I found myself staring up at the sky on the night of March 13, 1989, with my girlfriend and her parents in the backyard of their house. The sky was on fire, almost literally. Red and pink sheets of plasma streamed out in a circle from directly overhead, with blue-white streaks like xenon flashes occasionally strobing across the sky. We could actually hear a sizzling, crackling sound around us. The four of us stood there, awestruck by the aurora borealis we were lucky enough to witness.
At the same time, lights were winking out a couple of hundred miles north in Québec province. The same solar storm that was mesmerizing me was causing fits for Hydro-Québec, the provincial power authority, tripping circuit breakers and wreaking havoc. This certainly wasn’t the first time the Sun threw a fit and broke systems on Earth, but it was pretty dramatic, and there are some lessons to be learned from it and other solar outbursts.
The event I witnessed actually started three days earlier as a coronal mass ejection, or CME. A CME is a stream of plasma and tangled lines of magnetic flux, launched from the corona of the sun. It’s not clear what causes CMEs, but they certainly seem to be associated with other solar phenomena like solar flares and sunspots, and generally occur more often during times of high solar activity. Current thinking is that a CME is a magnetic flux rope thrown off by the sun when stressed magnetic fields inside the sun interact, releasing tremendous amounts of stored magnetic energy. These ropes expand out from the sun like a growing donut, picking up billions of tons of plasma from the sun’s corona and propelling it ahead of itself at a million miles an hour.
In some cases, these expanding clouds of plasma are Earth-directed, like in March of 1989. After a few days of travel, the expanding donut reaches the Earth’s magnetosphere, which is the limit of influence of the Earth’s magnetic field. The leading edge of the CME forms a shock wave that flattens the magnetic field on the day-side of the globe. This allows charged particles to slip into the Earth’s atmosphere, causing the aurora I saw at around 42° North latitude – a little far south for regular display of the Northern Lights, but not so far that they were unheard of. The 1989 CME was so powerful that it caused aurorae clear down to Florida, and even Cuba witnessed the display.
The Path of Least Resistance
As amazing as the aurorae in the 1989 CME were, they weren’t what caused so many headaches for Hydro-Québec. The action there was caused on the backside of Earth, away from the Sun. While it was compressing the day-side magnetosphere, the CME shock wave was also stretching out the night-side magnetosphere into a long tail of magnetic flux. Just like the collapsing magnetic fields inside the sun that started the CME in the first place, eventually the magnetic lines of force in the tail reconnected, releasing terawatts of stored energy back toward the Earth.
This is where the trouble started for Hydro-Québec. All that electrical energy needed to go someplace, and as is always the case, it took the path of least resistance. Most of the province of Québec sits atop a massive insulating sheet of igneous rock called the Canadian Shield, and the thin layer of soil stretched over it was soon conducting massive amounts of current. The ground connections of Hydro-Québec’s transmission system of high-tension lines and transformers eventually started conducting some of these earth currents, and at 2:43 AM, protective circuit breakers tripped at the Chibougamau substation in central Québec. This caused an imbalance on a 750 kV transmission line, which tripped breakers 150 km away.
Within one minute, the cascading failures had tripped automatic systems all over Québec, shutting down 21 gigawatts of supply and plunging the province into darkness for over nine hours. The cascade of failures wasn’t limited to Canada; thanks to interconnects between the US and Canadian grids, over 200 grid faults occurred within the first few minutes in the US. Operators were able to shunt around issues and avoid any major blackouts, though.
To their credit, Hydro-Québec didn’t just chalk this up to an act of God and continue with business as usual once the dust settled. They learned the lessons the sun had to teach them that day, and put in systems to prevent a recurrence. The simple expedient of decreasing the sensitivity of the protective relays that first caused the problem has avoided a repeat in similar storms; there was another CME in August of 1989 that scrambled computers at the Toronto Bourse but failed to result in any major blackouts. Hydro-Québec also set up an early warning system to keep an eye on space weather, and changed policies with regard to switching operations and power levels when storms are predicted.
As memorable as the event was for those of us lucky enough to have seen the pyrotechnics, it was probably far more memorable for the six million Canadians who woke up to cold, dark houses, crippled traffic systems, and closed airports. Watching that display of nature’s quiet fury, and finding out the extent of the damage the next day, only served to underscore how puny we are, and how vulnerable our systems are no matter how hard we try to pretend otherwise.