Interaction Of Plasma Flow Research Articles

Multiple shocks near Mars

Mars presents us with an example of a magnetosheath in which the interaction of the solar wind with planetary plasma of heavy ions results in a generation of strong nonlinear bi-ion MHD waves. These waves provide oscillations in the momentum exchange between protons and heavy ions and may give rise to multiple shock-like structures. One-dimensional hybrid simulations of plasma flow interaction with a “heavy ion obstacle” were performed to study the generation of shock waves in bi-ion plasma. A differential motion of protons and heavy ions leads to bunching of heavy ion flow picked up by solar wind. Plasma bunching arises because of a resonant interaction between magnetosound waves excited by beam and “slow” waves of a spatial charge in the heavy ion flow. Both kinds of waves grow, steepen and gradually evolve to shocks.

A Possible Mechanism for the Origin of Emerging Flux in the Sunspot Moat

Mass and energy flow near sunspots are associated with the emergence of magnetic flux, which then moves outward in the sunspot moat. We present results of analytical and numerical studies of the interaction of horizontal magnetic flux and plasma flows in three-dimensional geometry. We show that nonlinear coupling of flux and plasma flows in the presence of a gravitational field lead to nonlinear dissipative instabilities that result in the formation of a solitary kink along the magnetic flux. The stability of a kink and its further evolution depend on the physical parameters of magnetic flux and the surrounding medium. We discuss two major cases—magnetic soliton-like and shocklike propagation along the magnetic flux—and specify the appropriate physical conditions for their realization. In photospheric conditions, the proposed mechanism may be a good candidate for understanding of the dynamics of small-scale magnetic flux in the enhanced network at the solar surface. We apply our results to the observed properties of emerging flux in the sunspot region associated with moving magnetic features and find reasonable qualitative and quantitative agreement.

Interaction of turbulent plasma flow with a hypersonic shock wave

A transient increase is observed in both the spectral energy decay rate and the degree of chaotic complexity at the interface of a shock wave and a turbulent ionized gas. Even though the gas is apparently brought to rest by the shock wave, no evidence is found either of prompt relaminarization or of any systematic influence of end-wall material thermal conductivities on the turbulence parameters.

Current sheets in the solar atmosphere

The 2D and 3D numerical simulation is used for the investigation of current sheet (CS) creation above the active region. The current sheet in the solar corona can be created either in vicinity of a magnetic field singular line by focusing disturbances or at the interaction of the super-Alfvenic plasma flow with the perpendicular magnetic field.

Features of dynamics and structure of the shielding layer at the interaction of plasma flow with target

In the report we discuss the experimental results of powerful plasma-flow interactions with aluminum, graphite and stainless steel targets. The experiments were done with magnetized and non-magnetized plasma flows. The plasma flow was generated by a quasistationary plasma accelerator (QSPA). The feature of the experiments is that the research was made at effect on target of high power and long-time duration flows. Such flows give the possibility to simulate the long-time disruptions in ITER. The formation and structure of the shielding layer were investigated by space and time resolution measurements of spectrum. The erosion depth was measured by loss of target weight.

A new model of interaction between the solar wind and the local interstellar wind

The interaction of subsonic plasma flow with a neutral particle cloud via charge exchange is considered. We derive a general expression for the velocity potential of the plasma flow induced by charge exchange interaction in the axisymmetric case. The particular case of the interaction of uniform plasma flow with a spherically symmetric distribution of neutral particles is considered in detail. It is shown that charge exchange interaction is able to stagnate the plasma flow completely at a finite distance along the stagnation line, and to redirect the plasma flow around the neutral cloud. We argue that this simple situation could represent the main features of the interaction of the interstellar wind with high‐speed solar hydrogen flowing from the inner heliosphere. Thus the heliopause could in part, if not as a whole, actually result from this particular form of charge exchange interaction. The degree of ionization of the local interstellar medium is shown to determine the extent of the role of the charge exchange interaction. For a partially ionized interstellar wind, charge exchange plays the main role in slowing down and stagnating the interstellar wind, while for a highly ionized interstellar wind, its role is secondary to the direct gasdynamic interaction of the two counter streaming plasmas.

