Signatures of superstrong magnetic fields in a limb solar flare from observations of the Hα line

Abstract

We present signatures of the super-strong magnetic fields of almost 105 Gauss range in the limb solar flare of 14 July 2005 at the altitudes of 5 – 30 Mm during the post-peak phase of the flare. These features follow from the study of the Stokes V profile in the Hα line at large distances of 1.5 up to 4 Å from its center. A reliable circular polarization (till 1%) was found that changes its sign when crossing the line center. The profile of the polarization differs significantly from the intensity gradient profile dI/dλ, which indicates the strong magnetic field mode. If these features are interpreted as manifestations of the Zeeman effect, the corresponding magnetic field strength reaches ∼ 90 kG. Similar spectral manifestations were not found in another bright emission formation on the solar limb, namely in the active prominence of 24 July 1999. Theoretical analysis of the picture of the Zeeman effect for the case of such giant fields shows that the σ components of the Hα line should be quite narrow (∼0.2 Å) due to the Pashen-Back effect, despite the complex picture of the splitting of this line. Since the observed widths of the peaks of the Stokes V profiles are much wider, this may mean a certain dispersion of the magnetic field strengths in the flare, at which the maximum strengths can be even some greater than those indicated above.