Alfvén Waves Identified as Power Source for Auroral Electric Fields
A new study, co-led by the University of Hong Kong (HKU) and the University of California, Los Angeles (UCLA), has identified the power source for electric fields that accelerate particles. These particles, in turn, create auroral displays. Published in Nature Communications, the research indicates that Alfvén waves—plasma waves traveling along Earth's magnetic field lines—are responsible for fueling these electric fields.
The study demonstrated that these waves function as a natural accelerator. They supply energy that propels charged particles into the atmosphere, leading to the generation of auroral lights.
"This discovery not only answers a long-standing question in the physics of Earth's aurora but also offers a universal model applicable to other planets within and beyond our solar system."
Researchers confirmed these findings by analyzing data collected from multiple Earth-orbiting satellites. These included NASA's Van Allen Probes and the THEMIS mission. The collected data provided evidence that Alfvén waves continuously transfer energy to the auroral acceleration region, maintaining the electric fields that would otherwise dissipate.
The HKU team, led by Professor Zhonghua Yao of its Department of Earth and Planetary Sciences, provided expertise in the magnetospheric dynamics of giant planets. Meanwhile, the UCLA team, led by Dr. Sheng Tian, contributed extensive expertise in Earth's auroral physics.