MHD-aspects of EML efficiency increase due to channel segmentation

It is known that one of the possible ways to increase the electromagnetic launcher (EML) efficiency is to segment the working channel. This paper presents the results of the theoretical investigation of the MHD-processes in a railgun channel for two types of segmented launchers: (A) segmented configuration where all segments are the independent railguns divided by inter-stage dielectric inserts, and (B) distributed configuration which has the nonsegmented rails and distributed energy sources. The operation of each stage of a segmented railgun is determined by intricate MHD-flows. The plasma flow interaction with the magnetic field is of complex character and has an ambiguous influence on the muzzle velocity. The character of the discharge behaviour was investigated for both schemes. The influence of the current shape, of augmentation, of section length and the optimization of the multistage railgun operation for these parameters were studied. It is shown that the energy input to the plasma armature by means of short fast current pulses reduces momentum losses and provides the considerable velocity increase.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Detection of wave phenomena in the solar corona using radio occultation methods

Solar wind irregularities modulate the radio waves propagating in the solar corona and supercorona. The magnitude of the fluctuations is determined by the intensity of electron density irregularities and their characteristic period by the irregularities velocity. Detailed analysis shows however that the velocity registered in radio occultation experiments is actually a combination of two velocities, namely the velocity of plasma flows and that of the magnetohydrodynamic waves. This feature may manifest itself in several maxima in the correlation functions of the frequency fluctuations in signals registered at several ground stations. The interaction of plasma flows with the magnetosonic waves propagating from and toward the Sun results correspondingly in higher and lower apparent velocity of the irregularities. It was proved in radio occultation data obtained using spacecraft Venera-15,-16, Viking and Voyager.

Interaction of powerful high density plasma flows with the surface of a solid

Interaction of powerful high density plasma flows with the surface of a solid

Interaction of field‐aligned cold plasma flows with an equatorially‐trapped hot plasma: Electrostatic shock formation

Effects of equatorially trapped hot plasma on the highly supersonic cold‐plasma flow occurring during early stage plasmaspheric refilling are studied by means of numerical simulations. It is shown that the equatorially trapped hot ions set up a potential barrier for the cold ion beams and facilitate formation of electrostatic shocks by reflecting them from the equatorial region. Simulations with and without the hot plasma show different flow properties; the formation of electrostatic shocks occur only in the former case. The simulation with the hot plasma also reveals that the magnetic trapping in conjunction with the evolution of the electrostatic potential barrier produces ion velocity distribution functions consisting of a cold core and a hot ring in the perpendicular velocity. Such a distribution function provides a source of free energy for equatorial waves. The corresponding electron population is warm and field aligned.

Solitary vortex type motions of the mass loaded magnetized plasma flow

In situ observations of plasma and magnetic fields in vicinity of comets have shown existence of diamagnetic disturbances of the plasma of high amplitudes. The physical nature of such disturbances is not well understood by now. In this paper we note that the same to observed features have some kinds of nonlinear solitary vortex type disturbances. These type of motion is supported by plasma density, magnetic field or pressure gradients, which provides effective gravity in system. To analyze this possibility the early developed two-dimensional kinetic description of the magnetized plasma flow with mass loading is used. The solutions of the solitary vortex type superimposed on the regular plasma flow are considered both analytically and numerically. Numerical results are used to derive the relations between solitary vortex and averaged plasma flow parameters. This results are discussed in connection with the experimental observations of the solar wind plasma flow interaction with comet.

About the parametric interplay between ionic Mach number, body‐size, and satellite potential in determining the ion depletion in the wake of the S3‐2 satellite

Measurements of ion current, electron temperature, and density and values of satellite potential from the U.S. Air Force Satellite S3‐2 together with ion composition measurements from the Atmosphere Explorer (AE‐E) satellite were used to examine the variation of the ratio α=[I+(wake)]/[I+(ambient)]| (where I+ is the ion current) with altitude and to examine the significance of the parametric interplay between ionic Mach number, normalized body size RD (=R0/λD, where R0 is the satellite radius and λD is the ambient debye length) and normalized body potential ϕN (=eϕS/KTe, where ϕs is the satellite potential, Te is the electron temperature, and e and K are constants). It was possible to separate between the influence of RD and ϕN on α for a specific range of plasma parameters. Uncertainty, however, remains regarding the competition between RD and S(H+) and S(O+) (where S(O+) and S(H+) are oxygen and hydrogen ionic Mach numbers, respectively) in determining the ion distribution in the nearest vicinity to the satellite surface. A brief discussion relevant to future experiments in the area of body plasma flow interactions to be conducted on board the Shuttle/Spacelab facility, is also included.

