Transition layer between two magnetized plasmas

1979 ◽  
Vol 22 (3) ◽  
pp. 515-524 ◽  
Author(s):  
L. C. Lee ◽  
J. R. Kan
Keyword(s):  
Electron Temperature ◽  
Flow Velocity ◽  
Transition Layer ◽  
Potential Difference ◽  
Current Layer ◽  
Ion Temperature ◽  
Kinetic Formulation ◽  
Two Sides ◽  
Relative Flow ◽  
Asymptotic Potential

Structures of the current layer between two magnetized anisothermal plasmas are studied on the basis of a kinetic formulation. It is shown that the structure of the current layer is dominantly controlled by the hotter species of the plasmas. The thickness is characterized by the ion gyroradius if the ion temperature is much greater than the electron temperature. The structure is, in general, insensitive to the asymptotic potential difference and the relative flow velocity between plasmas on the two sides.

Effect of the relative flow velocity on the structure and stability of the magnetopause current layer

1994 ◽  
Vol 99 (A3) ◽  
pp. 4095 ◽  
Author(s):  
M. M. Kuznetsova ◽  
M. Roth ◽  
Z. Wang ◽  
M. Ashour-Abdalla
Keyword(s):  
Flow Velocity ◽  
Current Layer ◽  
Structure And Stability ◽  
Relative Flow

Coherence-imaging spectroscopy for 2D distribution of ion temperature and flow velocity in a laboratory magnetosphere

2018 ◽  
Vol 89 (10) ◽  
pp. 10D133 ◽  
Author(s):  
K. Nakamura ◽  
M. Nishiura ◽  
N. Takahashi ◽  
Z. Yoshida ◽  
N. Kenmochi ◽  
...  
Keyword(s):  
Flow Velocity ◽  
Imaging Spectroscopy ◽  
Ion Temperature ◽  
Coherence Imaging

scholarly journals Two-temperature magnetohydrodynamic simulations for sub-relativistic active galactic nucleus jets: dependence on the fraction of the electron heating

2020 ◽  
Vol 493 (4) ◽  
pp. 5761-5772 ◽  
Author(s):  
Takumi Ohmura ◽  
Mami Machida ◽  
Kenji Nakamura ◽  
Yuki Kudoh ◽  
Ryoji Matsumoto
Keyword(s):  
Electron Temperature ◽  
X Rays ◽  
Ion Temperature ◽  
Temperature Plasma ◽  
Electron Heating ◽  
Coulomb Collisions ◽  
X Ray ◽  
Jet Plasma ◽  
Magnetohydrodynamic Simulations ◽  
Two Temperature

ABSTRACT We present the results of two-temperature magnetohydrodynamic simulations of the propagation of sub-relativistic jets of active galactic nuclei. The dependence of the electron and ion temperature distributions on the fraction of electron heating, fe, at the shock front is studied for fe = 0, 0.05, and 0.2. Numerical results indicate that in sub-relativistic, rarefied jets, the jet plasma crossing the terminal shock forms a hot, two-temperature plasma in which the ion temperature is higher than the electron temperature. The two-temperature plasma expands and forms a backflow referred to as a cocoon, in which the ion temperature remains higher than the electron temperature for longer than 100 Myr. Electrons in the cocoon are continuously heated by ions through Coulomb collisions, and the electron temperature thus remains at Te > 109 K in the cocoon. X-ray emissions from the cocoon are weak because the electron number density is low. Meanwhile, X-rays are emitted from the shocked intracluster medium (ICM) surrounding the cocoon. Mixing of the jet plasma and the shocked ICM through the Kelvin–Helmholtz instability at the interface enhances X-ray emissions around the contact discontinuity between the cocoon and shocked ICM.

scholarly journals Velocity shear and current driven instability in a collisional F-region

2009 ◽  
Vol 27 (1) ◽  
pp. 381-394 ◽  
Author(s):  
P. J. G. Perron ◽  
J.-M. A. Noël ◽  
J.-P. St.-Maurice
Keyword(s):  
Dispersion Relation ◽  
Electron Temperature ◽  
Current Density ◽  
Threshold Current ◽  
Velocity Shear ◽  
Ion Temperature ◽  
Fluid Limit ◽  
Low Frequencies ◽  
F Region ◽  
Threshold Conditions

