Tuesday, September 30, 2008

The sun is the same in a relative way...

The sun is going through its "blankest" year in a long time.

There have been no sunspots out of 200 of the past 274 days. The sun goes through 11 years cycles of activity, and is at the nadir of the current cycle. Our star hasn't been this placid in 50 years.

Astronomers have also noticed that the sun is dimmer than ever. Its luminosity is only declined a fraction of a percent, but in solar terms, that's a lot of energy.

No one knows why sunspots erupt on the solar surface. The sun has a strong magnetic field, probably caused by its rotation. Since the enormous thermonuclear reaction is a ball of plasma, it does not spin like a solid object.

Different latitudes and depths move at different speeds. A spot on the equator makes a complete rotation every 25 days. All of these different layers produce a powerful magnetic field, that also rotates, until the field gets all tangled up and reaches a breaking point.

When the field breaks through the surface we see sunspots, which are up swellings of cooler material from the sun's interior. All of this wrapping and snapping is what is believed to lie behind the sunspot cycle.

Why so quiet? No one knows. It's not as if the sun is running out of fuel. The sun still has about 5 billion years of hydrogen left.

What effect, if any, the dimming is having on Earth's climate is also not known. Maybe in a few decades we'll be burning any organic material we can get our hands on to generate enough greenhouse gas to melt a little of the global ice sheet.

1 comment:

  1. What does this sentence mean?

    "No one knows what sunspots erupt on the solar surface."

    By the way, it is worth noting that the biggest solar cycle (in terms of number of sunspots during the peak years) in recorded history was Cycle 19, peaking around 1957-1959, and it was HUGE.

    But you know what preceded Cycle 19? A solar minimum so long and deep that in terms of the number of spotless days, it is 40% ahead (so far) of the current minimum.

    Think about that when someone (somehow it is never actually anyone involved in solar research who makes this claim) says current activity predicts decades of no sunspots, or another Maunder Minimum.

    I think the folks promoting this idea are global warming skeptics who are also promoting the mistaken notion that sunspot activity correlates well with climate, which it does not: