Bremen 2000 – wissenschaftliches Programm

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EP: Extraterrestrische Physik

EP 3: Sonne und Heliosph
äre I

EP 3.4: Vortrag

Dienstag, 21. März 2000, 16:30–16:45, H1

SOHO/CDS Observations of Active Region NOAA-8208 — •Gerhard Rank, Anja Czaykowska, Gabriela Bagalá und Gerhard Haerendel — Max-Planck-Institut für extraterrestrische Physik

Solar active region NOAA-8208 was observed on 28 April 1998 with the Coronal Diagnostic Spectrometer (CDS) onboard SOHO. We have studied two aspects of the transition region plasma at temperatures of about 10000 K. We investigate spatial variations of elemental abundance enhancements due to the first ionization potential (FIP) effect. The variations were determined by mapping the abundance ratio of 5-times ionized Neon (high FIP element) and Magnesium (low FIP element). We find local variations of this ratio within the active region which are related to magnetic loop structures. Additionally, we study the Doppler shifts of EUV lines. It is known that transition region lines show a prevailing redshift, and that this redshift correlates with the intensity emitted by the plasma. Here we find for the He I 584 Angstrom line formed in the upper chromosphere that the variation of redshift with intensity is stronger in the quiet Sun regions than in the active region.