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At least 235 records · Page 13

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NASA NTRS2012

Space Weathering Investigations Enabled by NASA's Virtual Heliophysical Observatories

Structural and chemical impact of the heliospheric space environment on exposed planetary surfaces and interplanetary dust grains may be generally defined as space weathering . In the inner solar system, from the asteroid belt inwards towards the Sun, the surface regolith structures of airless bodies are primarily determined by cumulative meteoritic impacts over billions of years, but the molecular composition to meters in depth can be substantially modified by irradiation effects. Plasma ions at eV to keV energies may both erode uppermost surfaces by sputtering, and implant or locally produce exogenic material, e.g. He-3 and H2O, while more energetic ions drive molecular change through electronic ionization. Galactic cosmic ray ions and more energetic solar ions can impact chemistry to meters in depth. High energy cosmic ray interactions produce showers of secondary particles and energetic photons that present hazards for robotic and human exploration missions but also enable detection of potentially useable resources such as water ice, oxygen, and many other elements. Surface sputtering also makes ejected elemental and molecular species accessible for in-situ compositional analysis by spacecraft with ion and neutral mass spectrometers. Modeling of relative impacts for these various space weathering processes requires knowledge of the incident species-resolved ion flux spectra at plasma to cosmic ray energies and as integrated over varying time scales. Although the main drivers for investigations of these processes come from NASA's planetary science and human exploration programs, the NASA heliophysics program provides the requisite data measurement and modeling resources to enable specification of the field & plasma and energetic particle irradiation environments for application to space weather and surface weathering investigations. The Virtual Heliospheric Observatory (VHO), Virtual Energetic Particle Observatory (VEPO), Lunar Solar Origins Exploration (LunaSOX), and Space Physics Data Facility (SPDF) services now provide a wide range of inner heliospheric spacecraft data that can be applied to space weathering of potential exploration destinations including the Moon, asteroids, and the moons of Mars, as well to radiation hazard assessment for the spacecraft and human explorers. For example, the new VEPO service for time-averaging of multi-source ion flux spectra enables the specification of composite flux spectra from a variety of ongoing and legacy missions for applications to surface interaction modeling. Apollo to Artemis data resources of LunaSOX enable specific space weathering investigations for the Moon, while VHO more generally covers the space field and plasma environments of the inner and outer solar system from the sunward-most perihelia of the twin Helios spacecraft to the ongoing heliosheath passages of the twin Voyagers. Composite multi-source spectra from VEPO can also be applied to the continuing compilation of accumulated 1-AU fluence spectra, mostly contributed by solar wind plasma and energetic particle events, for determination of time-averaged particle compositional and kinetic energy output from the Sun and for modeling of long-term irradiation impacts on planetary surfaces.

Cooper, John F.↗

DOE OSTI2022

Orbit tomography of energetic particle distribution functions

Both fast ions and runaway electrons are described by distribution functions, the understanding of which are of critical importance for the success of future fusion devices such as ITER. Typically, energetic particle diagnostics are only sensitive to a limited subsection of the energetic particle phase-space which is often insufficient for model validation. However, previous publications show that multiple measurements of a single spatially localized volume can be used to reconstruct a distribution function of the energetic particle velocity-space by using the diagnostics' velocity-space weight functions, i.e. velocity-space Tomography. In this work we use the recently formulated orbit weight functions to remove the restriction of spatially localized measurements and present orbit tomography, which is used to reconstruct the 3D phase-space distribution of all energetic particle orbits in the plasma. Through a transformation of the orbit distribution, the full energetic particle distribution function can be determined in the standard {energy, pitch, r, z}-space. We benchmark the technique by reconstructing the fast-ion distribution function of an MHD-quiescent DIII-D discharge using synthetic and experimental FIDA measurements. We also use the method to study the redistribution of fast ions during a sawtooth crash at ASDEX upgrade using FIDA measurements. Lastly, a comparison between the orbit tomography and velocity-space tomography is shown.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

NASA NTRS1994

Engineering Ulysses extended mission

The Ulysses Mission is a collaboration between the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA). The mission is unique, enabling exploration of the heliosphere within a few astronomical units of the Sun over a full range of heliographic latitudes adding a third dimension to our understanding of the Solar System. The advanced scientific instrumentation on Ulysses continually measures the properties of the heliospheric magnetic field, the solar wind, solar radio bursts and plasma waves, galactic cosmic rays, energetic particles, solar X-rays, and interstellar neutral gas. By the end of 1995, the spacecraft will have completed measurements at heliographic latitudes up to 80 degrees over a single orbit of the Sun. The properties of the heliosphere are solar cycle dependent, and Ulysses' first orbit of the Sun will have taken place around a solar minimum. In order to characterize the heliosphere over a full (11 year) solar cycle, it is desirable to continue measurements over a second orbit of the Sun, a new Odyssey that will extend through 2001. Since the spacecraft was only designed for a five-year mission, a number of technical challenges have been surmounted in order to demonstrate the engineering feasibility of this unparalleled scientific opportunity. This paper describes the changes that were necessary to the Ulysses mission engineering and mission operations in order to ensure continual, effective payload operation throughout 1996-2001.

Standley, Shaun↗

DOE OSTI2021

2D measurements of parallel counter-streaming flows in the W7-X scrape-off layer for attached and detached plasmas

Abstract Investigations of particle parallel flow velocities have been carried out for the scrape-off layer (SOL) of the Wendelstein 7-X (W7-X) stellarator, in order to gain insights on the SOL transport properties during attached and detached plasma scenarios. The experimental evidence is based on the coherence imaging spectroscopy (CIS) diagnostic, able to measure 2D impurity emission intensity and flow velocity. The impurity monitored by CIS is C 2+ , characterized by a line-emission intensity observed to be linearly proportional to the total plasma radiated power in both attached and detached plasmas. The related C 2+ velocity shows a strong dependence on the line-averaged electron density while remaining insensitive to the input power. During attached plasmas, the velocity increases with increasing line-averaged density. The tendency reverses in the transition to and during detachment, in which the velocity decreases by at least a factor of 2. The sharp drop in velocity, together with a rise in line-emission intensity, is reliably correlated to the detachment transition and can therefore be used as one of its signatures. The impurity flow velocity appears to be well coupled with the main ions’ one, thus implying the dominant role of impurity-main ion friction in the parallelimpurity transport dynamics. In view of this SOL impurity transport regime, the CIS measurement results are here interpreted with the help of EMC3-Eirene simulations, and their major trends are already explainable with a simple 1D fluid model.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

NASA NTRS1994

Ionospheric footprint of magnetosheathlike particle precipitation observed by an incoherent scatter radar

We have examined Sondrestrom incoherent scatter radar observations of ionospheric plasma density and temperature distributions and measurements of F region ion drifts that were made during a prenoon pass of the Defense Meteorological Satellite Program (DMSP)-F7 satellite through the radar field of view. The spacecraft traversed a region of intense electron precipitation with a characteristic energy below approximately 200 eV. Particles with such low characteristic energies are believed to be directly or indirectly of magnetosheath origin. The precipitation region had a width about 2 deg invariant latitude and covered the low-latitude boundary layer (LLBL), the cusp, and the equatorward section of the plasma mantle (PM). The corotating radar observed a patch of enhanced electron density and elevated electron temperature in the F2 region between about 10.5 and 12 magnetic local time in the same invariant latitude range where DMSP-F7 detected the soft-electron flux. The ion drift pattern, also obtained by radar, shows that it is unlikely that the plasma patch was produced by solar radiation and advected into the radar field of view. We suggest that the radar observed modifications of the ionospheric plasma distribution, which resulted from direct entry of magnetosheath electrons into the magnetosphere and down to ionospheric altitudes. Model calculations of the ionospheric response to the observed electron precipitation support our interpretation. The spectral characteristics of the electron flux in the LLBL, cusp, and equatorward section of the PM were in this case too similar to allow to distinguish between them by using incoherent scatter radar measurements only.

