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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 919 records · Page 51
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Environmental space hazards - An overview

An overview of space hazards that exist in the geo-lunar environment is given along with specific examples of deleterious effects that can be visited upon a long-term mission-oriented spacecraft system in LEO, GEO, the intervening space, LLO, and the lunar surface. Hazards discussed are categorized as pervasive (radiation), incident specific (meteoroids, monatomic oxygen, thermal gradient and shock, and low earth orbital debris), and chemically corrosive (monatomic oxygen). It is pointed out that, while some of the difficulties encountered are common to all types of propulsion systems, in the interplanetary domain the emphasis shifts from incident specific hazards to the pervasive upsets caused by ionizing and nonionizing radiation.

Bahr, G. K.↗
NASA NTRS1992

Terrestrial Response to Eruptive Solar Flares: Geomagnetic Storms

This paper describes the interplanetary structures that are associated with the large-amplitude and long-duration negative B subscript z fields that are found in the sheath field and/or driver gas regions of the shock and are thought to be the main cause of the intense storms.

solar flares geomagnetic storms magnetic field dat↗
DOE OSTI2025

The 2024 July 16 solar event: a challenge to the coronal mass ejection origin of long-duration gamma-ray flares

We present a multi-spacecraft analysis of the 2024 July 16 long-duration gamma-ray flare (LDGRF) detected by the Large Area Telescope on the Fermi satellite. The measured > 100 MeV γ-ray emission persisted for over seven hours after the flare impulsive phase, and was characterized by photon energies exceeding 1 GeV and a remarkably hard parent-proton spectrum. In contrast, the phenomena related to the coronal mass ejection (CME)-driven shock linked to this eruption were modest, suggesting an inefficient proton acceleration unlikely to achieve energies well above the 300 MeV pion-production threshold to account for the observed γ-ray emission. Specifically, the CME was relatively slow (∼600 km/s) and the accompanying interplanetary type-II/III radio bursts were faint and short-lived, unlike those typically detected during large events. In particular, the type-II emission did not extend to kilohertz frequencies and disappeared ∼5.5 hours prior to the LDGRF end time. Furthermore, the associated solar energetic particle (SEP) event was very weak, short-duration, and limited to a few tens of MeV, even at magnetically well-connected spacecraft. These findings demonstrate that a very fast CME resulting in a high-energy SEP event is not a necessary condition for the occurrence of LDGRFs, challenging the idea that the high-energy γ-ray emission is produced by the back-precipitation of shock-accelerated ions into the solar surface. The alternative origin scenario based on local particle trapping and acceleration in large-scale coronal loops is instead favored by the observation of giant arch-like structures of hot plasma over the source region that persisted for the entire duration of this LDGRF.

Sun: UV radiation↗
DOE OSTI2025

Modeling Particle Acceleration and Release from Solar Eruptions

Determining the relative contribution of solar flares versus coronal mass ejections in large solar energetic particle (SEP) events is a long-standing problem. Flare-accelerated particles may travel through complex magnetic fields in the eruption region and escape into interplanetary space, thereby contributing to large SEP events. The process by which flare accelerated particles are released into the heliosphere is poorly understood and yet is critical to advancing our understanding of SEPs. In this work, we address the release problem by solving the focused transport equation in the context of a 2.5D ARMS magnetohydrodynamic simulation of a breakout coronal mass ejection (CME)/flare event. We find that particles accelerated by flare reconnection can be released into interplanetary space through interchange reconnection between closed and open field lines. These particles can contribute directly to SEP events and may become an important seed population for further acceleration by CME-driven shocks. Additionally, we find that the energetic particle fluxes in the inner heliosphere remain elevated for an extended period, allowing them to contribute to SEP acceleration by subsequent CMEs. This study represents the first direct particle modeling of how flare-accelerated particles can contribute to major SEP events.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1994

3-D simulation of high-latitude interaction regions: Comparison with Ulysses results

A three-dimensional (3-D) magnetohydrodynamic (MHD) numerical model is used to simulate the global evolution of a steady, tilted-dipole solar wind flow configuration similar to that prevalent in interplanetary space in 1993. Systematic latitudinal changes in the structure of a corotating interaction region (CIR) near 5 AU is shown to agree well with recent Ulysses observations. The abrupt disappearance of forward shocks and continued persistence of reverse shocks poleward of the latitude where Ulysses crossed the southern edge of the coronal streamer belt is explained as a natural consequence of the 3-D flow geometry.

