Acoustic waves in two-fluid solar atmosphere model: cut-off periods, chromospheric cavity, and wave tunnelling

2018 ◽  
Vol 481 (1) ◽  
pp. 262-267 ◽  
Author(s):  
D Wójcik ◽  
K Murawski ◽  
Z E Musielak
Keyword(s):  
Solar Atmosphere ◽  
Acoustic Waves ◽  
Atmosphere Model ◽  
Two Fluid

scholarly journals Numerical simulations of the lower solar atmosphere heating by two-fluid nonlinear Alfvén waves

2020 ◽  
Vol 639 ◽  
pp. A45
Author(s):  
B. Kuźma ◽  
D. Wójcik ◽  
K. Murawski ◽  
D. Yuan ◽  
S. Poedts
Keyword(s):  
Magnetic Flux ◽  
Numerical Simulations ◽  
Solar Atmosphere ◽  
Flux Tube ◽  
Alfven Waves ◽  
Alfven Wave ◽  
Magnetic Flux Tube ◽  
Alfvén Waves ◽  
Two Fluid ◽  
Lower Solar Atmosphere

Context. We present new insight into the long-standing problem of plasma heating in the lower solar atmosphere in terms of collisional dissipation caused by two-fluid Alfvén waves. Aims. Using numerical simulations, we study Alfvén wave propagation and dissipation in a magnetic flux tube and their heating effect. Methods. We set up 2.5-dimensional numerical simulations with a semi-empirical model of a stratified solar atmosphere and a force-free magnetic field mimicking a magnetic flux tube. We consider a partially ionized plasma consisting of ion + electron and neutral fluids, which are coupled by ion-neutral collisions. Results. We find that Alfvén waves, which are directly generated by a monochromatic driver at the bottom of the photosphere, experience strong damping. Low-amplitude waves do not thermalize sufficient wave energy to heat the solar atmospheric plasma. However, Alfvén waves with amplitudes greater than 0.1 km s−1 drive through ponderomotive force magneto-acoustic waves in higher atmospheric layers. These waves are damped by ion-neutral collisions, and the thermal energy released in this process leads to heating of the upper photosphere and the chromosphere. Conclusions. We infer that, as a result of ion-neutral collisions, the energy carried initially by Alfvén waves is thermalized in the upper photosphere and the chromosphere, and the corresponding heating rate is large enough to compensate radiative and thermal-conduction energy losses therein.

scholarly journals Mode conversion of two-fluid shocks in a partially-ionised, isothermal, stratified atmosphere

2020 ◽  
Vol 637 ◽  
pp. A97
Author(s):  
B. Snow ◽  
A. Hillier
Keyword(s):  
Solar Atmosphere ◽  
Mode Conversion ◽  
Frictional Heating ◽  
Fast Mode ◽  
Compressional Waves ◽  
Pressure Scale ◽  
Velocity Drift ◽  
Two Fluid ◽  
Lower Solar Atmosphere

Context. The plasma of the lower solar atmosphere consists of mostly neutral particles, whereas the upper solar atmosphere is mostly made up of ionised particles and electrons. A shock that propagates upwards in the solar atmosphere therefore undergoes a transition where the dominant fluid is either neutral or ionised. An upwards propagating shock also passes a point where the sound and Alfvén speed are equal. At this point the energy of the acoustic shock can separated into fast and slow components. The way the energy is distributed between the two modes depends on the angle of magnetic field. Aims. We aim to investigate the separation of neutral and ionised species in a gravitationally stratified atmosphere. The role of two-fluid effects on the structure of the shocks post-mode-conversion and the frictional heating is quantified for different levels of collisional coupling. Methods. Two-fluid numerical simulations were performed using the (PIP) code of a wave steepening into a shock in an isothermal, partially-ionised atmosphere. The collisional coefficient was varied to investigate the regimes where the plasma and neutral species are weakly, strongly, and finitely coupled. Results. The propagation speeds of the compressional waves hosted by neutral and ionised species vary and, therefore, velocity drift between the two species is produced as the plasma attempts to propagate faster than the neutrals. This is most extreme for a fast-mode shock. We find that the collisional coefficient drastically impacts the features present in the system, specifically the mode conversion height, type of shocks present, and the finite shock widths created by the two-fluid effects. In the finitely-coupled regime, fast-mode shock widths can exceed the pressure scale height, which may lead to a new potential observable of two-fluid effects in the lower solar atmosphere.

