Four stages of <a href="https://en.wikipedia.org/wiki/skin_effect" class="extiw" title="w:skin effect">skin effect</a> in a coax showing the effect of inductance.  Color code: black=overall insulating sheath, tan=conductor, white=dielectric, green=current into the screen, blue=current coming out of the screen, dashed blue lines with arrowheads=magnetic flux (B).  The width of the dashed blue lines is intended to show relative strength of the line integral of the B field.  The four stages A, B, C and D are unenergized, low frequency middle frequency and high frequency respectively. There are three regions that may contain B flux: the center conductor, the dielectric and the outer conductor.  In stage B, current covers the conductors uniformly and there is B flux in all three regions. In stage C, the flux in the dielectric is unchanged from stage B, but some of the cross sections of the center conductor and outer conductor have no current and no flux. There is less energy stored in the field for the same current so the inductance is less.  In stage D the skin effect is fully developed.  The current is confined to the surface of the conductors.  The flux in the dielectric is unchanged from stage B but there is no current and no flux in the conductors.  There is less energy stored for the same current relative to stage C o the inductance less than the inductance of stage C.
<ul><li><a href="//commons.wikimedia.org/wiki/File:Coax_and_Skin_depth.png" title="File:Coax and Skin depth.png">File:Coax and Skin depth.png</a>: <a href="//commons.wikimedia.org/wiki/User:Constant314" title="User:Constant314">Constant314</a></li>
<li>derivative work <a href="//commons.wikimedia.org/wiki/User:Gregors" title="User:Gregors">Gregors</a></li></ul>
<ul><li><a href="//commons.wikimedia.org/wiki/File:Coax_and_Skin_depth.png" title="File:Coax and Skin depth.png">File:Coax and Skin depth.png</a></li></ul>