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Plasma Bullets Spark Northern Lights

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July 24, 2008: Duck! Plasma bullets are zinging past Earth.

That's the conclusion of researchers studying data from NASA's five THEMIS spacecraft. The gigantic bullets, they say, are launched by explosions 1/3rd of the way to the Moon and when they hit Earth—wow. The impacts spark colorful outbursts of Northern Lights called "substorms."

Right: A substorm of Northern Lights photographed from the window of an airplane over Hudson Bay, Canada, on Feb 27, 2008. Credit: Jeff Hapeman. [more]

"We have discovered what makes the Northern Lights dance," declares UCLA physicist Vassilis Angelopoulos, principal investigator of the THEMIS mission. The findings appear online in the July 24 issue of Science Express and in print August 14 in the journal Science.

The THEMIS fleet was launched in February 2007 to unravel the mystery of substorms, which have long puzzled observers with their unpredictable eruptions of light and color. The spacecraft wouldn't merely observe substorms from afar; they would actually plunge into the tempest using onboard sensors to measure particles and fields. Mission scientists hoped this in situ approach would allow them to figure out what caused substorms--and they were right.

The discovery came on what began as a quiet day, Feb 26, 2008. Arctic skies were dark and Earth's magnetic field was still. High above the planet, the five THEMIS satellites had just arranged themselves in a line down the middle of Earth’s magnetotail—a million kilometer long tail of magnetism pulled into space by the action of the solar wind.

Sign up for EXPRESS SCIENCE NEWS delivery That's when the explosion occurred.

A little more than midway up the THEMIS line, magnetic fields erupted, "releasing about 1015 Joules of energy," says Angelopoulos. "For comparison, that's about as much energy as a magnitude 5 earthquake."

Although the explosion happened inside Earth's magnetic field, it was actually a release of energy from the sun. When the solar wind stretches Earth's magnetic field, it stores energy there, in much the same way energy is stored in a rubber band when you stretch it between thumb and forefinger. Bend your forefinger and—crack!—the rubber band snaps back on your thumb. Something similar happened inside the magnetotail on Feb. 26, 2008. Over-stretched magnetic fields snapped back, producing a powerful explosion. This process is called "magnetic reconnection" and it is thought to be common in stellar and planetary magnetic fields.

The blast launched two "plasma bullets," gigantic clouds of protons and electrons, one toward Earth and one away from Earth. The Earth-directed cloud crashed into the planet below, sparking vivid auroras observed by some 20 THEMIS ground stations in Canada and Alaska. The opposite cloud shot harmlessly into space, and may still be going for all researchers know.

Above: An artist's concept of the THEMIS satellites lined up inside Earth's magnetotail with an explosion between the 4th and 5th satellites. [Larger image]

The THEMIS satellites were perfectly positioned to catch the shot.

"We had bulls-eyes on our solar panels," says THEMIS project scientist David Sibeck of NASA's Goddard Space Flight Center. "Four of the satellites were hit by the Earth-directed cloud, while the opposite cloud hit the fifth satellite." Simple geometry pinpointed the site of the blast between the 4th and 5th satellite or "about 1/3rd of the way to the Moon."

No damage was done to the satellites. Plasma bullets are vast, gossamer structures less dense than the gentlest wisp of Earth's upper atmosphere. They whoosh past, allowing THEMIS instruments to sample the cloud’s internal particles and fields without truly buffeting the satellite.

This peaceful encounter on the small scale of a spacecraft, however, belies the energy deposited on the large scale of a planet. The bullet-shaped clouds are half as wide as Earth and 10 times as long, traveling hundreds of km/s. When such a bullet strikes the planet, brilliant auroras and geomagnetic storms ensue.

Right: A collection of ground-based All-Sky Imagers (ASI) captures the aurora brightening caused by a substorm. Credit: NASA/Goddard Space Flight Center Scientific Visualization Studio. [animation]

"For the first time, THEMIS has shown us the whole process in action—from magnetic reconnection to aurora borealis," says Sibeck. "We are finally solving the puzzle of substorms."

The THEMIS mission is scheduled to continue for more than another year, and during that time Angelopoulos expects to catch lots more substorms--"dozens of them," he says. "This will give us a chance to study plasma bullets in greater detail and learn how they can help us predict space weather."

"THEMIS is not finished making discoveries," believes Sibeck. "The best may be yet to come."

