Incorporating Kinetic Physics into a Two-Fluid Solar-Wind Model with Temperature Anisotropy and Low-Frequency Alfven-Wave Turbulence

TL;DR

This paper presents a comprehensive 1D solar-wind model incorporating kinetic physics, temperature anisotropy, and Alfven-wave turbulence, providing insights into solar wind acceleration and heating mechanisms.

Contribution

It introduces a novel solar-wind model that combines kinetic physics, turbulence, and temperature anisotropy to better understand solar wind dynamics.

Findings

Model solutions align with observed solar wind properties.

Alfven-wave turbulence significantly contributes to solar wind heating.

Proton temperature anisotropy influences instability thresholds and scattering rates.

Abstract

We develop a 1D solar-wind model that includes separate energy equations for the electrons and protons, proton temperature anisotropy, collisional and collisionless heat flux, and an analytical treatment of low-frequency, reflection-driven, Alfven-wave turbulence. To partition the turbulent heating between electron heating, parallel proton heating, and perpendicular proton heating, we employ results from the theories of linear wave damping and nonlinear stochastic heating. We account for mirror and oblique firehose instabilities by increasing the proton pitch-angle scattering rate when the proton temperature anisotropy exceeds the threshold for either instability. We numerically integrate the equations of the model forward in time until a steady state is reached, focusing on two fast-solar-wind-like solutions. These solutions are consistent with a number of observations, supporting the idea that Alfven-wave turbulence plays an important role in the origin of the solar wind.