Summary

Description

<p> The understanding of the line emission from heavy ions is still incomplete and often inaccurate, resulting in missing or incorrect line assignments and missing or incorrect flux. This limits the utility both of spectral predictions and of space-based equipment used for observing the solar spectrum. An example of this is the 195 Å channel of TRACE, which is centered on the FeXII line. Recent changes in the atomic data used to model the spectral emission near 195 Å have dramatically (up to an order of magnitude) changed the temperature response of this channel. A similar situation is likely to recur for the Atmospheric Imaging Assembly (AIA) instrument, which is to be launched as part of the Solar Dynamics Observatory. Here the responses of the six iron line channels, centered on lines from FeIX, FeXII, FeXIV, FeXVI, FeXVIII, FeXX, FeXXIII, and FeXXIV, sensitively depend on the correct position and strength of neighboring lines that fall within the instrumental response. Current predictions from various theoretical models describing the emission covered by these channels are in disagreement, and definitive experimental observations at the level of detail needed for establishing an authoritative model are nonexistent. Given the impending launch of the Solar Dynamics Observatory, which is a key mission in the Heliophysics Research Program, a resolution of the spectral modeling issues by definitive laboratory measurements is not only timely but urgently needed. Here we propose to conduct the definitive laboratory measurements required for calibrating the temperature response of the six AIA iron channels. Our work will provide highly accurate wavelength and intensity information of all relevant lines falling into the wavelength bands of the six Fe channels. This will provide the data for producing the high-confidence spectral modeling codes needed for use in calibrating the response of each iron line channel as well as for the successful evaluation and utilization of the observational data from the six AIA iron line channels.</p>