On certain nights in Japan, a faint red glow spreads low across the horizon. It looks like a dim crimson haze, easy to overlook. But that soft light comes from charged solar particles colliding with oxygen atoms hundreds of kilometers above Earth, and new research shows it reaches far deeper into space than anyone expected.
Red glows that tower above the ordinary
A team from Hokkaido University and the Okinawa Institute of Science and Technology studied five red auroras spotted in Hokkaido between June 2024 and March 2025. These auroras extended roughly 500 to 800 kilometers above Earth’s surface. That is far higher than typical auroras, which form at altitudes of 200 to 400 kilometers. The findings were published in the Journal of Space Weather and Space Climate.
Lead author Tomohiro M. Nakayama said he was surprised to see such tall auroras during storms that standard measurements classified as moderately intense. The red glow appeared even when space weather indices suggested the solar activity was not extreme.
What made the auroras climb so high
Researchers believe dense streams of solar wind compressed Earth’s magnetosphere so strongly that the upper atmosphere heated up and expanded upward. That expansion pushed the region where red auroras form to much higher altitudes. At the same time, the movement of charged particles may have masked the true intensity of the storms, making them appear weaker according to traditional space weather measurements.
The team combined satellite observations with photographs taken by citizen scientists across Japan. By studying the angles of the auroras in those images and mapping them along Earth’s magnetic field lines, they reconstructed the true height of the glowing displays.
Why this matters for satellites and space weather
If moderately intense storms can produce auroras at 800 kilometers, those storms may actually be stronger than conventional indices indicate. That has consequences for satellites orbiting Earth. Many satellites operate in the region between 400 and 800 kilometers, where these red auroras now appear. Stronger hidden solar activity could affect satellite electronics, communications, and orbital paths.
The discovery suggests that scientists may need to rethink how they measure the strength of space storms. What looks moderate from the ground may be hiding something more powerful above.
