scholarly journals Heating of a Quiet Region of the Solar Chromosphere by Ion and Neutral Acoustic Waves

2019 ◽  
Vol 878 (2) ◽  
pp. 81 ◽  
Author(s):  
B. Kuźma ◽  
D. Wójcik ◽  
K. Murawski
Keyword(s):  
Acoustic Waves ◽  
Solar Chromosphere ◽  
Quiet Region

High-frequency acoustic waves are not sufficient to heat the solar chromosphere

Nature ◽  
2005 ◽  
Vol 435 (7044) ◽  
pp. 919-921 ◽  
Author(s):  
Astrid Fossum ◽  
Mats Carlsson
Keyword(s):  
Acoustic Waves ◽  
High Frequency ◽  
Solar Chromosphere

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.

Numerical modelling of MHD waves in the solar chromosphere

2005 ◽  
Vol 364 (1839) ◽  
pp. 395-404 ◽  
Author(s):  
Mats Carlsson ◽  
Thomas J Bogdan
Keyword(s):  
Magnetic Field ◽  
Acoustic Waves ◽  
Mode Conversion ◽  
Three Dimensions ◽  
Mhd Waves ◽  
Solar Chromosphere ◽  
Fast Mode ◽  
Reflected Waves ◽  
The Waves ◽  
The Magnetic Field

Acoustic waves are generated by the convective motions in the solar convection zone. When propagating upwards into the chromosphere they reach the height where the sound speed equals the Alfvén speed and they undergo mode conversion, refraction and reflection. We use numerical simulations to study these processes in realistic configurations where the wavelength of the waves is similar to the length scales of the magnetic field. Even though this regime is outside the validity of previous analytic studies or studies using ray-tracing theory, we show that some of their basic results remain valid: the critical quantity for mode conversion is the angle between the magnetic field and the k-vector: the attack angle. At angles smaller than 30° much of the acoustic, fast mode from the photosphere is transmitted as an acoustic, slow mode propagating along the field lines. At larger angles, most of the energy is refracted/reflected and returns as a fast mode creating an interference pattern between the upward and downward propagating waves. In three-dimensions, this interference between waves at small angles creates patterns with large horizontal phase speeds, especially close to magnetic field concentrations. When damping from shock dissipation and radiation is taken into account, the waves in the low–mid chromosphere have mostly the character of upward propagating acoustic waves and it is only close to the reflecting layer we get similar amplitudes for the upward propagating and refracted/reflected waves. The oscillatory power is suppressed in magnetic field concentrations and enhanced in ring-formed patterns around them. The complex interference patterns caused by mode-conversion, refraction and reflection, even with simple incident waves and in simple magnetic field geometries, make direct inversion of observables exceedingly difficult. In a dynamic chromosphere it is doubtful if the determination of mean quantities is even meaningful.

scholarly journals Observational study of chromospheric heating by acoustic waves

2020 ◽  
Vol 642 ◽  
pp. A52
Author(s):  
V. Abbasvand ◽  
M. Sobotka ◽  
M. Švanda ◽  
P. Heinzel ◽  
M. García-Rivas ◽  
...  
Keyword(s):  
Energy Flux ◽  
Acoustic Waves ◽  
Acoustic Energy ◽  
Solar Chromosphere ◽  
Echelle Spectrograph ◽  
Quiet Sun ◽  
Non Local ◽  
Radiative Losses ◽  
Semi Empirical

Aims. Our aim is to investigate the role of acoustic and magneto-acoustic waves in heating the solar chromosphere. Observations in strong chromospheric lines are analyzed by comparing the deposited acoustic-energy flux with the total integrated radiative losses. Methods. Quiet-Sun and weak-plage regions were observed in the Ca II 854.2 nm and Hα lines with the Fast Imaging Solar Spectrograph (FISS) at the 1.6-m Goode Solar Telescope on 2019 October 3 and in the Hα and Hβ lines with the echelle spectrograph attached to the Vacuum Tower Telescope on 2018 December 11 and 2019 June 6. The deposited acoustic energy flux at frequencies up to 20 mHz was derived from Doppler velocities observed in line centers and wings. Radiative losses were computed by means of a set of scaled non-local thermodynamic equilibrium 1D hydrostatic semi-empirical models obtained by fitting synthetic to observed line profiles. Results. In the middle chromosphere (h = 1000–1400 km), the radiative losses can be fully balanced by the deposited acoustic energy flux in a quiet-Sun region. In the upper chromosphere (h >  1400 km), the deposited acoustic flux is small compared to the radiative losses in quiet as well as in plage regions. The crucial parameter determining the amount of deposited acoustic flux is the gas density at a given height. Conclusions. The acoustic energy flux is efficiently deposited in the middle chromosphere, where the density of gas is sufficiently high. About 90% of the available acoustic energy flux in the quiet-Sun region is deposited in these layers, and thus it is a major contributor to the radiative losses of the middle chromosphere. In the upper chromosphere, the deposited acoustic flux is too low, so that other heating mechanisms have to act to balance the radiative cooling.

scholarly journals High frequency generation in the corona: Resonant cavities

2018 ◽  
Vol 611 ◽  
pp. A10 ◽  
Author(s):  
I. C. Santamaria ◽  
T. Van Doorsselaere
Keyword(s):  
Magnetic Field ◽  
Shock Wave ◽  
Acoustic Waves ◽  
High Frequency ◽  
Spatial Scales ◽  
Wave Train ◽  
Null Point ◽  
Solar Chromosphere ◽  
High Frequency Region ◽  
Frequency Wave

