Onset of Normal Field Instability in a Ferrofluid in Microgravity

Abstract

A ferrofluid is a magnetic liquid composed of nanoscale ferrous particles sus- pended in a low-viscosity carrier fluid. When subjected to a magnetic field, the surface of a ferrofluid deforms into peaks and valleys along the magnetic field lines. The onset of surface deformation is called the Normal Field Instability, and the theory describing the NFI identifies a critical magnetic field below which no magnetically driven surface deformations occur. This critical field depends on the gravitational acceleration and, according to the theory, should disappear as local gravitational acceleration approaches zero. Previous studies have been inconclusive on the existence of a critical magnetic field in reduced gravity. For our work, we designed a payload for a suborbital rocket mission which launched through the RockSat-C program. Our experiment incorporated a ferrofluid sam- ple and a uniform magnetic field which could be varied across a discrete range of value. During the microgravity portion of the rocket’s flight, we obtained video of the ferrofluid’s behavior to compare it to data taken in Earth’s gravity.