Issue |
A&A
Volume 431, Number 1, February III 2005
|
|
---|---|---|
Page(s) | 339 - 344 | |
Section | The Sun | |
DOI | https://doi.org/10.1051/0004-6361:20041299 | |
Published online | 02 February 2005 |
Explosive events in the solar atmosphere seen in extreme-ultraviolet emission lines
1
Instituto Nacional de Astrofisica, Optica y Electrónica, Puebla, Mexico e-mail: mend@inaoep.mx
2
Max-Planck-Institut für Aeronomie, 37191 Katlenburg-Lindau, Germany
Received:
15
May
2004
Accepted:
5
October
2004
We present observations of explosive events (EEs) in the solar atmosphere
obtained with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER)
spectrometer on the Solar and Heliospheric Observatory (SOHO) in the wavelength
range from about 750 Å to 790 Å.
Prominent spectral lines in this range are emitted by ions which have
temperatures of maximum ionic abundances between 5 K and
K in ionization equilibrium, and are therefore expected
to be formed in the transition region (TR) and in the low corona. The aim of this work is to
investigate whether the EEs originate in a limited
range of temperatures or in a wide interval.
We analyzed the behaviour of several emission lines during 114 EEs. In many events,
the radiance increased first in lines with formation temperatures near
5 K.
A number of events produced profiles that clearly revealed blue and red
components, in addition to the central line.
In general, both the radiance and the line-of-sight (LOS) velocity of the blue
component are larger than those of the red one.
From an inspection of the profiles that did not show all three spectral
components, we found, in all the cases, that the lowest temperature line showed
a red shift whereas the highest temperature was characterized by a blue shift.
The inverse situation was not observed. We interpret these results as an indication that
most of the EEs originate at
intermediate temperatures of the TR as fast reconnection jets.
Key words: Sun: transition region / Sun: activity / Sun: UV radiation / Sun: atmosphere
© ESO, 2005
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