Figure 4.

The magnetic field resulting from eddy currents can be modeled using a linear system. Rapidly decaying eddy currents are assumed to behave as a single current loop from immediately neighboring areas. The time derivative of the coil current is the input function and a monoexponential $A\cdot e^{-b\cdot t}$, which represents current decay in a single loop, is the impulse response function. After optimizing A and b, the predicted output closely follows the time course for B_E when σ_p= 1 S/m. The half-life of the mono exponential is $\text{τ}=\frac{\ln \left(2\right)}{\text{b}}=2\hspace{0.17em}\text{ns}$. The fit is less acceptable as conductivity rises and is not reasonable for σ_p= 1000 S/m.