Aims. Null points are prominent magnetic field singularities in which the magnetic field strength strongly decreases in very small spatial scales. Around null points, predicted to be ubiquitous in the solar chromosphere and corona, the wave behavior changes considerably. Null points are also responsible for driving very energetic phenomena, and for contributing to chromospheric and coronal heating. In previous works we demonstrated that slow magneto-acoustic shock waves were generated in the chromosphere propagate through the null point, thereby producing a train of secondary shocks escaping along the field lines. A particular combination of the shock wave speeds generates waves at a frequency of 80 MHz. The present work aims to investigate this high frequency region around a coronal null point to give a plausible explanation to its generation at that particular frequency. Methods. We carried out a set of two-dimensional numerical simulations of wave propagation in the neighborhood of a null point located in the corona. We varied both the amplitude of the driver and the atmospheric properties to investigate the sensitivity of the high frequency waves to these parameters. Results. We demonstrate that the wave frequency is sensitive to the atmospheric parameters in the corona, but it is independent of the strength of the driver. Thus, the null point behaves as a resonant cavity generating waves at specific frequencies that depend on the background equilibrium model. Moreover, we conclude that the high frequency wave train generated at the null point is not necessarily a result of the interaction between the null point and a shock wave. This wave train can be also developed by the interaction between the null point and fast acoustic-like magneto-acoustic waves, that is, this interaction within the linear regime.

scholarly journals High frequency oscillations in the solar chromosphere and their connection with heating

2007 ◽  
Vol 3 (S247) ◽  
pp. 312-315 ◽  
Author(s):  
Aleksandra Andic ◽  
M. Mathioudakis ◽  
F. P. Keenan ◽  
D. B. Jess ◽  
D. S. Bloomfield
Keyword(s):  
Magnetic Fields ◽  
Acoustic Waves ◽  
High Frequency ◽  
Solar Observatory ◽  
Solar Chromosphere ◽  
Frequency Interval ◽  
Solar Telescope ◽  
National Solar Observatory ◽  
High Frequency Oscillations ◽  
Using Data

AbstractHigh frequency acoustic waves have been suggested as a source of mechanical heating in the quiet solar chromosphere. To investigate this, we have observed intensity oscillations of several lines in the frequency interval 1.64-70mHz using data from the VTT Tenerife and the Dunn Solar Telescope at the National Solar Observatory. Our analysis of Fe i 543.45 nm, Fe i 543.29 nm and the G-band, indicate that the majority of oscillations are connected with the magnetic fields and do not provide sufficient mechanical flux for the heating of the chromosphere. This correlation is also observed in quiet Sun areas.

scholarly journals The Heating of the Quiet Solar Chromosphere

1990 ◽  
Vol 142 ◽  
pp. 197-206
Author(s):  
Wolfgang Kalkofen
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Acoustic Waves ◽  
Solar Chromosphere ◽  
Temperature Structure ◽  
Cell Interior ◽  
Long Period ◽  
Low Field ◽  
Magnetic Elements ◽  
Short Period

The quiet solar chromosphere shows three distinct regions. Ordered according to the strength of the emission from the low and middle chromosphere they are (1) the magnetic elements on the boundary of supergranulation cells, (2) the bright points in the cell interior, and (3) the truly quiet chromosphere, also in the cell interior. The magnetic elements on the cell boundary are associated with intense magnetic fields and are heated by waves with very long periods, ranging from six to twelve minutes; the bright points are associated with magnetic elements of low field strength and are heated by (long-period) waves with periods near the acoustic cutoff period of three minutes; and the quiet cell interior, which is free of magnetic field, may be heated by short-period acoustic waves, with periods below one minute. This paper reviews mainly the heating of the bright points and concludes that the large-amplitude, long-period waves heating the bright points dissipate enough energy to account for their chromospheric temperature structure.

scholarly journals Heating and dynamics of the quiet solar chromosphere

2007 ◽  
Vol 3 (S247) ◽  
pp. 93-98
Author(s):  
Wolfgang Kalkofen
Keyword(s):  
Acoustic Waves ◽  
Energy Exchange ◽  
Spatial Scales ◽  
Quantitative Measure ◽  
Hydrodynamical Model ◽  
Radiative Energy ◽  
Solar Chromosphere ◽  
Spatial Averaging ◽  
Heating Mechanism ◽  
Open Question

AbstractThe quiet solar chromosphere in regions with negligible magnetic field is believed to be heated by acoustic waves. But their energy flux, measured in the upper photosphere with the Transition Region And Coronal Explorer (TRACE), has been found to be insufficient to account for the radiative emission from the chromosphere. Wedemeyer-Böhm et al. (2007) and Cuntz et al. (2007), employing a 3D hydrodynamical model by Wedemeyer et al. (2004), have proposed that the spatial resolution of TRACE is inadequate to resolve intensity fluctuations that occur on small spatial scales. This paper accepts the principle of spatial averaging by TRACE as a qualitative explanation for the low acoustic flux but finds that the hydrodynamical model is too much simplified in the treatment of radiative energy exchange to provide a quantitative measure of the suppression of the fluctuations. The heating mechanism of the chromosphere thus remains an open question.

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