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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 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
NASA NTRS2023

Analyses of ∼0.05–2 MeV Ions Associated with the 2022 February 16 Energetic Storm Particle Event Observed By Parker Solar Probe

We present analyses of 0.05–2 MeV ions from the 2022 February 16 energetic storm particle event observed by Parker Solar Probeʼs (PSP) ISeIS/EPI-Lo instrument at 0.35 au from the Sun. This event was characterized by an enhancement in ion fluxes from a quiet background, increasing gradually with time with a nearly flat spectrum, rising sharply near the arrival of the coronal mass ejection (CME)–driven shock, becoming nearly a power-law spectrum, then decaying exponentially afterward, with a rate that was independent of energy. From the observed fluxes, we determine diffusion coefficients, finding that far upstream of the shock the diffusion coefficients are nearly independent of energy, with a value of 10 20 cm 2 s −1 . Near the shock, the diffusion coefficients are more than 1 order of magnitude smaller and increase nearly linearly with energy. We also determine the source of energetic particles, by comparing ratios of the intensities at the shock to estimates of the quiet-time intensity to predictions from diffusive shock acceleration theory. We conclude that the source of energetic ions is mostly the solar wind for this event. We also present potential interpretations of the near-exponential decay of the intensity behind the shock. One possibility we suggest is that the shock was over expanding when it crossed PSP and the energetic particle intensity decreased behind the shock to fill the expanding volume. Over expanding CMEs could well be more common closer to the Sun, and this is an example of such a case.

Interplanetary particle acceleration↗
NASA NTRS1974

A correlation between time-overlapping solar flares and the release of energetic particles

The origin of a large corotating solar particle event in August 1970 is discussed. Proton data from spacecraft at five widely separated heliocentric longitudes are used to identify two distinct release points which are over 100 deg apart in solar longitude. Optical flare data show a high incidence of time-overlapping flares between plage regions close to the two release points, indicating a good connection between them. Unusual X-ray and radio emissions are also observed from these regions. The spectrum of the relativistic electrons in the corotating particle event is represented by a power law with an index gamma equal to approximately -4, considerably steeper than that usually observed from a solar flare. It is concluded that there is a large magnetic loop structure connecting points over 100 deg apart on the sun which is able to trap energetic protons and electrons from an earlier solar flare. Subsequent release of these particles establishes an intense, long-lived corotating event.

Simnett, G. M.↗
NASA NTRS1993

Energetic particle environment in the early solar system - Extremely long pre-compaction meteoritic ages or an enhanced early particle flux

Individual mineral grains from meteorites have been exposed to energetic particles prior to inclusion in the host meteorite matrix, an event which occurred quite early in solar system history. Spallation-produced noble gases in such grains are observed to be orders of magnitude greater in abundance than could be produced after meteorite formation and thus provide a record of precompaction irradiation by energetic particles. If attributed to the contemporary particle environment (current galactic and solar cosmic rays) a minimum exposure time for these grains in the CM parent-body regolith of 150 Myr is obtained, with more realistic models suggesting an active parent body regolith for 300 Myr. Constraints on when meteorite compaction occurred and current models for meteorite evolution suggest that this is unreasonably long, that the time available for exposure to energetic particles on the surface of the parent-body regolith is much less than this. Pre-compaction exposure, compressed into a shorter span of time by constraints on the compaction times of carbonaceous meteorites, would require energetic particle fluxes in excess of those in the contemporary solar system and point toward an active early (T Tauri) sun as its source.

Woolum, Dorothy S.↗
DOE OSTI2025

A Numerical Model for the Dynamics of Pickup Ions Outside the Heliopause and IBEX “Ribbon” Observation

