Network oscillations at the boundary of an equatorial coronal hole
Abstract
Aims: We investigate intensity oscillations observed simultaneously in the quiet chromosphere and in the corona, above an enhanced network area at the boundary of an equatorial coronal hole.
Methods: A Fourier analysis is applied to a sequence of images observed in the 171 Å and 1600 Å passbands of TRACE. Four interesting features above the magnetic network are further investigated by using a wavelet analysis.
Results: Our results reveal that, in both the 171 Å and 1600 Å passbands, oscillations above the magnetic network show a lack of power at high frequencies (5.0-8.3 mHz), and a significant power at low (1.3-2.0 mHz) and intermediate frequencies (2.6-4.0 mHz). The global 5-min oscillation is clearly present in the 4 analyzed features when seen in the 1600 Å passband, and is also found with enhanced power in feature 1 (leg of a large coronal loop) and feature 2 (legs of a coronal bright point loop) when seen in the 171 Å passband. Two features above an enhanced network element (feature 3 and feature 4) show repeated propagating behaviors with a dominant period of 10 min and 5 min, respectively.
Conclusions: We suggest these oscillations are likely to be slow magneto-acoustic waves propagating along inclined magnetic field lines, from the lower solar atmosphere into the corona. The energy flux carried by these waves is estimated of the order of 40~erg~ cm-2~s-1 for the 171 Å passband and is far lower than the energy required to heat the quiet corona. For the 1600 Å passband, the energy flux is about 1.4×10^6~erg~ cm-2~s-1, which is about one third of the required energy budget for the chromosphere.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- September 2008
- DOI:
- 10.1051/0004-6361:200810124
- arXiv:
- arXiv:0907.0818
- Bibcode:
- 2008A&A...488..331T
- Keywords:
-
- Sun: oscillations;
- Sun: corona;
- Sun: chromosphere;
- Sun: UV radiation;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 7 pages, 8 figures