# Solar Interior Rotation and its Variation

**Rachel Howe
**

National Solar Observatory,

950 N. Cherry Ave.,

Tucson AZ 85719, U.S.A.

http://www.noao.edu/staff/rhowe/

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Abstract

This article surveys the development of observational understanding of the interior rotation
of the Sun and its temporal variation over approximately forty years, starting with the 1960s
attempts to determine the solar core rotation from oblateness and proceeding through the
development of helioseismology to the detailed modern picture of the internal rotation deduced
from continuous helioseismic observations during solar cycle 23. After introducing some basic
helioseismic concepts, it covers, in turn, the rotation of the core and radiative interior, the
“tachocline” shear layer at the base of the convection zone, the differential rotation in the
convection zone, the near-surface shear, the pattern of migrating zonal flows known as the
torsional oscillation, and the possible temporal variations at the bottom of the convection zone.
For each area, the article also briefly explores the relationship between observations and models.