The Effect of Abnormal Granulation on Acoustic Wave Travel Times and Mode Frequencies
Abstract
Observations indicate that in plage areas (i.e. in active regions outside sunspots) acoustic waves travel faster than in the quiet Sun, leading to shortened travel times and higher p-mode frequencies. Coupled with the 11-year variation of solar activity, this may also explain the solar cycle variation of oscillation frequencies. While it is clear that the ultimate cause of any difference between the quiet Sun and plage is the presence of magnetic fields of order 100 G in the latter, the mechanism by which the magnetic field exerts its influence has not yet been conclusively identified. One possible such mechanism is suggested by the observation that granular motions in plage areas tend to be slightly "abnormal", dampened compared to the quiet Sun.
- Publication:
-
Solar Physics
- Pub Date:
- February 2007
- DOI:
- 10.1007/s11207-006-0180-8
- arXiv:
- arXiv:astro-ph/0702076
- Bibcode:
- 2007SoPh..240..197P
- Keywords:
-
- Sun: faculae;
- plages;
- Sun: granulation;
- Sun: helioseismology;
- Astrophysics
- E-Print:
- 18 pages, 5 figures. Solar Phys., in press