Binary period variation in HR 1099 calculated for a surface magnetic field of 1 kG, a cycle length of P_act = 2 P_mod, no phase shift, and varying fluctuation parameters A_V, A_B, and A_P. In a conservative scenario with A_P = A_V = A_B = 0.1, the calculated binary period modulation amplitude is two orders of magnitude below the observed values (∼10⁻⁴). Increasing the velocity field fluctuation amplitude to A_V = 0.3 at constant power dissipation A_P = 0.1 only results in a slight increase of ΔP/P. Even for the rather extreme case of A_P = A_V = A_B = 0.5, the produced period variations disagree with observations (see Frasca & Lanza 2005).