Gamma-ray Flashes & Storms

Thunderstorms create about a 1000 quick bursts of gamma rays (i.e., high energy light on Earth). Recent data from NASA's Fermi Gamma-ray Space Telescope compared to ground-based radar and lightning detectors, gave scientists detailed information on the different types of thunderstorms and their produced energy.

Terrestrial gamma-ray flashes (TGFs), were discovered in the 1990s by NASA's Compton Gamma-Ray Observatory. TGFs, lasting less than a thousandth of a second, are poorly understood.

"Remarkably, we have found that any thunderstorm can produce gamma rays, even those that appear to be so weak a meteorologist wouldn't look twice at them," said Themis Chronis, who led the research at the University of Alabama in Huntsville (UAH).

The Fermi data, combined with info from ground-based radar and lightning, shows that terrestrial gamma-ray flashes come from a diversity of storms and may be more common than earlier expectations. In fact, the upper part of an intracloud lightning bolt disrupts the storm's electric field creating an avalanche of electrons that surge upward at high speed. These fast-moving electrons are deflected by air molecules and emit gamma rays, creating a TGF.  


The new study confirms previous findings that TGFs tend to occur near the highest parts of a thunderstorm, between about 7 and 9 miles (11 to 14 kilometers) high.

As climate change unfolds, it will be interesting to see if TGFs increase or decrease with storms. I'm sure the Fermi folks will keep an eye to the skies. Go science!

Stalagmites - Time Capsules of Climate Change

As the Earth's climate continues to shift bringing drought to some areas and record snowfall to others, scientists are constantly searching for new ways to monitor and model the data.

So, you can imagine the excitement generated when cave stalagmites in Borneo (video) were sampled and found to mirror some large climatic events, but not others. Located just north of the equator in the Pacific, the region is a big climate player. By sampling the stalagmite's historical record, scientists can obtain previously unknown data that may offer hints to puzzling climate questions. 

“To my knowledge, this is the first record that so clearly shows sensitivity to one set of major abrupt climate change events and not another,” explains Kim Cobb, an associate professor in the School of Earth and Atmospheric Sciences at the Georgia Institute of Technology. 

Rock strata (layers) like those seem in the Grand Canyon have been studied by geologists for a long time, but these new stalagmite records have the added benefit of limited or no erosion. They also provide information on the water minerals present during past climate shifts.