Mount Wilson Magnetic Classifications

In solar-terrestrial terms, a classification system for sunspots:

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