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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

The Distribution of Interplanetary Dust between 0.96 and 1.04 au as Inferred from Impacts on the STEREO Spacecraft Observed by the Heliospheric Imagers

The distribution of dust in the ecliptic plane between 0.96 and 1.04 au has been inferred from impacts on the two Solar Terrestrial Relations Observatory (STEREO) spacecraft through observation of secondary particle trails and unexpected off-points in the heliospheric imager (HI) cameras. This study made use of analysis carried out by members of a distributed webbased citizen science project Solar Stormwatch. A comparison between observations of the brightest particle trails and a survey of fainter trails shows consistent distributions. While there is no obvious correlation between this distribution and the occurrence of individual meteor streams at Earth, there are some broad longitudinal features in these distributions that are also observed in sources of the sporadic meteor population. The different position of the HI instrument on the two STEREO spacecraft leads to each sampling different populations of dust particles. The asymmetry in the number of trails seen by each spacecraft and the fact that there are many more unexpected off-points in the HI-B than in HI-A indicates that the majority of impacts are coming from the apex direction. For impacts causing off-points in the HI-B camera, these dust particles are estimated to have masses in excess of 10 (exp−17) kg with radii exceeding 0.1 μm. For off-points observed in the HI-A images, which can only have been caused by particles travelling from the anti-apex direction, the distribution is consistent with that of secondary 'storm' trails observed by HI-B, providing evidence that these trails also result from impacts with primary particles from an anti-apex source. Investigating the mass distribution for the off-points of both HI-A and HI-B, it is apparent that the differential mass index of particles from the apex direction (causing off-points in HI-B) is consistently above 2. This indicates that the majority of the mass is within the smaller particles of this population. In contrast, the differential mass index of particles from the anti-apex direction (causing off-points in HI-A) is consistently below 2, indicating that the majority of the mass is to be found in larger particles of this distribution.

Davis, C. J.↗
NASA NTRS1984

Multiple spacecraft observations of interplanetary shocks Shock-normal oscillations and their effects

Observations of interplanetary shocks with multiple spacecraft and multiple instruments has permitted the determination of their average shock normals with unprecedented accuracy. Nevertheless, there are still local deviations from the best-fit normal. These deviations in general appear to be less than 5 deg but on occasion can be of the order of 20 deg or more. These fluctuating normals and the fluctuating upstream field can cause variations in the downstream field strength even when the upstream field strength is constant. This behavior has important consequences for the appearance of quasi-parallel shocks. Precursor waves which stand on the shock ramp and do not propagate or are not convected across the shock front do not affect the downstream field.

Russell, C. T.↗
NASA NTRS1987

Martian surface physical properties to be derived by radar altimeter on the Mars observer spacecraft

The potential is described of a candidate Mars Observer altimeter for determining dielectric properties of Mars regolith. It is pointed out that it is straightforward to use the time between altimeter pulse trains for passive radiometry (hence dielectric properties) and roughness can be derived. Given the mission plan the whole surface can be mapped at least three times, yielding data on seasonal variability.

Garvin, J. B.↗
NASA NTRS1990

Radiation effects on various optical components for the Mars Observer spacecraft

The performance of selected optical parts of the Mars Observer Laser Altimeter (MOLA) is considered. Test results indicate that Schott RG-830, RG-850 filter glass, and the Rolyn Optics Neutral Density filters are essentially immune to levels of radiation an order of magnitude larger than that expected for the MOLA spacecraft. The Corion LG-840 filters are shown to be relatively safe for this application, but exposures to levels higher than 15 kilo-rads(Si) have a severe effect on this material. The BK-7 prism appears to be acceptable for the relatively benign environment required for MOLA. It is concluded that the optical performance of the components tested is not degraded by exposure to the whole life dose expected for the Mars Observer.

