MIXED-PARITY SOLUTIONS IN A MEAN-FIELD DYNAMO MODEL

We consider the effect of including both dipole and quadrupole paritie s in the previous mean-field model of Hollerbach and Jones (1995), whi ch considered dipole parity only. Allowing for both parities, we find that the onset of dynamo action occurs at alpha(0) approximate to 6, i n the form of a purely quadrupolar dynamo wave. A symmetry-breaking bi furcation then occurs at alpha(0) approximate to 11, beyond which the solutions are of mixed parity. The quadrupolar component still oscilla tes about a zero ti me-average, but the dipolar component about a non- zero average. For Even greater alpha(0) we obtain an unconnected upper -branch solution. In sharp contrast to the HJ95 pore-parity upper bran ch, however, this mixed-parity upper branch a's steady-state rather th an periodic. Although it does not appear to be possible to connect the se two upper branches by any simple sequence of bifurcations, we never theless suggest hour aspects of the mixed-parity branch may help in un derstanding features of the previous pure-parity branch.