This paper considers the analytical solution to the problem of low-frequency induction, by quasi-uniform electric fields, in an equatorially stratified sphere having the particular conductivity distribution &sgr;(&phgr;)=&sgr;0e-&lgr; cos(p&phgr;), where p∈{1,2} is a periodicity factor, &sgr;0 is a conductivity amplitude factor, and &lgr;>0 is a dimensionless conductivity contrast parameter. This distribution has p conductivity maxima and minima as a function of equatorial angle. The resulting induced electric and current density fields are fully three-dimensional and exhibit interesting, yet physically reasonable, behavior. Most noticeable are the deviations from the straight current paths that would be present in the absence of any conductivity gradient. This solution for electric excitation is supplementary to ones previously published for the quasi-static magnetic excitation and so completes the solution for induction in the sphere by quasi-uniform electromagnetic sources. The nature of the solution is illustrated for the case of both singly and doubly periodic conductivity distributions, for the three canonical source directions. ¿ 1998 American Geophysical Union |