E.E. Khizhnyak, E.P. Khizhnyak, O.V. Betsky, Yu.g. Yaremenko, A.S. Kozmin

Heating is considered as one of the main non-controversial primary mechanisms of biological effects of millimeter wave radiation, and water is the primary target responsible for the absorption of microwave energy. Temperature gradients which occur due to rapid absorption of millimeter waves become sufficient to create convective stream-ing in water-containing media. The temperature gradient which corresponds to the threshold of free convection (1 ºC per 6.7 km) can be exceeded after a few seconds of millimeter wave exposure at incident power densities of 106 W/cm2. It is quite difficult to observe micro-convection streams in pure water at such low levels of microwave exposure, but it-s much easier to record such types of convection in ethanol-water solutions because temperature gradients disturb the concentration equilibrium of ethanol-water solutions. Experimental studies of micro-convection processes in thin interfacial layers of 10% ethanol-water solutions ex-posed to non-thermal intensity millimeter wave radiation were performed using the method of high resolution real-time infrared thermography. Modification of micro-convection patterns was observed at 106 W/cm2 levels of mm-wave exposure together with 0.2-0.3 ºC temperature fluctuations caused by ethanol concentration gradients leading to an exothermal reaction due to ethanol diffusion in water. Under such conditions millimeter waves play the role of a trigger factor that determines the localization of the ris-ing convective stream.