Search NASA⌕ Search

SEARCH · Search NASA

Results for “PLASMA FLUX MEASUREMENT”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
NASA NTRS2014

International Space Station Columbus Payload SoLACES Degradation Assessment

SOLAR is a European Space Agency (ESA) payload deployed on the International Space Station (ISS) and located on the Columbus Laboratory. It is located on the Columbus External Payload Facility in a zenith location. The objective of the SOLAR payload is to study the Sun. The SOLAR payload consists of three instruments that allow for measurement of virtually the entire electromagnetic spectrum (17 nm to 100 um). The three payload instruments are SOVIM (SOlar Variable and Irradiance Monitor), SOLSPEC (SOLar SPECctral Irradiance measurements), and SolACES (SOLar Auto‐Calibrating Extreme UV/UV Spectrophotometers). The SolACES payload includes a set of 4 spectrometers that measure the solar EUV flux from 17 nm to 220 nm. One of these 4 spectrometers failed early on (before deployment). EUV data is important in understanding the solar dynamo. Also, EUV flux is the source of most of the ionization that produces the ionosphere plasma. Plasma production is important in understanding the ionosphere environment. The ionosphere conditions affect many subjects including spacecraft charging, dynamo processes, instabilities, and communications. The 3 remaining spectrometers have collected valuable data during the historically low solar cycle 24. Some of this data will be presented. A significant trend in degradation of the remaining SolACES spectrometers was observed towards the end of CY2010 (GMT 310) through mid CY 2011 (GMT 132). The Principle Investigators of SolACES initiated a Mission Evaluation Room (MER) Chit to request an investigation of the degradation in CY 2011 (GMT 230). The Boeing Space Environments team was asked to respond to the ESA initiated MER Chit request to investigate the cause of the degradation. This paper will discuss the findings of that investigation.

Harman, William↗
NASA NTRS2023

The Eruption of a Magnetic Flux Rope Observed By Solar Orbiter and Parker Solar Probe

Magnetic flux ropes are a key component of coronal mass ejections, forming the core of these eruptive phenomena. However, determining whether a flux rope is present prior to eruption onset and, if so, the rope’s handedness and the number of turns that any helical field lines make is difficult without magnetic field modelling or in-situ detection of the flux rope. We present two distinct observations of plasma flows along a filament channel on 4 and 5 September 2022 made using the Solar Orbiter spacecraft. Each plasma flow exhibited helical motions in a right-handed sense as the plasma moved from the source active region across the solar disk to the quiet Sun, suggesting that the magnetic configuration of the filament channel contains a flux rope with positive chirality and at least one turn. The length and velocity of the plasma flow increased from the first to the second observation, suggesting evolution of the flux rope, with the flux rope subsequently erupting within ∼5 hours of the second plasma flow. The erupting flux rope then passed over the Parker Solar Probe spacecraft during its Encounter 13, enabling in-situ diagnostics of the structure. Although complex and consistent with the flux rope erupting from underneath the heliospheric current sheet, the in-situ measurements support the inference of a right-handed flux rope from remote-sensing observations. These observations provide a unique insight into the eruption and evolution of a magnetic flux rope near the Sun.

Dynamics↗
DOE OSTI2021

Pellet triggering of edge localized modes in low collisionality pedestals at DIII-D

Edge localized modes (ELMs) are triggered using deuterium pellets injected into plasmas with ITER-relevant low collisionality pedestals, and the resulting peak ELM energy fluence is reduced by approximately 25%–50% relative to natural ELMs destabilized at similar pedestal pressures. Cryogenically frozen deuterium pellets are injected from the low-field side of the DIII-D tokamak at frequencies lower than the natural ELM frequency, and heat flux is measured by infrared cameras. Ideal MHD pedestal stability calculations show that without pellet injection, these low collisionality pedestals were limited by their current density (peeling-limited) rather than their pressure gradient (ballooning-limited). ELM triggering success correlates strongly with pellet mass, consistent with the theory that a large pressure perturbation is required to trigger an ELM in low collisionality discharges that are far from the ballooning stability boundary. For sufficiently large pellets, both instantaneous and time-integrated ELM energy deposition measured by infrared cameras is reduced with respect to naturally occurring ELMs at the inner strike point, which is the position where it is largest for natural ELMs. Energy fluence at the outer strike point is less effected. Cameras observing both heat flux and D-alpha emission often find significant toroidally asymmetric striations in the outboard far scrape-off layer resulting from ELMs that are triggered by pellets. Toroidal asymmetries at the inner strike point are similar between natural and pellet-triggered ELMs, indicating that the reduction in peak heat flux and total fluence at that location is robust for the conditions reported here.

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↗
NASA NTRS2001

Constraints on Solar Wind Plasma Properties Derived from Coordinated Coronal Observations

The goal of the proposed research is to increase the understanding of coronal plasma phenomena by making use of different observational approaches and combine the observations with the necessary theoretical considerations. We continued to study the formation of spectral lines in the corona/transition region under different non-equilibrium conditions. In addition to Mg and Ne we have also studied some cases involving Si ions and spectral lines. Due to the fact that the sun was at the maximum phase of the solar cycle, we spent some time on observing coronal mass ejections. Observations of the H I Lyman-alpha spectral line and the line pair 0 VI 1031.91 AA and 1037.61 AA were carried out with the UVCS instrument in the northern polar region of the sun at position angle 270 deg. The region was monitored at about 2 RS for about 5 hours on March 04, and for about 8 hours on March 05. During that time interval a major Coronal Mass Ejection developed in the northern hemisphere. Density, velocity and temperature maps of the ejected plasma have been obtained from the UVCS data. This event was also seen in the white light Large Angle and Spectrometric Coronagraph Experiment (LASCO) images, and its evolution at lower heights can be followed in Extreme Ultraviolet Imaging Telescope (EIT). The LASCO images are essential in providing the larger scale context for this event which is unique in the sense that it developed almost due North and had very little interactions with adjacent regions. The combination of UVCS velocity maps and LASCO images which were reduced using advanced image processing techniques, show very clearly how the mass ejection evolved from the solar surface to several solar radii, the twisting of the flux ropes, which are seen in UVCS as blue and red shifted velocities. First results were presented at the AGU Meeting in Boston. To study the quieter side of the coronal plasma, we carried out an experiment during the past eclipse, in June 01. We measured the corona in several iron spectral lines, and polarized white light. The results from that experiment look promising so far.

Esser, Ruth↗
NASA NTRS2015

The Transition Region Response to a Coronal Nanoflare: Forward Modeling and Observations in SDO/AIA

The corona and transition region (TR) are fundamentally coupled through the processes of thermal conduction and mass exchange. It is not possible to understand one without the other. Yet the temperature-dependent emissions from the two locations behave quite differently in the aftermath of an impulsive heating event such as a coronal nanoflare. Whereas the corona cools sequentially, emitting first at higher temperatures and then at lower temperatures, the TR is multithermal and the emission at all temperatures responds in unison. We have previously applied the automated time lag technique of Viall & Klimchuk to disk observations of an active region (AR) made by the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory. Lines of sight passing through coronal plasma show clear evidence for post-nanoflare cooling, while lines of sight intersecting the TR footpoints of coronal strands show zero time lag. In this paper, we use the EBTEL hydrodynamics code to demonstrate that this is precisely the expected behavior when the corona is heated by nanoflares. We also apply the time lag technique for the first time to off-limb observations of an AR. Since TR emission is not present above the limb, the occurrence of zero time lags is greatly diminished, supporting the conclusion that zero time lags measured on the disk are due to TR plasma. Lastly, we show that the "coronal" channels in AIA can be dominated by bright TR emission. When defined in a physically meaningful way, the TR reaches a temperature of roughly 60% the peak temperature in a flux tube. The TR resulting from impulsive heating can extend to 3 MK and higher, well within the range of the "coronal" AIA channels.

Sun: corona↗
NASA NTRS2016

Review of the Theoretical and Experimental Status of Dark Matter Identification with Cosmic-Ray Antideuterons

Recent years have seen increased theoretical and experimental effort towards the first-ever detection of cosmic-ray antideuterons, in particular as an indirect signature of dark matter annihilation or decay. In contrast to indirect dark matter searches using positrons, antiprotons, or gamma-rays, which suffer from relatively high and uncertain astrophysical backgrounds, searches with antideuterons benefit from very suppressed conventional backgrounds, offering a potential breakthrough in unexplored phase space for dark matter. This article is based on the first dedicated cosmic-ray antideuteron workshop, which was held at UCLA in June 2014. It reviews broad classes of dark matter candidates that result in detectable cosmic-ray antideuteron fluxes, as well as the status and prospects of current experimental searches. The coalescence model of antideuteron production and the influence of antideuteron measurements at particle colliders are discussed. This is followed by a review of the modeling of antideuteron propagation through the magnetic fields, plasma currents, and molecular material of our Galaxy, the solar system, the Earth's geomagnetic field, and the atmosphere. Finally, the three ongoing or planned experiments that are sensitive to cosmic-ray antideuterons, BESS, AMS-02, and GAPS, are detailed. As cosmic-ray antideuteron detection is a rare event search, multiple experiments with orthogonal techniques and backgrounds are essential. Therefore, the combination of AMS-02 and GAPS antideuteron searches is highly desirable. Many theoretical and experimental groups have contributed to these studies over the last decade, this review aims to provide the first coherent discussion of the relevant dark matter theories that antideuterons probe, the challenges to predictions and interpretations of antideuteron signals, and the experimental efforts toward cosmic antideuteron detection.

Antideuteron Cosmic ray Dark matter↗
NASA NTRSDate not supplied

Science Conops for Application of Sport Mission Data to Study Large (~1000KN) Ionospheric Plasma Depletions

The Scintillation Prediction Observations Research Task (SPORT) mission is a single 6U CubeSat space weather satellite planned for an October 2022 launch into an ISS-like orbit. The primary purpose of the SPORT mission is to determine the longitudinal effects on equatorial plasma bubble (EPB) growth resulting from the offset dipole magnetic field of the Earth. By combining field and plasma measurements from SPORT with other low-altitude (i.e., alt < 1000 km) spacecraft, it is possible to investigate large-scale (> 1000 km) EPB structures. The types of investigation made possible by measurements from SPORT and other contemporaneous missions include 1) dynamics of depleted magnetic flux tubes; 2) dynamics of field-aligned EPB expansion versus propagation speed; 3) EPB vertical extent; and 4) EPB temporal evolution. To support these investigation types, the respective modes of conjunctions are: 1) simultaneous intersection of a magnetic flux tube; 2) intersection of magnetic flux tube separated in time; 3) Simultaneous Latitude/Longitude position conjunction; and 4) Non-simultaneous latitude/longitude position conjunction. This paper will summarize the SPORT satellite and data used for Science CONOPS to accomplish these objectives.

Scintillation↗
DOE OSTI2021

Modeling of ExB effects on tungsten re-deposition and transport in the DIII-D divertor

Mixed-material DIVIMP-WallDYN modelling, now incorporating ExB drifts, is presented that simultaneously reproduces tungsten (W) erosion and deposition patterns observed during the DIII-D Metal Rings Campaign, in which a toroidally symmetric set of W-coated tiles were installed in the carbon (C) DIII-D divertor. Since most reactor plasma facing component (PFC) designs call for mixed-material environments, including ITER’s W/Be enviroment, the divertor targets will quickly evolve into reconstitued surfaces of multiple elements. This work identifies controlling physics that affects material migration patterns in the divertor, which impact PFC lifetimes and impurity leakage from the divertor to the core. These simulations indicate that radial and poloidal ExB transport dominates over parallel force balance for high-Z impurities such as W in the divertor region of DIII-D. It is demonstrated that ExB drifts are required to reproduce the experimental observation of non-local W and C co-accumulation in a band ~7-9 cm outboard of the outer-strike-point (OSP) W source, for attached Lmode conditions in the unfavorable ion grad-B drift direction. In addition, W gross erosion is localized to the region outboard of the OSP, as the formation of C co-deposits suppresses W erosion at the strike point. Time-dependent simulations with scaled ExB impurity drifts (60% of the OEDGE-calculated drift velocity) and W re-erosion quantitatively reproduce these features, including depth-resolved W/C ratios, within a factor of 2 over ~115 seconds of accumulated plasma exposure. The location of co-deposition regions is shown to be well represented by an analytic leakage model, driven largely by poloidal ExB drifts. Qualitative agreement is also found between campaign-integrated W deposition measurements and simulations for the favorable ion grad-B drift direction, the standard mode of operation for most tokamaks. Furthermore, these results imply that a longterm inward radial migration of material from the outer divertor through the private flux region may occur in future devices.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Characterisation of a laser plasma betatron source for high resolution x-ray imaging

Abstract We report on the characterisation of an x-ray source, generated by a laser-driven plasma wakefield accelerator. The spectrum of the optimised source was consistent with an on-axis synchrotron spectrum with a critical energy of 13.8 − 1.9 + 2.2 keV and the number of photons per pulse generated above 1 keV was calculated to be 6 − 0.9 + 1.2 × 10 9 . The x-ray beam was used to image a resolution grid placed 37 cm from the source, which gave a measured spatial resolution of 4 µ m × 5 µ m. The inferred emission region had a radius and length of 0.5 ± 0.2 µ m and 3.2 ± 0.9 mm respectively. It was also observed that laser damage to the exit aperture of the gas cell led to a reduction in the accelerated electron beam charge and a corresponding reduction in x-ray flux due to the change in the plasma density profile.

plasma acceleration↗
NASA NTRS2022

Electron Heat Fluxes Generated by Intense Whistler Waves at the Upper Ionospheric Altitudes

Magnetospheric whistler waves, chorus and hiss, can't provide the resonance heating of the core electron plasma population. However, these whistler-mode branches, can implicitly participate in the heating processes of the core plasma thermal electron population by triggering the electron precipitation over a broad energy range from the magnetosphere and subsequent atmospheric ionization processes leading to the production of superthermal electron population. These superthermal electrons play a large role in the magnetosphere-ionosphere-atmosphere energy interplay with participation of both magnetically conjugate hemispheres, and their Coulomb interaction with background magnetospheric thermal electrons. Using strong hiss and chorus wave events measured by the Van Allen Probes and SuperThermal Electron Transport code, we evaluate the formation of electron heat fluxes at the upper ionospheric altitudes and discuss their consequences on the formation of electron temperature. It is found that chorus and hiss waves that initiate the precipitation of magnetospheric electrons with energies below 30 keV and the follow-up production of secondary electrons play an important role in the energy balance of ionosphere-magnetosphere system.

Magnetospheric whistler waves as an implicit sourc↗
NASA NTRS1984

The plasma wave environment of an auroral arc. II - ULF waves on an auroral arc boundary

On March 9, 1978, a sounding rocket launched from Poker Flat, Alaska, at 2200 LT, made a four-component measurement of a 0.5 Hz hydromagnetic wave as the payload crossed the poleward boundary of a quiet homogeneous auroral arc. An energy flux of about 10 to the -6th W/sq m was observed propagating upward with a left-handed polarization within the arc, and a flux 6 times greater was observed propagating downward with a right-handed polarization on the arc boundary. The waves were identified as shear mode Alfven waves. Various models for the source of the free energy are discussed with the conclusion that the most likely production mechanism was either the electromagnetic or electrostatic Kelvin-Helmholtz instability.

