Although the sun provides the necessary energy for life on earth, its surface hosts one of the most hostile and violent environments in the galaxy. During the peak of the solar cycle, spots on the sun explode multiple times per day, burping out a plasma soup of electrons, protons, and light ions.
Usually, these coronal mass ejections (CMEs) cause little harm to the Earth and even cause the beautiful auroras seen near the Earth's poles. Some CMEs, however, have caused extensive damage in the past. In 1989, for instance, a huge CME damaged satellites, shutdown a Quebec, Canada power grid, and showered Texas with an extremely rare aurora.
A new study by researchers at Lockheed Martin has revealed that about 4 percent of power disruptions in the U.S. from 1992 to 2010 were associated with elevated solar activity — the kind of activity that releases CMEs. This finding clashes with government reports that blamed zero disruptions on solar activity during that same time period.
|A long filament erupted from the sun on August 31, 2012, emitting a coronal mass ejection. |
Image Credit: NASA/GSFC/SDO
Ignition and Induction
When solar flares release the charged particles found in CMEs, it takes several days before they reach Earth. Upon arrival, the fast-moving charged particles create currents in the Earth's atmosphere, similar to the currents that flow through wires for electrical devices.
But these currents are huge. A flow of charged particles such as those in CMEs have accompanying magnetic fields that increase with the size of the current. In turn, these changing magnetic fields induce currents in nearby conductors such as power lines. If the induced current reaches a high enough point, the power grid can become overloaded, leading to blackouts such as the one that happened in Quebec in 1989.
Lockheed Martin scientists Carolus J. Schrijver and Sarah D. Mitchell suspected that these CMEs may have been behind other power disruptions in the past, prompting them to dig into the data. For their research, Schrijver and Mitchell used grid disruption data collected by the federal government and an organization of utility operators across North America. In total, the data covers over 300 million customers in the U.S. and Canada.
Comparing this data with instances of elevated solar activity, the researchers found that 4 percent of the reported power distributions from 1992-2010 were strongly correlated with heightened solar flare activity.
The two scientists compared power disruptions that occurred near heightened solar activity with power disruptions that happened during periods of low solar activity. Most disruptions stem from other causes (e.g. vandalism, local weather events, or fuel price changes), so the researchers controlled for these other factors when comparing solar activity levels.
In the words of Schrijver and Mitchell, "the null hypothesis that the US power grid is insensitive to space weather is rejected with more than 0.975 (or 32 in 33) probability" (3-sigma confidence).
The official government reports, however, tell another story. Solar activity was never cited as a primary cause or contributing factor to a power disruption over the 19-year time period, according to Schrijver and Mitchell. While the authors caution that their research doesn't necessarily suggest that geomagnetic storms are the primary cause of the 4 percent of outages.
Nonetheless, they believe that geomagnetic storms were likely a contributing factor.
For instance, Schrijver and Mitchell suggest parallels between geomagnetic storms and skier-caused avalanches. When snow and weather conditions are just right, sometimes all it takes is the small disruption from a skier to trigger massive avalanches. Similarly, geomagnetic storms have the potential to cause widespread outages when other conditions render the power grid susceptible.
Schrijver and Mitchell's paper was recently published in the Journal of Space Weather and Space Climate, according to their arXiv submission.