Bill,
I think you are looking for "boundary conditions" as related to discharge of end insulators on antennas, or self supported elements, for that matter. Much has to do with the dielectric and breakdown voltage of the surrounding air.
The subject is mentioned in the Antenna Handbook but does not go into formulas.
But here is a paper on the general subject that has theory and formulas. Pull out some of the phrases related to "boundary" and do a Google further.
http://prst-ab.aps.org/onecol/PRSTAB/v8/i5/e05040173,
T