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P K Shukla - One of the best experts on this subject based on the ideXlab platform.

  • nonlinear interactions between electromagnetic waves and Electron Plasma oscillations in quantum Plasmas
    Physical Review Letters, 2007
    Co-Authors: P K Shukla, Bengt Eliasson
    Abstract:

    We consider nonlinear interactions between intense circularly polarized electromagnetic (CPEM) waves and Electron Plasma oscillations (EPOs) in a dense quantum Plasma, taking into account the Electron density response in the presence of the relativistic ponderomotive force and mass increase in the CPEM wave fields. The dynamics of the CPEM waves and EPOs is governed by the two coupled nonlinear Schrodinger equations and Poisson’s equation. The nonlinear equations admit the modulational instability of an intense CPEM pump wave against EPOs, leading to the formation and trapping of localized CPEM wave pipes in the Electron density hole that is associated with a positive potential distribution in our dense Plasma. The relevance of our investigation to the next generation intense laser-solid density Plasma interaction experiments is discussed.

  • near wall layer of a positive dust Electron Plasma in the presence of a nonequilibrium charging process
    Physics of Plasmas, 2001
    Co-Authors: M S Benilov, P K Shukla
    Abstract:

    Accounting for a nonequilibrium charging process in a positive dust–Electron Plasma, a theory is developed for a quasi-neutral layer separating the near-wall space–charge sheath from the bulk Plasma where the charging of the dust grains is quasi-equilibrium (i.e., the current of the Electrons emitted by a dust grain is approximately equal to the current of the Electrons collected by the grain). The problem is solvable when the velocity of the dust particles entering the layer from the quasi-equilibrium Plasma satisfies an inequality which is mathematically, although not physically, similar to the Bohm criterion. The obtained results explain the reason for the absence of a continuous transition from the Bohm criterion in a dusty Plasma with a variable dust particle charge to the conventional Bohm criterion for an Electron–ion Plasma with constant ion charge.

  • near wall space charge sheaths in a positive dust Electron Plasma
    Physica Scripta, 2001
    Co-Authors: M S Benilov, P K Shukla
    Abstract:

    A space-charge sheath near a negative surface in a Plasma composed of dust grains of a variable positive charge, Electrons, and neutral particles, is considered. The limiting case of large ratio of the Electron Debye radius to the length scale of variation of the charge of a dust grain is treated. The charging of dust grains in the sheath is quasi-equilibrium in such a case, i.e. the current of the Electrons emitted by a dust grain is approximately equal to the current of the Plasma Electrons collected by the grain. An analytical solution decribing the sheath is found for this limiting case. A further simplification may be achieved in cases when the mean energy of Electrons emitted by the dust grain is much smaller than the surface potential of the grain.

C Joshi - One of the best experts on this subject based on the ideXlab platform.

  • ultrahigh gradient acceleration of injected eletrons by laser excited relativistic Electron Plasma waves
    Physical Review Letters, 1993
    Co-Authors: C E Clayton, W P Leemans, M J Everett, K A Marsh, A Dyson, Amit K Lal, R Williams, C Joshi
    Abstract:

    High-gradient acceleration of externally injected 2.1-MeV Electrons by a laser beat wave driven relativistic Plasma wave has been demonstrated for the first time. Electrons with energies up to the detection limit of 9.1 MeV were detected when such a Plasma wave was resonantly excited using a two-frequency laser. This implies a gradient of 0.7 GeV/m, corresponding to a Plasma-wave amplitude of more than 8%. The Electron signal was below detection threshold without injection or when the laser was operated on a single frequency.

  • ultrahigh gradient acceleration of injected Electrons by laser excited relativistic Electron Plasma waves
    Physical Review Letters, 1993
    Co-Authors: C E Clayton, W P Leemans, M J Everett, K A Marsh, A Dyson, Amit K Lal, R Williams, C Joshi
    Abstract:

    High-gradient acceleration of externally injected 2.1-MeV Electrons by a laser beat wave driven relativistic Plasma wave has been demonstrated for the first time. Electrons with energies up to the detection limit of 9.1 MeV were detected when such a Plasma wave was resonantly excited using a two-frequency laser. This implies a gradient of 0.7 GeV/m, corresponding to a Plasma-wave amplitude of more than 8%. The Electron signal was below detection threshold without injection or when the laser was operated on a single frequency.

Suresh C Sharma - One of the best experts on this subject based on the ideXlab platform.

