The chromospheric magnetic field in active regions derived from spectropolarimetry of Ca II 8542

TL;DR

This study measures the magnetic field in the Sun's chromosphere and photosphere using spectropolarimetric data from IBIS and Hinode, revealing field strengths up to 2 kG in photosphere and 800 G in chromosphere.

Contribution

It presents a comparative analysis of chromospheric and photospheric magnetic fields using the COG method on spectropolarimetric data, providing new insights into active region magnetic structures.

Findings

Photospheric magnetic fields reach up to 2 kG in plages and umbra.

Chromospheric LOS field strength inside umbra reaches 800 G.

Magnetic field strength decreases toward sunspot edges.

Abstract

We analyze spectropolarimetric observations of the chromospheric Ca II 8542 line taken by the Interferometric Bidimensional Spectrometer (IBIS) at the Dunn Solar Telescope and photospheric Fe I 6302 lines obtained with the Solar Optical Telescope (SOT) of Spectro-polarimeter (SP) on board the Hinode satellite. The data were obtained on 2012 January 29 targeting NOAA active region (AR) 11408 and AR 11410. By using the center-of-gravity (COG) method we compute the line-of-sight (LOS) field strength for observed lines of Fe I 6301.5/6302.5 with SP spacecraft at every places in the active region. Also, we construct a COG map for the chromospheric IBIS data of Ca II 8542 line in comparison with COG maps derived from the SP of field strength. We found the photospheric field strength ranges up to 2 kG in plages and up to 2 kG or higher values inside the umbral region. In the case of chromospheric field strength, the LOS field inside the umbral region increases up to 800 G, and the field strength decreases toward the edges of sunspot.