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Remembering the Great Halloween Solar Storms

Artwork of a witch flying in front of an aurora
Courtesy of the U.S. Geological Survey

Over a decade ago, the sun played a rather spooky Halloween trick on the planet when it unleashed a series of massive solar storms in late October 2003, some of which hit the Earth. With little warning, three massive and very intense sunspot groups had emerged on the sun's surface by October 26, with the largest measuring over 13 times the size of Earth. Due to their extreme size and complex structure, 17 major solar flares—including one of the largest ever recorded—accompanied the sudden increase in sunspots.

A Day for the Record Books

On October 28, the largest of the sunspots ejected an enormous solar flare—one of the largest ever recorded at the time. A very fast-moving burst of gas and magnetic energy from the sun's outer atmosphere, known as a coronal mass ejection, and a geomagnetic storm quickly followed, with the storm growing to become the sixth most intense in over 70 years. Less than 24 hours later, the sun produced another powerful Earth-directed coronal mass ejection with another extreme geomagnetic storm following quickly on its heels.

While the Earth's atmosphere protects us from the dangerous high-energy particles and radiation that solar flares produce, technological systems around the world and in space felt the full of effects of the flares and subsequent geomagnetic storms. Everything from satellites to GPS to radio communication experienced problems or outages due to the severe activity.

Tricks and Treats

The storms affected over half of the Earth-orbiting spacecraft, intermittently disrupting satellite TV and radio services and damaging a Japanese scientific satellite beyond repair. The solar activity also sent several deep-space missions into safe mode or complete shutdown and destroyed the Martian Radiation Environment Experiment aboard NASA's Mars Odyssey mission. At the height of the storms, astronauts aboard the International Space Station had to take cover from the high radiation levels, which had only happened twice before in the mission's history.

The solar storms also led to communications problems for airline flights between North America and Asia over the North Pole, disrupting operations. Antarctic science groups also had a full communications blackout for over 130 hours due to the storms. And, the storms seriously affected GPS systems used for surveying, deep-sea and land drilling, and other airline flights.

Despite the tricks played on our technological systems, the Great Halloween Solar Storms of 2003 also gave us a treat. The extreme and prolonged geomagnetic storms brought widespread middle and even low latitude aurorae with them on October 29 and 30. Aurora sightings occurred from California to Texas to Florida. People in Australia, central Europe, and even as far south as the Mediterranean countries also reported tremendous aurora viewing.

For more information on this storm event, see the Intense Space Weather Storms, October 19 - November 7, 2003, Service Assessment. And, check out satellite images and videos from the Great Halloween Solar Storm and other significant events on our GOES Solar X-ray Imager Greatest Hits.

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