Electrical Relaxation in Saline Ice

The experimentally observed frequency dispersions of the complex dielectric coefficient for some samples of artificial saline ice (of a type similar to natural sea ice) are examined with a view to identifying major contributing mechanisms. The simultaneous integral equations describing the linear superposition of relaxation processes having a continuum of relaxation times were inverted numerically to yield histogram representations of the relaxation time distribution function between 10−9 and 10−1 sec. These functions exhibited three main features: (1) an abrupt peak near 10−9 sec, responsible in part for the high frequency dispersion (above 1 MHz), and which is attributed to polarization of the elongated conductive brine cells within the ice (Maxwell-Wagner-Sillars dispersion); (2) a hump between 10−6 and 10−4 sec which shifts towards shorter relaxation times at higher temperatures, showing an activation energy similar to that of protons in pure ice—this mechanism is seen at midfrequencies (1 KHz-1 MHz); and (3) a wide mass at longer relaxation times commencing between 10−4 and 10−3 sec which is probably associated with space-charge polarization arising from movement of the ions within continuous brine channels reaching from one electrode to the other.