Turbulence in the sub-Alfv\'enic solar wind driven by reflection of low-frequency Alfv\'en waves

TL;DR

This study models how reflection-driven Alfvén wave turbulence influences solar wind heating and acceleration, revealing spectral evolution and the significance of reflection in shaping turbulence and energy dissipation in the heliosphere.

Contribution

It demonstrates the role of wave reflection in shaping turbulence spectra and heating in the solar wind using 2D shell models from the corona to 17 solar radii.

Findings

Turbulent spectra evolve toward a Kolmogorov spectrum at larger distances.

Reflection influences the spectral shape near the solar surface.

Turbulent dissipation accounts for at least half of the solar wind heating.

Abstract

We study the formation and evolution of a turbulent spectrum of Alfv\'en waves driven by reflection off the solar wind density gradients, starting from the coronal base up to 17 solar radii, well beyond the Alfv\'enic critical point. The background solar wind is assigned and 2D shell models are used to describe nonlinear interactions. We find that the turbulent spectra are influenced by the nature of reflected waves. Close to the base, these give rise to a flatter and steeper spectrum for the outgoing and reflected waves respectively. At higher heliocentric distance both spectra evolve toward an asymptotic Kolmogorov spectrum. The turbulent dissipation is found to account for at least half of the heating required to sustain the background imposed solar wind and its shape is found to be determined by the reflection-determined turbulent heating below 1.5 solar radii. Therefore reflection and reflection-driven turbulence are shown to play a key role in the accelerationof the fast solar wind and origin of the turbulent spectrum found at 0.3 AU in the heliosphere.