Watermann, Jurgen↗

DOE OSTI2021

Non-neutral plasma manipulation techniques in development of a high-capacity positron trap

Preliminary experiments have been performed toward the development of a multi-cell Penning–Malmberg trap for the storage of large numbers of positrons (≥10 10 e + ). We introduce the master-cell test trap and the diagnostic tools for first experiments with electrons. The usage of a phosphor screen to measure the z-integrated plasma distribution and the number of confined particles is demonstrated, as well as the trap alignment to the magnetic field ( B = 3.1 T) using the m = 1 diocotron mode. The plasma parameters and expansion are described along with the autoresonant excitation of the diocotron mode using rotating dipole fields and frequency chirped sinusoidal drive signals. We analyze the reproducibility of the excitation and use these findings to settle on the path for the next generation multi-cell test device.

Singer, M.↗

DOE OSTI2026

Understanding cold electron impact on parallel-propagating whistler chorus waves via moment-based quasilinear theory

Earth's magnetosphere hosts a wide range of collisionless particle populations that interact through various wave-particle processes. Among these, cold electrons, with energies below 100 eV, often dominate the plasma density but remain poorly characterized due to measurement challenges such as spacecraft charging and photoelectron contamination. Understanding the contribution of these cold populations to wave–particle interaction is of significant interest. Recent kinetic simulations identified a secondary drift-driven instability, in which parallel-propagating whistler-mode chorus waves excite oblique electrostatic whistler waves near the resonance cone and Bernstein-mode turbulence. These secondary modes enable a new channel of energy transfer from the parallel-propagating whistler wave to the cold electrons. In this work, we develop a moment-based quasilinear theory of the secondary instabilities to quantify such energy exchange. Our results show that these secondary instabilities persist for a wide range of parameters and, in many cases, lead to nearly complete damping of the primary wave. Such secondary instability might limit the amplitude of parallel-propagating whistler waves in Earth's magnetosphere and might explain why high-amplitude oblique whistler or electron Bernstein waves are rarely observed simultaneously with high-amplitude field-aligned whistler waves in the inner magnetosphere.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2025

Assessment of errors in analytic modeling of permanent magnet electron spectrometers for laser-plasma accelerators

Here, we assess the error in three treatments of a critical electron beam diagnostic for laser-plasma acceleration (LPA) experiments: a permanent magnet electron spectrometer. Since LPA electron spectrometers are often difficult to calibrate due to the scarcity of well-characterized, tunable electron beam sources in the appropriate energy range and the mechanical complexity of electron spectrometers, the standard of calibration is Hall probe measurements. We first compare the electron spectrometer performance between SIMION calculations and the Hall probe measurements. We find up to a 60% (<8%) error in determining the absolute energy for electrons below (above) 80 MeV when using the SIMION-modeled magnetic field vs the measured magnetic field due to SIMION overpredicting fringe field strength. The difference in spectrometer energy resolution is within ∼10% between the modeled and measured fields. We then assess a simple block model, which is commonly used. We find that the simple block model presented here sufficiently captures the predicted as-built spectrometer performance for any application provided that the user can tolerate uncertainties on absolute energy determination up to 5% and errors on energy resolution up to 1%.

Electromagnetic optics↗

NASA NTRS1990

SPEAR-1: An experiment to measure current collection in the ionosphere by high voltage biased conductors

An experiment is described in which a high electrical potential difference, up to 45 kV, was applied between deployed conducting spheres and a sounding rocket in the ionosphere. Measurements were made of the applied voltage and the resulting currents for each of 24 applications of different high potentials. In addition, diagnostic measurements of optical emissions in the vicinity of the spheres, energetic particle flow to the sounding rocket, dc electric field and wave data were made. The ambient plasma and neutral environments were measured by a Langmuir probe and a cold cathode neutral ionization gauge, respectively. The payload is described and examples of the measured current and voltage characteristics are presented. The characteristics of the measured currents are discussed in terms of the diagnostic measurements and the in-situ measurements of the vehicle environment. In general, it was found that the currents observed were at a level typical of magnetically limited currents from the ionospheric plasma for potentials less than 12 kV, and slightly higher for larger potentials. However, due to the failure to expose the plasma contactor, the vehicle sheath modified the sphere sheaths and made comparisons with the analytic models of Langmuir-Blodgett and Parker-Murphy less meaningful. Examples of localized enhancements of ambient gas density resulting from the operation of the attitude control system thrusters (cold nitrogen) were obtained. Current measurements and optical data indicated localized discharges due to enhanced gas density that reduced the vehicle-ionosphere impedance.

