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PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
SEQUENCE:0
UID:UW-Physics-Event-3412
DTSTART:20140925T193000Z
DTEND:20140925T210000Z
DTSTAMP:20260419T161936Z
LAST-MODIFIED:20140922T124800Z
LOCATION:4421 Sterling Hall
SUMMARY:Angular Momentum Transport via Internal Gravity Waves in Evolv
 ing Stars\, Astronomy Colloquium\, Jim Fuller\, Caltech
DESCRIPTION:Recent asteroseismic advances have allowed for direct meas
 urements of the internal rotation rates of many sub-giant and red gian
 t stars. Unlike the nearly rigidly rotating Sun\, these evolved stars 
 contain radiative cores that spin much faster than their overlying con
 vective envelopes\, but much slower than they would in the absence of 
 internal angular momentum transport. We investigate the role of intern
 al gravity waves in angular momentum transport in evolving low mass st
 ars. In agreement with previous results\, we find that convectively ex
 cited gravity waves can prevent the development of strong differential
  rotation in the radiative cores of Sun-like stars. As stars evolve in
 to sub-giants\, however\, low frequency gravity waves become strongly 
 attenuated and cannot propagate below the hydrogen burning shell\, all
 owing the spin of the core to decouple from the convective envelope. T
 his decoupling occurs at the base of the sub-giant&lt\;br&gt\;branch w
 hen stars have surface temperatures of roughly 5500K. However\, gravit
 y waves can still spin down the upper radiative region\, implying that
  the observed differential rotation is likely confined to the deep cor
 e near the hydrogen burning shell. The torque on the upper radiative r
 egion may also prevent the core from accreting high-angular momentum m
 aterial and slow the rate of core spin-up. The observed spin-down of c
 ores on the red giant branch cannot be totally attributed to gravity w
 aves\, but the waves may enhance shear within the radiative region and
  thus increase the efficacy of viscous/magnetic torques.
URL:https://www.physics.wisc.edu/events/?id=3412
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