Physics
Scientific paper
Sep 1999
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999aspc..184..266b&link_type=abstract
Third Advances in Solar Physics Euroconference: Magnetic Fields and Oscillations, ASP Conference Series vol.184, p. 266-270. Eds
Physics
Sun: Corona, Sun: Transition Region, Sun: Uv Radiation, Sunspots
Scientific paper
The spatial distributions of line emission and line-of-sight velocity in seventeen different sunspot regions are studied, based on observations with the Coronal Diagnostic Spectrometer - CDS on SOHO. Ten EUV emission lines, formed in the chromosphere, transition region, and corona are observed. Enhanced EUV line emissions in the transition region are distributed non-uniformly over the active regions and are located both inside and outside sunspots. Most sunspot regions show strongly enhanced transition region line emission above the spot, i.e. sunspot plumes are reinvented. From wavelength shifts we derive the line-of-sight velocity, relative to the average velocity in the rastered area, 120" x 120". In sunspot plumes we find that the motion is directed away from the observer and increases with increasing line formation temperature, T, reaches a maximum up to 40 km s-1 close to log T ≅ 5.5, then decreases abruptly. The spatial extent of both emission features and flow regions increase with increasing temperature within the transition region. The observations show a marked difference between the transition region and the low corona, both regarding the spatial distributions of line emission and line-of-sight velocity.
Brekke Paal
Brynildsen Nils
Haugan S. V. H.
Kjeldseth-Moe Olav
Maltby Per
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