The Energy Flux of Internal Gravity Waves in the Lower Solar Atmosphere

2008 ◽  
Vol 681 (2) ◽  
pp. L125-L128 ◽  
Author(s):  
Thomas Straus ◽  
Bernhard Fleck ◽  
Stuart M. Jefferies ◽  
Gianna Cauzzi ◽  
Scott W. McIntosh ◽  
...  
Keyword(s):  
Solar Atmosphere ◽  
Energy Flux ◽  
Gravity Waves ◽  
Internal Gravity Waves ◽  
Lower Solar Atmosphere

scholarly journals Synthetic observations of internal gravity waves in the solar atmosphere

2020 ◽  
Vol 633 ◽  
pp. A140
Author(s):  
G. Vigeesh ◽  
M. Roth
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Flux Density ◽  
Solar Atmosphere ◽  
Energy Flux ◽  
Gravity Waves ◽  
Internal Gravity Waves ◽  
Spectral Lines ◽  
Magnetic Flux Density ◽  
Phase Differences

Aims. We study the properties of internal gravity waves (IGWs) detected in synthetic observations that are obtained from realistic numerical simulation of the solar atmosphere. Methods. We used four different simulations of the solar magneto-convection performed using the CO5BOLD code. A magnetic-field-free model and three magnetic models were simulated. The latter three models start with an initial vertical, homogeneous field of 10, 50, and 100 G magnetic flux density, representing different regions of the quiet solar surface. We used the NICOLE code to compute synthetic spectral maps from all the simulated models for the two magnetically insensitive neutral iron lines Fe I λλ 5434 Å and 5576 Å. We carried out Fourier analyses of the intensity and Doppler velocities to derive the power, phase, and coherence in the kh − ω diagnostic diagram to study the properties of internal gravity waves. Results. We find the signatures of the internal gravity waves in the synthetic spectra to be consistent with observations of the real Sun. The effect of magnetic field on the wave spectra is not as clearly discernible in synthetic observations as in the case of numerical simulations. The phase differences obtained using the spectral lines are significantly different from the phase differences in the simulation. The phase coherency between two atmospheric layers in the gravity wave regime is height dependent and is seen to decrease with the travel distance between the observed layers. In the studied models, the lower atmosphere shows a phase coherency above the significance level for a height separation of ∼400 km, while in the chromospheric layers it reduces to ∼100–200 km depending on the average magnetic flux density. Conclusion. We conclude that the energy flux of IGWs determined from the phase difference analysis may be overestimated by an order of magnitude. Spectral lines that are weak and less temperature sensitive may be better suited to detecting internal waves and accurately determining their energy flux in the solar atmosphere.

scholarly journals On the influence of magnetic topology on the propagation of internal gravity waves in the solar atmosphere

2020 ◽  
Vol 379 (2190) ◽  
pp. 20200177 ◽  
Author(s):  
G. Vigeesh ◽  
M. Roth ◽  
O. Steiner ◽  
B. Fleck
Keyword(s):  
Magnetic Field ◽  
Flux Density ◽  
Solar Atmosphere ◽  
Gravity Waves ◽  
Internal Gravity Waves ◽  
Magnetic Flux Density ◽  
Horizontal Field ◽  
Crucial Difference ◽  
Propagation Properties ◽  
Lower Solar Atmosphere

The solar surface is a continuous source of internal gravity waves (IGWs). IGWs are believed to supply the bulk of the wave energy for the lower solar atmosphere, but their existence and role for the energy balance of the upper layers is still unclear, largely due to the lack of knowledge about the influence of the Sun’s magnetic fields on their propagation. In this work, we look at naturally excited IGWs in realistic models of the solar atmosphere and study the effect of different magnetic field topographies on their propagation. We carry out radiation-magnetohydrodynamic simulations of a magnetic field free and two magnetic models—one with an initial, homogeneous, vertical field of 100 G magnetic flux density and one with an initial horizontal field of 100 G flux density. The propagation properties of IGWs are studied by examining the phase-difference and coherence spectra in the k h  −  ω diagnostic diagram. We find that IGWs in the upper solar atmosphere show upward propagation in the model with predominantly horizontal field similar to the model without magnetic field. In contrast to that the model with predominantly vertical fields show downward propagation. This crucial difference in the propagation direction is also revealed in the difference in energy transported by waves for heights below 0.8 Mm. Higher up, the propagation properties show a peculiar behaviour, which require further study. Our analysis suggests that IGWs may play a significant role in the heating of the chromospheric layers of the internetwork region where horizontal fields are thought to be prevalent. This article is part of the Theo Murphy meeting issue ‘High-resolution wave dynamics in the lower solar atmosphere’.

