Joint probability density with radial, tangential, and perturbative forces

We derive the Fokker-Planck equation for an active particle with both radial and tangential force and perturbative force, and its approximate solution of joint probability density is obtained. In t>>u and u=0 regions, an active particle leads to a super-diffusive distribution for radial velocity, while the mean squared tangential velocity with both radial and tangential force and perturbative force behaviors the Gaussian diffusion. As a result, the joint probability density obtained may be similarly consistent with that for the self-propelled particle.