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  • LUNAR AND PLANETARY EXPLORATION  (7)
  • AERODYNAMICS  (5)
  • ASTROPHYSICS  (3)
  • 1
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    ULF turbulence in the Neptunian polar cusp (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Results of a spectral analysis of the ULF wave turbulence in the Neptunian polar cusp are presented. The activity is characterized as broadbanded, extending up to a maximum frequency of about 0.5 Hz, and having maximum wave amplitudes as large as 6 percent of the dc magnetic field. Activity in the cusp region was particularly intense at its frontside and backside, associated with the magnetopause and cusp/magnetosphere boundaries, respectively. The turbulence, particularly that above f(ci), is tentatively identified as whistler mode. It is argued that such whistler mode turbulence should resonate with electrons having energies in the tens of kiloelectron volts. Observations indicate a very strong correlation of the ULF turbulence with the energetic electrons between 22 and 35 keV measured by Voyager's low-energy charged particle experiment. A vigorous interaction between the two is inferred. ULF wave turbulence in the cusp may represent a significant but not complete power source for the magnetosphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 98; A3; p. 3631-3643.
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  • 2
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    Large amplitude MHD waves upstream of the Jovian bow shock (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Observations of large amplitude MHD waves upstream of Jupiter's bow shock are analyzed. The waves are found to be right circularly polarized in the solar wind frame, which suggests that they are propagating in the fast magnetosonic mode. A complete spectral and minimum variance eigenvalue analysis of the data was performed. The power spectrum of the magnetic fluctuations contains several peaks. The fluctuations at 2.3 MHz have a direction of minimum variance anti-parallel to the direction of the average magnetic field. Several harmonics at 6, 9, and 12 MHz are also present. The direction of minimum variance of these fluctuations lies at approximately 40 deg to the magnetic field. It is argued that these fluctuations are waves excited by protons reflected off the Jovian bow shock. The inferred speed of the reflected protons is about two times the solar wind speed in the solar wind frame. A linear instability analysis is presented that suggests an explanation for many of the observed features of the observations. The fluctuations apparently contain a significant fraction of magnetic energy that is linearly polarized and in the Alfven mode.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 88; 9989-999
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  • 3
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    Large-amplitude MHD waves upstream of the Jovian bow shock Reinterpretation (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Observations of large amplitude magnetohydrodynamic (MHD) waves upstream of the Jovian bow shock were previously interpreted as arising from a resonant electromagnetic ion beam instability. That interpretation was based on the conclusion that the observed fluctuations were predominantly right elliptically polarized in the solar wind rest frame. Because it was noted that the fluctuations are, in fact, left elliptically polarized, a reanalysis of the observations was necessary. Several mechanisms for producing left hand polarized MHD waves in the observed frequency range were investigated. Instabilities excited by protons appear unlikely to account for the observations. A resonant instability excited by relativistic electrons escaping from the Jovian magnetosphere is a likely source of free energy consistent with the observations. Evidence for the existence of such a population of electrons was found in both the Low Energy Charged Particle experiments and Cosmic Ray experiments on Voyager 2.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 90; 302-310
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  • 4
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    The application of CFD for military aircraft design at transonic speeds (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Numerous computational fluid dynamics (CFD) codes are available that solve any of several variations of the transonic flow equations from small disturbance to full Navier-Stokes. The design philosophy at General Dynamics Fort Worth Division involves use of all these levels of codes, depending on the stage of configuration development. Throughout this process, drag calculation is a central issue. An overview is provided for several transonic codes and representative test-to-theory comparisons for fighter-type configurations are presented. Correlations are shown for lift, drag, pitching moment, and pressure distributions. The future of applied CFD is also discussed, including the important task of code validation. With the progress being made in code development and the continued evolution in computer hardware, the routine application of these codes for increasingly more complex geometries and flow conditions seems apparent.
