scholarly journals Observational support for the electron mirror mode: AMPTE-IRM and Equator-S measurements in the magnetosheath

2018 ◽  
Author(s):  
Rudolf A. Treumann ◽  
Wolfgang Baumjohann
Keyword(s):  
High Temperature ◽  
Collisionless Plasma ◽  
Recent Theory ◽  
Dayside Magnetopause ◽  
Mirror Mode

Abstract. Based on AMPTE-IRM and Equator-S observations in the magnetosheath near the dayside magnetopause, we provide observational support for a recent theory by Noreen et al. (2017) of the contribution of the electron mirror instability to the evolution of mirror modes in the high-temperature anisotropic collisionless plasma of the magnetosheath.

PLT reaches high temperature in a collisionless plasma

Physics Today ◽  
1978 ◽  
Vol 31 (11) ◽  
pp. 17-20
Author(s):  
Gloria B. Lubkin
Keyword(s):  
High Temperature ◽  
Collisionless Plasma

scholarly journals The strange physics of low frequency mirror mode turbulence in the high temperature plasma of the magnetosheath

2004 ◽  
Vol 11 (5/6) ◽  
pp. 647-657 ◽  
Author(s):  
R. A. Treumann ◽  
C. H. Jaroschek ◽  
O. D. Constantinescu ◽  
R. Nakamura ◽  
O. A. Pokhotelov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
High Temperature ◽  
Particle Density ◽  
Convective Transport ◽  
Magnetized Plasma ◽  
Temperature Plasma ◽  
High Temperature Plasma ◽  
Fluid Theory ◽  
Mirror Mode ◽  
The Magnetic Field

Abstract. Mirror mode turbulence is the lowest frequency perpendicular magnetic excitation in magnetized plasma proposed already about half a century ago by Rudakov and Sagdeev (1958) and Chandrasekhar et al. (1958) from fluid theory. Its experimental verification required a relatively long time. It was early recognized that mirror modes for being excited require a transverse pressure (or temperature) anisotropy. In principle mirror modes are some version of slow mode waves. Fluid theory, however, does not give a correct physical picture of the mirror mode. The linear infinitesimally small amplitude physics is described correctly only by including the full kinetic theory and is modified by existing spatial gradients of the plasma parameters which attribute a small finite frequency to the mode. In addition, the mode is propagating only very slowly in plasma such that convective transport is the main cause of flow in it. As the lowest frequency mode it can be expected that mirror modes serve as one of the dominant energy inputs into plasma. This is however true only when the mode grows to large amplitude leaving the linear stage. At such low frequencies, on the other hand, quasilinear theory does not apply as a valid saturation mechanism. Probably the dominant processes are related to the generation of gradients in the plasma which serve as the cause of drift modes thus transferring energy to shorter wavelength propagating waves of higher nonzero frequency. This kind of theory has not yet been developed as it has not yet been understood why mirror modes in spite of their slow growth rate usually are of very large amplitudes indeed of the order of |B/B0|2~O(1). It is thus highly reasonable to assume that mirror modes are instrumental for the development of stationary turbulence in high temperature plasma. Moreover, since the magnetic field in mirror turbulence forms extended though slightly oblique magnetic bottles, low parallel energy particles can be trapped in mirror modes and redistribute energy (cf. for instance, Chisham et al. 1998). Such trapped electrons excite banded whistler wave emission known under the name of lion roars and indicating that the mirror modes contain a trapped particle component while leading to the splitting of particle distributions (see Baumjohann et al., 1999) into trapped and passing particles. The most amazing fact about mirror modes is, however, that they evolve in the practically fully collisionless regime of high temperature plasma where it is on thermodynamic reasons entirely impossible to expel any magnetic field from the plasma. The fact that magnetic fields are indeed locally extracted makes mirror modes similar to "superconducting" structures in matter as known only at extremely low temperatures. Of course, microscopic quantum effects do not play a role in mirror modes. However, it seems that all mirror structures have typical scales of the order of the ion inertial length which implies that mirrors evolve in a regime where the transverse ion and electron motions decouple. In this case the Hall kinetics comes into play. We estimate that in the marginally stationary nonlinear state of the evolution of mirror modes the modes become stretched along the magnetic field with k||=0 and that a small number the order of a few percent of the particle density is responsible only for the screening of the field from the interior of the mirror bubbles.

