Helioseismic Measurement of Solar Torsional Oscillations
S. V. Vorontsov,12
J. Christensen-Dalsgaard,3
J. Schou,4
V. N. Strakhov,2
M. J. Thompson5*
Bands of slower and faster rotation, the so-called torsional
oscillations, are observed at the Sun's surface to migrate in latitude
over the 11-year solar cycle. Here, we report on the temporal
variations of the Sun's internal rotation from solar p-mode
frequencies obtained over nearly 6 years by the Michelson Doppler
Imager (MDI) instrument on board the Solar and Heliospheric Observatory
(SOHO) satellite. The entire solar convective envelope appears to be
involved in the torsional oscillations, with phase propagating poleward
and equatorward from midlatitudes at all depths throughout the
convective envelope.
1 Astronomy Unit, Queen Mary, University of
London, Mile End Road, London E1 4NS, UK.
2 Institute of Physics of the Earth, B. Gruzinskaya
10, Moscow 123810, Russia.
3 Teoretisk Astrofysik
Center, Danmarks Grundforskningsfond, and Institut for Fysik og
Astronomi, Aarhus Universitet, DK-8000 Aarhus C, Denmark.
4 HEPL Annex A201, Stanford University, Stanford, CA
94305-4085, USA.
5 Space and Atmospheric Physics
Group, The Blackett Laboratory, Imperial College of Science, Technology
and Medicine, London SW7 2BZ, UK.
*
To whom correspondence should be addressed. E-mail:
michael.thompson{at}ic.ac.uk
