Alternating current in flux tubes is one of the possible contributors to the heating of the solar corona. The mechanism of the generation of alternating currents in flux tubes by turbulent pressure fluctuations in convective zone is proposed. The thin-flux-tube approximation shows, that the linear and weakly nonlinear torsional waves in twisted flux tube, are accompanied by tube cross section fluctuations. Consequently, external pressure fluctuations generate not only slow MHD waves but torsional waves as well. The torsional waves are nothing else than alternating current. ©2000 American Institute of Physics.