Wave-Based Heating Mechanisms for the Solar Corona

1994 ◽  
Vol 144 ◽  
pp. 443-451 ◽  
Author(s):  
F. Malara ◽  
M. Velli
Keyword(s):  
Solar Corona ◽  
Nonlinear Effects ◽  
Resonant Absorption ◽  
Mhd Waves ◽  
Small Scale ◽  
Phase Mixing ◽  
Low Dissipation ◽  
Wave Heating ◽  
Lower Solar Atmosphere ◽  
Small Scale Structures

AbstractDissipation of MHD waves generated in the lower solar atmosphere has long been proposed as a means to heat the solar corona. Because of the extremely low dissipation coefficients of the coronal plasma large gradients are necessary to efficiently dissipate such waves. Interactions with the inhomogeneities of the background medium may represent a way to create small scale structures, phase-mixing and resonant absorption being important examples. The generalization of such ideas to propagation in complex geometries (e.g., containing X type neutral points) and the extension to nonlinear effects are paramount to the development of wave-heating theories.

Exploring Coronal Structures with SOHO

2000 ◽  
Vol 179 ◽  
pp. 403-406
Author(s):  
M. Karovska ◽  
B. Wood ◽  
J. Chen ◽  
J. Cook ◽  
R. Howard
Keyword(s):  
Solar Corona ◽  
Image Enhancement ◽  
Coronal Mass Ejections ◽  
Dynamical Evolution ◽  
Small Scale ◽  
Low Contrast ◽  
Contrast Structures ◽  
Scale Structures ◽  
Small Scale Structures ◽  
Coronal Structures

AbstractWe applied advanced image enhancement techniques to explore in detail the characteristics of the small-scale structures and/or the low contrast structures in several Coronal Mass Ejections (CMEs) observed by SOHO. We highlight here the results from our studies of the morphology and dynamical evolution of CME structures in the solar corona using two instruments on board SOHO: LASCO and EIT.

scholarly journals Contribution of observed multi frequency spectrum of Alfvén waves to coronal heating

2019 ◽  
Vol 623 ◽  
pp. A37 ◽  
Author(s):  
P. Pagano ◽  
I. De Moortel
Keyword(s):  
Active Region ◽  
Power Spectrum ◽  
Solar Corona ◽  
Coronal Loop ◽  
Alfven Waves ◽  
Mhd Waves ◽  
Alfvén Waves ◽  
Coronal Loops ◽  
Phase Mixing ◽  
Transverse Oscillations

Context. Whilst there are observational indications that transverse magnetohydrodynamic (MHD) waves carry enough energy to maintain the thermal structure of the solar corona, it is not clear whether such energy can be efficiently and effectively converted into heating. Phase-mixing of Alfvén waves is considered a candidate mechanism, as it can develop transverse gradient where magnetic energy can be converted into thermal energy. However, phase-mixing is a process that crucially depends on the amplitude and period of the transverse oscillations, and only recently have we obtained a complete measurement of the power spectrum for transverse oscillations in the corona. Aims. We aim to investigate the heating generated by phase-mixing of transverse oscillations triggered by buffeting of a coronal loop that follows from the observed coronal power spectrum as well as the impact of these persistent oscillations on the structure of coronal loops. Methods. We considered a 3D MHD model of an active region coronal loop and we perturbed its footpoints with a 2D horizontal driver that represents a random buffeting motion of the loop footpoints. Our driver was composed of 1000 pulses superimposed to generate the observed power spectrum. Results. We find that the heating supply from the observed power spectrum in the solar corona through phase-mixing is not sufficient to maintain the million-degree active region solar corona. We also find that the development of Kelvin–Helmholtz instabilities could be a common phenomenon in coronal loops that could affect their apparent life time. Conclusions. This study concludes that is unlikely that phase-mixing of Alfvén waves resulting from an observed power spectrum of transverse coronal loop oscillations can heat the active region solar corona. However, transverse waves could play an important role in the development of small scale structures.

scholarly journals Phase Mixing of Propagating Alfvén Waves

1985 ◽  
Vol 107 ◽  
pp. 365-369
Author(s):  
L. Nocera ◽  
B. Leroy ◽  
E. R. Priest
Keyword(s):  
Solar Corona ◽  
Solar Atmosphere ◽  
Outer Part ◽  
Alfven Waves ◽  
Mhd Waves ◽  
Alfvén Waves ◽  
Phase Mixing ◽  
The Waves

Among MHD waves, Alfvén waves have been proved to be the best candidates to reach the solar corona and, eventually, to be responsible for the heating of this outer part of the solar atmosphere. The problem arises, however, about the mechanism able to transform the energy stored in the waves into heat.

scholarly journals Effect of coronal loop structure on wave heating through phase mixing

