... Sun-aligned arcs are auroral features found within the polar cap , as opposed to the auroral oval where the more typical arcs reside. First global image of this phenomenon was reported by Frank et al. (1982); it consists of luminous belt reaching across the polar cap from noon to midnigh (that is why it is also called theta aurora; terms transpolar or polar cap arc are also known). ... Res., ... Antisunward decay of polar cap arcs, J. Geophys. ... The Creation of Theta-Aurora, by JHU/APL . ...