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Mount Wilson scheme

A way of classifying sunspots in terms of their magnetic properties. Alpha denotes a unipolar sunspot group. Beta denotes a sunspot group having both positive and negative magnetic polarities, with a simple and distinct division between the polarities. Beta-Gamma denotes a sunspot group that is bipolar but in which no continuous line can be drawn separating spots of opposite polarities. Delta denotes a complex magnetic configuration of a solar sunspot group consisting of opposite polarity umbrae within the same penumbra. Gamma denotes a complex active region in which the positive and negative polarities are so irregularly distributed as to prevent classification as a bipolar group.

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