At high data rates a transition from thermo-activated to gyro-magnetic magnetic switching occurs. The switching is then driven mainly by the head field and thermal effects are usually ignored. In this study, it is shown that when the field from a recording head does not change polarity and no transition is written, the switching of the magnetization for current recording media occurs by thermal activation. The magnetic response of individual grains during the motion through the field profile of the recording head is determined by integration of the Langevin equation of the system using the Heun numerical scheme. The authors show that the thermal reduction of the switching field exhibits a logarithmic variation with medium velocity v, characteristic of a thermo-activated process, when v<v1, the thermal reduction of the switching field is independent of the medium velocity but linearly dependent on temperature and is attributed to random variations in the realization of the gyro-magnetic switching process. For v>v1, the gym-magnetic precession modifies the energy barrier to the switching process. The barrier can be determined from the gradient of In(psw) vs 1/T plots. Comparison with the barrier determined in the quasi-static limit of vanishing velocity, shows that gyro-magnetic precession results in an enhancement of the barrier. The dependence of the effective barrier on the head-to-medium relative velocity is also studied.