The temperature dependence of the electrical resistance noise in the presence of a magnetic field in polycrystalline YBCO samples was fitted with an average activation energy which decreases with magnetic field and with bias electrical current. 555 Mod. Phys. Lett. B 2001.15:555-559. Downloaded from www.worldscientific.com by MCMASTER UNIVERSITY on 02/18/15. For personal use only.