scholarly journals Electron pairing in mirror modes: surpassing the quasi-linear limit

2019 ◽  
Vol 37 (5) ◽  
pp. 971-988 ◽  
Author(s):  
Rudolf A. Treumann ◽  
Wolfgang Baumjohann
Keyword(s):  
High Temperature ◽  
Sound Waves ◽  
Pressure Balance ◽  
Final State ◽  
Temperature Plasma ◽  
Growth Pressure ◽  
First Case ◽  
Fluid Instability ◽  
Linear Limit ◽  
Mirror Mode

Abstract. The mirror mode evolving in collisionless magnetised high-temperature thermally anisotropic plasmas is shown to develop an interesting macro-state. Starting as a classical zero-frequency ion fluid instability it saturates quasi-linearly at very low magnetic level, while forming elongated magnetic bubbles which trap the electron component to perform an adiabatic bounce motion along the magnetic field. Further evolution of the mirror mode towards a stationary state is determined by the bouncing trapped electrons which interact with the thermal level of ion sound waves and generate attractive wake potentials which give rise to the formation of electron pairs in the lowest-energy singlet state of two combined electrons. Pairing preferentially takes place near the bounce-mirror points where the pairs become spatially locked with all their energy in the gyration. The resulting large anisotropy of pairs enters the mirror growth rate in the quasi-linearly stable mirror mode. It breaks the quasi-linear stability and causes further growth. Pressure balance is either restored by dissipation of the pairs and their anisotropy or inflow of plasma from the environment. In the first case new pairs will continuously form until equilibrium is reached. In the final state the fraction of pairs can be estimated. This process is open to experimental verification. To our knowledge it is the only process in which high-temperature plasma pairing may occur and has an important observable macroscopic effect: breaking the quasi-linear limit and, via pressure balance, generation of localised diamagnetism.

scholarly journals Mirror mode physics: Amplitude limit

2019 ◽  
Author(s):  
Rudolf A. Treumann ◽  
Wolfgang Baumjohann
Keyword(s):  
Magnetic Field ◽  
High Temperature ◽  
Dominant Role ◽  
Sound Waves ◽  
Final State ◽  
Temperature Plasma ◽  
Electron Pairs ◽  
Mirror Mode ◽  
Spacecraft Data ◽  
The Magnetic Field

Abstract. The mirror mode evolving in collisionless magnetised high-temperature thermally anisotropic plasmas is shown to resemble a macro-quantum state. Starting as a classical zero frequency ion fluid instability it saturates quasi-linearly at very low magnetic level, while forming extended magnetic bubbles.It traps the electron component into an adiabatic bounce motion along the magnetic field which causes a bulk electron anisotropy. This can drive an electron mirror mode (see Treumann and Baumjohann, 2018b, who identified it in old spacecraft data). More important, however, we show that trapped electrons play the dominant role of further evolution towards a stationary state. Interaction of the trapped bouncing electrons with the thermal level of ion sound waves causes attractive potentials between electrons and forms electron pairs in the lowest-energy singlet state of two combined electrons. This happens preferentially near the electron mirror points resulting in a diamagnetic current effect which ultimately drives evolution of the magnetic field into large amplitude mirror bubbles causing diamagnetism and expelling a larger fraction of magnetic flux from the interior of the initial quasi-linearly stable mirror mode bottle. Estimates given in view of mirror modes in the magnetosheath are in reasonable numerical agreement with observation. We derive the self-consistent final state of the mirror bubbles. This analysis demonstrates that the observed mirror mode in high temperature space plasmas (solar wind, magnetosheath, magnetotail) is not a simple magnetohydrodynamic instability. It resembles a classical super-conducting, super-fluid state in high temperature plasma under conditions when electron pairs form. This is a most interesting observation which suggests that pair formation can become relevant in space and astrophysics.

scholarly journals High-pressure phase diagrams of FeSe1−xTex: correlation between suppressed nematicity and enhanced superconductivity

