What have we learned from helioseismology, what have we really learned, and what do we aspire to learn?

TL;DR

Helioseismology has significantly advanced our understanding of the Sun's internal structure, rotation, and magnetic phenomena, though some broader questions remain open and are still actively researched.

Contribution

This paper reviews the achievements of helioseismology and discusses the ongoing challenges and future directions in understanding solar interior processes.

Findings

Detailed solar interior sound speed and density profiles established

Sun's rotation and sunspot thermal structure mapped

Insights into solar dynamo and energy transport mechanisms

Abstract

Helioseismology has been widely acclaimed as having been a great success: it appears to have answered nearly all the questions that we originally asked, some with unexpectedly high precision. We have learned how the sound speed and matter density vary throughout almost all of the solar interior -- which not so very long ago was generally considered to be impossible -- we have learned how the Sun rotates, and we have a beautiful picture, on a coffee cup, of the thermal stratification of a sunspot, and also an indication of the material flow around it. We have tried, with some success at times, to apply our findings to issues of broader relevance: the test of the General Theory of Relativity via planetary orbit precession (now almost forgotten because the issue has convincingly been closed, albeit no doubt temporarily), the solar neutrino problem, the manner of the transport of energy from the centre to the surface of the Sun, the mechanisms of angular-momentum redistribution, and the workings of the solar dynamo. The first two were of general interest to the broad scientific community beyond astronomy, and were, quite rightly, principally responsible for our acclaimed success; the others are still in a state of flux.