Vertical gradients of the magnetic fields in active regions

In this paper, we describe the results of an investigation of magnetic field structures in two active regions. The photospheric magnetic fields were measured simultaneously in all three components with the Crimean vector magnetograph in the Fe i 5250 line. In our analysis, we compare the observed magnetic field with the potential field. The potential field vector was calculated according to the potential-field theory, and the H_zcomponent was taken as a boundary condition. From these data vertical gradients are calculated from the condition div H = 0. Averaged gradients of both fields increase with the H_zfield intensity and within the error limits they do not differ from one another for field strengths up to 1200 G. For larger H_zthe potential field gradients become higher than those of the observed field. In large spots, observed field gradients are about two times less than those of the potential field. It is shown that this difference is connected with the observed field twisting.