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NASA NTRS1999

Whistler Solitons in Plasma with Anisotropic Hot Electron Admixture

The longitudinal and transverse modulation instability of whistler waves in plasma, with a small admixture of hot anisotropic electrons, is discussed. If the hot particles temperature anisotropy is positive, it is found that, in such plasma, longitudinal perturbations can lead to soliton formation for frequencies forbidden in cold plasma. The soliton is enriched by hot particles. The frequency region unstable to transverse modulation in cold plasma in the presence of hot electrons is divided by stable domains. For both cases the role of hot electrons is more significant for whistlers with smaller frequencies.

Khazanov, G. V.↗

NASA NTRS1999

Whistler Solitons in Plasma with Anisotropic Hot Electron Admixture

Khazanov, G. V.↗

NASA NTRS2012

Phase Coupling Between Spectral Components of Collapsing Langmuir Solitons in Solar Type III Radio Bursts

We present the high time resolution observations of one of the Langmuir wave packets obtained in the source region of a solar type III radio burst. This wave packet satisfies the threshold condition of the supersonic modulational instability, as well as the criterion of a collapsing Langmuir soliton, i.e., the spatial scale derived from its peak intensity is less than that derived from its short time scale. The spectrum of t his wave packet contains an intense spectral peak at local electron plasma frequency, f(sub pe) and relatively weaker peaks at 2f(sub pe) and 3f(sub pe). We apply the wavelet based bispectral analysis technique on this wave packet and compute the bicoherence between its spectral components. It is found that the bicoherence exhibits two peaks at (approximately f(sub pe), approximately f(sub pe)) and (approximately f(sub pe) approximately 2f(sub pe)), which strongly suggest that the spectral peak at 2f(sub pe) probably corresponds to the second harmonic radio emission, generated as a result of the merging of antiparallel propagating Langmuir waves trapped in the collapsing Langmuir soliton, and, the spectral peak at 3f(sub pe) probably corresponds to the third harmonic radio emission, generated as a result of merging of a trapped Langmuir wave and a second harmonic electromagnetic wave.

Thejappa, G.↗

NASA NTRS1999

The Existence of Optical Solitons on Wavelength Division Multiplexed Beams in a Nonlinear Fiber

Simple analytic expression for the initial fundamental optical solitons on wavelength division multiplexed (WDM) beams in a nonlinear fiber has been found.

multiplexed beams nonlinear fibers optical soliton↗

NASA NTRS1976

Pseudopotentials of Estabrook and Wahlquist, the geometry of solitons, and the theory of connections

The prolongation structure of Wahlquist and Estabrook is interpreted as a connection. In this way, some geometric insight might be provided for the description of those nonlinear partial differential equations which admit soliton solutions. A new geometric property - linked to the existence of an SL(2,R) connection - is proved for the solutions of the Korteweg-de Vries equation.

Hermann, R.↗

NASA NTRS1982

Solitons and ionospheric heating

It is noted that for parameters characterizing the Platteville ionospheric heating facility, the Langmuir wave evolution at the exact reflection point of the heater wave involves an oscillating two-stream instability followed by a collisionally damped three-dimensional soliton collapse. The result gives an alternative explanation for certain experimental observations.

Weatherall, J. C.↗

NASA NTRS1983

Linking numbers, spin, and statistics of solitons

The spin and statistics of solitons in the (2 + 1)- and (3 + 1)-dimensional nonlinear sigma models is considered. For the (2 + 1)-dimensional case, there is the possibility of fractional spin and exotic statistics; for 3 + 1 dimensions, the usual spin-statistics relation is demonstrated. The linking-number interpretation of the Hopf invariant and the use of suspension considerably simplify the analysis.

Wilczek, F.↗

NASA NTRS1984

Solitons in superfluid (He-3)-A - Bound states on domain walls

The effects of solitons on the spectrum of fermion excitations in superfluid (He-3)-A are investigated. It is found that there is a two-dimensional manifold of bound states with energies within the gap of the bulk superfluid. The bound-state spectrum lacks inversion symmetry parallel to the wall.

Ho, T. L.↗

NASA NTRS1984

Observations of double layer-like and soliton-like structures in the ionosphere

Two types of large electric field signatures, individual pulses and pulse trains, were observed on a sounding rocket launched into the afternoon auroral zone on January 21, 1982. The typical electric fields in the individual pulses were 50 mV/m or larger, aligned mostly parallel to B, and the corresponding potentials were at leat 100 mV (kT approximately 0.3 eV). A lower limit of 15 km/sec can be set on the velocity of these structures, indicating that they were not ion acoustic double layers. The pulse trains, each consisting of on the order of 100 pulses, were observed in close association with intense plasma frequency waves. This correlation is consistent with the interpretation of these trains as Langmuir solitons. The pulse trains correlate better with the intensity of the field-aligned currents than with the energetic electron flux.

Boehm, M. H.↗

NASA NTRS1984

Solitons versus parametric instabilities during ionospheric heating

Various effects associated with ionospheric heating are investigated by numerically solving the modified Zakharov (1972) equations. It is shown that, for typical ionospheric parameters, the modulational instability is more important than the parametric decay instability in the spatial region of strongest heater electric field. It is concluded that the modulational instability leads to the formation of solitons, as originally predicted by Petviashvili (1976).

