Current Science at NOAO
Solar Infrared Spectroheliograms
Alan Clark and Marcel Bergman,University of Calgary;
Doug Rabin and Claude Plymate,NSO/National Science Foundation
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Image
at "moustache" peak intensity. |
June, 1999 | Alan Clark and Marcel Bergman (University of Calgary), and
Doug Rabin and Claude Plymate (NSO) used the Near Infra-red
Imaging Camera at the McMath-Pierce Telescope to image an
active region on the Sun in the light of an infrared
hydrogen line for the first time. These results are part
of a broader infrared spectroscopic imaging program
to explore the distribution across active regions and
the limb of many metal and molecular lines in order to
develop new diagnostic tests for atmospheric models of both
quiet and active regions of the Sun.
The active region NOAA 8350 was observed during a period of
excellent seeing on 8 October 1998, at a time when a bright
Ellerman bomb appeared on a light bridge crossing the main sunspot.
Images of small, bright Ellerman bombs on the fringe of the
penumbra are about 1 arcsec in diameter, almost matching the
limiting resolution of the telescope at these IR wavelengths.
These features show the characteristic "moustache" spectral
signature for spectral lines. The most interesting feature,
a bright Ellerman bomb, can be seen on the light bridge which
crosses the sunspot. The spectral frame centered on this feature,
which is crossed by several N2O absorption lines from the Earth's
atmosphere, clearly shows the moustache emission extending over
most of the 3 cm-1 spectral range. A spectroheliogram at a
wavelength near the peak of the emission clearly shows the
intense brightness as well as the structure of the transient
event, while a spectroheliogram centered on Br-alpha shows
no brightening, as expected. The matching CaII K image also
shows this bright feature.
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Image at Br-alpha Line Center. |
The appearance of the sunspot in Br-alpha is interesting
in its own right. The dark umbra is surrounded by a bright
penumbra, which itself is surrounded by plage regions which
appear dark against the quiet photosphere. This behavior
has been seen in subsequent observations of other sunspots.
For more information see:
NOAO Newsletter
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