|
|||||
|
|
Coronal Diagnostics from Narrowband Images Around 30.4 nm |
|
| Authors: | V Andretta D Telloni G Del Zanna |
| Institution: | 1. INAF/Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, 80131, Napoli, Italy 2. INAF/Osservatorio Astrofisico di Torino, Strada Osservatorio 20, 10025, Pino Torinese (TO), Italy 3. DAMTP, Centre for Mathematical Sciences, University of Cambridge, Cambridge, UK |
| Abstract: | Images taken in the band centered at 30.4 nm are routinely used to map the radiance of the He?ii Ly?α line on the solar disk. That line is one of the strongest, if not the strongest, line in the EUV observed in the solar spectrum, and one of the few lines in that wavelength range providing information on the upper chromosphere or lower transition region. However, when observing the off-limb corona, the contribution from the nearby Si?xi 30.3 nm line can become significant. In this work we aim at estimating the relative contribution of those two lines in the solar corona around the minimum of solar activity. We combine measurements from CDS taken in August 2008 with temperature and density profiles from semiempirical models of the corona to compute the radiances of the two lines, and of other representative coronal lines (e.g. Mg?x 62.5 nm, Si?xii 52.1 nm). Considering both diagnosed quantities from line ratios (temperatures and densities) and line radiances in absolute units, we obtain a good overall match between observations and models. We find that the Si?xi line dominates the He?ii line from just above the limb up to ≈?2?R ⊙ in streamers, while its contribution to narrowband imaging in the 30.4 nm band is expected to become smaller, even negligible in the corona beyond ≈?2?–?3?R ⊙, the precise value being strongly dependent on the coronal temperature profile. |
| Keywords: | |
| 本文献已被 SpringerLink 等数据库收录！ | |