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  1. EVIDENCE AGAINST THE OSCILLATING TWO-STREAM INSTABILITY AND SPATIAL COLLAPSE OF LANGMUIR WAVES IN SOLAR TYPE III RADIO BURSTS

    SciTech Connect

    Graham, D. B.; Cairns, Iver H.; Malaspina, D. M.; Ergun, R. E.

    2012-07-01

    Recently Thejappa et al. studied a specific Langmuir wave packet observed by STEREO A and argued based on the electric field from one of the three antennas that this packet satisfied the conditions for the oscillating two-stream instability (OTSI) and was undergoing wave collapse. We analyze the same event using all three electric components and show that, while the wave packet has structure consistent with collapse simulations and theory, the field strength is well below that required for collapse to proceed. Analyzing the three electric field components shows that the power spectrum and dominance of wave power perpendicular to the local magnetic field are inconsistent with OTSI. We show that this packet and other more intense packets are inconsistent with collapse and show no evidence of OTSI, but are likely trapped eigenmodes in density wells. Therefore, OTSI and collapse are unlikely explanations for intense Langmuir events observed in the solar wind.

  2. A theory of solar type 3 radio bursts

    NASA Technical Reports Server (NTRS)

    Goldstein, M. L.; Papadopoulos, K.; Smith, R. A.

    1979-01-01

    Energetic electrons propagating through the interplanetary medium are shown to excite the one dimensional oscillating two stream instability (OTSI). The OTSI is in turn stabilized by anomalous resistivity which completes the transfer of long wavelength Langmuir waves to short wavelengths, out of resonance with the electrons. The theory explains the small energy losses suffered by the electrons in propagating to 1 AU, the predominance of second harmonic radiation, and the observed correlation between radio and electron fluxes.

  3. Phase Coupling in Langmuir Wave Packets: Evidence for Four Wave Interactions in Solar Type III Radio Bursts

    NASA Technical Reports Server (NTRS)

    Thejappa, G.; MacDowall, R. J.; Bergamo, M.

    2012-01-01

    The four wave interaction process, known as the oscillating two stream instability (OTSI) is considered as one of the mechanisms responsible for stabilizing the electron beams associated with solar type III radio bursts. It has been reported that (1) an intense localized Langmuir wave packet associated with a type III burst contains the spectral characteristics of the OTSI: (a) a resonant peak at the local electron plasma frequency, f(sub pe), (b) a Stokes peak at a frequency slightly lower than f(sub pe), (c) anti-Stokes peak at a frequency slightly higher than f(sub pe), and (d) a low frequency enhancement below a few hundred Hz, (2) the frequencies and wave numbers of these spectral components satisfy the resonance conditions of the OTSI, and (3) the peak intensity of the wave packet is well above the thresholds for the OTSI as well as spatial collapse of envelope solitons. Here, for the first time, applying the trispectral analysis on this wave packet, we show that the tricoherence, which measures the degree of coherent four-wave coupling amongst the observed spectral components exhibits a peak. This provides an additional evidence for the OTSI and related spatial collapse of Langmuir envelope solitons in type III burst sources.

  4. Nonlinear stability of solar type 3 radio bursts. 2: Application to observations near 1 AU

    NASA Technical Reports Server (NTRS)

    Goldstein, M. L.; Smith, R. A.; Papadopoulos, K.

    1978-01-01

    A set of rate equations including strong turbulence effects and anomalous resitivity are solved using parmeters which model several solar type 3 bursts. Exciter distributions observed at 1 AU are excitation of the linear bump-in-tail instability, amplifying Langmuir waves above the threshold for the oscillating two stream instability (OTSI). The OTSI, and the attendant anomalous resistivity produce a rapid spectral transfer of Langmuir waves to short wavelengths, out of resonance with the electron exciter. Further energy loss of the beam is thus precluded. The various parameters needed to model the bursts are extrapolated inside 1 AU with similar results. Again, the OTSI is excited and decouples the electron beam from the Langmuir radiation. Reabsorption of the Langmuir waves by the beam is shown to be unimportant in all cases, even at 0.1 AU. The theory provides a natural explanation for the observed realationship between radio flux, and the electron flux.

