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1.
Observations carried out from the coronagraphs on board space missions (LASCO/SOHO, Solar Maximum and Skylab) and ground-based facilities (HAO/Mauna Loa Observatory) show that coronal mass ejections
(CMEs) can be classified into two classes based on their kinematics evolution. These two classes of CMEs are so-called fast
and slow CMEs. The fast CME starts with a high initial speed that remains more or less constant; it is also called the constant-speed CME. On the other hand, the slow CME starts with a low initial speed, but shows a gradual acceleration; it is also called
the accelerated and slow CME. Low and Zhang [Astrophys. J. 564, L53–L56, 2002] suggested that these two classes of CMEs could be a result of a difference in the initial topology of the
magnetic fields associated with the underlying quiescent prominences. A normal prominence magnetic field topology will lead
to a fast CME, while an inverse quiescent prominence results in a slow CME, because of the nature of the magnetic reconnection
processes. In a recent study given by Wu et al. [Solar Phys. 225, 157–175, 2004], it was shown that an inverse quiescent prominence magnetic topology also could produce a fast CME. In this
study, we perform a numerical MHD simulation for CMEs occurring in both normal and inverse quiescent prominence magnetic topology.
This study demonstrates three major physical processes responsible for destabilization of these two types of prominence magnetic
field topologies that can launch CMEs. These three initiation processes are identical to those used by Wu et al. [Solar Phys. 225, 157–175, 2004]. The simulations show that both fast and slow CMEs can be initiated from these two different types of magnetic
topologies. However, the normal quiescent prominence magnetic topology does show the possibility for launching a reconnection island (or secondary O-line) that might be thought of as a “CME’’. 相似文献
2.
H. Taylor P. Cloutier M. Dryer S. Suess A. Barnes R. Wolff A. Stern 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(7):343-346
During the summer of 1979, solar coronal structure was such that a sequence of recurrent regions produced a corresponding sequence of corotating solar wind streams, with pronounced downstream signatures. One of these stream events passed Earth on July 3, and was observed later at Venus late on July 11th, with similar characteristics. Corresponding in-situ measurements at Earth from the Atmospheric Explorer-E satellite and at Venus from the Pioneer Venus Orbiter are examined for evidence of comparable perturbations of the planetary ionospheres. The passage of the stream shock front is found to be associated with pronounced fluctuations in n(0+) which appear as pronounced local depletion of ion concentrations in both ionospheres. The ionosphere disturbances appear to be closely associated with large variations in the solar wind momentum flux. The implied local ionospheric depletions observed at each planet are interpreted to be the consequence of plasma redistribution, rather than actual depletions of plasma. 相似文献
3.
Murray Dryer 《Space Science Reviews》1974,15(4):403-468
Recent observational and theoretical studies of interplanetary shock waves associated with solar flares are reviewed. An attempt is made to outline the framework for the genesis, life and demise of these shocks. Thus, suggestions are made regarding their birth within the flare generation process, MHD wave propagation through the chromosphere and inner corona, and maturity to fully-developed coronal shock waves. Their subsequent propagation into the ambient interplanetary medium and disturbing effects within the solar wind are discussed within the context of theoretical and phenomenological models. The latter — based essentially on observations — are useful for a limited interpretation of shock geometric and kinematic characteristics. The former — upon which ultimate physical understanding depends — are used for clarification and classification of the shocks and their consequences within the solar wind. Classification of limiting cases of blast-produced shocks (as in an explosion) or longer lasting ejecta (or piston-driven shocks) will hopefully be combined with the study of the flare process itself.The theoretical approach, in spite of its contribution to clarification of various concepts, contains some fundamental limitations and requires further study. Numerical simulations, for example, depend upon a non-unique set of multi-parameter initial conditions at or near the Sun. Additionally, the subtle but important influence of magnetic fields upon energy transport processes within the solar wind has not been considered in the numerical simulation approach. Similarity solutions are limited to geometrical symmetries and have not exploited their potential beyond the special cases of the blast and the constant-velocity, piston-driven shock waves. These continuum fluid studies will probably require augmentation or even replacement by plasma kinetic theory in special situations when observations indicate the presence of anomalous transport processes. Presently, for example, efforts are directed toward identification of detailed shock structures (as in the case of Earth's bow shock) and of the disturbed solar wind (such as the piston).Further progress is expected with extensive in situ and remote monitoring of the solar wind over a wide range of heliographic radii, longitudes and latitudes.This paper is a revised and updated version of an invited review originally presented at the IUGG XV General Assembly, Moscow, U.S.S.R., 2–14 August 1971. 相似文献
4.
