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Temporal variations in the acoustic signal from faculae

Karoff, C.

The integrated brightness of the Sun shows variability on time-scales from minutes to decades. This variability is mainly caused by pressure mode oscillations, by granulation and by dark spots and bright faculae on the surface of the Sun. By analysing the frequency spectrum of the integrated brightness, we can obtain greater knowledge about these …

Principal component analysis of background and sunspot magnetic field variations during solar cycles 21-23

Zharkova, V. V.; Shepherd, S. J.; Zharkov, S. I.

The aim of this paper is to derive the principal components (PCs) in variations of (i) the solar background magnetic field (SBMF), measured by the Wilcox Solar Observatory with low spatial resolution for solar cycles 21-23, and (ii) the sunspot magnetic field (SMF) in cycle 23, obtained by SOHO/MDI. For reduction of the component dimensions, princ…

Acoustic spectrum fitting for a large set of solar-like pulsators

Baudin, F.; Chaplin, W. J.; Elsworth, Y. +2 more

Asteroseismology provides the means both to constrain the global properties and to probe the internal structures of stars. Asteroseismic data are now available on large numbers of solar-type stars, thanks in particular to the CoRoT and Kepler space missions, and automated data-analysis pipelines are needed to provide efficient and timely results. …

A new method to detect solar-like oscillations at very low S/N using statistical significance testing

Chaplin, William J.; Kjeldsen, Hans; Lund, Mikkel N.

We introduce a new method to detect solar-like oscillations in frequency power spectra of stellar observations, under conditions of very low signal-to-noise ratio. The Moving-Windowed-Power-Search (MWPS) searches the power spectrum for signatures of excess power, over and above slowly varying (in frequency) background contributions from stellar gr…

Misleading variations in estimated rotational frequency splittings of solar p modes: consequences for helioseismology and asteroseismology

Chaplin, William J.; García, Rafael A.; Mathur, Savita +4 more

The aim of this paper is to investigate whether there are any 11-yr or quasi-biennial solar-cycle-related variations in solar rotational splitting frequencies of low-degree solar p modes. Although no 11-yr signals were observed, variations on a shorter time-scale (∼2 yr) were apparent. We show that the variations arose from complications/artefacts…