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: http://star.arm.ac.uk/annrep/annrep2003/node50.html
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Ignacio Ugarte Urra's PhD thesis topic is the investigation of coronal
bright points. In his first paper (in collaboration with Gerry Doyle and
Maria Madjarska) he investigated 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 observations. The data were obtained with
various instruments on-board SoHO, including the SUMER spectrograph in the
transition region line SVI 933.40Å, CDS in the HeI 584.33Å, OV 629.73Å and MgIX 368.0Å 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 hours.
Furthermore, the bright point only became visible at coronal temperatures
when the two converging opposite magnetic polarities were
7000km 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 small-scale
(
6arcsec) transient brightenings within the bright point with a
periodicity of
6 minutes. The Doppler shift in the bright point
was found to be in the range of -10 to 10km s-1 although it is
dominated by a red-shifted emission which is associated with regions
characterized by stronger `quiet' Sun photospheric magnetic flux.
Small-scale brightenings within the bright point show velocity variations
in the range 3-6km s-1. In general the bright point has a radiance
4 times higher than that of the network. No relation was found
between the bright point and the UV bi-directional jet phenomena.