Solar structure and evolution

Abstract

The Sun provides a critical benchmark for the general study of stellar structure and evolution. Also, knowledge about the internal properties of the Sun is important for the understanding of solar atmospheric phenomena, including the solar magnetic cycle. Here I provide a brief overview of the theory of stellar structure and evolution, including the physical processes and parameters that are involved. This is followed by a discussion of solar evolution, extending from the birth to the latest stages. As a background for the interpretation of observations related to the solar interior I provide a rather extensive analysis of the sensitivity of solar models to the assumptions underlying their calculation. I then discuss the detailed information about the solar interior that has become available through helioseismic investigations and the detection of solar neutrinos, with further constraints provided by the observed abundances of the lightest elements. Revisions in the determination of the solar surface abundances have led to increased discrepancies, discussed in some detail, between the observational inferences and solar models. I finally briefly address the relation of the Sun to other similar stars and the prospects for asteroseismic investigations of stellar structure and evolution.

Drop of Solar Wind at the End of the 20th Century

“…It is well known that the Sun has variable activity, and the study of solar activity variation and its effect on the Earth on a scale of 1–100 years is one of the main tasks of solar and solar‐terrestrial physics (e.g., Bhargawa & Singh, 2021; Christensen‐Dalsgaard, 2021; De Jager, 2005; Gopalswamy et al., 2020; Hathaway, 2015; Sasikumar Raja et al., 2019; Schwander et al., 2017; Schwenn, 2006; Usoskin, 2017). In the literature, in addition to the well‐studied solar cycles of Schwabe (11 years) and Hale (22 years), the possibility of the Sun approaching the minimum of the Gleissberg (about 90 years) cycle, the so‐called grand minimum, is widely discussed (Dreschhoff et al., 2015; Feynman & Ruzmaikin, 2011; Nagovitsyn et al., 2021; Svalgaard et al., 2005; Zolotova & Ponyavin, 2014).…”

Horizons: Nuclear Astrophysics in the 2020s and Beyond

“…The recent detection of neutrinos from the CNO cycle operating in the solar core by BOREXINO [142] marks a similar milestone. In this case the combination of neutrino observations with precise nuclear reaction rates, for example for the 14 N(p,γ) 15 O reaction, open up a pathway forward to constrain the contents of C, N, and O in the solar core, with prospects of resolving the so called solar abundance problem, a long standing discrepancy between the solar composition inferred from spectroscopy of sunlight and from helioseismology [143]. The CNO neutrino flux depends on the rate of proton capture on 12 C, 14 N and 16 O at very low energies.…”

Stellar convective penetration: parameterized theory and dynamical simulations

“…Convection is a crucial mechanism for transporting heat in stars (Woosley et al 2002;Hansen et al 2004;Christensen-Dalsgaard 2021), and convective dynamics influence many poorly-understood stellar phenomena. For example, convection drives the magnetic dynamo of the Sun, leading to a whole host of emergent phenomena collectively known as solar activity (Brun & Browning 2017).…”