizing isothermal fluid and the electron intertia in our approach is neglected. The dissipation of magnetic field fluctuations in collisionless plasmas can occur via fluid cascade at large-scales, followed by various intermediate (ion) and small-scale eloectron kinetic wave-particle interactions. The efficiency of the ion heating depends on the characteristics of the waves carrying energy at the ion scales, such as polarization, direction of propagation and spectral properties of the fluctuations. Realistic solar wind turbulence includes different types of waves at all scales, starting with fluid regime and going down to the electron scales. Although the spatial and temporal scales of these fluctuaction are separated by few orders of magnitudes, they can still exchange energy as large and small-scales turbulent cascades oparate. As a simplistic attempt to model part of the solar wind turbulence at the ion scales we assume a superposition of left-hand circularly-polarized Alfven ion-cyclotron waves. These waves are frequently observed in situ in the solar wind, and yet their specific role for the energetization of minor ions remains unclear. In this study we perform 2.5D hybrid simulations to test the importance of parallel and obliquely propagating Alfven-cyclotron waves for the anisotropic heating of minor ions in the solar wind. We start with initially isotropic plasma with equal temperatures for the protons and alpha particles and impose an initial turbulent spectrum of Alfven-cyclotron waves to subsequently follow the preferential heating for the minor ions and the onset of temperature anisotropies for both ion species. We compare the efficiency of the parallel and oblique waves in heating the protons and the minor ions. In the course of the nonlinear evolution of the system when an initial parallel wave spectrum is assumed we observe a substaintial anisotropic cascade of the magnetic field power spectrum towards perpendicular wave numbers.
Primary author
Dr
Yana Maneva
(CmPA at KU Leuven)
Co-author
Prof.
Stefaan Poedts
(KU Leuven)