The leading mechanism for the origin of the Interstellar Boundary Explorer (IBEX) “ribbon” of enhanced energetic neutral atoms (ENAs) from the outer heliosphere is the so-called secondary ENA process. In this mechanism, neutralized ions escape the heliosphere, and after several times of charge exchange collision,s some propagate back toward Earth in directions nearly perpendicular to the local interstellar magnetic field. However, the physical processes governing the distribution of the pickup ions (PUIs) outside the heliopause are still unclear. In this study, we build a new global model of the IBEX ribbon, where a key component is to calculate the dynamics of the PUIs outside the heliopause by solving the gyrophase-averaged focused transport equations on top of the background magnetohydrodynamic-kinetic model for the heliosphere-interstellar medium interaction. We discuss how the properties of the simulated ribbon change with different scattering parameters and show simulation results of the ENA sky maps, ribbon centers, ribbon profiles at several azimuthal slices, the ribbon ENA source region, and the velocity distribution of PUIs in the ENA source region for different scattering frequencies. Our results show that the model can provide reasonable ribbon sky maps comparable to the observed ribbon when the PUI mean free path is on the order of several thousand astronomical units.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRSDate not supplied

NAIRAS Model Updates

Explore the source record for details and available documents.

Aviation Radiation↗
NASA NTRS1982

Evidence for solar magnetic loops beyond 1 AU

A description is presented of observations of energetic particles emitted by solar flares into interplanetary magnetic loop-like structures during two different events. In one of these events, the IMP-7 spacecraft detected particles which were injected into an apparently preexisting 'magnetic loop' during the onset of a solar flare particle event. The energetic particles appear to bounce between two magnetic mirrors. During the second event, the spacecraft entered a magnetic field regime where the energetic particle intensities had already reached a characteristic angular distribution indicative of a stably trapped population. Observations of the evolution of the angular distributions of the energetic particle intensities during the solar events reveal the occurrence of unusual particle anisotropies.

Sarris, E. T.↗
NASA NTRS1981

Plasma waves associated with energetic particles streaming into the solar wind from the earth's bow shock

Plasma wave and plasma data from ISEE 1 and 2 are examined. In the upstream solar wind, three dominant types of plasma waves are observed which are associated with energetic particle streams coming from the bow shock: ion acoustic waves, electron plasma oscillations, and whistler mode waves. The ion acoustic waves occur simultaneously with either ion beams or a dispersed ion population in the energy range from 0.5 to greater than 45 keV. The electron plasma oscillations are long-wavelength, nearly monochromatic electrostatic waves which are closely correlated with the flux of low-energy electrons, especially in the 0.2-1.5 keV range. Electromagnetic waves with frequencies below 200 Hz are observed when either ion beams or dispersed ion distributions are present; for these waves the refractive index determined from the wave B to E ratio is consistent with whistler mode radiation.

Anderson, R. R.↗
NASA NTRS2007

SDO Asks: What's The Sun Doing Now?

Solar observations have tended to emphasize events like flares and CMEs, and what leads to these events. The past decade has seen an increasing emphasis on understanding the entire Sun, from the nuclear reactions at the core to the development and loss of magnetic loops in the corona. The Solar Dynamics Observatory (SDO) will return synoptic data, taken at a regular cadence and covering the entire Sun. This means you can still study events, but can also move forward to producing a quantitative model of what the Sun is doing today. The science investigations of SDO will determine how the Sun's magnetic field is generated and structured, how this stored magnetic energy is released into the heliosphere and geospace as the solar wind, energetic particles, and variations in the solar irradiance. How SDO data will transform the study of the Sun and the affect on stellar astrophysics will be discussed.

Pesnell, W. D.↗
NASA NTRS2008

The Solar Dynamics Observatory: Your Eye On The Sun

The Sun hiccups and satellites die. That is what NASA's Living With a Star Program is all about. The Solar Dynamics Observatory (SDO) is the first Space Weather Mission in LWS. SDO's main goal is to understand, driving towards a predictive capability, those solar variations that influence life on Earth and humanity's technological systems. The past decade has seen an increasing emphasis on understanding the entire Sun, from the nuclear reactions at the core to the development and loss of magnetic loops in the corona. SDO's three science investigations (HMI, AIA, and EVE) will determine how the Sun's magnetic field is generated and structured, how this stored magnetic energy is released into the heliosphere and geospace as the solar wind, energetic particles, and variations in the solar irradiance. SDO will return full-disk Dopplergrams, full-disk vector magnetograms, full-disk images at nine E/UV wavelengths, and EUV spectral irradiances, all taken at a rapid cadence. This means you can "observe the database" to study events, but we can also move forward in producing quantitative models of what the Sun is doing today. SDO is scheduled to launch in 2008 on an Atlas V rocket from the Kennedy Space Center, Cape Canaveral, Florida. The satellite will fly in a 28 degree inclined geosynchronous orbit about the longitude of New Mexico, where a dedicated Ka-band ground station will receive the 150 Mbps data flow. How SDO data will transform the study of the Sun and its affect on Space Weather studies will be discussed.

Pesnell, William Dean↗
NASA NTRS2008

The Solar Dynamics Observatory

The Solar Dynamics Observatory (SDO) is the first Space Weather Mission in NASA's Living With a Star Program. SDO's main goal is to understand, driving towards a predictive capability, those solar variations that influence life on Earth and humanity's technological systems. The past decade has seen an increasing emphasis on understanding the entire Sun, from the nuclear reactions at the core to the development and loss of magnetic loops in the corona. SDO's three science investigations (HMI, AIA, and EVE) will determine how the Sun's magnetic field is generated and structured, how this stored magnetic energy is released into the heliosphere and geospace as the solar wind, energetic particles, and variations in the solar irradiance. SDO will return full-disk Dopplergrams, full-disk vector magnetograms, full-disk images at nine EIUV wavelengths, and EUV spectral irradiances, all taken at a rapid cadence. This means you can 'observe the database' to study events, but we can also move forward in producing quantitative models of what the Sun is doing today. SDO is scheduled to launch in 2008 on an Atlas V rocket from the Kennedy Space Center, Cape Canaveral, Florida. The satellite will fly in a 28 degree inclined geosynchronous orbit about the longitude of New Mexico, where a dedicated Ka-band ground station will receive the 150 Mbps data flow. How SDO data will transform the study of the Sun and its affect on Space Weather studies will be discussed.

Pesnell, William D.↗
NASA NTRS2010

The Solar Dynamics Observatory: Your Eye on the Sun

The Solar Dynamics Observatory (SDO) was launched on February 11,2010 into partly cloudy skies over Cape Canaveral, Florida. SDO moved into a 28 degree inclined geosynchronous orbit over the longitude of the ground station in New Mexico. SDO is the first Space Weather Mission in NASA's Living With a Star Program. SDO's main goal is to understand and predict those solar variations that influence life on Earth and our technological systems. The SDO science investigations will determine how the Sun's magnetic field is generated and structured, how this stored magnetic energy is released into the heliosphere as the solar wind, energetic particles, and variations in the solar irradiance. The SDO mission consists of three scientific investigations (AIA, EVE, and HMI), a spacecraft bus, and a dedicated Ka-band ground station to handle the 150 Mbps data flow. SDO continues a long tradition of NASA missions providing calibrated solar spectral irradiance data, in this case using multiple measurements of the irradiance and rocket underflights of the spacecraft. The other instruments on SDO will be used to explain and develop predictive models of the solar spectral irradiance in the extreme ultraviolet. Science teams at LMSAL, LASP, and Stanford are responsible for processing, analyzing, distributing, and archiving the science data. We will talk about the building of SDO, its launch, and the data and science it will provide to NASA.

Pesnell, William Dean↗
NASA NTRS2011

The Solar Dynamics Observatory: Your On-Orbit Eye on the Sun

The Solar Dynamics Observatory (SDO) was launched on February 11, 2010 into the partly cloudy skies above Cape Canaveral, Florida. Over the next month SDO moved into a 28 degree inclined geosynchronous orbit at the longitude of the ground station in New Mexico. SDO is the first Space Weather Mission in NASA's Living With a Star Program. SDO's main goal is to understand and predict those solar variations that influence life on Earth and our technological systems. The SDO science investigations will determine how the Sun's magnetic field is generated and structured, how this stored magnetic energy is released into the heliosphere as the solar wind, energetic particles, and variations in the solar irradiance. The SDO mission consists of three scientific investigations (AIA, EVE, and HMI), a spacecraft bus, and a dedicated Ka-band ground station to handle the 150 Mbps data flow. SDO continues a long tradition of NASA missions providing calibrated solar spectral irradiance data, in this case using multiple measurements of the irradiance and rocket underflights of the spacecraft. The other instruments on SDO will be used to explain and develop predictive models of the solar spectral irradiance in the extreme ultraviolet. Science teams at LMSAL, LASP, and Stanford are responsible for processing, analyzing, distributing, and archiving the science data. We will talk about the launch of SDO and describe the data and science it is providing to NASA.