scholarly journals A new method for detecting solar atmospheric gravity waves

2020 ◽  
Vol 379 (2190) ◽  
pp. 20200178 ◽  
Author(s):  
Daniele Calchetti ◽  
Stuart M. Jefferies ◽  
Bernhard Fleck ◽  
Francesco Berrilli ◽  
Dmitriy V. Shcherbik
Keyword(s):  
Solar Atmosphere ◽  
Gravity Waves ◽  
Three Dimensional ◽  
Internal Gravity Waves ◽  
New Method ◽  
Ample Evidence ◽  
New Approach ◽  
Wave Dynamics ◽  
Atmospheric Gravity ◽  
Lower Solar Atmosphere

Internal gravity waves have been observed in the Earth’s atmosphere and oceans, on Mars and Jupiter, and in the Sun’s atmosphere. Despite ample evidence for the existence of propagating gravity waves in the Sun’s atmosphere, we still do not have a full understanding of their characteristics and overall role for the dynamics and energetics of the solar atmosphere. Here, we present a new approach to study the propagation of gravity waves in the solar atmosphere. It is based on calculating the three-dimensional cross-correlation function between the vertical velocities measured at different heights. We apply this new method to a time series of co-spatial and co-temporal Doppler images obtained by SOHO/MDI and Hinode/SOT as well as to simulations of upward propagating gravity wave-packets. We show some preliminary results and outline future developments. This article is part of the Theo Murphy meeting issue ‘High-resolution wave dynamics in the lower solar atmosphere’.

Estimation of the Energy Flux of Torsional Alfvén Waves in the Lower Solar Atmosphere Based on Measurements of the Doppler Velocities

2021 ◽  
Vol 61 (7) ◽  
pp. 1035-1037
Author(s):  
Yu. T. Tsap ◽  
A. V. Stepanov ◽  
Yu. G. Kopylova ◽  
O. V. Khaneychuk ◽  
T. B. Goldvarg
Keyword(s):  
Solar Atmosphere ◽  
Energy Flux ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
Lower Solar Atmosphere

scholarly journals Internal Gravity Waves in the Magnetized Solar Atmosphere. II. Energy Transport

2019 ◽  
Vol 872 (2) ◽  
pp. 166 ◽  
Author(s):  
G. Vigeesh ◽  
M. Roth ◽  
O. Steiner ◽  
J. Jackiewicz
Keyword(s):  
Solar Atmosphere ◽  
Gravity Waves ◽  
Energy Transport ◽  
Internal Gravity Waves

scholarly journals Resolving the horizontal direction of internal tide generation

2019 ◽  
Vol 864 ◽  
pp. 381-407 ◽  
Author(s):  
Friederike Pollmann ◽  
Jonas Nycander ◽  
Carsten Eden ◽  
Dirk Olbers
Keyword(s):  
Internal Wave ◽  
Energy Flux ◽  
Gravity Waves ◽  
Large Scale ◽  
Bottom Topography ◽  
Internal Gravity Waves ◽  
Global Ocean ◽  
Wide Field ◽  
Practical Advantage ◽  
Analytical Approaches

The mixing induced by breaking internal gravity waves is an important contributor to the ocean’s energy budget, shaping, inter alia, nutrient supply, water mass transformation and the large-scale overturning circulation. Much of the energy input into the internal wave field is supplied by the conversion of barotropic tides at rough bottom topography, which hence needs to be described realistically in internal gravity wave models and mixing parametrisations based thereon. A new semi-analytical method to describe this internal wave forcing, calculating not only the total conversion but also the direction of this energy flux, is presented. It is based on linear theory for variable stratification and finite depth, that is, it computes the energy flux into the different vertical modes for two-dimensional, subcritical, small-amplitude topography and small tidal excursion. A practical advantage over earlier semi-analytical approaches is that the new one gives a positive definite conversion field. Sensitivity studies using both idealised and realistic topography allow the identification of suitable numerical parameter settings and corroborate the accuracy of the method. This motivates the application to the global ocean in order to better account for the geographical distribution of diapycnal mixing induced by low-mode internal gravity waves, which can propagate over large distances before breaking. The first results highlight the significant differences of energy flux magnitudes with direction, confirming the relevance of this more detailed approach for energetically consistent mixing parametrisations in ocean models. The method used here should be applicable to any physical system that is described by the standard wave equation with a very wide field of sources.

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