The Experts below are selected from a list of 165 Experts worldwide ranked by ideXlab platform
Frank Verheest - One of the best experts on this subject based on the ideXlab platform.
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electrostatic supersolitons and double layers at the Acoustic Speed
Physics of Plasmas, 2015Co-Authors: Frank Verheest, Manfred A HellbergAbstract:Supersolitons are characterized by subsidiary extrema on the sides of a typical bipolar electric field signature or by association with a root beyond double layers in the fully nonlinear Sagdeev pseudopotential description. It has been proven that supersolitons may exist in several plasmas having at least three constituent species, but they cannot be found in weakly nonlinear theory. Another recent aspect of pseudopotential theory is that in certain plasma models and parameter regimes solitons and/or double layers can exist at the Acoustic Speed, having no reductive perturbation counterparts. Importantly, they signal coexistence between solitons having positive and negative polarity, in that one solution can be realized at a time, depending on infinitesimal perturbations from the equilibrium state. Weaving the two strands together, we demonstrate here that one can even find supersolitons and double layers at the Acoustic Speed, as illustrated using the model of cold positive and negative ions, in the presence of nonthermal electrons following a Cairns distribution. This model has been discussed before, but the existence and properties of supersolitons at the Acoustic Speed were not established at the time of publication.
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new light on ion Acoustic solitary waves in a plasma with two temperature electrons
EPL, 2010Co-Authors: Frank Verheest, Manfred A Hellberg, T K BalukuAbstract:Ion Acoustic solitary waves in two-temperature electron plasmas have been studied in the past, and negative-potential solitons and double layers found, in addition to positive-potential solitons. Here, further investigations show that positive-potential double layers can form below a critical density ratio, associated with the third derivative of the Sagdeev potential evaluated at the origin for the phase velocity of the linear wave. For density ratios that support positive double layers, solitons are also reported beyond the double layers, depending on the cool-to-hot electron temperature ratio. In addition, when both polarities can be supported, solitary structures can propagate at the Acoustic Speed, contrary to a KdV prescription.
Manfred A Hellberg - One of the best experts on this subject based on the ideXlab platform.
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electrostatic supersolitons and double layers at the Acoustic Speed
Physics of Plasmas, 2015Co-Authors: Frank Verheest, Manfred A HellbergAbstract:Supersolitons are characterized by subsidiary extrema on the sides of a typical bipolar electric field signature or by association with a root beyond double layers in the fully nonlinear Sagdeev pseudopotential description. It has been proven that supersolitons may exist in several plasmas having at least three constituent species, but they cannot be found in weakly nonlinear theory. Another recent aspect of pseudopotential theory is that in certain plasma models and parameter regimes solitons and/or double layers can exist at the Acoustic Speed, having no reductive perturbation counterparts. Importantly, they signal coexistence between solitons having positive and negative polarity, in that one solution can be realized at a time, depending on infinitesimal perturbations from the equilibrium state. Weaving the two strands together, we demonstrate here that one can even find supersolitons and double layers at the Acoustic Speed, as illustrated using the model of cold positive and negative ions, in the presence of nonthermal electrons following a Cairns distribution. This model has been discussed before, but the existence and properties of supersolitons at the Acoustic Speed were not established at the time of publication.
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ion Acoustic solitary waves in an electron positron ion plasma with non thermal electrons
Plasma Physics and Controlled Fusion, 2011Co-Authors: T K Baluku, Manfred A HellbergAbstract:Using the Sagdeev potential approach, arbitrary amplitude modified ion Acoustic solitons and double layers have been studied in an electron–positron–ion (e–p–i) plasma composed of Cairns-distributed electrons, Boltzmann positrons and cold ions. Existence domains are presented in different slices of parameter space, and care is taken to differentiate between behaviour at a fixed soliton Speed, and at the Mach number normalized with respect to the true Acoustic Speed for the three-component plasma. Negative solitons, limited in Mach number by double layers, have been found over small ranges in β, relative positron density and Mach number. These have not previously been reported in an e–p–i plasma. A region of 'coexistence' in parameter space has been identified, in which solitons of both polarities are supported. In this region, one polarity behaves in a 'Korteweg–de Vries (KdV)-like' fashion, vanishing at the Acoustic Speed, while solitons of the other polarity have finite amplitude at the Acoustic Speed ('non-KdV-like'), as has been reported recently in a number of other plasma models. This work extends considerably and also corrects some errors in a recent publication (Pakzad 2009 Phys. Lett. A 373 847–50).
