Magnetic Liquid Patterns in Space and Time

Abstract

Macroscopic surface patterns of magnetic fluids are experimentally investigated for four different configurations of the liquid layer, and the orientation, homogeneity and temporal evolution of the magnetic field. Firstly the formation of surface undulations after a pulse-like application of the magnetic induction is examined. The wavenumbers measured for different magnetic induction are compared with the wavenumber of maximal growth predicted by linear stability analysis for the Rosensweig instability. Secondly, the formation of twin-peak patterns at the magnetic Faraday instability in an annular trough is reported. Thirdly, a ring of magnetic liquid spikes in a gradient magnetic field is periodically excited by an alternating magnetic field. The transition to spatio-temporal intermittency found in this way is characterized by power laws and their critical exponents. Eventually, we record the pinch-off of a magnetic liquid bridge by a high-speed camera. The temporal evolution of the neck radius is compared with results obtained theoretically via universal scaling functions.