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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Autocorrelation of wind observations

Autocorrelation and variance statistics are calculated for cloud motion measurements from four different sources, rawinsonde wind reports, synoptic land station reports, ship reports, aircraft reports, automatic aircraft reports gathered during the Global Weather Experiment, and Seasat scatterometer winds from September 1978. The last of these data sources exhibited the highest autocorrelations and lowest standard deviations over short distances. Structure function plots of autocovariances against separation distance between observations indicated that Seasat was most sensitive to wind field structure by having low autovariance at short distances.

Wylie, D. P.↗
NASA NTRS1995

Acceleration phenomena of high-speed wind observed at 0.1-0.3 AU with interplanetary scintillation

The radial distance dependence of solar wind speeds, which were measured by interplanetary scintillation method, has been studied especially for a high-speed solar wind, and large increase of the IPS speeds (300 km/s) was observed at the distance range of 0.1 - 0.3 AU. When the streams are mapped back onto the source surface, they distribute in polar coronal holes or their boundaries. Since the IPS measurement can be biased by several effects such as of line-of-sight integration, strong scattering and random velocities, we examined these biasing effects and have found difficulty to explain the large IPS speed increase with the biasing effects.

Kojima, M.↗
NASA NTRS1986

Solar wind observations near the sun

Observations of interplanetary scintillations with the VLA telescope are reported. The solar wind in the accelerating region from 3 to 12 solar radii was observed by scintillation of the radio source 3C279. The results obtained outside of 7 solar radii showed good agreement with previous work but observations between 3 and 4.5 solar radii were new and unexpected. Turbulence in the solar wind has a spatially anisotropic structure elongated in the radial direction, the flow direction being also in the radial direction. An abrupt change of both the velocity and the spatial anisotropy of turbulence was found at distances from 3 to 4.5 solar radii. There is a large random velocity component inside of 12 solar radii which is comparable to the bulk flow speed, and it has a spatially anisotropic probability distribution. From the measured cross-correlation functions, evidence which may be related to the complex structure of the magnetic field is found.

Armstrong, J. W.↗
NASA NTRS2000

Connecting the Sun and the solar wind: source regions of the fast wind observed in interplanetary space

Highly sensitive radio occultation and white light measurements of path-integrated density have shown that the solar corona comprises three distinct morphological regions, streamer, quiet Sun, and polar coronal hole, which except for the streamer region, extend radially into interplanetary space from 1.15 R***s*** to at least 30 R***s***. The authors build on these results by comparing solar wind flow speeds observed at the same time as path-integrated density.

solar↗
NASA NTRS2013

STEREO and Wind Observations of Intense Cyclotron Harmonic Waves at the Earth's Bow Shock and Inside the Magnetosheath

We present the first observations of electron cyclotron harmonic waves at the Earth's bow shock from STEREO and Wind burst waveform captures. These waves are observed at magnetic field gradients at a variety of shock geometries ranging from quasi-parallel to nearly perpendicular along with whistler mode waves, ion acoustic waves, and electrostatic solitary waves. Large amplitude cyclotron harmonic waveforms are also observed in the magnetosheath in association with magnetic field gradients convected past the bow shock. Amplitudes of the cyclotron harmonic waves range from a few tens to more than 500 millivolts/meter peak-peak. A comparison between the short (15 meters) and long (100 meters) Wind spin plane antennas shows a similar response at low harmonics and a stronger response on the short antenna at higher harmonics. This indicates that wavelengths are not significantly larger than 100 meters, consistent with the electron cyclotron radius. Waveforms are broadband and polarizations are distinctively comma-shaped with significant power both perpendicular and parallel to the magnetic field. Harmonics tend to be more prominent in the perpendicular directions. These observations indicate that the waves consist of a combination of perpendicular Bernstein waves and field-aligned waves without harmonics. A likely source is the electron cyclotron drift instability which is a coupling between Bernstein and ion acoustic waves. These waves are the most common type of high-frequency wave seen by STEREO during bow shock crossings and magnetosheath traversals and our observations suggest that they are an important component of the high-frequency turbulent spectrum in these regions.

bow shock↗
NASA NTRS1976

Simultaneous partial reflection and meteor radar wind observations at Urbana, Illinois, during the winter of 1974-1975

A program of observation was undertaken during the winter of 1974-1975 utilizing the meteor winds radar and partial reflection system at Urbana, Illinois. The north-south component of the prevailing wind representative of 80-100 km altitude was deduced for four 24-h observational periods during which partial reflection measurements of D-region electron density were made. These observations indicate southward mean motion during periods of higher electron density and northward mean motion during periods of lower electron density. This is consistent with the idea that increases in the transport of nitric oxide from the auroral zone is a cause of winter increases in D-region electron density at midlatitudes.

