Astronomy & Astrophysics

Free access article

A&A 481, L49-L52 (2008)
DOI: 10.1051/0004-6361:20079087

Letter

Flows in active region loops observed by Hinode EIS

G. Del Zanna

Mullard Space Science Laboratory, University College London, Holmbury St. Mary Dorking RH5 6NT, UK DAMTP, Centre for Mathematical Sciences, Wilberforce road Cambridge CB3 0WA, UK
e-mail: GDelZanna@spd.aas.org

(Received 16 November 2007 / Accepted 14 January 2008)

Abstract
We aim to investigate the overall characteristics of coronal active region loops and their evolution. The Hinode database was searched for observations of active regions as they crossed the Sun centre. NOAA 10926 was selected. The morphology of this young active region did not significantly change over the course of a few days. Persistent redshifts, stronger in cooler lines (about 5-10 km s^-1 in $\ion{xii}$ and 20-30 km s^-1 in $\ion{viii}$ ), were observed in most loop structures with the EUV Imaging Spectrometer. Persistent blueshifts, stronger in the hotter lines (typically 5-20 km s^-1 in $\ion{xii}$ and 10-30 km s^-1 in $\ion{xv}$ ), were present in areas of weak emission, in a sharp boundary between the low-lying "hot" 3 MK loops and the higher "cooler" 1 MK loops.

Key words: Sun: corona -- Sun: UV radiation -- Sun: activity