Butterfly diagram showing paired pattern of sunspots. Graph shows sunspot numbers.
<ul><li><a href="https://en.wikipedia.org/wiki/Sp%C3%B6rer%27s_law" class="extiw" title="en:Spörer's law">en:Spörer's law</a> noted that at the start of an 11-year sunspot cycle, the spots appeared first at higher latitudes and later in progressively lower latitudes.</li>
<li>The <a href="https://en.wikipedia.org/wiki/Babcock_Model" class="extiw" title="en:Babcock Model">en:Babcock Model</a> explains the behavior described by Spörer's law, as well as other effects, as being due to magnetic fields which are twisted by the Sun's rotation.</li></ul>
NASA, Marshal Space Flight Center, Solar Physics
<ul><li><a rel="nofollow" class="external free" href="http://solarscience.msfc.nasa.gov/images/bfly.gif">http://solarscience.msfc.nasa.gov/images/bfly.gif</a> (updated monthly)</li>
<li><a rel="nofollow" class="external free" href="http://solarscience.msfc.nasa.gov/SunspotCycle.shtml">http://solarscience.msfc.nasa.gov/SunspotCycle.shtml</a> (explanatory text)</li></ul>