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Reconstructing the Solar Wind From Its Early History To Current Epoch
(15.01.2016)
Аннотация
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.