  • Electron Plasma wave excitation by a q gaussian laser beam and subsequent Electron acceleration
    Physics of Plasmas, 2020
    Co-Authors: Monika Yadav, D N Gupta, Suresh C Sharma
    Abstract:

    In this paper, we theoretically study the propagation dynamics of a q-Gaussian laser beam in a Plasma by considering the relativistic and ponderomotive nonlinearities. The q-Gaussian laser beam exhibits unique characteristics while interacting with the Plasma. The q-Gaussian laser beam redistributes the Plasma density in a different way, which affects the laser self-focusing. A comparative study of the self-focusing for Gaussian and q-Gaussian laser beams is reported. The results obtained from numerical analysis reveal a stronger self-focusing of the q-Gaussian laser beam in Plasmas, which is desirable to excite a large amplitude Plasma wave for Electron acceleration by extending the interaction length. We then extended this study to investigate the Electron Plasma wave excitation by the q-Gaussian laser beam. The Electron Plasma wave is driven more efficiently by the q-Gaussian laser beam. Our results show that the Electron Plasma wave field intensity enhances more than twofold for the q-Gaussian laser beam in comparison with the case of a Gaussian laser beam. The Electron Plasma wave excited by a q-Gaussian beam can accelerate the Plasma Electrons to higher energies. Numerical results are presented for the established set of laser and Plasma parameters.

Naveen Gupta - One of the best experts on this subject based on the ideXlab platform.

  • second harmonic generation of self focused cosh gaussian laser beam in thermal quantum Plasma by excitation of an Electron Plasma wave
    Contributions To Plasma Physics, 2016
    Co-Authors: Naveen Gupta, Arvinder Singh
    Abstract:

    This paper presents a scheme for second harmonic generation (SHG) of an intense Cosh-Gaussian (ChG) laser beam in thermal quantum Plasmas. Moment theory approach in W.K.B approximation has been adopted in deriving the differential equation governing the propagation characteristics of the laser beam with distance of propagation. The effect of relativistic increase in Electron mass on propagation dynamics of laser beam has been incorporated. Due to relativistic nonlinearity in the dielectric properties of the Plasma, the laser beam gets self-focused and produces density gradients in the transverse direction. The generated density gradients excite Electron Plasma wave (EPW) at pump frequency that interacts with the incident laser beam to produce its second harmonics. Numerical simulations have been carried out to investigate the effects of laser parameters on selffocusing of the laser beam and hence on the conversion efficiency of its second harmonics. Simulation results predict that within a specific range of decentered parameter the ChG laser beams show smaller divergence as they propagate and, thus, lead to enhanced conversion efficiency of second harmonics. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

  • beat wave excitation of Electron Plasma wave by relativistic cross focusing of cosh gaussian laser beams in Plasma
    Physics of Plasmas, 2015
    Co-Authors: Arvinder Singh, Naveen Gupta
    Abstract:

    A scheme for beat wave excitation of Electron Plasma wave (EPW) is proposed by relativistic cross-focusing of two coaxial Cosh-Gaussian (ChG) laser beams in an under dense Plasma. The Plasma wave is generated on account of beating of two coaxial laser beams of frequencies ω1 and ω2. The mechanism for laser produced nonlinearity is assumed to be relativistic nonlinearity in Electron mass. Following moment theory approach in Wentzel Kramers Brillouin (W.K.B) approximation, the coupled differential equations governing the evolution of spot size of laser beams with distance of propagation have been derived. The relativistic nonlinearity depends not only on the intensity of first laser beam but also on the intensity of second laser beam. Therefore, propagation dynamics of one laser beam affect that of second beam and hence cross-focusing of the two laser beams takes place. Due to non uniform intensity distribution of pump laser beams, the background Electron concentration gets modified. The amplitude of EPW, w...

Donald A. Gurnett - One of the best experts on this subject based on the ideXlab platform.

  • Electron Plasma Oscillations Upstream of the Solar Wind Termination Shock
    2016
    Co-Authors: Donald A. Gurnett, William S. Kurth, Hz Where
    Abstract:

    Electron Plasma oscillations have been detected upstream of the solar wind ter-mination shock by the Plasma wave instrument on the Voyager 1 spacecraft. These waves were first observed on 11 February 2004, at a heliocentric radial distance of 91.0 astronomical units, and continued sporadically with a gradually increasing occurrence rate for nearly a year. The last event occurred on 15 December 2004, at 94.1 astronomical units, just before the spacecraft crossed the termination shock. Since then, no further Electron Plasma oscillations have been observed, consistent with the spacecraft having crossed the termination shock into the heliosheath. Electron Plasma oscillations, also known as Langmuir waves, are one of the oldest known and most widely studied of all Plasma wave phenomena (1). For many years it has been known that Electron Plasma oscillations are generated ahead of planetary bow shocks by energetic Electrons escaping into the solar wind upstream of the shock (2–7). This close relationship led Kurth and Gurnett (8) to pre-dict that Electron Plasma oscillations would be present upstream of the solar wind termination shock. Here, we report the initial observations of these waves. Electron Plasma oscillations are electro-static oscillations that occur at a characteristic frequency of the Plasma known as the Electron Plasma frequency. The Electron Plasma fre-quency is given by fp 0 8980 ffiffiffiffi n

  • intense Plasma wave emissions associated with saturn s moon rhea
    AGUFM, 2010
    Co-Authors: Donald A. Gurnett, G B Hospodarsky, W S Kurth, O Santolik, G H Jones, P Schippers, F J Crary, J S Leisner, C T Russell
    Abstract:

