Evaluation of electromotive force in interplanetary space

Abstract. Electromotive force plays a central role in the turbulent dynamo mechanism and carries important information on the nature of the turbulent fields. In this study, an analysis method is developed for the electromotive force and the transport coefficients such as those for the α effect (coefficient α) and the turbulent diffusivity (coefficient β). The method is applied to a magnetic cloud event observed by the Helios 2 spacecraft in the inner heliosphere. The electromotive force is enhanced together with the magnetic cloud event by 1 or 2 orders of magnitude, suggesting that the magnetic field can locally be amplified in the heliosphere, presumably for a short time.