The instability of a hot horizontal layer of ferromagnetic fluid rotating about a vertical axis has been investigated when the Prandtl numberP < 1. Earlier it was shown that forP > 1 the overstability cannot occur. In this paper the convective and overstable marginal states have been investigated separately forP < 1 and it is found that though convective marginal state is possible for alla, the non-dimensional wave number, and N the Taylor number, the overstability is possible only ifN > (1 +P)π4/(1 −P) and in case the condition is satisfied, overstability is possible for all those values ofa which satisfya2 < [N(1 −P)π2/(1 +P)]1/3 − π2. IfRc(con) andRc(o.s) are the critical values of the convective and the overstable marginal states respectively, then it is also found thatRc(con) <Rc(o.s) providedN is not sufficiently large.
Volume 129 | Issue 5
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