MOUNT WILSON MAGNETIC CLASSIFICATIONS
Alpha. Denotes a unipolar SUNSPOT group.
Beta. A sunspot group having both positive and negative mag-
netic polarities, with a simple and distinct division between
Beta-Gamma. A sunspot group that is bipolar but in which no
continuous line can be drawn separating spots of opposite
Delta. A complex magnetic configuration of a solar sunspot
group consisting of opposite polarity UMBRAe within the same
Gamma. A complex ACTIVE REGION in which the positive and nega-
tive polarities are so irregularly distributed as to prevent
classification as a bipolar group.