Raitt, W. John↗

NASA NTRS1978

Quiet-time plasma irregularities at 1400 km in the cleft region

The quiet north polar cleft at 1400 km was studied by Isis-2 instruments, and data from the retarding potential analyzer and the cylindrical electrostatic probe show that thermal plasma density fluctuations are distributed in a region between 75 deg and 82 deg invariant latitude and approximately dawn to dusk. Cleft shape and shape variations are described. Thermal ions and thermal electrons usually fluctuated together, but suprathermal electrons fluctuated independently. Data on thermal plasma patterns correlates fairly well with observations of soft particles and auroral optical emissions and not as well with measurements of high-energy particles. The data suggest that the energy source for the thermal irregularities is associated with soft particles and that precipitating high-energy particles do not drive the thermal plasma at these altitudes.

Kayser, S. E.↗

DOE OSTI2022

Direct spectral measurements of midinfrared radiation from a laser wakefield accelerator

The formation of plasma waves during laser wakefield acceleration (LWFA) produces time-dependent frequency shifts in the driving laser pulse, extending its spectral content to the infrared. We present direct spectral measurements of multi-mJ infrared pulses from an LWFA. Experimental beam profile measurements and three-dimensional particle-in-cell simulations suggest high focusability of these pulses. Further, particle-in-cell simulations demonstrate that the measurement of side-scattered infrared radiation may serve as a diagnostic of plasma waves and the efficiency of spectral broadening during LWFA.

43 PARTICLE ACCELERATORS↗

NASA NTRS2004

Development of a Method for Local Electron Temperature and Density Measurements in the Divertor of the JET Tokamak

Plasma volume recombination in the divertor, a process in which charged particles recombine to neutral atoms, contributes to plasma detachment and hence cooling at the divertor target region. Detachment has been observed at JET and other tokamaks and is known to occur at low electron temperatures (T(sub e)<1 eV) and at high electron density (n(sub e)>10(exp 20)/m(exp 3)). The ability to measure such low temperatures is therefore of interest for modelling the divertor. In present work we report development of a new spectroscopic technique for investigation of local electron density (n(sub e)) and temperature (T,) in the outer divertor at JET.

Jupen, C.↗

NASA NTRSDate not supplied

Trace Element Abundances Measured in Concentric and Texturally Distinct Fine-Grained Rims Surrounding Allende Chondrules

Layered rims of dust-sized material surround some chondrules and other early formed nebular particles, such as calcium aluminum inclusions in chondritic meteorites. In the Allende meteorite most chondrules(~85%) are un-rimmed and in direct contact with the host matrix material [1]. When present, rim thickness appears correlated to underlying particle size in both the Allende and Murchison chondrites [1,2]. This diverse behavior strongly argues for pre-parent body formation of rimmed particles as they traversed distinct (cooler and/or dustier) nebular environments [1]. Nebular rim formation involves accretion of unequilibrated dust to chondrule surfaces, recording evidence for the formation of at least two separate particle populations (chondrules and dust) that interacted in the nebula, and therefore potentially record distinct nebular reservoirs (e.g. [3-5]). Additionally, some particles exhibit textural evidence for multiple rim layers, (e.g., [1], further investigated herein). Herein, we evaluate the chemistry of concentrically and texturally distinct chondrule rim layers to investigate the possibility of discrete rim formation events recorded by individual chondrules (Fig. 1A,B). Using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) we measure major, minor, and trace elements of the rims and particles in Allende. Samples were characterized in detail previously by electron microanalysis for their mineralogy, textures, particle size, and rim thickness(es) [1].