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Author: Dr. Tony Phillips | Credit: Science@NASA

A REAL MIXED UP WEATHER PATTERN OVER THE MID-WEST--WITH A NORTHWEST FLOW IN THE UPPER ATMSOPHERE AND A SOUTHERLY FLOW AT THE SURFACE...RESULTING IN A VERY HUMID WEATHER PATTERN WITH WAVES OF RAIN AND STORMS DROPPING DOWN IN THE NORTHWEST FLOW--WE WILL STAY IN THIS PATTERN...ON THE EDGE...FOR SEVERAL DAYS...INTO EARLY NEXT WEEK...SO WE WATCH FOR RAIN AND THUNDERSTORMS...AT ANYTIME. AS FOR "DOLLY" THE ENERGY WILL PUSH DUE WEST INTO THE SOUTHWEST AND MEXICO...AT SOME POINT THE POCKET WILL GET PICKED UP AND BROUGHT BACK OVER THE NATION--THAT WILL BE THE MIDDLE TO END OF NEXT WEEK...NO BIG DEAL--BUT SOMETHING FUN TO WATCH IN THE ATMSOPHERE

NEAT STUFF:

DESCENDING SPACE JUNK: Almost exactly one year ago, on July 23, 2007, International Space Station astronauts threw an obsolete, refrigerator-sized ammonia reservoir overboard. The 1400-lb piece of space junk has been circling Earth ever since and now, in July 2008, its orbit has decayed so much that it has become an easy naked-eye target for backyard sky watchers. The "Early Ammonia Servicer" (EAS for short) is almost as bright as the stars of the Big Dipper and growing brighter as it descends. Today's edition of

http://spaceweather.com displays photos of the EAS, which is expected to burn up in Earth's atmosphere in late 2008 or early 2009. Readers who wish to see the EAS with their own eyes should check the Simple Satellite Tracker for flyby times: http://spaceweather.com/flybys. Europeans are favored with flybys this week, North Americans next week.
.

STAR CHART INFO: 

THE COOL PIC OF THE DAY:

NOAA satellite image, June 30, 2004, showing wildfire smoke blanketing Alaska.

High resolution (credit: NOAA)

The Arctic may get some temporary relief from global warming if the annual North American wildfire season intensifies, according to a new study by researchers at the University of Colorado and NOAA.

Smoke transported to the Arctic from northern forest fires may cool the surface for several weeks to months at a time, according to the most detailed analysis yet of how smoke influences the Arctic climate relative to the amount of snow and ice cover.

"Smoke in the atmosphere temporarily reduces the amount of solar radiation reaching the surface. This transitory effect could partly offset some of the warming caused by the buildup of greenhouse gases and other pollutants," said Robert Stone, an atmospheric scientist with the university and NOAA Cooperative Institute for Research in Environmental Sciences (CIRES) and lead author of the study, which appears this week in the Journal of Geophysical Research.

How much solar energy is prevented from reaching the surface depends on the smoke's opacity, the elevation of the sun above the horizon, and the brightness of the surface, according to the study.

Stone and his research colleagues analyzed the short-term climate impact of numerous wildfires that swept through Alaska and western Canada in 2004. That summer, fires burned a record 10,000 square miles of Alaska's interior and another 12,000 square miles in western Canada.

A NOAA climate observatory near Barrow, Alaska, provided the data for the study. Smoke observed at Barrow was so thick that at times visibility dropped to just over one mile. The aerosol optical depth (AOD), a measure of the total absorption and scattering of solar radiation by smoke particles, rose a hundredfold from typical summer values.

Smoke in the atmosphere tends to cool the snow-free tundra while warming the smoke layer itself, the authors found. Smoke has an even greater cooling effect over the darker, ice-free ocean and less over bright snow.

"The heating of the smoke layer and cooling of the surface can lead to increased atmospheric stability, which in turn may keep clouds from forming," said Stone. "We think that this influence of smoke aerosol on clouds further affects the balance of radiation reaching the surface in the Arctic."

Research observatories as far away as Greenland and the Svalbard archipelago north of Norway also recorded elevated AOD values over several weeks during the 2004 summer, suggesting that the climate footprint of the North American wildfires was far-reaching. Smoke from the same fires also was observed as far south as the Gulf of Mexico.

To conduct their analysis, Stone and colleagues looked at how a range of smoky conditions might change the amount of solar radiation reaching the Earth’s surface. Models showed that the cooling caused by future forest fires would depend on the severity of the fire season and on the geographic dispersion of smoke.

The authors cautioned, however, that the full climate impact of Arctic aerosols, including smoke particles, is still not entirely clear. For one thing, smoke particles captured within clouds or deposited on snow may change the brightness of these objects, further affecting the amount of solar radiation absorbed by the surface.

Also, aerosols such as smoke affect the absorption and scattering not only of solar radiation, but also of longwave or thermal radiation within the atmosphere. The impact of aerosols on longwave radiation, which dominates at night and during the long, dark winter season in the Arctic, has yet to be quantified.

