The hemispheric conjugate observation of postnoon "bright spots"/auroral spirals

Abstract

Using the Polar ultraviolet imager (UVI) above the Arctic and the all-sky camera (ASC) at Chinese Zhongshan Station (ZHS) in Antarctica, an outstanding hemispheric conjugate observation of postnoon "bright spots" in the Arctic and auroral spirals in Antarctica is presented. Multiple bright auroral spirals, which are counterclockwise rotation viewed along the direction of the magnetic field, in postnoon auroral arcs are seen on the field of view (FOV) of ASC at ZHS in the Southern Hemisphere, while multiple bright spots are seen at the conjugate FOV of ASC on postnoon auroral oval in the Northern Hemisphere by Polar UVI. We consider that the auroral spirals in postnoon arcs are the visible characteristic of postnoon UV bright spots on ground-based observation and suggest that the current sheet instability above the parallel electric field region, which could produce the arcs, is the origin for bright spots occurring at the ionosphere, and the hemispheric symmetry/asymmetry of postnoon upward field-aligned currents, which is affected by the IMF BY and season, can control the conjugacy/nonconjugacy of postnoon bright spots/auroral spirals between the two hemispheres. Key Points PostnoonAuroral spirals are the visible forms of bright spots on the ground-based imagerPostnoon upward FACs can control the conjugacy of postnoon bright spots ©2013. American Geophysical Union. All Rights Reserved.