Reconstructing the Solar Wind From Its Early History To Current Epoch

TL;DR

This study uses advanced 3D magnetohydrodynamic modeling to reconstruct the early solar wind's properties, revealing its evolution over billions of years and implications for planetary atmospheres and magnetospheres.

Contribution

It introduces a comprehensive MHD model that accounts for turbulence and separate plasma components to simulate the solar wind's evolution over time.

Findings

Early solar wind was faster, denser, and hotter at 0.7 Gyr.

Model results align with empirical data for stars of different ages.

Findings provide constraints on wind pressures affecting planetary magnetospheres.

Abstract

Stellar winds from active solar type stars can play a crucial role in removal of stellar angular momentum and erosion of planetary atmospheres. However, major wind properties except for mass loss rates cannot be directly derived from observations. We employed a three dimensional magnetohydrodynamic Alfven wave driven solar wind model, ALF3D, to reconstruct the solar wind parameters including the mass loss rate, terminal velocity and wind temperature at 0.7, 2 and 4.65 Gyr. Our model treats the wind thermal electrons, protons and pickup protons as separate fluids and incorporates turbulence transport, eddy viscosity, turbulent resistivity, and turbulent heating to properly describe proton and electron temperatures of the solar wind. To study the evolution of the solar wind, we specified three input model parameters, the plasma density, Alfven wave amplitude and the strength of the dipole magnetic field at the wind base for each of three solar wind evolution models that are consistent with observational constrains. Our model results show that the velocity of the paleo solar wind was twice as fast, about 50 times denser and 2 times hotter at 1 AU in the Suns early history at 0.7 Gyr. The theoretical calculations of mass loss rate appear to be in agreement with the empirically derived values for stars of various ages. These results can provide constraints for wind dynamic pressures on magnetospheres of (exo)planets around the young Sun and other active stars, which is crucial in realistic assessment of the Joule heating of their ionospheres and corresponding effects of atmospheric erosion.