On the evolution of the solar photospheric and coronal magnetic field

The Extreme Ultraviolet Imaging Telescope (EIT) and the Michelsen Doppler I mager (MDI) instruments on the Solar and Heliospheric Observatory (SOHO) ra n a coordinated observing campaign over the dates 1997 August 10-14. MDI ge nerated 1".2 resolution magnetograms (0".6 pixels) of the solar photosphere at a nominal cadence of one minute while EIT observed Fe XII (195 Angstrom ) (5" resolution; 2".5 pixels) in the MDI high-resolution field of view at a cadence of similar to 17 minutes. We investigate the relationship between the quiet-Sun photospheric magnetic field and the quiet solar corona by fi rst removing instrumental effects from the EIT data, time-averaging the MDI data for improved statistics, and coaligning the two data sets and applyin g solar rotation tracking. At the time of the observation, this was the lon gest continuous run of its kind. We conduct a detailed investigation of the processes of evolution in the photospheric magnetic field and look for sym pathetic effects in the solar corona. We measure the lifetimes, dimensions, and orientations of small-scale coronal brightenings and reconcile these p rocesses against the evolution of the underlying photospheric magnetic fiel d. Using statistics collected from this study, we find that emerging bipole s in quiet Sun reach a typical length of approximate to 14 Mm before fading or reconnecting to other flux concentrations in a time period of approxima te to5-12 hr, and the quiet solar corona completely decorrelates in approxi mately 15 hr. We find that the majority of large coronal loops in quiet Sun are the products of numerous smaller magnetic flux concentrations coalesci ng in the photosphere rather than the product of a single large emerging bi pole. This continuous process of emergence and coalescence leads to the obs ervation that there is no preferred orientation to small-scale coronal brig htenings in the solar corona.