“When the Sun ‘sneezes,’ Earth’s technology can detect it.” In this instance, the offender is a one-two punch: X-class solar flare coupled with a coronal mass ejection, followed by a strong solar wind jetting out through a large hole in the corona. The cumulative effect: Earth finds itself in G4 severe geomagnetic storm conditions, a strength known to have sufficient electrical current to surge through the upper atmosphere, Earth’s magnetic field, and even the surface underlying power lines.
But the process starts on the Sun itself, in this case, with an X1.9 flare that served as the prologue to the main event. A flare’s burst of radiation can cause rapid radio blackouts, but the longer-lasting blackout comes in the form of the CME, which is a huge, magnetized cloud of solar plasma that takes about a day to travel the 150 million kilometers to Earth. Upon impact, the CME pushes and squishes the magnetosphere, releasing trapped clouds of charged particles and directing them down the magnetic field lines to the polar atmosphere, where collisions involving oxygen and nitrogen atoms convert their energy into the greens, reds, and purples that make up the aurora’s colors sometimes extending beyond the poles if the storm is intense enough.
The thing that gives this particular event such punch is the “tailwind” driving it. The CME has been pursued by fast solar wind from a coronal hole, and speeds measured during this activity indicate speeds of approximately 1,070 km/s, more than double what normally exists at around 400 km/s. While a fast stream alone can make aurorae brighter, in combination with a CME, Earth’s magnetic environment can remain active for an extended period of time even after the most active viewing period has ended.
The most photogenic of these phenomena would be the aurora, but the most significant effect would not be. Strong geomagnetic storms may affect radio communication, reduce the signals used in navigation, and even cause the need to change the orbit of spacecraft due to increased drag, charging, or sensor malfunctions. For the power grid, the effect would be geomagnetically induced current, which may be caused by the current in the geomagnetic storms, flowing into long conductors like the power grid’s transmission lines, making transformers work harder to manage the voltage.
Even less obvious is the other space weather threat that came a bit prior to the CME: a solar radiation storm. This was S4, the most severe level since 2003. Solar radiation storms involve fast protons that are accelerated from the vicinity of the eruption, some of which travel fast enough that they can strike the Earth in a matter of tens of minutes. While the atmosphere and the magnetic field give excellent protection against radiation at the surface, conditions change higher up. This is where astronauts, satellites, or polar flights can modify their paths or modes of operation.
There is also an operational nuance which engineers understand to be part of the process: high flux can cause space-based observations to be adversely affected. In the case of such solar storms, certain real-time solar wind observations can be rendered inaccurate, leading to greater reliance on the parameters which are not affected.
But for the rest of us, the most immediate effect of the storm is simple: a sky that won’t act like it’s supposed to and a reminder that our modern world exists under the whim of a star with a temperament.
