The Formation of a Moat Around a Sunspot as Observed on Longitudinal–Field Magnetograms (?)

In this paper the dynamics of the photospheric magnetic field near the sunspot of the active region McMath 15508 is considered on the basis of longitudinal magnetic field B11 magnetograms. The magnetograms were obtained at the panoramic magnetograph of the Sayan Observatory. The time taken to obtain one magnetogram was 5 min. The spatial resolution was 1.8“ × 3.6“. In the active region McMath 15508 a new bipolar spot group formed westward of the existing sunspot group on September 1; the next day the main sunspots had penumbras, and on September 3 the new sunspot group reached a maximum area and began decaying thereafter.