Weathering heights

The National Aeronautics and Space Administration has a new job: space weatherman.

The agency's fledgling Solar Dynamics Observatory (SDO) will study sun storms and how they occur. Storms from the sun explosively release magnetic energy and affect space weather.

These storms, which send massive streams of charged particles for millions of miles across and outside the solar system, can cripple satellites, disable power grids and jam radio communications.

Radio links on Earth have been a critical safety tool since the earliest days of the technology. Before the federal government created the Federal Communications Commission in 1934, the Navy regulated radio matters because officials considered that the technology's main function would be helping save distressed mariners.

Nowadays, radio networks such as the Global Positioning System, which provides radiolocation services worldwide, form one of the latest safety-critical radio applications that solar storms can shut down.

The new observatory includes technology that NASA will use to issue warnings of approaching solar storms.

Those warning can help radio system operators prepare for pending outages. The warning can help satellite owners plan how to reorient their 'birds' by firing small control thrusters. The repositioned satellites can face their most durable, or solar flare resistant, components in the direction of the oncoming blast of solar energy so as to protect more vulnerable parts.

"Right now, we can make limited space weather predictions, but they are baby steps compared to our ability to forecast weather on Earth," said Dean Pesnell of NASA's Goddard Space Flight Center, Greenbelt, Md., project scientist for SDO.

"SDO's instruments are designed to work together to tell us more about how solar storms form, which will improve predictions of when they are about to happen," Pesnell said.

Solar flares, or explosions in the sun's atmosphere, can be devastating. The largest are equal to billions of one-megaton nuclear bombs. Solar magnetic energy can also blast billions of tons of plasma into space at millions of miles per hour as a coronal mass ejection (CME).

This violent solar activity often occurs near sunspots, dark regions on the sun caused by concentrated magnetic fields. Sunspots and stormy solar weather follow a cycle that repeats approximately every 11 years, from few sunspots and quiet conditions to many sunspots and active, and back again.

NASA plans to launch the observatory, a semi-autonomous spacecraft, in December into geosynchronous orbit with a dedicated ground station. The craft will have a continuous data downlink. The observatory will study the flows of plasma inside the sun and how these affect the sun's weather as well as what magnetic structures lead to flares and CMEs.

The observatory will use three instruments to study the sun's weather. The first is a Helioseismic and Magnetic Imager (HMI), which will help map plasma flows inside the sun and create a picture based on sound waves of the sun's interior, similar to an ultrasound scan. HMI also will measure the strength and direction of the magnetic fields emerging on the sun's surface. NASA plans to use this data to determine how magnetic fields move and concentrate in the sun, the cause of storms.

The Atmospheric Imaging Assembly will take pictures of the sun's atmosphere close to the surface where solar magnetic fields change shape and release energy. It will be used with HMI to link changes on the sun's surface to interior changes.

The Extreme Ultraviolet Variability Experiment (EVE) will measure the sun's ultraviolet brightness, which constantly changes. Rapid changes in the sun's ultraviolet radiation can cause outages in radio communications and affect satellites orbiting the Earth. EVE will take measurements of the sun's brightness as often as every 10 seconds, providing space weather forecasters with warnings of communications and navigation outages.

The three technologies will be used together to forecast space weather and climate.

The observatory is the first mission to be launched for NASA's Living With a Star Program, designed to help federal agencies and humanity generally to understand the sun's influence on Earth and near-Earth space.

About the Author

Kathleen Hickey is a freelance writer for GCN.


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