Nonlinear Dissipation of Alfvén Waves

Boynton, G. Chris; Torkelsson, Ulf

doi:10.1007/978-94-009-0315-9_99

Cited by 12 publications

(34 citation statements)

References 2 publications

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“…The coronal plasma is modeled using the MHD equations (Priest 1982;Boynton & Torkelsson 1996), which are written in conservation form, as required by the numerical algorithm selected to advance them. As in the work of Boynton & Torkelsson (1996), we use the flux-corrected transport (FCT) algorithm (Boris & Book 1973) to perform the numerical simulations because of its proven resilience, stability, and positivity in handling functions with steep gradients, including shocks.…”

Section: Mhd Equationsmentioning

confidence: 99%

“…As in the work of Boynton & Torkelsson (1996), we use the flux-corrected transport (FCT) algorithm (Boris & Book 1973) to perform the numerical simulations because of its proven resilience, stability, and positivity in handling functions with steep gradients, including shocks. FCT is designed to treat shocks correctly; this is why the fluid equations must be in conservation form.…”

Section: Mhd Equationsmentioning

confidence: 99%

“…The conversion of MHD waves into shocks has already been proposed as a contributing heating mechanism for the solar corona by Boynton & Torkelsson (1996), using an isothermal, one-dimensional, numerical model. Periodic MHD waves are generated by moving the footpoint of a magnetic field line at the bottom of the computational region, which represents a layer in the low solar corona.…”

Section: Introductionmentioning

confidence: 99%

“…A comparison with the results of Boynton & Torkelsson (1996) motivates our choice of simulation runs. They considered both stratified and unstratified media, but we redo their unstratified, periodic wave runs only (x 3.2), to avoid certain unessential complications that would lengthen the presentation unduly.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Magnetohydrodynamic Shock Heating of the Solar Corona

Orta

Huerta

Boynton

2003

ApJ

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Coronal MHD waves excited by perturbations of magnetic field lines propagate upward, carrying with them the energy from the excitation. Under favorable conditions shocks form, and part of the wave energy is converted to plasma heating and motion. We use numerical simulations to accurately follow the shock formation and subsequent energy release. The model includes an adiabatic energy equation for the explicit evaluation of temperature increases and energy fluxes contributed by the shocks. Transverse, plane-polarized excitations are considered; they can be periodic, as in Alfvén wave trains, or pulsed, as might result from nanoflares. The model is tested with a set of validation runs that produce good agreement with theoretical predictions. Our results show that nonlinear waves moving along large magnetic fields with low plasma , with field amplitudes comparable to the background field, develop shocks that form important amounts of plasma heating and that mass outflow may occur. Fast and slow magnetoacoustic shocks are generated, each one making its own contribution. Most of the heating takes place in the low corona, but long-range distributed heating still occurs up to heights of several solar radii. The energy fluxes for the stronger cases are sufficient to compensate for thermal and convective losses, consistent with observations. We conclude that large-amplitude MHD shocks in low-regions could be a viable mechanism for coronal heating and wind acceleration in regions of open magnetic field lines.

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Section: Mhd Equationsmentioning

confidence: 99%

Section: Mhd Equationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Magnetohydrodynamic Shock Heating of the Solar Corona

Orta

Huerta

Boynton

2003

ApJ

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“…A number of attempts have been carried out to investigate nonlinear Alfvén waves in stratified solar winds in 1-D (Lau and Siregar, 1996;Boynton and Torkelsson, 1996) and 2-D Davila, 1997, 1998;Grappin et al, 2002), and by multi-fluid treatments (Ofman, 2004). These studies nicely explain observations by suitable choices of perturbation amplitude at the inner boundary in the corona.…”

Section: Introductionmentioning

confidence: 99%

Coronal heating and wind acceleration by nonlinear Alfvén waves – global simulations with gravity, radiation, and conduction

Suzuki

2008

Nonlin. Processes Geophys.

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Abstract. We review our recent results of global onedimensional (1-D) MHD simulations for the acceleration of solar and stellar winds. We impose transverse photospheric motions corresponding to the granulations, which generate outgoing Alfvén waves. We treat the propagation and dissipation of the Alfvén waves and consequent heating from the photosphere by dynamical simulations in a self-consistent manner. Nonlinear dissipation of Alfven waves becomes quite effective owing to the stratification of the atmosphere (the outward decrease of the density). We show that the coronal heating and the solar wind acceleration in the open magnetic field regions are natural consequence of the footpoint fluctuations of the magnetic fields at the surface (photosphere). We find that the properties of the solar wind sensitively depend on the fluctuation amplitudes at the solar surface because of the nonlinearity of the Alfvén waves, and that the wind speed at 1 AU is mainly controlled by the field strength and geometry of flux tubes. Based on these results, we point out that both fast and slow solar winds can be explained by the dissipation of nonlinear Alfvén waves in a unified manner. We also discuss winds from red giant stars driven by Alfvén waves, focusing on different aspects from the solar wind.

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Atmospheric Heating and Wind Acceleration in Cool Evolved Stars

Airapetian

Cuntz

2014

Giants of Eclipse: The Ζ Aurigae Stars and Other Binary Systems

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A chromosphere is a universal attribute of stars of spectral type later than ∼F5. Evolved (K and M) giants and supergiants (including the ζ Aur binaries) show extended and highly turbulent chromospheres, which develop into slow massive winds. The associated continuous mass loss has a significant impact on stellar evolution, and thence on the chemical evolution of galaxies. Yet despite the fundamental importance of those winds in astrophysics, the question of their origin(s) remains unsolved. What sources heat a chromosphere? What is the role of the chromosphere in the formation of stellar winds? This article provides a review of the observational requirements and theoretical approaches for modelling chromospheric heating and the acceleration of winds in single cool, evolved stars and in eclipsing binary stars, including physical models that have recently been proposed. It describes the successes that have been achieved so far by invoking acoustic and MHD waves to provide a physical description of plasma heating and wind acceleration, and discusses the challenges that still remain.

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Nonlinear Dissipation of Alfvén Waves

Cited by 12 publications

References 2 publications

Magnetohydrodynamic Shock Heating of the Solar Corona

Magnetohydrodynamic Shock Heating of the Solar Corona

Coronal heating and wind acceleration by nonlinear Alfvén waves – global simulations with gravity, radiation, and conduction

Atmospheric Heating and Wind Acceleration in Cool Evolved Stars

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