Tuesday, November 18, 2008

The Sun Shows Signs of Life

Nov. 7, 2008: After two-plus years of few sunspots, even fewer solar flares, and a generally eerie calm, the sun is finally showing signs of life.

"I think solar minimum is behind us," says sunspot forecaster David Hathaway of the NASA Marshall Space Flight Center.

His statement is prompted by an October flurry of sunspots. "Last month we counted five sunspot groups," he says. That may not sound like much, but in a year with record-low numbers of sunspots and long stretches of utter spotlessness, five is significant. "This represents a real increase in solar activity."

Above: New-cycle sunspot group 1007 emerges on Halloween and marches across the face of the sun over a four-day period in early November 2008. Credit: the Solar and Heliospheric Observatory (SOHO).

Even more significant is the fact that four of the five sunspot groups belonged to Solar Cycle 24, the long-awaited next installment of the sun's 11-year solar cycle. "October was the first time we've seen sunspots from new Solar Cycle 24 outnumbering spots from old Solar Cycle 23. It's a good sign that the new cycle is taking off."

Old Solar Cycle 23 peaked in 2000 and has since decayed to low levels. Meanwhile, new Solar Cycle 24 has struggled to get started. 2008 is a year of overlap with both cycles weakly active at the same time. From January to September, the sun produced a total of 22 sunspot groups; 82% of them belonged to old Cycle 23. October added five more; but this time 80% belonged to Cycle 24. The tables have turned.

At first glance, old- and new-cycle sunspots look the same, but they are not. To tell the difference, solar physicists check two things: a sunspot's heliographic latitude and its magnetic polarity. (1) New-cycle sunspots always appear at high latitude, while old-cycle spots cluster around the sun's equator. (2) The magnetic polarity of new-cycle spots is reversed compared to old-cycle spots. Four of October's five sunspot groups satisfied these two criteria for membership in Solar Cycle 24.

The biggest of the new-cycle spots emerged at the end of the month on Halloween. Numbered 1007, or "double-oh seven" for short, the sunspot had two dark cores each wider than Earth connected by active magnetic filaments thousands of kilometers long. Amateur astronomer Alan Friedman took this picture from his backyard observatory in Buffalo, New York:

On Nov. 3rd and again on Nov. 4th, double-oh seven unleashed a series of B-class solar flares. Although B-flares are considered minor, the explosions made themselves felt on Earth. X-rays bathed the dayside of our planet and sent waves of ionization rippling through the atmosphere over Europe. Hams monitoring VLF radio beacons noticed strange "fades" and "surges" caused by the sudden ionospheric disturbances.

Hathaway tamps down the excitement: "We're still years away from solar maximum and, in the meantime, the sun is going to have some more quiet stretches." Even with its flurry of sunspots, the October sun was mostly blank, with zero sunspots on 20 of the month's 31 days.

1 comment:

Francis T. Manns, Ph.D. said...

The third most important greenhouse gas is CO2, and it does not correlate well with global warming or cooling either; in fact, CO2 in the atmosphere trails warming which is clear natural evidence for its well-studied inverse solubility in water. CO2 dissolves in cold water and bubbles out of warm water. The equilibrium in seawater is 50, making seawater a great 'sink'; CO2 is 34 times more soluble in water than air is soluble in water.
Correlation is not causation to be sure. The causation has been studied, however, and while the radiation from the sun varies only in the fourth decimal place, the magnetism is awesome. As I understand it, the hypothesis of the Danish National Space Center goes as follows:
Active sun → enhanced magnetic and thermal flux = solar wind → geomagnetic shield response → less low-level clouds → less albedo (less heat reflected) → warmer climate
Quiet sun → reduced magnetic and thermal flux = reduced solar wind → geomagnetic shield drops → galactic cosmic ray flux → more low-level clouds and more snow → more albedo effect (more heat reflected) → colder climate
That is how the bulk of climate change might work, coupled with (modulated by) sunspot peak frequency there are cycles of global warming and cooling like waves in the ocean. When the waves are closely spaced, the planets warm; when the waves are spaced farther apart, the planets cool.
Check the web site of the Danish National Space Center.

Cyclicity in the Sun-Jupiter centre of gravity is likely the ultimate cause of the solar magnetic cycle. We await more on that. In addition, though the post 60s warming period is over, it has allowed that great green house gas, water vapour, to kick in with humidity, clouds, rain and snow to provide the negative feedback that scientists use to explain the 4+ billion year history of life on Earth. The planet heats and cools naturally and our gasses are the thermostat.