The sun is primarily a giant, gaseous nuclear reactor. The bulk of its mass comes from the hydrogen atoms in its core which undergo nuclear fusion reactions to generate helium atoms and tremendous amounts of heat and energy in the form of radiation. The outer layers of the sun, however, are primarily made of plasma, which is little more than clouds of charged particles carried along by magnetic fields. The magnetic fields themselves are the product of the movement of the charged particles, forming a giant, self-sustaining web of magnetic current.
The sun undergoes a cycle of fluctuations in its magnetic field approximately every eleven years, and its observed activity changes accordingly as a result of the shifting magnetic forces. Solar 'activity' is used broadly to describe solar wind, solar flares, the formation of solar prominences, and coronal mass ejections. Entry into the phase known as the solar maximum of the solar cycle is marked by a prolonged and heightened flurry of activity. Fluctuations in magnetic fields on and around the sun's surface are responsible for the observed increase in activity during solar maxima, as measured by the number of surface sunspots and the frequency of massive solar flares and prominences. At present we are at the peak of the solar maximum, meaning that the sun is at its most active in eleven years, and NASA has estimated that the peak will last until approximately Fall 2013. Compared to previous solar cycles, the sun's current cycle is relatively mild- the last time the solar peak activity was as low as it is now was over a century ago. Regardless, the sun's increased activity in the midst of the solar maximum poses a threat to our astronauts and the electrical systems, and satellites we are so reliant upon.
|The double solar prominences that occured on Nov. 16th. Image credit: Steele Hill, SDO/NASA|
In the image above, the glowing (and presumably very, very hot) red loops are made of plasma, a cloud of electrically charged helium and hydrogen atoms. Plasma is swept along with the tide of the sun's ever-changing magnetic fields until the massive web of magnetic forces becomes unstable and the forcefully bursts outward, causing the plasma to be ejected from the sun's surface. The plasma 'loops' formed are known as solar prominences, and can reach up to hundreds of thousands of miles away from the sun. On November 16th two large solar prominences were spotted erupting, and NASA caught it all on video. Fortunately, the recently observed prominences were not directed towards the earth; otherwise, the results could have been disastrous.
|The corona, visible in an image taken during an eclipse. Image credit: NASA.gov|
|A solar eruption (coronal mass ejection, CME) from June 2011. Image credit: SDO/NASA|
In a CME, charged particles, matter, and heat are carried along by the force of the plasma explosion and, if headed in the direction of the earth, can interfere with the earth's electrical grids and satellites. First, the outermost atmosphere of the earth would be bombarded with radiation and ultraviolet light, potentially disrupting radio communication. The real trouble comes later- sometimes days after the actual CME event- when the CME cloud reaches the earth. The plasma cloud also hauls billions of tons of matter along with it, comparable to the weight of Mount Everest slamming into the earth. As solar charged particles enter the earth's atmosphere, many orbiting satellites would be at risk. Many of the charged particles will also be drawn into the transmission wires on electrical grids, overloading the wires and potentially damaging transformers as a result of the the surge of electricity. Many experts believe that the potential damage to our electric distribution systems could be so heavy that it would result in widespread and prolonged power outages and have a significant economic impact as a result.
In terms of solar storms, size isn't all that matters- even a relatively small solar storm could be disastrous if it reaches the earth. It already happened once in 1859, in the midst of a solar maximum comparable to the cycle we are in now, according to NASA. Now known as the 'Carrington Event', named for the man who first realized the connection between solar activity and accompanying disturbances on earth, it was one of the worst solar storms ever encountered. As a surge of solar particles collided with gases in the earth's atmosphere, the 'northern lights' were visible as far south as the equator. The mass entry of charged solar particles into telegraph wires caused several telegraph stations to explode and damaged telegraph wires. The modern electric grid is still vulnerable to geomagnetic disturbances such as the 1859 solar storm, and widespread power outages or damage to transformer and the electric transmission system would be far more damaging due to our heavy reliance on electrical power.
Regulatory agencies are beginning to recognize the danger of GMDs as we enter the solar maximum, and have begun addressing the vulnerabilities in our electric distribution systems accordingly. After a careful review of professional testimony regarding the potential threat of geomagnetic disturbances (GMDs) such as solar storms, the Federal Energy Regulatory Commission (FERC) announced in October that it had found that "GMD vulnerabilities are not adequately addressed" in current standard operating procedures, "[constituting] a reliability gap" in our electrical grids. Based on these findings, FERC set forth a plan dictating that utility companies be prepared to address electrical failures as a result of GMDs and that preventive measures are put in place to protect electrical equipment from potential damage or failure after a GMD.
Scientists have also been paying more attention to the sun, carefully scrutinizing its activity to better understand the properties of the sun and the events which create solar storms. The Solar Dynamics Observatory at NASA is devoted to collecting information about the sun's activity in real time- fluctuations in the sun's magnetic fields, radiation emissions, the way the activity of the sun varies throughout the solar cycle- and analyze the information to look for patterns and make predictions about events which may affect the earth. According to their website, the SDO collects enough data to fill an entire data CD every 36 seconds!
Through the combined efforts of researchers, electricity distribution centers, and regulatory agencies, the susceptibility of our electric grids to solar storms is being addressed to protect some of our most valuable resources: energy distribution systems. Although we have never experienced a solar storm on earth of the same magnitude as the Carrington Event, many experts believe that there is a strong possibility we may one day find ourselves in a similar situation, in which case it is best to be prepared.
|Picture of the Northern Lights taken near Norway in January of this year. The lights were visible farther south after a coronal mass ejection cloud reached the earth's atmosphere. Image credit: Ole C. Salomonsen|
If you have the time, click here to go to the SDO's images page. There are some really great images of the sun in action in the gallery!