The Northern Lights Could Dip Far South Later This Week

ACROSS AMERICA — A massive geomagnetic storm that hurled a stream of northern lights-producing plasma toward Earth’s magnetic field has intensified, increasing chances more Americans will be treated to ethereal aurora borealis displays this week.

The Space Weather Prediction Center, a division of the National Oceanic and Atmospheric Administration, upgraded its geomagnetic storm watch Tuesday, and now says the northern lights displays may be visible to the naked eye across the entire northern tier of U.S. states and as far south as central Iowa on Thursday.

Some of the farthest-north U.S. states could see the auroras again Friday night as a result of the coronal mass ejection (CME) on the sun. The difference in the aurora borealis forecast is the upgrade in the storm from a G2 (moderate) to G3 (strong) level, which can push the aurora far south.

The storm could have a Kp index — a measure of the strength of geomagnetic storms — of up to 7 at its peak. Geomagnetic storm watches are typically issued by the Space Weather Prediction Center for Kp5 and stronger storms. As shown on the map below, states above the yellow line may see the northern lights this week.

It’s Prime Aurora Time

If this storm is a bust or or you miss the auroras, your chances of seeing the northern lights are greater than ever right now. The reason: Solar Cycle 25. It’s an 11-year cycle in which the sun’s magnetic fields flip polarity, causing solar storms 93 million miles from Earth to occur with much more frequency over the next decade or so.

• Related: Why, Yes, The Chance Of Seeing Northern Lights Is Greater

After solar storms, the auroral oval surrounding geomagnetic poles dips down, explaining why someone in northern Minnesota may see the auroras, but they’re not visible to someone along the same latitude in northern Washington state.

The solar flare Monday was an M4 strength event on a scale of M1 to M9. M-class solar flares are the second largest type, and are capable of producing some brief radio blackouts in the Earth’s polar regions.

During geomagnetic storms, the ovals expand away from the poles and give some lucky people in the United States an ethereal sky show they’ll never forget. In particularly strong storms, people in latitudes as low as Pennsylvania, Oregon and Iowa can see the lights.

The science behind the auroras — in the Southern Hemisphere, they’re called the aurora australis — is complicated. During solar storms, the sun emits electrically charged ions that move away in a stream of plasma, an ionized gas, known as the “solar wind.” The vivid colors glow when the plasma slams into the Earth’s ionosphere about 60 to 80 miles above the planet’s surface.

As the National Weather Service explains the phenomenon, the lights glow “similarly to how a neon sign lights up when electrons pass through inert gas.”