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SUMMARY:Zonostrophic turbulence on gas giants: insights on turbulent trans
 port and mixing from laboratory experiments - Daphné Lemasquerier (Univer
 sity of St Andrews)
DTSTART:20240521T130000Z
DTEND:20240521T140000Z
UID:TALK215761@talks.cam.ac.uk
DESCRIPTION:The colourful bands of Jupiter are sustained by intense east-w
 est winds called zonal jets\, which extend well below Jupiter's weather la
 yer into its mantle of liquid hydrogen. These jets constitute a fascinatin
 g natural example of how a rapidly-rotating turbulent flow self-organises 
 at large scale. Despite decades of observations and modelling\, understand
 ing the long-term\, nonlinear equilibration of zonal jets and the feedback
  with the underlying turbulence is still a challenge\, notably because of 
 the extreme "zonostrophic" regime of turbulence on gas giants.&nbsp\;\nIn 
 this talk\, I will discuss the challenges that arise to study such extreme
  regime\, and describe insights from recent laboratory experiments built i
 n Marseille where instantaneous turbulent zonal jets spontaneously emerge 
 from the small-scale forcing\, equilibrate at large scale\, and can contai
 n up to 70% of the total kinetic energy of the flow once in a quasi-steady
  state. I will show that the spectral properties of the experimental flows
  are consistent with the theoretical predictions in the zonostrophic turbu
 lence regime. This constitutes the first fully-experimental validation of 
 the zonostrophic theory in a completely three-dimensional framework. &nbsp
 \;Next\, I will quantify the local potential vorticity mixing by measuring
  the equivalent of a Thorpe scale\, and confirm that it can be used to est
 imate the upscale energy transfer rate of the flow\, which otherwise needs
  to be estimated from a much more demanding spectral analysis. Finally\, I
  will analyse Lagrangian trajectories to discuss the turbulent transport p
 roperties in terms of effective diffusivity and investigate the effect of 
 the zonal flow on the isotropy and homogeneity of the turbulent transport.
  Our estimates of meridional diffusivities are consistent with predictions
  from mixing length and zonostrophic theories\, and confirm the so-called 
 suppression effect of zonal flows on eddy-diffusivity\, which may hence be
  important to take into account in models parametrizing small-scale proces
 ses. These results are cross-validated by complementary 2D quasi-geostroph
 ic numerical simulations.\nContributors - Benjamin Favier (IRPHE\, CNRS)\,
  Michael Le Bars (IRPHE\, CNRS)\, Simon Cabanes (IPGP)\, Jonathan Aurnou (
 UCLA)
LOCATION:Seminar Room 1\, Newton Institute
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