The ground magnetic signature of a three-dimensional ionospheric current system with multiple field-aligned current sheets is calculated under the assumption of uniform ionospheric conductance. Such a current system and the accompanying spiky electric fields are consistent with the model of flux transfer events proposed by Kan (1988). The magnetic signature of the proposed flux transfer event current system is dominated by the H component with a distribution pattern highly localized under the multiple current sheets. The Z component is weaker and less confined. If the upward current density is significantly greater than the downward current density in each pair of flux transfer event field-aligned current sheets, the negative Z component perturbation spreads over a much wider area than the positive Z component. If the magnitudes of the current density are reversed, the opposite is true. The D component is 30 nT or less which is probably too small to be detectable. ¿ American Geophysical Union 1989