The 2008 Perseid Meteor Shower

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July 22, 2008: Mark your calendar: The 2008 Perseid meteor shower peaks on August 12th and it should be a good show.

"The time to look is during the dark hours before dawn on Tuesday, August 12th," says Bill Cooke of NASA's Meteoroid Environment Office at the Marshall Space Flight Center. "There should be plenty of meteors--perhaps one or two every minute."

Right: A Perseid meteor over Joshua Tree National Park in California, August 11, 2007. Credit: Joe Westerberg. [more]

The source of the shower is Comet Swift-Tuttle. Although the comet is far away, currently located beyond the orbit of Uranus, a trail of debris from the comet stretches all the way back to Earth. Crossing the trail in August, Earth will be pelted by specks of comet dust hitting the atmosphere at 132,000 mph. At that speed, even a flimsy speck of dust makes a vivid streak of light when it disintegrates--a meteor! Because, Swift-Tuttle's meteors streak out of the constellation Perseus, they are called "Perseids."

(Note: In the narrative that follows, all times are local. For instance, 9:00 pm means 9:00 pm in your time zone, where you live. )

Sign up for EXPRESS SCIENCE NEWS delivery Serious meteor hunters will begin their watch early, on Monday evening, August 11th, around 9 pm when Perseus first rises in the northeast. This is the time to look for Perseid Earthgrazers--meteors that approach from the horizon and skim the atmosphere overhead like a stone skipping across the surface of a pond.

"Earthgrazers are long, slow and colorful; they are among the most beautiful of meteors," says Cooke. He cautions that an hour of watching may net only a few of these at most, but seeing even one can make the whole night worthwhile.

A warm summer night. Bright meteors skipping overhead. And the peak is yet to come. What could be better?

The answer lies halfway up the southern sky: Jupiter and the gibbous Moon converge on August 11th and 12th for a close encounter in the constellation Sagittarius: sky map. It's a grand sight visible even from light-polluted cities.

For a while the beautiful Moon will interfere with the Perseids, lunar glare wiping out all but the brightest meteors. Yin-yang. The situation reverses itself at 2 am on Tuesday morning, August 12th, when the Moon sets and leaves behind a dark sky for the Perseids. The shower will surge into the darkness, peppering the sky with dozens and perhaps hundreds of meteors until dawn.

Above: The eastern sky viewed during the hours before sunrise on Tuesday, Aug. 12, 2008.

For maximum effect, "get away from city lights," Cooke advises. The brightest Perseids can be seen from cities, he allows, but the greater flurry of faint, delicate meteors is visible only from the countryside. (Scouts, this is a good time to go camping.)

The Perseids are coming. Enjoy the show!

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Author: Dr. Tony Phillips | Credit: Science@NASA

NASA works to improve short-term weather forecasts

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July 18, 2008: Sometimes seconds count. If a furious, tornado-spitting thunderstorm was bearing down on your home town, a few moments might make all the difference in the world.

Will McCarty, a graduate student at the National Space Science and Technology Center, is working with data from NASA's Aqua satellite to improve short-term weather predictions--the kind that could help you dodge that thunderstorm.

Above: Severe weather over DeWitt, Michigan, on June 14, 2008. Photo credit and copyright: Daniel O'Malley.

Guided by his NASA mentor, Gary Jedlovec, McCarty has already learned how to improve 48-hour forecasts by 3 hours. "That may not sound like a big deal, but tell that to someone who escaped a weather disaster by the skin of their teeth," says McCarty.

They accomplished the improvement by entwining measurements from Aqua's Atmospheric Infrared Sounder (AIRS), into weather models. To understand how AIRS works its magic, let's first take a look at how forecasts are made:

Sign up for EXPRESS SCIENCE NEWS delivery Twice a day, all over the world, weather balloons measure temperature, wind, air pressure and humidity. These balloons sample the lowest 7 to 10 miles of Earth's atmosphere, where weather happens. More measurements are made by surface observing stations, aircraft, and weather radars. All these data form a "snapshot" of the weather over the land at one point in time, every 12 hours.

Next, the measurements are plugged into forecast models--computer-coded equations that describe the interactions among the weather-influencing variables mentioned above, plus others. A forecaster interprets the model output to make his local weather prediction.

Sometimes lives ride on this mundane sounding process.

"The better we make the model output, the more the forecaster can trust it and use it as a tool for forecasting, and the more accurate forecasts the public receives," says McCarty.

AIRS improves the model output by improving its input: Riding on NASA's Aqua spacecraft and viewing the atmosphere through nearly 2,400 different spectral channels, AIRS creates an accurate global 3-D map of atmospheric temperature, water vapor, clouds and greenhouse gases.

