Spectropolarimetry of the Solar Mg II h and k Lines

Abstract

We report on spectropolarimetric observations across the Mg II h and k-lines at 2800 angstrom made by the Ultraviolet Spectrometer and Polarimeter onboard the Solar Maximum Mission satellite. Our analysis confirms the strong linear polarization in the wings of both lines observed near the limb, as previously reported, but also demonstrates the presence of a negatively (i.e., radially oriented) polarized signal between the two lines. We find evidence for fluctuations of the polarization pattern over a broad spectral range, resulting in some depolarization with respect to the pure scattering case when observed at very low spatial and temporal resolutions. This is consistent with recent theoretical modeling that predicts this to be the result of redistribution effects, quantum interference between the atomic levels of the upper term, and magneto-optical effects. A first attempt at a quantitative exploitation of these signals for the diagnosis of magnetic fields in the chromosphere is attempted. In active regions, we present observations of circular polarization dominated by the Zeeman effect. We are able to constrain the magnetic field strength in the upper active chromosphere using an analysis based on the magnetograph formula, as justified by theoretical modeling. We inferred a significantly strong magnetic field (~500 G) at the 2.5 sigma level on an exceptionally active, flaring region.

(12 pages, 5 figures)

References in corpus (3)

• Magnetic Diagnostics of the Solar Chromosphere with the Mg II h-k Lines
• The magnetic sensitivity of the Mg ii k line to the joint action of Hanle, Zeeman and magneto-optical effects
• Explicit Form of the Radiative and Collisional Branching Ratios in Polarized Radiation Transport with Coherent Scattering

Cited by in corpus (6)

• Mapping Solar Magnetic Fields from the Photosphere to the Base of the Corona
• The magnetic sensitivity of the resonance and subordinate lines of Mg II in the solar chromosphere
• TIC: A Stokes inversion code for scattering polarization with partial frequency redistribution and arbitrary magnetic fields
• Effects of spectral resolution on simple magnetic field diagnostics of the Mg II h & k lines
• Formation of the Mg II h and k polarization profiles in a solar plage model and their suitability to infer magnetic fields
• Derivation of Instrument Requirements for Polarimetry using Mg, Fe, and Mn lines between 250 and 290 nm