SOHO/CDS and Ground Based Observations of a Two-Ribbon Flare:Spatially Resolved Signatures of Chromospheric Evaporation |
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Ambretta Falchi Submitted: 2003-01-20 06:46
During a coordinated observing campaign (SOHO JOP 139), we obtained
simultaneous spectroheliograms of a solar active region in several
spectral lines, sampling levels from the chromosphere to the corona.
Ground based spectroheliograms were acquired at the Dunn Solar Tower
of NSO/Sacramento Peak in four chromospheric lines, while the Coronal
Diagnostic Spectrograph (CDS) aboard SOHO was used to obtain rasters
of the active region in transition region (TR) and coronal lines. Such
a complete dataset allowed us to compare the development of intensity
and velocity fields during a small two-ribbon flare in the whole
atmosphere. In particular, we obtained for the first time
quasi-simultaneous and spatially resolved observations of velocity
fields during the impulsive phase of a flare, both in chromosphere and
upper atmosphere. In this phase, strong downflows (up to 40 km
s-1) following the shape of the developing ribbons are measured
at chromospheric levels, while strong upward motions are instead
measured in TR (up to -100 km s-1) and coronal lines (-160 km
s-1). The spatial pattern of these velocities have a common area
about 10 arcsec wide. This is the first time that opposite directed
flows at different atmospheric levels are observed in the same spatial location during a flare. These signatures are highly suggestive of
the chromospheric evaporation scenario predicted in theoretical models
of flares.
Authors: Teriaca, L., Falchi, A., Cauzzi, G., Falciani, R., Smaldone, L.A. and Andretta, V.
Projects:
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Publication Status: Accepted by ApJ
Last Modified: 2003-01-20 06:46
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