Towards a Solution to the Early Faint Sun Paradox: A Lower Cosmic Ray Flux from a Stronger Solar Wind

Abstract

Standard solar models predict a solar luminosity that gradually increased by about 30% over the past 4.5 billion years. Under the faint sun, Earth should have been frozen solid for most of its existence. Yet, running water is observed to have been present since very early in Earth's history. This enigma is known as the faint sun paradox. We show here that it can be partially resolved once we consider the cooling effect that cosmic rays are suspected to have on the global climate and that the younger sun must have had a stronger solar wind, such that it was more effective at stopping cosmic rays from reaching Earth. The paradox can then be completely resolved with the further contribution of modest greenhouse gas warming. When we add the cosmic ray flux modulation by a variable star formation rate in the Milky Way, we recover the long term glacial activity on Earth. As to the future, we find that the average global temperature will increase by typically 10K in the coming 2 Gyr.

8 pages, 3 figures, submitted to JGR

References in corpus (2)

• The Spiral Structure of the Milky Way, Cosmic Rays, and Ice Age Epochs on Earth
• Cosmic Ray Diffusion from the Galactic Spiral Arms, Iron Meteorites, and a possible climatic connection?

Cited by in corpus (17)

• The faint young Sun problem
• Impact of Space Weather on Climate and Habitability of Terrestrial Type Exoplanets
• The Sun in Time: Activity and Environment
• Implications of mass and energy loss due to coronal mass ejections on magnetically-active stars
• Solar structure and evolution
• Warming the early Earth - CO2 reconsidered
• Theoretical mass loss rates of cool main-sequence stars
• Cosmic Rays and Terrestrial Life: A Brief Review
• On climate response to changes in the cosmic ray flux and radiative budget
• The Cosmic Ray Intensity Near the Archean Earth
• Clouds and the Faint Young Sun Paradox
• Radio emission and mass loss rate limits of four young solar-type stars
• On the correlation between the recent star formation rate in the Solar Neighbourhood and the glaciation period record on Earth
• Short-term Variations in the Galactic Environment of the Sun
• Galactic Cosmic Rays - Clouds Effect and Bifurcation Model of the Earth Global Climate. Part 1. Theory
• Radiative forcings for 28 potential Archean greenhouse gases
• Towards a holistic magnetic braking model -- II: explaining several long-term internal- and surface-spin properties of solar-like stars and the Sun