Why the Aurora Matters

Aaron Ridley, PhD
University of Michigan

Abstract: The northern (and southern) lights are beautiful displays of dancing lights. They are caused by particles streaming into the atmosphere from the near-Earth space environment causing atoms and molecules in the atmosphere to become excited and when they return to their nominal state, they emit light. In addition, the aurora deposits energy into the atmosphere (causing ionization, chemistry, and heating) and is associated with electric fields. This, in turn, causes even more heating. In response to this, the atmosphere heats up and grows, such that the density at a constant altitude  (like the altitude of the International Space Station) increases - sometimes quite dramatically. Satellites in orbit experience more drag and their trajectories are altered. Our inability to understand and predict these processes hampers our ability to predict to the level necessary the probability of collisions between orbiting objects, which matters a lot in the age of mega-constellations. This talk will explain how the aurora deposits energy into the atmosphere, why our understanding is limited, and what we can do about it.

Biography: Professor Aaron Ridley is gainfully employed at the University of Michigan. He develops global weather models of the upper atmosphere as his primary research - namely the Global Ionosphere Thermosphere Model (GITM) and a new model called Aether. In addition, he has worked on the development of a variety of satellite missions, being the Constellation Scientist for the CYGNSS mission, which measure the winds over the oceans, and the co-chair of the Science and Technology Definition Team for the Geospace Dynamics Constellation mission. He teaches two first year introduction to engineering classes - one based on rocket science and the other on high altitude balloons, has an Coursera MOOC on Rocket Science, and has taught a class on satellite mission design.