A unified framework for global auroral morphologies of different planets

Abstract

Planetary magnetic fields control energetic particles in their space environments and guide particles to polar atmospheres, where they produce stunning auroral forms. As revealed by spacecraft measurements of the Earth, Saturn and Jupiter, the pathways of energetic particles to these planetary polar atmospheres are diverse, suggesting that there are different coupling processes between their ionospheres and magnetospheres. These planets all have dipole-dominated magnetic fields, rotate in the same direction and are blown by the solar wind, but what controls the global-scale patterns of energy dissipation remains unknown. Based on three-dimensional magnetohydrodynamics calculations, we reveal that the competition between planet-driven plasma rotation and solar-wind-driven flow convection determines the structure of global auroral morphologies. This unified theoretical framework can reproduce polar aurora from the Earth-type to the Jupiter-type based on transition states that are strikingly consistent with the highly variable aurora patterns of Saturn. This generalized description of fundamental magnetospheric physics, proposed here and validated by decades-long observations, is applicable to exoplanetary systems.