Shuttle-era experiments in the area of plasma flow interactions with bodies in space

A new experimental approach is discussed in general terms, that can be adopted in the Shuttle/Spacelab era starting in the 1980s for studies in the area of plasma flow interactions with bodies in space. The potential use of the Space Shuttle/Orbiter as a near Earth plasma laboratory for studies in the area of Space Plasma Physics and particularly in the area of Solar-System Plasmas is discussed. This new experimental approach holds great promise for studies in the Supersonic and sub-Alfvenic flow regime which has applications to the motion of natural satellites around their mother planets in the Solar-system (e.g. the satellite Io around the planet Jupiter). A well conceived experimental and theoretical program, can lead to a better physical understanding regarding the validity and range of applicability of using gas-dynamic, kinetic and fluid approaches in describing collisionless plasma flow interactions with bodies in a variety of flow regimes. In addition to the above scientific aspects of the program, significant technological advances can be achieved regarding the interaction of space probes in planetary atmospheres/ionospheres and the reliability of using various plasma diagnostic devices on board spacecraft and large space platforms.

Interaction between a Shock-Heated Plasma and a Nozzle-Shaped Magnetic Field

The magnetohydrodynamic (MHD) equations for the interaction of a shock-heated plasma flow with a nozzle-shaped magnetic field are solved numerically with the two-step Lax-Wendroff method using the time-splitting technique. The results are compared with the experimental data obtained with an arc-driven shock tube. The measured output voltage of pickup coils and the measured luminosity profiles in the shock front agree well to calculations.

Technique for measuring the differential ion flux vector

A diagnostic technique is discussed which gives the angle of incidence of a plasma stream, the energy corresponding to the mean velocity of the ions, and the distribution of the ion thermal motion superimposed on the drift. The technique is shown to be operable for low-energy plasma streams (5–60 eV) and in the presence of multiple plasma streams differing in direction and/or energy. Resolution is better than 3.5° with ∼1% energy spread in the streams. The instrument samples the plasma at a single region in space, independent of the number of plasma streams or their characteristics. The technique was developed to investigate plasma flow interactions in the laboratory. Its capabilities are demonstrated by some preliminary data taken for the case of a long cylindrical body inmersed in a drifting, collisionless plasma.

Radiation characteristics of the zone of interaction of hypersonic plasma flows with obstacles in the vacuum-ultraviolet range

Radiation characteristics of the zone of interaction of hypersonic plasma flows with obstacles in the vacuum-ultraviolet range

Numerical Study of the Interaction of Shock-Heated Plasma Flows with Transverse Magnetic Fields

The magnetohydrodynamic (MHD) equations for the interaction of shock-induced plasma flows with transverse magnetic fields are solved numerically by taking into account the radiative energy loss; real gas effects such as variable degrees of ionization are also considered. The one-dimensional flow is assumed. The results are compared with experimental data obtained with an arc-driven shock tube whose test section is similar to the MHD generator of the Faraday type. The continuum radiation intensity is measured as a function of time. Good agreement is obtained in the time histories of the calculated and measured continuum radiation intensities at the position where the flow is one-dimensional.

Radiation Cooling Effects on Interaction of a Shock-Heated Plasma Flow with a Transverse Magnetic Field

Radiation Cooling Effects on Interaction of a Shock-Heated Plasma Flow with a Transverse Magnetic Field

Particle precipitation and radiation belt in laboratory experiments

Precipitation of particles and how they intrude into the magnetosphere have been investigated in a laboratory experiment. An artificial magnetosphere with a geomagnetic tail has been generated as a result of plasma flow interaction with the field of a magnetic dipole. Two precipitation zones at different latitudes are distinctly observed on the dayside. High-latitude precipitation is associated with plasma intrusion into a polar gap. A low-latitude zone embraces the terrella. Its origin is associated with a radiation belt. Radiation belt filling with particles takes place on the nightside as a result of the convection of force lines into the magnetosphere. It is shown that an equatorial gap originating at the dayside transforms into the plasma sheet in the magnetosphere tail.

Real Gas Effects on Interaction of Shock-Heated Plasma Flows with a Transverse Magnetic Field

Real Gas Effects on Interaction of Shock-Heated Plasma Flows with a Transverse Magnetic Field