2020 ◽  
Vol 643 ◽  
pp. A73
Author(s):  
P. Pagano ◽  
I. De Moortel ◽  
R. J. Morton
Keyword(s):  
Coronal Loop ◽  
Magnetic Energy ◽  
Thermal Structure ◽  
Initial Density ◽  
Mhd Waves ◽  
Transverse Waves ◽  
Phase Mixing ◽  
Wave Heating ◽  
Subsequent Effect ◽  
The Impact

Context. The mechanism(s) behind coronal heating still elude(s) direct observation and modelling of viable theoretical processes and the subsequent effect on coronal structures is one of the key tools available to assess possible heating mechanisms. Wave heating via the phase mixing of magnetohydrodynamic (MHD) transverse waves has been proposed as a possible way to convert magnetic energy into thermal energy, but MHD models increasingly suggest this is not an efficient enough mechanism. Aims. We modelled heating by phase mixing transverse MHD waves in various configurations in order to investigate whether certain circumstances can enhance the heating sufficiently to sustain the million degree solar corona and to assess the impact of the propagation and phase mixing of transverse MHD waves on the structure of the boundary shell of coronal loops. Methods. We used 3D MHD simulations of a pre-existing density enhancement in a magnetised medium and a boundary driver to trigger the propagation of transverse waves with the same power spectrum as measured by the Coronal Multi-Channel Polarimeter. We consider different density structures, boundary conditions at the non-drive footpoint, characteristics of the driver, and different forms of magnetic resistivity. Results. We find that different initial density structures significantly affect the evolution of the boundary shell and that some driver configurations can enhance the heating generated from the dissipation of the MHD waves. In particular, drivers coherent on a larger spatial scale and higher dissipation coefficients can generate significant heating, although it is still insufficient to balance the radiative losses in this setup. Conclusions. We conclude that while phase mixing of transverse MHD waves is unlikely to sustain the thermal structure of the corona, there are configurations that allow for an enhanced efficiency of this mechanism. We provide possible signatures to identify the presence of such configurations, such as the location of where the heating is deposited along the coronal loop.

The nature of kink MHD waves in the solar corona: magnetic twist and phase mixing

2020 ◽  
Vol 497 (1) ◽  
pp. 1135-1142
Author(s):  
K Bahari ◽  
Z Ebrahimi
Keyword(s):  
Magnetic Field ◽  
Flux Tube ◽  
Mhd Waves ◽  
Small Scale ◽  
Transitional Layer ◽  
Restoring Force ◽  
Temporal Behaviour ◽  
Phase Mixing ◽  
Background Density ◽  
Kink Waves

ABSTRACT To study the nature of magnetohydrodynamic (MHD) kink waves, the temporal behaviour of an initial kink perturbation of a typical coronal flux tube has been investigated in this paper. The flux tube has a transitional layer that separates the core region of the tube from the surrounding environment. In the transitional layer, the background density and magnetic field varies continuously from the internal to the external values. The magnetic field is straight and aligned with the tube axis in the internal and external regions of the flux tube, but is assumed to be twisted in the transitional layer. Hence, in the transitional layer the background Alfvén speed is inhomogeneous and perturbations become out of phase due to the process of phase mixing. Our result shows that as the energy of the wave transfers to the local Alfvén waves in the inhomogeneous region, the magnetic tension force becomes the dominant restoring force of the wave. The numerical results show that the nature of the small-scale oscillations in the transitional layer is determined by the ratio of the azimuthal components of the restoring forces.

scholarly journals Phase Mixing of Kink MHD Waves in the Solar Corona: Viscous Dissipation and Heating

2020 ◽  
Vol 893 (2) ◽  
pp. 157
Author(s):  
Zanyar Ebrahimi ◽  
Roberto Soler ◽  
Kayoomars Karami
Keyword(s):  
Solar Corona ◽  
Viscous Dissipation ◽  
Mhd Waves ◽  
Phase Mixing

scholarly journals Numerical Simulation of Twisted Solar Corona

1998 ◽  
Vol 185 ◽  
pp. 467-468
Author(s):  
S. Parhi ◽  
B.P. Pandey ◽  
M. Goossens ◽  
G.S. Lakhina
Keyword(s):  
Numerical Simulation ◽  
Wave Propagation ◽  
Solar Corona ◽  
Temperature Profile ◽  
Resonant Absorption ◽  
Wave Generation ◽  
Coronal Plasma ◽  
Mhd Waves ◽  
Coronal Temperature ◽  
Physical Picture

The solar corona supports a variety of waves generated by convective upwelling motion in the photosphere. In order to explain the observed coronal temperature profile, resonant absorption of MHD waves by coronal plasma (Goossens et al, 1995) has been proposed as a possible candidate. The physical picture is that the footpoint motion in the photosphere constantly stirs the coronal plasma leading to the MHD wave generation which is then resonantly absorbed producing the enhanced heating of the corona. Here we consider the problem of MHD wave propagation in a twisted solar corona.

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