F regionn. See F layer.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.F region n (General Physics) the highest region of the ionosphere, extending from a height of about 150 kilometres to about 1000 kilometres. It contains the highest proportion of free electrons and is the most useful region for long-range radio transmission. Also called: Appleton layer See also ionosphere Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
F layer
F layern.1. The highest region of the ionosphere, extending at night from about 190 to 400 kilometers (120 to 250 miles) and during the day from about 145 to 400 kilometers (90 to 250 miles) above the earth. Also called F region.2. Either of two layers, designated F1 and F2, into which this region is divided during the day, extending respectively from about 145 to 240 kilometers (90 to 150 miles) and from about 190 to 400 kilometers (120 to 250 miles) above the earth.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.F layer n. the highest radio-reflective region of the ionosphere, at an altitude of ab. 80 mi. (130 km). [1925?30] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.