The sun sure has woken up this week, unleashing a powerful X-class solar flare on Jan. 18 that hurled a colossal, fast-moving coronal mass ejection (CME) directly toward Earth. That CME has now arrived, triggering severe (G4) geomagnetic storm conditions far earlier than initially forecast.
The shock wave from the CME struck at 2:38 p.m. EST (1938 GMT) on Jan. 19, according to NOAA’s Space Weather Prediction Center, which confirmed that G4 storm levels were reached shortly after impact. The storm is ongoing, and space weather forecasters say CME passage will continue through the evening, keeping the door open for more aurora activity tonight.
Related: Northern lights may be visible in 24 states tonight as a massive CME slams into Earth
Why the CME’s impact depends on its magnetic orientation
CME arrivals are notoriously difficult to forecast. Their speed, direction of travel and — most importantly — their magnetic orientation all determine how strongly (if at all) they will interact with Earth’s magnetic field.
If the CME’s magnetic field is oriented southward, a component known as the Bz, it can more easily link up with Earth’s northward-pointing magnetic field, allowing energy to pour into our planet’s magnetosphere and trigger geomagnetic storm conditions.
If the Bz is instead oriented northward, Earth’s magnetic field largely deflects the incoming energy, effectively “closing the door,” and what looked like a promising space weather event can end up being a bit of a nothing burger.
Some CMEs contain a mixture of southward and northward magnetic fields, which can lead to stop-start or fluctuating geomagnetic activity. These events keep space weather forecasters and aurora chasers very much on their toes.
Even now, after the CME has arrived, we won’t fully understand its magnetic orientation until it’s sampled in real time by solar wind monitoring spacecraft like DSCOVR and ACE, positioned upstream of Earth.
What’s an X-class solar flare?
Solar flares are ranked in ascending strength from A, B, C and M up to X, with each letter representing a tenfold increase in intensity. X-class flares are the strongest eruptions and the number following the X indicates how powerful the event is. Today’s flare was measured at X1.9, putting it in the upper tier of solar outbursts.
The powerful flare from sunspot region AR4341 peaked at 1:09 p.m. EST (1809 GMT), according to NOAA’s Space Weather Prediction Center. The eruption triggered strong (R3) radio blackouts across the sunlit side of Earth, with the most severe disruptions concentrated over the Americas.
What is a CME and how can it affect Earth?
A CME is a massive expulsion of plasma from the sun that carries a magnetic field. If a CME hits Earth’s magnetosphere — the protective magnetic “bubble” generated by our planet — it can trigger a geomagnetic storm.
These geomagnetic storms vary in intensity and are therefore classified on a scale from minor (G1) to extreme (G5). Current forecasts from the U.K. Met Office suggest the incoming CME could produce strong (G3) to severe (G4) geomagnetic storm conditions.
Storms of this magnitude can disrupt satellite operations, degrade GPS navigation and increase atmospheric drag on spacecraft. They can also supercharge auroral activity, potentially pushing the northern lights far beyond their usual high-latitude haunts and into mid-latitude regions near 45° latitude.
Editor’s note: This article was updated on Jan. 19 at 4:30 p.m. EST (2130 GMT) to reflect that the coronal mass ejection (CME) has arrived and triggered G4 (severe) geomagnetic storm conditions, according to NOAA. Forecasts and visibility potential may continue to evolve as the storm progresses.
Author: Daisy Dobrijevic
Source: Space.com
Reviewed By: Editorial Team
