The Mg/Ne abundance ratio in a recently emerged flux region observed by CDS
Abstract
Evidence for the existence of the FIP-effect in the transition region is presented here based on recent observations from the Coronal Diagnostic Spectrometer (CDS) on-board the Solar and Heliospheric Observatory (SOHO). Observations of an emerging flux region in lines of Mgv-vii and Nevi-vii reveal differences in the relative Mg/Ne abundance of a factor of 9.2 between two transition region brightenings separated by less than 1 arc min on the Sun. The lower abundance ratio is approximately equal to the photospheric Mg/Ne value and is associated with a small loop-like feature in the central, hottest part of the active region. The higher abundance ratio is found in spike-like structures at the edge of the active region. A density diagnostic of Oiv is used to derive an electron number density of 1011.3 cm-3 for the low Mg/Ne brightening, while a Mgvii diagnostic gives a density of 109.2 cm for the high Mg/Ne brightening.
- Publication:
-
Solar Physics
- Pub Date:
- October 1997
- DOI:
- 10.1023/A:1004936106427
- Bibcode:
- 1997SoPh..175..523Y
- Keywords:
-
- Active Region;
- High Abundance;
- Transition Region;
- Lower Abundance;
- Recent Observation