MODEL-Z BY COMPUTATION AND TAYLORS CONDITION

The spherical geodynamo model of Braginsky (1978) is re-integrated. Th e original model of Braginsky modified the Taylor's condition to inclu de the influence of viscous core-mantle coupling. Reinstating also the phi-component of momentum partial derivative omega(G)(s)/partial deri vative t [where omega(G)(s) is the geostrophic shear] in the expressio n for the modified Taylor condition makes possible the investigation o f solutions for small viscosities. Above a critical dynamo number D-c, the solution enters a viscously-limited branch (''Ekman'' or ''coupli ng'' branch) and, eventually, as D is further increased, jumps to a st rong-field branch. The original numerical solution of Braginsky belong s to the latter branch and is duplicated. But, with weak viscosities, the solution on that branch is proved inviscid. In that inviscid limit , Braginsky's model meets the Taylor's condition. The same code is use d to re-investigate another alpha omega dynamo model defined by a simp ler choice of alpha and omega effects [alpha = R(alpha) cos theta, ome ga = R(omega)(r - 1)].