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A possible mechanism for the formation and heating of coronal loops through the propagation and damping of fast mode waves is proposed and studied in detail. Loop-like field structures are represented by a dipole field with the point dipole at a given distance below the solar surface. The density of the medium is determined by hydrostatic equilibrium along the field lines in an isothermal atmosphere. The fast mode waves propagating outward from the coronal base are refracted into regions with a low Alfvén speed and suffer collisionless damping when the gas pressure becomes comparable to the magnetic pressure. The propagation and damping of these waves are studied for three different cases: a uniform density at the coronal base, a density depletion within a given flux tube, and a density enhancement within a given flux tube. The fast mode waves are found to be important in the formation and heating of the loops if the wave energy flux density is of the order 105 ergs cm-2 s-1 at the coronal base.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
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A two-fluid model of the solar wind with anisotropic proton temperature and allowing for extended coronal proton-heating is considered for the case of a purely radial and of a spiral magnetic field. Proton-proton Coulomb-collisions together with a spiral interplanetary magnetic field are found to be sufficient to reduce the thermal anisotropy in the proton gas to a value in agreement with observations. Reasonable values are obtained for the flow-velocity, number density and the protontemperature near the orbit of the Earth.This work was supported by the Norwegian Research Council for Science and the Humanities (E. Leer) and the National Aeronautics and Space Administration under Contract No. NGR-05-009-081. 相似文献
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In coronal holes the electron (proton) density is low, and heating of the proton gas produces a rapidly increasing proton temperature in the inner corona. In models with a reasonable electron density in the upper transition region the proton gas becomes collisionless some 0.2 to 0.3 solar radii into the corona. In the collisionless region the proton heat flux is outwards, along the temperature gradient. The thermal coupling to electrons is weak in coronal holes, so the heat flux into the transition region is too small to supply the energy needed to heat the solar wind plasma to coronal temperatures. Our model studies indicate that in models with proton heating the inward heat conduction may be so inefficient that some of the energy flux must be deposited in the transition region to produce the proton fluxes that are observed in the solar wind. If we allow for coronal electron heating, the energy that is needed in the transition region to heat the solar wind to coronal temperatures, may be supplied by heat conduction from the corona. 相似文献
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It is shown that the simultaneous consideration of observed values of the solar wind proton flux density at 1 AU and of the electron pressure at the base of the solar corona leads to relatively strong constraints on the coronal temperature in the region of subsonic solar wind flow. The extreme upper limit on the mean coronal temperature in the subsonic region is found to be about 2.6 × 106 K, but this upper limit is reduced to about 2.0 × 106 K if reasonable, rather than extreme, assumptions are made; the limit on the maximum temperature is about 0.5 × 106 K greater than the limit on the mean. It is also found that the same two observations limit the rate of momentum addition possible in the region of subsonic solar wind flow.On leave from The Auroral Observatory, Institute of Mathematical and Physical Sciences, University of Troms0, N-9001 Tromsø, Norway.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
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Egil Leer 《Solar physics》1974,35(2):467-480
A one-fluid model of the solar atmosphere is considered. The corona is heated by waves propagating out from the Sun, and profiles for temperature, flow speed and number density are obtained. For a relatively quiet Sun the inwards heat flux in the inner corona is constant in T 5–6 × 105 K and the temperature maximum is reached for r — R = 0.4 — 0.5 R where R
is the solar radius. The number density in the inner corona decreases with an increasing particle flux. 相似文献
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The effect of an interplanetary atomic hydrogen gas on solar wind proton, electron and α-particle temperatures beyond 1 AU
is considered. It is shown that the proton temperature (and probably also the α-particle temperature) reaches a minimum between
2 AU and 4 AU, depending on values chosen for solar wind and interstellar gas parameters. Heating of the electron gas depends
primarily on the thermal coupling of the protons and electrons. For strong coupling (whenT
p
≳T
e
), the electron temperature reaches a minimum between 4 AU and 8 AU, but for weak coupling (Coulomb collisions only), the
electron temperature continues to decrease throughout the inner solar system. A spacecraft travelling to Jupiter should be
able to observe the heating effect of the solar wind-interplanetary hydrogen interaction, and from such observations it may
be possible of infer some properties of the interstellar neutral gas.
Currently a National Research Council Resident Research Associate. 相似文献
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