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SUMMARY:Invited speaker: Observations of solar oscillations in the inertia
 l frequency range - Laurent Gizon (Max Planck Institute for Solar System R
 esearch)
DTSTART:20221129T090000Z
DTEND:20221129T094500Z
UID:TALK192080@talks.cam.ac.uk
DESCRIPTION:The oscillations of a slowly rotating star have long been clas
 sified into spheroidal and toroidal modes. The spheroidal modes include th
 e well-known five-min acoustic modes used in helioseismology. In this pres
 entation we report observations of the Sun&rsquo\;s toroidal modes\, for w
 hich the restoring force is the Coriolis force and whose periods are on th
 e order of the solar rotation period. By comparing the observations with t
 he normal modes of a differentially rotating spherical shell\, we are able
  to identify many of the observed modes. These include high-latitude modes
 \, critical-latitude modes\, and the equatorial Rossby modes. In the model
 \, the high-latitude modes are baroclinically unstable due to the latitudi
 nal entropy gradient. The frequencies of the modes and their surface eigen
 functions inform us about important properties of the deep convection zone
 \, such as the superadiabaticity and the turbulent viscosity. The interpre
 tation of the mode amplitudes requires some care and detailed modeling\, i
 n particular because the mode spectrum is dense and the mode amplitudes ar
 e observed to be sensitive to the solar-cycle magnetic field.\n&nbsp\;\n&n
 bsp\;\n&nbsp\;
LOCATION:Seminar Room 1\, Newton Institute
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