Nicholson, D. R.↗

NASA NTRS1984

Intermittency and solitons in the driven dissipative nonlinear Schroedinger equation

The cubic nonlinear Schroedinger equation, in the presence of driving and Landau damping, is studied numerically. As the pump intensity is increased, the system exhibits a transition from intermittency to a two-torus to chaos. The laminar phase of the intermittency is also a two-torus motion which corresponds in physical space to two identical solitons of amplitude determined by a power-balance equation.

Moon, H. T.↗

NASA NTRS1984

Modulational instability and soliton formation during ionospheric heating

The most intense electric fields during ionospheric heating occur a fraction of a kilometer below the classical reflection point. At this location, the nonlinear evolution of Langmuir waves is studied within the context of the modified Zakharov equations. It is found that the modulational instability (oscillating two-stream instability) is more important than the three-wave parametric decay instability, leading to the rapid formation of solitons.

Payne, G. L.↗

NASA NTRS1986

Transport by negative eddy viscosity in soliton turbulence

The forced Schrodinger equation is used to describe the microhydrodynamical state of strong soliton turbulence. The Schrodinger equation is transformed into a master equation and is decomposed into a macrogroup, a microgroup, and a submicrogroup, representative of the three transport processes of spectral evolution, transport property, and relaxation. The kinetic equation for the macrodistribution is derived and reverted to the continuum by the method of moments in order to find the equation of spectral evolution. The spectral flow is found to be governed by three types of transport, which are discussed.

Tchen, C. M.↗

NASA NTRS1989

Solitosynthesis: Cosmological evolution of non-topological solitons

The thermal creation, fusion, evaporation, and destruction of non-topological solitons (NTS) after a phase transition in the early universe is considered. By defining and following NTS statistical equilibrium and departures from it, and depending on particle physics parameters, one of three possible scenarios occurs. If reaction rates are high enough, a period of equilibrium occurs and relic abundances are determined by the freeze-out temperature. Equilibrium first drives most NTS's into their constituents (free phi particles) and then causes rapid fusion into large NTS's. If freeze-out occurs during the first phase, the NTS's are almost entirely destroyed, while if it occurs during the second phase, solitosynthesis occurs and NTS's may be cosmically relevant. For slow reaction rates the NTS's are born frozen out and have the abundance determined by the phase transition. Analytic approximations for determining the abundances are developed, and tested by numerically integrating a reaction network in an expanding universe. Unfortunately, for most of the parameter space considered, solito-destruction/evaporation occurs.

Griest, Kim↗

NASA NTRS1989

Statistical fluctuations as the origin of nontopological solitons

Nontopological solitons can be formed during a phase transition in the early universe as long as some net charge can be trapped in regions of false vacuum. It has been previously suggested that a particle-antiparticle asymmetry would provide a source for such trapped charge. It is pointed out that, for the model and parameters considered, statistical fluctuations provide a much larger concentration of charge, and are therefore, the dominant source of charge fluctuations in solitogenesis.

Griest, Kim↗

NASA NTRS1989

Soliton and strong Langmuir turbulence in solar flare processes

The occurrence of modulational instability in the current sheet of a solar flare is investigated. Special attention is given to the plasma microinstability in this sheet and its relation to the flare process. It is found that solitons or strong Langmuir turbulence are likely to occur in the diffusion region under solar flare conditions in which the electric resistivity could be enhanced by several orders of magnitude in the region, resulting in significant heating and stochastic acceleration of particles. A numerical example is used to demonstrate the transition of the magnetic field velocity and plasma density from the outer MHD region into the diffusive region and then back out again with the completion of the energy conversion process. This is all made possible by an increase in resistivity of four to five orders of magnitude over the classical value.

Song, M. T.↗

NASA NTRS1990

Ponderable soliton stars and cosmic background radiation

A theory is developed to describe the possible perturbations of the cosmic background radiation (CBR) by radiation from ponderable soliton stars in the early universe. Since the temperature of such stars is in the range of 10 to the 6th K, thermalization of their emitted radiation is possible. Two models are considered: one in which thermalization is ignored and one in which decoupling from thermalization is considered as a sudden process. The expected perturbation of the CBR is probably less than 1 percent and is largely around the short-wavelength end, in the form of point radio sources. This result is consistent with the most recent COBE measurements.

Chiu, Hong-Yee↗

NASA NTRS1992

Computational modeling of femtosecond optical solitons from Maxwell's equations

An algorithm is developed that permits the direct time integration of full-vector nonlinear Maxwell's equations. This capability permits the modeling of both linear and nonlinear instantaneous and dispersive effects in the electric polarization in material media. The modeling of the optical carrier is retained. The fundamental innovation is to notice that it is possible to treat the linear and nonlinear convolution integrals, which describe the dispersion, as new dependent variables. A coupled system of nonlinear second-order ordinary differential equations can then be derived for the linear and nonlinear convolution integrals, by differentiating them in the time domain. These equations, together with Maxwell's equations, are solved to determine the electromagnetic fields in nonlinear dispersive media. Results are presented of calculations in one dimension of the propagation and collision of femtosecond electromagnetic solitons that retain the optical carrier, taking into account as the Kerr and Raman interactions.

Goorjian, Peter M.↗