Acoustic Wave Properties in Footpoints of Coronal Loops in 3D MHD Simulations

Abstract Acoustic waves excited in the photosphere and below might play an integral part in the heating of the solar chromosphere and corona. However, it is yet not fully clear how much of the initially acoustic wave flux reaches the corona and in what form. We investigate the wave propagation, damping, transmission, and conversion in the lower layers of the solar atmosphere using 3D numerical MHD simulations. A model of a gravitationally stratified expanding straight coronal loop, stretching from photosphere to photosphere, is perturbed at one footpoint by an acoustic driver with a period of 370 s. For this period, acoustic cutoff regions are present below the transition region (TR). About 2% of the initial energy from the driver reaches the corona. The shape of the cutoff regions and the height of the TR show a highly dynamic behavior. Taking only the driven waves into account, the waves have a propagating nature below and above the cutoff region, but are standing and evanescent within the cutoff region. Studying the driven waves together with the background motions in the model reveals standing waves between the cutoff region and the TR. These standing waves cause an oscillation of the TR height. In addition, fast or leaky sausage body-like waves might have been excited close to the base of the loop. These waves then possibly convert to fast or leaky sausage surface-like waves at the top of the main cutoff region, followed by a conversion to slow sausage body-like waves around the TR.

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ANALYSIS OF DISPERSION ERRORS IN ACOUSTIC WAVE SIMULATIONS

Revista de Engenharia Térmica ◽

10.5380/reterm.v5i1.61663 ◽

2006 ◽

Vol 5 (1) ◽

pp. 62

Author(s):

R. A. C. Germanos ◽

L. F. De Souza

Keyword(s):

Acoustic Wave ◽

Fourth Order ◽

Finite Differences ◽

Acoustic Waves ◽

Time Integration ◽

Compact Scheme ◽

High Order Accuracy ◽

Discretization Schemes ◽

Analysis Of Dispersion ◽

The Waves

The governing equations of the acoustic problem are the compressible Euler equations. The discretization of these equations has to ensure that the acoustic waves are transported with non-dispersive and non-dissipative characteristics. In the present study numerical simulations of a standing acoustic wave are performed. Four different space discretization schemes are tested, namely, a second order finite-differences, a fourth order finitedifferences, a fourth order finite-differences compact scheme and a sixth order finite-differences compact scheme. The time integration is done with a fourth order Runge-Kutta scheme. The results obtained are compared with linearized analytical solutions. The influence of the dispersion on the simulation of a standing wave is analyzed. The results confirm that high order accuracy schemes can be more efficient for simulation of acoustic waves, especially the waves with high frequency.

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Two-fluid simulations of waves in the solar chromosphere

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834154 ◽

2019 ◽

Vol 627 ◽

pp. A25 ◽

Cited By ~ 7

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.

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Numerical modelling of MHD waves in the solar chromosphere

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2005.1705 ◽

2005 ◽

Vol 364 (1839) ◽

pp. 395-404 ◽

Cited By ~ 22

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.

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Research on the Method to Decompose Propagation Sound Wave in Annular Duct

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.472-475.1074 ◽

2012 ◽

Vol 472-475 ◽

pp. 1074-1077

Author(s):

Zhan Xin Liu

Keyword(s):

Acoustic Wave ◽

Acoustic Waves ◽

Decomposition Methods ◽

Benchmark Problems ◽

Fourier Mode ◽

Governing Equations ◽

Experiment Data ◽

Annular Duct ◽

Energy Relations ◽

The Waves

There are many benchmark problems which have exact solutions or experiment data to gauge the simulation of aeroacoustic problems. Annular duct acoustic modes are good benchmark problems of this kind. The waves propagated along the duct can be considered as the summation of infinite Fourier modes. The energy relations of a single Fourier mode are deduced from governing equations in this paper. To investigate the properties of acoustic wave propagating along the duct, it’s necessary to decompose acoustic waves in the duct into multiple Fourier modes; the decomposition methods are presented.

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Determination of the Acoustic Wave Flux in the Lower Solar Chromosphere

The Astrophysical Journal ◽

10.1086/504887 ◽

2006 ◽

Vol 646 (1) ◽

pp. 579-592 ◽

Cited By ~ 48

Author(s):

Astrid Fossum ◽

Mats Carlsson

Keyword(s):

Acoustic Wave ◽

Solar Chromosphere ◽

Wave Flux

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Formation of a Complex Topologies of SAW-Based Inertial Sensors by Laser Thin Film Local Evaporation

Micromachines ◽

10.3390/mi12010010 ◽

2020 ◽

Vol 12 (1) ◽

pp. 10

Author(s):

Alexander Kukaev ◽

Dmitry Lukyanov ◽

Denis Mikhailenko ◽

Daniil Safronov ◽

Sergey Shevchenko ◽

...

