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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 757 records · Page 42
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NASA NTRSDate not supplied

NASA Space Radiation Laboratory Galactic Cosmic Ray Simulator

With exciting new Agency plans for a sustainable return to the moon, astronauts will once again leave earth’s protective magnetosphere only to endure higher levels of radiation from galactic cosmic rays (GCR) and the possibility of a large solar particle event (SPE). Gateway, lunar landers, and surface habitats will be designed to protect crew against SPEs with vehicle optimization, storm shelter concepts, and/or active dosimetry; however, the ever-penetrating GCR will continue to pose the most significant health risks especially as lunar missions increase in duration and as NASA sets its aspirations on Mars. The primary risks of concern include carcinogenesis, central nervous system effects resulting in potential in-mission cognitive or behavioral impairment and/or late neurological disorders, degenerative tissue effects including cataracts, circulatory and heart disease, as well as, potential immune system decrements impacting multiple aspects of crew health. Characterization and mitigation of these risks requires a significant reduction in the large biological uncertainties of chronic (low-dose rate) heavy ion exposures and the validation of countermeasures in a relevant space environment. NASA has developed the “GCR Simulator” at Brookhaven National Laboratory to generate a spectrum of ion beams that approximates the primary and secondary GCR field experienced at human organ locations within a deep-space vehicle. The majority of the dose is delivered from protons (~65-75%) and helium ions (~10-20%) with heavier ions (Z>3) contributing the remainder. The “GCR Simulator” exposes state-of-the art cellular and animal model systems to 33 sequential beams including 4 proton energies plus degrader, 4 helium energies plus degrader, and the five heavy ions of C, O, Si, Ti, and Fe. A polyethylene degrader is used with the 100 MeV/n H and He beams to provide a nearly continuous distribution of low energy particles. A 500 mGy exposure, delivering doses from each of the 33 beams, requires 75-90 minutes. To more closely simulate the low dose rates found in space, sequential field exposures can be divided into daily fractions over 2-6 weeks, with individual beam fractions as low as 0.1-0.2 mGy. In the large beam configuration (60 x 60 cm2), 54 special housing cages can accommodate 2-3 mice each for a 70-75 min duration or ~15 individually housed rats. Emerging research results from our 2018 runs utilizing mixed heavy ion fields and protracted space exposures are forthcoming and will deepen our understanding of the numerous health risks faced by astronauts. This talk discusses NASA’s innovative technology solution for a ground-based GCR simulator at the NASA Space Radiation Laboratory to enable future exploration missions.

galactic cosmic ray simulator↗
NASA NTRS2020

Concerning the Interaction of A Transmitted Interplanetary Impulse With A Plasmaspheric Drainage Plume: First Results From 3-D Hybrid Kinetic Modeling

We present a new hybrid kinetic model to simulate the response of plasmaspheric drainage plumes to impulsive interplanetary pressure pulses. Since particle distributions attending the interplanetary pulses and in the drainage plume are non-Maxwellian, wave-particle interactions play a crucial role in energy transport within and outside the plumes. Finite gyroradius effects become important in mass loading of the transmitted impulse with the drainage plume ions. A forward-reverse shock structure develops from the initial step-like transmitted shock. First results show that the impulse causes strong deformations in the global structure of the plume. The anisotropic ion velocity distribution functions at the impulse front and inside the plume help us determine energy transport via wave-particle interactions throughout the Earth’s inner magnetosphere.

A S Lipatov↗
NASA NTRS2022

Review of Solar Energetic Particle Models

Solar Energetic Particle (SEP) events are interesting from a scientific perspective as they are the product of a broad set of physical processes from the corona out through the extent of the heliosphere, and provide insight into processes of particle acceleration and transport that are widely applicable in astrophysics. From the operations perspective, SEP events pose a radiation hazard for aviation, electronics in space, and human space exploration, in particular for missions outside of the Earth’s protective magnetosphere including to the Moon and Mars. Thus, it is critical to improve the scientific understanding of SEP events and use this understanding to develop and improve SEP forecasting capabilities to support operations. Many SEP models exist or are in development using a wide variety of approaches and with differing goals. These include computationally intensive physics-based models, fast and light empirical models, machine learning-based models, and mixed-model approaches. The aim of this paper is to summarize all of the SEP models currently developed in the scientific community, including a description of model approach, inputs and outputs, free parameters, and any published validations or comparisons with data.