Pizzo, V. J.↗
NASA NTRS1999

Cosmic Ray Telescope Experiment (CRT), Pioneer 10/11 Program

In May 1996 the electrical power on Pioneer 10 was no longer adequate to support the Cosmic Ray Telescope Experiment (CRT). In March 1997 ground based operations for the mission were terminated. The 25 years of Pioneer 10 were a remarkable voyage of discovery as it ventured into a vast new unexplored region of space. These observations by the Pioneer experiments led in the development of a new discipline of space science - heliospheric physics. For cosmic ray studies it was an incredible era, leading to the identification of new energetic particle populations and processes and initiating the study of the dynamics and large-scale structure and began the study of the dynamics and large-scale structure of the outer heliosphere. A summary of some of the principal scientific findings of the CRT experiment over this period is given in the next section. Even with the cessation of data from the Pioneer 10/11 mission there remained a great deal of scientific analysis and data archiving that required on the order of an additional three years of effort on the part of the CRT team. We have tried to select those tasks where the P10/11 CRT data have an important role to play. Special emphasis is placed on long-term synoptic studies that make use of the extended temporal and spatial coverage of the missions and the full capabilities of the CRT experiment. The major scientific objectives of this study are: (1) A phenomenological study of the modulation process in the heliosphere, thereby laying the foundation for developing a unified model of cosmic ray modulation over a complete 22 year heliomagnetic cycle; (2) These modulation studies and the temporal changes in the cosmic ray intensities also provide information on the large-scale structure and dynamics of the outer heliosphere; (3) use the galactic and anomalous cosmic ray data from Pioneer 10 to obtain a more accurate estimate of the distance to the modulation boundary and to the termination shock; (4) Use the results from (2) and from temporal variations to determine whether significant modulation occurs in the region of the heliosphere; (5)study the acceleration and transport of low energy solar interplanetary energetic particles and their relation to solar activity and interplanetary phenomena.

McDonald, Frank B.↗
DOE OSTI2022

Inner southern magnetosphere observation of Mercury via SERENA ion sensors in BepiColombo mission

Mercury’s southern inner magnetosphere is an unexplored region as it was not observed by earlier space missions. In October 2021, BepiColombo mission has passed through this region during its first Mercury flyby. Here, we describe the observations of SERENA ion sensors nearby and inside Mercury’s magnetosphere. An intermittent high-energy signal, possibly due to an interplanetary magnetic flux rope, has been observed downstream Mercury, together with low energy solar wind. Low energy ions, possibly due to satellite outgassing, were detected outside the magnetosphere. The dayside magnetopause and bow-shock crossing were much closer to the planet than expected, signature of a highly eroded magnetosphere. Different ion populations have been observed inside the magnetosphere, like low latitude boundary layer at magnetopause inbound and partial ring current at dawn close to the planet. These observations are important for understanding the weak magnetosphere behavior so close to the Sun, revealing details never reached before.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1981

Interplanetary magnetic clouds at 1 AU

Magnetic clouds are defined as regions with a radial dimension approximately 0.25 AU (at 1 AU) in which the magnetic field strength is high and the magnetic field direction changes appreciably by means of rotation of one component of B nearly parallel to a plane. The magnetic field geometry in such a magnetic cloud is consistent with that of a magnetic loop, but it cannot be determined uniquely. Forty-five clouds were identified in interplanetary data obtained near Earth between 1967 and 1978; at least one cloud passed the Earth every three months. Three classes of clouds were identified, corresponding to the association of a cloud with a shock, a stream interface, or a CME. There are approximately equal numbers of clouds in each class, and the three types of clouds might be different manifestations of a coronal transient. The magnetic pressure inside the clouds is higher than the ion pressure and the sum is higher than the pressure of the material outside of the cloud.

Klein, L. W.↗
NASA NTRS1985

Variations in elemental composition of several MEV/nucleon ions observed in interplanetary space

Six years of accumulated ISEE-3 and IMP-8 data to study variations in elemental relative abundances among the different populations of energetic ions seen in interplanetary space are surveyed. Evidence suggesting that heavy ion enrichments may be organized by a rigidity scaling factor A/Z over the range H to Fe is presented. Data to support the hypothesis that shock-associated particles are probably accelerated from ambient energetic fluxes are shown.