Geller, M. A.↗
NASA NTRS1988

Moored surface wind observations at four sites along the Pacific equator between 140 and 95 deg W

Moored surface wind measurements were recorded along the Pacific equator at 140, 124, 110, and 95 deg W during portions of 1980-1985. Minimum record length is one year. The annual mean and monthly mean westward speeds at 110 deg W were about 1.5 m/s higher during the year preceding the 1982-1983 El Nino than in the year following this event. The annual cycle, which moved westward at about 0.8 m/s, consisted of weak westward and northward speeds in February-April and vice versa in September-October. The spectral slope between 5-day and 0.05-day periods was -1.5. The rms amplitude of the 95-percent statistically significant diurnal period oscillation was 0.3 m/s, and the meridional component was nearly twice as large as the zonal component. The diurnal period wave was coherent (at the 95-percent confidence level) between 95 and 124 deg W, with westward phase propagation of about 138 m/s. No statistically significant spectral peak was found in the 40- to 50-day intraseasonal period band. The surface zonal ocean current component, which reached approximately 0.5 and -0.5 m/s in April and October, respectively at 110 deg W, influenced the surface wind stress computed from the quadratic bulk aerodynamic formulation by 10-20 percent.

Halpern, David↗
NASA NTRS1984

NROSS scatterometer - An instrument for global oceanic wind observations

One of the instruments - the NROSS scatterometer or SCATT - to be launched on the Navy Remote Ocean Sensing System spacecraft in 1989 is discussed. To determine wind speed and direction that SCATT will measure the ocean normalized radar cross section (NRCS) by illuminating the ocean's surface with microwave pulses and measuring the return signal power. A wind retrieval algorithm is used to compute the wind speed and direction from the measured NRCS. Winds over at least 90 percent of the global, ice-free ocean will be observed at least once every two days. For NASA users, the system will retrieve winds with an accuracy of plus or minus 2 m/s or 10 percent whichever is greater, for wind speeds ranging from 3 to 30 m/s.

Li, F.↗
NASA NTRS2019

Validation of Satellite-Based Wind Observations During PISTON

PISTON cruises provide a useful and unique suite of measurements relevant to validating satellite-based ocean wind datasets near tropical convection. In this talk, we will focus on opportunities for using PISTON observations to validate two different scatterometer datasets: (1) Cyclone Global Navigation Satellite System (CYGNSS) (2) Advanced Scatterometer (ASCAT).

Lang, Timothy↗
NASA NTRS2000

Coincident POLAR/UVI and WIND Observations of Pseudobreakups

Using POLAR/UVI global images, we have identified a period of successive minor auroral activations during which WIND was making a perigee pass (X approx. - 11Re). These auroral brightenings are interpreted to be pseudobreakups due to the lack of global expansion. Large magnetic field fluctuations and high earthward ion velocity moments measured by the WIND spacecraft show a nearly one-to-one correspondence with the auroral intensifications. Analysis of the plasma parameters indicates that there is no difference in the behavior of the plasma during pseudobreakups as compared to substorm expansive phase onset. Inspection of the ion distribution functions during high velocity moment events reveals the presence of a two component plasma. The particles contributing to the large mean velocities are energetic ions from approx. 2-27 keV. We conclude that pseudobreakups are the ionospheric signature of high velocity moment events.

