Spectral manifestations of extremely strong magnetic fields in the sunspot umbra

Abstract

Fine peculiarities of the Zeeman effect in two big sunspots of October 29, 2003, and October 25, 2014, are analyzed. In order to search spectral evidences of very strong spatially unresolved magnetic fields, the Stokes I±V and V profiles of the FeI 6301.5 and 6302.5Å lines are studied in detail. Confirmed are two effects discovered earlier by Lozitsky (2016): (a) non-parallelism of bisectors in the FeI 6301.5 line at a distance of about ±250mÅ from the line center and (b) the existence of weak secondary peaks in Stokes V of the FeI 6302.5 line placed at a distance of, on the average, ±375mÅ from the line center. Close correlation (r=0.77±0.06) was found between (a) and (b) effects indicating the reality of very strong (≈8kG) unresolved magnetic fields. For the first sunspot, the presence of the abovementioned 8-kG fields is traced along 12Mm of the sunspot umbra. The filling factor is 0.2–0.3 here, and the relative Doppler velocities (without Evershed’s effect) are from −1.7 to −3.1km/s (plasma lifting). Similar parameters were also obtained for the second sunspot.