This day has been a long time coming. Ever since the beginning of Solar Cycle 24 back on January 4th 2008, solar physicists have been eagerly awaiting the fireworks to begin… alas, the Sun decided to take a break and stay blank for nine months, keeping any Cycle 24 sunspot activity hidden. That’s not to say there have been no sunspots. Due to a strange quirk in solar activity, the previous cycle took some time to wind down and continued to send groups of spots to the surface, occasionally unleashing some surprise flares and coronal mass ejections (CMEs).
However, it has now been confirmed that the sunspot group seen today by the Solar and Heliospheric Observatory (SOHO) and international amateur astronomers do in fact belong to Cycle 24.
Phew, I was beginning to feel a little chilly…
So how do we know these new sunspots have anything to do with the new 11-year solar cycle? Firstly, a quick glance at the SOHO image above tells me that these might be “new” spots as they have been spawned at high latitudes. At the start of a new solar cycle, sunspots tend to appear at high latitudes, and as the (approximate) 11-year cycle progresses, sunspot groups drift toward the equator as solar activity increases. After solar maximum, when you can expect to see a high number of spots, CMEs and flares; the few spots left appear to drift to lower latitudes until they are extinguished at solar minimum.
“Like a breath of fresh plasma, there’s an emerging sunspot group on the Sun. This ends a very low period of activity on the solar surface and as it’s a cycle 24 spot group is very exciting indeed. Seeing conditions weren’t brilliant this morning but, to be honest, I don’t care because there’s a sunspot group to look at!!” – Pete Lawrence, Solar Astronomer,
The issue recently is that the solar minimum separating Cycle 23 and 24 appears to have lasted a little longer than expected, prompting some articles to postulate that this could mark the beginning of an extended period of calm. Solar physicists have disputed this, and although NASA made the bold prediction in 2006 that Cycle 23 will be the biggest cycle we’ve ever experienced, many scientists just think this is a glitch and the cycle will continue as normal very soon.
So how else do we know these new spots are from Cycle 24? By taking measurements of the Sun’s magnetic field, SOHO has been able to deduce the direction of the magnetic field appearing from one spot and feeding down into the other spot (sunspots usually appear in pairs, one with a “north” polar field and one with a “south” polar field). During a solar cycle, the global magnetic field of the Sun “flips” (magnetic north becomes magnetic south and vice versa) – this is known as a polarity change, and this flip can be observed in the nature of sunspots. If the leading spot in the sunspot pair becomes “north” after a period when it used to be “south” this means the global field has swapped polarity and a new solar cycle has begun.
This technique was used in January when the first spots of Cycle 24 were discovered, and it was used again to verify the polarity of today’s spots.
This is all great, very nice to see spots from the new cycle again after a nine month break, but does this signify the start of a more active solar disk? Well, that is something we’ll have to wait and find out, the Sun is notoriously difficult to forecast and I doubt it will be revealing its secrets any time soon…
Original source: Space Weather