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Astronomy & Astrophysics manuscript no. (will be inserted by hand later)

Summary: Astronomy & Astrophysics manuscript no.
(will be inserted by hand later)
An EUV Bright Point as seen by SUMER, CDS, MDI and EIT
on­board SoHO
M.S. Madjarska 1 , J.G. Doyle 1 , L. Teriaca 2 , and D. Banerjee 3
1 Armagh Observatory, College Hill, Armagh BT61 9DG, N. Ireland
2 Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
3 Centre for Plasma Astrophysics, Katholieke Universiteit Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium
15 November 2002
Abstract. This paper presents the formation, evolution and decay of a coronal bright point via a spectroscopic analysis of its
transition region counterpart and the evolution of the underlying magnetic bipole during 3 days of almost continuous observa­
tions. The data were obtained with various instruments on­board SoHO, including the SUMER spectrograph in the transition
region line S ## 933.40 Ċ, CDS in the He # 584.33, O # 629.73 and Mg ## 368.06 Ċ lines, plus MDI and EIT. The existence of the
coronal feature is strongly correlated with the evolution of the underlying bipolar region. The lifetime of the bright point from
the moment when it was first visible in the EIT images until its complete disappearance was # 18 hrs. Furthermore, the bright
point only became visible at coronal temperatures when the two converging opposite magnetic polarities were # 7 000 km
apart. As far as the temporal coverage of the data permits, we found that the bright point disappeared at coronal temperatures
after a full cancellation of one of the magnetic polarities. The spectroscopic analysis reveals the presence of small­scale (# 6 ## )
transient brightenings within the bright point with a periodicity of # 6 min. The Doppler shift in the bright point was found to
be in the range of -10 to 10 km s -1 although it is dominated by a red­shifted emission which is associated with regions char­


Source: Armagh Observatory


Collections: Physics