The National Weather Service’s Space Weather Prediction Center has downgraded the expected strength of the geomagnetic storm from “strong” (Level 3) to “minor” (Level 1) through Friday.
“The storm has fizzled,” read the headline on SpaceWeather.com, an online hub for space weather information. “Mid-latitude auroras are not likely” for Thursday.
When the sun erupted Monday, it unleashed what’s known as a coronal mass ejection (CME), or a cloud of plasma. The shock ahead of it has already passed Earth. There was a brief response in the planet’s geomagnetic field environment Wednesday night, but not to the degree predicted. There remains a small chance that the solar wind en route could fuel a stronger storm, but the probability is diminishing.
So what happened? With more observations and better physics-based models, why is it so hard to nail these events? At the risk of sounding like an apologist for the space weather forecasters of the world, here’s a short list.
First, the sun is a long way away. Think of the roughly 93-million-mile distance like this. If you scale things to have the sun be the size of a basketball, Earth is then roughly the size of a BB, and they would sit at opposite ends of an NBA-sized basketball court. Plus, the in-between space is dynamic and mostly invisible.
Second, a key element in predicting the impact of a coronal mass ejection is the simple ballistics. That is, will the plasma cloud make a direct hit or a glancing blow? Location, location, location.
Third, what you can’t see kills you. Not only are the speed and trajectory of the CME important, but the embedded magnetic field — invisible in the makings of the CME — is also a huge factor for the strength of the ensuing geomagnetic response on Earth. Forecasters are aware of that only as the CME passes the observations taken 1 million miles upstream. Think of the spin on a baseball; whether it’s a curveball or a two-seam fastball matters.
Lastly, even if auroras, also referred to as the northern lights, materialize, you need clear skies to see them, and it helps to have an unobtrusive moon for the sky to be as dark as possible.
Considering the downgraded geomagnetic storming predicted, skywatchers in the northern United States may opt to sit this one out. In the higher latitudes (northern Canada, Alaska and northern Europe), where the pending solar wind could still give us a bit of a jolt, auroras are probable, and a dim moon will assist viewing.
Even though mid-latitudes are likely to miss out on an opportunity to see auroras Thursday night, this event is one of the first salvos in an uptick of activity occurring in the near future as new Solar Cycle 25 takes hold.