    Keywords: AERODYNAMICS
    Type: NASA, Langley Research Center, Transonic Symposium: Theory, Application, and Experiment, Volume 1, Part 1; p 109-132
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  • 5
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    Turbulence analysis of the Jovian upstream 'wave' phenomenon (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: As Voyager 2 approached Jupiter's bow shock, large-amplitude fluctuations were seen in both the magnetic field and plasma fluid velocity. These fluctuations generally coincided with the occurrence of long-lived energetic particle events similar to the upstream waves often observed near the earth's bow shock. In this paper an analysis of the magnetic field and plasma observations using spectral methods is presented. The characteristic spectral features related to the upstream waves are generally seen near 1 mHz. The measured correlation lengths of these fluctuations suggest that they are coherent over only a few wavelengths. The analysis is consistent with the hypothesis that these fluctuations are driven by streaming ions, possibly protons. No evidence for the existence of whistler waves is found. It is argued that some of the observed spectral features suggest that dynamical turbulent processes are occurring in the uptream wave region, including a possible observation of an inverse cascade of magnetic helicity to large spatial scales.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 88; July 1
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  • 6
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    Application of the vortex-lattice technique to the analysis of thin wings with vortex separation and thick multi-element wings (1976)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Two techniques for extending the range of applicability of the basic vortex-lattice method are discussed. The first improves the computation of aerodynamic forces on thin, low-aspect-ratio wings of arbitrary planforms at subsonic Mach numbers by including the effects of leading-edge and tip vortex separation, characteristic of this type wing, through use of the well-known suction-analogy method of E. C. Polhamus. Comparisons with experimental data for a variety of planforms are presented. The second consists of the use of the vortex-lattice method to predict pressure distributions over thick multi-element wings (wings with leading- and trailing-edge devices). A method of laying out the lattice is described which gives accurate pressures on the top and part of the bottom surface of the wing. Limited comparisons between the result predicted by this method, the conventional lattice arrangement method, experimental data, and 2-D potential flow analysis techniques are presented.
    Keywords: AERODYNAMICS
    Type: NASA. Langley Res. Center Vortex-Lattice Utilization; p 237-260
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  • 7
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    Observational study of the IMF spiral north and south of the current sheet (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: We have analyzed 23 years of spacecraft observations spanning 27 AU. Our analysis reveals both an overwinding of the interplanetary magnetic field (IMF) and a sustained asymmetry between the northern and southern hemispheres of the heliosphere. Nonzero azimuthal field components at the source boundary may account for the observed overwinding. The north-south asymmetry, whereby the IMF spiral north of the current sheet is more tightly wound than the IMF spiral south of the current sheet, persists due to unknown sources. It is also shown that there exist significant, correlated departures from the Parker theory in the azimuthal component of the field.
    Keywords: ASTROPHYSICS
    Type: In: Solar Wind Seven; Proceedings of the 3rd COSPAR Colloquium, Goslar, Germany, Sept. 16-20, 1991 (A93-33554 13-92); p. 273-276.
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  • 8
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    Large amplitude MHD waves upstream of the Jovian bow shock: Reinterpretation (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Observations of large amplitude magnetohydrodynamic (MHD) waves upstream of the Jovian bow shock were previously interpreted as arising from a resonant electromagnetic ion beam instability. That interpretation was based on the conclusion that the observed fluctuations were predominantly right elliptically polarized in the solar wind rest frame. Because it was noted that the fluctuations are, in fact, left elliptically polarized, a reanalysis of the observations was necessary. Several mechanisms for producing left hand polarized MHD waves in the observed frequency range were investigated. Instabilities excited by protons appear unlikely to account for the observations. A resonant instability excited by relativistic electrons escaping from the Jovian magnetosphere is a likely source of free energy consistent with the observations. Evidence for the existence of such a population of electrons was found in both the Low Energy Charged Particle experiments and Cosmic Ray experiments on Voyager 2.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-TM-86131 , NAS 1.15:86131
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  • 9
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    An experimental investigation of leading-edge vortex augmentation by blowing (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A wind tunnel test was conducted to determine the effects of over-the-wing blowing as a means of augmenting the leading-edge vortex flow of several pointed-tip, sharp-edged planforms. Arrow, delta, and diamond wings with leading-edge sweeps of 30 and 45 degrees were mounted on a body-of-revolution fuselage and tested in a low-speed wind tunnel at a Mach number of 0.2. Nozzle location data, pitch data, and flow-visualization pictures were obtained for a range of blowing rates. Results show pronounced increases in vortex lift due to the blowing.
    Keywords: AERODYNAMICS
    Type: NASA-CR-132415
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  • 10
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    Large amplitude MHD waves upstream of the Jovian bow shock (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Observations of large amplitude magnetohydrodynamics (MHD) waves upstream of Jupiter's bow shock are analyzed. The waves are found to be right circularly polarized in the solar wind frame which suggests that they are propagating in the fast magnetosonic mode. A complete spectral and minimum variance eigenvalue analysis of the data was performed. The power spectrum of the magnetic fluctuations contains several peaks. The fluctuations at 2.3 mHz have a direction of minimum variance along the direction of the average magnetic field. The direction of minimum variance of these fluctuations lies at approximately 40 deg. to the magnetic field and is parallel to the radial direction. We argue that these fluctuations are waves excited by protons reflected off the Jovian bow shock. The inferred speed of the reflected protons is about two times the solar wind speed in the plasma rest frame. A linear instability analysis is presented which suggests an explanation for many of the observed features of the observations.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-TM-85005 , NAS 1.15:85005
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