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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 469 records · Page 26
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NASA NTRS1979

Compositions of energetic particle populations in interplanetary space

Study of the compositions of energetic particle populations in interplanetary space is reviewed emphasizing observations of helium and heavier particles with energies below about 10 to 20 MeV/nucleon. Three dominant constituents of interplanetary particles are considered: solar flare particles, co-rotating particle streams, and a so-called 'anomalous cosmic ray' component. The recent discovery of a class of solar flare particle events with heavy elements indicates highly selective solar injection mechanisms. Observations of positive radial intensity gradients and anisotropies in co-rotating particle streams suggest the existence of large-scale interplanetary acceleration in a region extending from about 2 to 4 AU. Although present observations exclude the sun as a direct source of the 'anomalous cosmic ray' component, its origin is still debated.

Gloeckler, G.↗
NASA NTRS1979

Compositions of energetic particle populations in interplanetary space

Observations of helium and heavier particles with energies below about 10 to 20 MeV/nucleon are discussed with emphasis on the composition of solar flare particles, corotating energetic particle streams, and the anomalous cosmic ray component. Future advances expected from results obtained from ISEE -3, Voyager, and the international solar polar spacecraft are reviewed.

Gloeckler, G.↗
NASA NTRS2003

CMEs, the Tail of the Solar Wind Magnetic Field Distribution, and 11-yr Cosmic Ray Modulation at 1 AU

Using a recent classification of the solar wind at 1 AU into its principal components (slow solar wind, high-speed streams, and coronal mass ejections (CMEs) for 1972-2000, we show that the monthly-averaged galactic cosmic ray intensity is anti-correlated with the percentage of time that the Earth is imbedded in CME flows. We suggest that this correlation results primarily from a CME related change in the tail of the distribution function of hourly-averaged values of the solar wind magnetic field (B) between solar minimum and solar maximum. The number of high-B (square proper subset 10 nT) values increases by a factor of approx. 3 from minimum to maximum (from 5% of all hours to 17%), with about two-thirds of this increase due to CMEs. On an hour-to-hour basis, average changes of cosmic ray intensity at Earth become negative for solar wind magnetic field values square proper subset 10 nT.

Cliver, E. W.↗
NASA NTRS1982

Solar wind protons - Three-dimensional velocity distributions and derived plasma parameters measured between 0.3 and 1 AU

Such nonthermal features as temperature anisotropies, heat fluxes, and proton double streams have been observed by a Helios solar probe survey of solar wind three-dimensional proton velocity distributions between 0.3 and 1 AU. It is found that a strong anisotropy in the core of proton distributions, with a temperature that is larger perpendicular rather than parallel to the magnetic field, is a persistent feature of high-speed streams, becoming most pronounced in the perihelion, or about 0.3 AU. Isotropic distributions have been detected only close to, and at, magnetic sector boundaries, and the flattest radial temperature profiles are found in high-speed streams. These observations indicate that local heating or proton heat conduction occurs in the solar wind.

Marsch, E.↗
NASA NTRS2024

A Floor in the Sun's Photospheric Magnetic Field: Implications for an Independent Small-scale Dynamo

Clette recently showed that F 10.7 systematically approaches a quiet Sun daily value of 67 solar flux units (sfu) at solar minima as the number of spotless days on the Sun increases. Previously, a floor of ∼2.8 nT had been proposed for the solar wind (SW) magnetic field strength (B). F 10.7 , which closely tracks the Sun's unsigned photospheric magnetic flux, and SW B exhibit different relationships to their floors at 11 yr solar minima during the last ∼50 yr. While F 10.7 approaches 67 sfu at each minimum, the corresponding SW B is offset above ∼2.8 nT by an amount approximately proportional to the solar polar field strength—which varied by a factor of ∼2.5 during this interval. This difference is substantiated by ∼130 yr of reconstructed F 10.7 (via the range of the diurnal variation of the East-component (rY) of the geomagnetic field) and SW B (based on the interdiurnal variability geomagnetic activity index). For the last ∼60 yr, the contribution of the slow SW to SW B has exhibited a floor-like behavior at ∼2 nT, in contrast to the contributions of coronal mass ejections and high-speed streams that vary with the solar cycle. These observations, as well as recent SW studies based on Parker Solar Probe and Solar Dynamics Observatory data, suggest that (1) the Sun has a small-scale turbulent dynamo that is independent of the 11 yr sunspot cycle; and (2) the small-scale magnetic fields generated by this nonvarying turbulent dynamo maintain a constant open flux carried to the heliosphere by the Sun's floor-like slow SW.

