By Marlene Cimons, National Science Foundation
Just before dawn on September 2, 1859, the skies above Earth erupted into a brilliant light display of red, green and purple auroras, accompanied by a world-wide breakdown in communication systems. Telegraph operations were shut down. The discharges from sparks shocked telegraph operators, and telegraph papers caught fire.
The so-called Carrington Event, named after the British astronomer who identified it, was the result of a magnetic explosion on the sun, more commonly known as a solar flare, believed to be the biggest solar storm in history. If an event of that magnitude happened today, it could prove disastrous, wiping out electric power, disrupting spacecraft, aviation, and GPS-based positioning industries, and costing in the trillions.
“That was only 150 years ago. Could it happen again? We don’t know,’’ says Craig Foltz, of the National Science Foundation’s (NSF) division of astronomical sciences, and program director for the National Solar Observatory. “Remember that our system was very simple then. When you think about the vulnerability of our very complex communications systems today, the impact of an event like that could be substantial.’’
Space weather originates with the sun. At least four solar phenomena, not one of which is well understood, release matter from the sun into the solar system and together are the starting point for understanding the processes by which space weather develops and affects near-earth space: coronal mass ejections, solar flares, coronal holes and solar prominences.
In recent years, scientists have become increasingly involved in studying all the pieces of the space weather puzzle, using several different but complementary approaches to improve their understanding of what is happening on the sun and in the atmosphere--and when. These include the construction of a new high-powered telescope that will tell researchers more about the impact of magnetic fields on the sun, and new mathematical models—or computer calculations—that will speed up and make more accurate predictions of space weather events.
The Carrington Event was probably the greatest space weather occurrence ever recorded, but it was by no means the only one—about 500 magnetic storms occur during a typical 11-year solar cycle. In March 1989, for example, a solar storm caused the entire Quebec power grid to collapse in less than two minutes, affecting six million people in the middle of a Canadian winter. A 2003 Halloween storm prompted a massive blackout in the Northeast, and extensive satellite problems, including the loss of the $450 million Midori-2 research satellite.
“The driver for space weather is the sun,’’ says Dr. Stephen L. Keil, director of the National Solar Observatory. “The sun has a continuously changing magnetic field due to convective turbulence. When it reaches a certain state, the field has a lot of excess energy. When that happens, you get the field erupting, an explosion on the surface of the sun. It accelerates particles and ejects mass and magnetic field during the flare. When they reach Earth, they can affect Earth’s magnetic field—space systems, satellites, GPS, Direct TV, military satellites, etc.’’
Coronal mass ejections, which may or may not have accompanying flares, also cause space weather and geomagnetic disturbances, and they also accelerate energetic particles that can damage space systems. High speed solar wind streams also can cause geomagnetic disturbances.
All of these phenomena involve rapid changes in the solar magnetic field, which can have a significant impact on life on Earth.
Experts believe that society is ill prepared to cope with such severe solar disturbances, or predict them, without more knowledge of their causes.
Researchers are working to change this. The Boston University-based Center for Integrated Space Weather Modeling, for example, with the National Oceanic and Atmospheric Administration Space Weather Prediction Center, recently announced a new large-scale physics based space weather prediction model, or computer calculation program, designed to provide forecasters with a one-to-four day advance warning of high-speed streams of solar plasma and Earth-directed coronal mass ejections.