The 24th Cycle
Published on Jan 6, 2008 at 8:03 am.
2 Comments.
Filed under Sun.
For the earliest days of telescopes, astronomers have known that the Sun has spots. But, the number of sunspots is not constant. Individual spots come and go. In 1843, Heinrich Schwabe noted that the number of sunspots seems to go through a pattern that lasts a bit over a decade. The sun starts the cycle with few or no spots. Then, over the next few years, it gradually gets more and more spots. Then, the number of spots drops again to near zero. The sunspot cycles are numbered using reconstructed data back to observations in the 18th Century. We just finished the 23rd Cycle and we are waiting for the start of the 24th Cycle. The sunspot cycle was shown to last an average of about 11 years. Sometimes a cycle is a year or so short, or a year or so long. But, we now know (thanks in part to the work of Walter Adams and George Ellery Hale) that sunspots are associated with regions of intense magnetic field. We also know that the magnetic field of the Sun reverses with each sunspot cycle. In fact, that is how we know when the old cycle ends and the new cycle begins: sunspots begin forming in regions having a magnetic polarity reversed from that of the old cycle. Thus, the 11 year sunspot cycle is really only the visual part of a 22 year magnetic cycle on the Sun.
The Sun has been in an extended minimum for the last couple of years. The next sunspot cycle should have started about a year ago, if the normal pattern held. However, scientists at the National Center for Atmospheric Research (NCAR) predicted that this next cycle would be delayed by about a year, and would be 30% to 50% more active than the previous cycle. That is significant because the same magnetic activity that causes sunspots causes solar flares and coronal mass ejections that can trigger geomagnetic storms. These geomagnetic storms can affect communications, power transmission, and navigation systems. They can also disrupt, or even disable, satellites and spacecraft, and the radiation associated with this activity can have adverse effects on aircraft crew and passengers. The radiation storms can even be life threatening for astronauts caught unprotected by Earth’s magnetic field, such as astronauts on a lunar mission.
Last month, solar astronomers noticed a region of reversed magnetic field forming on the Sun, as shown in the following image and magnetogram. This active region signaled the first of the activity for the 24th Cycle. However, the active region didn’t generate any sunspots, so it wasn’t declared the beginning of the new cycle.
But, finally, a sunspot was found, labeled 0981 in the image at the top of this posting, that in the following magnetogram was shown to be in a region of reversed magnetic field. It is the first definite sunspot of the 24th Cycle. So, the new cycle is starting, nearly a year late. That suggests that the NCAR team in Boulder may be right about this being a significantly active sunspot cycle. If that is the case, then it would be one of the most active cycles in recent decades. It would certainly be the most active since we became nearly dependent upon satellite communications, navigation, and observations. Remember that geomagnetic storms and solar radiation storms can interfere with satellite operations.
If this is indeed the beginning of a new cycle, then don’t expect the Sun to be covered in sunspots at once. It takes a few years for the Sun to ramp up to maximum. The peak will not be until about 2012. But, it is also important to note that sometimes the biggest solar flares and most powerful geomagnetic storms occur on the downslope of the solar cycle, and that would be for several years after 2012. This is only the first sunspot of the new cycle, so we’ll have to wait to see how the predictions pan out. It might be interesting.
-Astroprof
Images courtesy of NASA, SOHO
Ole Phat Stu on January 7, 2008 at 9:59 am: 1
Maxing in 2012 eh?
When the Aztek calender comes to its end?
Duck’n'cover!
Astroprof’s Page » A Long, Quiet Solar Minimum on July 11, 2008 at 3:22 pm: 2
[…] Sun is at solar minimum right now. It is supposed to be at a lull of sunspot activity. And, as I wrote a few months ago, the next sunspot cycle is already showing signs of getting started. It just […]