Our sun emits more than heat and light.
In addition to photons, the sun propels bursts of gases our way. When these blasts from the solar atmosphere, or corona, are powerful enough to disrupt the earth’s magnetic field, the ripples in energy far overhead become visible as the “northern lights,” more formally called the aurora borealis.
Stronger effects than usual have been observed this year. We are in an active phase of Solar Cycle 25. A solar cycle, about 11 years long, consists of a rise and fall of coronal bursts. 2025 is a year of spiking coronal mass ejections (CMEs) — the 25th since 1755, when they were first noted.
CMEs approach fast, but far slower than light. Whereas the sun’s light (traveling 186,000 miles per second) hits us in eight minutes, a CME (moving about 300 miles per second) can take three days. We have time to prepare. In those three days, astronomers — after watching a tongue of firelike energy erupt from the sun’s outer layer — can gallop across computer screens, barking “The CMEs are coming!”
Evanstonians who heed such alerts can flock to the lakefront and peer into the invisible ionosphere. More than 30 miles overhead, CME energy stimulates nitrogen and oxygen molecules, much as we can stimulate neon in an electrified tube. The excited upper-atmospheric gases release energy as light — reds higher up, greens and blues lower down — as excited observers release colorful shouts. (Or alarmed shouts, as radio or GPS signals are disrupted.)
For alerts, download an app. Or visit the site of NOAA (National Oceanic and Atmospheric Administration) — but understand that the federal government shutdown has delayed routine updates. With public information you can be forewarned of CMEs and their effects — either problematic or lovely. Take advantage of this information. Seize the night. Carpe noctem.