Auroral Oval : ?The ring-shaped belts of auroral activity around the north and south magnetic poles. The auroral oval expands and contracts over a period of hours and days, depending on geomagnetic activity
Space Science Institute (SSI),Space Weather Center, Glossary of Space Weather-Related Terms, Colorado, USA 2011. http://www.spaceweathercenter.org/glossary/001/01. html, (Space Wthr - Amer) {860}