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Samstag, 20. Juni 2009 um 00:00 Uhr |
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While some are already speculating about a defective solar dynamo and a new Maunder minimum upon us, real solar physicists have taken data instead on what's really going on underneath the solar photosphere. And on June 17 they've come up with answers. Scientists from the National Solar Observatory (NSO) in Tucson, Arizona, have discovered that a solar jet stream deep inside the Sun is migrating slower than usual through the star's interior, giving rise to the current lack of sunspots and low solar activity.
They used long-term observations from the Global Oscillation Network Group (GONG) facility to detect and track an east-to-west jet stream, known as the "torsional oscillation", at depths of ~1000 to 7000 km below the surface of the Sun. The Sun generates new jet streams near its poles every 11 years; the streams migrate slowly, over a period of 17 years, to the equator, and are associated with the production of sunspots once they reach a critical latitude of 22 degrees.
The researchers found that the stream associated with the new solar cycle has moved sluggishly, taking three years to cover a 10 degree range in latitude compared to two years for the last solar cycle, but has now reached the critical latitude. The current solar minimum has become so long and deep, some scientists have speculated the Sun might enter a long period with no sunspot activity at all. The new result both shows that the Sun's internal magnetic dynamo continues to operate, and heralds the beginning of a new cycle of solar activity. Just as this sluggish stream reaches the usual active latitude of 22°, a year late, we finally begin to see new groups of sunspots emerging at the new active latitude. Since the current minimum is now one year longer than usual, the extended solar minimum phase may have resulted from the slower migration of the flow.
You can find Daniel Fischers Cosmic Mirror here. |
