The Sun in Time: Activity and Environment

By M. Gudel. 2007

189 citations recorded by the source corpus.

The Sun’s magnetic activity has steadily declined during its main-sequence life. While the solar photospheric luminosity was about 30% lower 4.6 Gyr ago when the Sun arrived on the main sequence compared to present-day levels, its faster rotation generated enhanced magnetic activity; magnetic heating processes in the chromosphere, the transition region, and the corona induced ultraviolet, extreme-ultraviolet, and X-ray emission about 10, 100, and 1000 times, respectively, the present-day levels, as inferred from young solar-analog stars. Also, the production rate of accelerated, high-energy particles was orders of magnitude higher than in present-day solar flares, and a much stronger wind escaped from the Sun, permeating the entire solar system. The consequences of the enhanced radiation and particle fluxes from the young Sun were potentially severe for the evolution of solar-system planets and moons. Interactions of high-energy radiation and the solar wind with upper planetary atmospheres may have led to the escape of important amounts of atmospheric constituents. The present dry atmosphere of Venus and the thin atmosphere of Mars may be a product of early irradiation and heating by solar high-energy radiation. High levels of magnetic activity are also inferred for the pre-main sequence Sun. At those stages, interactions of high-energy radiation and particles with the circumsolar disk in which planets eventually formed were important. Traces left in meteorites by energetic particles and anomalous isotopic abundance ratios in meteoritic inclusions may provide evidence for a highly active pre-main sequence Sun. The present article reviews these various issues related to the magnetic activity of the young Sun and the consequent interactions with its environment. The emphasis is on the phenomenology related to the production of high-energy photons and particles. Apart from the activity on the young Sun, systematic trends applicable to the entire main-sequence life of a solar analog are discussed.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/320a235873f2b9e3717d99aa78a78c5d9df54fff

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In Astronomy and Astrophysics

Citations in the corpus

Origin and loss of nebula-captured hydrogen envelopes from ‘sub’- to ‘super-Earths’ in the habitable zone of Sun-like stars (2014, background): “…environment of young solar-like stars indicate that the assumed EUV and far-UV flux values by Sekiya et al. (1980b; 1981) have been too high and/or lasted for shorter timescales (Guinan et al. 2003; Ribas et al. 2005; Güdel 2007; Claire et al. 2012; Lammer et al. 2012; and references therein).”
Mercury’s Weather-Beaten Surface: Understanding Mercury in the Context of Lunar and Asteroidal Space Weathering Studies (2014, background): “Additional clues about the Sun over geologic timescales come from studies of solaranalog stars (Ribas et al. 2005; Wood 2006; Güdel 2007; Guinan and Engle 2009).”
Do Kepler Superflare Stars Really Include Slowly Rotating Sun-like Stars?—Results Using APO 3.5 m Telescope Spectroscopic Observations and Gaia-DR2 Data (2019, background): “Previous observations of solar-type stars (e.g., X-ray, UV, Ca II H and K) have shown that the stellar magnetic activity level decreases as rotation period increases (e.g., Noyes et al. 1984; Güdel 2007; Wright et al. 2011).”
JUPITER MODELS WITH IMPROVED AB INITIO HYDROGEN EQUATION OF STATE (H-REOS.2) (2011, background): “On the other hand, non-standard solar evolution models that predict a bright and more massive young Sun (Sackmann & Boothroyd 2003) cannot completely be ruled out by observationally derived stellar mass loss rates, see Güdel (2007) for a review.”
The faint young Sun problem (2012, background): “…and Fowler , 2011], life on the early Earth [Nisbet and Sleep, 2001], evolution of the terrestrial planets and considerations of planetary habitability [Pollack , 1979; Rampino and Caldeira, 1994; Kasting and Catling , 2003] or the evolution of the Sun [Kasting and Grinspoon, 1991; Güdel , 2007].”