Right: Will McCarty of the National Space Science and Technology Center in Huntsville, Alabama. [more]

"AIRS has finer resolution than previous instruments, so it can make more detailed measurements," says McCarty. "This makes analyses sharper, which improves the forecasts based on them."

McCarty and Jedlovec are most interested in AIRS infra-red "radiances," i.e., measurements of thermal energy emitted by the Earth's surface and atmosphere. The researchers look at radiances because they provide large scale measurements of the temperature and water vapor patterns in the atmosphere.

"Radiance measurements, in general, allow the observation of many places, particularly over the oceans, that are sparsely measured directly by traditional means, if at all," explains McCarty. "AIRS gives us the best picture of the vertical temperature and moisture structures ever made from space."

AIRS' claim to fame, then, is its capacity to increase both the area of Earth's atmosphere measured and the detail of those measurements.

Above: A typical AIRS infra-red weather snapshot. This is typhoon Nakri, which Aqua flew over on May 28, 2008. [more]

What's the next step? "Dealing with clouds," says McCarty. "Infrared energy doesn't penetrate clouds well. When clouds are around, the instrument is really only seeing the tops of clouds."

When clouds are low, however, there's still some good data from the air above them because most of the atmosphere is still being measured. These data have been wasted up to now – thrown out in the bathwater along with all the other cloud-contaminated data.

McCarty is now working on an algorithm to identify which channels are truly useless and which are valid. His method will help identify what is good, useful data and increase the amount of data collected, making even better forecasts possible. He will soon plug his data into a forecast model to find out just how much better.

A 3-hour improvement may be just the beginning.

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Author: Dauna Coulter | Editor: Dr. Tony Phillips | Credit: Science@NASA

The combined average global land and ocean surface temperatures for June 2008 ranked eighth warmest for June since worldwide records began in 1880, according to an analysis by NOAA’s National Climatic Data Center in Asheville, N.C. Also, globally it was the ninth warmest January – June period on record.

• The combined global land and ocean surface temperature for June 2008 was 60.8 degrees F, which is 0.9 degrees F above the 20th century mean of 59.9 degrees F.

• Separately, the global land surface temperature was 57.2 degrees F, which is 1.3 degrees F above the 20th century mean of 55.9 degrees F.

• The global ocean surface temperature was 62.2 degrees F, which is 0.7 degrees F above the 20th century mean of 61.5 degrees F.

• For the January – June period, the combined global land and ocean surface temperature was 57.1 degrees F, which is 0.8 degrees F about the 20th century mean of 56.3 degrees F.

• Northern Hemisphere Arctic sea ice extent for June 2008 ranked third lowest for June since records began in 1979. Southern Hemisphere Antarctic sea ice extent for June 2008 was above the 1979-2000 mean, ranking as the second largest June extent.

• El Niño-Southern Oscillation conditions transitioned to a neutral phase during June.

• Torrential rain lashed southern China from June 7-18. These were followed by more heavy rain from typhoon Fengshen late in the month. The downpours caused widespread floods and affected more than five million people. June 2008 was the wettest month ever for Hong Kong, Guangzhou, and Macao based on records that began in 1884. 

Two low-flying unmanned aircraft are cruising over Greenland this month to closely observe the melting of the Greenland Ice Sheet and its potential contribution to global sea level rise in the coming century. The flights will help scientists determine whether the ice sheet’s melt rate will accelerate in the future.

“We’re seeing the start of a new era in Arctic exploration,” said scientist Betsy Weatherhead, of NOAA’s Earth System Research Laboratory (ESRL) and the Cooperative Institute for Research in Environmental Sciences (CIRES). “With unmanned aircraft systems, we can fly missions too dangerous, dirty, or dull for humans and address questions we couldn’t even think of addressing before.”

Weatherhead is a lead scientist for the Arctic testbed of NOAA’s Unmanned Aircraft Systems program, which is funding the Greenland field experiment. The project is a partnership of ESRL, CIRES, and Advanced Ceramics Research, manufacturer of the unmanned “Manta” vehicles. The two Mantas fly out of Ilulissat, half way up Greenland’s west coast, for three weeks through the end of July.

The Greenland Ice Sheet is shrinking at a rate of 40–50 cubic miles each year, according to NASA satellite measurements, and that rate is accelerating. The total volume of the ice sheet is 700,000 cubic miles. Scientists believe the buildup of heat-trapping gases in Earth’s atmosphere is the main culprit, but the mechanisms are unclear. Better observations will shed light on the role of short-lived surface lakes and why the edges of the ice sheet are melting rapidly.

