The "Great Halloween Solar Storms": 22 Years Ago, One Of The Most Powerful CMEs Ever Hit Earth

Halloween 2003 was a real treat for stargazers, yet rather tricky for astronauts, pilots, and satellite operators. Out of seemingly nowhere, three monstrous sunspots appeared in late October, bombarding the Earth with a series of freakish solar storms that triggered a Halloween light show unlike any other.

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The solar shenanigans began on October 19 and lasted until November 5, with a total of 17 solar flares hurled in our direction during this period. However, the most intense activity was concentrated around the final days of October, when the largest of the sunspots, known as Region 486, unleashed its fury.

More than 13 times the size of the Earth, Region 486 was responsible for 12 of the 17 ejections, including three absolute whoppers. The first of these occurred on October 28 and was given a rating of X17 – even though X10 is typically used to denote the most powerful solar flares.

Hitting the Earth the following day, the deluge of gas and magnetic energy triggered a G5 solar storm – the strongest category – that lasted for 27 hours. However, before this tempest was even over, Region 486 let rip again, this time producing an X10 solar flare that reached us on October 30 and kept the storm going for a further 24 hours.

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As a result, incredibly strong aurorae were seen across the Northern Hemisphere on Halloween, with the spectacle visible as far south in the US as Texas and Florida.

Yet Region 489 still wasn’t done, and cracked out its biggest ejection yet on November 4. This stonker of a flare clocked in at X28, although because it wasn’t aimed directly towards the Earth, it only triggered a moderate solar storm.

However, the Halloween aurorae were not the only outcome of these massive ejections. Onboard the ISS, for instance, astronauts were forced to retreat to the Zvezda service module to shelter from the increased levels of radiation, while all airline flights passing over the North Pole had to be rerouted to avoid the brunt of the bombardment.

It has also been reported that the majority of all the satellites in Low Earth Orbit went offline as a result of the solar storms. The Japanese space agency even had to say adios to its ADEOS-II satellite, which had only been launched the previous year but became irreparably damaged by the Halloween flares.

Luckily, no collisions between satellites or spacecraft were reported during the time it took ground staff to regain control over them. However, with the number of items in orbit having increased dramatically since 2003, any repeat of this solar trickery could now have much scarier consequences.