Abstract. We have studied how the presence of collisions affects the behavior of instabilities triggered by a combination of shears and parallel currents in the ionosphere under a variety of ion to electron temperature ratios. To this goal we have numerically solved a kinetic dispersion relation, using a relaxation model to describe the effects of ion and electron collisions. We have compared our solutions to expressions derived in a fluid limit which applied only to large electron to ion temperature ratios. We have limited our study to threshold conditions for the current density and the shears. We have studied how the threshold varies as a function of the wave-vector angle direction and as a function of frequency. As expected, we have found that for low frequencies and/or elevated ion to electron temperature ratios, the kinetic dispersion relation has to be used to evaluate the threshold conditions. We have also found that ion velocity shears can significantly lower the field-aligned threshold current needed to trigger the instability, especially for wave-vectors close to the perpendicular to the magnetic field. However the current density and shear requirements remain significantly higher than if collisions are neglected. Therefore, for ionospheric F-region applications, the effect of collisions should be included in the calculation of instabilities associated with horizontal shears in the vertical flow. Furthermore, in many situations of interest the kinetic solutions should be used instead of the fluid limit, in spite of the fact that the latter can be shown to produce qualitatively valid solutions.

scholarly journals Kinetic infernal modes for Wendelstein 7-X-like -profiles

2019 ◽  
Vol 85 (6) ◽  
Author(s):  
Alessandro Zocco ◽  
Alexey Mishchenko ◽  
Axel Könies
Keyword(s):  
Electron Temperature ◽  
High Performance ◽  
Ion Temperature ◽  
Electron Temperature Gradient ◽  
Average Value ◽  
Toroidal Plasma ◽  
Rotational Transform ◽  
Ideal Magnetohydrodynamic ◽  
The One ◽  
Sawtooth Oscillations

We show analytically that for $\unicode[STIX]{x1D704}$ -profiles similar to the one of the Wendelstein 7-X stellarator, where $\unicode[STIX]{x1D704}$ is the rotational transform of the equilibrium magnetic field, a highly conducting toroidal plasma is unstable to kinetically mediated pressure-driven long-wavelength reconnecting modes, of the infernal type. The modes are destabilized either by the electron temperature gradient or by a small amount of current, depending on how far from unity the average value of $\unicode[STIX]{x1D704}$ is, which is assumed to be slowly varying. We argue that, for W7-X, a broad mode with toroidal and poloidal mode numbers $(n,m)=(1,1)$ can be destabilized due to the strong geometric side-band coupling of the resonant kinetic electron response at locations where $\unicode[STIX]{x1D704}$ is rational for harmonics that belong to the mode family of the $(n,m)=(1,1)$ mode itself. In many regimes, the growth rate is insensitive to the plasma density, thus it is likely to persist in high performance W7-X discharges. For a peaked electron temperature, with a maximum of $T_{e}=5~\text{keV}$ , larger than the ion temperature, $T_{i}=2.5~\text{keV}$ , and a density $n_{0}=10^{19}~\text{m}^{-3}$ , instability is found in regimes which show plasma sawtooth activity, with growth rates of the order of tens of kiloHertz. Frequencies are either electron diamagnetic or of the ideal magnetohydrodynamic type, but sub-Alfvénic. The kinetic infernal mode is thus a good candidate for the explanation of sawtooth oscillations in present-day stellarators and poses a new challenge to the problem of stellarator reactor optimization.

New low-frequency waves and negative mass instability in dusty plasmas

2010 ◽  
Vol 76 (6) ◽  
pp. 929-937
Author(s):  
D. P. RESENDES ◽  
R. BINGHAM ◽  
S. MOTA ◽  
V. N. TSYTOVICH
Keyword(s):  
Electron Temperature ◽  
Free Path ◽  
Collision Frequency ◽  
Low Frequency ◽  
Mean Free Path ◽  
Sound Waves ◽  
Ion Temperature ◽  
Plasma Particle ◽  
Charging Mode ◽  
Dust Charging

AbstractLow-frequency dusty plasma waves with frequencies much smaller than the frequency of charging collisions of plasma particles with dust particles are considered taking into account elastic and charging collisions of plasma particles with dust and neutrals. The usual dust sound waves with an upper frequency equal to the dust plasma frequency are found to be present only for wavelengths much smaller than the plasma particle effective mean free path due to the effective collision frequency. The effectice collision frequency is found to be inversely proportional to the square root of the product of the charging frequency and the frequency of particle momentum losses, involving processes due to elastic plasma particle–dust collisions and collisions with neutrals. It is shown that when the wavelength of the wave is much larger than the mean free path for effective collisions, the properties of the waves are different from those considered previously. A negative mass instability is found in this domain of frequencies when the effective mean free path of ions is larger than the effective mean free path of electrons. In the absence of neutrals, this appears to be possible only if the temperature of ions exceeds the electron temperature. This can occur in laboratory experiments and space plasmas but not in plasma-etching experiments. In the absence of instability, a new dust oscillation, a dust charging mode, is found, whose frequency is almost constant over a certain range of wave numbers. It is inversely proportional to the dust mass and charging frequency of the dust. A new dust electron sound wave is found for frequencies less than the frequency of the dust charging mode. The velocity of the dust electron sound wave is determined by the electron temperature but not the ion temperature, as for the usual dust sound waves, with the electron temperature substantially exceeding the ion temperature.

