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21.
The magnetosphere is a multi-scale spatio-temporal complex dynamical system. Self-organization is a possible solution to the
seemingly contradicting observation of the repeatable and coherent substorm phenomena with underlying complex behavior in
the plasma sheet. Self-organization, through spatio-temporal chaos, emerges naturally in a plasma physics model with sporadic
dissipation. 相似文献
22.
Space observations in several near-Earth environments have revealed the presence of positive-potential, large-amplitude electrostatic
structures, associated with high-frequency disturbances, and indicative of electron dynamics. Earlier models proposed in terms
of electron-acoustic solitary waves in a two-electron-temperature plasma were inadequate, because only negative potential
structures could thus be obtained, whereas the observations point to positive potential structures. In this paper, it is shown
that the theoretical restriction to negative potential solitons is due to the neglect of the inertia of the hot electrons,
implicitly or explicitly assumed in previous papers. If hot electron inertia is retained, however, there exists a parameter
range where positive potential solitary waves are formed, which can have important consequences for the re-interpretation
of several astrophysical phenomena involving two-electron-temperature plasmas.
PACS: 52.35.Mw, 52.35.Sb, 96.50.Ry 相似文献
23.
A.M. Gulisano S. Dasso C.H. Mandrini P. Dmoulin 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2007,40(12):1881-1890
Magnetic clouds (MCs) are highly magnetized plasma structures that have a low proton temperature and a magnetic field vector that rotates when seen by a heliospheric observer. More than 25 years of observations of magnetic and plasma properties of MCs at 1 AU have provided significant knowledge of their magnetic structure. However, because in situ observations only give information along the trajectory of the spacecraft, their real 3D magnetic configuration remains still partially unknown. We generate a set of synthetic clouds, exploring the space of parameters that represents the possible orientations and minimum distances of the satellite trajectory to the cloud axis, p. The synthetic clouds have a local cylindrical symmetry and a linear force-free magnetic configuration. From the analysis of synthetic clouds, we quantify the errors introduced in the determination of the orientation/size (and, consequently, of the global magnetohydrodynamic quantities) by the Minimum Variance method when p is not zero. 相似文献
24.
Shahida Parveen Shahzad Mahmood Anisa Qamar Muhammad Adnan 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(3):1192-1203
The interaction between two, four and six magnetoacoustic solitons in electron-positron plasmas are investigated. The extended Poincaré–Lighthill–Kuo (PLK) perturbation method is employed to derived two KdV equations for magnetoacoustic solitons moving towards each other and studied the head-on collision between them and their phase shifts. The Hirota bilinear method is used to have multi-soliton solutions of already derived two KdV equations for right and left moving solitons. The four and six magnetoacoustic solitons solutions of the two KdV equations are obtained to discuss their interaction and phase shifts. It is found that only compressive magnetoacoustic solitons structures are formed in electron-positron plasma. The present study may be useful to understand the collective phenomena related to head-on and overtaking magnetoacoustic solitons interaction in electron-positron plasmas that may occur in a pulsar magnetosphere. 相似文献
25.
J.A. Valdivia A. Klimas D. Vassiliadis V. Uritsky J. Takalo 《Space Science Reviews》2003,107(1-2):515-522
Self-organization is a possible solution to the seemingly contradicting observation of the repeatable and coherent substorm
phenomena with underlying complex behavior in the plasma sheet. Self-organization, through spatio-temporal chaos, emerges
naturally in a plasma physics model with sporadic dissipation.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
26.
Mostafa Mehdipoor Mehdi Asri 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(8):2470-2482
The nonlinear propagation of ion–acoustic (IA) waves in a magneto–rotating plasma is studied by considering the Kappa-Cairns electron distribution. Employing the perturbation scheme, Korteweg–de Vries equation is derived. It is seen that both positive and negative potential solitons can be supported in the present plasma model. The numerical results reveal that the Kappa-Cairns distributed electrons modify features of the electrostatic waves significantly. The effects of non–thermal parameters, plasma rotation frequency, ion temperature, and the wave propagation angle on electrostatic solitary wave structures are also discussed here. It is found that the plasma parameters considerably influence the propagation of IA waves in rotating plasmas. Furthermore, using the bifurcation theory of planar dynamical systems to the K-dV equation, we have presented the existence of solitary and periodic traveling waves. Our study may be helpful to understand the behavior of ion–acoustic wave in the rotating plasma. 相似文献
27.
28.
The properties of magnetohydrodynamic waves and instabilities of laboratory and space plasmas are determined by the overall
magnetic confinement geometry and by the detailed distributions of the density, pressure, magnetic field, and background velocity
of the plasma. Consequently, measurement of the spectrum of MHD waves (MHD spectroscopy) gives direct information on the internal
state of the plasma, provided a theoretical model is available to solve the forward as well as the inverse spectral problems.
