Summary: Astronomy & Astrophysics manuscript no. corholeb1 c ESO 2009
June 6, 2009
Coronal hole boundaries evolution at small scales: I. EIT 195 Å and
TRACE 171 Å view
M. S. Madjarska1,2 and T. Wiegelmann1
Max-Planck-Institut f¨ur Sonnensystemforschung, Max-Planck-Str. 2, 37191 Katlenburg-Lindau, Germany
Armagh Observatory, College Hill, Armagh BT61 9DG, N. Ireland
Received date, accepted date
Aims. We aim at studying the small-scale evolution at the boundaries of an equatorial coronal hole connected with a channel of open
magnetic flux with the polar region and an `isolated' one in the extreme-ultraviolet spectral range. We intend to determine the spatial
and temporal scale of these changes.
Methods. Imager data from TRACE in the Fe IX/X 171 Å passband and EIT on-board Solar and Heliospheric Observatory in the
Fe XII 195 Å passband were analysed.
Results. We found that small-scale loops known as bright points play an essential role in coronal holes boundaries evolution at small
scales. Their emergence and disappearance continuously expand or contract coronal holes. The changes appear to be random on a
time scale comparable with the lifetime of the loops seen at these temperatures. No signature was found for a major energy release
during the evolution of the loops.