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Universality and Diversity of Solar Winds Driven by Nonlinear Low-Frequency Alfvén Waves from the Photosphere -Fast/Slow Winds and Disappearance of Solar Winds-  

Takeru Suzuki   Submitted: 2005-10-31 15:26

(abridged) We investigate how the properties of the corona and solar wind in the open coronal holes depend on the properties of the magnetic fields and their footpoint motions at the surface, by perfoming 1D MHD simulations from the photosphere to 0.3 or 0.1AU. We impose low-frequency (<0.05Hz) 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, B, and super-radial expansion of the cross section, f_max. We find that a transonic solar wind is the universal consequence. The atmosphere is also stably heated up to >106K by the dissipation of the Alfvén waves through compressive-wave generation and wave reflection in the case of the sufficient wave input with photospheric amplitude, <dv> > 0.7km s-1. The density, and accordingly the mass flux, of solar winds show a quite sensitive dependence on <dv> because of an unstable aspect of the heating by the nonlinear Alfvén waves. A case with <dv>=0.4km s-1 gives ~50 times smaller mass flux than the fiducial case for the fast wind with <dv>=0.7km s-1; solar wind almost disappears only if <dv> becomes half. We also find that the solar wind speed has a positive correlation with B/f_max, which is consistent with recent observations. We finally show that both fast and slow solar winds can be explained by the single process, the dissipation of the low-frequency Alfvén waves, with different sets of <dv> and B/f_max. Our simulations naturally explain the observed (i) anticorrelation of the solar wind speed and the coronal temperature and (ii) larger amplitude of the Alfvénic fluctuations in the fast winds. In Appendix, we also explain our implementation of the outgoing boundary condition of the MHD waves with some numerical tests.

Authors: Takeru K. Suzuki & Shu-ichiro Inutsuka
Projects:

Publication Status: Submitted for publication in JGR, available on astro-ph/0511006
Last Modified: 2005-10-31 15:30
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Successful Coronal Heating and Solar Wind Acceleration by MHD Waves by Numerical Simulations from Photosphere to 0.3AU  

Takeru Suzuki   Submitted: 2005-08-25 19:44

We show that the coronal heating and the acceleration of the fast solar wind in the coronal holes are natural consequence of the footpoint fluctuations of the magnetic fields at the photosphere by one-dimensional, time-dependent, and nonlinear magnetohydrodynamical simulation with radiative cooling and thermal conduction. We impose low-frequency (<0.05Hz) transverse photospheric motions, corresponding to the granulations, with velocity <dv> = 0.7km s-1. In spite of the attenuation in the chromosphere by the reflection, the sufficient energy of the generated outgoing Alfvén waves transmit into the corona to heat and accelerate of the plasma by nonlinear dissipation. Our result clearly shows that the initial cool (104K) and static atmosphere is naturally heated up to 106K and accelerated to 800km s-1, and explain recent SoHO observations and Interplanetary Scintillation measurements.

Authors: Takeru K. Suzuki & Shu-ichiro Inutsuka
Projects: None

Publication Status: Contribution talk at Solar Wind11/SOHO16, available at astro-ph/0508568
Last Modified: 2005-08-25 19:44
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Making the corona and the fast solar wind: a self-consistent simulation for the low-frequency Alfvén waves from photosphere to 0.3AU  

Takeru Suzuki   Submitted: 2005-06-27 07:29

We show that the coronal heating and the fast solar wind acceleration in the coronal holes are natural consequence of the footpoint fluctuations of the magnetic fields at the photosphere by performing 1-dimensional magnetohydrodynamical simulation with radiative cooling and thermal conduction. We initially set a static open flux tube with temperature 104K rooted at the photosphere. We impose transverse photospheric motions, corresponding to the granulations, with velocity <dvperp> = 0.7km s-1 and period between 20seconds and 30minutes, which generate outgoing Alfvén waves. We self-consistently treat these waves and the plasma heating. After attenuation in the chromosphere by ~=85% of the initial energy flux, the outgoing Alfvén waves transmit into the corona to contribute to the heating and acceleration of the plasma mainly by nonlinear generation of the compressive waves. Our result clearly shows that the initial cool and static atmosphere is naturally heated up to 106K and accelerated to ~=800km s-1.

Authors: Takeru K. Suzuki & Shu-ichiro Inutsuka
Projects: None

Publication Status: ApJL, vol. 632, L49, also available on astro-ph/0506639
Last Modified: 2005-10-31 15:28
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Abstracts by Author
Universality and Diversity of Solar Winds Driven by Nonlinear Low-Frequency Alfven Waves from the Photosphere -Fast/Slow Winds and Disappearance of Solar Winds-
Successful Coronal Heating and Solar Wind Acceleration by MHD Waves by Numerical Simulations from Photosphere to 0.3AU
Making the corona and the fast solar wind: a self-consistent simulation for the low-frequency Alfven waves from photosphere to 0.3AU

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