An anisotropic-Alfvenic-turbulence-based solar wind model with proton temperature anisotropy

TL;DR

This paper develops a solar wind model based on anisotropic Alfvenic turbulence and proton temperature anisotropy, addressing heating and acceleration mechanisms for both fast and slow solar wind streams.

Contribution

It extends existing turbulence-based solar wind models by incorporating proton temperature anisotropy effects, field line curvature, and electron radiative losses.

Findings

The model successfully explains proton temperature anisotropy in both fast and slow solar wind.

It demonstrates the applicability of anisotropic turbulence mechanisms to slow solar wind near streamer helmets.

The model aligns with observations of ion heating and wind acceleration in the solar corona.

Abstract

How the solar wind is accelerated to its supersonic speed is intimately related to how it is heated. Mechanisms based on ion-cyclotron resonance have been successful in explaining a large number of observations, those concerning the significant ion temperature anisotropy above coronal holes in particular. However, they suffer from the inconsistency with turbulence theory which says that the turbulent cascade in a low-beta medium like the solar corona should proceed in the perpendicular rather than the parallel direction, meaning that there is little energy in the ion gyro-frequency range for ions to absorb via ion-cyclotron resonance. Recently a mechanism based on the interaction between the solar wind particles and the anisotropic turbulence has been proposed, where the perpendicular proton energy addition is via the stochastic heating (Chandran et al. 2011). We extend this promising mechanism by properly accounting for the effect of proton temperature anisotropy on the propagation of Alfven waves, for the radiative losses of electron energy, and for the field line curvature that naturally accompanies solar winds in the corona. While this mechanism was shown in previous studies to apply to the polar fast solar wind, we demonstrate here for the first time that it applies also to the slow wind flowing along field lines bordering streamer helmets.