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new light on ion Acoustic solitary waves in a plasma with two temperature electrons
EPL, 2010Co-Authors: Frank Verheest, Manfred A Hellberg, T K BalukuAbstract:Ion Acoustic solitary waves in two-temperature electron plasmas have been studied in the past, and negative-potential solitons and double layers found, in addition to positive-potential solitons. Here, further investigations show that positive-potential double layers can form below a critical density ratio, associated with the third derivative of the Sagdeev potential evaluated at the origin for the phase velocity of the linear wave. For density ratios that support positive double layers, solitons are also reported beyond the double layers, depending on the cool-to-hot electron temperature ratio. In addition, when both polarities can be supported, solitary structures can propagate at the Acoustic Speed, contrary to a KdV prescription.
S D Bale - One of the best experts on this subject based on the ideXlab platform.
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electrostatic solitary waves in the earth s bow shock nature properties lifetimes and origin
arXiv: Space Physics, 2021Co-Authors: R Wang, F S Mozer, S D Bale, I Y Vasko, Ilya Kuzichev, A V Artemyev, Mms TeamAbstract:We present a statistical analysis of more than two thousand bipolar electrostatic solitary waves (ESW) collected from ten quasi-perpendicular Earth's bow shock crossings by Magnetospheric Multiscale spacecraft. We developed and implemented a correction procedure for reconstruction of actual electric fields, velocities, and other properties of ESW from measurements, whose spatial scales are typically comparable with or smaller than spatial distance between voltage-sensitive probes. We determined the optimal ratio between frequency response factors of axial and spin plane antennas to be around 1.65/1.8. We found that more than 95\% of the ESW in the Earth's bow shock are of negative polarity and present an in depth analysis of properties of these ESW. They have spatial scales of about 10--100 m that is within a range of $\lambda_{D}$ to $10\lambda_{D}$, amplitudes typically below a few Volts that is below 0.1 of local electron temperature, and velocities below a few hundreds km/s in spacecraft and plasma rest frames that is on the order of local ion-Acoustic Speed. The spatial scales of ESW are distinctly correlated with local Debye length $\lambda_{D}$. ESW with amplitudes of 5--30 V or 0.1--0.3 Te have the occurrence rate of a few percent. The ESW have electric fields generally oblique to local magnetic field and propagate highly oblique to shock normal ${\bf N}$; more than 80\% of ESW propagate within 30$^{\circ}$ of the shock plane. In the shock plane, ESW typically propagate within a few tens of degrees of local magnetic field projection ${\bf B}_{\rm LM}$ onto the shock plane and preferentially opposite to ${\bf N}\times {\bf B}_{\rm LM}$. We argue that the ESW of negative polarity are ion phase space holes produced in a nonlinear stage of ion-ion ion-streaming instabilities. We estimated lifetimes of the ion holes to be 10--100 ms, or 1--10 km in terms of spatial distance.
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megavolt parallel potentials arising from double layer streams in the earth s outer radiation belt
Physical Review Letters, 2013Co-Authors: F S Mozer, S D Bale, J W Bonnell, C C Chaston, I Roth, J R WygantAbstract:Huge numbers of double layers carrying electric fields parallel to the local magnetic field line have been observed on the Van Allen probes in connection with in situ relativistic electron acceleration in the Earth's outer radiation belt. For one case with adequate high time resolution data, 7000 double layers were observed in an interval of 1 min to produce a 230,000 V net parallel potential drop crossing the spacecraft. Lower resolution data show that this event lasted for 6 min and that more than 1,000,000 volts of net parallel potential crossed the spacecraft during this time. A double layer traverses the length of a magnetic field line in about 15 s and the orbital motion of the spacecraft perpendicular to the magnetic field was about 700 km during this 6 min interval. Thus, the instantaneous parallel potential along a single magnetic field line was the order of tens of kilovolts. Electrons on the field line might experience many such potential steps in their lifetimes to accelerate them to energies where they serve as the seed population for relativistic acceleration by coherent, large amplitude whistler mode waves. Because the double-layer Speed of 3100 km/s is the order of the electron Acoustic Speed (and not the ion Acoustic Speed) of a 25 eV plasma, the double layers may result from a new electron Acoustic mode. Acceleration mechanisms involving double layers may also be important in planetary radiation belts such as Jupiter, Saturn, Uranus, and Neptune, in the solar corona during flares, and in astrophysical objects.
