The solar upheavals...

So, what is the current thinking on how the sun can suddenly become more
active than in the so called 11 year max? Is it just that nobody really
knows what the 11 year cycle is about, or is there more to it than that?

I thought the solar cycles were indirectly attributed to the flip of the
suns magnetic field, probably due to the effects of turbulence in a hot
rotating body which obviously is generating currents and hence the field.

If the spots are still active as the sun rotates back around, as it were,
it will be interesting to see if it is still spewing stuff out.

is there any spacecraft able to see the far side to know if the CMEs are
going on when the spots are out of sight?

Brian

--
Brian Gaff....
graphics are great, but the blind can't hear them
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In article ,
Brian Gaff wrote:
So, what is the current thinking on how the sun can suddenly become more
active than in the so called 11 year max? Is it just that nobody really
knows what the 11 year cycle is about, or is there more to it than that?

The cycle is not a smooth, predictable curve; there is a lot of randomness
(or what looks like randomness, anyway) superimposed on the cycle. Some
of this may be easier to figure out after we've seen a few dozen cycles --
we have good data on only about four so far.

is there any spacecraft able to see the far side to know if the CMEs are
going on when the spots are out of sight?

Alas, we have no solar imaging from the far side. There is some indirect
information available; in particular, one or two of SOHO's instruments can
see seismic effects from major events on the far side, when conditions are
right.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |

"Brian Gaff" writes:

So, what is the current thinking on how the sun can suddenly become more
active than in the so called 11 year max?

1.) Large solar flares can happen at any time of the solar cycle.
They are simply more _likely_ near the maximum, just as large floods
can happen during any time of the year, but are more likely during
the rainy season. (Also like floods, no matter how large the rare
"recordbreaker" is, it will eventually be broken by another large,
rare, extreme event; such is the nature of extreme-value statistics.)

2.) It has only been three years since the last maximum.

3.) Solar maxima are not that sharply peaked.

See http://science.nasa.gov/ssl/pad/solar/sunspots.htm, for example.


Is it just that nobody really knows what the 11 year cycle is about,
or is there more to it than that?

No, there is rather _less_ to it than that --- see my three points above.



I thought the solar cycles were indirectly attributed to the flip of the
suns magnetic field, probably due to the effects of turbulence in a hot
rotating body which obviously is generating currents and hence the field.

It is basically a "feedback" oscillation. Sunspots are basically anti-cyclonic
"storms" in the Sun's lower atmosphere, which carry "ropes" of poloidal
magnetic flux (and angular momentum) from the Sun's poles to its equator,
where they "reconnect" with the opposite flux carried down from the other pole;
this flux-transport process is somewhat analogous to how cyclones carry
angular momentum and heat and water-vapor from the Earth's equator to its
poles (the direction is reversed because the Suns pole's are hotter than
its equator, not colder, as on the Earth). The flux-transport process
also build up toroidal fluxes in the Sun's mid-latitudes, which are
somewhat analogous to the Earth's jet-streams; these mid-latitude toriodal
fluxes are converted into poloidal fluxes by upwelling cyclonic disturbances
in the high-latitude regions, which regenerate the poloidal magnetic field,
except with opposite sign. See the discussion at:
http://science.nasa.gov/ssl/pad/solar/dynamo.htm.


If the spots are still active as the sun rotates back around, as it were,
it will be interesting to see if it is still spewing stuff out.

It is highly likely that it still will be; this process has been oberved
many times before.


is there any spacecraft able to see the far side to know if the CMEs are
going on when the spots are out of sight?

Not generally; however, it is no longer neccesary to have such spacecraft
to obeserve when a solar flare occurs. Helioseismology allows us to
"see through the Sun," just as ordinary seismology allows us to
"see through the Earth." CMEs are generally associated with Solar flare
activity, and solar flares on the opposite side of the Sun generate
helioseismic disturbances that propagate right through the Sun, and
that can be observed on this side of the Sun. See:
http://antwrp.gsfc.nasa.gov/apod/ap010503.html;
for technical details, see:
http://soi.stanford.edu/press/ssu03-00/backside_paper/lindsey.pdf.


-- Gordon D. Pusch

perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;'

www.spaceweather.com has a piece on these giant sunspots that recently
appeared. It seems they are still very active on the far side of the Sun.



THE FAR SIDE OF THE SUN: The three giant sunspots that caused so much space
weather in recent weeks are now on the far side of the sun. There are hints
that the three are still active. Witness these CMEs hurled over the sun's
limb by farside explosions: Nov. 6th, Nov. 7th, and Nov. 9th. Using a
technique called helioseismic holography, researchers can "see" a portion of
the sun's far side. In a few days their images should tell us if two of the
sunspots (486 and 488) are indeed still big. The sun's 27-day rotation is
carrying all three spots back toward the Earth-facing side of our star; the
first could reappear as early as Nov. 13th.

From http://www.spaceweather.com/:



THE FAR SIDE OF THE SUN: The three giant sunspots that caused so much space
weather in recent weeks are now on the far side of the sun. There are hints
that the three are still active. Witness these CMEs hurled over the sun's
limb by farside explosions: Nov. 6th, Nov. 7th, and Nov. 9th. Using a
technique called helioseismic holography, researchers can "see" a portion of
the sun's far side. In a few days their images should tell us if two of the
sunspots (486 and 488) are indeed still big. The sun's 27-day rotation is
carrying all three spots back toward the Earth-facing side of our star; the
first could reappear as early as Nov. 13th.