Flight Reflex Induced by an Electromagnetic Beam Moving Relative to the Test Subject

This study is motivated by the need to better understand and predict the conditions under which electromagnetic exposure induces a flight response in biological subjects, which is important for assessing safety thresholds and guiding the design of exposure tests. The aim of this work is to investigate the occurrence of the flight reflex when a subject is exposed to an electromagnetic beam moving relative to the body. A heat-induced flight model is developed based on the physical processes of beam energy absorption, heat diffusion across the skin, activation of thermal nociceptors, and the initiation of a flight response once the activated skin volume reaches a critical threshold. In the present mathematical model, the governing system is reduced to a normalized formulation in which the temperature field reaches a steady state in a coordinate system moving with the beam. A key parameter in the heating process is the active heating duration of the beam defined as the time it takes for the moving beam to traverse one beam radius. Within this framework, the occurrence of flight is analyzed in the two-dimensional space of physical beam radius and power density at various values of beam active heating duration, which contains the effect of beam moving velocity. An accurate empirical formula along with a simple scaling law is derived to characterize the boundary of the flight-inducing region. The results show that the scaling law reliably predicts the effects of varying beam radius and velocity, even without detailed model parameters. This provides a practical tool for forecasting flight-inducing exposure conditions and supports safety assessment and system design for moving electromagnetic sources.