July 8, 2019: Solar Cycle 25 is coming to life. For the second time this month, a sunspot from the next solar cycle has emerged in the sun’s southern hemisphere. Numbered “AR2744”, it is inset in this magnetic map of the sun’s surface from NASA’s Solar Dynamics Observatory:
How do we know this sunspot belongs to Solar Cycle 25? Its magnetic polarity tells us so. Southern sunspots from old Solar Cycle 24 have a -/+ polarity. This sunspot is the opposite: +/-. According to Hale’s Law, sunspots switch polarities from one solar cycle to the next. AR2744 is therefore a member of Solar Cycle 25.
Solar cycles always mix together at their boundaries. Right now we are experiencing the tail end of decaying Solar Cycle 24. AR2744 shows that we are simultaneously experiencing the first stirrings of Solar Cycle 25. The transition between Solar Cycle 24 and Solar Cycle…
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