Small-scale magnetic field diagnostics in solar flares using bisectors of I ± V profiles

In the present study, spatially unresolved magnetic fields in solar flares are investigated by analyzing the fine structure of Zeeman splitting in two FeI lines. Namely, we consider bisector splitting of I ± V Stokes profiles in 5123.7 and 5233 Ǻ lines. The analysis of bisector splitting functions (BSF) of the 5233 Ǻ line averaged over 12 solar flares of different classes, from C5 to X1.4, reveals two distinct peaks, around Δλ = 80-110 mǺ and 170-200 mǺ. Such peculiarities indicate the unacceptability of weak field approximation for FeI 5233 line and need interpretation in the framework of inhomogeneous models with strong magnetic field components. Consequently, we argue that the named two peaks can reflect the existence of two discrete modes of subtelescopic magnetic fields with strengths about 6 and 12 kG in photospheric layers.