Astronuc said:
The sun is apparently in a 'deep' or prolonged minimum right now. Activity should start to pick up this month or perhaps during August.
This solar min has in a sense set solar science back to the drawing board. Back in 2006 solar scientists predicted that cycle 24 would be strong and that they would "see the first sunspots of the next cycle appear in late 2006 or 2007—and Solar Max to be underway by 2010 or 2011" (http://science.nasa.gov/headlines/y2006/10mar_stormwarning.htm ).
The observation of a short-lived "backward sunspot" on July 31, 2006 (http://science.nasa.gov/headlines/y2006/15aug_backwards.htm ) led David Hathaway to claim that the next cycle, Solar Cycle 24, should begin "any time now".
That sunspot was too short-lived to be deemed worthy of even a sunspot number. It took another year and a half before the first cycle 24 sunspot was seen (http://science.nasa.gov/headlines/y2008/10jan_solarcycle24.htm ). The uptick expected to be seen in 2007 didn't happen. Then in didn't happen in 2008. Cycle 24 was very slow to start, and cycle 23 was hanging on (http://science.nasa.gov/headlines/y2008/28mar_oldcycle.htm ). Maybe some signs of life in November 2008 (http://science.nasa.gov/headlines/y2008/07nov_signsoflife.htm )?
Nope. Solar activity has remained very low for the first half of 2009. The latest sign of life was a sunspot that struggled to form (but failed to do so) on July 24. One problem: It's polarity makes it a member of solar cycle 23 (
http://www.spaceweather.com/archive.php?view=1&day=24&month=07&year=2009, see the "Daily Sun" image).
If the activity follows previous trends then the reversal should start sometime during the latter half of 2011.
That boat (activity following previous trends) has already sailed. NASA is much less confident in its predictions:
An international panel of experts led by NOAA and sponsored by NASA has released a new prediction for the next solar cycle. Solar Cycle 24 will peak, they say, in May 2013 with a below-average number of sunspots.
...
"It turns out that none of our models were totally correct," says Dean Pesnell of the Goddard Space Flight Center, NASA's lead representative on the panel. "The sun is behaving in an unexpected and very interesting way."
Right now, the solar cycle is in a valley--the deepest of the past century. In 2008 and 2009, the sun set Space Age records for low sunspot counts, weak solar wind, and low solar irradiance. The sun has gone more than two years without a significant solar flare.
"In our professional careers, we've never seen anything quite like it," says Pesnell. "Solar minimum has lasted far beyond the date we predicted in 2007."
(http://science.nasa.gov/headlines/y2009/29may_noaaprediction.htm )
I couldn't find a nice concise process outline, i.e., when the reversal begins, how long the process lasts, and when it is considered to be completed. Apparently it takes weeks, based on what I discern from the 'butterfly' plots.
The magnetic butterfly diagrams give a better picture of the magnetic field than do the sunspot charts. See
http://solarscience.msfc.nasa.gov/images/magbfly.jpg.
(The 1024x600 image is a bit too large for inclusion directly.) It looks like it takes a year or so for the field at the poles to flip.
I am curious about the significance of the current 'deep' or prolonged miniumum. Does it mean that the return to maximum will be steeper than usual, or that the next maximum will be much stronger than usual?
Some solar scientists are proclaiming that this very prolonged minimum represents the start of a Dalton-style, maybe even a Maunder-style minimum. Time will tell.
