Eddy diffusivity in convective hydromagnetic systems

• Type: Article in International Scientific Journal
• Date: 2007

Authors

Baptista, M (Author) Other; Gama, SMA (Author) FCUP; Zheligovsky, VA (Author) Other

Journal

Title: European Physical Journal B

Vol. 60

Pages: 337-351

ISSN: 1434-6028

Publisher: Springer Nature

Indexing

ISI Web of Knowledge - 2 Citations

Scopus - 3 Citations

Scientific classification

FOS: Natural sciences > Physical sciences

Other information

Authenticus ID: P-004-5YX

DOI: 10.1140/epjb/e2007-00351-8

Abstract (EN): An eigenvalue equation, for linear instability modes involving large scales in a convective hydromagnetic system, is derived in the framework of multiscale analysis. We consider a horizontal layer with electrically conducting boundaries, kept at fixed temperatures and with free surface boundary conditions for the velocity field; periodicity in horizontal directions is assumed. The steady states must be stable to short (fast) scale perturbations and possess symmetry about the vertical axis, allowing instabilities involving large (slow) scales to develop. We expand the modes and their growth rates in power series in the scale separation parameter and obtain a hierarchy of equations, which are solved numerically. Second order solvability condition yields a closed equation for the leading terms of the asymptotic expansions and respective growth rate, whose origin is in the (combined) eddy diffusivity phenomenon. For about 10% of randomly generated steady convective hydromagnetic regimes, negative eddy diffusivity is found.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 15