The statistical distribution of the magnetic-field strength in G-band bright points
Abstract
Context. G-band bright points are small-sized features characterized by high photometric contrast. Theoretical investigations indicate that these features have associated magnetic-field strengths of 1 to 2 kG. Results from observations, however, lead to contradictory results, indicating magnetic fields of only kG strength in some and including hG strengths in others.
Aims: To understand the differences between measurements reported in the literature, and to reconcile them with results from theory, we analyzed the distribution of the magnetic-field strength of G-band bright features identified in synthetic images of the solar photosphere and its sensitivity to observational and methodological effects.
Methods: We investigated the dependence of magnetic-field strength distributions of G-band bright points identified in 3D magnetohydrodynamic simulations on feature selection method, data sampling, alignment, and spatial resolution.
Results: The distribution of the magnetic-field strength of G-band bright features shows two peaks, one at about 1.5 kG and one below 1 hG. The former corresponds to magnetic features, the second mostly to bright granules. Peaks at several hG are obtained only on spatially degraded or misaligned data.
Conclusions: Simulations show that magnetic G-band bright points have typically associated field strengths of a few kG. Field strengths in the hG range can result from observational effects, which explains the discrepancies presented in the literature. Our results also indicate that results from spectro-polarimetric inversions with an imposed unit filling-factor should be employed with great caution.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- February 2014
- DOI:
- 10.1051/0004-6361/201322909
- arXiv:
- arXiv:1312.2611
- Bibcode:
- 2014A&A...562L...1C
- Keywords:
-
- magnetohydrodynamics (MHD);
- magnetic fields;
- Sun: photosphere;
- Sun: magnetic fields;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- doi:10.1051/0004-6361/201322909