Today in Astronomy 142 - Astro Pas Rochester

Today in Astronomy 142 - Astro Pas Rochester Today in Astronomy 142 - Astro Pas Rochester

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10.07.2015 Views

11-year sunspot cycle, for the last 400 yearsFigure: Chaisson and McMillan, Astronomy TodayAstronomy 142 22

Sunspot formation and cycle: interaction ofmagnetism and differential rotationThe Sun rotates, but not as a solid body; this differentialrotation wraps and distorts an initially “poloidal” solarmagnetic field.! Occasionally, the field lines burst out of the surface andloop through the lower atmosphere, thereby creating asunspot pair. The underlying pattern of the solar fieldlines explains the observed pattern of sunspot polarities.! If the loop happens to occur on the limb of the Sun and isseen against dark space, a prominence is visible.! The twisting and wrapping of the field lines eventuallyresults in the production of a poloidal field again, but withnorth and south switched. Then the process repeats.! 22 years between identical field configurations, 11 yearsbetween sunspot-number maxima.Astronomy 142 23

11-year sunspot cycle, for the last 400 yearsFigure: Chaisson and McMillan, <strong><strong>Astro</strong>nomy</strong> <strong>Today</strong><strong><strong>Astro</strong>nomy</strong> <strong>142</strong> 22

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