In summer the sun melts the top layer of the glaciers to form little lakes throughout the region, many of which vanish within a day. Scientists think these lakes may be emptying out through the ice and lubricating the bottom of the glacier with water. The glacier can then slide more quickly down the valleys, eventually breaking off into icebergs at the coastline.

A bird’s-eye view of the region from 500 to 1,000 feet above the ice can provide fine-scale measurements of the water and surface of the glaciers. Low-flying, unmanned Mantas give just that view, cruising at low altitudes over little-known terrain without putting human life at risk.

“We’re concerned that as temperatures rise, more heat will cause more melting, more melting will create bigger lakes, and the rate of ice loss will accelerate,” said NOAA Corps CDR John Adler, the project manager and a CIRES graduate student.

Trained operators from ACR control the crewless vehicles from the ground under the direction of on-site scientists. The eight-foot-wide, 45-pound Mantas take off on airport runways with permission from air traffic authorities. They can carry 15-pound instrument payloads and fly for up to six hours at about 40 knots, or 45 miles per hour, according to the Advanced Ceramics Research Web site.

What's Wrong with the Sun? (Nothing)

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Stop the presses! The sun is behaving normally.

So says NASA solar physicist David Hathaway. "There have been some reports lately that Solar Minimum is lasting longer than it should. That's not true. The ongoing lull in sunspot number is well within historic norms for the solar cycle."

This report, that there's nothing to report, is newsworthy because of a growing buzz in lay and academic circles that something is wrong with the sun. Sun Goes Longer Than Normal Without Producing Sunspots declared one recent press release. A careful look at the data, however, suggests otherwise.

But first, a status report: "The sun is now near the low point of its 11-year activity cycle," says Hathaway. "We call this 'Solar Minimum.' It is the period of quiet that separates one Solar Max from another."

Above: The solar cycle, 1995-2015. The "noisy" curve traces measured sunspot numbers; the smoothed curves are predictions. Credit: D. Hathaway/NASA/MSFC. [more]

During Solar Max, huge sunspots and intense solar flares are a daily occurance. Auroras appear in Florida. Radiation storms knock out satellites. Radio blackouts frustrate hams. The last such episode took place in the years around 2000-2001.

During Solar Minimum, the opposite occurs. Solar flares are almost non-existant while whole weeks go by without a single, tiny sunspot to break the monotony of the blank sun. This is what we are experiencing now.

Sign up for EXPRESS SCIENCE NEWS delivery Although minima are a normal aspect of the solar cycle, some observers are questioning the length of the ongoing minimum, now slogging through its 3rd year.

"It does seem like it's taking a long time," allows Hathaway, "but I think we're just forgetting how long a solar minimum can last." In the early 20th century there were periods of quiet lasting almost twice as long as the current spell. (See the end notes for an example.) Most researchers weren't even born then.

Hathaway has studied international sunspot counts stretching all the way back to 1749 and he offers these statistics: "The average period of a solar cycle is 131 months with a standard deviation of 14 months. Decaying solar cycle 23 (the one we are experiencing now) has so far lasted 142 months--well within the first standard deviation and thus not at all abnormal. The last available 13-month smoothed sunspot number was 5.70. This is bigger than 12 of the last 23 solar minimum values."

In summary, "the current minimum is not abnormally low or long."

The longest minimum on record, the Maunder Minimum of 1645-1715, lasted an incredible 70 years. Sunspots were rarely observed and the solar cycle seemed to have broken down completely. The period of quiet coincided with the Little Ice Age, a series of extraordinarily bitter winters in Earth's northern hemisphere. Many researchers are convinced that low solar activity, acting in concert with increased volcanism and possible changes in ocean current patterns, played a role in that 17th century cooling.

For reasons no one understands, the sunspot cycle revived itself in the early 18th century and has carried on since with the familiar 11-year period. Because solar physicists do not understand what triggered the Maunder Minimum or exactly how it influenced Earth's climate, they are always on the look-out for signs that it might be happening again.

The quiet of 2008 is not the second coming of the Maunder Minimum, believes Hathaway. "We have already observed a few sunspots from the next solar cycle," he says. (See Solar Cycle 24 Begins.) "This suggests the solar cycle is progressing normally."

What's next? Hathaway anticipates more spotless days1, maybe even hundreds, followed by a return to Solar Max conditions in the years around 2012.

Stay tuned to Science@NASA for updates.

