"Helicities, defined by the volume integral of the inner product of a vector field and its curl, are known to play essential roles in numerous geo/astrophysical and space plasma science phenomena, including stellar and planetary dynamos and evolution, mass condensation in star forming regions, accretion jet formation near compact massive objects, amplification of large-scale magnetic fields in the Universe, magnetic confinement in fusion and laboratory plasmas, etc. Acknowledging these important roles in various research fields, helicities have been studied from many different angles and viewpoints."-- Provided by publisher.