Monday, April 20, 2009

Saturday, April 18, 2009


This image provided by the European Space Agency shows and artist impression of catalogued objects in low-Earth orbit viewed over the Equator. Scientists are keeping a close eye on orbital debris created when two communications satellites _ one American, the other Russian _ smashed into each other hundreds of miles above Siberia Tuesday Feb. 10, 2009. The collision was the first high-speed impact between two intact spacecraft, NASA officials said. The debris field shown in this image is an artist's impression based on actual data but not shown in their actual size or density. (AP Photo/ESA)

24 solar cycle

"On January 4, 2008, a reversed-polarity sunspot appeared—and this signals the start of Solar Cycle 24," says David Hathaway of the Marshall Space Flight Center.

Above: Images of the first sunspot of Solar Cycle 24 taken by the NASA/ESA Solar and Heliospheric Observatory (SOHO).
The sunspot that appeared on January 4th fits both these criteria. It was high latitude (30 degrees N) and magnetically reversed. NOAA named the spot AR10981, or "sunspot 981" for short.
Sunspot 981 was small--only about as wide as Earth, which counts as small on the grand scale of the sun--and it has already faded away. But its three day appearance on Jan. 4-6 was enough to convince most solar physicists that Solar Cycle 24 is underway.
Doug Biesecker of NOAA's Space Weather Prediction Center in Boulder, Colorado, likens sunspot 981 "to the first robin of spring. There's still snow on the ground, but the seasons are changing." Last year, Biesecker chaired the Solar Cycle 24 Prediction Panel, an international group of experts from many universities and government agencies. "We predicted that Solar Cycle 24 would begin around March 2008 and it looks like we weren't far off," he says.
"Solar storms can disable satellites that we depend on for weather forecasts and GPS navigation," says Hathaway. Radio bursts from solar flares can directly interfere with cell phone reception while coronal mass ejections (CMEs) hitting Earth can cause electrical power outages. "The most famous example is the Quebec outage of 1989, which left some Canadians without power for as much as six days."
Air travel can be affected, too.
Strange but True: While Solar Cycle 24 has begun, Solar Cycle 23 has not ended. Both cycles will coexist for a period of time, perhaps a year or more, as one dies down and the other comes to life. In the months ahead we may see old-cycle sunspots and new-cycle sunspots on the sun at the same time.
Much of this is still years away. "Intense solar activity won't begin immediately," notes Hathaway. "Solar cycles usually take a few years to build from solar minimum (where we are now) to Solar Max, expected in 2011 or 2012."
It's a slow journey, but we're on our way.

read the full article at science@nasa link is given below....

Earth's magnetic poles shifting

left: The movement of Earth's north magnetic pole across the Canadian arctic, 1831--2001. Credit: Geological Survey of Canada.
Scientists have long known that the magnetic pole moves. James Ross located the pole for the first time in 1831 after an exhausting arctic journey during which his ship got stuck in the ice for four years. No one returned until the next century. In 1904, Roald Amundsen found the pole again and discovered that it had moved--at least 50 km since the days of Ross.
The pole kept going during the 20th century, north at an average speed of 10 km per year, lately accelerating "to 40 km per year," says Newitt. At this rate it will exit North America and reach Siberia in a few decades.
Keeping track of the north magnetic pole is Newitt's job. "We usually go out and check its location once every few years," he says. "We'll have to make more trips now that it is moving so quickly."
Earth's magnetic field is changing in other ways, too: Compass needles in Africa, for instance, are drifting about 1 degree per decade. And globally the magnetic field has weakened 10% since the 19th century. When this was mentioned by researchers at a recent meeting of the American Geophysical Union, many newspapers carried the story. A typical headline: "Is Earth's magnetic field collapsing?"
Probably not. As remarkable as these changes sound, "they're mild compared to what Earth's magnetic field has done in the past," says University of California professor Gary Glatzmaier.
ometimes the field completely flips. The north and the south poles swap places. Such reversals, recorded in the magnetism of ancient rocks, are unpredictable. They come at irregular intervals averaging about 300,000 years; the last one was 780,000 years ago. Are we overdue for another? No one knows.
Above: Magnetic stripes around mid-ocean ridges reveal the history of Earth's magnetic field for millions of years. The study of Earth's past magnetism is called paleomagnetism. Image credit: USGS. [More]
According to Glatzmaier, the ongoing 10% decline doesn't mean that a reversal is imminent. "The field is increasing or decreasing all the time," he says. "We know this from studies of the paleomagnetic record." Earth's present-day magnetic field is, in fact, much stronger than normal. The dipole moment, a measure of the intensity of the magnetic field, is now 8 x 1022 amps x m2. That's twice the million-year average of 4 x 1022 amps x m2.
To understand what's happening, says Glatzmaier, we have to take a trip ... to the center of the Earth where the magnetic field is produced.
At the heart of our planet lies a solid iron ball, about as hot as the surface of the sun. Researchers call it "the inner core." It's really a world within a world. The inner core is 70% as wide as the moon. It spins at its own rate, as much as 0.2o of longitude per year faster than the Earth above it, and it has its own ocean: a very deep layer of liquid iron known as "the outer core."
A schematic diagram of Earth's interior. The outer core is the source of the geomagnetic field.
Earth's magnetic field comes from this ocean of iron, which is an electrically conducting fluid in constant motion. Sitting atop the hot inner core, the liquid outer core seethes and roils like water in a pan on a hot stove. The outer core also has "hurricanes"--whirlpools powered by the Coriolis forces of Earth's rotation. These complex motions generate our planet's magnetism through a process called the dynamo effect.

Using the equations of magnetohydrodynamics, a branch of physics dealing with conducting fluids and magnetic fields, Glatzmaier and colleague Paul Roberts have created a supercomputer model of Earth's interior. Their software heats the inner core, stirs the metallic ocean above it, then calculates the resulting magnetic field. They run their code for hundreds of thousands of simulated years and watch what happens.
What they see mimics the real Earth: The magnetic field waxes and wanes, poles drift and, occasionally, flip. Change is normal, they've learned. And no wonder. The source of the field, the outer core, is itself seething, swirling, turbulent. "It's chaotic down there," notes Glatzmaier. The changes we detect on our planet's surface are a sign of that inner chaos.
They've also learned what happens during a magnetic flip. Reversals take a few thousand years to complete, and during that time--contrary to popular belief--the magnetic field does not vanish. "It just gets more complicated," says Glatzmaier. Magnetic lines of force near Earth's surface become twisted and tangled, and magnetic poles pop up in unaccustomed places. A south magnetic pole might emerge over Africa, for instance, or a north pole over Tahiti. Weird. But it's still a planetary magnetic field, and it still protects us from space radiation and solar storms.

Supercomputer models of Earth's magnetic field. On the left is a normal dipolar magnetic field, typical of the long years between polarity reversals. On the right is the sort of complicated magnetic field Earth has during the upheaval of a reversal.
And, as a bonus, Tahiti could be a great place to see the Northern Lights. In such a time, Larry Newitt's job would be different. Instead of shivering in Resolute Bay, he could enjoy the warm South Pacific, hopping from island to island, hunting for magnetic poles while auroras danced overhead.
Sometimes, maybe, a little change can be a good thing.

Feature Author: Dr. Tony Phillips
Feature Production Editor: Dr. Tony Phillips
Feature Production Credit: Science@NASA

inf. taken from NASA website click below link for more inf._

Sunday, April 5, 2009


This Earth day, remind the people in your life that it's time protect and cherish our planet. Send a free eCard and with each one sent Care2 will donate money to save a square foot of rainforest. You can make a difference!