A RELATION BETWEEN MAGNETIC-FIELD STRENGTH AND TEMPERATURE IN SUNSPOTS

We present Stokes I Zeeman splitting measurements of sunspots using the highly sensitive (g = 3) Fe I line at lambda = 1.5649 mum. The splittings are compared with simultaneous intensity measurements in the adjacent continuum. The relation between magnetic field strength and temperature has a characteristic, nonlinear shape in all the spots studied. In the umbra, there is an approximately linear relation between B2 and T(b), consistent with magnetohydrostatic equilibrium in a nearly vertical field. A distinct flattening of the B2 vs T(b) relationship in the inner penumbra may be due to changes in the lateral pressure balance as the magnetic field becomes more horizontal; spatially unresolved intensity inhomogeneities may also influence the observed relation.