Large-scale photospheric dynamics below coronal holes

Free access article

Issue		A&A Volume 443, Number 1, November III 2005


Page(s)		309 - 317
Section		The Sun
DOI		http://dx.doi.org/10.1051/0004-6361:20053249

A&A 443, 309-317 (2005)
DOI: 10.1051/0004-6361:20053249

Large-scale photospheric dynamics below coronal holes

N. Meunier

Laboratoire d'Astrophysique de l'Observatoire Midi-Pyrénées, 57 avenue d'Azereix, BP 826, 65008 Tarbes Cedex, France
e-mail: meunier@bagn.obs-mip.fr

(Received 15 April 2005 / Accepted 11 July 2005)

Abstract
A large data set of MDI magnetograms is studied to analyze the global dynamics of magnetic structures from network to active regions inside and outside coronal holes. We find a weaker meridional circulation at almost all latitudes, as well as a more differential rotation of the photospheric magnetic structures below high-latitude coronal holes. Stronger asymmetries in the dynamics are observed in coronal holes at high latitude compared to outside coronal holes. The variation in the dynamics is also studied as a function of the coronal hole size as well as its variation with time and with magnetic field. The smaller velocity dispersion obtained in coronal holes when using a cross-correlation technique shows that the large-scale circulation may be inhibited inside coronal holes compared to outside. However, there is an indication of a larger diffusion of magnetic features within coronal holes than outside.

Key words: Sun: magnetic fields -- Sun: photosphere -- Sun: activity -- Sun: corona

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