The objective of this project was to obtain better mappings of the auroral currents that flow into and out of the polar ionosphere, and how they vary as a function of the magnetic field in the solar wind. One main goal was to determine the response of these currents to extreme levels of solar wind conditions, as determined by the product of the wind velocity and the strength of the magnetic field, the solar wind's electric field.  The electric fields and voltages in the polar ionosphere are known to increase in proportion to the level of the solar wind driving, up to a certain point, then increase at a much lower rate as the driving increases.  This is known as the "electric potential saturation," the causes of which have been the subject of considerable debate within the space science community. This saturation effect is also important to the understanding of the physics of the solar wind-magnetosphere-ionosphere interaction.   What wasn't known was whether or not the currents exhibit the same saturation behavior, as these currents are more difficult to measure than the electric fields.  The second main goal was to obtain better mappings of the current distribution as a function of the solar wind and its magnetic field, and to be able to predict theis response. These currents are strongly coupled to the geomagnetic perturbations that occur on the ground, and the heating of the upper atmosphere, both of which can have undesired effects on infrastructure.
These objectives were accomplished by the use of measurements of the magnetic fields above the Earth's atmosphere, from which the currents are deduced. A large database was constructed of measurements from three different satellite missions named Oersted, CHAMP, and Swarm, spanning a period of approximately 14 years, and accompanied by measurements of the solar wind by NASA's ACE satellite. Measurements of solar radiation at different wavelengths, as indicated by four different indices, were also used.

It was found that the total current does NOT saturate as the magnitude of the solar wind electric field increases; the relationship is linear. This behavior is very much unlike the polar cap electric potentials, and it holds for all current regions. To help with the data analysis, a software tool was developed to automatically sort and sum the current going to or from different regions, based on traditional classifications that have been referred to as "Region 0", "Region 1", and "Region 2," not a trivial task. A new, predictive computer model for the current mappings has been produced. It has much greater resolution and accuracy than previous models, and it will be useful for future scientific studies as well as forecasting the space environment.

Last Modified: 07/06/2017
Modified by: Daniel Weimer