From AMS Glossary
An elliptical band around each geomagnetic pole ranging from about 75° magnetic latitude at local noon to about 67° magnetic latitude at midnight under average geomagnetic conditions. Those locations experience the maximum occurrence of aurorae. The aurora widens to both higher and lower latitudes during the expansion phase of a geomagnetic substorm.
Space Weather Prediction Center, 2018: Aurora. Accessed 13 August 2018. Available at https://www.swpc.noaa.gov/phenomena/aurora.
Term edited 13 August 2018.