Issue |
A&A
Volume 466, Number 2, May I 2007
|
|
---|---|---|
Page(s) | 691 - 696 | |
Section | The Sun | |
DOI | https://doi.org/10.1051/0004-6361:20066790 | |
Published online | 20 February 2007 |
The superrotation of solar supergranules
Laboratoire d'Astrophysique de l'Observatoire Midi-Pyrénées, Université Paul Sabatier, CNRS, 57 Avenue d'Azereix, BP 826, 65008 Tarbes Cedex, France e-mail: [meunier;roudier]@ast.obs-mip.fr
Received:
22
November
2006
Accepted:
19
January
2007
Context.Supergranules have long been believed to rotate faster than plasma and than magnetic structures. However, it has recently been shown that this could be due to a bias appearing when using Dopplergrams, which are strongly affected by projection effets.
Aims.Our purpose is to perform new measurements of supergranule angular velocities using a technique that would not be significantly influenced by projection effets.
Methods.We are therefore tracking horizontal divergence maps smoothed on the supergranular scale, either globally or on the scale of cells. Tracking the magnetic field using the same technique allows them to be used as a reference. Doppler tracking is performed for a direct comparison.
Results.We confirm that the tracking of Doppler features is not reliable when computing the dynamics on the supergranular scale. However, we find that divergence features are still rotating faster than the magnetic field, when using two independent time series.
Conclusions.We conclude that the long-standing puzzle of supergranular superrotation persists, and that interpreting it in terms of anchorage depth inside the convective zone may not be sufficient to explain it.
Key words: Sun: rotation / Sun: photosphere / Sun: general
© ESO, 2007
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.