Weak and strong magnetic fields in the solar photosphere

Abstract

We discuss very high-resolution (1/2'') magnetograms of quiet Sun and plage, which were obtained by using a tunable birefringent filter in Fe I lambda6302. A search for a turbulent bipolar field, using co-added and spatially filtered frames, is unsuccessful. Statistical analysis sets an upper limit of 50 gauss on the rms vertical component of such a field and probably rules out the possibility of field strengths exceeding 100 gauss in the inner network field observed at Kitt Peak. The area, total flux, and energy content of the strong (kilogauss) network fields are measured and compared with the upper limits for these properties of a hypothetical, widespread weak field. In quiet photosphere, a weak background field may contain interesting amounts of flux and energy, but the strong fields are dominant at higher levels and in plage. The total magnetic energy in quiet photosphere is roughly equal to the kinetic energy of granular and oscillatory velocities at the same level. By flux conservation, field strengths in the transition region are greater than 25 gauss in quiet network and 100 gauss in plage.