@article{PAR00009444,
  title = {{O}n the reflection of {A}lfven waves and its implication for {E}arth's core modelling},
  author = {{S}chaeffer, {N}. and {J}ault, {D}. and {C}ardin, {P}hilippe and {D}rouard, {M}.},
  editor = {},
  language = {{ENG}},
  abstract = {{A}lfven waves propagate in electrically conducting fluids in the presence of a magnetic field. {T}heir reflection properties depend on the ratio between the kinematic viscosity and the magnetic diffusivity of the fluid, also known as the magnetic {P}randtl number {P}m. {I}n the special case, {P}m = 1, there is no reflection on an insulating, no-slip boundary, and the incoming wave energy is entirely dissipated in the boundary layer. {W}e investigate the consequences of this remarkable behaviour for the numerical modelling of torsional {A}lfven waves (also known as torsional oscillations), which represent a special class of {A}lfven waves, in rapidly rotating spherical shells. {T}hey consist of geostrophic motions and are thought to exist in the fluid cores of planets with internal magnetic field. {I}n the geophysical limit {P}m << 1, these waves are reflected at the core equator, but they are entirely absorbed for {P}m = 1. {O}ur numerical calculations show that the reflection coefficient at the equator of these waves remains below 0.2 for {P}m = 0.3, which is the range of values for which geodynamo numerical models operate. {A}s a result, geodynamo models with no-slip boundary conditions cannot exhibit torsional oscillation normal modes.},
  keywords = {{N}umerical solutions ; {D}ynamo: theories and simulations ; {R}apid time ; variations ; {C}ore ; outer-core and inner-core ; {P}lanetary interiors},
  booktitle = {},
  journal = {{G}eophysical {J}ournal {I}nternational},
  volume = {191},
  numero = {2},
  pages = {508--516},
  ISSN = {0956-540{X}},
  year = {2012},
  DOI = {10.1111/j.1365-246{X}.2012.05611.x},
  URL = {https://www.documentation.ird.fr/hor/{PAR}00009444},
}