Posts Tagged ‘weather

Space Weather

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So much of our modern technology is at risk from space weather, including satellites, communications and power grids. Airline passengers flying over the poles and astronauts can also be adversely effected. Studying the causes and effects of space weather can help us to better predict these events and to take precautions to minimize their impacts. Credit: NASA

Five scientists speaking at a workshop at the 2011 Fall AGU meeting in San Francisco on Tuesday, December 6 at 10 AM PST will discuss the complex — and relatively new — research area of space weather. The term refers to a host of disturbances that can alter the vast electromagnetic system stretching from the sun to Earth and all the way to the edges of the solar system. This system is increasingly dynamic as the sun moves toward solar maximum in 2013 and sends out correspondingly more energy and eruptions. Such energy can disrupt and even damage human technology, and scientists would like to predict space weather as well as meteorologists do for conventional weather on Earth. Our understanding of space weather has already improved substantially since the last solar maximum in 2001, and a host of spacecraft instruments are supplying data to continue to expand our knowledge.

The speakers will provide the context to understand the science of the sun-Earth system, discuss the details of potential space weather effects, and explain the state-of-the-art in terms of space weather modeling and prediction.

Earth’s own magnetic environment, the magnetosphere, is an inextricable part of this system, changing constantly in response to incoming energy from the sun such as the stream of particles known as the solar wind, giant eruptions of radiation from the sun called solar flares, or bursts of solar material called coronal mass ejections. In the workshop, Daniel Baker from the University of Colorado in Boulder, Colo., explains the current understanding of the physics behind this system. Showing high-resolution pictures of the sun’s roiling surface, Baker will trace ejections from their origin at the sun through space to Earth’s protective magnetic envelope. Here, under the correct circumstances, the sun’s energy can connect efficiently and effectively with Earth’s own atmosphere.
Louis Lanzerotti from the New Jersey Institute of Technology in Newark, N.J., explains what happens next. At their most benign, such space weather events trigger beautiful aurora in the night sky as incoming particles collide with Earth’s atmosphere and produce light. But space weather can also adversely impact our modern technological infrastructure. Even in the mid-1800s, telegraph operators noticed that auroras in the night sky coincided with disruptions to telegraph operation – and today such disruptions can affect a much wider array of technologies that have developed over the last century. Such space weather-produced effects include loss of radio contact for airplanes on transpolar flights, astronauts imperiled by radiation, damage to electric grids, and disruption of cell phone service and underwater telecommunication cables, and destruction of satellite electronics. The effects of the sun can be complex, subtle, and some times quite surprising, and we need accurate models and accurate forecasts to protect modern technology.

Discussing the state-of-the-art in such models, Michael Hesse of NASA’s Goddard Space Flight Center in Greenbelt, Md., describes researchers’ recent successes in data analysis and modeling efforts. Hesse leads the Community Coordinated Modeling Center at Goddard, which combines models with real time observations from NASA spacecraft that together show all sides of the sun. By incorporating stereoscopic views of a coronal mass ejection, for example, scientists at the CCMC can better predict its direction and velocity.

Such prediction techniques are still young, not unlike the early days of Earth weather forecasting, but they nevertheless represent a giant leap in accuracy. Antti Pulkkinen, a scientist with both Goddard and Catholic University in Washington, D.C., describes the new more accurate, numerical-based models. These have been made possible due to improvement not only in the models themselves, but due to more comprehensive observations and the increased power of supercomputers. One use for such models: the Solar Shield Project, which can predict which areas on Earth may experience the worst effects from an incoming solar storm. Power grid operators can then take steps to protect their technology from harm rather than risk damage to their transformers.
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Written by physicsgg

December 6, 2011 at 9:41 am

Posted in SPACE

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Firing laser beams into the sky could make it rain, say scientists

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Water droplets have been created by shooting lasers into the air. The technique might be used to create or prevent rain

Ever since ancient farmers called on the gods to send rain to save their harvests, humans have longed to have the weather at their command.

That dream has now received a boost after researchers used a powerful laser to produce water droplets in the air, a step that could ultimately help trigger rainfall.

While nothing can produce a downpour from dry air, the technique, called laser-assisted water condensation, might allow some control over where and when rain falls if the atmosphere is sufficiently humid.

Researchers demonstrated the technique in field tests after hauling a mobile laser laboratory the size of a small garage to the banks of the Rhône near lake Geneva in Switzerland.

Records from 133 hours of firings revealed that intense pulses of laser light created nitric acid particles in the air that behaved like atmospheric glue, binding water molecules together into droplets and preventing them from re-evaporating.

Within seconds, these grew into stable drops a few thousandths of a millimetre in diameter: too small to fall as rain, but large enough to encourage the scientists to press on with the work.

“We have not yet generated raindrops – they are too small and too light to fall as rain. To get rain, we will need particles a hundred times the size, so they are heavy enough to fall,” said Jérôme Kasparian, a physicist at the University of GenevaA report on the tests appears in the journal Nature Communications.

With improvements, shooting lasers into the sky could either help trigger or prevent showers. One possibility might be to create water droplets in air masses drifting towards mountains. The air would cool as it rose over these, causing the water droplets to grow and eventually fall.

An alternative might be to stave off an immediate downpour by creating so many tiny droplets in the air that none grew large enough to fall. “Maybe one day this could be a way to attenuate the monsoon or reduce flooding in certain areas,” Kasparian said.

Efforts to bring the weather under control have become a matter of national pride in China, where the Beijing meterological bureau has an office devoted to weather modificationIn 2009, the department claimed success after 18 jets and 432 explosive rockets laden with chemicals were sent into the skies to “seed” clouds. The chemicals, usually dry ice or silver iodide, provide a surface for water vapour to condense on, and supposedly trigger downpours from pregnant skies.

Kasparian believes laser-assisted rainmaking has advantages over blasting chemicals into the sky. “The laser can run continuously, you can aim it well, and you don’t disperse huge amounts of silver iodide in the atmosphere,” he said.

“You can also turn the laser on and off at will, which makes it easier to assess whether it has any effect. When the Chinese launch silver iodide into the sky, it is very hard to know whether it would have rained anyway,” Kasparian added.

The team’s Teramobile laser can shoot beams of light several kilometres into the sky, putting within easy reach the regions of the atmosphere where water vapour normally condenses into raindrops.

One modification the team is considering involves sweeping the laser across the sky to produce water droplets over a greater area. “From a technical point of view, sweeping the laser is not an issue. They do it in nightclubs all the time,” Kasparian said.

Written by physicsgg

August 30, 2011 at 6:38 pm

Posted in meteorology

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