Leakage Inductance Coaxial Cable
This is the graph showing the magnetic field induced from current flowing on the outside of a hollow cylinder (coax):

Source: http://www.ittc.ku.edu/~jstiles/220/handouts/Example%20A%20Hollow%20Tube%20of%20Current.pdf

It also happens current flowing on the outside of coax also has the same behavior as a wire. All wires have inductance. It comes from the magnetic field inhibiting the flow of current. Current flowing through a wire transfers energy to "create" the magnetic field around the wire (or outer conductor of coax), just like wire does in a coil.

If you have current flowing on the outside of the coax, this should be modeled as inductance in a simulator.