The Sun has given us quite an active solar maximum thus far. As the term implies, the Sun is putting on a big show for us in terms of prominences, flares, and sunspots. In fact, there hasn’t been a single day since 2022 in which the Sun has had no spots, a stark contrast to the solar minimum of 2019 where 219 days (77% of the year) had a Sun devoid of sunspots. This 11-year solar cycle in which the Sun goes from maximum activity to minimum activity and then back to maximum has been observed for several centuries.
Large eruptions on the Sun, known as coronal mass ejections or CMEs for short, have occurrence rates that are also correlated to the solar cycle. Space-based observatories such as the Solar and Heliospheric Observatory (SOHO) observe these events, which gives scientists back on Earth valuable data to determine if we can expect the billions of tons of material ejected are headed for our home planet. While high-energy light such as X-rays only takes about eight minutes to reach us when released by a solar flare, the particles of a CME arrive later. Depending on the strength of the eruption, they can get here in as little as 15-18 hours whereas slower moving CMEs can take several days to reach us.
When the CME’s charged particles reach Earth, our magnetic field acts as a shield to protect our planet and its local environment including satellites in low-Earth orbit. The larger and faster the CME, the more the Earth’s magnetic field is distorted and compressed. The fast-moving particles interact with the atmosphere, exciting the gas molecules and causing them to glow to produce the northern and southern lights (aurora borealis and aurora australis). The colors observed are unique to the gases of our atmosphere. The familiar red and green hues are due to oxygen emission while the not-as-common blues and violets are due to nitrogen. These colors are also produced at specific altitudes. For example, green aurora are found between 60 and 150 miles up while red aurora occur at least 150 miles up. Other colors are produced lower in the atmosphere.
On November 11, 2025, we experienced not one but two large CMEs pummeling our magnetic field at nearly the same time. The combined arrival resulted in aurora being visible at abnormally low latitudes – all 50 states had aurora visible at some point. Scientists use a scale to describe the intensity of a geomagnetic storm that ranges from G1 (weak effects on power grids, mild auroral activity) to G5 (significant effects on power grids/communications and intense aurora extending to lower latitudes). Original predictions forecast about G3 storm, but the geomagnetic storm quickly rose to G4, with is the same level as the storm that produced bright aurora over Tennessee in May 2024.
Dyer Observatory’s all-sky camera, which captures an image every 20 seconds, caught the northern lights shimmering. The show was bright enough that the aurora easily punched through the bright light pollution from Nashville to the north. While the glow was visible over a span of about five hours, there were two short periods where the aurora rapidly brightened, demonstrating how quickly and unpredictably the display can change.
With the Sun still in solar maximum and remaining pretty active for at least the next couple years, additional aurora being visible over Tennessee is a good possibility. A great resource to check out daily is Spaceweather.com, which will post announcements of CMEs and expected impacts. Think you might be seeing aurora? Be sure to check out Dyer Observatory’s Sky Report page, which features the current all-sky image, a movie from the past 24 hours, a link to aurora predictions, and more!