Safeguarding Our Satellites From the Sun
How much do we need to worry about the sun? Solar blasts from the past reveal some expensive consequences and important incentives to improve our understanding.
A direct hit from a giant solar storm similar to the historic 1859
storm could take a heavy toll on our satellite fleet, according to new research.
"A worst-case solar storm could have an economic impact similar to a category 5 hurricane or a tsunami," said Dr. Sten Odenwald of NASA's Goddard Space Flight Center, Greenbelt, Md. "There are more than 900 working satellites with an estimated replacement value of $170 billion to $230 billion, supporting a $90 billion-per-year industry. One scenario showed a 'superstorm' costing as much as $70 billion due to a combination of lost satellites, service loss, and profit loss."
Image left: A telegraph pole in San Francisco, Calif. Click on image for a high resolution .jpg. Credit: Damon Hart-Davis.
The 1859 storm was more severe than any encountered during the space age, according to a review of ice core data by Odenwald, and an analysis of geomagnetic data and eyewitness accounts by Dr. Jim Green of NASA Goddard, and his team. "The 1859 storm was the granddaddy of all solar storms - there has been nothing like it since," said Green. "It disrupted telegraph lines all over the world and generated aurora as far south as Panama. It enthralled the public - news reports were everywhere."
Solar storms begin with tangled magnetic fields generated by the sun's churning electrified gas (plasma). Like a rubber band that has been twisted too far, solar magnetic fields can suddenly snap to a new shape, releasing tremendous energy as a solar flare or a coronal mass ejection (CME). Solar flares are explosions in the sun's atmosphere, with the largest 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 (kilometers) per hour as a 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 an eleven-year cycle, from few sunspots and calm to many sunspots and active, and back again. The most powerful solar storms have occurred within a few years of the peak in sunspot number, which was in the year 2000 for the last solar cycle.
Recent Record-Breaking Storms
We've seen some pretty fantastic solar storms in the last few years too, despite the sun entering into the solar minimum. And we've been very lucky. The last few major storms were more like glancing blows rather than full impact in terms of affecting Earth's many satellites and space systems. For example, just last September as the nation was reeling from Hurricane Katrina, forecasters at the National Oceanic and Atmospheric Administration (NOAA) issued warnings that some of the largest solar flares ever recorded had erupted and had the potential to disrupt spacecraft operations, electric power systems, high frequency communications and low frequency navigation systems. In particular they were concerned about communications between rescue workers.
The event created "a complete blackout of high frequency communications on the daylit side of Earth, which included the entire United States and basically anywhere the sun was shinning" at the time, said Larry Combs, a solar forecaster at the NOAA Space Environment Center.
Image right: An APL technician secures the electrical harness routed to the high-gain antenna on the STEREO "A" observatory. Click on image for a high resolution .jpg. Credit: NASA/Johns Hopkins University Applied Physics Laboratory.
Perhaps the best-known disruption of service occurred in March 1989, when a powerful solar blast disturbed at least 200 different components of electric power systems in Maryland, California, New York, New Mexico, Arizona and Pennsylvania. In Sweden, five power transmission lines were tripped by large voltage fluctuations and fire alarms went off. Meanwhile a $10 million transformer was damaged beyond repair in New Jersey.
But the Hydro-Quebec power company suffered the brunt of the storm: a chain reaction collapsed an entire power grid in 90 seconds leaving more than six million people in Quebec City, Montreal, and surrounding areas without power and heat. Morning rush hour was snarled without traffic lights, the subway system and airport were shut down, and schools and businesses were forced to close. It took nine hours to restore power to most of the region and cost Hydro-Quebec at least $10 million.
Satellites were also affected: geostationary communication satellites had to be re-pointed manually and doctors never received pages. Some satellites in polar orbits tumbled out of control for several hours and some weather images were lost when the GOES weather satellite communications were interrupted.
Next Steps: Understanding and Predicting
NASA's upcoming Solar Terrestrial Relations Observatory (STEREO) will help researchers better understand space weather in order to make more accurate predictions and take better precautions. While a fleet of spacecraft already fly between the sun and Earth trying to gain a better perspective on the sun's powerful blasts, STEREO will be the first to provide a three-dimensional view. This additional information will help us understand how and why CMEs, the primary driver of space weather, occur and how they move through space.
Better prediction means more warning time for satellite and power grid operators to put their assets into a "safe mode" to weather the storm while a better understanding will help engineers figure out how to build better and more resilient systems.
"Every year we become more and more reliant on space technologies in our everyday lives and we expect things to work," said Dr. Michael Kaiser, STEREO Project Scientist at NASA Goddard Space Flight Center. "But nature has a mind of its own and STEREO is going to help us figure out how to avoid those expensive and inconvenient surprises the sun tends to throw at us."
Bill Steigerwald & Rachel A. Weintraub
NASA Goddard Space Flight Center