Coronal Heating Distribution Due to Low‐Frequency, Wave‐driven Turbulence

Abstract

The heating of the lower solar corona is examined using numerical simulations and theoretical models of magnetohydrodynamic turbulence in open magnetic regions. A turbulent energy cascade to small length scales perpendicular to the mean magnetic field can be sustained by driving with low-frequency Alfvén waves reflected from mean density and magnetic field gradients. This mechanism deposits energy efficiently in the lower corona, and we show that the spatial distribution of the heating is determined by the mean density through the Alfvén speed profile. This provides a robust heating mechanism which can explain observed high coronal temperatures and accounts for the significant heating (per unit volume) distribution below 2 solar radii needed in models of the origin of the solar wind. The obtained heating per unit mass, on the other hand, is much more extended, indicating that the heating on a per-particle basis persists throughout all the lower coronal region considered here.

Turbulence In The Solar Atmosphere: Manifestations And Diagnostics Via Solar Image Processing

“…In essence, a turbulent evolution requires (1) a few large-scale, coherent, currentcarrying magnetic structures, (2) ideal (non-dissipative) fragmentation of the free magnetic energy within an inertial range of length scales, and (3) a critical length scale below which magnetic resistivity sets in and releases part of the fragmented free energy. All of the above requirements are satisfied in modeled active regions and are supported by observations of actual solar active regions: the vector potential and the photospheric flows are organized in a few large-scale structures, while the electric current density and hence the magnetic free energy are distributed within numerous small-scale structures with linear sizes extending down to our present observational limit (e.g., Einaudi et al, 1996;Georgoulis, Velli, and Einaudi 1998;Chae 2001;Dmitruk et al, 2002). The first and the second process are known as an inverse and a direct cascade, respectively.…”

Solar Wind Electrons Alphas and Protons (SWEAP) Investigation: Design of the Solar Wind and Coronal Plasma Instrument Suite for Solar Probe Plus

“…(2) Understand Which Heating Mechanisms Dominate as a Function of Distance from the Sun Numerous models to describe the heating and acceleration mechanisms of the Hollweg (2008), Cranmer (2000), Hollweg and Isenberg (2002), Isenberg (2001a), Galinsky and Shevchenko (2000), Marsch and Tu (2001), Kasper et al (2008 b Matthaeus et al (1999), Dmitruk et al (2002), Cranmer et al (2007), Chandran et al (2009) c Bruner (1978), Ulmschneider (1985) d Parker (1979Parker ( , 1987, Sturrock (1999), Priest et al (2002), Axford and McKenzie (1992), Cargill and Klimchuk (2004), Schrijver et al (1997), Zurbuchen et al (2002) e Scudder (1994), Pierrard and Lamy (2003) solar corona and wind have been advanced with varying degrees of success, but none is universally accepted and possibly many are valid in some subset of plasma conditions. With the correct measurements SPP can determine the relative contribution of these mechanisms in the solar wind and understand which are most important.…”

Discrete modes and turbulence in a wave‐driven strongly magnetized plasma

“…[5] We employ a Reduced MHD model of wave-driven turbulence that we have previously applied to study coronal heating in an open magnetic region [Dmitruk et al, 2002;Dmitruk and Matthaeus, 2003]. The description is not a full 3D model, but represents anisotropic transverse fluctuating velocity and magnetic fields v, b, having weaker spatial variation in the s direction than in the perpendicular directions, r s ( r ?…”