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Video abstract for the article 'Orbital Josephson effect and interactions in driven atom condensates on a ring ' by M Heimsoth, C E Creffield, L D Carr and F Sols (M Heimsoth et al 2012 New J. Phys. 14 075023). Read the full article in New Journal of Physics at http://iopscience.iop.org/1367-2630/14/7/075023/article. Part of Focus on Bose Condensation Phenomena in Atomic and Solid State Physics. GENERAL SCIENTIFIC SUMMARY Introduction and background. Bosonic Josephson junctions represent a minimal case of a quantum many-body system. for this reason, they have become popular for studying collective quantum phenomena, such as macroscopic quantum self-trapping and many-body entanglement, for both experimental and theoretical considerations. Josephson junctions in Bose--Einstein condensates (BECs) are characterized by a few macroscopically occupied single-particle modes, among which the atoms can move coherently. Importantly, in these systems the dynamics and statistics are such that, effectively, two particles only interact with each other when they are found in the same mode. So far, two examples of the Josephson effect in BECs are known. These are conventionally referred to as the internal and external Josephson effect. Main results. In this paper, we present a qualitatively new form of Josephson link in BECs and name it the 'orbital Josephson effect', because it connects single-particle modes each characterized by a specific orbital state. The participating modes are three rotational modes of a BEC in a ring trap (see the figure). We observe that many-body effects become relevant for those dynamical regimes where a mean-field prediction shows chaos. Wider implications. A novel manifestation of Josephson physics in BECs extends the possibilities of experimentalists to realize its versatile dynamics. Furthermore, this work helps in the understanding of the tricky role of particle interactions for quantum many-body systems out of equilibrium, because the basic parts of our derivations can be directly translated to the case of fermionic or mixed systems, as well as to other trap-geometries.