Redshift in sunspot plumes Original Research Article

The non-uniform spatial distributions of emission and wavelength shift in ten EUV lines formed in the chromosphere, transition region and corona above 50 sunspots are investigated, based on observations with the Coronal Diagnostic Spectrometer on the Solar and Heliospheric Observatory. The sunspot plumes are the most prominent features in the transition region line emissions. We find that almost all sunspots show a plume when one magnetic polarity dominates the region out to a distance of 50″ from the sunspot. Both the enhanced emission and the redshift in sunspot plumes increase with the line formation temperature, T, reach a maximum close to log T = 5.5 and cease to exist close to log T = 6.0. The mass flow in the corona is too small to explain the observed redshift in the transition region. We present a working hypothesis where gas at transition region temperatures moves in flow channels from the surroundings into the sunspot.