Lowry, Jay H.↗
NASA NTRS1973

Large-scale structure of the interplanetary medium. II - Evolving magnetic configurations deduced from multi-spacecraft observations

Description of a method for constructing large-scale (about 0.25 AU) interplanetary magnetic field lines using only solar wind velocity from well-separated appropriately located spacecraft. The technique is based on 'labeling' the field lines at each spacecraft with their coronal connection longitudes calculated in the EQRH (extrapolated quasi-radial hypervelocity) approximation. Even though the EQRH approximation is most applicable to quasi-steady solar wind, it is proposed that it should also be satisfactorily accurate for moderately evolving conditions. For strongly evolving conditions (e.g., flare-associated plasma) a straightforward correction based on the inferred coronal longitudinal velocity profile is proposed. To illustrate the multispacecraft EQRH technique, a calculation is performed in which the interplanetary field lines in a model evolving solar wind disturbance are deduced from model observations at separated spacecraft. Since the expected agreement is found, data from Pioneers 8 and 9 and Vela are used to construct field lines for an unusually quiet period (Apr. 26-30, 1969) and for a flare-associated disturbance accompanied by a Forbush decrease (Mar. 23-25, 1969).

Nolte, J. T.↗
NASA NTRS2016

Multipoint Spacecraft Observations of Long-Lasting Poloidal Pc4 Pulsations in the Dayside Magnetosphere on 1-2 May 2014

We use magnetic field and plasma observations from the Van Allen Probes, Time History of Events and Macroscale Interactions during Substorms (THEMIS) and Geostationary Operational Environmental Satellite system (GOES) spacecraft to study the spatial and temporal characteristics of long-lasting poloidal Pc4 pulsations in the dayside magnetosphere. The pulsations were observed after the main phase of a moderate storm during low geomagnetic activity. The pulsations occurred during various interplanetary conditions and the solar wind parameters do not seem to control the occurrence of the pulsations. The most striking feature of the Pc4 magnetic field pulsations was their occurrence at similar locations during three of four successive orbits. We used this information to study the latitudinal nodal structure of the pulsations and demonstrated that the latitudinal extent of the magnetic field pulsations did not exceed 2 Earth radii (R(sub E)). A phase shift between the azimuthal and radial components of the electric and magnetic fields was observed from Z(sub SM) = 0.30 R(sub E) to Z(sub SM) = -0.16 R(sub E). We used magnetic and electric field data from Van Allen Probes to determine the structure of ULF waves. We showed that the Pc4 magnetic field pulsations were radially polarized and are the second-mode harmonic waves. We suggest that the spacecraft were near a magnetic field null during the second orbit when they failed to observe the magnetic field pulsations at the local times where pulsations were observed on previous and successive orbits. We investigated the spectral structure of the Pc4 pulsations. Each spacecraft observed a decrease of the dominant period as it moved to a smaller L shell (stronger magnetic field strength). We demonstrated that higher frequencies occurred at times and locations where Alfven velocities were greater, i.e., on Orbit 1. There is some evidence that the periods of the pulsations increased during the plasmasphere refilling following the storm.

Korotova, Galina↗
NASA NTRS2023

Small-Scale Magnetic Flux Ropes in Stream Interaction Regions From Parker Solar Probe and Wind Spacecraft Observations

Using in situ measurements from the Parker Solar Probe and Wind spacecraft, we investigate the small-scale magnetic flux ropes (SFRs) and their properties inside stream interaction regions (SIRs). Within SIRs from ∼0.15 to 1 au, SFRs are found to exist in a wide range of solar wind speeds with more frequent occurrences after the stream interface, and the Alfvénicity of these structures decreases significantly with increasing heliocentric distances. Furthermore, we examine the variation of five corresponding SIRs from the same solar sources. The enhancements of suprathermal electrons within these SIRs persist at 1 au and are observed multiple times. An SFR appears to occur repeatedly with the recurring SIRs and is traversed by the Wind spacecraft at least twice. This set of SFRs has similarities in variations of the magnetic field components, plasma bulk properties, density ratio of solar wind alpha and proton particles, and unidirectional suprathermal electrons. We also show, through the detailed time-series plots and Grad–Shafranov reconstruction results, that they possess the same chirality and carry comparable amounts of magnetic flux. Lastly, we discuss the possibility for these recurring SFRs to be formed via interchange reconnection, maintain the connection with the Sun, and survive up to 1 au.

