By Ed Browne
A geomagnetic storm has been hitting Earth over the past day or so, peaking in strength on Tuesday morning.
Geomagnetic storms are caused by a short burst of intense activity from the sun known as a coronal mass ejection (CME)—a vast ejection of billions of tons of superheated gas, barrelling toward Earth at 6.7 million miles per hour.
These CMEs carry a magnetic field and vast amounts of radiation, and despite Earth’s best efforts to protect us, thanks to our own magnetic field they can still play havoc with electrical systems.
On October 9, the Space Weather Prediction Center at the U.S. National Oceanic and Atmospheric Administration (NOAA) issued an alert stating that a G2 moderate category geomagnetic storm was predicted to hit the planet on October 11, reducing to a G1 minor storm by October 12.
The center warned of power grid fluctuations, voltage alarms in power systems based at high latitudes, and some high frequency radio fading. It also added it may be possible to see an aurora in New York or Washington State—areas of the U.S. that are normally well below the latitude required to spot the dazzling natural phenomenon.
But by around 8 p.m. on October 11 a G2 storm warning was in place for October 12, with a warning valid from 2 a.m. to 3 p.m. that afternoon.
The latest alert, issued at 10:58 a.m. UTC, at the time of writing noted the G2 storm was underway.
It is unclear at this point if there has been any disruption linked to the moderately strong storm.
The standard way of classifying a solar storm is known as the K-index. It’s used to measure disturbances in the Earth’s magnetic field and has a range of between Kp 0 and Kp 9. Kp 5 or above indicates a geomagnetic storm is occurring, and the Earth was experiencing a high of Kp 6 on Tuesday morning.
Measuring the Storm
Then there are ways of measuring the effects. The NOAA uses the G scale which measures from 1 to 5, with 5 being the highest level.
Tuesday morning’s storm appears to have topped out at G2, and as of the latest NOAA measure the storm’s Kp index was 6.
If a storm of Kp 9 were to strike, life could be significantly disrupted. Power systems would experience issues with voltage control and grids might see complete blackouts.
Spacecraft, like satellites, would become confused as to which way up they were, leading to data and navigation issues. Radio would be out for days at a time. And people looking upwards in Texas or Florida would spot auroras.
Thankfully, storms of such strength do not occur often—on around four days per 11 years. G2 storms such as Tuesday morning’s can occur in 360 days per 11 years.