On this day in engineering history, a powerful geomagnetic
storm paralyzed the Hydro-Québec power
grid, leaving 6-million customers without electricity for over nine hours. As
the world's largest producer of hydroelectric power, Hydro-Québec provides electricity to the Canadian province
of Québec as well as to parts of the
northeastern United States.
Although the power outage of March 13, 1986 did not extend beyond the Canadian
border, the span of this service failure could have been far greater had it
occurred during the peak-demand conditions of the summer or winter months.
Understanding Geomagnetic Storms
Geomagnetic storms
are temporary disturbances in the Earth's magnetosphere, an extra-atmospheric
zone of charged particles that was discovered by Explorer I in 1958. Earth's
magnetic field captures charged particles (protons and electrons) carried by the
solar wind, an interplanetary stream of ionized particles that flows from the
Sun.
In March 1986, the solar wind brought sunspot-induced auroral electroject
currents (AEC) into Earth's magnetosphere at speeds as high as 900 km/s. These
large, multi-ampere currents flowed in an oval shape and became centered over
Earth's north and south magnetic poles, regions where magnetism is concentrated.
Magnetic Poles and Geomagnetically Induced Currents (GIC)
According to the
American Geophysical Union (AGU), the Hydro-Québec power grid is particularly vulnerable
to geomagnetic storms because of its proximity to Earth's North Magnetic Pole,
which lies off Canada's
Ellesmere Island and shifts across the Arctic . The North Magnetic Pole is the point on the Earth's surface
where the magnetic field is directed vertically downward. When the solar wind
is aligned with this magnetic field, the resulting auroras can be especially intense.
Like many other
parts of North America, Québec is rich in
igneous rock, a geological formation with high electrical resistivity. When
geomagnetic storms occur, the AGU's John G. Kappenman explains, "the high
resistance of igneous rock encourages geomagnetically induced currents (GICs)
to flow in the power transmission lines situated above the rock." The resulting
electrical disturbances can be severe.
The image that
accompanies this blog-entry (top left) depicts the auroral zone created by the auroral
electroject current (AEC) of March 9, 1986. Auroras appear as brightly-colored "lights"
in the Earth's atmosphere, typically in the polar regions. With the Great
Geomagnetic Storm of 1986, however, auroras were visible as far south as Texas.
Resources:
http://www.agu.org/sci_soc/eiskappenman.html
http://adsabs.harvard.edu/abs/1987SoPh..109..119G
http://en.wikipedia.org/wiki/Hydro-Qu%C3%A9bec
http://www.qrg.northwestern.edu/projects/vss/docs/space-environment/3-what-is-solar-wind.html
http://physics.fortlewis.edu/Astronomy/astronomy%20today/CHAISSON/GLOSSARY/GLOSS_M.HTM
http://en.wikipedia.org/wiki/North_Magnetic_Pole
http://www.abc.net.au/science/news/space/SpaceRepublish_1003429.htm
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