SIGN SINGULARITY IN THE SECULAR ACCELERATION OF THE GEOMAGNETIC-FIELD

We investigate the occurrence of sign singularity in the geomagnetic f ield secular acceleration. The results on the cancellation index kappa are compared with the results relative to experimental data from ordi nary fluid and MHD turbulence, showing that a turbulent inhomogeneous cascading process occurs. The relevance of our results is pointed out and discussed in the context of fluid motions, acting within the Earth 's fluid metallic core, showing that the secular acceleration is evide nce of the turbulent nature and the intermittent character of the flui d core motions. [S0031-9007(98)07784-9].