Solar storms can disrupt a wired planet, affecting communication and navigation satellites, power grids, defense systems, data centers, weather forecasting, and more. On Monday afternoon, the sun delivered a massive flare, its most powerful energetic strike in some time. For the most part, there was little infrastructure disruption reported. The most significant impact was a beautiful one: the northern lights, usually limited to polar regions, have been visible across Canada, much of the U.S., and .
The event began at 1:09 p.m. ET on Jan. 18, with observatories worldwide detecting what is known as a [coronal mass ejection (CME)]—an explosive burst of superheated plasma and magnetism from the solar surface. From the start, astronomers knew they had spotted a major event. Solar flares are categorized by strength into B-class, C-class, M-class, and X-class, with B being the weakest and X the strongest. Importantly, the scale is logarithmic, so X is 10 times more powerful than M, which is 10 times more powerful than C, and so on. This flare was an X. It was heading our way, and we had to brace for the impact.
Earth has experienced worse events. Within the M, C, B, and X categories, there’s a more precise 1 to 9 scale, where 1 is weakest and 9 strongest—so a B7 is stronger than a B3. The current storm is an [X-class event]. The October 2003 flare [was so powerful that] it damaged detectors, exceeding the 1 to 9 scale and registering an enormous X17 before instruments failed.
Regardless of a storm’s rating, once detected, the [space weather agency] takes action—specifically its Space Weather Prediction Center (SWPC). The SWPC has a scale from 1 to 5, from minor to moderate to strong to severe to extreme. Minor storms have minimal impact on power grids, satellites, and other infrastructure. The most noticeable effect of a minor storm is on migratory animals, which use Earth’s magnetic fields as an internal GPS and can be disoriented by solar magnetism. Northern lights may be visible as far south as Michigan. An extreme storm, category 5, can cause voltage control problems in power grids—possibly leading to grid failure. Satellites can lose orientation, face uplink and downlink issues, and experience electrical charging on their surfaces. Aurorae can be seen as far south as Texas and Florida.
This week’s flare was less powerful, classified as category 4, or severe, potentially causing power grid and satellite disruptions, but to a lesser extent than a category 5. Aurorae were seen in northern California and the Alabama-Mississippi region.
The first humans affected by any solar storm are those in space. [The International Space Station] has been continuously occupied by rotating crews of astronauts and cosmonauts. In case of a coming solar storm, they train to shelter in the two most shielded of the station’s 16 habitable components—the American Destiny module and Russia’s Zvezda—for good reason. Cosmic radiation may increase the risk of [health issues] like cancer, cataracts, and neurodegenerative disease. [This happened] this week.
Other earthly assets [are protected]. Satellites are put into safe mode, with only power, navigation, and communication systems operating, and other systems shut down until the storm passes; airlines avoid polar routes, more exposed to incoming radiation; [power grids] reduce load and rely on protective systems blocking geomagnetically induced currents (GIC). When the solar gale reached Earth at 2:20 p.m. ET on Jan. 19—or 25 hours after the CME erupted—all systems held, and only minor disruptions were reported. The solar wave-front is still affecting Earth but is expected to dissipate by Jan. 21.
The aurorae will linger. NOAA has another scale, the [auroral oval scale], measuring how far from the poles lights will be visible after a solar storm. The scale runs from 1 to 9; this storm [reached scale 5], meaning 27 U.S. states will experience a light show. The moon is cooperating, with only the tiniest sliver visible, creating a very dark sky that enhances the aurora. If you’re in a lucky state, enjoy the show.