Kathryn Whitman↗
NASA NTRSDate not supplied

SPHINX: An SEP Model Validation Infrastructure developed through Community Challenges and the SEP Scoreboards

Solar Energetic Particle (SEP) events are interesting from a scientific perspective as they are the product of a broad set of physical processes from the corona out through the extent of the heliosphere, and provide insight into processes of particle acceleration and transport that are widely applicable in astrophysics. From the operations perspective, SEP events pose a radiation hazard for aviation, electronics in space, and human space exploration, in particular for missions outside of the Earth’s protective magnetosphere including to the Moon and Mars (Whitman et al 2022). For these reasons, SEP modelers have developed a rich and diverse set of models with a wide variety of aims. Some models probe the basic physics at the heart of particle acceleration and transport. Others produce fast statistical forecasts or employ disruptive new techniques like Machine Learning with the goal to assist end users in making operational decisions. To enable a consistent and quantitative understanding of SEP model performance, a generalized, automated validation infrastructure, called SPHINX, is being developed at NASA SRAG in close collaboration with NASA CCMC, NASA M2M, NOAA SWPC, and BIRA-IASB. This infrastructure has been built up through a multi-year community challenge. Starting in 2018 at the SHINE workshop, an effort was launched through SHINE, ISWAT, and ESWW to encourage quantitative, comprehensive, and consistent validation of SEP models. This effort has defined a set of challenge SEP events with the aim of generating quantitative comparisons between forecasts and observations and a set of challenge “non-events” to assess false alarms. In 2023, these challenge lists have been extended to statistically significant numbers with a prescribed set of rules for producing forecasts and supported through the dedicated SEPVAL working meetings. The participation of the research community has allowed the infrastructure to validate all the types of outputs being produced by SEP models. In parallel, the SPHINX code is being applied to real time forecasts submitted to the SEP Scoreboards, ensuring that the validation infrastructure can interpret forecasts produced in an operational scenario and provide metrics meaningful for operations. Upon completion, SPHINX and its interactive user interface, SPHINX-Web, will be made available for public use.

space weather↗
NASA NTRS1965

Earth's magnetic field

Dipole field, magnetosphere, quiet day geomagnetic variations, dynamo theory for ionosphere origin, and other topics related to earth magnetic field

MAGNETOSPHERE↗
NASA NTRS1981

Low-energy charged particles in Saturn's magnetosphere - Results from Voyager 1

The Voyager 1 low-energy charged particle instrument measured electrons and ions with energies below 26 and 40 kiloelectron volts, respectively, in the Saturn magnetosphere. Spectra of all ion species were found to have an energy cutoff at levels greater than 2 million electron volts. In contrast to the magnetospheres of Jupiter and earth, there are no lobe regions essentially devoid of particles in Saturn's nighttime magnetosphere. One novel feature of the Saturn magnetosphere is a pervasive population of energetic molecular hydrogen.

Krimigis, S. M.↗
NASA NTRS1973

Electron pitch angle distributions throughout the magnetosphere as observed on Ogo 5.

A survey of the equatorial pitch angle distributions of energetic electrons is provided for all local times out to radial distances of 20 earth radii on the night side of the earth and to the magnetopause on the day side of the earth. In much of the inner magnetosphere and in the outer magnetosphere on the day side of the earth, the normal loss cone distribution prevails. The effects of drift shell splitting - i.e., the appearance of pitch angle distributions with minimums at 90 deg, called butterfly distributions - become apparent in the early afternoon magnetosphere at extended distances, and the distribution is observed in to 5.5 earth radii in the nighttime magnetosphere. Inside about 9 earth radii the pitch angle effects are quite energy-dependent. Beyond about 9 earth radii in the premidnight magnetosphere during quiet times the butterfly distribution is often observed. It is shown that these electrons cannot survive a drift to dawn without being considerably modified. The role of substorm activity in modifying these distributions is identified.

West, H. I., Jr.↗
NASA NTRS1981

Magnetic fields and charged particles around major planets and their satellites

It is noted that whereas Jupiter and Saturn have magnetospheres whose large-scale structure can be understood by analogy with earth, the ways in which the magnetospheres differ are of great interest. At earth, large-scale processes are dominated by convective flows of plasma driven by the solar wind. At Jupiter, centrifugal effects that are driven by planetary rotation are critical. Magnetic particle sources include not only the ionosphere and solar wind (as at earth) but also satellites and rings. The internal planetary magnetic moments controlling the scale of the magnetosphere differ by orders of magnitude between Jupiter and earth. It is pointed out that where the magnetic moments have been modeled from spacecraft data, the restricted spatial sampling has biased the results and limited confidence in details of the models. Voyager data suggest that Io may itself be magnetized and surrounded by an entirely unfamiliar type of magnetosphere.

