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SPACE STATION SIGHTINGS:
The International Space Station and space
shuttle Discovery have entered the evening skies of North America.
Docked together, they are brighter than any star in the sky, so
you won't want to miss a single apparition. Check the Simple
Satellite Tracker for flybys.
images: from
Paul Martini of Joshua Tree National Park, California; from
Jonathan Sabin of Ellenton, Florida; from
Jerry Chab of Falls City, Nebraska; from
Ben Cooper of East Hampton, New York; from
Paco Bellido of Córdoba, Spain; from
Ron Hodges of Midland Texas;
ROCKETING PLASMA BLOB:
Solar activity is low, but it's not zero.
Consider the following: On Sept. 5th, Jean-Paul Godard of Paris,
France, was watching some prominences gently wave over the edge
of the sun when, suddenly, a plasma blob rocketed into view:
"I've never seen a fast ejection like this before,"
says Godard. "I recorded the
action using a 3-inch refracting telescope and a Coronado SolarMax
filter."
The blob does not appear to have escaped the sun.
Indeed, it might not have been a blob at all, but rather a plasma
wave traveling up a magnetic flux tube--and 'breaking'
when it reached the top. Whether it was a rocketing blob or breaking
wave, it shows that even the quiet sun is worth watching. Monitoring
is encouraged.
more images: from
Alan Friedman of Buffalo, New York; from
Cai-Uso Wohler of Bispingen, Germany; from
Francisco A. Rodriguez of Cabreja Mountain Observatory, Canary
Islands; from
Jimmy Eubanks of Boiling Springs, South Carolina; from
Pavol Rapavy of Observatory Rimavska Sobota, Slovakia;
SOLAR MINIMUM VS.
GLOBAL WARMING: From 2002 to 2008, decreasing
solar irradiance has countered much anthropogenic warming of Earth's
surface. That's the conclusion of researchers Judith Lean (NRL)
and David Rind (NASA/GISS), who have just published a new analysis
of global temperatures in the Geophysical Research Letters.
Lean and Rind considered four drivers of climate change: solar activity,
volcanic eruptions, ENSO (El Nino), and the accumulation of greenhouse
gases. The following plot shows how much each has contributed to
the changing temperature of Earth's surface since 1980:
Volcanic aerosols are a source of cooling; ENSO and greenhouse
gases cause heating; the solar cycle can go either way. When added
together, these factors can account for 76% of the variance in Earth's
surface temperature over the past ~30 years, according to the analysis
of Lean and Rind.
Several aspects of their model attract attention: "The warmest
year on record, 1998, coincides with the 'super-El Nino' of 1997-98,"
points out Lean. "The ESNO is capable of producing significant
spikes in the temperature record." Solar minimum has the opposite
effect: "A 0.1% decrease in the sun's irradiance has counteracted
some of the warming action of greenhouse gases from 2002 - 2008,"
she notes. "This is the reason for the well-known 'flat' temperature
trend of recent years."
What's next? Ultimately, the authors say, temperatures will begin
rising again as greenhouse gases accumulate and solar activity resumes
with the coming of the next solar cycle. Of couse, the solar cycle
could be out
of whack; if solar minimum deepens and persists, no one is certain
what will happen. Lean and Rind reveal their predictions
for the future here.
Reference: Lean, J. L., and D. H. Rind (2009),
How will Earth's surface temperature change in future decades?,
Geophys. Res. Lett., 36, L15708
August
2009 Aurora Gallery
[previous Augusts: 2008,
2007, 2006,
2005, 2004,
2003, 2002,
2001]
Explore
the Sunspot Cycle
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