scholarly journals The solar corona as an active medium for magnetoacoustic waves

2021 ◽  
Author(s):  
Dmitrii Kolotkov ◽  
Dmitrii Zavershinskii ◽  
Valery M Nakariakov
Keyword(s):  
Solar Corona ◽  
Active Medium ◽  
Thermal Equilibrium ◽  
Research Field ◽  
Coronal Heating ◽  
Slow Waves ◽  
Back Reaction ◽  
Heating Source ◽  
Magnetoacoustic Waves ◽  
Gain Energy

Abstract The presence and interplay of continuous cooling and heating processes maintaining the corona of the Sun at the observed one million K temperature were recently understood to have crucial effects on the dynamics and stability of magnetoacoustic waves. These essentially compressive waves perturb the coronal thermal equilibrium, leading to the phenomenon of a wave-induced thermal misbalance. Representing an additional natural mechanism for the exchange of energy between the plasma and the wave, thermal misbalance makes the corona an active medium for magnetoacoustic waves, so that the wave can not only lose but also gain energy from the coronal heating source (similarly to burning gases, lasers and masers). We review recent achievements in this newly emerging research field, focussing on the effects that slow-mode magnetoacoustic waves experience as a back-reaction of this perturbed coronal thermal equilibrium. The new effects include enhanced frequency-dependent damping or amplification of slow waves, and effective, not associated with the coronal plasma non-uniformity, dispersion. We also discuss the possibility to probe the unknown coronal heating function by observations of slow waves and linear theory of thermal instabilities. The manifold of the new properties that slow waves acquire from a thermodynamically active nature of the solar corona indicate a clear need for accounting for the effects of combined coronal heating/cooling processes not only for traditional problems of the formation and evolution of prominences and coronal rain, but also for an adequate modelling and interpretation of magnetohydrodynamic waves.

scholarly journals Seismological constraints on the solar coronal heating function

2020 ◽  
Vol 644 ◽  
pp. A33
Author(s):  
D. Y. Kolotkov ◽  
T. J. Duckenfield ◽  
V. M. Nakariakov
Keyword(s):  
Thermal Equilibrium ◽  
Solar Physics ◽  
Coronal Heating ◽  
Back Reaction ◽  
Heating Mechanism ◽  
Heating And Cooling ◽  
Specific Choice ◽  
Magnetoacoustic Waves ◽  
Unstable Case ◽  
Wave Induced

Aims. The hot solar corona exists because of the balance between radiative and conductive cooling and some counteracting heating mechanism that remains one of the major puzzles in solar physics. Methods. The coronal thermal equilibrium is perturbed by magnetoacoustic waves, which are abundantly present in the corona, causing a misbalance between the heating and cooling rates. As a consequence of this misbalance, the wave experiences a back-reaction, either losing or gaining energy from the energy supply that heats the plasma, at timescales comparable to the wave period. Results. In particular, the plasma can be subject to wave-induced instability or over-stability, depending on the specific choice of the coronal heating function. In the unstable case, the coronal thermal equilibrium would be violently destroyed, which does not allow for the existence of long-lived plasma structures typical for the corona. Based on this, we constrained the coronal heating function using observations of slow magnetoacoustic waves in various coronal plasma structures.

scholarly journals The ionization and thermal balance in P Cygni’s wind revisited

1989 ◽  
Vol 113 ◽  
pp. 263-264
Author(s):  
D.R.H. Johnson ◽  
J.E. Drew
Keyword(s):  
Thermal Equilibrium ◽  
Thermal Balance ◽  
Heating Source ◽  
Helium Line

Abstract.The statistical and thermal equilibrium of P Cygni’s wind as a function of radius is investigated using the model of Drew (1985) with an improved treatment of hydrogen. Provisional calculated hydrogen and helium line fluxes are compared with observation. The wind temperature is found to be cooler than observation implies, and a further heating source is tentatively identified.

scholarly journals Stellar Coronae

1980 ◽  
Vol 5 ◽  
pp. 419-428 ◽  
Author(s):  
G. S. Vaiana
Keyword(s):  
Magnetic Fields ◽  
Solar Corona ◽  
Main Sequence ◽  
High Energy ◽  
Coronal Heating ◽  
Standard Theory ◽  
Plasma Structure ◽  
X Ray ◽  
Spatially Resolved ◽  
Surface Convection