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Author: Dr. Tony Phillips | Credit: Science@NASA

NASA to Attempt Historic Solar Sail Deployment

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"Hold your hands out to the sun. What do you feel? Heat, of course. But there's pressure as well – though you've never noticed it, because it's so tiny. Over the area of your hands, it only comes to about a millionth of an ounce. But out in space, even a pressure as small as that can be important – for it's acting all the time, hour after hour, day after day. Unlike rocket fuel, it's free and unlimited. If we want to, we can use it; we can build sails to catch the radiation blowing from the sun."1

These words were spoken not by a NASA scientist but by a fictional character – John Merton – in Arthur C. Clarke's short story The Wind from the Sun. If all goes well, Merton's prophetic words are about to become fact.

NASA researchers, thinking "out of the box" (or maybe "out of the rocket") have long dreamed of the possibility of sailing among the planets with sails propelled by sunlight instead of by wind. Except in works of fiction, though, no one has yet successfully deployed such a sail anywhere beyond Earth.

Right: An artist's concept of a sailing ship and a solar sail.

"There's a first time for everything," says Edward "Sandy" Montgomery of NASA's Marshall Space Flight Center.

Montgomery's team and a team from Ames Research Center (led by Elwood Agasid) hope to make history this summer by deploying a solar sail called NanoSail-D. It will travel to space onboard a SpaceX Falcon 1 rocket, scheduled for launch from Omelek Island in the Pacific Ocean during a window extending from July 29th to August 6th (a back-up extends from August 29th to September 5th).

Sign up for EXPRESS SCIENCE NEWS delivery "NanoSail-D will be the first fully deployed solar sail in space, and the first spacecraft to use solar pressure as a primary means of attitude control or orbital maneuvering," says Montgomery, who is NanoSail-D's payload manager.

"We are always on the lookout for opportunities. Ames owns a slot on the Falcon 1 launch and asked us if we wanted to go along. We said, 'Yes!' We'll use the Poly Picosatellite Orbital Deployer, or P-POD, developed by the University of California Polytechnic Institute to deploy our sail."

A few years ago, the Planetary Society attempted a mission like NanoSail-D called Cosmos I, but the launch vehicle failed and destroyed the undeployed spacecraft. Montgomery and team believe that NanoSail-D, however, will unfurl four gossamer wings from its pod in the blackness of space like a butterfly from a cocoon: movie.

"The structure is made of aluminum and space-age plastic," says Montgomery. "The whole spacecraft weighs less than ten pounds. We carry it around in a special suitcase -- airplane carry-on luggage size." Fully opened, the kite-shaped sail spreads out to about 100 square feet of light-catching surface.

Above: The Huntsville-based NanoSail-D team stands with the fully deployed sail at ManTech SRS technologies on April 16, 2008, after the successful deployment test.

"A success would be huge for the future of space exploration," Montgomery believes.

Why so important? Solar sails could extend our reach as far as our dreams. Because there's no friction in space, once a solar sail starts moving, it can go on forever. Indeed, long after a rocket would run out of gas and begin to coast, a solar sailship could still be accelerating, achieving speeds much faster and covering distances far greater than any rocket. No rocket in existence could carry enough fuel to reach the outer solar system in as short a time. And like a marine sail, a solar sail could also bring you home. You could use the solar sail to tack your vessel, making it travel "against the wind," back to Earth.

"It's not so much about how far a sail will go compared to a rocket; the key is how fast," says Montgomery. "The Voyagers have escaped the solar system, and they were sent by rockets, but it's taken more than three decades to do it. A sail launched today would probably catch up with them in a single decade. Sails are slower to get started though. So, for example, between the Earth and the moon, rockets might be preferred for missions with a short timeline. It's a trip of days for rockets, but months for a solar sail. The rule of thumb, therefore, would be to use rockets for short hops and solar sails for the long hauls."

Right: University of Alabama research technician Doug Huie holds the future in his hands. Folded-up, NanoSail-D occupies a space no bigger than a bread box.

All of this may sound like speculation, but NanoSail-D could show that solar sails are truly feasible. And there's an added bonus to this technology demo:

"Currently, micro-satellites in orbit above a few hundred kilometers can stay in orbit for decades after completing their mission," explains Montgomery. "This creates an orbital debris collision risk for other spacecraft. NanoSail-D will demonstrate the feasibility of using a drag sail to decrease the time satellites clutter up Earth's orbit. Although our sail looks like a kite, it will act like a parachute (or like a drag sail) in the very thin upper atmosphere around Earth. It will slow the spacecraft and make it lose altitude, re-enter the Earth's atmosphere and burn off in a relatively short period of time. A drag sail is a lighter alternative to carrying a propulsion system to de-orbit a satellite."

And finally, the question everyone wants answered: What does D stand for?

"We chose the 'D' in the name, not because it came after models A, B, and C, but because it can stand for demonstrate, deploy, drag, and/or de-orbit," says Montgomery.

Soon, 'D' may stand for something new: "DID IT!"

Check Science@NASA post-launch and the meaning will be revealed.

