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Are short-term variations in solar oscillation frequencies the signature of a second dynamo?

Auteur

Broomhall Anne-Marie

Institution

University of Birmingham

Theme

Solar diameter, irradiance and activity
Auteur(s) supplémentaire(s)Stephen.T. Fletcher (2), David Salabert (3), Sarbani Basu (4), William J. Chaplin (1), Yvonne Elsworth (1), Rafa A. García (5), Antonio Jimenez (3), and Roger New (2)
Institution(s) supplémentaire(s)(2) Sheffield Hallam University, (3) Instituto de Astrofisica de Canarias, (4) Yale University, (5) Service d'Astrophysique, CEA/Sacaly

Abstract

In addition to the well-known 11-year solar cycle, the Sun’s magnetic activity also shows significant variation on shorter time scales, e.g. between one and two years. We observe a quasi-biennial (2-year) signal in the solar p-mode oscillation frequencies, which are sensitive probes of the solar interior. The signal is visible in Sun-as-a-star data observed by different instruments and here we describe the results obtained using BiSON, GOLF, and VIRGO data. Our results imply that the 2-year signal is susceptible to the influence of the main 11-year solar cycle. However, the source of the signal appears to be separate from that of the 11-year cycle. We speculate as to whether it might be the signature of a second dynamo, located in the region of near-surface rotational shear.
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