This terminology entails a program, viz. to improve the accuracy of our knowledge of plasmas, both in the laboratory and in
space. Here, helioseismology (which could be considered as one of the forms of MHD spectroscopy) may serve as a luminous example.
The required study of magnetohydrodynamic waves and instabilities of both laboratory and space plasmas has been conducted
for many years starting from the assumption of static equilibrium. Recently, there is a outburst of interest for plasma states
where this assumption is violated. In fusion research, this interest is due to the importance of neutral beam heating and
pumped divertor action for the extraction of heat and exhaust needed in future tokamak reactors. Both result in rotation of
the plasma with speeds that do not permit the assumption of static equilibrium anymore. In astrophysics, observations in the
full range of electromagnetic radiation has revealed the primary importance of plasma flows in such diverse situations as
coronal flux tubes, stellar winds, rotating accretion disks, and jets emitted from radio galaxies. These flows have speeds
which substantially influence the background stationary equilibrium state, if such a state exists at all. Consequently, it
is important to study both the stationary states of magnetized plasmas with flow and the waves and instabilities they exhibit.
We will present new results along these lines, extending from the discovery of gaps in the continuous spectrum and low-frequency
Alfvén waves driven by rotation to the nonlinear flow patterns that occur when the background speed traverses the full range
from sub-slow to super-fast.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
29.
This review is devoted to ponderomotive forces and their importance for the acceleration of charged particles by electromagnetic
waves in space plasmas. Ponderomotive forces constitute time-averaged nonlinear forces acting on a media in the presence of
oscillating electromagnetic fields. Ponderomotive forces represent a useful analytical tool to describe plasma acceleration.
Oscillating electromagnetic fields are also related with dissipative processes, such as heating of particles. Dissipative
processes are, however, left outside these discussions. The focus will be entirely on the (conservative) ponderomotive forces
acting in space plasmas.
The review consists of seven sections. In Section 1, we explain the rational for using the auxiliary ponderomotive forces
instead of the fundamental Lorentz force for the study of particle motions in oscillating fields. In Section 2, we present
the Abraham, Miller, Lundin–Hultqvist and Barlow ponderomotive forces, and the Bolotovsky–Serov ponderomotive drift. The hydrodynamic,
quasi-hydrodynamic, and ‘`test-particle’' approaches are used for the study of ponderomotive wave-particle interaction. The
problems of self-consistency and regularization are discussed in Section 3. The model of static balance of forces (Section
4) exemplifies the interplay between thermal, gravitational and ponderomotive forces, but it also introduces a set of useful
definitions, dimensionless parameters, etc. We analyze the Alfvén and ion cyclotron waves in static limit with emphasis on
the specific distinction between traveling and standing waves. Particular attention has been given to the impact of traveling
Alfvén waves on the steady state anabatic wind that blows over the polar regions (Section~5). We demonstrate the existence
of a wave-induced cold anabatic wind. We also show that, at a critical point, the ponderomotive acceleration of the wind is
a factor of 3 greater than the thermal acceleration. Section 6 demonstrates various manifestations of ponderomotive forces
in the Earth's magnetosphere, for instance the ionospheric plasma acceleration and outflow. The polar wind and the auroral
density cavities are considered in relation to results from the Freja and Viking satellites. The high-altitude energization
and escape of ions is discussed. The ponderomotive anharmonicity of standing Alfvén waves is analyzed from ground based ULF
wave measurements. The complexity of the many challenging problems related with plasma processes near the magnetospheric boundaries
is discussed in the light of recent Cluster observations. At the end of Section 6, we consider the application of ponderomotive
forces to the diversity of phenomena on the Sun, in the interstellar environment, on newborn stars, pulsars and active galaxies.
We emphasize the role of forcing of magnetized plasmas in general and ponderomotive forcing in particular, presenting some
simple conceivable scenarios for massive outflow and jets from astrophysical objects. 相似文献
30.
Steven J. Schwartz 《Space Science Reviews》2006,124(1-4):333-344
Shocks are found throughout the heliosphere, wherever supersonic (or super-magnetosonic) flows encounter obstacles or other,
slowly moving, media. Although some of the physical parameters are in different regimes, all shocks heat and decelerate the
media incident upon them. Most shocks must propagate in a collisionless plasma, thereby adding importance to the particle
interactions with the electromagnetic fields, and enabling some particles to be accelerated to high energies. This paper explores
the commonalities, and differences, in shocks throughout the heliosphere, and concentrates on the role of shock microstructure
in effecting the shock transition and in governing the resulting energy partition amongst the constituent species. Shocks
play a significant role in the solar-terrestrial chain. 相似文献