* The start of [a new solar] cycle begins with a well-established dipole field component aligned along the solar rotational axis. The field lines tend to be held by the highly conductive solar plasma of the solar surface.
* The solar surface plasma rotation rate is different at different latitudes, and the rotation rate is 20 percent faster at the equator than at the poles (one rotation every 27 days). Consequently, the magnetic field lines are wrapped by 20 percent every 27 days.
* After many rotations, the field lines become highly twisted and bundled, increasing their intensity, and the resulting buoyancy lifts the bundle to the solar surface, forming a bipolar field that appears as two spots, being kinks in the field lines.
* The sunspots result from the strong local magnetic fields in the solar surface that exclude the light-emitting solar plasma and appear as darkened spots on the solar surface.
* The leading spot of the bipolar field has the same polarity as the solar hemisphere, and the trailing spot is of opposite polarity. The leading spot of the bipolar field tends to migrate towards the equator, while the trailing spot of opposite polarity migrates towards the solar pole of the respective hemisphere with a resultant reduction of the solar dipole moment. This process of sunspot formation and migration continues until the solar dipole field reverses (after about 11 years).
* The solar dipole field, through similar processes, reverses again at the end of the 22-year cycle.
* The magnetic field of the spot at the equator sometimes weakens, allowing an influx of coronal plasma that increases the internal pressure and forms a magnetic bubble which may burst and produce an ejection of coronal mass, leaving a coronal hole with open field lines. Such a coronal mass ejections are a source of the high-speed solar wind.
* The fluctuations in the bundled fields convert magnetic field energy into plasma heating, producing emission of electromagnetic radiation as intense ultraviolet (UV) and X-rays."
http://en.wikipedia.org/wiki/Babcock_Model
_________________________________________________
"Different parts of the Sun rotate at different speeds. The Sun's equator spins fastest, and the poles spin more slowly. This causes the Sun's magnetic field to get all tangled up over time. Loops in the tangled magnetic field poke through the Sun's surface sometimes. When they do, they make sunspots."
Windows to the Universe original artwork.
http://www.windows.ucar.edu/tour/link=/sun/Solar_interior/Sun_layers/differential_rotation.html
_________________________________________________
From March of 2008...
"New solar cycles always begin with a high-latitude, reversed polarity sunspot. High latitude refers to the Sun's grid of latitude and longitude; old sunspots congregate near the Sun's equator and new sunspots appear higher, at around 25-30 degrees latitude. Reversed polarity means a sunspot with opposite magnetic polarity compared to sunspots from the previous solar cycle, such as the one detected on the 4 January this year. However, Solar Cycle 23 has not yet ended, and it may run concurrently with the new cycle for up to a year while sunspots from the old cycle become less numerous."
http://www.astronomynow.com/news/080304solarcycle/
_________________________________________________
"The physical basis of the solar cycle was elucidated in the early twentieth century by George Ellery Hale and collaborators, who in 1908 showed that sunspots were strongly magnetized (this was the first detection of magnetic fields outside the Earth), and in 1919 went on to show that the magnetic polarity of sunspot pairs:
* Is always the same in a given solar hemisphere throughout a given sunspot cycle;
* Is opposite across hemispheres throughout a cycle;
* Reverses itself in both hemispheres from one sunspot cycle to the next.
Hale's observations revealed that the solar cycle is a magnetic cycle with an average duration of 22 years. However, because very nearly all manifestations of the solar cycle are insensitive to magnetic polarity, it remains common usage to speak of the "11-year solar cycle". ..."
http://en.wikipedia.org/wiki/Solar_cycle
_________________________________________________
Solar Cycle 24 Begins
"On January 4, 2008, a reversed-polarity sunspot appeared—and this signals the start of Solar Cycle 24," says David Hathaway of the Marshall Space Flight Center.
Solar activity waxes and wanes in 11-year cycles. Lately, we've been experiencing the low ebb, "very few flares, sunspots, or activity of any kind," says Hathaway. "Solar minimum is upon us."
The previous solar cycle, Solar Cycle 23, peaked in 2000-2002 with many furious solar storms. That cycle decayed as usual to the present quiet leaving solar physicists little to do other than wonder, when would the next cycle begin?
The answer is now [Jan 4, 2008].
"New solar cycles always begin with a high-latitude, reversed polarity sunspot," explains Hathaway. "Reversed polarity" means a sunspot with opposite magnetic polarity compared to sunspots from the previous solar cycle. "High-latitude" refers to the sun's grid of latitude and longitude. Old cycle spots congregate near the sun's equator. New cycle spots appear higher, around 25 or 30 degrees latitude.
The sunspot that appeared on January 4th fits both these criteria. It was high latitude (30 degrees N) and magnetically reversed. NOAA named the spot AR10981, or "sunspot 981" for short.
http://science.nasa.gov/headlines/y2008/10jan_solarcycle24.htm
_________________________________________________
N/S = North South magnetic polarity