DYNAMO III

Dynamo III

Of the four dynamo experiments, Dynamo III most closely models a flow one might find in Earth's outer core. The apparatus marks our return to rotating convection experiments. It is 60 cm in diameter and may rotate up to 100 rev/sec (this puts us in a somewhat frightening, but unexplored region of parameter space: Ra = 10^11, E = 10^-8). The sodium is contained between two corotating concentric spheres. The outside of the sphere is heated with quartz-tungsten IR bulbs, and hexane is pumped up through the central shaft to cool the inner sphere. The temperature difference, along with the rotation, drives convection in the sodium.

We will measure heat flux through both the inner and outer sphere. Temperature and Magnetic field will also be measured in the rotating frame. All the data taken on the rotating frame will be transmitted to the lab frame via a microprocessor controlled IR link (like a remote control).

The following photos were taken recently (12-18-02) while collecting convection data with water instead of sodium. With water we are able to reach Ra = 10^14. The photo on the left was taken through a window in the outer containment vessel. The photo on the right is a rear view of the heater array.

As in Dynamo II, we will diagnose how close we are to self-generation by applying external magnetic pulses (100 G) to the sodium and measuring the rate at which the pulse decays. The slower the decay, the closer we are to a dynamo. We will study the system in the presence of large fields as has been done with Dynamo II.