ATOMIC-LEVEL PSEUDO-DEGENERACY OF ATOMIC LEVELS GIVING TRANSITIONS INDUCED BY MAGNETIC FIELDS, OF IMPORTANCE FOR DETERMINING THE FIELD STRENGTHS IN THE SOLAR CORONA

Abstract

We present a measured value for the degree of pseudo-degeneracy between two fine-structure levels in Fe 9+ from line intensity ratios involving a transition induced by an external magnetic field. The extracted fine-structure energy difference between the and 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 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 Fe 9+ 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 Fe 9+ . In addition, the proposed method to use the line ratio of the blended line with another line from Fe x as the density diagnostic should evaluate the effect of the magnetic-field-induced transition line.