Seeing a federal agency update its forecast every thirty minutes has a subtle unnerving quality. Usually, science doesn’t operate like that. Science is patient, methodical, and based on collected data. However, NOAA’s Space Weather Prediction Center found itself doing something more akin to live journalism than long-range forecasting when a cluster of coronal mass ejections launched from an already agitated region of the Sun started arriving at Earth with more force than anyone had anticipated. This involved watching instruments, reading signals, and pushing new assessments before the previous ones had time to settle.
It began with a sunspot, as these things frequently do. Since mid-August, attention has been focused on Active Region 3078, a compact and magnetically complex grouping located in the southern hemisphere just west of the Sun’s central meridian. It was small but unusually stressed, according to forecasters; this type of tight, twisted magnetic configuration tends to release energy abruptly and without much notice. It released an M5-class flare on August 16 just before four in the morning Eastern time, which was powerful enough to cause a moderate radio blackout over portions of the Earth’s daylight surface. It would have been a noteworthy event on its own. However, Region 3078 was not finished.
Each of the subsequent coronal mass ejections, which started on August 14, contained billions of tons of solar plasma embedded in magnetic fields that were significantly stronger than the interplanetary baseline. These are not mild disruptions. In fifteen to eighteen hours, a fast CME can travel the distance between the Sun and Earth. The slower ones require several days. It’s not the travel time that makes them difficult to predict, but rather what occurs when they get there. The orientation of the magnetic field frozen inside the plasma cloud has a significant impact on the strength of any ensuing geomagnetic storm.
Like a key into a lock, a southward-pointing field penetrates Earth’s magnetosphere. A northward one mostly veers off course. Part of the reason NOAA’s DSCOVR satellite, which sits at the gravitational balance point between Earth and the Sun, is so important is that that orientation only becomes apparent minutes before arrival. As the final warning station, it can provide 15 to 60 minutes before the storm front arrives.
On their five-level scale, NOAA had originally predicted a G3 storm to arrive late on August 18, with moderate G2 conditions the next day. Up until August 19, a geomagnetic storm watch was in effect. Then the DSCOVR data began to arrive. More powerful than that, the storm came. Although the precise amount that forecasts were exceeded in real time is still unknown, the rapid, continuous, and almost nervous pace of updates indicated that the event was progressing faster than anticipated.
At this level, geomagnetic storms are more than just atmospheric phenomena. They exert pressure on the electrical grid, slightly distort satellite orbits, and impair GPS accuracy in ways that aren’t always evident until a navigational system exhibits unusual behavior. Communications over the radio break down. In metal infrastructure, pipeline operators keep an eye out for induced currents. When space weather intensifies, utility companies and airlines discreetly monitor these operational risks rather than theoretical ones.
But the auroras are completely different. According to NOAA estimates, northern lights could be seen during this storm as far south as Pennsylvania, Iowa, and Oregon, latitudes that hardly ever see them. Observing people post pictures of auroras taken in suburban backyards gives the impression that, for a brief period, the event gave people who had never considered the invisible infrastructure of space weather a sense of reality. Perhaps that is the most beneficial thing a storm like this can accomplish. This is not how every CME strikes. Some, though, will strike more forcefully. By late August, Region 3078 appeared to be weakening, with imagery suggesting deterioration. The Sun might be standing down for the time being.