scholarly journals Two-fluid simulations of waves in the solar chromosphere

2019 ◽  
Vol 627 ◽  
pp. A25 ◽  
Author(s):  
B. Popescu Braileanu ◽  
V. S. Lukin ◽  
E. Khomenko ◽  
Á. de Vicente
Keyword(s):  
Acoustic Waves ◽  
Hydrogen Plasma ◽  
The Other ◽  
Alfven Wave ◽  
Numerical Code ◽  
Solar Chromosphere ◽  
Charged Fluid ◽  
Induction Equation ◽  
The Waves ◽  
Two Fluid

Solar chromosphere consists of a partially ionized plasma, which makes modeling the solar chromosphere a particularly challenging numerical task. Here we numerically model chromospheric waves using a two-fluid approach with a newly developed numerical code. The code solves two-fluid equations of conservation of mass, momentum, and energy, together with the induction equation for the case of the purely hydrogen plasma with collisional coupling between the charged and neutral fluid components. The implementation of a semi-implicit algorithm allows us to overcome the numerical stability constraints due to the stiff collisional terms. We test the code against analytical solutions of acoustic and Alfvén wave propagation in uniform medium in several regimes of collisional coupling. The results of our simulations are consistent with the analytical estimates, and with other results described in the literature. In the limit of a large collisional frequency, the waves propagate with a common speed of a single fluid. In the other limit of a vanishingly small collisional frequency, the Alfvén waves propagate with an Alfvén speed of the charged fluid only, while the perturbation in neutral fluid is very small. The acoustic waves in these limits propagate with the sound speed corresponding to either the charges or the neutrals, while the perturbation in the other fluid component is negligible. Otherwise, when the collision frequency is similar to the real part of the wave frequency, the interaction between charges and neutrals through momentum-transfer collisions cause alterations of the waves frequencies and damping of the wave amplitudes.

scholarly journals Validation of the Alfvén Wave Solar Atmosphere Model (AWSoM) with Observations from the Low Corona to 1 au

2019 ◽  
Vol 887 (1) ◽  
pp. 83 ◽  
Author(s):  
Nishtha Sachdeva ◽  
Bart van der Holst ◽  
Ward B. Manchester ◽  
Gabor Tóth ◽  
Yuxi Chen ◽  
...  
Keyword(s):  
Solar Atmosphere ◽  
Alfven Wave ◽  
Atmosphere Model

scholarly journals Recent Advances in Acoustic Heating

1990 ◽  
Vol 142 ◽  
pp. 231-235
Author(s):  
P. Ulmschneider
Keyword(s):  
Shock Waves ◽  
Solar Atmosphere ◽  
Acoustic Waves ◽  
Radiation Loss ◽  
Rotating Stars ◽  
Magnetic Heating ◽  
Surface Variation ◽  
Chromospheric Emission ◽  
Surface Convection ◽  
Chromospheric Heating

Turbulent surface convection zones of stars generate acoustic waves which contribute to the heating of chromospheres and coronae. The dissipation of limiting strength acoustic shock waves agrees well with the empirically determined chromospheric radiation loss rates. Acoustic waves with frequency and energy required for the chromospheric heating are observed in the solar atmosphere. Acoustic heating can explain the basal chromospheric emission of slowly rotating stars and constitutes a weak background in faster rotating stars; it can not explain the emission-rotation correlation and the surface variation of emission which are due to magnetic heating.

Magnetic coupling of waves and oscillations in the lower solar atmosphere: can the tail wag the dog?

