Issue |
A&A
Volume 430, Number 2, February I 2005
|
|
---|---|---|
Page(s) | L29 - L32 | |
Section | Letters | |
DOI | https://doi.org/10.1051/0004-6361:200400125 | |
Published online | 20 January 2005 |
Letter to the Editor
The effect of metastable level populations on the ionization fraction of Li-like ions
1
Armagh Observatory, College Hill, Armagh, BT61 9DG, N. Ireland e-mail: jgd@arm.ac.uk
2
Department of Physics, University of Strathclyde, Glasgow, Scotland
Received:
11
November
2004
Accepted:
11
December
2004
Lines from Li-like ions have been known to produce theoretical
intensities under-estimated compared to lines of a similar formation
temperature. Here we investigate this anomalous behaviour whereby the ionization fractions
are calculated using the ADAS code considering the electron density dependence
of dielectronic recombination coupled with collisional ionization from metastable
levels. For the lines investigated, the line contribution functions show a clear
dependence with increasing electron density. For example, C iv 1548 Å
shows over a factor of three enhancement for . The increase in the higher temperature lines is lower, but are still in the range of 30 to 60%.
Furthermore, all the lines have their peak contribution shifted to lower temperature. Calculating
the total radiative power output at an electron density of
, we
find that the difference in the transition region is 10–15% while above 106 K
the difference is around 30% compared to the low density value.
Key words: Sun: atmosphere / di-electronic recombination / metastable levels / contributon function / electron density / line intensity / UV/EUV radiation
© ESO, 2005
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.