FUNCTION: auroral_zone PURPOSE: IDL function to calculate auroral zone position as a function of magnetic local time (mlt: 0.0-24.0 hours), activity index Q (q: 0-6). Returns corrected geomagnetic colatitude in radians. OPTIONS: To return poleward edge, set poleward. To return latitude, set latitude. To return value for southern oval, set south. To return value in degrees, set degrees. See Holzworth & Meng, GRL 2, p. 377, 1975. Originally written by J. Clemmons, June 1993. Corrected by J.Rauchleiba under the direction of Mike Temerin Apr 1997.