Theory and Transport of Nearly Incompressible Magnetohydrodynamic Turbulence. IV. Solar Coronal Turbulence

Abstract

A new model describing the transport and evolution of turbulence in the quiet solar corona is presented. In the low plasma beta environment, transverse photospheric convective fluid motions drive predominantly quasi-2D (nonpropagating) turbulence in the mixed-polarity “magnetic carpet,” together with a minority slab (Alfvénic) component. We use a simplified sub-Alfvénic flow velocity profile to solve transport equations describing the evolution and dissipation of turbulence from (including the Alfvén surface). Typical coronal base parameters are used, although one model uses correlation lengths derived observationally by Abramenko et al., and the other assumes values 10 times larger. The model predicts that (1) the majority quasi-2D turbulence evolves from a balanced state at the coronal base to an imbalanced state, with outward fluctuations dominating, at and beyond the Alfvén surface, i.e., inward turbulent fluctuations are dissipated preferentially; (2) the initially imbalanced slab component remains imbalanced throughout the solar corona, being dominated by outwardly propagating Alfvén waves, and wave reflection is weak; (3) quasi-2D turbulence becomes increasingly magnetized, and beyond , the kinetic energy is mainly in slab fluctuations; (4) there is no accumulation of inward energy at the Alfvén surface; (5) inertial range quasi-2D rather than slab fluctuations are preferentially dissipated within ; and (6) turbulent dissipation of quasi-2D fluctuations is sufficient to heat the corona to temperatures K within , consistent with observations that suggest that the fast solar wind is accelerated most efficiently between .

Energy Transport and Heating by Torsional Alfvén Waves Propagating from the Photosphere to the Corona in the Quiet Sun

“…We do not incorporate information about the coronal structure at larger heights, and so we ignore the possible reflections that may occur there. In the context of plasma heating by turbulence, Alfvn wave reflection in the corona has been studied by, e.g., Matthaeus et al (1999); Cranmer & van Ballegooijen (2005); Zank et al (2018). In relation with the purpose of this paper, i.e., to study wave energy propagation from the photosphere to the corona through the chromosphere, the results show that the reflection of waves driven at the photosphere is important in the high chromosphere and transition region but, in our calculations, reflection does not play a relevant role above the transition region since only about 1% of the driven energy flux is able to reach those heights (see again Figure 9(a)).…”

Critical Magnetic Field Strengths for Solar Coronal Plumes in Quiet Regions and Coronal Holes?

“…The other possible mechanism for plume heating could be the heating by waves. The recently proposed mechanism of turbulence build up and dissipation (Zank et al 2018) could be an alternative possibility. In any case (whether heating is from mixed-polarity, waves, or turbulence) magnetoconvection drives the heating in plumes, similar to that seen for active regions (e.g., Tiwari et al 2017).…”

Turbulence Transport Modeling and First Orbit Parker Solar Probe (PSP) Observations

“…Different authors have chosen different values for α. For example, Matthaeus et al (1999a) chose α = 1 in their model of coronal heating by magnetohydrodynamic turbulence (see also Zank et al (2018a)). In our study, we consider α = 0.1.…”