How to forecast a solar outburst
Powerful eruptions from the sun can trigger magnetic storms on Earth that can cause power blackouts and disrupt radio communications. And they can also trigger radiation storms in space that may damage satellites and threaten astronauts.
Now, a team of scientists has found that these powerful outbursts, known as coronal mass ejections (CMEs), emit telltale radio signals. The signals travel at the speed of light – far faster than the billions of tons of hot, electrically charged gas that CMEs hurl through space. As a result, the signals can be used to provide earlier warnings of impending magnetic or radiation storms. The lead time can range from tens of minutes to a few hours, according to Natchimuthuk Gopalswamy, a scientist at NASA's Goddard Space Flight Center in Greenbelt, Md., who led the team.
The team discovered the link between CMEs and their radio signals by using two sun-watching spacecraft, each with different sets of instruments. The team looked at 472 CMEs the two craft captured between 1996 and 2005 and teased out the correlation between storm-producing CMEs and their radio "screams." The team presented its results at this week's spring meeting of the American Astronomical Society in Honolulu.
Ants: selfless road workers
Army ants have evolved an effective way to patch potholes in their paths: They pile into the gap to smooth the way for their comrades.
That's the story two University of Bristol researchers tell after studying army ants (Eciton burchellii) from the rain forests of Central and South America. The ants – up to 200,000 at a time – sally forth to raid their surroundings for food. The ants form an unbroken stream between the vanguard and the nest back home. Foraging ants scurry back along the trail with prey they've captured. But when the homeward-bound ants approach a gap in the ground cover, other ants fill it in until the path is smooth. This hastens the return of food to the nest. Once the food-bearing ants pass, the living pothole patch leaves the gap and heads home, too.
The duo tested the process in the lab using wood containing holes of different sizes. If the holes were small enough for one ant to span, the ant whose size best matched the hole emerged to bridge it. If the hole was too large for any one ant, enough would come forward to fill it and smooth the way. The behavior allows far more food to reach the nests than would otherwise be the case; thus, the living pothole patches more than compensate for the fact that they don't carry prey themselves.
"When it comes to ants, they have their own do-it-yourself highways agency," says Nigel Franks, one of the two researchers. The study appears in the June issue of the journal Animal Behaviour.
Birds benefit from trees on farms
Just a few trees in an otherwise cleared patch of farmland can be a big help in preserving threatened tropical birds, a new study shows.
Researchers at Stanford University's Center for Conservation Biology reached this conclusion after trying to gauge the impact of forest loss on bird populations in Costa Rica. They conducted their work in a region where coffee plantations had replaced once-verdant rain forest. Previous studies found that the plantations appeared to host up to 200 species, suggesting that birds and coffee plants got along just fine. But those results were based on spotting birds as they flew through the plantation or were captured there. They said nothing about how much time the birds spent among the coffee plants. So a team led by Stanford scientist Cagan Sekercioglu captured birds, put radio tags on them, and then tracked their whereabouts over two seasons – eight months total.
They found that birds in the plantations actually spent much of their time in the few trees, or stands of trees along creeks and rivers, and not among the coffee plants themselves. The small patches of trees were critical to some of the birds, the team found. Thus, if farmers leave small stands of trees to dot their plantations, they could help preserve endangered bird species.
"Even modest restoration efforts ... can help these birds more than you would think," Dr. Sekercioglu says. The results appear in the April issue of the journal Conservation Biology.