Single-point coronal magnetometry using multi-line spectropolarimetric observations
Abstract
The US National Science Foundation's Daniel K Inouye Solar Telescope (DKIST) will soon provide large-aperture coronagraphic observations of polarized coronal emission lines in the visible and infrared spectrum at spatial resolutions close to 1 arcsec, comparable to space-based observatories. Polarized via coherent scattering and the Zeeman Effect, the targeted emission lines hold diagnostic potential for the hard-to-measure coronal magnetic field. DKIST provides the requisite advances in spatial resolution, spectral coverage, and polarimetric sensitivity in these lines to advance our understand of coronal magnetic structure; however, techniques for inferring the field parameters from the observations require careful consideration. Here we discuss a technique that combines two or more magnetic-dipole (M1) coronal lines to infer the vector components of the coronal magnetic field that do not require detailed knowledge of the other intrinsic plasma state variables. Generalizing the analytical formalism of the 'single-point' inversion approach introduced by Plowman (2014) we show that some combinations of M1 lines contain degenerate spectropolarimetric information which prohibits their application for this technique. This may include the pair of Fe XIII 10747, 10797 Å emission lines originally proposed by Plowman. Through a sensitivity analysis based on photon noise and polarized atomic modeling based on coronal loop properties, we discuss using the Fe XIII 10747 Å, Si X 14301 Å line pair as one alternative combination for implementing this technique. We find that for noise levels around 10$^{-4}$ of the line intensity, which will be available with DKIST, magnetic fields with sufficient strength ($\sim$25 G) and not severely inclined to the line-of-sight (<35$^\circ$) can be recovered with this method. We discuss potential targets for this method and limitations for it's applicability.
- Publication:
-
43rd COSPAR Scientific Assembly. Held 28 January - 4 February
- Pub Date:
- January 2021
- Bibcode:
- 2021cosp...43E1788D