  5. Evidence for four- and three-wave interactions in solar type III radio emissions

    NASA Astrophysics Data System (ADS)

    Thejappa, G.; MacDowall, R. J.; Bergamo, M.

    2013-08-01

    The high time resolution observations obtained by the STEREO/WAVES experiment show that in the source regions of solar type III radio bursts, Langmuir waves often occur as intense localized wave packets with short durations of only few ms. One of these wave packets shows that it is a three-dimensional field structure with WLneTe ~ 10-3, where WL is the peak energy density, and ne and Te are the electron density and temperature, respectively. For this wave packet, the conditions of the oscillating two-stream instability (OTSI) and supersonic collapse are satisfied within the error range of determination of main parameters. The density cavity, observed during this wave packet indicates that its depth, width and temporal coincidence are consistent with those of a caviton, generated by the ponderomotive force of the collapsing wave packet. The spectrum of each of the parallel and perpendicular components of the wave packet contains a primary peak at fpe, two secondary peaks at fpe ± fS and a low-frequency enhancement below fS, which, as indicated by the frequency and wave number resonance conditions, and the fast Fourier transform (FFT)-based tricoherence spectral peak at (fpe, fpe, fpe + fS, fpe - fS), are coupled to each other by the OTSI type of four-wave interaction (fpe is the local electron plasma frequency and fS is the frequency of ion sound waves). In addition to the primary peak at fpe, each of these spectra also contains a peak at 2fpe, which as indicated by the frequency and wave number resonance conditions, and the wavelet-based bicoherence spectral peak at (fpe, fpe), appears to correspond to the second harmonic electromagnetic waves generated as a result of coalescence of oppositely propagating sidebands excited by the OTSI. Thus, these observations for

  6. Oscillating two-stream instability in a magnetized electron-positron-ion plasma

    NASA Astrophysics Data System (ADS)

    Tinakiche, Nouara; Annou, R.

    2015-04-01

    Oscillating two-stream instability (OTSI) in a magnetized electron-ion plasma has been thoroughly studied, e.g., in ionospheric heating experiments [C. S. Liu and V. K. Tripathi, Interaction of Electromagnetic Waves With Electron Beams and Plasmas (World Scientific, 1994); V. K. Tripathi and P. V. Siva Rama Prasad, J. Plasma Phys. 41, 13 (1989); K. Ramachandran and V. K. Tripathi, IEEE Trans. Plasma Sci. 25, 423 (1997)]. In this paper, OTSI is investigated in a magnetized electron-positron-ion plasma. The dispersion relation of the process is established. The pump field threshold, along with the maximum growth rate of the instability is assessed using the Arecibo and HAARP parameters.

  7. Interrater reliability and discriminative validity of the structural elements of the Ayres Sensory Integration Fidelity Measure.

    PubMed

    May-Benson, Teresa A; Roley, Susanne Smith; Mailloux, Zoe; Parham, L Diane; Koomar, Jane; Schaaf, Roseann C; Jaarsveld, Annamarie Van; Cohn, Ellen

    2014-01-01

    This study examined the reliability and validity of the structural section of the Ayres Sensory Integration® Fidelity Measure© (ASIFM), which provides a method for monitoring the extent to which an intervention was implemented as conceptualized in studies of occupational therapy using sensory integration intervention methods (OT-SI). We examined the structural elements of the measure, including content of assessment reports, availability of specific equipment and adequate space, safety monitoring, and integration of communication with parents and other team members, such as collaborative goal setting with parents or family and teacher education, into the intervention program. Analysis of self-report ratings by 259 occupational therapists from 185 different facilities indicated that the structural section of the ASIFM has acceptable interrater reliability (r ≥ .82) and significantly differentiates between settings in which therapists reportedly do and do not practice OT-SI (p < .001). PMID:25184462

  8. Oscillating two-stream instability in a magnetized electron-positron-ion plasma

    SciTech Connect

    Tinakiche, Nouara; Annou, R.

