G2 Geomagnetic Storm May Light 25 U.S. States as CME Nears Earth on June 13

Q: Ancient records show auroras in Japan. Could a future solar storm push the lights that far south again?

Yes. A sufficiently strong future solar storm could push auroras far enough south to be seen in Japan again. The key factor is storm intensity. This weekend’s forecast is only for a moderate G2 geomagnetic storm, with Kp values around 5 to 6, which is enough to bring auroras into parts of the northern and central United States but not nearly strong enough to make Japan a likely viewing area. Auroras reach lower latitudes when the auroral oval expands during much stronger disturbances in Earth’s magnetic field. Historical evidence shows this has happened before. Researchers have cited Japanese records, including a 1204 account from Kyoto, describing red lights in the northern sky at about 35 degrees north latitude. That fits modern understanding that extreme solar storms can produce low-latitude auroras. Recent events support that possibility. During the May 2024 G5 extreme geomagnetic storm, auroras were reported as far south as Texas, Mexico, the Bahamas and the Caribbean—latitudes comparable to or even farther south than much of Japan. The 1859 Carrington Event pushed auroras into the tropics. So the answer is not that Japan would see auroras during an ordinary storm like the one forecast now. But during a rare, powerful event—likely in the upper end of the G-scale, especially G4 or G5—it is scientifically plausible, and historical records suggest it has happened before.

Q: Why do cameras capture brilliant auroras while our eyes often see only faint white glows?

Cameras usually show auroras as brighter and more colorful because they can collect far more light than the human eye can in the dark. At night, human vision relies mainly on rod cells, which are good at detecting faint light and motion but poor at seeing color. The cone cells that detect color need stronger light. So when an aurora is weak or distant, many people see it as a pale gray or whitish glow, sometimes with a hint of green, rather than the vivid reds, purples and greens seen in photos. A camera sensor works differently. With night mode or a long exposure, it can gather light for several seconds instead of the fraction of a second used by the eye-brain system. That lets the sensor accumulate many more photons from the aurora, making faint emissions from oxygen and nitrogen appear much brighter and more saturated. This is why NOAA’s photography advice emphasizes tripods, RAW shooting and low-light modes: the camera needs stability to keep collecting light. The effect is strongest during moderate displays like the G2 storm forecast this weekend. A bright, active aurora can show visible green or even red to the naked eye, especially far from city lights between about 10 p.m. and 2 a.m. But in many cases, the camera is simply better at revealing what is already there but too dim for human color vision to register clearly.

3 articles · Updated · Forbes · Jun 12

Early Saturday in North America, forecasters say a coronal mass ejection could trigger a G2 geomagnetic storm, expanding northern lights visibility well beyond the usual far-northern band.
NOAA currently flags G1 storming on June 13, while the UK Met Office says a glancing CME impact could still produce isolated G2-G3 conditions if the hit is stronger.
Nineteen states could see aurora under a G2 event, including Oregon, Iowa, Illinois, Indiana, Ohio and New York; a stronger G3 storm could extend visibility to 25 states, reaching Kansas, Missouri and Maryland.
Viewing odds remain highly sensitive to the CME's exact arrival and the interplanetary magnetic field's southward Bz, though a near-new moon will help even as short pre-solstice nights limit darkness.