Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufmsh21a1590v&link_type=abstract
American Geophysical Union, Fall Meeting 2008, abstract #SH21A-1590
Astronomy and Astrophysics
Astronomy
2740 Magnetospheric Configuration And Dynamics, 2753 Numerical Modeling, 7509 Corona, 7524 Magnetic Fields, 7539 Stellar Astronomy
Scientific paper
By means of self-consistent three-dimensional (3D) magnetohydrodynamics (MHD) numerical simulations, we analyze magnetized solar-like stellar winds and their dependence on the plasma-β parameter (the ratio between thermal and magnetic energy densities). This is the first study to perform such analysis solving the fully ideal 3D MHD equations. We analyze winds with polar magnetic field intensities ranging from 1 to 20~G. We show that the wind structure presents characteristics that are similar to the solar coronal wind. The steady-state magnetic field topology for all cases is similar, presenting a configuration of helmet streamer-type, with zones of closed field lines and open field lines coexisting. Higher magnetic field intensities lead to faster and hotter winds. For the maximum magnetic intensity simulated of 20~G, the wind velocity reaches values of ~ 1000 km~s-1 at r ~ 20~r0 and a maximum temperature of ~ 6 × 106~K at r~ 6~r0. The increase of the field intensity generates a larger "dead zone" in the wind, i. e., the closed loops that inhibit matter to escape from latitudes lower than ~ 45° extend farther away from the star. The Lorentz force leads naturally to a latitude-dependent wind. We show that by increasing the density, the system recover back to slower and cooler winds. The key parameter in determining the wind velocity profile is the β-parameter. Therefore, there is a group of magnetized flows that would present the same terminal velocity despite of its thermal and magnetic energy densities, as long as the plasma-β parameter is the same. This degeneracy, however, can be removed if we compare other physical parameters of the wind, such as the mass-loss rate.
Gombosi Tamas I.
Jatenco-Pereira Vera
Opher Merav
Vidotto Aline A.
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