LARGE SPOT GROUP photographed on Nov. 4, 1980 at the start of Cycle 21. Will the current cycle witness any similar large spots?
There has been so much babble written concerning solar cycle 24 (the alleged "missing cycle") that itemizing it all would take the better part of a day. Suffice it to say that being able to attend the 40th meeting of the Solar Physics Division definitely helped in clarifying the issues, especially in terms of holding back the sea of codswallop that has been churned out recently by global warming deniers.
Most of these have latched on to solar cycle 24 as an escape hatch, reasoning that because the Maunder Minimum was effectively a missing cycle (few or no spots) and ushered in a brutally much colder span of ~ 70 years, than the same may be true now. And then, because of this assumed new "minimum" we shall not have to fret over carbon-based human engendered warming!
Not so fast!
The papers that were delivered more than showed this viewpoint to be baseless. Also, the extrapolations to a "new Maunder minimum" (or any significant minimum) premature and unjustified.
First, look at comparative spotless days. As noted by Prof. Frank Hill in his Tuesday morning lecture 'A Helioseismic Comparison of the Solar Minima Preceding Cycles 23 and 24', the current cycle is not yet exceptional - certainly in terms of spotless days aggregated.
While 286 total spotless days have been accumulated in 2008, and 128 so far this year, there have been other years with more, including: 311 spotless says in 1913, and 287 spotless days for 1901.
At the same time, it is also true that we currently have the lowest solar wind pressure since cycle 15, as well as the lowest irradiance in the modern (space observation) era. However, this is not as low as that recorded for cycles 13-14.
As for climate issues, what about the assumption that few or no spots for cycle 24 mean it will be overall weaker than cycle 23, and hence portend colder temperatures?
This case also can't be made, since we have the example of a very weak cycle (16) which led to a much more energetic and active one (cycle 17). Thus, cycle 24 could actually turn out to be very active cycle with higher solar irradiance that actually reinforces man-made global warming as opposed to cancelling it.
What we do know is that the behavior of cycle 24 appears to pose more serious questions for solar dynamo theory. This is the theory that every 11 years or so, magnetic fields on the Sun attain a high torsional component which causes them to "twist" up and also move from more northerly to more southerly solar latitudes where most active regions (ARs) form. Typically, this is around 22-23 heliographic degrees.
So far, the torsional oscillation flow for the current cycle is hovering near helio latitude 33 degrees, nearly 10 degrees off. Even moving at about 7 Mm (mega-meters or 10^6 meters) a year southward, this will take over 2 years to reach a latitude of 23 degrees, where large active regions (and spots!) ought to form.
Clearly, the solar dynamo needs refining, and certainly basic concepts such as the emergence of tachoclines, and the meriodonal flows inside the Sun.
To show how amiss we are, one paper presented displayed beautiful, multi-layered cross sectional views of the meriodonal flows in full color. But when the presenter was asked to show the actual observational data that supported it, nearly ninety-five percent of the colored lines and contours vanished! Clearly, there's a lot of unwarranted extrapolation.
For their part, the torsional oscillations tend to occur about 1000 kilometers below the Sun's surface (photosphere) but we have few instruments that can actually probe that deeply. One refrain one heard over and over in terms of supporting dynamo theory was: 'We need more money!'
If nothing else, and I propose extreme caution here- superior instruments (say designed for solar "sounding") might help to discriminate between the classical (e.g. Babcock-Leighton) dynamo theory and new ones involving "shallow" dynamos. In the latter case, ephemeral photospheric regions (EPRs) might be the first phenomena to be accounted for much in advance of actual sunspots seen as "inverse ion hurricanes". (EPRs, as the name implies, are not very stable or long lasting, usually appearing as small pores, then vanishing in 1-2 days)
In order to work then, a proper shallow dynamo theory needs to present sufficient observations to back up the supposition that a super-adiabatic temperature gradient is largest near the surface and its associated latent energy supports the reaction:
H + (energy) -> H+ + e(-) [ionization of hydrogen]
As is known from the standard (sunspot) theory of Parker, the "inverse ion hurricane" represented by a large sunspot enables the basis for the latent energy to translate into a convective collapse process so the luminosity can flow out and around the periphery of spots. The larger the spot (such as the one shown in the image, which I photographed in McMath region 17244 on Nov. 4, 1980) the greater the luminosity and heat discharged.
This is why the more spots there are in a cycle, the higher the solar irradiance, and the higher the mean global temperature of Earth. (One can get variations up to 0.21 K or more). This is often counter intuitive, since spots are actually cooler regions in relation to the Sun's surrounding photosphere, which is roughly 1500 K hotter.
The bottom line is there is much more to learn, and we need more money ....yes, but this must go to better actual instruments to plumb the solar depths...not merely for more sophisticated computers to do more numerical simulations!
In the meantime, we shall keep a close and wary eye on cycle 24 (which is actually interphased with the remnants or last gasps of cycle 23- so the current minimum is technically the "minimum of cycle 23 and 24") to see whether it portends a prolonged era of few or no spots (and hence lower solar irradiance) or much higher spot activity. In which case we had better start from now to induce massive changes in human behavior to lower carbon dioxide emissions!
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