Temporal variations in the Sun's rotational kinetic energy

¹ Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005, India e-mail: antia@tifr.res.in
² Centre for Basic Sciences, University of Mumbai, Mumbai 400098, India, and Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
³ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, and Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, Wilberfore Road, Cambridge CB3 0WA, UK

Received: 3 July 2007
Accepted: 31 October 2007

Abstract

Aims. We study the variation of the angular momentum and the rotational kinetic energy of the Sun, and associated variations in the gravitational multipole moments, on a timescale of the solar cycle.

Methods.These quantities are determined by inverting helioseismic rotational splitting data obtained by the Global Oscillation Network Group and by the Michelson Doppler Imager on the Solar and Heliospheric Observatory.

Results.The temporal variation in angular momentum and kinetic energy at high latitudes (>) through the convection zone is positively correlated with the level of solar activity, whereas at low latitudes it is anticorrelated, except in the top 10% by radius where both are correlated positively.

Conclusions.The helioseismic data imply significant temporal variation in the angular momentum and the rotational kinetic energy, and in the gravitational multipole moments. The properties of that variation will help constrain dynamical theories of the solar cycle.