We derive the guiding center equations of motion from the phase space Euler-Lagrange formulation, which describe the motion of a charged particle in a toroidal magnetic equilibrium in the presence of the electrostatic fluctuations of the drift wave type turbulence. The guiding center equations are numerically solved including the Coulomb collisional pitch angle scattering. Without electrostatic potential, φ, we measure the microscopic diffusion coefficient, D, for different values of collisionality $ν_*$. The results agree well with the neoclassical calculations. The diffusion coefficient is also measured in the presence of a model spectrum of electrostatic drift wave fluctuations, $\tilde{φ}$ (γ, θ, φ), and the external potential, $φ_0(γ)$. In general the diffusion coefficient increases with increasing fluctuation amplitude while the equilibrium potential diminishes the diffusion processes.