Interplanetary studies: Propagation of disturbances between the Sun and the magnetosphere 总被引:6,自引:0,他引:6
Murray Dryer 《Space Science Reviews》1994,67(3-4):363-419
This review is concerned with the interplanetary ‘transmission line’ between the Sun and the Earth's magnetosphere. It starts with comments about coronal mass ejections (CMEs) that are associated with various forms of solar activities. It then continues with some of the current views about their continuation through the heliosphere to Earth and elsewhere. The evolution of energy, mass, and momentum transfer is of prime interest since the temporal/spatial/magnitude behavior of the interplanetary electric field and transient solar wind dynamic pressure is relevant to the magnetospheric response (the presence or absence of geomagnetic storms and substorms) at Earth. Energetec particle flux predictions are discussed in the context of solar activity (flares, prominence eruptions) at various positions on the solar disk relative to Earth's central meridian. A number of multi-dimensional magnetohydrodynamic (MHD) models, applied to the solar, near-Sun, and interplanetary portions of the ‘transmission line’, are discussed. These model simulations, necessary to advancing our understanding beyond the phenomenological or morphological stages, are directed to deceptively simple questions such as the following: can one-to-one associations be made between specific forms of solar activity and magnetosphere response? 相似文献
5.
Results of experiments are reported on the burning of individual decane droplets, initially between 1.0 and 1.2 mm in dia, in air at room temperature and atmospheric pressure. Use was made of the 2.2 s drop tower at the NASA Lewis Research Center and a newly designed droplet-combustion apparatus that promotes nearly spherically symmetrical combustion. Unanticipated disruptions were encountered and related to sooting behavior. 相似文献
6.
7.
M. Dryer D.F. Smart 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(7):291-301
We review the status of the best “off-the-shelf” tool available for the study of dynamical behavior of coronal transients and traveling interplanetary disturbances. This tool involves numerical solution of the initial-boundary value problem of multi-dimensional time-dependent magnetohydrodynamics. While this tool cannot address questions of turbulence and kinetic behavior, we suggest that deeper understanding of large scale phenomena can be obtained by direct comparison of the MHD models with multi-disciplinary synoptic observations of specific events on the sun, and in the corona and interplanetary space. Conclusions reached after a recent critique (based on a limited set of observational and numerical data) of the MHD paradigm's application to coronal transients are examined and found to have limited validity. Substantial observational progress was achieved during SMY through ground- and space-based observations of solar and interplanetary events. Many of these observations can confidently be associated with one another for specific events. These associations can be combined into a reasonable scenario of geometrical extent and mass, energy and momentum transfer in the framework of the solar-terrestrial chain of cause and effect. Several of these events during STIP Interval VII in August 1979 are used to provide test cases for an MHD simulation that is described with some details. The bringing-together of diverse observations is necessary in order to outline a program for the testing of dynamical models and their more physically-restricted approximations. 相似文献
8.
9.
T.E. Gergely M.R. Kundu S.T. Wu M. Dryer Z. Smith R.T. Stewart 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(7):283-286
A large coronal transient took place on 8 May 1981. The transient was related to an M7.7/2B flare and was associated with at least two coronal type II bursts. The velocities of the type II bursts were in the range 1100–1800 kms?1, in excess of the transient velocity of 500–1000 kms?1. Two dimensional positions of the type II radio sources are available from both the Clark Lake and the Culgoora Radio Observatories. We carry out two dimensional MHD simulations of the event, taking into account the observed velocity, position, and size of the type II bursts. We simulate the multiple shocks observed during the event and their interaction, and discuss some results of the simulation. 相似文献
10.
A self-consistent time-dependent, two-dimensional MHD model with a realistic energy equation is developed to understand the origin of bright coronal emission accompanying the occurrence of a new bipolar magnetic region. The motivation for this study is the interpretation of anticipated observations to be made by the SOHO mission.Purple Mt. Obser., PRC 相似文献