Chondrites↗

NASA NTRS2023

SelenITA: A Dual Point Lunar Mission to Characterize the Near Surface Dust and Electromagnetic Plasma Environment

SelenITA is a dual CubeSat mission that will provide the first multi-point dust, plasma, and magnetic field measurements in lunar orbit. This mission will advance the understanding of the electromagnetic space environment at the Moon in support of the Artemis program, exploration, and the geosciences. Here we present the science rationale motivating the mission. The candidate mission science objectives include: (1) constrain the origins of crustal magnetic fields; (2) determine the nature of plasma interactions with crustal magnetic fields; (3) characterize plasma waves and turbulence at the Moon; (4) characterize the lunar surface electric potential in varying plasma environments; (5) constrain the composition, thermal state, and structure of the lunar upper mantle and crust; (6) characterize the ionizing radiation in lunar orbit; and lastly, (7) determine the density of the dust exosphere as a function of latitude, longitude, and altitude, including the lunar polar space environment. The measurement requirements include simultaneous two-point observations of the 3-component vector magnetic field, plasma distribution (flux, energy, density, temperature), and single-point observations of energetic particles (protons, electrons, gamma rays), and dust. These measurements are important because it helps us understand how future astronauts, robots, and space hardware will live and work on the lunar surface.

space weather↗

NASA NTRS2023

SelenITA: A Dual Point Lunar Mission to Characterize the Near Surface Dust and Electromagnetic Plasma Environment

space weather↗

NASA NTRS2015

Techniques for Measuring Surface Potentials in Space

Materials exposed to the space plasma environment charge to a net potential relative to the ambient plasma. The charging process is due to differential currents to the material surface that results in a net surface charge density. While this process is termed "spacecraft surface charging" when applied to aerospace hardware, it also applies to the surfaces of astronomical objects in direct contact with the space plasma environment including a number of planetary bodies, asteroids, and dust particles. The ability to measure surface potentials is important to many techniques used in conducting fundamental heliospheric science, spacecraft engineering operations, and space technology development activities. This presentation provides a survey of current technologies used to measure surface potentials of spacecraft and planetary bodies with examples of their application to space science and technology programs.

Minow, Joseph I.↗

NASA NTRS2007

MESSENGER and Venus Express Observations of the Solar Wind Interaction with Venus: A Dual Spacecraft Study

At 23:08 UT on 5 June 2007 the MESSENGER spacecraft reached its closest approach altitude (338 krn) during its second flyby of Venus en route to its 201 1 orbit insertion at Mercury. Whereas no measurements were collected during MESSENGER'S first Venus flyby in October 2006, the Magnetometer (MAG) and the Energetic Particle and Plasma Spectrometer (EPPS) operated successfully throughout this second encounter. Venus provides the solar system's best example to date of a solar wind - ionosphere planetary interaction. Pioneer Venus Orbiter measurements have shown that this interaction affects the upper atmosphere and ionosphere down to altitudes of - 150 km. Here we present an initial overview of the MESSENGER observations during the - 4 hrs that the spacecraft spent within 10 planet radii of Venus and, together with Venus Express measurements, examine the influence of solar wind plasma and interplanetary magnetic field conditions on the solar wind interaction at solar minimum.

Slavin, James A.↗

DOE OSTI2024

Design of radial interferometer–polarimeter for internal magnetic and density fluctuation measurements at multiple space–time scales in the National Spherical Torus Experiment-Upgrade (NSTX-U)

A Faraday-effect radial interferometer–polarimeter is designed for the National Spherical Torus Experiment-Upgrade (NSTX-U) to measure multiscale magnetic and density fluctuations critical to understanding fusion plasma confinement and stability, including those originating from magnetohydrodynamic instabilities, energetic particle-driven modes, and turbulence. The diagnostic will utilize the three-wave technique with 5 MHz bandwidth to simultaneously measure line-integrated magnetic and density fluctuations up to the ion-cyclotron frequency. Probe beams will be launched radially from the low-field side at the NSTX-U midplane, where the measured Faraday fluctuations mainly correspond to radial magnetic fluctuations that directly link to magnetic transport. A correlation technique will be employed to reduce the measurement noise to below 0.01° enabling detection of small amplitude fluctuations. Two toroidally displaced chords with 7° separation will be installed to measure toroidal mode numbers up to n = 25 for mode identification. Finally, solid-state microwave sources operating at 321 μm (935 GHz) will be used to minimize the impact of the Cotton–Mouton effect.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