The VLF complex permittivity of deep Antarctic ice measured in situ

Abstract

The results of the first in‐situ measurement at VLF of the complex permittivities of deep Antarctic ice are presented as functions of depth, projected along the vertical. Measurements made with an electrically short dipole probe at five frequencies to a depth of 1500 m below the ice surface are reported. Temperature is identified as a dominant factor affecting the ice permittivity. This fact, coupled with the measurements of complex permittivity to 1500 m depth, is used to estimate ice permittivities from 1500 m to the bottom of the ice sheet at 2164 m. Comparison of the in‐situ measurements with those of surface measurements is made; it is concluded that for the purpose of VLF antenna and propagation studies the Antarctic ice sheet cannot be considered to be an isotropic homogeneous material, but must be treated at least as a horizontally stratified medium whose dielectric and loss properties vary in the vertical direction with temperature.