Temporal variations in the acoustic signal from faculae

TL;DR

This study analyzes 13 years of solar brightness data to understand how acoustic signals from granulation, faculae, and p-mode oscillations vary over time, revealing their connection to solar cycles and surface phenomena.

Contribution

It demonstrates the temporal variability of facular signals and their correlation with solar activity cycles using long-term integrated brightness observations.

Findings

Facular component significance varies over time, exceeding 0.99 around half the time.

P-mode oscillation amplitudes follow the solar cycle.

Granulation and faculae amplitudes show quasi-annual and quasi-biennial variability.

Abstract

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 analyzing the frequency spectrum of the integrated brightness we can obtain greater knowledge about these phenomena. It is shown how the frequency spectrum of the integrated brightness of the Sun in the frequency range from 0.1 to 3.2 mHz shows clear signs of both granulation, faculae and p-mode oscillations and that the measured characteristic time-scales and amplitudes of the acoustic signals from granulation and faculae are consistent with high-resolution observations of the solar surface. Using 13 years of observations of the Sun's integrated brightness from the VIRGO instrument on the SOHO satellite it is shown that the significance of the facular component varies with time and that it has a significance above 0.99 around half the time. Furthermore, an analysis of the temporal variability in the measured amplitudes of both the granulation, faculae and p-mode oscillation components in the frequency spectrum reveals that the amplitude of the p-mode oscillation component shows variability that follows the solar cycles, while the amplitudes of the granulation and facular components show signs of quasi-annual and quasi-biennial variability, respectively.