The measurement on the dielectric properties of ice at HF, VHF and microwave frequencies

The dielectric properties of ice Ih (hexagonal ice) were measured at HF, VHF and microwave frequencies using several methods appropriate for each frequency range. C-axis orientation dependence of the complex permittivity was particularly investigated because the dielectric anisotropy of the media determines the polarization state of the electromagnetic waves propagating in it and because it can cause the radio-echo internal reflections in the polar ice sheets. It was confirmed that the difference between the real part of the permittivity parallel to the c-axis and perpendicular to the c-axis is almost the same at HF and at microwave frequency. In addition, it was confirmed that the anisotropy of the loss tangent was about 20% at -22°C at HF, i.e. at frequencies characterized by the high frequency tail of the Debye relaxation spectrum. This value is well explained mainly by the anisotropy in the dispersion strength and partly by the anisotropy in the relaxation time of Debye dispersion. In addition, these facts suggests this ratio hold over frequencies up to microwave where the absorption of the lattice vibration becomes dominant