Spectral Manifestations of Strong and Especially Strong Magnetic Fields in the Active Prominence on July 24, 1999

Abstract

We present the results of the study of the magnetic field in the active prominence on July 24, 1999 at 07:00 UT, using the observational material obtained on the Echelle spectrograph of the horizontal solar telescope of the Astronomical Observatory of Taras Shevchenko Kyiv National University. Our analysis is based on the study of I ± V profiles of the Hα line, which were related to heights in the range of 11–20 Mm. It was found that the bisectors of the I ± V profiles are non-parallel to each other in majority of places of this prominence. This indicates the inhomogeneity of the magnetic field: with a uniform magnetic field, the named bisectors should be parallel. Moreover, the maximum splitting of bisectors is observed not only in the core of the line (which was found earlier by other authors), but also in its far wings, at distances of 1.5–2.5 Å from the line center. The specified maximum of splitting corresponds to magnetic field of about 3000 G, but this value should be considered only as a lower estimate of the true local magnetic fields. In particular, the second maximum of bisector splitting may indicate that the actual value of Zeeman splitting in small-scale structures with a small filling factor reaches the above value of 1.5–2.5 Å which corresponds to the field strength of almost 100 kG. From our study it follows that evidences on such extremely magnetic fields may not actually be a rare phenomenon, but a rather common one, which, however, can be recorded only under certain favorable observational conditions.