The Cancellation of Magnetic Flux. I. On the Quiet Sun

Abstract

We studied the disappearance of magnetic flux in an area of the quiet Sun from digital and photographic magnetograms recorded at 2·5 min intervals for many hours on 9 July 1984 at the Big Bear Solar Observatory. We limited the quantitative part of the analyses to features which had a total of 1017 Mx (1 Mx "'" 10-8 Wb) or greater and at least a 20 G (1 G"", 10-4 T) contour, and which changed by more than 10% of the maximum measured flux during the 5·5 hours of most consistent image quality during the observing day. Sixteen examples of flux disappearance and three ephemeral regions met these criteria. The disappearance of flux in these examples occurred only in closely spaced features of opposite polarity. The mutual disappearance of magnetic flux in closely spaced features of opposite polarity is herein defined as 'cancellation'. The 16 examples of cancellation were observed in combinations of network features, intranetwork features, and ephemeral regions. In two of the three ephemeral regions, an imbalance of magnetic flux between the two poles within each of the ephemeral regions was created, at least in part, by the cancellation of one pole with an adjacent feature of opposite polarity. Many smaller cancellation are clearly recognized below the threshold that we established for our initial measurements. We conclude that cancellation is the dominant way in which magnetic flux is observed to disappear on the quiet Sun.