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SUMMARY:Internally-driven inertial waves in geodynamo simulations - Avishe
 k Ranjan (Engineering)
DTSTART:20170307T130000Z
DTEND:20170307T140000Z
UID:TALK70342@talks.cam.ac.uk
CONTACT:Robert Teed
DESCRIPTION:Inertial waves are oscillations in a rotating fluid\, such as 
 the Earth's outer core\, which result from the restoring action of the Cor
 iolis force and conservation of angular momentum. Particularly important a
 re the low-frequency inertial waves that are known to create Taylor column
 s above a moving body in a rotating tank. They also create columnar flow s
 tructures above/below a localized layer of buoyancy.\n\nWe report\, for th
 e first time\, internally-driven inertial waves triggered by buoyant anoma
 lies near the equator in a strongly-forced geodynamo simulation at Ra/Ra_c
 =42 and E=3x10^{-5}. Using the vertical acceleration as a diagnostic for w
 ave-fronts\, we find that a horizontal movement of buoyant anomalies near 
 the equator is well-correlated with a corresponding movement far from the 
 equator. Moreover\, we find that the slopes observed in the time-series of
  vertical acceleration match closely with those expected from the group sp
 eed of low-frequency inertial waves. The azimuthally-averaged spectrum of 
 vertical acceleration lies in the inertial wave frequency range. Our resul
 ts suggest that the columnar flow in the rotation-dominated core\, an impo
 rtant ingredient for the maintenance of a dipolar magnetic field\, is main
 tained on a fast-time scale by internally-driven inertial waves\, and not 
 by boundary-driven Busse rolls as previously thought. The dynamical role o
 f inertial waves\, particularly with regards to their helicity segregation
  characteristic\, is under investigation.
LOCATION:MR14\,  Centre for Mathematical Sciences\, Wilberforce Road\, Cam
 bridge
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