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large amplitude electrostatic waves associated with magnetic ramp substructure at earth s bow shock
Geophysical Research Letters, 2006Co-Authors: A J Hull, F S Mozer, D E Larson, M Wilber, J D Scudder, C T Russell, S D BaleAbstract:[1] We present Polar observations of high frequency (100 Hz ≤ f ≤ 4000 Hz) electrostatic (ES) waves at Earth's bow shock under extreme solar wind conditions. Although solitary waves are observed, the most prevalent structures in the magnetic ramp are coherent, large-amplitude (up to 80 mV/m) ES wave packets, which last 10-30 cycles, and propagate at varied obliquities relative to the magnetic field. The ES wave power is well correlated with maxima in the magnetic ramp substructure, suggesting that these maxima are important source regions. Detailed interferometric based analysis of waveforms show that they have wavelengths of a few hundred meters (e.g., ∼20λ D ∼ 0.5 ρe ) and phase Speeds at the Acoustic Speed, suggesting that they are ion Acoustic waves (IAW)s. The IAWs, having potentials ≤ 1V with no net change, are not likely to affect bulk plasma energization, though they may scatter the plasma and thus affect plasma thermalization.
T K Baluku - One of the best experts on this subject based on the ideXlab platform.
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ion Acoustic solitary waves in an electron positron ion plasma with non thermal electrons
Plasma Physics and Controlled Fusion, 2011Co-Authors: T K Baluku, Manfred A HellbergAbstract:Using the Sagdeev potential approach, arbitrary amplitude modified ion Acoustic solitons and double layers have been studied in an electron–positron–ion (e–p–i) plasma composed of Cairns-distributed electrons, Boltzmann positrons and cold ions. Existence domains are presented in different slices of parameter space, and care is taken to differentiate between behaviour at a fixed soliton Speed, and at the Mach number normalized with respect to the true Acoustic Speed for the three-component plasma. Negative solitons, limited in Mach number by double layers, have been found over small ranges in β, relative positron density and Mach number. These have not previously been reported in an e–p–i plasma. A region of 'coexistence' in parameter space has been identified, in which solitons of both polarities are supported. In this region, one polarity behaves in a 'Korteweg–de Vries (KdV)-like' fashion, vanishing at the Acoustic Speed, while solitons of the other polarity have finite amplitude at the Acoustic Speed ('non-KdV-like'), as has been reported recently in a number of other plasma models. This work extends considerably and also corrects some errors in a recent publication (Pakzad 2009 Phys. Lett. A 373 847–50).
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new light on ion Acoustic solitary waves in a plasma with two temperature electrons
EPL, 2010Co-Authors: Frank Verheest, Manfred A Hellberg, T K BalukuAbstract:Ion Acoustic solitary waves in two-temperature electron plasmas have been studied in the past, and negative-potential solitons and double layers found, in addition to positive-potential solitons. Here, further investigations show that positive-potential double layers can form below a critical density ratio, associated with the third derivative of the Sagdeev potential evaluated at the origin for the phase velocity of the linear wave. For density ratios that support positive double layers, solitons are also reported beyond the double layers, depending on the cool-to-hot electron temperature ratio. In addition, when both polarities can be supported, solitary structures can propagate at the Acoustic Speed, contrary to a KdV prescription.
P K Shukla - One of the best experts on this subject based on the ideXlab platform.
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dust Acoustic solitary waves in a quantum plasma
Physics of Plasmas, 2006Co-Authors: S Ali, P K ShuklaAbstract:By employing one-dimensional quantum hydrodynamic (QHD) model for a three species quantum plasma, nonlinear properties of dust Acoustic solitary waves are studied. For this purpose a Korteweg-de Vries (KdV) equation is derived, incorporating quantum corrections. The quantum mechanical effects are also examined numerically both on the profiles of the amplitude and the width of dust Acoustic solitary waves. It is found that the amplitude remains constant but the width shrinks for different values of a dimensionless electron quantum parameter He=(Zd0ℏ2ωpd2)∕memdCd4, where Zd0 is the dust charge state, ℏ is the Planck constant divided by 2π, ωpd is the dust plasma frequency, me (md) is the electron (dust) mass, and Cd is the dust Acoustic Speed.
