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Laboratory Measurements of Electron Impact Ionization in Support of the NASA Heliophysics Research Program Project

Metadata Updated: November 12, 2020

<p> Our knowledge of the outer solar atmosphere and solar wind rests to a large degree on our understanding of the underlying ionization balance for the observed gas. The outer solar atmosphere is comprised of the chromosphere, transition region, and corona. The spectral and thermal properties of these and the solar wind are determined by the charge state distribution (CSD) for the different elements in the gas. Hence, interpreting spectral observations or particle measurements and developing accurate models for the outer solar atmosphere and solar wind all depend fundamentally upon reliable ionization balance calculations. These CSD calculations rest in turn upon accurate rate coefficients for electron impact ionization (EII) and for high electron temperature (Te) dielectronic recombination (DR). In the outer solar atmosphere and solar wind, EII is the dominant ionization mechanism and high Te DR is the dominant electron-ion recombination process.</p> <p> To address these atomic data needs of the solar physics community, we have been funded since May 1, 2000 by the NASA Solar and Heliospheric Physics (SHP) Supporting Research (SR) program. During this time we have successfully carried out a series of heavy ion storage ring measurements and theoretical calculations designed to generate new and more reliable recombination and ionization data for the solar physics community. The bulk of our effort to date has been focused on DR but recently we have expanded our work to include EII. Additionally, using state-of-the-art theoretical DR data benchmarked by our SR-supported DR measurements, state-of-the-art theoretical radiative recombination (RR) data, and the most recent compilation of EII data, we have generated new CSDs for gas in coronal ionization equilibrium (CIE) for all elements from H to Zn (Bryans et al. 2009). We have also used these data to analyze coronal observations, investigate the solar physics implications of our new CIE results, and look for remaining errors in the atomic data (Hahn et al. 2010b).</p> <p> We propose to continue our ongoing reseach program and carry out a series of EII measurements using the heavy ion Test Storage Ring (TSR) located at the Max Planck Institute for Nuclear Physics (MPIK) in Heidelberg, Germany. A major limitation of almost all existing EII data has been the difficulty of providing unambiguous experimental results due to the challenge of producing wellcharacterized ion beams. Most ion sources generate beams with unknown fractions of metastable and ground state ions. The storage ring approach effectively solves this problem by storing the ion beam long enough that essentially all metastable levels radiatively decay to the ground state before data are collected.</p> <p> We plan to carry out new EII measurements at TSR for nine iron ions: Fe ix, x, xi, xiv, xv, xvii, xviii, xx, and xxi. Here and throughout we label the ionizing or recombining systems using the inital charge state of the ion. We focus on iron because it is prominent in solar spectra. These particular ions were chosen because they are important for analyzing observations by the EUV Imaging Spectrometer (EIS) on Hinode and by the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO).</p> <p> TSR began operation in 1988. It is the only storage ring in the world currently capable of performing the proposed measurements. However, it will be shut down at the end of 2012. The work proposed here thus represents the last opportunity to obtain these unambiguous EII data for the foreseeable future.</p> <p> In the remainder of this section we discuss in more detail the motivation behind the proposed research and how our work will address the needs of the solar physics community. Section 2 reviews the EII and DR processes and the state of experimental and theoretical knowledge. A description of TSR and the experimental techniques u

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Public: This dataset is intended for public access and use. License: No license information was provided. If this work was prepared by an officer or employee of the United States government as part of that person's official duties it is considered a U.S. Government Work.

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Metadata Created Date November 12, 2020
Metadata Updated Date November 12, 2020

Metadata Source

Harvested from NASA Data.json

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Resource Type Dataset
Metadata Created Date November 12, 2020
Metadata Updated Date November 12, 2020
Publisher Science Mission Directorate
Unique Identifier Unknown
Identifier TECHPORT_10781
Data First Published 2011-09-01
Data Last Modified 2020-01-29
Public Access Level public
Bureau Code 026:00
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Harvest Source Title NASA Data.json
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Source Datajson Identifier True
Source Hash 9935fd84971b0c5fde931f58192506fead36c2ba
Source Schema Version 1.1
Temporal 2011-09-01T00:00:00Z/2014-09-01T00:00:00Z

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