DYNAMIC PROPERTIES ALONG THE NEUTRAL LINE OF A DELTA SPOT INFERRED FROM HIGH-RESOLUTION OBSERVATIONS

Delta (delta) spots are complex magnetic configurations of sunspots characterized by umbrae of opposite polarity sharing a common penumbra. In order to investigate the fine structure of the region separating the two magnetic polarities of a delta spot, we studied the morphology, the magnetic configuration, and the velocity field in such a region using observations of active region (AR) NOAA 11267 obtained with the CRisp Imaging SpectroPolarimeter (CRISP) at the Swedish Solar Telescope on 2011 August 6. The analysis of CRISP data shows upflows and downflows of similar to +/- 3 km s(-1) in proximity of the delta spot polarity inversion line (PIL), and horizontal motions along the PIL of the order of similar to 1 km s(-1). The results obtained from the SIR inversion of CRISP data also indicate that the transverse magnetic field in the brighter region separating the two opposite magnetic polarities of the delta spot is tilted about similar to 45 degrees with respect to the PIL. Solar Dynamics Observatory/Helioseismic and Magnetic Imager observations confirm the presence of motions of similar to +/- 3 km s(-1) in proximity of the PIL, which were observed to last 15 hr. From the data analyzed, we conclude that the steady, persistent, and subsonic motions observed along the delta spot PIL can be interpreted as being due to Evershed flows occurring in the penumbral filaments that show a curved, wrapped configuration. The fluting of the penumbral filaments and their bending, continuously increased by the approaching motion of the negative umbra toward the positive one, give rise to the complex line-of-sight velocity maps that we observed.