Solar magnetic fields↗
NASA NTRS2014

Spinoff 2013

Topics covered include: Innovative Software Tools Measure Behavioral Alertness; Miniaturized, Portable Sensors Monitor Metabolic Health; Patient Simulators Train Emergency Caregivers; Solar Refrigerators Store Life-Saving Vaccines; Monitors Enable Medication Management in Patients' Homes; Handheld Diagnostic Device Delivers Quick Medical Readings; Experiments Result in Safer, Spin-Resistant Aircraft; Interfaces Visualize Data for Airline Safety, Efficiency; Data Mining Tools Make Flights Safer, More Efficient; NASA Standards Inform Comfortable Car Seats; Heat Shield Paves the Way for Commercial Space; Air Systems Provide Life Support to Miners; Coatings Preserve Metal, Stone, Tile, and Concrete; Robots Spur Software That Lends a Hand; Cloud-Based Data Sharing Connects Emergency Managers; Catalytic Converters Maintain Air Quality in Mines; NASA-Enhanced Water Bottles Filter Water on the Go; Brainwave Monitoring Software Improves Distracted Minds; Thermal Materials Protect Priceless, Personal Keepsakes; Home Air Purifiers Eradicate Harmful Pathogens; Thermal Materials Drive Professional Apparel Line; Radiant Barriers Save Energy in Buildings; Open Source Initiative Powers Real-Time Data Streams; Shuttle Engine Designs Revolutionize Solar Power; Procedure-Authoring Tool Improves Safety on Oil Rigs; Satellite Data Aid Monitoring of Nation's Forests; Mars Technologies Spawn Durable Wind Turbines; Programs Visualize Earth and Space for Interactive Education; Processor Units Reduce Satellite Construction Costs; Software Accelerates Computing Time for Complex Math; Simulation Tools Prevent Signal Interference on Spacecraft; Software Simplifies the Sharing of Numerical Models; Virtual Machine Language Controls Remote Devices; Micro-Accelerometers Monitor Equipment Health; Reactors Save Energy, Costs for Hydrogen Production; Cameras Monitor Spacecraft Integrity to Prevent Failures; Testing Devices Garner Data on Insulation Performance; Smart Sensors Gather Information for Machine Diagnostics; Oxygen Sensors Monitor Bioreactors and Ensure Health and Safety; Vision Algorithms Catch Defects in Screen Displays; and Deformable Mirrors Capture Exoplanet Data, Reflect Lasers.

Source record↗
NASA NTRS2007

A New Source of Space Weather Data

The twin STEREO spacecraft were launched on October 26,2006 and, after spending several weeks in alignment orbits, became operational in heliocentric orbits on January 2 1,2007. The spacecraft are now in orbits similar to Earth's and are separating from each other at a rate of about 45 degrees per year as viewed from the sun. The STEREO spacecraft are each equipped with a complement of EUV, and white light imagers as well as particles and fields in situ instruments and a radio burst tracker. In addition to full resolution data downloaded once per day, each spacecraft broadcasts a real time telemetry 'beacon' stream containing compressed images and typically one minute averages of solar wind measurements and radio intensities. These real time data streams are received by a mix of NOAA and NASA-managed tracking stations and the data is transmitted by these stations to the STEREO Science Center at NASA Goddard Space Flight Center where they are processed into useable parameters with a latency of less than five minutes from receipt. As the two spacecraft recede from the sun-Earth line, triangulation of the imaging and radio measurements should allow better estimate of the speed and direction of coronal mass ejections, allowing a more precise estimate of their arrival at Earth. In situ particles and fields measurements, particularly for the spacecraft (Behind) trailing Earth in its orbit, will sample the solar wind that will eventually co-rotate around to the sun-Earth line. Late in the prime mission when the spacecraft are very far (>90 degrees) from the sun-Earth line, observations from the Behind spacecraft, will be particularly valuable for providing a preview of active regions well beyond the sun's East limb (as seen from Earth). Continually updated STEREO space weather data can be viewed and downloaded at http:/lstereo-ssc.nascom.nasa.govldata/beacon/.

Kaiser, Michael L.↗
NASA NTRS1976

Solar wind structure at large heliocentric distances - An interpretation of Pioneer 10 observations

Examination of hourly values of the solar wind speed observed by the Pioneer 10 spacecraft beyond a heliocentric distance of 4 AU reveals (1) a prevalent 'sawtoothlike' speed-time profile, most speed fluctuations displaying a rapid rise and a much slower decline, and (2) the nearly universal appearance of abrupt (on the 1-hour time resolution of these data) changes in the speed on the rising portions of the speed fluctuations. These previously unreported characteristics, as well as the rate of decay of stream amplitudes derived earlier by Collard and Wolfe, are in general agreement with the predictions of stream propagation models that neglect any conversion of kinetic energy to thermal energy outside of shock fronts. Thus the Pioneer 10 observations give the first confirmation of the general concept of solar wind stream evolution employed in these models, i.e., that solar wind speed inhomogeneities appear to steepen to form shock waves and that the 'wave amplitudes' decay slowly as the shock waves propagate outward from the sun.

