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Propagation of shock related Moreton and EUV waves in the solar atmosphere is simulated by the nonlinear geometrical acoustics
method. This method is based on the ray approximation and takes account of nonlinear wave features: dependence of the wave
velocity on its amplitude, nonlinear dissipation of wave energy in the shock front, and the increase in its duration with
time. The paper describes ways of applying this method to solve the propagation problem of a blast magnetohydrodynamic shock
wave. Results of analytical modeling of EUV and Moreton waves in the spherically symmetric and isothermal solar corona are
also presented. The calculations demonstrate deceleration of these waves and an increase in their duration. The calculation
results of the kinematics of the EUV wave observed on the Sun on January 17, 2010 are presented as an example. 相似文献
12.
We present the results of analytical modelling of fast-mode magnetohydrodynamic wave propagation near a 2D magnetic null point. We consider both a linear wave and a weak shock and analyse their behaviour in cold and warm plasmas. We apply the nonlinear geometrical acoustics method based on the Wentzel–Kramers–Brillouin approximation. We calculate the wave amplitude, using the ray approximation and the laws of solitary shock wave damping. We find that a complex caustic is formed around the null point. Plasma heating is distributed in space and occurs at a caustic as well as near the null point due to substantial nonlinear damping of the shock wave. The shock wave passes through the null point even in a cold plasma. The complex shape of the wave front can be explained by the caustic pattern. 相似文献
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V. V. Grechnev A. M. Uralov I. M. Chertok V. A. Slemzin B. P. Filippov Y. I. Egorov V. G. Fainshtein A. N. Afanasyev N. P. Prestage M. Temmer 《Solar physics》2014,289(4):1279-1312
We continue our study (Grechnev et al., 2013, doi: 10.1007/s11207-013-0316-6 ; Paper I) on the 18 November 2003 geoffective event. To understand possible impact on geospace of coronal transients observed on that day, we investigated their properties from solar near-surface manifestations in extreme ultraviolet, LASCO white-light images, and dynamic radio spectra. We reconcile near-surface activity with the expansion of coronal mass ejections (CMEs) and determine their orientation relative to the earthward direction. The kinematic measurements, dynamic radio spectra, and microwave and X-ray light curves all contribute to the overall picture of the complex event and confirm an additional eruption at 08:07?–?08:20 UT close to the solar disk center presumed in Paper I. Unusual characteristics of the ejection appear to match those expected for a source of the 20 November superstorm but make its detection in LASCO images hopeless. On the other hand, none of the CMEs observed by LASCO seem to be a promising candidate for a source of the superstorm being able to produce, at most, a glancing blow on the Earth’s magnetosphere. Our analysis confirms free propagation of shock waves revealed in the event and reconciles their kinematics with “EUV waves” and dynamic radio spectra up to decameters. 相似文献
15.
We show a mechanism whereby the jets result during the development of β-plumes (i.e., low-frequency Rossby waves that establish gyre circulations) in a model of ocean-basin circulation. The energy originates in baroclinic meanders of circulation at the eastern boundary of the ocean. Eddies are intimately related and occur as a result of the instability of this process. This mechanism does not rely on the existence of the small-scale turbulence to establish zonal flows. Zonal jets can then be amplified by eddies arranged in certain order in the flow. The underlying dynamics include the propagation of linear and nonlinear basin scale Rossby waves. The related barotropic theory for these waves is developed here. We demonstrate the radiative development of jets and β-plumes in a laboratory experiment using a rotating fluid with a paraboloidal free surface. The dynamical fields are measured by the laboratory analog of the satellite altimetry. 相似文献
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