magnetic diurnal variation
magnetic diurnal variation[mag′ned·ik dī′ərn·əl ‚ver·ē′ā·shən]
Oscillations of the earth's magnetic field which have a periodicity of about a day and which depend to a close approximation only on local time and geographic latitude. Also known as magnetic daily variation.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.