A TRUE-FIELD MAGNETOGRAM IN A SOLAR PLACE REGION

A new instrument, the Near-Infrared Magnetograph, has been used to make the first two-dimensional image of true magnetic field strength in the solar photosphere. The magnitude of the magnetic field vector is derived with a typical formal precision of +/- 75 G (2-sigma) from circularly polarized spectra of a highly Zeeman-sensitive iron line at 6388.6 cm-1 (1.565-mu-m). The true-field map demonstrates that the properties of "kilogauss" flux tubes vary coherently on a variety of spatial scales within the 1' field of view. The measured fields span the range 1000-1700 G. The amplitude of the polarized signal implies that the spatial filling factor of the flux tubes can approach 0.3 at the seeing-limited resolution of 2". Magnetic field strength and magnetic flux are statistically related in the sense that weak-field areas are weak-flux areas, but strong fields are present in both strong-flux and weak-flux areas. This implies a degree of independence in the relationship between the filling factor of flux tubes and their individual properties, such as field strength, pressure, and temperature.