On the period ratio P₁/2P₂ in the oscillations of coronal loops

McEwan, M.P. , Donnelly, G.R., Diaz, A.J. and Roberts, B. (2006) On the period ratio P₁/2P₂ in the oscillations of coronal loops. Astronomy and Astrophysics, 460(3), pp. 893-899. (doi: 10.1051/0004-6361:20065313)

Abstract

<p>Aims. With strong evidence of fast and slow magnetoacoustic modes arising in the solar atmosphere there is scope for improved determinations of coronal parameters through coronal seismology. Of particular interest is the ratio P₁/2P₂between the period P₁ of the fundamental mode and the period P₂ of its first harmonic; in an homogeneous medium this ratio is one, but in a more complex configuration it is shifted to lower values.</p> <p>Methods. We consider analytically the effects on the different magnetohydrodynamic modes of structuring and stratification, pointing out that transverse or longitudinal structuring or gravitational stratification modifies the ratio P₁/2P₂.</p> <p>Results. The deviations caused by gravity and structure are studied for the fast and slow modes. Structure along the loop is found to be the dominant effect.</p> <p>Conclusions. The departure of P₁/2P₂ from unity can be used as a seismological tool in the corona. We apply our technique to the observations by Verwichte et al. (2004), deducing the density scale height in a coronal loop.</p>

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: McEwan, Dr Michael
• Authors: McEwan, M.P., Donnelly, G.R., Diaz, A.J., and Roberts, B.
• College/School: University Services > Learning and Teaching Services Division; University Services > Student and Academic Services > Academic Services
• Journal Name: Astronomy and Astrophysics
• Publisher: EDP Sciences
• ISSN: 0004-6361
• ISSN (Online): 1432-0746
• Copyright Holders: Copyright © 2006 ESO
• First Published: First published in Astronomy & Astrophysics 460(3):763-770
• Publisher Policy: Reproduced with permission from Astronomy & Astrophysics, © ESO