2005 ◽  
Vol 364 (1839) ◽  
pp. 351-381 ◽  
Author(s):  
Robert Erdélyi
Keyword(s):  
Magnetic Fields ◽  
Solar Atmosphere ◽  
Acoustic Waves ◽  
Large Scale ◽  
Magnetic Coupling ◽  
Small Scale ◽  
Coupling Mechanism ◽  
Frequency Shifts ◽  
Characteristic Features ◽  
Lower Solar Atmosphere

Can the ubiquitously magnetic solar atmosphere have any effect on solar global oscillations? Traditionally, solar atmospheric magnetic fields are considered to be somewhat less important for the existence and characteristic features of solar global oscillations ( p , f and the not-yet-observed g -modes). In this paper, I demonstrate the importance of the presence of magnetism and plasma dynamics for global resonant oscillations in the solar atmosphere. In particular, in the lower part of the solar atmosphere there are both coherent and random components of magnetic fields and velocity fields, each of which contribute on its own to the line widths and frequency variations of solar global acoustic waves. Changes in the coherent large-scale atmospheric magnetic fields cause frequency shifts of global oscillations over a solar cycle. The random character of the continuously emerging, more localized, magnetic carpet (i.e. small-scale, possibly even sub-resolution, loops) gives rise to additional frequency shifts. On the other hand, random and organized surface and sub-surface flows, like surface granulation, meridional flows or differential rotation, also affect the coupling mechanism of global oscillations to the lower magnetic atmosphere. The competition between magnetic fields and flows is inevitable. Finally, I shall discuss how solar global oscillations can resonantly interact with the overlaying inhomogeneous lower solar atmosphere embedded in a magnetic carpet. Line width broadening and distorsion of global acoustic modes will be discussed. The latter is suggested to be tested and measured by using ring-analysis techniques.

Nonlinear magneto-acoustic waves in the solar atmosphere

2001 ◽  
Vol 34 (2-4) ◽  
pp. 399-409
Author(s):  
César A. Mendoza-Briceño ◽  
Miguel H. Ibáñez ◽  
Valery M. Nakariakov
Keyword(s):  
Solar Atmosphere ◽  
Acoustic Waves

On the observation of traveling acoustic waves in the solar atmosphere using a magneto-optical filter

2007 ◽  
Vol 328 (3-4) ◽  
pp. 211-214 ◽  
Author(s):  
M. Haberreiter ◽  
W. Finsterle ◽  
S. M. Jefferies
Keyword(s):  
Solar Atmosphere ◽  
Acoustic Waves ◽  
Optical Filter

scholarly journals Simulating Solar Maximum Conditions Using the Alfvén Wave Solar Atmosphere Model (AWSoM)

2021 ◽  
Vol 923 (2) ◽  
pp. 176
Author(s):  
Nishtha Sachdeva ◽  
Gábor Tóth ◽  
Ward B. Manchester ◽  
Bart van der Holst ◽  
Zhenguang Huang ◽  
...  
Keyword(s):  
Solar Wind ◽  
Solar Atmosphere ◽  
Solar Maximum ◽  
Initial Conditions ◽  
Magnetic Activity ◽  
Alfven Wave ◽  
Time Of Arrival ◽  
Plasma Parameters ◽  
Modeling Framework ◽  
Atmosphere Model

Abstract To simulate solar coronal mass ejections (CMEs) and predict their time of arrival and geomagnetic impact, it is important to accurately model the background solar wind conditions in which CMEs propagate. We use the Alfvén Wave Solar atmosphere Model (AWSoM) within the the Space Weather Modeling Framework to simulate solar maximum conditions during two Carrington rotations and produce solar wind background conditions comparable to the observations. We describe the inner boundary conditions for AWSoM using the ADAPT global magnetic maps and validate the simulated results with EUV observations in the low corona and measured plasma parameters at L1 as well as at the position of the Solar Terrestrial Relations Observatory spacecraft. This work complements our prior AWSoM validation study for solar minimum conditions and shows that during periods of higher magnetic activity, AWSoM can reproduce the solar plasma conditions (using properly adjusted photospheric Poynting flux) suitable for providing proper initial conditions for launching CMEs.

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