The standard theory of stellar coronae requires the presence of vigorous surface convection. In consequence, the expectation of such a theory is that stellar x-ray emission — if due to a corona — should be limited to a subset of stars (principally those of main sequence spectral types F and G), and therefore should be relatively rare. This theory also makes detailed predictions about coronal heating, which are subject to test if spatially resolved coronal data are available. We are now in a position to subject the standard coronal scenarios to observational scrutiny on both counts: Skylab and later observations have supplied us with spatially resolved data of the solar corona, while the succession of high-energy x-ray astronomy satellites, culminating with EINSTEIN, now gives us a long-awaited glimpse of stellar x-ray emission throughout the K-R diagram.I will maintain that these new data imply that coronal x-ray emission dominantly derives from plasma structure confined by stellar surface magnetic fields; that coronal heating is likely to be non-acoustic in character and involves the confining magnetic fields; that stellar x-ray emission is not well correlated with the level of surface convection activity. These results of course cast serious doubt upon the viability of the standard theory of stellar coronal formation. In the following, I will try to very briefly summarize the solar and stellar data, to present the context in which they were initially obtained, and very briefly sketch the new coronal picture we are pursuing. The results presented here are excerpted from lectures presented by R. Rosner and myself recently at Erice, Italy (viz. Vaiana 1979) and from the preliminary results of the EINSTEIN Stellar Survey (Vaiana et al. 1979). The latter, part of a larger effort in x-ray astronomy led by R. Giacconi, involves the work of many people, including F.R. Harnden, L. Golub, P. Gorenstein, R. Rosner, F. Seward, K. Topika at CFA, as well as a number of EINSTEIN guest investigators.

scholarly journals Coronal Heating Mechanism in the Presence of a Flow: A Numerical Approach

1998 ◽  
Vol 185 ◽  
pp. 469-470
Author(s):  
S. Parhi ◽  
T. Tanaka
Keyword(s):  
Magnetic Fields ◽  
Solar Corona ◽  
Plasma Heating ◽  
Inhomogeneous Plasma ◽  
Resonant Absorption ◽  
Numerical Approach ◽  
Coronal Heating ◽  
Heating Mechanism ◽  
Driving Current ◽  
Field Lines

The solar corona is a hot, tenuous plasma permeated with the structured magnetic fields. A variety of waves is generated in the corona due to the convective upwelling motion in the photosphere. The excitation of MHD fluctuations is generated by the footpoint motion of the field lines in the photosphere. Resonant absorption of the Alfvén waves in an inhomogeneous plasma has been suggested as a means of driving current and plasma heating in the corona (Sakurai et al., 1991). We study this problem in the presence of flow.

Landau damped kinetic Alfvén waves and coronal heating

2009 ◽  
Vol 76 (2) ◽  
pp. 239-246 ◽  
Author(s):  
R. P. SHARMA ◽  
SACHIN KUMAR
Keyword(s):  
Solar Corona ◽  
Initial Conditions ◽  
Planck Equation ◽  
Alfven Waves ◽  
Coronal Heating ◽  
Landau Damping ◽  
Alfvén Waves ◽  
Energetic Electrons ◽  
Turbulent Spectra ◽  
Kinetic Alfvén Waves

AbstractSome recent observations of solar corona suggest that the kinetic Alfvén waves (KAWs) turbulence may be responsible for electron acceleration in solar corona and coronal heating. In the present research, we investigate the turbulent spectra of KAW due to filamentation process in the presence of Landau damping and particle energization. We present here the numerical simulation of model equation governing the nonlinear dynamics of the KAW in the presence of Landau damping. When the ponderomotive and Joule heating nonlinearities are incorporated in the KAW dynamics, the power spectra of the turbulent field is evaluated and used for particle heating. Our results reveal the formation of damped coherent magnetic filamentary structures and the turbulent spectra. The effect of Landau damping is to make the turbulent spectra steeper. Two types of scalings k−3.6 and k−4 have been obtained. We have studied the turbulence with different initial conditions. Using the Fokker–Planck equation with the new velocity space diffusion coefficient, we find the distribution function of energetic electrons in these turbulent structures. Landau damped KAWs may be responsible for the acceleration of the energetic electrons in solar corona and coronal heating.

BACK REACTION IN SCHWARZSCHILD–de SITTER SPACETIME WITH A MASSLESS QUANTUM FIELD

2006 ◽  
Vol 21 (02) ◽  
pp. 169-179
Author(s):  
P. I. KURIAKOSE ◽  
V. C. KURIAKOSE
Keyword(s):  
Black Hole ◽  
Effective Potential ◽  
Thermal Equilibrium ◽  
Back Reaction ◽  
De Sitter Spacetime ◽  
Quantum Field ◽  
De Sitter ◽  
Spacetime Geometry ◽  
Sitter Spacetime ◽  
Massless Quantum

Back reaction in the Schwarzschild–de Sitter black hole in thermal equilibrium with conformal massless quantum field is discussed using the method of York. The presence of quantum field and back reaction ensures the entropy of dressed black hole. In the perturbed spacetime geometry, the nature of the effective potential and the orbits of massless and massive particles are also investigated.

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