Asteroseismology and magnetic cycles

• Type: Article in International Scientific Journal
• Date: 2012

Authors

Santos, ARG (Author) Other; Cunha, MS (Author) FCUP; Lima, JJG (Author) FCUP

Journal

Title: Astronomische Nachrichten

Vol. 333

Pages: 1032-1035

ISSN: 0004-6337

Publisher: Wiley-Blackwell

Indexing

ISI Web of Knowledge - 3 Citations

Scopus - 3 Citations

Scientific classification

FOS: Natural sciences > Physical sciences

Other information

Authenticus ID: P-002-2PX

DOI: 10.1002/asna.201211821

Abstract (EN): Small cyclic variations in the frequencies of acoustic modes are expected to be a common phenomenon in solar-like pulsators, as a result of stellar magnetic activity cycles. The frequency variations observed throughout the solar and stellar cycles contain information about structural changes that take place inside the stars as well as about variations in magnetic field structure and intensity. The task of inferring and disentangling that information is, however, not a trivial one. In the sun and solar-like pulsators, the direct effect of the magnetic field on the oscillations might be significantly important in regions of strong magnetic field (such as solar/stellar spots), where the Lorentz force can be comparable to the gas-pressure gradient. Our aim is to determine the sun-/starspot effect on the oscillation frequencies and attempt to understand if this effect contributes strongly to the frequency changes observed along the magnetic cycle. The total contribution of the spots to the frequency shifts results from a combination of direct and indirect effects of the magnetic field on the oscillations. In this first work we considered only the indirect effect associated with changes in the stratification within the starspot. Based on the solution of the wave equation and the variational principal we estimated the impact of these stratification changes on the oscillation frequencies of global modes in the sun and found that the induced frequency shifts are about two orders of magnitude smaller than the frequency shifts observed over the solar cycle ((c) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Language: English

Type (Professor's evaluation): Scientific