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ATOMIC-LEVEL PSEUDO-DEGENERACY of ATOMIC LEVELS GIVING TRANSITIONS INDUCED by MAGNETIC FIELDS, of IMPORTANCE for DETERMINING the FIELD STRENGTHS in the SOLAR CORONA

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Author

  • Wenxian Li
  • Yang Yang
  • Bingsheng Tu
  • Jun Xiao
  • Jon Grumer
  • Tomas Brage
  • Tetsuya Watanabe
  • Roger Hutton
  • Yaming Zou

Summary, in English

We present a measured value for the degree of pseudo-degeneracy between two fine-structure levels in Fe9+ from line intensity ratios involving a transition induced by an external magnetic field. The extracted fine-structure energy difference between 3p4 3d 4D7/2 the and 4D7/2 levels, where the latter is the upper state for the magnetic-field induced line, is needed in our recently proposed method to measure magnetic-field strengths in the solar corona. The intensity of the 3p4 3d 4D7/2 → 3p5 2 P3/2 line at 257.262 Å is sensitive to the magnetic field external to the ion. This sensitivity is in turn strongly dependent on the energy separation in the pseudo-degeneracy through the mixing induced by the external magnetic field. Our measurement, which uses an Electron Beam Ion Trap with a known magnetic-field strength, indicates that this energy difference is 3.5 cm-1. The high abundance of Fe9+ and the sensitivity of the line's transition probability to field strengths below 0.1 T opens up the possibility of diagnosing coronal magnetic fields. We propose a new method to measure the magnetic field in the solar corona, from similar intensity ratios in Fe9+. In addition, the proposed method to use the line ratio of the blended line 3p4 3d 4D7/2.5/2 → 3p5 2P3/2 with another line from Fe x as the density diagnostic should evaluate the effect of the magnetic-field-induced transition line.

Publishing year

2016-08-01

Language

English

Publication/Series

Astrophysical Journal

Volume

826

Issue

2

Document type

Journal article

Publisher

American Astronomical Society

Topic

  • Atom and Molecular Physics and Optics
  • Astronomy, Astrophysics and Cosmology

Keywords

  • atomic processes
  • magnetic fields
  • Sun: corona
  • techniques: spectroscopic
  • UV radiation

Status

Published

ISBN/ISSN/Other

  • ISSN: 0004-637X