The extended minimum of solar cycle 23 as seen by radial velocity (GOLF, GONG) and intensity (VIRGO) helioseismic instruments

TL;DR

This study analyzes solar oscillation data from multiple instruments during solar cycle 23 and its extended minimum, revealing how p-mode frequencies responded to unusual surface activity levels.

Contribution

It provides a comparative analysis of p-mode frequency variations during the deep solar minimum using data from space-based and ground-based helioseismic instruments.

Findings

P-mode frequencies showed distinct variations during the extended solar minimum.

Different angular degrees of p-modes responded differently to the solar activity changes.

The study highlights the sensitivity of helioseismic measurements to solar activity levels.

Abstract

We present an analysis of the variability of the solar oscillation spectrum during solar cycle 23 and its extended minimum. We use simultaneous observations of the low-degree solar p modes collected by the space-based, Sun-as-a-star GOLF (radial velocity) and VIRGO (intensity) instruments, and by the ground-based, multi-site network GONG. We investigate in particular the response of the p-mode eigenfrequencies to the observed peculiar deep solar minimum of surface activity of 2007-2009 as compared with the previous solar cycle 23. We study the different temporal variations of the p-mode frequencies with individual angular degrees.