The Diagnostic Potential of Transition Region Lines under-going Transient Ionization in Dynamic Events |
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Gerry Doyle Submitted: 2012-04-30 05:00
We discuss the diagnostic potential of high cadence ultraviolet spectral data when transient ionization is considered. For this we use high cadence UV spectra taken
during the impulsive phase of a solar flares (observed with instruments on-board the Solar Maximum Mission) which showed excellent correspondence with hard X-ray pulses. The ionization fraction of the transition region ion O V and in particular the contribution function for the O V 1371A line are computed within the Atomic Data and Analysis Structure,
which is a collection of fundamental and derived atomic data and codes which manipulate them. Due to transient ionization, the O V 1371A line is enhanced in the first fraction of a second with the peak in the line contribution function occurring initially at a higher electron temperature than in ionization equilibrium. The rise time and enhancement factor depend mostly on the electron density. The fractional increase in the O V 1371A emissivity due to transient ionization can reach a factor of 2-4 and can explain the fast response in the line flux of transition regions ions during the impulsive phase of flares solely as a result of transient ionization. This technique can be used to diagnostic the electron temperature and density of solar flares observed with the forth-coming Interface Region Imaging Spectrograph.
Authors: J.G. Doyle, A. Giunta, A. Singh, M.S. Madjarska, H. Summers, B.J. Kellett & M. O'Mullane
Projects: Solar Max Misson
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Publication Status: Solar Phys (accepted)
Last Modified: 2012-05-01 10:16
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