From time to time, the photosphere of the Sun is marked by sunspots.  There is a structure to sunspots as seen in this marvelous imageSunspots are somewhat cooler than their surroundings, that's why they appear dark. Just how do sunspots work? Here are some ideas.    Every    eleven    years     under    the    influence    of    the    Sun's    magnetic    field     the    number    of sunspots    increases   and   decreases.   The   arrangement   of   these   spots   forms   an   interesting   butterfly   pattern .   We   are just   past   sunspot   maximum ,   as   you   can   see   from   this   recent   image .      But   the   size   of   each   maximum   has   seemed   to decline   recently .      This   seems   to   be   part   of   a   much   longer   overall   trend .      During   sunspot   maximum,   there   are   always concerns    about   the   charged   particles   which   the   Sun   will   be   throwing   our   way.      Scientists   suspect   that   sunspot   activity   might   have   an effect   on   Earth’s   weather .         During   times   of   sunspot   maximum,   violent   flares   can   erupt   on   the   surface   of   the   Sun. These   flares    last   15   or 20   minutes   or   so,   and   are   tremendous   releases   of   magnetic   energy   on   the   Sun.   Every   sunspot   cycle   sees   the   magnetic   polarity   of   the spots reverse.     Here is a great image of a sunspot group showing a lot of the detail of umbra and penumbra.
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Carpe Caelum
Carpe Caelum Stellar Astronomy
Carpe Caelum Stellar Astronomy