scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

STP12 Abstracts
Berlin, 12 - 16 July 2010
SCOSTEP Symposium 2010
A theoretical model of torsional oscillations from a flux transport dynamo model
Chatterjee Piyali 1 , Chakraborty Sagar 2 , Rai Choudhuri Arnab 3
1 NORDITA, Stockholm, 2 Niels Bohr Institute, Copenhagen, 3 Indian Institue of Science, Bangalore
Torsional oscillations, which appear as fast and slow rotating bands on the solar surface,
provide observational evidence for the back reaction of the magnetic cycle on the solar flows.
However, the faster rotating band is observed at the solar surface 2-3 years before the first
sunspots of the upcoming cycle appear on the solar surface. We conjecture that this apparent
violation of causality can be resolved if the Lorentz stress is initiated at the high latitude
tachocline due to production of strong toroidal fields there and are propagated upwards due to
Alfven waves. We present below results from a mean field model coupled with an equation
for the azimuthal velocity to support our claim. The reader is also requested to look at
Chakraborty, Choudhuri and Chatterjee (2009, PRL, 102, 041102 and PRL, 103, .099902),
where this work was originally published.