INFRARED LINES AS PROBES OF SOLAR MAGNETIC FEATURES .6. THE THERMAL-MAGNETIC RELATION AND WILSON DEPRESSION OF A SIMPLE SUNSPOT

We analyse the relationship between the temperature and the magnetic v ector, as derived from 1.56 mum spectra, in a simple sunspot. Due to t he high Zeeman sensitivity of the g = 3, 1.56 mum line, we can study t his relationship throughout the sunspot. We confirm the field-strength , B, vs. temperature, T, relationship found by Kopp & Rabin (1992). In addition, we also find a linear relation between the magnetic inclina tion angle, gamma', and T. An analysis based on the assumption of magn etohydrostatic force balance gives an estimate of the Wilson depressio n, Z(W), throughout the sunspot. Our analysis supports a jump in Z(W) of 200-500 km at the umbral boundary and agrees with a relatively cons tant Z(W) in the penumbra. In addition, we constrain various gradients of magnetic parameters and judge the strength of magnetic curvature f orces. For example, we set tight limits on the vertical gradient of ga mma', the magnetic inclination angle to the vertical, in the penumbra. Finally, we discuss the consequences for, e.g., the model proposed by Sanchez Almeida & Lites (1992) to explain the broad-band circular pol arization measured in sunspots.