Large-scale horizontal flows in the solar photosphere

III. Effects on filament destabilization

¹ Laboratoire d'Astrophysique de l'Observatoire Midi-Pyrénées, Université Paul Sabatier Toulouse III, CNRS, 57 Avenue d'Azeirex, 65000 Tarbes, France e-mail: roudier@ast.obs-mip.fr
² Astronomical Institute, Academy of Sciences of the Czech Republic, Fričova 298, 25165 Ondřejov, Czech Republic
³ Astronomical Institute, Charles University, V Holešovičkách 2, 18200 Prague, Czech Republic
⁴ Laboratoire d'Astrophysique, Observatoire de Grenoble, Université Joseph Fourier, BP 53, 38041 Grenoble Cedex 9, France
⁵ National Solar Observatory, Sacramento Peak, Sunspot, NM 88349, USA
⁶ LESIA, Observatoire de Paris, Section de Meudon, 92195 Meudon, France
⁷ LERMA, Observatoire de Paris, Section de Meudon, 92195 Meudon, France

Received: 30 May 2007
Accepted: 15 October 2007

Abstract

Aims.We study the influence of large-scale photospheric motions on the destabilization of an eruptive filament, observed on October 6, 7, and 8, 2004, as part of an international observing campaign (JOP 178).

Methods.Large-scale horizontal flows were investigated from a series of MDI full-disc Dopplergrams and magnetograms. From the Dopplergrams, we tracked supergranular flow patterns using the local correlation tracking (LCT) technique. We used both LCT and manual tracking of isolated magnetic elements to obtain horizontal velocities from magnetograms.

Results.We find that the measured flow fields obtained by the different methods are well-correlated on large scales. The topology of the flow field changed significantly during the filament eruptive phase, suggesting a possible coupling between the surface flow field and the coronal magnetic field. We measured an increase in the shear below the point where the eruption starts and a decrease in shear after the eruption. We find a pattern in the large-scale horizontal flows at the solar surface that interact with differential rotation.

Conclusions.We conclude that there is probably a link between changes in surface flow and the disappearance of the eruptive filament.