Spatially resolved signatures of chromospheric evaporation during a small two-ribbon flare
Abstract
Ground based spectroheliograms of a solar active region were acquired in four chromospheric lines simultaneously with rasters in transition region (TR) and coronal lines obtained with the Coronal Diagnostic Spectrograph (CDS) aboard SOHO. Such a complete dataset allows us to study the development of intensity and velocity fields during a small two-ribbon flare in the whole atmosphere. In particular, we obtain 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 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.
- Publication:
-
Memorie della Societa Astronomica Italiana
- Pub Date:
- 2003
- Bibcode:
- 2003MmSAI..74..635T
- Keywords:
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- Solar activity;
- Flares;
- Atmospheric motions