EarthRef.org Reference Database (ERR) -- Claßen et al. 1999

The onset and structure of compositional convection in a rotating system are investigated experimentally. A vertically oriented cylindrical annulus filled with NH4Cl--H2O solution is cooled from the bottom and can be rotated about its axis at rates ranging up to 10.5 rad s-1, corresponding to Ekman numbers down to 7.5¿10-6. The Coriolis force has a strong effect on the structure of plumes above the mush-liquid interface. Helical motion of the conduit, which is weakly developed in the non-rotating case, is amplified by Coriolis forces that twist the plume conduits to lie nearly horizontally. This results in secondary plumes (or blobs) that rise from the sub-horizontal primary plume conduits. This new instability could be an efficient mechanism for producing small-scale flow in the form of buoyant blobs that ascend through the polar regions of the outer core. ¿ 1999 American Geophysical Union The onset and structure of compositional convection in a rotating system are investigated experimentally. A vertically oriented cylindrical annulus filled with NH4Cl--H2O solution is cooled from the bottom and can be rotated about its axis at rates ranging up to 10.5 rad s-1, corresponding to Ekman numbers down to 7.5¿10-6. The Coriolis force has a strong effect on the structure of plumes above the mush-liquid interface. Helical motion of the conduit, which is weakly developed in the non-rotating case, is amplified by Coriolis forces that twist the plume conduits to lie nearly horizontally. This results in secondary plumes (or blobs) that rise from the sub-horizontal primary plume conduits. This new instability could be an efficient mechanism for producing small-scale flow in the form of buoyant blobs that ascend through the polar regions of the outer core. ¿ 1999 American Geophysical Union