scholarly journals The effect of electron bite-outs on artificial electron heating and the PMSE overshoot

2005 ◽  
Vol 23 (12) ◽  
pp. 3633-3643 ◽  
Author(s):  
M. Kassa ◽  
O. Havnes ◽  
E. Belova
Keyword(s):  
Electron Temperature ◽  
Electron Density ◽  
Electron Density Profile ◽  
Dust Particles ◽  
High Electron ◽  
Heating Effect ◽  
Ion Temperature ◽  
Degree Of Ionization ◽  
Electron Heating ◽  
Transmitter Power

Abstract. We have considered the effect that a local reduction in the electron density (an electron bite-out), caused by electron absorption on to dust particles, can have on the artificial electron heating in the height region between 80 to 90km, where noctilucent clouds (NLC) and the radar phenomenon PMSE (Polar Mesospheric Summer Echoes) are observed. With an electron density profile without bite-outs, the heated electron temperature Te,hot will generally decrease smoothly with height in the PMSE region or there may be no significant heating effect present. Within a bite-out Te,hot will decrease less rapidly and can even increase slightly with height if the bite-out is strong. We have looked at recent observations of PMSE which are affected by artificial electron heating, with a heater cycling producing the new overshoot effect. According to the theory for the PMSE overshoot the fractional increase in electron temperature Te,hot/Ti, where Ti is the unaffected ion temperature=neutral temperature, can be found from the reduction in PMSE intensity as the heater is switched on. We have looked at results from four days of observations with the EISCAT VHF radar (224 MHz), together with the EISCAT heating facility. We find support for the PMSE overshoot and heating model from a sequence of observations during one of the days where the heater transmitter power is varied from cycle to cycle and where the calculated Te,hot/Ti is found to vary in proportion to the transmitter power. We also looked for signatures of electron bite-outs by examining the variation of Te,hot/Ti with height for the three other days. We find that the height variation of Te,hot/Ti is very different on the three days. On one of the days we see typically that this ratio can increase with height, showing the presence of a bite-out, while on the next day the heating factor mainly decreases with height, indicating that the fractional amount of dust is low, so that the electron density is hardly affected by it. On the third day there is little heating effect on the PMSE layer. This is probably due to a sufficiently high electron density in the atmosphere below the PMSE layer, so that the transmitted heater power is absorbed in these lower layers. On this day the D-region, as given by the UHF (933MHz) observations, extends deeper down in the atmosphere than on the other two days, indicating that the degree of ionization in and below the PMSE layers is higher as well.

scholarly journals Spotty appearance of the solar disk as inferred from the comparaison between EUV and radio intensities

1965 ◽  
Vol 23 ◽  
pp. 109-114
Author(s):  
Z. Suemoto ◽  
F. Moriyama
Keyword(s):  
Electron Temperature ◽  
Transition Layer ◽  
Solar Disk ◽  
Sunspot Minimum ◽  
Line Intensities ◽  
Inhomogeneous Model ◽  
First Approximation

This is a revised version of the work reported to the COSPAR Symposium of 1962. In the first place, the basic components of the radio intensities ranging from 1000 MHz to 9400 MHz derived by H. Tanaka were used to establish the relation between the electron temperature and integrated number of electrons for 1960 and 1961 flights. The result justifies our former assumption that the radio intensities with which the EUV line intensities from the transition layer are to be compared should, as a first approximation, be very close to those at sunspot minimum.In the second place, the integrated numbers of electrons from the EUV line intensities were derived based on the same data as were used by Pottasch. This is to eliminate any arbitrariness in adopting parameters which are still uncertain.The result is that we still have a large amount of disagreement between the two sets of intensities in the sense that EUV line intensities are at least ten times stronger as might be inferred from the radio intensities. If one assumes an inhomogeneous model in which the solar disk is bright only in patches covering about 0.15 of its total area, the discrepancy would be eliminated.

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