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We report on multi-wavelength ultraviolet (UV) high-resolution observations taken with the IRIS satellite during the emergence phase of an emerging flux region embedded in the unipolar plage of active region NOAA 12529. These data are complemented by measurements taken with the spectropolarimeter aboard the Hinode satellite and by observations from SDO. In the photosphere, we observe the appearance of opposite emerging polarities, separating from each other, and cancellation with a pre-existing flux concentration of the plage. In the upper atmospheric layers, recurrent brightenings resembling UV bursts, with counterparts in all UV/EUV filtergrams, are identified in the EFR site. In addition, plasma ejections are observed at chromospheric level. Most important, we unravel a signature of plasma heated up to 1 MK detecting Fe XII emission in the core of the brightening sites. Comparing these findings with previous observations and numerical models, we suggest evidence of several long-lasting, small-scale magnetic reconnection episodes between the new bipolar EFR and the ambient field. [ABSTRACT FROM AUTHOR]

Sunspots are the most prominent feature of the solar magnetism in the photosphere. Although they have been widely investigated in the past, their structure remains poorly understood. Indeed, due to limitations in observations and the complexity of the magnetic field estimation at chromospheric heights, the magnetic field structure of sunspot above the photosphere is still uncertain. Improving the present knowledge of sunspot is important in solar and stellar physics, since spot generation is seen not only on the Sun, but also on other solar-type stars. In this regard, we studied a large, isolated sunspot with spectro-polarimeteric measurements that were acquired at the Fe I 6173 nm and Ca II 8542 nm lines by the spectropolarimeter IBIS/DST under excellent seeing conditions lasting more than three hours. Using the Non-LTE inversion code NICOLE, we inverted both line measurements simultaneously, to retrieve the three-dimensional magnetic and thermal structure of the penumbral region from the bottom of the photosphere to the middle chromosphere. Our analysis of data acquired at spectral ranges unexplored in previous studies shows clear spine and intra-spine structure of the penumbral magnetic field at chromopheric heights. Our investigation of the magnetic field gradient in the penumbra along the vertical and azimuthal directions confirms results reported in the literature from analysis of data taken at the spectral region of the He I 1083 nm triplet. [ABSTRACT FROM AUTHOR]

Sunspots are the most prominent feature of the solar magnetism in the photosphere. Although they have been widely investigated in the past, their structure remains poorly understood. Indeed, due to limitations in observations and the complexity of the magnetic field estimation at chromospheric heights, the magnetic field structure of sunspot above the photosphere is still uncertain. Improving the present knowledge of sunspot is important in solar and stellar physics, since spot generation is seen not only on the Sun, but also on other solar-type stars. In this regard, we studied a large, isolated sunspot with spectro-polarimeteric measurements that were acquired at the Fe I 6173 nm and Ca II 8542 nm lines by the spectropolarimeter IBIS/DST under excellent seeing conditions lasting more than three hours. Using the Non-LTE inversion code NICOLE, we inverted both line measurements simultaneously, to retrieve the three-dimensional magnetic and thermal structure of the penumbral region from the bottom of the photosphere to the middle chromosphere. Our analysis of data acquired at spectral ranges unexplored in previous studies shows clear spine and intra-spine structure of the penumbral magnetic field at chromopheric heights. Our investigation of the magnetic field gradient in the penumbra along the vertical and azimuthal directions confirms results reported in the literature from analysis of data taken at the spectral region of the He I 1083 nm triplet. [ABSTRACT FROM AUTHOR]

We report on multi-wavelength ultraviolet (UV) high-resolution observations taken with the IRIS satellite during the emergence phase of an emerging flux region embedded in the unipolar plage of active region NOAA 12529. These data are complemented by measurements taken with the spectropolarimeter aboard the Hinode satellite and by observations from SDO. In the photosphere, we observe the appearance of opposite emerging polarities, separating from each other, and cancellation with a pre-existing flux concentration of the plage. In the upper atmospheric layers, recurrent brightenings resembling UV bursts, with counterparts in all UV/EUV filtergrams, are identified in the EFR site. In addition, plasma ejections are observed at chromospheric level. Most important, we unravel a signature of plasma heated up to 1 MK detecting Fe XII emission in the core of the brightening sites. Comparing these findings with previous observations and numerical models, we suggest evidence of several long-lasting, small-scale magnetic reconnection episodes between the new bipolar EFR and the ambient field. [ABSTRACT FROM AUTHOR]