Mcguire, R. E.↗
NASA NTRS1985

Lunar and Planetary Science Conference, 16th, Houston, TX, March 11-15, 1985, Proceedings. Part 1

Various papers on lunar studies, meteorites and cosmic dust, Mars, and tektites are presented. The topics discussed include: very high potassium basalt; complications in mare basalt petrogenesis; mare basalt genesis; modeling trace elements and isotopic ratios; Zr-Hf-Ta fractionation during lunar evolution; petrology of the Apollo 12 highland component; petrologic province maps of the lunar highlands derived from orbital geochemical data; petrology and chemistry of Apollo 12 regolith breccias; chemical variability and origin of agglutinitic glass; multistage exposure history of the 74261 soil constituents; and an experimental investigation of agglutinate melting mechanisms; shocked mixtures of sodium and potassium feldspars. Also addressed are: cooling history of some Antarctic ureilites; the Leoville accretionary breccia; ubiquitous brecciation after metamorphism in equilibrated ordinary chondrites; layer silicates in a chondritic porous interplanetary dust particle; estimates of rheological properties for flows on the Martian volcano Ascraeus Mons; the Martian dust storm of Sol 1742; and late Eocene North American microtektites and clinopyroxene-bearing spherules.

Ryder, G.↗
NASA NTRS2011

THEMIS Observations of a Transient Event at the Magnetopause

This study focuses on Time History of Events and Macroscale Interactions During Substorms (THEMIS) observations of a long \duration transient event in the vicinity of the dayside magnetopause at approx.15:34 UT on 18 July 2008 that was characterized by features typical of a magnetospheric flux transfer event (FTE): a bipolar negative-positive 5-7 nT signature in the Bn component, a positive monopolar variation in the Bl and Bm components, a approx.5-7 nT enhancement in the total magnetic field strength, and a transient density and flow enhancement. The interplanetary magnetic field (IMF) was mostly radial and disturbed during the intervals studied; that is, it was favorable for the repeated formation, disappearance and reformation of the foreshock just upstream from the subsolar bow shock. We show that varying IMF directions and solar wind pressures created significant effects that caused the compressions of the magnetosphere and the bow shock and magnetopause motions and triggered the transient event. Global signatures of magnetic impulse events (MIEs) in ground magnetograms during the period suggest a widespread pressure pulse instead of a localized FTE as the cause of the event in the magnetosphere. The directions of propagation and the flow patterns associated with the event also suggest an interpretation in terms of pressure pulses.

Korotova, G. I.↗
NASA NTRS1985

Cosmic-ray picture of the heliosphere

The existing data base on the characteristics of the heliosphere is discussed. It is known that solar gravity is less than necessary to hold all the solar material, and therefore a supersonic solar wind exists. Skylab soft X-ray photographs revealed the existence of coronal holes, which evolve in an 11 yr cycle. It has been proposed that all but the highest energy cosmic rays detected on earth can be attributed to solar and heliospheric origins, a controversial view which requires further empirical and theoretical work on particle acceleration processes and regions of interaction of the solar wind with interplanetary plasma. It is possible that a warped solar current sheet stretches to interplanetary space and organizes the solar magnetic field and thereby guides cosmic rays. An inverse correlation has been identified between the sunspot cycle and cosmic ray intensity. The features and effects of solar flares, subsequent shock waves and high speed particle streams are also discussed.

Venkatesan, D.↗
NASA NTRS1989

Magnetic fields near Mars - First results

The magnetic fields of Mars have been measured from Phobos 2 with high temporal resolution in the tail and down to an 850-km altitude. During four successive highly elliptical orbits, the position of the bow shock as well as that of a transition layer, the 'planetopause', were identified. Subsequent circular orbits at 6000-km altitude provided the first high-resolution data in the planetary tail and indicate that the interplanetary magnetic field mainly controls the magnetic tail. Magnetic turbulence was also detected when the spacecraft crossed the orbit of Phobos, indicating the possible existence of a torus near the orbit of this moon.

Riedler, W.↗
NASA NTRS1992

Nonlinear magnetosonic waves and mirror mode structures in the March 1991 Ulysses interplanetary event

In examining the March 23-25, 1991 Ulysses (2.2 AU) high speed solar wind events, two distinct plasma wave modes are found: steepened magnetosonic waves with whistler precursors and mirror mode structures. These two modes are locally generated by plasma instabilities, presumably associated with anisotropies existing in the energetic shock particles and solar wind plasma, respectively. The magnetosonic waves are generated by a right-hand resonant instability associated with an about 40 keV ion beam. By an extrapolation of the results presented here, assuming microflares and nanoflares at the sun generate shocks in the lower corona and these shocks accelerate energetic ions, it is suggested that the ions, via the right-hand resonant instability, generate magnetosonic waves which steepened to form 'microshocks'. These shocks could, in turn, accelerate more energetic ions, leading to a shock/energetic ion/magnetosonic wave cascade. These newly formed magnetosonic waves and shocks presumably could propagate in a broad range of directions, leading to energy dissipation over a large region of the outer corona.