Keyword(s):

Thin Film ◽

Acoustic Wave ◽

Surface Acoustic Wave ◽

Acoustic Waves ◽

Inertial Sensors ◽

Surface Acoustic Waves ◽

Sensing Element ◽

Small Series ◽

Evaporation Technique ◽

Photolithography Process

Originally, sensors based on surface acoustic waves are fabricated using photolithography, which becomes extremely expensive when a small series or even single elements are needed for the research. A laser thin film local evaporation technique is proposed to substitute the photolithography process in the production of surface acoustic wave based inertial sensors prototypes. To estimate its potential a prototype of a surface acoustic wave gyroscope sensing element was fabricated and tested. Its was shown that the frequency mismatch is no more than 1%, but dispersion of the wave on small inertial masses leads to a spurious parasitic signal on receiving electrodes. Possible ways of its neglecting is discussed.

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Can Multi-threaded Flux Tubes in Coronal Arcades Support a Magnetohydrodynamic Avalanche?

Solar Physics ◽

10.1007/s11207-021-01865-7 ◽

2021 ◽

Vol 296 (8) ◽

Author(s):

J. Threlfall ◽

J. Reid ◽

A. W. Hood

Keyword(s):

Magnetic Fields ◽

Three Dimensional ◽

Coronal Loops ◽

Flux Tubes ◽

Single Thread ◽

Mhd Instabilities ◽

Mhd Instability ◽

Mhd Simulations ◽

Ideal Mhd ◽

Model Geometry

AbstractMagnetohydrodynamic (MHD) instabilities allow energy to be released from stressed magnetic fields, commonly modelled in cylindrical flux tubes linking parallel planes, but, more recently, also in curved arcades containing flux tubes with both footpoints in the same photospheric plane. Uncurved cylindrical flux tubes containing multiple individual threads have been shown to be capable of sustaining an MHD avalanche, whereby a single unstable thread can destabilise many. We examine the properties of multi-threaded coronal loops, wherein each thread is created by photospheric driving in a realistic, curved coronal arcade structure (with both footpoints of each thread in the same plane). We use three-dimensional MHD simulations to study the evolution of single- and multi-threaded coronal loops, which become unstable and reconnect, while varying the driving velocity of individual threads. Experiments containing a single thread destabilise in a manner indicative of an ideal MHD instability and consistent with previous examples in the literature. The introduction of additional threads modifies this picture, with aspects of the model geometry and relative driving speeds of individual threads affecting the ability of any thread to destabilise others. In both single- and multi-threaded cases, continuous driving of the remnants of disrupted threads produces secondary, aperiodic bursts of energetic release.

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Investigation of the surface acoustic wave properties of heteroepitaxial ZnO layers on Al2O3

Journal of Applied Physics ◽

10.1063/1.1661779 ◽

1972 ◽

Vol 43 (9) ◽

pp. 3627-3631 ◽

Cited By ~ 18

Author(s):

Frank Pizzarello

Keyword(s):

Acoustic Wave ◽

Surface Acoustic Wave ◽

Wave Properties

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Parametric excitation of magnetoacoustic waves by a pump magnetic field in a high-β plasma

Journal of Plasma Physics ◽

10.1017/s0022377800020456 ◽

1977 ◽

Vol 17 (1) ◽

pp. 93-103 ◽

Cited By ~ 7

Author(s):

N. F. Cramer

Keyword(s):

Magnetic Field ◽

Parametric Excitation ◽

Acoustic Waves ◽

Magnetic Pressure ◽

Gas Pressure ◽

Alfven Wave ◽

Fast Wave ◽

Magnetoacoustic Waves ◽

Background Magnetic Field ◽

The Waves

The parametric excitation of slow, intermediate (Alfvén) and fast magneto-acoustic waves by a modulated spatially non-uniform magnetic field in a plasma with a finite ratio of gas pressure to magnetic pressure is considered. The waves are excited in pairs, either pairs of the same mode, or a pair of different modes. The growth rates of the instabilities are calculated and compared with the known result for the Alfvén wave in a zero gas pressure plasma. The only waves that are found not to be excited are the slow plus fast wave pair, and the intermediate plus slow or fast wave pair (unless the waves have a component of propagation direction perpendicular to both the background magnetic field and the direction of non-uniformity of the field).

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