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
K. Mukasa ◽  
K. Matsuura ◽  
M. Qiu ◽  
M. Saito ◽  
Y. Sugimura ◽  
...  
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Phase Diagrams ◽  
High Temperature Superconductivity ◽  
High Pressure Phase ◽  
Recent Theory ◽  
Magnetic Fluctuations ◽  
End Point ◽  
Enhanced Superconductivity ◽  
Pressure Phase

AbstractThe interplay among magnetism, electronic nematicity, and superconductivity is the key issue in strongly correlated materials including iron-based, cuprate, and heavy-fermion superconductors. Magnetic fluctuations have been widely discussed as a pairing mechanism of unconventional superconductivity, but recent theory predicts that quantum fluctuations of nematic order may also promote high-temperature superconductivity. This has been studied in FeSe1−xSx superconductors exhibiting nonmagnetic nematic and pressure-induced antiferromagnetic orders, but its abrupt suppression of superconductivity at the nematic end point leaves the nematic-fluctuation driven superconductivity unconfirmed. Here we report on systematic studies of high-pressure phase diagrams up to 8 GPa in high-quality single crystals of FeSe1−xTex. When Te composition x(Te) becomes larger than 0.1, the high-pressure magnetic order disappears, whereas the pressure-induced superconducting dome near the nematic end point is continuously found up to x(Te) ≈ 0.5. In contrast to FeSe1−xSx, enhanced superconductivity in FeSe1−xTex does not correlate with magnetism but with the suppression of nematicity, highlighting the paramount role of nonmagnetic nematic fluctuations for high-temperature superconductivity in this system.

scholarly journals Condensate Formation in Collisionless Plasma

2021 ◽  
Vol 9 ◽  
Author(s):  
R. A. Treumann ◽  
Wolfgang Baumjohann
Keyword(s):  
High Temperature ◽  
Background Noise ◽  
Collisionless Plasma ◽  
Debye Length ◽  
Magnetic Mirror ◽  
Perpendicular Direction ◽  
Correlation Lengths ◽  
Ion Acoustic ◽  
Condensate Formation ◽  
Parallel Direction

Particle condensates in general magnetic mirror geometries in high-temperature plasmas may be caused by a discrete resonance with thermal ion-acoustic background noise near mirror points. The resonance breaks the bounce symmetry, temporally locking the particles to the resonant wavelength. The relevant correlation lengths are the Debye length in the parallel direction and the ion gyroradius in the perpendicular direction.

scholarly journals Mirror Mode Junctions as Sources of Radiation

2021 ◽  
Vol 8 ◽  
Author(s):  
R. A. Treumann ◽  
Wolfgang Baumjohann
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Electromagnetic Radiation ◽  
Superconducting State ◽  
Infrared Range ◽  
Ginzburg Landau ◽  
Discrete Particle ◽  
Mirror Mode ◽  
Particle Resonance

Mirror modes in collisionless high-temperature plasmas represent macroscopic high-temperature quasi-superconductors with bouncing electrons in discrete-particle resonance with thermal ion-sound noise contributing to the ion-mode growth beyond quasilinear stability. In the semi-classical Ginzburg-Landau approximation the conditions for phase transition are reviewed. The quasi-superconducting state is of second kind causing a magnetically perforated plasma texture. Focussing on the interaction of mirror bubbles we apply semi-classical Josephson conditions and show that a mirror perforated plasma emits weak electromagnetic radiation which in the magnetosheath should be in the sub-millimeter, respectively, infrared range. This effect might be of astrophysical importance.

