Red auroras over Japan reach 800 km altitude, signaling new satellite-decay warning sign
Hokkaido University and Okinawa Institute researchers documented red auroras stretching to 800 kilometers above Japan during only moderate magnetic storms. The dense, slow solar wind that produced them also heats the upper atmosphere and drags low-orbit satellites lower, giving Starlink, GPS, and ISS operators a visible early warning marker for orbital decay risk.
Five red auroral events over Hokkaido between June 2024 and March 2025 stretched from 490 to 800 kilometers above the ground, well into Starlink and ISS orbital altitudes. Authors Tomohiro Nakayama and Ryuho Kataoka link them to dense, slow solar wind streams compressing Earth's magnetosphere during only moderately intense storms (peak Dst around minus 110 nT). The same compression heats the upper atmosphere and increases drag on low-orbit satellites. Published May 19 in the Journal of Space Weather and Space Climate.