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Rossby number(ross -bee) Symbol: R 0. The ratio of the rotation period P to the turnover time τc of a convective cell in a star's interior or a planetary atmosphere; τc is the time required for hot gas to rise from the bottom to the top of a convective cell and then fall back as it cools. The Rossby number is a measure of the efficiency of a star's dynamo (which ‘drives' its activity), smaller values of R 0 indicating a greater influence of rotation upon convection, and therefore higher activity, irrespective of the surface temperature of the star.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006
Rossby number[′rȯs·bē ‚nəm·bər]
The nondimensional ratio of the inertial force to the Coriolis force for a given flow of a rotating fluid, given as R0= U/fL, where U is a characteristic velocity, f the Coriolis parameter (or, if the system is cylindrical rather than spherical, twice the system's rotation rate), and L a characteristic length.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.