Charged Brown Particle: The More Retardation is - the Lower is the   Effective Temperature
  The Brownian motion of a charged particle with finite size (described by Sommerfeld model) is considered. It is found out that due to radiation reaction: (1) the effective temperature of such particle is lower, and (2) the acceleration of the average velocity is smaller, than that for classical Brown particle without electric charge. 
Alexander A.Vlasov