Kivelson, M. G.↗
NASA NTRS2022

The Earth's Exosphere and Its Response to Space Weather

Neutral-Plasma charge exchange is a fundamental physical process that occurs ubiquitously across the universe. In geospace, charge exchange occurs in the Earth’s topside ionosphere, polar wind, plasmasphere, inner magnetosphere, and magnetosheath. Past and current space missions have profiled plasma and electromagnetic characteristics in various parts of the Earth’s magnetospheric system. However, observations of the exosphere, i.e., neutrals above 500 km altitude, are still sparse and, in some regions, non-existent, which limits our understanding of the neutral contribution to the overall dynamics of the geospace environment. Cold exospheric neutrals (< 10 eV) play an important role in the Sun-Earth interaction. Variability of exospheric density provides key information of the Earth’s atmospheric loss under dynamic space environment conditions. Various neutral species and their density variations in the polar wind can alter ion outflow patterns, modifying global magnetospheric dynamics. Exospheric neutrals also provide an energy sink for the inner magnetosphere by creating Energetic Neutral Atoms (ENAs) through charge exchange with high-energy ring current ions, which subsequently leave our geospace system unimpeded by magnetic fields. Exospheric neutrals also provide a means to observe the global interaction of the solar wind – magnetosphere, through global imaging of the system via ENAs (e.g., the TWINS and IMAGE missions) and soft X-rays (e.g., the upcoming LEXI and SMILE missions), the byproducts of neutral-plasma charge exchange. In the coming decade, we advocate that our community needs to increase our exploration of the neutral populations in the outermost reaches of the Earth’s atmosphere. It is imperative that we improve both in-situ and remote-sensing technologies for measuring key neutral species in our exosphere. We also encourage dedicated exosphere missions and to stimulate model developments of our exosphere and its interaction with the co-located magnetospheric system and neighboring Ionosphere - Thermosphere - Mesosphere system.

Hyunju Connor↗
NASA NTRS1997

Local and Global Studies of Ion Outflow From the High Latitude Ionosphere

Ion outflow from the ionosphere plays a fundamental but poorly defined role in magnetospheric processes. The purpose of the research is to better understand the mass coupling between the Earth's ionosphere and Magnetosphere. The work performed under this grant falls in three areas: (1) event studies using archived data from the DE-1/2 satellites; (2) investigations using Data from the ISTP satellites; and (3) work supporting a Space Physics Educational Outreach (SPEO) grant supplement.

Petersen, W. K.↗
NASA NTRS1985

Particle behavior in the magnetosphere

The Rice Convection Model deals with large-scale processes in the earth's inner and middle magnetosphere, including coupling to the ionosphere. Starting from appropriate initial and boundary conditions, the model computes the following physical parameters: ionospheric electric fields and currents; magnetospheric particle distributions, electric fields, and electric currents; and magnetic-field-aligned (Birkeland) currents connecting the two regions. This paper evaluates work on the model, with emphasis on the assumptions made, the basic equations, and the numerical methods. The theoretical basis of the model is compared and contrasted with standard magnetohydrodynamics. The limitations imposed by the major assumptions are discussed. Model inputs and boundary conditions are listed, and the methods of specifying them discussed. Some physical conclusions and insights that have been gained from the model are listed and described very briefly. References are given to published discussions of the major points of physics.

Wolf, R. A.↗
NASA NTRS2018

Intense Electric Fields and Electron-Scale Substructure Within Magnetotail Flux Ropes as Revealed by the Magnetospheric Multiscale Mission

Three flux ropes associated with near-Earth magnetotail reconnection are analyzed using Magnetospheric Multiscale observations. The flux ropes are Earthward propagating with sizes from ∼3 to 11 ion inertial lengths. Significantly different axial orientations are observed, suggesting spatiotemporal variability in the reconnection and/or flux rope dynamics. An electron-scale vortex, associated with one of the most intense electric fields (E) in the event, is observed within one of the flux ropes. This E is predominantly perpendicular to the magnetic field (B); the electron vortex is frozen-in with E × B drifting electrons carrying perpendicular current and causing a small-scale magnetic enhancement. The vortex is ∼16 electron gyroradii in size perpendicular to B and potentially elongated parallel to B. The need to decouple the frozen-in vortical motion from the surrounding plasma implies a parallel E at the structure's ends. The formation of frozen-in electron vortices within reconnection-generated flux ropes may have implications for particle acceleration.

