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Properties of $p$- and $f$-modes in hydromagnetic turbulence
- Source :
- Mon. Not. Roy. Astron. Soc. 447, 3708-3722 (2015)
- Publication Year :
- 2014
-
Abstract
- With the ultimate aim of using the fundamental or $f$-mode to study helioseismic aspects of turbulence-generated magnetic flux concentrations, we use randomly forced hydromagnetic simulations of a piecewise isothermal layer in two dimensions with reflecting boundaries at top and bottom. We compute numerically diagnostic wavenumber-frequency diagrams of the vertical velocity at the interface between the denser gas below and the less dense gas above. For an Alfv\'en-to-sound speed ratio of about 0.1, a 5% frequency increase of the $f$-mode can be measured when $k_xH_{\rm p}=3$-$4$, where $k_x$ is the horizontal wavenumber and $H_{\rm p}$ is the pressure scale height at the surface. Since the solar radius is about 2000 times larger than $H_{\rm p}$, the corresponding spherical harmonic degree would be 6000-8000. For weaker fields, a $k_x$-dependent frequency decrease by the turbulent motions becomes dominant. For vertical magnetic fields, the frequency is enhanced for $k_xH_{\rm p}\approx4$, but decreased relative to its nonmagnetic value for $k_xH_{\rm p}\approx9$.<br />Comment: 17 pages, 22 figures, Version accepted in MNRAS
- Subjects :
- Astrophysics - Solar and Stellar Astrophysics
Subjects
Details
- Database :
- arXiv
- Journal :
- Mon. Not. Roy. Astron. Soc. 447, 3708-3722 (2015)
- Publication Type :
- Report
- Accession number :
- edsarx.1404.3246
- Document Type :
- Working Paper
- Full Text :
- https://doi.org/10.1093/mnras/stu2540