Hundhausen, A. J.↗
DOE OSTI2020

The chemical nature of the young 120-Myr-old nearby Pisces–Eridanus stellar stream flowing through the Galactic disc

Recently, a new cylindrical-shaped stream of stars up to 700 pc long was discovered hiding in the Galactic disc using kinematic data enabled by the Gaia mission. This stream of stars, dubbed Pisces–Eridanus (Psc–Eri), was initially thought to be as old as 1 Gyr, yet its stars shared a rotation period distribution consistent with a population that was 120 Myr old. Here, we explore the detailed chemical nature of this stellar stream. We carried out high-resolution spectroscopic follow-up of 42 Psc–Eri stars using McDonald Observatory and combined these data with information for 40 members observed with the low-resolution LAMOST spectroscopic survey. Together, these data enabled us to measure the abundance distribution of light/odd-Z (Li, Na, Al, Sc, V), α (Mg, Si, Ca, Ti), Fe-peak (Cr, Mn, Fe, Co, Ni, Zn), and neutron capture (Sr, Y, Zr, Ba, La, Nd, Eu) elements along the Psc–Eri stream. We find that the stream is (1) near-solar metallicity with [Fe/H] = –0.03 dex and (2) has a metallicity spread of 0.07 dex (or 0.04 dex when outliers are excluded). We also find that (3) the abundance of Li indicates that Psc–Eri is ~120 Myr old, consistent with its gyrochronology age. Additionally, Psc–Eri has (4) [X/Fe] abundance spreads that are just larger than the typical uncertainty in most elements, (5) it is a cylindrical-like system whose outer edges rotate about the centre, and (6) no significant abundance gradients along its major axis except a potentially weak gradient in [Si/Fe]. These results show that Psc–Eri is a uniquely close young chemically interesting laboratory for testing our understanding of star and planet formation.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1979

Modeling the Earth's radiation belts. A review of quantitative data based electron and proton models

The evolution of quantitative models of the trapped radiation belts is traced to show how the knowledge of the various features has developed, or been clarified, by performing the required analysis and synthesis. The Starfish electron injection introduced problems in the time behavior of the inner zone, but this residue decayed away, and a good model of this depletion now exists. The outer zone electrons were handled statistically by a log normal distribution such that above 5 Earth radii there are no long term changes over the solar cycle. The transition region between the two zones presents the most difficulty, therefore the behavior of individual substorms as well as long term changes must be studied. The latest corrections to the electron environment based on new data are outlined. The proton models have evolved to the point where the solar cycle effect at low altitudes is included. Trends for new models are discussed; the feasibility of predicting substorm injections and solar wind high-speed streams make the modeling of individual events a topical activity.

Vette, J. I.↗
NASA NTRS1986

On the initial motion of artificial comets in the AMPTE releases

A model describing the initial Ba(+) cloud noted in the AMPTE program is presented which stresses the diamagnetic aspects of the interaction. Based on the observed magnetic field profile, it is suggested that the Ba(+) gyroradius becomes shorter than the cloud radius, and that the Ba(+) ions are magnetized. Momentum coupling force between the Ba(+) cloud and the solar wind in their relative streaming direction will produce an acceleration drift in the direction identical to the observed motion of the cloud, and the observed acceleration force is used to compute the magnitude of the coupling force and to compare it with other models.

Papadopoulos, K.↗
NASA NTRS1995

An extended structure-function model and its application to the analysis of solar wind intermittency

An extended structure-function model is developed by including the new effect in the p-model of Meneveau and Sreenivasan (1987a), i.e., that the averaged energy cascade rate changes with scale, a situation which has been found to prevail in non-fully-developed turbulence in the inner solar wind. This model is useful for the small-scale fluctuations in the inner heliosphere, where the turbulence is not fully developed and cannot be explained quantitatively by any of the previous intermittency turbulence models. With two model parameters, the intrinsic index of the energy spectrum, alpha and the fragmentation fraction p, the model can fit, for the first time, all the observed scaling exponents of the structure functions, which are calculated for time lags ranging from 81 seconds to 0.7 hours from the Helios solar wind data. From the cases we studied we can establish for p neither a clear radial evolution trend, nor a solar-wind-speed, or stream-structure dependence, or a systematic anisotropy for both the flow velocity and magnetic field component fluctuations. Generally, p has values between 0. 7 and 0.8. However, in some cases in low-speed wind p has somewhat higher values for the magnetic components, especially for the radial component. In high-speed wind, the inferred intrinsic spectral indices (alpha) of the velocity and magnetic field components are about equal, while the experimental spectral indices derived from the observed power spectra differ. The magnetic index is somewhat larger than the index of the velocity spectrum. For magnetic fluctuations in both high- and low-speed winds, the intrinsic exponent alpha has values which are near 1.5, while the observed spectral exponent has much higher values.

