A comprehensive study of internal gravity waves in magnetized solar atmosphere using numerical simulations
Final Report Abstract
As part of this project, we successfully carried out a comprehensive study of the role of internal gravity waves in the solar atmosphere. We were able to construct several magneto-convection simulation models of the solar atmosphere with varying magnetic field properties and study the generation and propagation of these waves. We found that these waves are influenced by the presence of the magnetic field in the atmosphere depending on the atmospheric layer in which they propagate. We find that the average magnetic flux density and orientation of the magnetic field has a significant impact on these waves in higher layers of the atmosphere, in contrast to near-surface layers where they are unaffected by the magnetic field. In terms of their role in the energy transport, we find that these waves may not be as important as earlier thought, both in terms of their direct or indirect contribution to the energy budget of the upper atmosphere. Within the limitation of the current study, we can only confirm that this results are mainly valid for the network-like regions of the solar atmosphere where the magnetic fields are predominantly vertical. However, during the course of the project we also found that IGWs in the presence of predominantly horizontal fields, like internetwork regions, show upward propagation for IGWs (downward phases) even in low-β plasma (magnetic-field dominated layers), indicating that these waves may still be important for chromospheric layers. This later study is currently being explored as an outcome of the current work. We computed synthetic spectral maps from our models and carried out Fourier analyses of the intensity and Doppler velocities to study the properties of internal gravity waves to directly compare them with observations of the real Sun. By comparing energy flux directly obtained from the simulation with that determined from the spectral lines, we come to the conclusion that the specific choice of spectral lines plays an important role; the types of lines needed for such an analysis tend to smear out the velocity field depending on the width of the line-formation region and their spatial separation, resulting in significantly smaller phase differences which can lead to overestimation of the energy flux of IGWs by an order of magnitude. Our understanding is that lines that are temperature insensitive and non-magnetic with narrow line-formation ranges may be preferable for detecting and studying internal waves in the solar atmosphere.
Publications
- On the effect of vorticity on the propagation of internal gravity waves, 2017, MSAIS, 88, 54
Vigeesh, G. and Steiner, O. and Calvo, F. and Roth, M.
- Internal Gravity Waves in the Magnetized Solar Atmosphere. II. Energy Transport, 2019, 872, 166
Vigeesh, G. and Roth, M. and Steiner, O. and Jackiewicz, J.
(See online at https://doi.org/10.3847/1538-4357/ab020c) - Synthetic observations of internal gravity waves in the solar atmosphere, 2019, A&A
Vigeesh, G. and Roth, M.
(See online at https://doi.org/10.1051/0004-6361/201936846)
