Definitions for "Skin depth"
Measure of the effective depth of penetration of electromagnetic fields. It is defined as the depth at which the amplitude of an electromagnetic field drops to 37% of its surface value.
In a current-carrying conductor, the depth below the surface at which the current density has decreased one level below the current density at the surface; that is, the field has decreased to 1/e (36.8%) of its surface value, also called depth penetration.
A measure of the depth of penetration of an electromagnetic field into a material. It is defined as the depth at which the primary field decreases to 1/e of the field at the surface. It is calculated by approximately 503 x (resistivity/frequency ). Note that depth of penetration is greater at higher resistivity and/or lower frequency.