    2015-04-15

    Oscillating two-stream instability (OTSI) in a magnetized electron-ion plasma has been thoroughly studied, e.g., in ionospheric heating experiments [C. S. Liu and V. K. Tripathi, Interaction of Electromagnetic Waves With Electron Beams and Plasmas (World Scientific, 1994); V. K. Tripathi and P. V. Siva Rama Prasad, J. Plasma Phys. 41, 13 (1989); K. Ramachandran and V. K. Tripathi, IEEE Trans. Plasma Sci. 25, 423 (1997)]. In this paper, OTSI is investigated in a magnetized electron-positron-ion plasma. The dispersion relation of the process is established. The pump field threshold, along with the maximum growth rate of the instability is assessed using the Arecibo and HAARP parameters.

  9. EVIDENCE FOR THE OSCILLATING TWO STREAM INSTABILITY AND SPATIAL COLLAPSE OF LANGMUIR WAVES IN A SOLAR TYPE III RADIO BURST

    SciTech Connect

    Thejappa, G.; Bergamo, M.; Papadopoulos, K.; MacDowall, R. J. E-mail: mbergamo@umd.edu E-mail: Robert.MacDowall@nasa.gov

    2012-03-15

    We present observational evidence for the oscillating two stream instability (OTSI) and spatial collapse of Langmuir waves in the source region of a solar type III radio burst. High time resolution observations from the STEREO A spacecraft show that Langmuir waves excited by the electron beam occur as isolated field structures with short durations {approx}3.2 ms and with high intensities exceeding the strong turbulence thresholds. These short duration events are identified as the envelope solitons which have collapsed to spatial scales of a few hundred Debye lengths. The spectra of these wave packets contain an intense peak and two sidebands, corresponding to beam-resonant Langmuir waves, and down-shifted and up-shifted daughter Langmuir waves, respectively, and low-frequency enhancements below a few hundred Hz. The frequencies and wave numbers of these spectral components satisfy the resonance conditions of the OTSI. The observed high intensities, short scale lengths, sideband spectral structures, and low-frequency enhancements strongly suggest that the OTSI and spatial collapse of Langmuir waves probably control the nonlinear beam-plasma interactions in type III radio bursts.

  10. Thermodynamic Modeling and Analysis of Human Stress Response

    NASA Technical Reports Server (NTRS)

    Boregowda, S. C.; Tiwari, S. N.

    1999-01-01

    A novel approach based on the second law of thermodynamics is developed to investigate the psychophysiology and quantify human stress level. Two types of stresses (thermal and mental) are examined. A Unified Stress Response Theory (USRT) is developed under the new proposed field of study called Engineering Psychophysiology. The USRT is used to investigate both thermal and mental stresses from a holistic (human body as a whole) and thermodynamic viewpoint. The original concepts and definitions are established as postulates which form the basis for thermodynamic approach to quantify human stress level. An Objective Thermal Stress Index (OTSI) is developed by applying the second law of thermodynamics to the human thermal system to quantify thermal stress or dis- comfort in the human body. The human thermal model based on finite element method is implemented. It is utilized as a "Computational Environmental Chamber" to conduct series of simulations to examine the human thermal stress responses under different environmental conditions. An innovative hybrid technique is developed to analyze human thermal behavior based on series of human-environment interaction simulations. Continuous monitoring of thermal stress is demonstrated with the help of OTSI. It is well established that the human thermal system obeys the second law of thermodynamics. Further, the OTSI is validated against the experimental data. Regarding mental stress, an Objective Mental Stress Index (OMSI) is developed by applying the Maxwell relations of thermodynamics to the combined thermal and cardiovascular system in the human body. The OMSI is utilized to demonstrate the technique of monitoring mental stress continuously and is validated with the help of series of experimental studies. Although the OMSI indicates the level of mental stress, it provides a strong thermodynamic and mathematical relationship between activities of thermal and cardiovascular systems of the human body.