Solar wind↗
NASA NTRS1990

Spacecraft observations of the interaction of active comets with the solar wind

Six spacecraft encountered two comets during 1985 and 1986, obtaining a wealth of data relative to the plasma processes at work in the interaction of an active comet with the solar wind. A review of what space plasma scientists have learned from these data and of their interpretations is presented. The interaction process begins millions of kilometers from the nucleus where the solar wind first picks up cometary ions that slow down the wind and causes the interplanetary magnetic field to pile up and drape around the comet's ionosphere. Thus the geometry of a comet's plasma tail is defined by this draped field. At Halley the Giotto spacecraft noted a well-defined boundary separating the mixture of solar wind and cometary plasmas and the interplanetary magnetic field from the free-field, almost pure cometary plasma in the inner coma. Additional unexpected features in the inner coma were a flux of fast 'granddaughter' ions and high densities of negative ions. Further details covering pickup ions and plasma waves, mass loading, bow shock, energetic particles, the cometosheath, the ionopause, the plasma tail, and the field-free region are provided.

Neugebauer, M.↗
NASA NTRS1987

Using a horizon sensor for Mars observer spacecraft attitude control

A modified earth horizon sensor design is proposed for the Mars Observer mission. The horizon sensor modification are based on Mars horizon radiance profiles. Attention is given to the Mars Observer's attitude control system, whose primary mode is horizon sensor-based and therefore obviates the use of an onboard spacecraft ephemeris; control accuracy of the order of 10 mrad 3sigma/axis is achieved. The attitude control system's second, celestial-backup mode, wich requires greater operational effort, employs an onboard celestial sensor as the spacecraft ephemeris; its control accuracy is of the order of 8 mrad 3sigma/axis.

Langmaier, J. K.↗
NASA NTRS1979

The magnetic field of Jupiter - A comparison of radio astronomy and spacecraft observations

The inner magnetic field of Jupiter is characterized on the basis of Pioneer 10 and 11 measurements and earth-based decimetric radio observations. The dipole parameters derived from the two data sets are in good agreement. Problems in reconciling asymmetries observed in the earth-based data and the spacecraft data are discussed. Models of synchrotron emission from arbitrary magnetic field configurations and high-resolution maps of the Jovian radiation belts in all polarizations are needed to further understanding of Jupiter's magnetic field

Smith, E. J.↗
NASA NTRS1972

Spacecraft observations of the solar wind composition

Solar wind composition studies by means of plasma analyzers carried on various spacecraft are reviewed. The average ratio of helium to hydrogen over the solar cycle is close to 0.045; values as low as 0.0025 and as high as 0.25 have been observed. High values have been observed following solar flares and interplanetary shock waves when the flare gas driving the shock arrives at the spacecraft. Ions of He-3(+2), O-16(+6), and O-16(+7) have been observed with Vela 3 electrostatic analyzers. Further measurements with Vela 5 analyzers have shown the presence of N-14(+6), Si-28(+7) to Si-28(+9) and Fe-56(+7) to Fe-56(+12) ions. The relative abundance of oxygen, silicon, and iron in the solar wind of July 6, 1969, was 1.00, 0.21, and 0.17, which is very similar to reported values for the corona. The ratio of helium to oxygen is variable; the average value of He/O is close to 100, but values between 30 and 400 have been observed.

Bame, S. J.↗
NASA NTRS1999

Polar Spacecraft Observations of the Turbulent Outer Cusp/Magnetopause Boundary Layer of Earth

The orbit of the Polar spacecraft has been ideally suited for studying the turbulent region of the cusp that is located near or just outside the magnetopause current sheet at 7-9 R(sub E). The wave data obtained in this region show that electromagnetic turbulence is dominant in the frequency range 1-10 Hz. The waves responsible for this turbulence usually propagate perpendicular to the local magnetic field and have an index of refraction that generally falls between the estimated cold plasma theoretical values of the electromagnetic lower hybrid and whistler modes and may be composed of both modes in concert with kinetic Alfven waves and/or fast magnetosonic waves. Fourier spectra of the higher frequency wave data also show the electromagnetic turbulence at frequencies up to and near the electron cyclotron frequency. This higher frequency electromagnetic turbulence is most likely associated with whistler mode waves. The lower hybrid drift and current gradient instabilities are suggested as possible mechanisms for producing the turbulence. The plasma and field environment of this turbulent region is examined and found to be extremely complex. Some of the wave activity is associated with processes occurring locally, such as changes in the DC magnetic field, while others are associated with solar wind and interplanetary magnetic field changes.