Tu, C.-Y.↗
NASA NTRS2006

Capabilities of the Natural Environments Branch at NASA's Marshall Space Flight Center

The Natural Environment Branch at NASA s Marshall Space Flight Center (MSFC) has the responsibility to provide engineering support to programs and projects in natural environments. The Natural Environments Branch (EV13) is responsible for natural environments definitions, modelling, database development and effects assessments. EV13 personnel develop requirements for flight projects and provide operational support for space and launch vehicle systems. To accomplish these responsibilities, Branch . personnel have developed modelling and analytical tools which include planetary atmospheres, meteoroids, ionizing radiation, plasmas and ionospheres, magnetic and gravitational fields, spacecraft charging modelling, and radiation effects on electronic parts. NASA s Meteoroid Environment Office is operated within the EV13 and provides meteoroid engineering models and shower forecasts to spacecraft designers and operators. This paper will describe the capabilities within the Natural Environments Effects Branch including; examples of natural environment definitions, radiation transport, output from the Global Reference Atmosphere Models for Earth, Venus, Mars, Titan, and Neptune), recent NASCAP 2K results from solar sail modelling, and meteor stream models

Edwards, David L.↗
NASA NTRS2013

Electrostatic Solitary Waves in the Solar Wind: Evidence for Instability at Solar Wind Current Sheets

A strong spatial association between bipolar electrostatic solitary waves (ESWs) and magnetic current sheets (CSs) in the solar wind is reported here for the first time. This association requires that the plasma instabilities (e.g., Buneman, electron two stream) which generate ESWs are preferentially localized to solar wind CSs. Distributions of CS properties (including shear angle, thickness, solar wind speed, and vector magnetic field change) are examined for differences between CSs associated with ESWs and randomly chosen CSs. Possible mechanisms for producing ESW-generating instabilities at solar wind CSs are considered, including magnetic reconnection.

Electrostatic Solitary Waves↗
NASA NTRS1990

An estimate of the maximum speed of the solar wind, 1938-1989

In an effort to estimate the highest flow velocity that the solar wind has exhibited at earth during the past 50 years, geomagnetic storms that occurred from 1938 to 1989 were surveyed, and the storms that were preceded by a major proton flare were selected. For each identified flare-storm pair, the average speed ('transit speed') of the associated interplanetary shock from the interval between the flare onset and the sudden commencement of the geomagnetic storm was calculated. In each case, the maximum solar wind flow speed was inferred from an empirical relationship (derived for a sample of recent events) between the shock transit speed and the peak flow velocity of the associated transient stream, obtaining a distribution of maximum solar wind speeds, which presumably corresponds to a sample of the most energetic events of this 50-yr period. Results show no evidence for bulk flow velocities greater than the about 2000 km/sec value deduced by Zastenker et al. (1978) and Grunwaldt (1975) for the August 4, 1972 event.

Cliver, E. W.↗
NASA NTRS1995

Correlated variations in the azimuthal and elevation angles of the interplanetary magnetic field

Analysis of data collected during the in-ecliptic phase of the Ulysses mission shows that there are periods during which deviations from the Parker spiral direction in the azimuthal and elevation angles of the interplanetary magnetic field are correlated. There are a number of solar wind structures which might be expected to introduce such a correlation into the data, e.g., CMEs, Stream-stream interfaces or helicity carried by the solar wind. These potential sources fall into two categories: Those produced at or close to the solar wind source region and those produced by extended interactions as the solar wind expands. We will distinguish the contributions of these two source categories and assess the impact on the evolution on the interplanetary magnetic field.

Murphy, N.↗
NASA NTRS2022

Direct Observations of a Complex Coronal Web Driving Highly Structured Slow Solar Wind

The solar wind is formed by continuous streams of charged particles that escape into the heliosphere from the Sun. Fast wind with speeds more than 500 km s -1 emerges from the interiors of coronal holes. Near the ecliptic plane, fast wind from low-latitude coronal holes is interspersed with a highly structured slow solar wind. The source regions and drivers of this slow wind are poorly understood. Here we report observations from an off-point campaign of the GOES Solar Ultraviolet Imager that reveal a spatially complex web of magnetized plasma structures, over a low-latitude coronal hole active region system, that persistently interact and reconnect in the middle corona. SOHO coronagraphic images show concurrent emergence of slow wind streams over these coronal web structures. With advanced global MHD coronal models, we demonstrate that the observed coronal web is a direct imprint of the magnetic separatrix web (S-web). By revealing a highly dynamic portion of S-web, our observations open a window into important middle coronal processes that appear to play key role in driving structured slow solar wind.

Solar physics↗