  11. The thresholds of ionospheric plasma instabilities pumped by high-frequency radio waves at EISCAT

    NASA Astrophysics Data System (ADS)

    Bryers, C. J.; Kosch, M. J.; Senior, A.; Rietveld, M. T.; Yeoman, T. K.

    2013-11-01

    We test the existing theories regarding the thresholds for the parametric decay instability (PDI), the oscillating two-steam instability (OTSI), and the thermal parametric instability (TPI) using the European Incoherent Scatter (EISCAT) facility's ionospheric heater. In these processes, the pump wave can couple to various electrostatic waves in the F layer ionosphere, which can be observed using the EISCAT UHF radar (PDI and OTSI) or by HF radar (TPI). On 19 October 2012, the heater power was stepped from ˜0.5 MW to ˜100 MW effective radiated power in seven steps using a 1 min on, 1 min off cycle. We use an electric field model, taking into account D region absorption, to compare theory with our observations. In all three cases, we find good agreement. In addition, the growth of striations formed during the TPI causes anomalous absorption of the heater wave, which we observe as decreased UHF ion line and plasma line backscatter power. We show evidence that heating for a prolonged period of time reduces the UHF ion line intensity throughout the experiment.

  12. Evidence for Langmuir Envelope Solitons in Solar Type III Burst Source Regions

    NASA Technical Reports Server (NTRS)

    Thejappa, G.; Goldstein, M. L.; MacDowall, R. J.; Papadopoulos, K.; Stone, R. G.

    1998-01-01

    We present observational evidence for the generation of Langmuir envelope solitons in the source regions of solar type III radio bursts. The solitons appear to be formed by electron beams which excite either the modulational instability or oscillating two-stream instability (OTSI). Millisecond data from the Ulysses Unified Radio and Plasma Wave Experiment (URAP) show that Langmuir waves associated with type III bursts occur as broad intense peaks with time scales ranging from 15 to 90 milliseconds (6 - 27 km). These broad field structures have the properties expected of Langmuir envelope solitons, viz.: the normalized peak energy densities, W(sub L)/n(sub e)T(sub e) approximately 10(exp -5), are well above the modulational instability threshold; the spatial scales, L, which range from 1 - 5 Langmuir wavelengths, show a high degree of inverse correlation with (W(sub L)/n(sub e)T(sub e))(sup 1/2); and the observed widths of these broad peaks agree well with the predicted widths of envelope solitons. We show that the orientation of the Langmuir field structures is random with respect to the ambient magnetic field, indicating that they are probably isotropic structures that have evolved from initially pancake-like solitons. These observations suggest that strong turbulence processes, such as the modulational instability or the OTSI, stabilize the electron beams that produce type III bursts.

  13. Nonlinear stability of solar type 3 radio bursts. 1: Theory

    NASA Technical Reports Server (NTRS)

    Smith, R. A.; Goldstein, M. L.; Papadopoulos, K.

    1978-01-01

    A theory of the excitation of solar type 3 bursts is presented. Electrons initially unstable to the linear bump-in-tail instability are shown to rapidly amplify Langmuir waves to energy densities characteristic of strong turbulence. The three-dimensional equations which describe the strong coupling (wave-wave) interactions are derived. For parameters characteristic of the interplanetary medium the equations reduce to one dimension. In this case, the oscillating two stream instability (OTSI) is the dominant nonlinear instability, and is stablized through the production of nonlinear ion density fluctuations that efficiently scatter Langmuir waves out of resonance with the electron beam. An analytical model of the electron distribution function is also developed which is used to estimate the total energy losses suffered by the electron beam as it propagates from the solar corona to 1 A.U. and beyond.