The effect of a time-sinusoidal magnetic field on the onset of convection in a horizontal magnetic fluid layer heated from above and bounded by isothermal non magnetic boundaries is investigated. The analysis is restricted to static and linear laws of magnetization. A first order Galerkin method is performed to reduce the governing linear system to the Mathieu equation with damping term. Therefore, the Floquet theory is used to determine the convective threshold for the free-free and rigid-rigid cases. With an appropriate choice of the ratio of the magnetic and gravitational forces, we show the possibility to produce a competition between the harmonic and subharmonic modes at the onset of convection.

1.
Berkovsky, B. M., 1978, Thermomechanics of Magnetic Fluids: Theory and Applications, Berkovsky Edition, Hemisphere, New York.
2.
Bashtovoy, V. G., Berkovsky, B. M., and Vislovich, A. N., 1988, Introduction to Thermomechanics of Magnetic Fluids, Berkovsky Edition, Hemisphere, New York.
3.
Finlayson
,
B. A.
,
1970
, “
Convective Instability of Ferromagnetic Fluids
,”
J. Fluid Mech.
,
40
, Part 4, pp.
753
767
.
4.
Shwab
,
L.
,
Hildebrandt
,
U.
, and
Stierstadt
,
K.
,
1983
, “
Magnetic Be´nard Convection
,”
J. Magn. Magn. Mater.
,
39
, p.
113
113
.
5.
Stiles
,
P. J.
, and
Kagan
,
M.
,
1990
, “
Thermoconvective Instability of a Horizontal Layer of Ferrofluid in a Strong Vertical Magnetic Field
,”
J. Magn. Magn. Mater.
,
85
, pp.
196
198
.
6.
Rudraiah
,
N.
, and
Sekhar
,
G. N.
,
1991
, “
Convection on Magnetic Fluids With Internal Heat Generation
,”
ASME J. Heat Transfer
,
113
, pp.
122
127
.
7.
Bashtovoy, V. G., and Berkovsky, B. M., 1973, “Thermomechanics of Ferromagnetic Fluids,” Magnitnaya Gidrodynamica, No. 3, pp. 3–14.
8.
Zaitsev
,
V. M.
, and
Shliomis
,
M. I.
,
1968
, “
The Hydrodynamics of a Ferromagnetic Fluid
,”
J. Appl. Mech. Tech. Phys.
,
9
, No.
1
, pp.
24
26
.
9.
Polevikov
,
V. K.
, and
Fertman
,
V. E.
,
1977
, “
Investigation of Heat Transfer Through a Horizontal Layer of a Magnetic Liquid for the Cooling of Cylindrical Conductors With a Current
,”
Magnetohydrodynamics (N.Y.)
,
13
, pp.
11
16
.
10.
Zebib
,
A.
,
1996
, “
Thermal Convection in Magnetic Fluid
,”
J. Fluid Mech.
,
321
, pp.
121
136
.
11.
Berkovsky
,
B. M.
,
Fertman
,
V. E.
,
Polevikov
,
V. K.
, and
Isaev
,
S. V.
,
1976
, “
Heat Transfer Across Vertical Ferrofluid Layers
,”
Int. J. Heat Mass Transf.
,
19
, pp.
981
986
.
12.
Aniss
,
S.
,
Souhar
,
M.
, and
Brancher
,
J. P.
,
1993
, “
Thermal Convection In a Magnetic Fluid In an Annular Hele-Shaw Cell
,”
J. Magn. Magn. Mater.
,
122
, pp.
319
322
.
13.
Souhar
,
M.
,
Aniss
,
S.
, and
Brancher
,
J. P.
,
1999
, “
Convection de Rayleigh-Be´nard Dans les Liquides Magne´tiques en Cellule de Hele-Shaw Annulaire
,”
Int. J. Heat Mass Transf.
,
42
, pp.
61
72
.
14.
Gresho
,
P. M.
, and
Sani
,
R. L.
,
1970
, “
The Effects of Gravity Modulation On The Stability of a Heated Fluid Layer
,”
J. Fluid Mech.
,
40
, pp.
783
806
.
15.
Biringen
,
S.
, and
Peltier
,
L. J.
,
1990
, “
Numerical Simulation of 3-D Be´nard Convection With Gravitational Modulation
,”
Phys. Fluids
,
A2
, No.
5
, pp.
754
764
.
16.
Clever
,
R.
,
Schubert
,
G.
, and
Busse
,
F. H.
,
1993
, “
Two-dimensional Oscillatory Convection In a Gravitationally Modulated Fluid Layer
,”
J. Fluid Mech.
,
253
, pp.
663
680
.
17.
Gershuni, G. Z., and Zhukhovitskii, E. M., 1976, Convective Instability of Incompressible Fluid, Keter Publisher, Jerusalem.
18.
Shliomis, M., Brancher J. P., and Souhar, M., 1995, “Parametric Excitation in Magnetic Fluids Under a Time Periodic Magnetic Field,” Proceeding of the Seventh conference on Magnetic Fluids, Bhavnagar, India.
19.
Aniss
,
S.
,
Souhar
,
M.
, and
Belhaq
,
M.
,
2000
, “
Asymptotic Study of the Convective Parametric Instability in Hele-Shaw Cell
,”
Phys. Fluids
,
12
, (No.
2
), pp.
262
268
.
20.
Brancher, J. P., 1980, Sur l’Hydrodynamique des Ferrofluides, The`se D’e´tat de l’INPL, Nancy.
21.
Rosenweig, R. E., 1985, Ferrohydrodynamics, Cambridge University Press.
22.
Morse, P. M., and Feshbach, H., 1953, Methods of Theoretical Physics, Part I, Mc Graw-Hill, New York, pp. 556–563.
23.
Jordan, D. W., and Smith, P., 1987, Non Linear Ordinary Differential Equations, Oxford Clarendon Press, New York.
24.
Chandrasekhar S., 1961, Hydrodynamic and Hydromagnetic Stability, Oxford University Press, London.
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