Three rapid bursts of charged particles that erupted toward Earth from the sun’s burning-hot outer atmosphere on Wednesday could lead to stunning auroras across a wide swath of the US and a colorful hue as far south as Florida to start the weekend.
Traveling at more than 1.5 million miles per hour, the trio of coronal mass ejections (CMEs) have merged into one pulse of plasma and magnetic field during the 60-hour trip from the sun’s atmosphere toward our own.
Tracking these developments, experts at the National Oceanic and Atmospheric Administration’s Space Weather Prediction Center issued a “severe geomagnetic storm watch” in advance of its arrival. This was the first such alert issued by the agency in nearly 20 years.
Visible auroras are possible across much of the United States as a result of this expected storm. An event of this magnitude is also likely to cause disruptions to radios, satellites, and possibly even some power grids, though nothing most people should be concerned about.
This weekend’s aurora potential started with a sunspot more than 10 times larger than Earth. It’s a sunspot so large, in fact, that it’s visible to the unmagnified eye through a leftover pair of eclipse glasses.
Solar flares and CMEs are often associated with sunspots. Larger and more intense spots can lead to more frequent and more intense releases of matter from the sun’s atmosphere.
Satellites dedicated to tracking solar activity detected the first CME rushing out of the sun’s corona around 9:00 am EDT on May 8. A second, smaller CME erupted from the same region a few hours later, followed by another burst of charged matter about eight hours after that.
All three CMEs erupted with different intensities and speeds. The first CME was the largest and slowest of the trio, which allowed the second, faster CME to collide and merge into the first. The third CME of the bunch would eventually catch up as well, allowing all three surges of charged particles to reach Earth in a single wave about 60 hours after ejecting from the sun.
The combined intensity of the three CMEs washing over Earth’s atmosphere at once is the driving force behind the severe geomagnetic storm.
If everything stays on track, a memorable series of auroras could grace the skies over much of the United States during the overnight hours Friday into early Saturday morning.
The timing of the event places the likely peak disruption in the middle of the night across the US, providing a great viewing opportunity for most of the country if the event remains on course.
A geomagnetic storm of this intensity could make the aurora visible overhead from Seattle to Chicago to New York and Washington, DC, with auroras possible as far south as Oklahoma City and Raleigh, North Carolina. Colors may be visible on the northern horizon as far south as northern Florida.
Folks across Europe and Asia may also see the auroras if the storm arrives during their nighttime hours. During the peak of an event of this magnitude, the northern lights could dance overhead around London, Paris, Berlin, and Moscow.
Getting away from city lights and cloud cover is the best way to see any colors in the sky. The darker and clearer, the better.
While an aurora is the most visible and widely anticipated effect of this solar spectacle, it could have some unwanted side effects as well.
Scientists rate the intensity of geomagnetic storms on the G-scale, which ranges from G1 (minor) to G5 (extreme). High-end storms are relatively rare. The Space Weather Prediction Center hasn’t issued a G4-level watch since January 2005.
Most geomagnetic storms are relatively weak and only cause auroras and intermittent disruptions for communities at the highest latitudes. Stronger events can produce auroras deep into the southern latitudes and significantly affect power grids and modern technology.
This weekend’s potential disruptions are likely nothing the average person would even notice, much less have to worry about. A G4 geomagnetic storm like the one predicted could hamper long-range radio frequencies and affect satellite communications. The surge of energy into the upper atmosphere could also affect the precision of GPS satellite signals.
It would take a much larger geomagnetic storm to threaten our modern way of life.
The strongest geomagnetic storm in modern history was the Carrington Event, the result of an immense CME that reached Earth at the beginning of September 1859. Intense auroras lit up the sky like daylight for much of the US, with northern lights visible all the way into the tropics.
The electrical currents induced by magnetic disruptions during the Carrington Event caused power surges throughout telegraph systems. Operators across the US and Europe reported fires, sparks, and even electrical shocks during the event.
Modern power grids are designed with safety systems to protect equipment in the event of an electrical surge like the one induced by a strong geomagnetic storm. If a Carrington-level disruption happened today, though, it could lead to life-altering and long-lasting blackouts around the globe.
