Properties of horizontal flows inside and outside a solar pore

¹ Institute Laboratoire d'Astrophysique de Toulouse, Observatoire Midi-Pyrénées, 14 avenue E. Belin, 31400 Toulouse, France
² Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
³ Astronomical Institute, Academy of Sciences of the Czech Republic, 25165 Ondřejov, The Czech Republic

Corresponding author: Th. Roudier, roudier@obs-mip.fr

Received: 17 April 2002
Accepted: 16 August 2002

Abstract

Horizontal velocities and their temporal variations inside a large pore and in the surrounding granulation are studied from a 73 min sequence of white light frames, acquired at the Swedish Vacuum Solar Telescope (La Palma). The local correlation tracking technique with high spatial (0 31) and temporal (5 min) resolution was applied to binarized images, yielding 14 independent velocity maps. A ring of divergence centres around the pore was observed in all the maps. Motions directed into the pore, deposited by the divergence centres, continue also within the pore but with magnitudes smaller by factor of 2–3. A link between the variations of large velocity amplitudes around the pore and the brightness fluctuations of umbral dots is suggested. A phase delay between velocity and intensity changes at the periphery of the pore, probably related to the penetration of bright features inwards across the pore's border, was observed.