Tsurutani, Bruce T.↗
NASA NTRS1979

Solar energetic particles - From the corona to the magnetotail

Some new results concerning coronal and interplanetary propagation of energetic particles are discussed in the context of previous and current observations and interpretations. Evidence is presented that the bulk of protons of approximately 1 MeV can be preferentially injected onto interplanetary field lines at coronal longitudes and latitudes well-removed (approximately 60 deg) from the site of the associated active region. For these protons, interplanetary propagation parallel and transverse to the interplanetary field evidently involves little scattering near 1 AU, so that parallel propagation is approximately 'scatter free' and transverse propagation is primarily that due to the E x B drift. Upstream of the earth's bow shock, both intensities and anisotropies of approximately 1-MeV protons and electrons are significantly modified by the magnetosphere, and these effects may provide a probe of the structure of the bow shock and magnetosheath in regions not readily accessible to spacecraft.

Roelof, E. C.↗
NASA NTRS1984

Solar Terrestrial Physics: Present and Future

The following topics relating to solar-terrestrial interactions are considered: (1) reconnection of magnetic fields; (2) particle acceleration; (3) solar magnetic flux; (4) magnetohydrodynamic waves and turbulence in the Sun and interplanetary medium; (5) coupling of the solar wind to the magnetosphere; (6) coronal transients; (7) the connection between the magnetosphere and ionosphere; (8) substorms in the magnetosphere; (9) solar flares and the solar terrestrial environment; (10) shock waves in the solar terrestrial environment; (11) plasma transport and convection at high latitudes; and (12) high latitude ionospheric structure.

Butler, D. M.↗
NASA NTRS1992

Plasma wave profiles of earth's bow shock at low Mach numbers - ISEE 3 observations on the far flank

A survey of selected crossings far downstream from the subsolar shock is presented in which the overall plasma wave (PW) behavior of a selected set of nearly perpendicular crossings and another set of limited Mach number but broad geometry are delinated. The result is a generalizable PW signature, or signatures, of low Mach number shocks and some likely implications of those signatures for the weak shock's plasma physical processes on the flank. The data are found to be consistent with the presence of ion beam interactions producing noise ahead of the shock in the ion acoustic frequency range. The presence or absence, and the amplitudes, of PW activity are explainable by the presence or absence of a population of upstream ions controlled by the component of the interplanetary magnetic field normal to the solar wind flow.

Greenstadt, E. W.↗
NASA NTRS1994

Solar activity and coronal mass ejections on the western hemisphere of the Sun in mid-August 1989: Association with interplanetary observations at the ICE and IMP 8 spacecraft

During the 10-day period from August 12 to 21, 1989, a sequence of coronal mass ejections (CMEs) was observed above the west limb of the Sun by the Solar Maximum Mission (SMM) coronagraph. Most of these CMEs apparently originated in the vicinity of one particularly active region during its passage from near central meridian to behind the west limb of the Sun. We present observations made at 1 AU during this period by the International Cometary Explorer (ICE) (formerly International Sun Earth Explorer-3 (ISEE 3)) and Interplanetary Monitoring Platform (IMP 8) spacecraft which were separated by approximately 75 deg in heliolongitude. Following CMEs on August 12 associated with solar events at approximately W40 deg, IMP 8 (in Earth orbit) detected a strong shock followed by signatures in magnetic field, solar wind plasma, and energetic ion data which suggest that CME-related material ('ejecta') forming the shock driver engulfed the spacecraft. This spacecraft only observed weak shocks, and no ejecta, from later CMEs originating further west of the spacecraft. In contrast ICE, off the west limb at approximately W75 deg, observed the shock from the W40 deg event but failed to encounter the shock driver, whereas clear ejecta signatures were observed following events further west, closer to the spacecraft heliolongitude. The disappearance of these signatures (which include bidirectional energetic ion flows, bidirectional solar wind heat fluxes, quiet, enhanced magnetic fields and anomalously cool plasma) at IMP 8 and their emergence at ICE as the solar source region moved westward supports the association of such signatures with ejecta related to CMEs. The dual-spacecraft observations are also consistent with the conclusion of Richardson and Cane (1993) that ejecta at 1 AU typically extend approximately 50 degs in longitude from the solar source. Some plausible associations between particular intervals of ejecta signatures at ICE and individual CMEs are made. However, these associations are complicated by the large number of CMEs present, by intermittent ICE data coverage, and by uncertainties in the ejecta propagation speeds to the spacecraft.

Richardson, I. G.↗