At the end of October 2003, one of the most active regions the Sun had produced in years swung into view and opened fire. Over a few days it threw out a barrage of extreme flares and plasma clouds, one after another, straight at the Earth. The storms that followed drove the aurora down to Texas and across southern Europe, darkened a Swedish city, killed a satellite, and sent the crew of the space station into shelter. For the modern satellite era, these are the storms every system is measured against.
What happened
The source was a giant, violent sunspot group. Beginning on October 28, it unleashed some of the strongest flares ever recorded, including an X17 that erupted almost straight toward Earth, and later in the sequence an even larger flare that remains among the biggest ever measured. Each eruption hurled a coronal mass ejection across the ninety three million miles to Earth, and several arrived faster than such clouds usually travel.
When they struck, they set off severe geomagnetic storms over multiple days. This was not one event but a run of them, which is why the plural name stuck. The Halloween Storms were a siege, not a single blow.
How far south it reached
The aurora came down far from the poles. It was seen across the southern United States, with reports from Texas and Florida, and over southern Europe and the Mediterranean, places that may go a decade or more between displays. Millions of people who never expect to see the lights looked up and found them.
What it broke
The damage was spread across sky and ground. In Sweden, the induced currents knocked out power to the city of Malmö for about an hour. In orbit, a Japanese Earth observation satellite was crippled and lost. Airlines rerouted flights away from the polar paths where the radiation and communication blackouts were worst. Aboard the International Space Station, the astronauts moved into the most shielded part of the station to ride out the radiation storm. Instruments at Mars felt it too.
If it happened today
The Halloween Storms are recent enough that the systems they stressed are the systems we still run, only now there are far more of them. More satellites, more polar flights, more GPS dependence, a denser and more interconnected grid. 2003 is the honest modern yardstick, a severe storm in the satellite age, and it is still well short of the worst the Sun has shown it can do.
How we know
Every stage of these storms was watched by spacecraft and ground instruments in real time, from the flares to the plasma clouds to the global aurora and the damage reports. They are among the best documented extreme storms in history, which is exactly why they serve as the modern benchmark.
Would you have seen it from your sky?
In 2003 the lights reached Texas and the Mediterranean over a few short days. The next siege will arrive with little warning. Magna Earth keeps the auroral oval under watch over your exact coordinates and tells you the hour it crosses into your sky, so you are standing under it rather than reading about it the morning after.
Know the night it reaches you — from $14/mo