Numerical simulations of waveperiods of stochastically-excited magnetoacoustic-gravity waves in a quiet region of the solar atmosphere

2018 ◽  
Author(s):  
J K Kraśkiewicz ◽  
K Murawski
Keyword(s):  
Numerical Simulations ◽  
Solar Atmosphere ◽  
Gravity Waves ◽  
Quiet Region

scholarly journals Numerical Simulations of Magnetoacoustic–Gravity Waves in the Solar Atmosphere

Solar Physics ◽  
2012 ◽  
Vol 283 (2) ◽  
pp. 383-399 ◽  
Author(s):  
K. Murawski ◽  
A. K. Srivastava ◽  
J. A. McLaughlin ◽  
R. Oliver
Keyword(s):  
Numerical Simulations ◽  
Solar Atmosphere ◽  
Gravity Waves

scholarly journals Five-Wave Resonances in Deep Water Gravity Waves: Integrability, Numerical Simulations and Experiments

Fluids ◽  
2021 ◽  
Vol 6 (6) ◽  
pp. 205
Author(s):  
Dan Lucas ◽  
Marc Perlin ◽  
Dian-Yong Liu ◽  
Shane Walsh ◽  
Rossen Ivanov ◽  
...  
Keyword(s):  
Normal Form ◽  
Numerical Simulations ◽  
Gravity Waves ◽  
Deep Water ◽  
Plane Waves ◽  
Surface Elevation ◽  
Wave Interactions ◽  
Frequency Space ◽  
Target Mode ◽  
The Hilbert Transform

In this work we consider the problem of finding the simplest arrangement of resonant deep-water gravity waves in one-dimensional propagation, from three perspectives: Theoretical, numerical and experimental. Theoretically this requires using a normal-form Hamiltonian that focuses on 5-wave resonances. The simplest arrangement is based on a triad of wavevectors K1+K2=K3 (satisfying specific ratios) along with their negatives, corresponding to a scenario of encountering wavepackets, amenable to experiments and numerical simulations. The normal-form equations for these encountering waves in resonance are shown to be non-integrable, but they admit an integrable reduction in a symmetric configuration. Numerical simulations of the governing equations in natural variables using pseudospectral methods require the inclusion of up to 6-wave interactions, which imposes a strong dealiasing cut-off in order to properly resolve the evolving waves. We study the resonance numerically by looking at a target mode in the base triad and showing that the energy transfer to this mode is more efficient when the system is close to satisfying the resonant conditions. We first look at encountering plane waves with base frequencies in the range 1.32–2.35 Hz and steepnesses below 0.1, and show that the time evolution of the target mode’s energy is dramatically changed at the resonance. We then look at a scenario that is closer to experiments: Encountering wavepackets in a 400-m long numerical tank, where the interaction time is reduced with respect to the plane-wave case but the resonance is still observed; by mimicking a probe measurement of surface elevation we obtain efficiencies of up to 10% in frequency space after including near-resonant contributions. Finally, we perform preliminary experiments of encountering wavepackets in a 35-m long tank, which seem to show that the resonance exists physically. The measured efficiencies via probe measurements of surface elevation are relatively small, indicating that a finer search is needed along with longer wave flumes with much larger amplitudes and lower frequency waves. A further analysis of phases generated from probe data via the analytic signal approach (using the Hilbert transform) shows a strong triad phase synchronisation at the resonance, thus providing independent experimental evidence of the resonance.

Interaction of surface waves with turbulence: direct numerical simulations of turbulent open-channel flow

1995 ◽  
Vol 286 ◽  
pp. 1-23 ◽  
Author(s):  
Vadim Borue ◽  
Steven A. Orszag ◽  
Ilya Staroselsky
Keyword(s):  
Free Surface ◽  
Numerical Simulations ◽  
Channel Flow ◽  
Gravity Waves ◽  
Open Channel ◽  
Open Channel Flow ◽  
Surface Region ◽  
Direct Numerical Simulations ◽  
Turbulence Production ◽  
Wind Sea

We report direct numerical simulations of incompressible unsteady open-channel flow. Two mechanisms of turbulence production are considered: shear at the bottom and externally imposed stress at the free surface. We concentrate upon the effects of mutual interaction of small-amplitude gravity waves with in-depth turbulence and statistical properties of the near-free-surface region. Extensions of our approach can be used to study turbulent mixing in the upper ocean and wind–sea interaction, and to provide diagnostics of bulk turbulence.

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.

Radiative damping of trapped gravity waves in the solar atmosphere

Solar Physics ◽  
1973 ◽  
Vol 30 (2) ◽  
pp. 319-325 ◽  
Author(s):  
Patricia André Clark ◽  
Alfred Clark
Keyword(s):  
Solar Atmosphere ◽  
Gravity Waves ◽  
Radiative Damping

Sensitivity of MCS Low-Frequency Gravity Waves to Microphysical Variations

2020 ◽  
Vol 77 (10) ◽  
pp. 3461-3477
Author(s):  
Rebecca D. Adams-Selin
Keyword(s):  
Numerical Simulations ◽  
Gravity Waves ◽  
Wave Motion ◽  
Low Frequency ◽  
Vertical Motion ◽  
Internal Variability ◽  
Initial Wave ◽  
Highly Sensitive ◽  
Heating Profiles ◽  
Melting Level

AbstractThe sensitivity of low-frequency gravity waves generated during the development and mature stages of an MCS to variations in the characteristics of the rimed ice parameterization were tested through idealized numerical simulations over a range of environment shears and instabilities. Latent cooling in the simulations with less dense, graupel-like rimed ice was more concentrated aloft near the melting level, while cooling in simulations with denser, hail-like rimed ice extended from the melting level to the surface. However, the cooling profiles still had significant internal variability across different environments and over each simulation’s duration. Initial wave production during the MCS developing stage was fairly similar in the hail and graupel simulations. During the mature stages, graupel simulations showed stronger perturbations in CAPE due to the cooling and associated wave vertical motion being farther aloft; hail simulations showed stronger perturbations in LFC due to cooling and wave vertical motion being concentrated at lower levels. The differences in the cooling profiles were not uniform enough to produce consistently different higher-order wave modes. However, the initiation of discrete cells ahead of the convective line was found to be highly sensitive to the nature of the prior destabilizing wave. Individual events of discrete propagation were suppressed in some of the graupel simulations due to the higher location of both peak cooling and vertical wave motion. Such results underscore the need to fully characterize MCS microphysical heating profiles and their low-frequency gravity waves to understand their structure and development.

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