Pickett, J. S.↗
NASA NTRS1999

Polar Spacecraft Observations of the Turbulent Outer Cusp/Magnetopause Boundary Layer of Earth

The orbit of the Polar spacecraft has been ideally suited for studying the turbulent region of the cusp that is located near or just outside the magnetopause current sheet at 7-9 R(sub E). The wave data obtained in this region show that electromagnetic turbulence is dominant in the frequency range 1-10 Hz. The waves responsible for this turbulence usually propagate perpendicular to the local magnetic field and have an index of refraction that generally falls between the estimated cold plasma theoretical values of the electromagnetic lower hybrid and whistler modes and may be composed of both modes in concert with kinetic Alfven waves and/or fast magnetosonic waves. Fourier spectra of the higher frequency wave data also show the electromagnetic turbulence at frequencies up to and near the electron cyclotron frequency. This higher frequency electromagnetic turbulence is most likely associated with whistler mode waves. The lower hybrid drift and current gradient instabilities are suggested as possible mechanisms for producing the turbulence. The plasma and field environment of this turbulent region is examined and found to be extremely complex. Some of the wave activity is associated with processes occurring locally, such as changes in the DC magnetic field, while others are associated with solar wind and interplanetary magnetic field changes.

Pickett, J. S.↗
NASA NTRS2006

Multi-Spacecraft Observations of Interplanetary Shock Accelerated Particle Events

We use simultaneous measurements from the Wind and ACE spacecraft to determine the spatial properties of both interplanetary (IP) shocks and the shock-associated energetic particle events. We combine plasma, magnetic field and energetic particle data from ACE and Wind for 124 energetic storm particle (ESP) events from 1998 to 2003 and examine the spatial and temporal variations of these events in the Earth's vicinity. We find that even though the two spacecraft were occasionally separated by more than 400 RE, the plasma, field, and energetic particle time-intensity profiles during the events were very similar. In addition, we find that the ion composition and energy spectra in individual IP shock events are identical at the two spacecraft locations. We also use the fitted shock velocity along the normal from ACE and estimate the shock transit time to Wind location. In general, there is poor agreement between the estimated transit time and the actual measured transit time. Hence, our assumptions that a) the IP shock at 1 AU propagates radially, and/or b) the IP shock is spherically symmetric at 1 AU are not valid. In this paper, we will also study, for the first time, the anisotropy measurements of low-energy IP shock-associated ions at both ACE and Wind. We will then compare these new anisotropy analyses with locally measured shock parameters and identify possible signatures of different shock acceleration processes as predicted by the first-order Fermi and shock-drift models.

Ho, G. C.↗
NASA NTRSDate not supplied

Rapid Succession of Sep Events Associated With A Series of Euv Jets: Solar Orbiter, Stereo-A and Near-Earth Spacecraft Observations

A series of near-relativistic solar electron events was observed on November 9 to 15, 2022 by STEREO-A at 0.96 au, by near-Earth spacecraft such as ACE, Wind and SOHO at ⇠0.99 au, and by Solar Orbiter at heliocentric distances ranging from 0.59 to 0.66 au. At least 22 electron intensity enhancements at energies >10 keV were clearly distinguishable in the particle data collected by the Energetic Particle Detector (EPD) suite of instruments on board Solar Orbiter, with 12 of these events occurring on 11 November 2022. Several of these electron events were accompanied by <10 MeV proton and <⇠2 MeV/n heavy ion intensity enhancements. The origin of this rapid succession of particle events is a series of jet-like eruptions detected in extreme ultraviolet (EUV) observations from the vicinity of active region AR 13141 that were closely associated with type III bursts in the decametric-hectometric range. We find a close association between the EUV jets, type III radio bursts and the release of near relativistic electrons. The events on 9 November and late on 14 November are particularly interesting in that they were just evident at electron energies below ⇠30 keV, were rich in heavy ions with energies below ⇠1 MeV/n, associated with type III radio bursts at frequencies below ⇠1.0 MHz, and originated at EUV solar eruptions lacking a clear jet. By combining remote and in-situ data from the three viewpoints (Solar Orbiter and STEREO-A were ⇠20 degrees and ⇠15 degrees east of Earth, respectively), we analyze the origin of this sequence of events, determine the interplanetary context where they were observed, and investigate the interplanetary transport of electrons to the different spacecraft.

D Loyo↗