Using a kinetic-theoretic approach to Fokker-Planck equilibrium of thermonuclear ␣ particles in dense and magnetized plasmas, the corresponding longitudinal dielectric function is investigated at length. It is used to evaluate the energy loss of the ␣ s Ј through the excitation of collective plasma modes. Specific attention was paid to the case of extreme magnetization, as well as to the parallel stopping of ␣ particles in dense and hot plasmas of magnetized target fusion ͑MTF͒ interest. Maximum stopping is shown to be strongly dependent on magnetic field intensity.