Physics and Effects of a Geomagnetic Storm
A geomagnetic storm is the result of a solar flare and an associated coronal mass ejection. A large explosion in the sun’s atmosphere releases magnetic energy stored in its corona and a massive burst of solar wind then carries huge quantities of matter and electromagnetic radiation into space. Depending on its velocity, this solar wind can reach our planet in approximately one to three days. When it does, the shock wave of the atomic particles from the coronal mass ejection interacts with the earth’s magnetic field generating disturbances. These disturbances are referred to as geomagnetic storms and cause geomagnetically induced currents (GIC) in long conducting networks. GICs can seriously affect the safety and performance of critical infrastructure assets such as high frequency telecommunication and electrical power grids, space satellites, data centers, GPS and SCADA systems. They can even increase corrosion in oil and gas pipelines. In a world driven by the sophistication and interconnectedness of our modern technology, any damage is further amplified.
Probability of Event versus Economical Cost
Solar activity cycles in an average period of about eleven years, causing solar variations ranging from the lowest period of activity, called the solar minimum, to the highest activity period, the solar maximum. We are currently in Solar Cycle 24, which began in January 2008. It is believed that the release of the February 15 flare signals the beginning of the solar maximum for this cycle, which is predicted to peak in 2013.
First recordings of solar storm generated effects date back as early as 1847 when telegraph services had been interrupted in Great Britain, followed by the largest storm known to date, the Carrington Event in 1859, which almost entirely shut down the US telegraph system. Because of our dependency on sensitive technology and its interconnectedness, an event of similar magnitude nowadays could cost $1-2 trillion and take 4-10 years to recover. This article, however, does not intend to focus on worst case scenarios, rather aims to point out how even smaller, thus more probable geomagnetic events can cause severe economic damage as we rely more and more on modern technology in every walk of life.
For example, on March 13, 1989 several transformers on the Hydro-Quebec power grid were damaged from GIC, resulting in a domino effect shutting down the entire grid for 9 hours, affecting 5 million people and costing $2 billion. Over 200 concurrent events had been reported in North America, including a destroyed transformer at the Salem nuclear plant in New Jersey. Since the 1989 blackout, Hydro-Quebec has invested more than $1.2 billion in protection measures - a clear indication that the magnitude of economic damage from GIC may warrant significant investments to protect against their damaging effects.
Transformers are particularly vulnerable as GIC causes a voltage differential between grounding points, which leads to transformer saturation, and possible overheating, shutdown or even destruction of the equipment. At costs of $10 million each and extended lead times for replacement, protection of these assets seems economically imperative. Cumulative effects of GIC in systems deployed in higher latitude areas, which are more susceptible to geomagnetic events, further decrease the life cycle of the equipment. Incidentally, the northeastern region of the US with the highest rates of detected geomagnetic activity shows 60% more failures in transformers coinciding with the eleven-year solar cycle. Nevertheless, while areas of higher latitude with their larger magnetic field variations generally experience greater exposure to GIC than areas of lower latitudes, during times of increased solar activity storm events have been observed much farther south with some even occurring close to the equator.
Industry groups and the scientific community agree that a combination of system hardening and operational strategies may provide the best mitigation strategy. While it is not economically feasible to harden an entire network system, installing a passive device or a circuit to block or reduce GIC in key assets such as transformers is deemed both effective as well as feasible. Operational mitigation measures on the other hand include temporary removal of key assets and separation of interconnected systems in response to solar storm warnings and alerts. This approach relies on the accuracy and timeliness of solar storm forecasting, which in the US is handled by the Space Weather Prediction Center of the National Oceanic and Atmospheric Administration. Through a fleet of satellites, their monitoring and predictive capabilities are continuously improving.
Understanding what protective measures can be employed to help protect critical assets is the first step in effective risk mitigation. Methods of hardening facilities and assets are well understood and already being employed by the military. At this point, we cannot accurately predict geomagnetic storm activity or prevent the effects on Earth from a large storm. However, with proper planning and protective measures, we may be able to reduce the overall damage and protect high-value assets so that when power is restored critical infrastructures and industries are ready to come back online.
Rod Rawls and Susann Ferrari
Protection Technology Group