This collaborative project will address feedback mechanisms between the ionosphere and geomagnetic storm dynamics and will investigate a possible role of the ionosphere on the variability of magnetic storm intensity. A particular scientific objective is the investigation of universal time (UT) dependence of geomagnetic storm intensity. A combination of data analysis and numerical experiments will be used to evaluate the effects of the ionosphere on the UT-dependence in geomagnetic storm intensity. This project incorporates numerical experiments using modeling components from the University of Michigan Space Weather Modeling Framework (SWMF) to gain insight into the role of the ionosphere on geomagnetic storm intensity. The study will also use GPS-determined global Total Electron Content (TEC) maps to characterize the middle and high latitude ionosphere during all levels of magnetic activity. Magnetic activity indices and TEC data will be used to empirically evaluate a possible feedback mechanism of the ionosphere on the storm intensity. The data will further be used to constrain the model experiments. Using the coupled space-weather model, SWMF, the project will investigate the degree to which high-latitude oxygen ion abundance changes vs. season and magnetic activity, using the TEC data to evaluate the validity of the ionospheric component of the SWMF simulations.
The northern lights, or aurora, are caused by electrons coming shooting into our atmosphere at very high speeds. As they hit our atmosphere, they excite atoms that glow. The electrons are tied to our magnetic field, and come down into our atmosphere close to both magnetic poles (near the south pole and the north pole). If you were far enough away from Earth, you could see the aurora happening in both hemispheres. Interestingly, the magnetic poles are not aligned with our rotation axis. In fact, the north magnetic pole is offset by about 10 degrees and the south magnetic pole is offset by about 20 degrees. As the Earth rotates, the poles go in and out of sunlight. In essence, this causes them to be warmer during some parts of the day and cooler during other parts of the day. And, since the poles are offset in different directions, when the northern magnetic pole is in sunlight, the southern pole is in darkness, and visa-versa. The goal of this grant was to explore how the offset of the pole, and the warm-cold cycle, has an interplay with the aurora. By this, we mean that if the northern magnetic pole is in sunlight when there is a big auroral display does it get hotter than in the southern hemispheric magnetic pole, which would be in darkness. This is a complicated question, because it has to do with a lot of interesting physics. We found that for very simple aurora displays, the idea was true - the sunlit hemisphere typically reacted stronger (had a larger temperature increase) than the dark hemisphere. What this means is that if the aurora happens during certain times of the day, the atmosphere will become hotter than if it happens other times of the day. This is important to understand because satellites fly through the very top regions of the atmosphere. When the atmosphere becomes hotter, it expands and the drag that the satellites feel increases. This causes the path that the satellite takes to change and become somewhat unpredictable. Ultimately, we would like to understand how our atmosphere behaves so we can predict how it will expand and contract and we can more accurately specify and predict the orbital track of satellites in order to mitigate the possibility of collisions between different objects in orbit around Earth. Our research serves to allow modelers to better understand how the atmosphere reacts to the aurora.
