76 research outputs found
Self-consistent Coronal Heating and Solar Wind Acceleration from Anisotropic Magnetohydrodynamic Turbulence
We present a series of models for the plasma properties along open magnetic
flux tubes rooted in solar coronal holes, streamers, and active regions. These
models represent the first self-consistent solutions that combine: (1)
chromospheric heating driven by an empirically guided acoustic wave spectrum,
(2) coronal heating from Alfven waves that have been partially reflected, then
damped by anisotropic turbulent cascade, and (3) solar wind acceleration from
gradients of gas pressure, acoustic wave pressure, and Alfven wave pressure.
The only input parameters are the photospheric lower boundary conditions for
the waves and the radial dependence of the background magnetic field along the
flux tube. For a single choice for the photospheric wave properties, our models
produce a realistic range of slow and fast solar wind conditions by varying
only the coronal magnetic field. Specifically, a 2D model of coronal holes and
streamers at solar minimum reproduces the latitudinal bifurcation of slow and
fast streams seen by Ulysses. The radial gradient of the Alfven speed affects
where the waves are reflected and damped, and thus whether energy is deposited
below or above the Parker critical point. As predicted by earlier studies, a
larger coronal ``expansion factor'' gives rise to a slower and denser wind,
higher temperature at the coronal base, less intense Alfven waves at 1 AU, and
correlative trends for commonly measured ratios of ion charge states and
FIP-sensitive abundances that are in general agreement with observations. These
models offer supporting evidence for the idea that coronal heating and solar
wind acceleration (in open magnetic flux tubes) can occur as a result of wave
dissipation and turbulent cascade. (abridged abstract)Comment: 32 pages (emulateapj style), 18 figures, ApJ Supplement, in press (v.
171, August 2007
patrimonio intelectual
Actas de congresoLas VI Jornadas se realizaron con la exposición de ponencias que se incluyeron en cuatro ejes temáticos, que se desarrollaron de modo sucesivo para facilitar la asistencia, el intercambio y el debate, distribuidos en tres jornadas.
Los ejes temáticos abordados fueron:
1. La enseñanza como proyecto de investigación. Recursos de enseñanza-aprendizaje como mejoras de la calidad educativa.
2. La experimentación como proyecto de investigación. Del ensayo a la aplicabilidad territorial, urbana, arquitectónica y de diseño industrial.
3. Tiempo y espacio como proyecto de investigación. Sentido, destino y usos del patrimonio construido y simbólico.
4. Idea constructiva, formulación y ejecución como proyecto de investigación. Búsqueda y elaboración de resultados que conforman los proyectos de la arquitectura y el diseño
Mode-coupling of low-frequency electromagnetic waves in dusty plasmas with temperature anisotropy
This paper studies the effects of the presence of dust particles with variable charge, in fully ionized, homogeneous, magnetized plasma of electrons and ions, with the electrons and ions described by bi-Maxwellian distributions in the equilibrium. The dispersion relation and the absorption rate are obtained for low frequency waves, with frequencies much lower than the ion cyclotron frequency. Two branches are obtained, identified as the whistler branch and the branch of circularly polarized waves, featuring damping due to the Landau damping process and to the collisional charging of the dust particles. The effects of the anisotropy of temperature on the damping rate of low frequency waves, and on the mode coupling which was demonstrated to occur in the isotropic situation, are numerically investigated. The results obtained show that in the anisotropic case the point of mode coupling is displaced to different values of dust density, and that a new point of mode coupling may appear from the effect of the temperature anisotropy
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