    [1] Measurements by the Cassini spacecraft during a close flyby of Saturn's moon Rhea on March 2, 2010, show the presence of intense Plasma waves in the magnetic flux tube connected to the surface of the moon. Three types of waves were observed, (1) bursty electrostatic waves near the Electron Plasma frequency, (2) intense whistler-mode emissions below one half of the Electron cyclotron frequency, and (3) broadband electrostatic waves at frequencies well below the ion Plasma frequency. The waves near the Electron Plasma frequency are believed to be driven by a low energy (∼35 eV) Electron beam accelerated away from Rhea. Their bursty structure is believed to be due to a nonlinear process similar to the three-wave interaction that occurs for Langmuir waves in the solar wind. The whistler-mode emissions are propagating toward Rhea and are shown to be generated by the loss-cone anisotropy (at parallel cyclotron resonance energies around 230 eV) caused by absorption of Electrons at the surface of the moon. Scattering by these whistler-mode waves may be able to explain previously reported depletions of energetic Electrons in the vicinity of the moon. The low-frequency waves may play a role in nonlinear three-wave interactions with the bursty electrostatic waves.

  • Electron densities in the upper ionosphere of mars from the excitation of Electron Plasma oscillations
    AGUFM, 2008
    Co-Authors: F. Duru, Donald A. Gurnett, A F Nagy, Ronan Modolo, D D Morgan, D Najib
    Abstract:

    In addition to remote radio sounding of the ionosphere of Mars, the MARSIS (MarsAdvanced Radar for Subsurface and Ionospheric Sounding) instrument on the MarsExpress spacecraft is also able to measure the in situ Electron density from the excitationof local Electron Plasma oscillations. This paper presents an investigation of the Electrondensity in the upper ionosphere of Mars based on the frequency of these oscillations.The advantage of this method is that Electron densities can be measured at much higheraltitudes than can be determined from remote radio soundings. Using this techniqueElectron densities from 503 orbits have been analyzed over the period from 4 August 2005to 31 July 2007 for altitudes ranging from about 275 to 1300 km. Although there isconsiderable variability from orbit to orbit, the median Electron density at a given solarzenith angle (SZA) on the dayside of Mars decreases systematically with increasingaltitude with a characteristic Plasma scale height varying from about 80 to 145 km.At a fixed altitude, the Electron density remains almost constant for SZAs less than about80 . For SZAs greater than about 80 the Electron density decreases rapidly withincreasing SZA, approaching very low values on the nightside. Simulations performedusing both magnetohydrodynamic and hybrid codes show that the nearly constant densityat a given altitude is caused by the horizontal transport of Plasma from the daysidetoward the nightside due to interaction with the solar wind.

  • Electron Plasma oscillations upstream of the solar wind termination shock.
    Science, 2005
    Co-Authors: Donald A. Gurnett, William S. Kurth
    Abstract:

    Electron Plasma oscillations have been detected upstream of the solar wind termination shock by the Plasma wave instrument on the Voyager 1 spacecraft. These waves were first observed on 11 February 2004, at a heliocentric radial distance of 91.0 astronomical units, and continued sporadically with a gradually increasing occurrence rate for nearly a year. The last event occurred on 15 December 2004, at 94.1 astronomical units, just before the spacecraft crossed the termination shock. Since then, no further Electron Plasma oscillations have been observed, consistent with the spacecraft having crossed the termination shock into the heliosheath.

  • fine structure of langmuir waves observed upstream of the bow shock at venus
    Journal of Geophysical Research, 1994
    Co-Authors: G B Hospodarsky, Donald A. Gurnett, W S Kurth, M G Kivelson, R J Strangeway, S J Bolton
    Abstract:

    Highly structured Langmuir waves, also known as Electron Plasma oscillations, have been observed in the foreshock of Venus using the Plasma wave experiment on the Galileo spacecraft during the gravity assist flyby on February 10, 1990. The Galileo wideband sampling system provides digital electric field waveform measurements at sampling rates up to 201,600 samples per second, much higher than any previous instrument of this type. The main Langmuir wave emission band occurs near the local Electron Plasma frequency, which was approximately 43 kHz. The Langmuir waves are observed to shift above and below the Plasma frequency, sometimes by as much as 20 kHz. The shifts in frequency are closely correlated with the downstream distance from the tangent field line, implying that the shifts are controlled by the Electron beam velocity. Considerable fine structure is also evident, with timescales as short as 0.15 ms, corresponding to spatial scales of a few tens of Debye lengths. The frequency spectrum often consists of beat-type waveforms, with beat frequencies ranging from 0.2 to 7 kHz, and in a few cases, isolated wave packets. The peak electric field strengths are approximately 1 mV/m. These field strengths are too small for strongly nonlinear processes to be important. The beat-type waveforms are suggestive of a parametric decay process.