Magnetospheric Multiscale↗
NASA NTRS1993

ULF waves in other magnetospheres - observations and possible source mechanisms

Five other planets besides the Earth (Mercury, Jupiter, Saturn, Uranus and Neptune) in our solar system are now known to possess internal magnetic fields. The exploration of these planets by the Mariner, Pioneer, Voyager and Ulysses spacecraft has revealed that all of them possess fully expressed magnetospheres which share several similarities in their structures with the Earth's magnetosphere. This paper presents an overview of the work done so far in the field of the ULF waves in the magnetospheres of Mercury, Jupiter, Saturn and Uranus. To give an idea of the expected wave periods, gyroperiods of the dominant ion species and the fundamental periods of the standing Alfven waves are presented as functions of L parameter in these magnetospheres. In the magnetosphere of Mercury, ULF waves were observed in the vicinity of the magnetopause and in the inner magnetosphere with frequencies in the range of 0.1-0.5 Hz. In the magnetosphere of Jupiter, at least three different types of wave sources are observed. Near the dayside and the dawn magnetopause, waves with periods 5-20 min and amplitudes between 5 and 10 nT are observed which may be caused by an interaction between the corotating outflowing plasma and the antisunward moving plasma from the magnetosheath. In Saturn's magnetosphere, ULF waves have been observed to be strongly confined to the plasma sheet and have wave periods in the range of 5-60 minutes. The calculated fundamental has a wave period of 5-6 hours in the region where these waves were observed. The ULF waves have extremely small amplitudes (approximately = 0.3 nT) in the magnetosphere of Uranus. These waves were also seen to be confined to the low magnitude latitudes and have periods much shorter than that of the fundamental of a standing Alfven wave.

Khurana, K. K.↗
NASA NTRS2011

Upstream Structures and Their Effects on the Magnetosphere

Kinetic processes within the Earth's foreshock generate a profusion of plasma and magnetic field structures with sizes and durations ranging from the microscale (e.g. SLAMs, solitons, and density holes) to the mesoscale (e.g. foreshock cavities or boundaries, hot flow anomalies, and bubbles). Swept into the bow shock by the solar wind flow, the perturbations associated with these features batter the magnetosphere, driving a wide variety of magnetospheric effects, including large amplitude magnetopause motion, bursty reconnection and the generation of flux transfer events, enhanced pulsation activity within the magnetosphere, diffusion and energization of radiation belt particles, enhanced particle precipitation resulting in dayside aurora and riometer absorption, and the generation of field-aligned currents and magnetic impulse events in high-latitude ground magnetometers. This talk reviews the ever growing menagery of structures observed upstream from the bow shock, examines their possible interrelationships, and considers their magnetospheric consequences.

Sibeck, D. G.↗
NASA NTRSDate not supplied

Auroral Electron Estimates From the Voyager 2 Plasma Observations During the Uranus Flyby and Comparisons to Earths Aurora

Introduction: We are fortunate enough to have plasma observations from the Voyager 2 flyby of Uranus in 1986. We revisit these data in the context of estimating what the auroral electrons in Uranus’ magnetosphere would look like and how they would compare to what we know about Earth’s aurora and how it is coupled to Earth’s magnetosphere. The Voyager 2 flyby of Uranus provided us with valua-ble information about the plasma environment in-side the magnetosphere of Uranus (Sittler, et al., 1987). The maximum energy of the Voyager 2 plasma instrument was 6 keV for electrons and it is clear from the data that the electron fluxes extended be-yond that range to higher energies. Future meas-urements should extend up to around 30 keV in or-der to fully capture the full electron distribution within the magnetosphere and those corresponding to the aurora. The electron temperatures were around 2 keV throughout the magnetosphere of Uranus and the densities ranged from 0.001 to 1.0 per cubic centimeter. These observed parameters will be compared to analogous structures within Earth’s magnetosphere and be used to estimate the energy and fluxes of electrons that would be observed within the auroral zones on Uranus.

R G Michell↗
NASA NTRS2002

Theoretical Technology Research for the International Solar Terrestrial Physics (ISTP) Program

During the last four years the UCLA (University of California, Los Angeles) IGPP (Institute of Geophysics and Planetary Physics) Space Plasma Simulation Group has continued its theoretical effort to develop a Mission Oriented Theory (MOT) for the International Solar Terrestrial Physics (ISTP) program. This effort has been based on a combination of approaches: analytical theory, large-scale kinetic (LSK) calculations, global magnetohydrodynamic (MHD) simulations and self-consistent plasma kinetic (SCK) simulations. These models have been used to formulate a global interpretation of local measurements made by the ISTP spacecraft. The regions of applications of the MOT cover most of the magnetosphere: solar wind, low- and high- latitude magnetospheric boundary, near-Earth and distant magnetotail, and auroral region. Most recent investigations include: plasma processes in the electron foreshock, response of the magnetospheric cusp, particle entry in the magnetosphere, sources of observed distribution functions in the magnetotail, transport of oxygen ions, self-consistent evolution of the magnetotail, substorm studies, effects of explosive reconnection, and auroral acceleration simulations. A complete list of the activities completed under the grant follow.

Ashour-Abdalla, Maha↗