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Author: Dauna Coulter | Editor: Dr. Tony Phillips | Credit: Science@NASA

High resolution (Credit: NOAA)

The U.S. Climate Change Science Program and the Subcommittee on Global Change Research today released a scientific assessment that provides the first comprehensive analysis of observed and projected changes in weather and climate extremes in North America and U.S. territories. The Intergovernmental Panel on Climate Change previously evaluated extreme weather and climate events on a global basis in this same context. However, there has not been a specific assessment across North America prior to this report.

Among the major findings reported in this assessment are that droughts, heavy downpours, excessive heat, and intense hurricanes are likely to become more commonplace as humans continue to increase the atmospheric concentrations of heat-trapping greenhouse gases.

The report is based on scientific evidence that a warming world will be accompanied by changes in the intensity, duration, frequency, and geographic extent of weather and climate extremes.

"This report addresses one of the most frequently asked questions about global warming: what will happen to weather and climate extremes? This synthesis and assessment product examines this question across North America and concludes that we are now witnessing and will increasingly experience more extreme weather and climate events," said report co-chair Tom Karl, Ph.D., director of NOAA’s National Climatic Data Center in Asheville, N.C.

High resolution (Credit: NOAA)

"We will continue to see some of the biggest impacts of global warming coming from changes in weather and climate extremes,” said report co-chair Gerry Meehl, Ph.D., of the National Center for Atmospheric Research in Boulder, Colo. "This report focuses for the first time on changes of extremes specifically over North America."

The full CCSP 3.3 report, Weather and Climate Extremes in a Changing Climate, and a summary FAQ brochure are available online.

Global warming of the past 50 years is due primarily to human-induced increases in heat-trapping gases, according to the report. Many types of extreme weather and climate event changes have been observed during this time period and continued changes are projected for this century. Specific future projections include:

• Abnormally hot days and nights, along with heat waves, are very likely to become more common. Cold nights are very likely to become less common.
• Sea ice extent is expected to continue to decrease and may even disappear in the Arctic Ocean in summer in coming decades.
• Precipitation, on average, is likely to be less frequent but more intense.
• Droughts are likely to become more frequent and severe in some regions.
• Hurricanes will likely have increased precipitation and wind.
• The strongest cold-season storms in the Atlantic and Pacific are likely to produce stronger winds and higher extreme wave heights.

The National Oceanic and Atmospheric Administration, an agency of the U.S. Commerce Department, is dedicated to enhancing economic security and national safety through the prediction and research of weather and climate-related events and information service delivery for transportation, and by providing environmental stewardship of our nation's coastal and marine resources.

The combined average global land and ocean surface temperatures for spring (March-May) ranked seventh warmest, while May was the eighth warmest since worldwide records began in 1880 according to an analysis by NOAA’s National Climatic Data Center in Asheville, N.C.

• The combined global land and ocean surface temperature for spring 2008 was 0.94 degrees F above the 20th century mean of 56.7 degrees F and ranked seventh warmest based on the 1880-2008 record. 

• The global land surface temperature for spring was 1.87 degrees F above the 20th century mean of 46.4 degrees F and tied with 2000 as third warmest.

• The global ocean surface temperature for spring was 0.59 degrees F above the 20th century mean of 61.0 degrees F and ranked 10th warmest.

• For May 2008, the combined global land and ocean surface temperature was 0.81 degrees F above the 20th century mean of 58.6 degrees F and ranked eighth warmest.

• The global land surface temperature for May was 1.26 degrees F above the 20th century mean of 52.0 degrees F and ranked seventh warmest.

• The global ocean surface temperature for May was 0.65 degrees F above the 20th century mean of 61.3 degrees F and ranked 10th warmest.

• The extent of spring 2008 snow cover over Eurasia was the lowest on record for any spring in the 42-year historical satellite record. Conversely, North American snow cover extent was slightly above average. For the Northern Hemisphere, spring 2008 was the third least extensive spring snow cover.

• Continued weakening of La Niña, the cold phase of the El Niño-Southern Oscillation (ENSO), occurred during May. The ENSO conditions are expected to trend toward neutral conditions during the next two months.

• Tropical Cyclone Nargis brought heavy rain, strong winds, and high storm surge waters to Burma (Myanmar) in early May, destroying thousands of homes and killing nearly 78,000 people. Nargis was the most devastating cyclone to strike Asia since 1991 and resulted in the worst natural disaster on record for Burma.

Check out this site:

http://www.kusi.com/weather/colemanscorner/19842304
.html

Food for thought...lets hear what you have to say.

Dave

NASA Plans to Visit the Sun

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June 10, 2008: For more than 400 years, astronomers have studied the sun from afar. Now NASA has decided to go there.

