Volume 555, July 2013
|Number of page(s)||9|
|Published online||04 July 2013|
Cross-sectional area and intensity variations of sausage modes⋆
Centre for mathematical Plasma Astrophysics, Mathematics
KU Leuven, Celestijnenlaan 200B bus
Accepted: 2 May 2013
Context. The observations obtained using the Rapid Oscillations in the Solar Atmosphere instrument (ROSA) show variations in both cross-sectional area and intensity for magnetic pores in the photosphere.
Aims. We study the phase behaviour between cross-sectional area and intensity variations for sausage modes in a photospheric context. We aim to determine the wave mode by looking at the phase difference between the cross-sectional area and intensity variations.
Methods. We used a straight cylinder as a model for the flux tube. The plasma is uniform both inside and outside the flux tube with a possible jump in the equilibrium values at the boundary, the magnetic field is directed along the flux tube. We derived analytic expressions for the cross-sectional area variation and the total intensity variation. Using these analytic expressions, we calculated the phase differences between the cross-sectional area and the intensity variations. These phase differences were then used to identify the wave mode.
Results. We found that for slow sausage modes the cross-sectional area and intensity variations are always in phase, while for fast sausage modes the variations are in antiphase.
Key words: magnetohydrodynamics (MHD) / methods: analytical / Sun: photosphere / Sun: oscillations
Appendix A is available in electronic form at http://www.aanda.org
© ESO, 2013
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