Earth's Ancient Aurora (IMAGE) University of Rochester Caption The larger auroral oval relative to the modern is the result of a weaker dipole magnetic field and stronger solar wind dynamic pressure. The auroral intensity is brighter due to solar wind densities many times greater than those today, and the dominant color reflects greater energies of the precipitating particles and the mildly reducing Paleoarchean atmosphere. Credit Courtesy J. Tarduno and R. Cottrell. University of Rochester Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.