Fillingim, M. O.↗
NASA NTRS1989

Solar wind observations with the ion composition instrument aboard the ISEE-3 ICE spacecraft

The principal observations obtained by the Ion Composition Instrument (ICI) flown on the ISEE-3/ICE spacecraft, which was in the solar wind from September 1978 to the end of 1982, before being directed to the far magnetotail of the Earth are discussed. Almost continuous observations were made of the abundances of 3He++, 4He++, O6+, O7+, Ne, Si and Fe in various charge states, and of their bulk speeds and temperatures. The results show that there is a strong tendency in the collisionless solar wind for the ionic temperatures to be proportional to the masses. For heavier ions these temperatures exceed typical coronal electron temperatures. 4He++, especially in high speed streams, moves faster than H+, and travels at the same speed as heavier ions. The mechanism leading to this heating and rapid streaming is still not entirely clear.

Ogilvie, K. W.↗
NASA NTRS1989

Solar wind observations with the ion composition instrument aboard the ISEE-3/ICE spacecraft

The principal observations obtained by the Ion Composition Instrument (ICI) flown on the ISEE-3/ICE spacecraft, which was in the solar wind from September 1978 to the end of 1982, before being directed to the far magnetotail of the Earth are discussed. Almost continuous observations were made of the abundances of 3He++, 4He++, 06+, 07+, Ne, Si and Fe in various charge states, and of their bulk speeds and temperatures. The results show that there is a strong tendency in the collisionless solar wind for the ionic temperatures to be proportional to the masses. For heavier ions these temperatures exceed typical coronal electron temperatures. 4He++, especially in high speed streams, moves faster than H+, and travels at the same speed as heavier ions. The mechanism leading to this heating and rapid streaming is still not entirely clear.

Ogilvie, K. W.↗
NASA NTRS1998

Coincident UVI and Wind Observations of Pseudo-Breakups

Using images taken by the Ultraviolet Imager (UVI) onboard the Polar spacecraft, we identify periods of pseudo-breakup activity coincident with perigee passes of the WIND spacecraft through the magnetotail. Previous studies have shown that from both observations on the ground and in the magnetotail there is very little difference phenomenologically between substorm onset and pseudo-breakups except for the degree of localization and the absence of global expansion. This raises the question of what prevents a pseudo-breakup from expanding globally. For the time intervals studied, we find a high correlation between pseudo-breakups and short-lived particle flux enhancements in the magnetotail. The velocity distribution of the plasma during some of these flux enhancements are indicative of bursty bulk flows.

Fillingim, M. O.↗
NASA NTRS1981

Momentum and energy balance in late-type stellar winds

Observations at ultraviolet and X-ray wavelengths indicate that the classical picture of a static stellar atmosphere containing a radiative equilibrium temperature distribution is inapplicable to the majority of late type stars. Mass loss and the presence of atmospheric regions characterized by gas temperatures in excess of the stellar effective temperature appear to be almost ubiquitous throughout the HR diagram. Evidence pertaining to the thermal and dynamical structure of the outer envelopes of cool stars is summarized. These results are compared with the predictions of several theoretical models which were proposed to account for mass loss from latetype stars. Models in which the outflow is thermally radiatively, or wave driven are considered for identification of the physical processes responsible for the observed wind properties. The observed variation of both the wind, thermal and dynamical structure as one proceeds from the supergiant branch toward the main sequence in the cool portion of the HR diagram give consideration to potential mechanisms for heating and cooling the flow from low gravity stars.

Macgregor, K. B.↗
NASA NTRS1995

Alfvenic fluctuations in the solar wind observed by Ulysses

One of the striking results of the Sun's south polar pass by Ulysses was the discovery of large amplitude, long period Alfvenic fluctuations that were continuously present in the solar wind flow from the polar coronal hole. The fluctuations dominate the variances and power spectra at periods greater than or equal to 1 hour and are evident as correlated fluctuations in the magnetic field and solar wind velocity components. Various properties of the fluctuations in the magnetic field, in the velocity, and in the electric field have been established. The waves appear to have important implications for galactic cosmic rays and for the solar wind, topics which have continued to be investigated. Their origin is also under study, specifically whether or not they represent motions of the ends of the field lines at the Sun. The resolution of these issues has benefited from the more recent observations as the spacecraft traveled northward toward the ecliptic and passed into the northern solar hemisphere. All these observations will be presented and their implications will be discussed.

Smith, E. J.↗