Issue |
A&A
Volume 460, Number 3, December IV 2006
|
|
---|---|---|
Page(s) | 893 - 899 | |
Section | The Sun | |
DOI | https://doi.org/10.1051/0004-6361:20065313 | |
Published online | 15 September 2006 |
On the period ratio P
/2P
in the oscillations of coronal loops
School of Mathematics and Statistics, University of St Andrews, St Andrews, Fife KY169SS, Scotland e-mail: mike@mcs.st-and.ac.uk
Received:
29
March
2006
Accepted:
11
September
2006
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 between 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.
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 .
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.
Conclusions.The departure of 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.
Key words: Sun: oscillations / Sun: magnetic fields / Sun: corona
© ESO, 2006
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.