  Adopting the thermal free-free emission mechanism, the coronal and
chromospheric magnetic fields are derived from the polarization and spectral
observations with the Nobeyama Radioheliograph at 1.76 cm. The solar active
regions (AR) located near the disk center observed on January 8, 2015 (AR
12257) and December 4, 2016 (AR 12615) are used for the estimate of the
chromospheric and coronal magnetic fields with the microwave radio
observations. We compare solar radio maps of active regions for both intensity
and circularly polarized component with the optical maps from observations with
the Helioseismic and Magnetic Imager and the chromosphere and corona transition
region images obtained with the Atmospheric Imaging Assembly instrument, on
board the Solar Dynamic Observatory. We notice from the comparison between
radio maps of both AR that the circular polarization degree in the AR 12257 is
about 2 percent, but the AR 12615 has a higher existent value by 3 percent.
Radio observations provide us for direct measurements of magnetic fields in the
chromospheric and coronal layers. We estimate the coronal magnetic fields using
the Atmospheric Imaging Assembly observations by adopting magnetic loops in the
corona over some patches with weak photospheric magnetic fields. The coronal
magnetic field derived from the Atmospheric Imaging Assembly data was from 90
to 240 Gauss. We also study the coronal magnetic fields based on the structure
of the extrapolated field, where the result of the magnetic fields was in the
range from 35 to 145 Gauss, showing that the difference in the coronal magnetic
fields between both results is attributed to the assumption of the force-free
approximation.