"We are going to visit a living, breathing star for the first time," says program scientist Lika Guhathakurta of NASA Headquarters. "This is an unexplored region of the solar system and the possibilities for discovery are off the charts."

Right: An artist's concept of Solar Probe Plus. [more]

The name of the mission is Solar Probe+ (pronounced "Solar Probe plus"). It's a heat-resistant spacecraft designed to plunge deep into the sun's atmosphere where it can sample solar wind and magnetism first hand. Launch could happen as early as 2015. By the time the mission ends 7 years later, planners believe Solar Probe+ will solve two great mysteries of astrophysics and make many new discoveries along the way.

Sign up for EXPRESS SCIENCE NEWS delivery The probe is still in its early design phase, called "pre-phase A" at NASA headquarters, says Guhathakurta. "We have a lot of work to do, but it's very exciting."

Johns Hopkins' Applied Physics Lab (APL) will design and build the spacecraft for NASA. APL already has experience sending probes toward the sun. APL's MESSENGER spacecraft completed its first flyby of the planet Mercury in January 2008 and many of the same heat-resistant technologies will fortify Solar Probe+. (Note: The mission is called Solar Probe plus because it builds on an earlier 2005 APL design called Solar Probe.)

At closest approach, Solar Probe+ will be 7 million km or 9 solar radii from the sun. There, the spacecraft's carbon-composite heat shield must withstand temperatures greater than 1400o C and survive blasts of radiation at levels not experienced by any previous spacecraft. Naturally, the probe is solar powered; it will get its electricity from liquid-cooled solar panels that can retract behind the heat-shield when sunlight becomes too intense. From these near distances, the Sun will appear 23 times wider than it does in the skies of Earth.

Above: A simulated view of the Sun illustrating the trajectory of Solar Probe+ during its multiple near-Sun passes. [Larger image]

The two mysteries prompting this mission are the high temperature of the sun's corona and the puzzling acceleration of the solar wind:

Mystery #1—the corona: If you stuck a thermometer in the surface of the sun, it would read about 6000o C. Intuition says the temperature should drop as you back away; instead, it rises. The sun's outer atmosphere, the corona, registers more than a million degrees Celsius, hundreds of times hotter than the star below. This high temperature remains a mystery more than 60 years after it was first measured.

Mystery #2—the solar wind: The sun spews a hot, million mph wind of charged particles throughout the solar system. Planets, comets, asteroids—they all feel it. Curiously, there is no organized wind close to the sun's surface, yet out among the planets there blows a veritable gale. Somewhere in between, some unknown agent gives the solar wind its great velocity. The question is, what?

"To solve these mysteries, Solar Probe+ will actually enter the corona," says Guhathakurta. "That's where the action is."

The payload consists mainly of instruments designed to sense the environment right around the spacecraft—e.g., a magnetometer, a plasma wave sensor, a dust detector, electron and ion analyzers and so on. "In-situ measurements will tell us what we need to know to unravel the physics of coronal heating and solar wind acceleration," she says.

Right: The re-designed Solar Probe+ spacecraft. [more]

Solar Probe+'s lone remote sensing instrument is the Hemispheric Imager. The "HI" for short is a telescope that will make 3D images of the sun's corona similar to medical CAT scans. The technique, called coronal tomography, is a fundamentally new approach to solar imaging and is only possible because the photography is performed from a moving platform close to the sun, flying through coronal clouds and streamers and imaging them as it flies by and through them.

With a likely launch in May 2015, Solar Probe+ will begin its prime mission near the end of Solar Cycle 24 and finish near the predicted maximum of Solar Cycle 25 in 2022. This would allow the spacecraft to sample the corona and solar wind at many different phases of the solar cycle. It also guarantees that Solar Probe+ will experience a good number of solar storms near the end of its mission. While perilous, this is according to plan: Researchers suspect that many of the most dangerous particles produced by solar storms are energized in the corona—just where Solar Probe+ will be. Solar Probe+ may be able to observe the process in action and show researchers how to forecast Solar Energetic Particle (SEP) events that threaten the health and safety of astronauts.

Solar Probe+'s repeated plunges into the corona will be accomplished by means of Venus flybys. The spacecraft will swing by Venus seven times in six years to bend the probe’s trajectory deeper and deeper into the sun’s atmosphere. Bonus: Although Venus is not a primary target of the mission, astronomers may learn new things about the planet when the heavily-instrumented probe swings by.

"Solar Probe+ is an extraordinary mission of exploration, discovery and deep understanding," says Guhathakurta. "We can't wait to get started."

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Author: Dr. Tony Phillips | Credit: Science@NASA