A NOVEL METHOD TO DETERMINE MAGNETIC FIELDS IN LOW-DENSITY PLASMA FACILITATED THROUGH ACCIDENTAL DEGENERACY OF QUANTUM STATES IN Fe⁹⁺

Abstract

We propose a new method to determine magnetic fields, by using the magnetic-field induced electric dipole transition 3p 4 3d 4 D 7/2 → 3p 5 2 P 3/2 in Fe 9+ ions. This ion has a high abundance in astrophysical plasma and is therefore well-suited for direct measurements of even rather weak fields in e.g. solar flares. This transition is induced by an external magnetic field and its rate is proportional to the square of the magnetic field strength. We present theoretical values for what we will label the reduced rate and propose that the critical energy difference between the upper level in this transition and the close to degenerate 3p 4 3d 4 D 5/2 should be measured experimentally since it is required to determine the relative intensity of this magnetic line for different magnetic fields. * Electronic address: Tomas.Brage@fysik.lu.se † Electronic address: rhutton@fudan.edu.cn

Magnetic-field- and hyperfine-induced P03−S01 transitions in Be- and Ne-like ions

“…The experimental results for the MIT-fs rates of Ne-like ions are in good agreement with previous theoretical predictions [6]. Recently, it was also proposed that MIT-fs in Cl-like Fe could be used to probe the solar coronal magnetic field [8,11].…”

“…There are a wide range of calculations for hyperfineinduced transitions (HIT) [3,12,[14][15][16]19,20,39,42] and magnetic-field-induced transitions for isotopes without nuclear spin (MIT-fs) [2,6,8]. Here, we focus on discussing the magnetic-field-and hyperfine-induced (MIT-hfs) transitions for isotopes with nuclear spin.…”

“…To distinguish these cases from when hyperfine interaction is present, we label them MIT-fs. The theory for these has been discussed in recent publications for Be-, Ne-, and Cl-like ions [6][7][8].…”

Solar UV and X-ray spectral diagnostics

“…The MIT in Fe x was discussed in detail by Li et al. (2015). In the presence of a strong magnetic field, the two states will mix, which will produce a new MIT (E1) from the level to the ground state , see Fig.…”

“…Li et al. (2015) carried out increasingly large atomic structure calculations, which were used to estimate the splitting of the and levels, which turns out to be a major uncertainty in the diagnostic. The best calculations provided a splitting of .…”