The equipartition frequency v of an anisotropic plasma is calculated numerically and analytically within the Landau approach for strong magnetic fields and several new integral expressions for v are presented. In the ultra strong magnetic field case, when r c <^b, where r c is the Larmor radius and b the classical distance of closest approach, v is shown to be dependent on how the Coulomb force is cut off at short distances. None of the obtained expressions, however, coincides with experiment, in contrast to the strong interaction theory of O'Neil and Hjorth. For weaker, but still strong magnetic fields (r c >b) the ambiguity disappears and the weak interaction result describes well the experiment. It is, hence, the transition region r c ^b, where the transition from strong to weak interaction takes place.