Journal Article

Periodicities in the coronal rotation and sunspot numbers

Satish Chandra and Hari Om Vats

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 414, issue 4, pages 3158-3165
Published in print July 2011 | ISSN: 0035-8711
Published online July 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.18611.x
Periodicities in the coronal rotation and sunspot numbers

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This study is an attempt to investigate the long-term variations in coronal rotation by analysing the time-series of the solar radio emission data at 2.8 GHz frequency for the period 1947–2009. Here, daily adjusted radio flux (known as Penticton flux) data are used. The autocorrelation analysis shows that the rotation period varies between 19.0–29.5 sidereal days (mean sidereal rotation period is 24.3 d). This variation in the coronal rotation period shows evidence of two components in the variation: (1) 22-yr component which may be related to the solar magnetic field reversal cycle or Hale's cycle; and (2) a component which is irregular in nature, but dominates over the other components. The cross-correlation analysis between the annual average sunspot number and the coronal rotation period also shows evidence of its correlation with 22-yr Hale's cycle. The 22-yr component is found to be almost in phase with the corresponding periodicities in the variation of the sunspot number.

Keywords: Sun: corona; Sun: radio radiation; Sun: rotation

Journal Article.  5742 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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