(Cont.) When the order of the applied magnetic fields is reversed, the DC axial magnetic field is applied first causing the ferrofluid droplet to form the labyrinth instability. The rotating magnetic field is then applied creating a spiral formation. Experiments are conducted for varying Hele-Shaw cell separation gap, and rotating magnetic field amplitude and frequency. Measurements were consistent with our model. A cylindrical vessel is filled with a water-based ferrofluid and excited by a uniform rotating magnetic field that induces a counter-rotating circular flow in the vessel. A DC axial magnetic field is slowly raised to change the curvature of the fluid surface and results in a change in the ferrofluid flow direction to co-rotating with the applied magnetic field. Measurements are taken of the threshold axial magnetic field that results in the change of flow direction for varying rotating magnetic field direction, amplitude, and frequency. An analysis is included that describes the change in flow direction due to surface curvature.

The article is a continuation of previous works in which general equations of magnetohydrodynamics were used for derivation of expressions describing the motion of a conductive fluid in a narrow channel of annular cross section with a rotating magnetic field. This system is numerically integrated in the present paper and results are given showing the distribution of velocity, magnetic field and pressure in the channel as well as indices describing energy transformation as a function of geometric parameters, the magnetic Reynolds number and the Alfven number. (Author).

Solar and space physics is the study of solar system phenomena that occur in the plasma state. Examples include sunspots, the solar wind, planetary magnetospheres, radiation belts, and the aurora. While each is a distinct phenomenon, there are commonalities among them. To help define and systematize these universal aspects of the field of space physics, the National Research Council was asked by NASA's Office of Space Science to provide a scientific assessment and strategy for the study of magnetized plasmas in the solar system. This report presents that assessment. It covers a number of important research goals for solar and space physics. The report is complementary to the NRC report, The Sun to the Earthâ€"and Beyond: A Decadal Research Strategy for Solar and Space Physics, which presents priorities and strategies for future program activities.

Earlier experiments have been repeated to evaluate magnetic fluid behavior in DC, AC and rotating magnetic fields. Understanding these behaviors are essential to the ferrohydrodynamic applications of ferrofluids in biomedicine. Careful measurements in Hele-Shaw cells with simultaneous perpendicular DC and in-plane rotating magnetic fields have shown that ferrofluid drop spiral patterns rotate in the same direction as the rotating magnetic field, independent of the polarity of the perpendicular DC magnetic field. This corrects inconsistencies in previously reported measurements. The large and heavy electromagnet and power supply used in earlier work were also replaced by a small permanent magnet assembly from MagswitchTM to still produce ferrofluid spirals and spontaneous self-assembling ferrofluid dot patterns.

When a conducting fluid moves in a magnetic field, electrical fields are induced in the fluid which in turn result in the flow of electric currents. The interaction of the currents with the magnetic fields results in forces which effect the fluid flow pattern and modifications in the magnetic field distributions. The study of this complicated interaction of moving conducting fluid with the magnetic field is the science of MHD which is described by the electromagnetic field equations of Maxwell along with the equations of the fluid dynamics.