Pesnell, W. Dean↗
NASA NTRS1985

Radial transport of approximately 1 MeV/nucleon ions during the 22 November 1977 solar particle event

Time intensity profiles of solar flare energetic particle events carry information on the particle injection processes at the Sun, as well as the transport of particles in interplanetary space. However, in order to help identify the individual processes of injection versus transport it is necessary to use observations taken at more than one radial location. Results of such a study concerning the 22 November 1977 solar particle event, observed with instruments at 1.0 and 1.55 AU are presented. The observations are for particles of energies near 1 MeV/nucleon, considerably less than the approx. 10 to 20 MeV/nucleon energies typical of previous radial transport studies. Thus, in the present work it is possible to examine the validity of transport models to considerably lower energies than in previous work.

Mason, G. M.↗
DOE OSTI2025

Predicting cutoff L-shells of solar protons using the GPPSn particle dataset

Solar energetic protons (SEPs) arriving at the Earth trigger severe radiation storms in the near-Earth space, directly impacting space missions operating at various altitudes. Therefore, monitoring SEP events and predicting the penetration depths of solar protons are critical for aerospace sectors. Building on previous efforts, here we demonstrate the feasibility of using proton measurements from the Global Prompt Proton Sensor network (GPPSn), enabled by Los Alamos National Laboratory developed combined X-ray dosimeters aboard GPS satellites, to characterize and predict the penetration of solar protons into the geomagnetic field. The inclined medium-Earth-orbits (MEOs) of the global GPS constellation offer a unique advantage of allowing simultaneous measurements of penetrating solar protons inside both open- and closed-field line regions. Therefore, the L-profiles of ∼10s–100 MeV solar protons and their associated cutoff L-shells can be determined from the GPPSn dataset, using predefined threshold proton flux values rather than traditional flux ratios. After examining a list of SEP event intervals across solar cycles 23, 24 and 25—including the 2024 Mother’s Day superstorm, we showcase how the latest GPPSn proton dataset (release v1.10), reprocessed and calibrated, can not only be used to monitor solar proton distributions inside the dynamic geomagnetic field for individual events, but also to derive a new empirical model linking cutoff L-shells with several key space weather parameters. This newly developed SEPCL-MEO model demonstrates high predictive performance; for example, predictions for > 30 MeV solar protons yield a correlation coefficient of 0.85 and performance efficiency of 0.67 when validated against GPPSn observations. Results from this pilot study underscores the scientific and operational value of the GPPSn dataset, and this dataset—when paired with machine-learning techniques—can play a critical role in observing and predicting the effects of future incoming SEP events, including extreme ones.

58 GEOSCIENCES↗
NASA NTRS1987

Positrons from accelerated particle interactions

Positron production from the decay of radioactive nuclei produced in nuclear interactions of accelerated particles is treated in detail. Laboratory data as well as theoretical considerations are used to construct energy-dependent cross sections for the production of a large number of radioactive positron emitters resulting from proton and alpha-particle interactions with ambient cosmic matter. Using these cross sections, positron production rates are calculated for a variety of energetic particle spectra, assuming solar abundances for both the energetic particles and the ambient medium. These results can be used for the study of astrophysical sites which emit annihilation radiation. In particular, the results have been applied to solar flares, where the observed 0.511 MeV line is shown to be due to positrons resulting from accelerated particle reactions.

Kozlovsky, B.↗
NASA NTRS1991

Solar abundances from gamma-ray spectroscopy - Comparisons with energetic particle, photospheric, and coronal abundances

Accelerated particle and ambient gas abundances have been derived using solar flare gamma-ray spectroscopy. The results with photospheric and coronal abundances, as well as with solar energetic particle abundances. This is the first time that the composition of accelerated particles interacting in an astrophysical source has been compared with the composition of particles escaping from the source. The analysis shows that the derived composition of the accelerated particles is different from the composition of particles observed in large proton flares; rather, it resembles the composition observed in He-3-rich flares. The analysis also suggests an ambient gas composition which differs from the composition of both the photosphere and the corona.

Murphy, R. J.↗