Solar winds driven by nonlinear low‐frequency Alfvén waves from the photosphere: Parametric study for fast/slow winds and disappearance of solar winds
By T. Inutsuka. 2005
134 citations recorded by the source corpus.
[1] We investigate how properties of the corona and solar wind in open coronal holes depend on properties of magnetic fields and their footpoint motions at the surface. We perform one-dimensional magnetohydrodynamical (MHD) simulations for the heating and the acceleration in coronal holes by low-frequency Alfven waves from the photosphere to 0.3 or 0.1 AU. We impose low-frequency (≲0.05 Hz) transverse fluctuations of the field lines at the photosphere with various amplitude, spectrum, and polarization in the open flux tubes with different photospheric field strength, Br,0, and superradial expansion of the cross section, fmax. We find that transonic solar winds are universal consequences. The atmosphere is also stably heated up to ≳106 K by the dissipation of the Alfven waves through compressive-wave generation and wave reflection in the cases of the sufficient wave input with photospheric amplitude, 〈dv⊥,0〉 ≳ 0.7 km s−1. The density, and accordingly the mass flux, of solar winds show a quite sensitive dependence on 〈dv⊥,0〉 because of an unstable aspect of the heating by the nonlinear Alfven waves. A case with 〈dv⊥,0〉 = 0.4 km s−1 gives ≃50 times smaller mass flux than the fiducial case for the fast wind with 〈dv⊥,0〉 = 0.7 km s−1; solar wind virtually disappears only if 〈dv⊥,0〉 becomes ≃1/2. We also find that the solar wind speed has a positive correlation with Br,0/fmax, which is consistent with recent observations by Kojima et al. On the basis of these findings, we show that both fast and slow solar winds can be explained by the single process, the dissipation of the low-frequency Alfven waves, with different sets of 〈dv⊥,0〉 and Br,0/fmax. Our simulations naturally explain the observed (1) anticorrelation of the solar wind speed and the coronal temperature and (2) larger amplitude of Alfvenic fluctuations in the fast wind. In Appendix A, we also explain our implementation of the outgoing boundary condition of the MHD waves with some numerical tests.
Subfields: Astronomy and Astrophysics, Molecular Biology
View Paper: https://www.semanticscholar.org/paper/7d6c6303bc1e5df74468aeccec9bcf1fa3931add
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Citations in the corpus
- The Solar Probe Plus Mission: Humanity’s First Visit to Our Star (2016, background): “Coronal heating and acceleration models based solely on this effect have been developed recently (Suzuki and Inutsuka 2006) leading to a solar wind which contains extremely large fluctuations in radial velocity and density close to the Sun.”
- Who Needs Turbulence? (2011, background): “1997): a coronal heating and acceleration model based solely on this effect has been developed in one dimension (Suzuki and Inutsuka 2006) leading to a solar wind that contains extremely large fluctuations in radial velocity and density oscillations close to the sun.”
- The Magnetic Landscape of the Sun's Polar Region (2008, background): “Alfvén waves are believed to play a vital role in the acceleration and heating of the fast solar wind (Hollweg 1972; Suzuki & Inutsuka 2006).”
- Accretion-powered Stellar Winds. II. Numerical Solutions for Stellar Wind Torques (2008, background): “Two important recent studies have done self-consistent analyses of the combined problem of both solar wind heating and acceleration (Suzuki & Inutsuka 2006; Cranmer et al. 2007).”
- Origins of the Ambient Solar Wind: Implications for Space Weather (2017, background): “…to gen- erate wave-like fluctuations that propagate up into the extended corona (Coleman 1968; Hollweg 1986; Velli et al. 1991; Matthaeus et al. 1999; Suzuki and Inutsuka 2006; Cranmer et al. 2007; Ofman 2010; van Ballegooijen et al. 2011; Chandran et al. 2011; Matsumoto and Suzuki 2012; Perez and…”