Abstract
The role of external forces in systems exhibiting anomalous diffusion is discussed on the basis of the describing Langevin equations. Since there exist different possibilities to include the effect of an external field, the concept of biasing and decoupled external fields is introduced. Complementary to the recently established Langevin equations for anomalous diffusion in a time-dependent external force field (Magdziarz M. et al., Phys. Rev. Lett., 101 (2008) 210601), the Langevin formulation of anomalous diffusion in a decoupled time-dependent force field is derived.