More displays of Northern Lights are likely in the coming weeks and months—including this weekend—after the revelation that there were more sunspots on the sun during July 2024 than at any time since December 2001, scientists say.
Sunspots are magnetic disturbances on the sun’s surface that can be as big as Earth. They’ve been counted every day since 1611, according to NASA, and indicate how magnetically active the sun is.
As reported by spaceweather.com, the monthly average sunspot number for July 2024 reached 196.5, according to the Royal Observatory of Belgium’s Solar Influences Data Analysis Center.
It comes after a week of “photographic displays” of the Northern Lights in North America, which now look likely to be repeated this weekend.
Counting Sunspots
Sunspots are where solar flares on the sun originate, frequently followed by coronal mass ejections. A solar flare is an intense blast of radiation from the sun that travels at light speed, taking only eight minutes to arrive at Earth. Solar flares can cause radio blackouts, but not aurora.
However, CMEs hurl magnetic fields and charged particles into the solar system at up to 1,900 miles (3,000 kilometers) per second. If they are traveling in Earth’s direction, they can cause geomagnetic storms—and that’s what causes the Northern Lights. They can take a few days to reach Earth.
This Weekend’s Displays
In the wake of an M8-class solar flare, an Earth-directed CME is expected to arrive at Earth this weekend, likely triggering a G2-class geomagnetic storm, according to NOAA’s Space Weather Prediction Center. G2 storms can generally be seen as far south as New York and Idaho; for G3, it’s Illinois and Oregon; for G4, it’s Alabama and northern California.
For the latest updates, check the SWPC’s latest “aurora view line,” which represents the southernmost locations from which you may see the aurora on the northern horizon.
May 10’s extreme G5 geomagnetic storm, which caused displays of aurora worldwide, was rated as a G5—the highest possible. That’s not what’s happening this weekend.
Solar Cycle 25
The sun has a roughly 11 year solar cycle during which the sun’s magnetic activity waxes and wanes. It’s now on the cusp of “solar maximum”—its peak period of activity—which is determined by counting sunspots on the sun’s surface. We’re currently in Solar Cycle 2025, which began in 2019.
However, while May saw the most sunspots since December 2001, Solar Cycle 2024 peaked in July 2000 when 244.3 sunspots were counted, according to the SWPC. That suggests that Solar Cycle 2024 could yet get more intense, though the SWPC’s latest forecast is for the maximum to occur between August 2024 and January 2025.
What Causes Aurora
The Northern Lights are caused by the solar wind, a stream of charged particles from the sun. As they strike Earth’s magnetic field, they accelerate down its magnetic field lines at the north and south poles to create ovals of green and red. They’re typically visible to those near the Arctic Circle, such as Alaska, northern Canada, or northern Scandinavia (Norway, Finland, Sweden, and Iceland).
However, if there are many solar flares and CMEs, the solar wind can become much more intense, with those ovals stretching further south. When that happens, those in North America can sometimes see the Northern Lights as a faint glow on the northern horizon.
Pick up my books Stargazing in 2024, A Stargazing Program For Beginners and When Is The Next Eclipse?
Wishing you clear skies and wide eyes.
