Astronomical Institute of the Czech Academy of Sciences
Natural Sciences (Astrophysics and Astrononmy)
We present high-resolution full-Stokes measurements of sunspots, using the highly-sensitive full-split (g=3) infrared line Fe I 1564.85 nm, and compare them with simultaneous continuum intensity measurements. We extend the classical work of Kopp & Rabin (1992, Solar Phys. 141, 253) from the intensity to the full Stokes vector. The data were obtained with the GREGOR Infrared Spectrograph (GRIS) on May 11, 2015, using the adaptive optics system. The observations include three large sunspots of active region 12339, with spatial resolution better than 0.5" in the spectral scans. The continuum intensity is corrected for instrumental scattered light and the brightness temperature is calculated. Magnetic field strength and inclination are derived directly from the line split and ratio of Stokes components. The continuum intensity relation to the field strength and inclination are studied separately in the umbra, light bridges, and penumbra. The results agree with previous studies but the higher spatial resolution leads to a larger scatter of values in the continuum intensity (temperature) and magnetic-field relations.
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