Simulating the aurora borealis

We present an algorithm to simulate the aurora borealis, commonly known as the "northern lights", a natural phenomenon of great visual beauty and considerable scientific interest. The algorithm is based on the current understanding of the physical origin of the aurora. This natural display is mainly caused by high-energy electrons originating in the Sun and entering the Earth's atmosphere in narrow regions centered on the magnetic poles. These electrons collide with atmospheric atoms which are excited to higher energy levels. The excited atoms emit rapidly varying visible light in a curtain-like volume as they return to lower energy levels thereby creating the aurora. By simulating these light emissions along with the spatial and temporal distribution of the entering electrons, we are able to render the major visual aspects of auroral displays. This approach also allows the representation of time-dependent features that characterize the dynamic nature of the aurorae. The applicability of this auroral model for artistic and research purposes is illustrated through comparisons of synthetic images with photographs of real auroral displays.