The physical mechanism of the auroras

Synopsis

Although the aurora borealis and aurora australis are frequent and easily observable phenomena, we have only recently understood exactly how they are created. We have long known that this auroral light is caused by high energy electrons colliding with the atmosphere, but not the exact physical mechanism. One theory is that when solar wind disturbs the magnetic field of the Earth, the result is a type of plasma wave called an Alfvén wave. These Alfvén waves then accelerate electrons into the atmosphere, creating the aurora. In a recent experiment, Alfvén waves were created in the lab and the velocity of the electrons was measured, showing good agreement with observations of the aurora. In this talk, I will explain the Alfvén wave mechanism and how it relates to the aurora.