The following work has been done at the Department of Earth and Planetary Sciences, Johns Hopkins University, in collaboration with Professor Peter Olson.

The experimental apparatus used for thermal convection studies in a rapidly rotating hemispherical shell. The outer copper hemisphere has a diameter of 30 cm, and the inner sphere has a diameter of 10 cm. The upper lid of the hemisphere is made from plexiglass. The black cylinders attached to the lid are thermistor probes that are wired to the slip ring at the bottom. A dye (green fluid) is injected from the stationary frame into the fluid through the dye port. The hemisphere is spun at 200-400 rpms. Water (Pr = 7) is used as the working fluid.

The experimental setup. The rotating hemisphere is at the center. The PC records the temperature measurements. The video recording is made through the rotoscope.

Planforms of rotating hemispherical shell convection at Ek = 4.7 x 10^-6,@under a thermally homogeneous outer boundary. Rotation is counter clockwise. These images were taken by flash photography.

A: Flow pattern under a stably stratified regime at Ra/Rac = -12.6.Dye was injected into the fluid at the point shown by the white arrow.The interleaving lenses of dye indicate the pattern of azimuthal flow.

B: Spiralling columnar convective pattern visualized by Kalliroscope flakes at Ra/Rac = 5.9 (penetrative convection).

C: Turbulent convective pattern visualized by flakes at Ra/Rac = 16.6.

D: Turbulent convection visualized by dye at Ra/Rac = 19.3 The dye is denser than the working fluid and spreads along the equatorial CMB, visualizing the fine-scaled warm plumes originating from the CMB. he warm plumes have a retrograde tilt and a wave number of about 3 per longitude of 10 degrees.

Equatorial planform of rotating hemispherial shell convection with anomalous heat flux at the core-mantle boundary (outer sphere). Rotation is couter clockwise. The heater is indicated by a white rectangle. Ekman number = 4.7 x 10^-6. Ra/Rac = 24. The peak CMB heat flux is 95 times its mean. The convective pattern is visualized by Kalliroscope flakes. The spiralling stationary front originates from the CMB at 50 degrees east of the heater.

Flow under a thermally heterogeneous outer boundary imaged by a fluorescent dye.Ra/Rac = 26. The peak heat flux is 69 times its mean. A white dye was injected adjacent to he heater. White arrows indicate the induced flows (eastward flow (broad arrow) and a narrow jet along the front (fine arrows)). The velocities of the eastward flow and the jet are about 1.5 mm/s and 5.2 mm/s, respectively.

An oblique view of the stationary front visualized by fluorescent dye, for the case shown above. White arrows indicate the trajectory of the 2-D jet flowing from the CMB to ICB. The grey arrow indicates the dye curtain. Rotation is left to right in this view.