Japanese Researchers Find Red Auroras at 500-800 Km, Challenging Moderate Storm Readings
Updated
Updated · ScienceDaily · May 23
Japanese Researchers Find Red Auroras at 500-800 Km, Challenging Moderate Storm Readings
2 articles · Updated · ScienceDaily · May 23
Five auroral events over Hokkaido from June 2024 to March 2025 showed faint red glows reaching about 500 to 800 kilometers above Earth—far above the usual 200 to 400 kilometers.
The team says dense solar-wind streams compressed Earth’s magnetosphere so strongly that the upper atmosphere heated and expanded upward, while standard geomagnetic indices still labeled the storms only moderate.
Satellite data and citizen-scientist photos from multiple sites across Japan let researchers triangulate the auroras’ height by mapping the images along Earth’s magnetic field lines.
Those hidden stronger storms could matter for low-Earth-orbit spacecraft, because a heated, expanded upper atmosphere increases drag and can alter satellite trajectories faster than expected.
If 'moderate' solar storms are this powerful, how vulnerable is our critical infrastructure to a truly severe event?
Why are our space weather models failing to predict the true power of solar storms hitting Earth?
With known solutions to protect our power grid, why does our infrastructure remain so exposed to a devastating solar threat?
High-Altitude Red Auroras Over Japan: A New Warning Sign for Satellite Safety and Space Weather Forecasting
Overview
In December 2023, a surprisingly bright red aurora was seen with the naked eye from Hokkaido, Japan. This rare event occurred at an unusually high altitude of 400 to 600 km, much higher than typical auroras. A research team from Nagoya University and The University of Tokyo, led by Associate Professor Ryuho Kataoka, investigated the phenomenon. They combined satellite data with photographs from citizen scientists across Japan. By analyzing the angles of these images and mapping them along Earth's magnetic field lines, the team accurately reconstructed the aurora’s vertical structure, revealing new insights into how such high-altitude auroras can appear during only moderate magnetic storms.