Time-fractional study of electron acoustic solitary waves in plasma of cold electron and two isothermal ions

2012 ◽  
Vol 78 (6) ◽  
pp. 641-649 ◽  
Author(s):  
S. A. EL-WAKIL ◽  
ESSAM M. ABULWAFA ◽  
EMAD K. EL-SHEWY ◽  
ABEER A. MAHMOUD
Keyword(s):  
High Temperature ◽  
Collisionless Plasma ◽  
Variational Iteration Method ◽  
Homogeneous System ◽  
Cold Electron ◽  
Type Distribution ◽  
Thermal Distribution ◽  
Noise Type ◽  
Solitary Pulse ◽  
Electron Acoustic

AbstractIn this paper, a homogeneous system of unmagnetized collisionless plasma consisting of a cold electron fluid, low-temperature ion obeying Boltzmann-type distribution and high-temperature ion obeying non-thermal distribution is considered. The perturbation method with two different forms of stretching will be considered to drive the KdV and modified KdV (mKdV) equations. The Agrawal's method is applied to formulate the time-fractional KdV and mKdV equations. A variational iteration method is used to solve these equations. The results show that the fractional order of the differential equations can be used to modify the shape of the solitary pulse instead of adding higher order dissipation terms to the equations. This study may be useful to construct the compressive and rarefactive electrostatic potential pulses associated with the broadband electrostatic noise type emissions.

scholarly journals Electron mirror branch: observational evidence from “historical” AMPTE-IRM and Equator-S measurements

2018 ◽  
Vol 36 (6) ◽  
pp. 1563-1576 ◽  
Author(s):  
Rudolf A. Treumann ◽  
Wolfgang Baumjohann
Keyword(s):  
Collisionless Plasma ◽  
Low Frequency ◽  
Small Population ◽  
Observational Evidence ◽  
Bulk Temperature ◽  
Temperature Anisotropy ◽  
Pressure Balance ◽  
Theoretical Evaluation ◽  
Separate Electron ◽  
Mirror Mode

Abstract. Based on now “historical” magnetic observations, supported by few available plasma data, and wave spectra from the AMPTE-IRM spacecraft, and also on “historical” Equator-S high-cadence magnetic field observations of mirror modes in the magnetosheath near the dayside magnetopause, we present observational evidence for a recent theoretical evaluation by Noreen et al. (2017) of the contribution of a global (bulk) electron temperature anisotropy to the evolution of mirror modes, giving rise to a separate electron mirror branch. We also refer to related low-frequency lion roars (whistlers) excited by the trapped resonant electron component in the high-temperature anisotropic collisionless plasma of the magnetosheath. These old data most probably indicate that signatures of the anisotropic electron effect on mirror modes had indeed already been observed long ago in magnetic and wave data, though they had not been recognised as such. Unfortunately either poor time resolution or complete lack of plasma data would have inhibited the confirmation of the required pressure balance in the electron branch for unambiguous confirmation of a separate electron mirror mode. If confirmed by future high-resolution observations (like those provided by the MMS mission), in both cases the large mirror mode amplitudes suggest that mirror modes escape quasilinear saturation, being in a state of weak kinetic plasma turbulence. As a side product, this casts as erroneous the frequent claim that the excitation of lion roars (whistlers) would eventually saturate the mirror instability by depleting the bulk temperature anisotropy. Whistlers, excited in mirror modes, just flatten the anisotropy of the small population of resonant electrons responsible for them, without having any effect on the global electron-pressure anisotropy, which causes the electron branch and by no means at all on the ion-mirror instability. For the confirmation of both the electron mirror branch and its responsibility for trapping of electrons and resonantly exciting high-frequency whistlers, also known as lion roars, high time- and energy-resolution observations of electrons (as provided for instance by MMS) are required.

The bottleneck may be the solution, not the problem

2016 ◽  
Vol 39 ◽  
Author(s):  
Arnon Lotem ◽  
Oren Kolodny ◽  
Joseph Y. Halpern ◽  
Luca Onnis ◽  
Shimon Edelman
Keyword(s):  
Working Memory ◽  
Language Acquisition ◽  
Recent Theory ◽  
Cognitive Mechanisms ◽  
Selection Pressures ◽  
Biological Trait ◽  
Memory Bottleneck

AbstractAs a highly consequential biological trait, a memory “bottleneck” cannot escape selection pressures. It must therefore co-evolve with other cognitive mechanisms rather than act as an independent constraint. Recent theory and an implemented model of language acquisition suggest that a limit on working memory may evolve to help learning. Furthermore, it need not hamper the use of language for communication.

Sign in / Sign up

Export Citation Format

Share Document