@article{PAR00002814,
  title = {{R}apidly rotating spherical {C}ouette flow in a dipolar magnetic field : an experimental study of the mean axisymmetric flow},
  author = {{N}ataf, {H}.{C} and {A}lboussiere, {T}. and {B}rito, {D}. and {C}ardin, {P}. and {G}agni{\`e}re, {N}. and {J}ault, {D}ominique and {S}chmitt, {D}.},
  editor = {},
  language = {{ENG}},
  abstract = {{I}n order to explore the magnetostrophic regime expected for planetary cores, experiments have been conducted in a rotating sphere filled with liquid sodium, with an imposed dipolar magnetic field (the {DTS} setup). {T}he field is produced by a permanent magnet enclosed in an inner sphere, which can rotate at a separate rate, producing a spherical {C}ouette flow. {T}he flow properties are investigated by measuring electric potentials on the outer sphere, the induced magnetic field in the laboratory frame, and velocity profiles inside the liquid sodium using ultrasonic {D}oppler velocimetry. {T}he present article focuses on the time-averaged axisymmetric part of the flow. {T}he {D}oppler profiles show that the angular velocity of the fluid is relatively uniform in most of the fluid shell, but rises near the inner sphere, revealing the presence of a magnetic wind, and gently drops towards the outer sphere. {T}he transition from a magnetostrophic flow near the inner sphere to a geostrophic flow near the outer sphere is controlled by the local {E}lsasser number. {F}or {R}ossby numbers up to order 1, the observed velocity profiles all show a similar shape. {N}umerical simulations in the linear regime are computed, and synthetic velocity profiles are compared with the measured ones. {I}n the geostrophic region, a torque-balance model provides very good predictions. {W}e find that the induced magnetic field varies in a consistent fashion, and displays a peculiar peak in the counter-rotating regime. {T}his happens when the fluid rotation rate is almost equal and opposite to the outer sphere rotation rate. {T}he fluid is then almost at rest in the laboratory frame, and the {P}roudman-{T}aylor constraint vanishes, enabling a strong meridional flow. {W}e suggest that dynamo action might be favored in such a situation.},
  keywords = {{MAGNETISME} ; {ASTROPHYSIQUE} ; {S}pherical {C}ouette flow ; magnetostrophic ; liquid sodium experiment ; dynamo ; ultrasonic {D}oppler velocimetry ; {T}aylor state},
  booktitle = {},
  journal = {{P}hysics of {T}he {E}arth and {P}lanetary {I}nteriors},
  volume = {170},
  numero = {},
  pages = {60--72},
  ISSN = {0031-9201},
  year = {2008},
  DOI = {10.1016/j.pepi.2008.07.034},
  URL = {https://www.documentation.ird.fr/hor/{PAR}00002814},
}