The quest for the solar g modes

TL;DR

This paper reviews the theoretical background, detection efforts, and future prospects of solar gravity (g) modes, which could reveal the solar core's properties but remain undetected despite extensive research.

Contribution

It provides a comprehensive review of the current state of g-mode detection efforts, including theory, techniques, and future directions, highlighting the lack of confirmed detections.

Findings

No undisputed detection of solar g modes yet

Review of detection techniques and their limitations

Discussion of future prospects for unambiguous detection

Abstract

Solar gravity modes (or g modes) -- oscillations of the solar interior for which buoyancy acts as the restoring force -- have the potential to provide unprecedented inference on the structure and dynamics of the solar core, inference that is not possible with the well observed acoustic modes (or p modes). The high amplitude of the g-mode eigenfunctions in the core and the evanesence of the modes in the convection zone make the modes particularly sensitive to the physical and dynamical conditions in the core. Owing to the existence of the convection zone, the g modes have very low amplitudes at photospheric levels, which makes the modes extremely hard to detect. In this paper, we review the current state of play regarding attempts to detect g modes. We review the theory of g modes, including theoretical estimation of the g-mode frequencies, amplitudes and damping rates. Then we go on to discuss the techniques that have been used to try to detect g modes. We review results in the literature, and finish by looking to the future, and the potential advances that can be made -- from both data and data-analysis perspectives -- to give unambiguous detections of individual g modes. The review ends by concluding that, at the time of writing, there is indeed a consensus amongst the authors that there is currently no undisputed detection of solar g modes.