Gelpi, C. G.↗
NASA NTRS1989

Kilometric radiation power flux dependence on area of discrete aurora

Kilometer wavelength radiation, measured from distant positions over the North Pole and over the Earth's equator, was compared to the area of discrete aurora imaged by several low-altitude spacecraft. Through correlative studies of auroral kilometric radiation (AKR) with about two thousand auroral images, a stereoscopic view of the average auroral acceleration region was obtained. A major result is that the total AKR power increases as the area of the discrete auroral oval increases. The implications are that the regions of parallel potentials or the auroral plasma cavities, in which AKR is generated, must possess the following attributes: (1) they are shallow in altitude and their radial position depends on wavelength, (2) they thread flux tubes of small cross section, (3) the generation mechanism in them reaches a saturation limit rapidly, and (4) their distribution over the discrete auroral oval is nearly uniform. The above statistical results are true for large samples collected over a long period of time (about six months). In the short term, AKR frequently exhibits temporal variations with scales as short as three minutes (the resolution of the averaged data used). These fluctuations are explainable by rapid quenchings as well as fast starts of the electron cyclotron maser mechanism. There were times when AKR was present at substantial power levels while optical emissions were below instrument thresholds. A recent theoretical result may account for this set of observations by predicting that suprathermal electrons, of energies as low as several hundred eV, can generate second harmonic AKR. The indirect observations of second harmonic AKR require that these electrons have mirror points high above the atmosphere so as to minimize auroral light emissions. The results provide evidence supporting the electron cyclotron maser mechanism.

Saflekos, N. A.↗
DOE OSTI2025

Isotopic mass effects of tritium-fueled high-performance TFTR supershots

An increase in total stored energy correlated with the addition of tritium fuel was observed in supershots during the TFTR DT campaign. This supershot regime had strikingly high, centrally peaked ion and electron temperatures, and the largest neutron emission rates observed in TFTR. This paper presents a study of the causes of this increase in stored energy in supershots. Twenty-six supershots have been recently reanalyzed with the TRANSP plasma analysis code. Early TRANSP simulations did not accurately match the measured magnitude and time evolutions of the neutron emission rates. This mismatch is attributed to neglecting apparent increases of trace amounts of heavy impurities during neutral beam injection. The new TRANSP runs were tuned to accommodate this and match the measured global neutron emission rates. These new runs also had improved fidelity in predicting the time histories and radial dependencies of measured DT neutron emission rates. That in turn adds confidence in the simulated thermal deuterium and tritium density profiles that are needed for calculating the average hydrogenic atomic mass profiles. Six subsets of these supershots had well matched toroidal field B tor , plasma current I p , flux geometry, and total injected neutral beam power. The mix of D and T beam ions was varied for different discharges. The magnitude of the increase of the thermal ion energy W i with added tritium was relatively small, and the total W tot increase is dominated by the increase in fast beam ions with T. Analyses at times before the occurrences of deleterious MHD instabilities yielded scaling of W tot with the volume-average isotopic mass consistent with previous publications. The relative fraction of fast energy ions is expected to be small in practical tokamak reactors. Thus the increase in stored energy W tot observed in TFTR supershots does not appear likely to be significantly helpful for producing useful fusion energy.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1982

Physical processes in gamma-ray bursts

Physical processes occurring in gamma-ray bursts are discussed, with special attention to the event of March 5, 1979 in the Large Magellanic Cloud. The source of that event's extraordinary intense line and continuum radiation has been explained as a pair plasma confined in a strong magnetic field, as in a neutron star magnetosphere, and some consequences of that model are studied. The magnetic field (approximately 10 to the 13th gauss) affects both plasma physical processes and annihilation, so that accurate measurements of the annihilation line shape may lead to quantitative field determinations. A simple model for gamma-gamma pair production and annihilation is calculated, implying that this process will not prevent escape of intense gamma-ray fluxes. Finally, energetic considerations suggest that the magnetospheric energy may be regenerated from internal sources, either during or between bursts.

Katz, J. I.↗
NASA NTRS1978

ISEE-C solar wind plasma experiment

Two 135 deg spherical section electrostatic analyzers furnish electron and ion measurements of the solar wind on ISEE-C. Each of these instruments utilizes a divided secondary emitter system to intercept the analyzed particles. Secondary electrons selected from all of the emitters simultaneously provide fast two-dimensional measurements of the particle fluxes integrated over polar angle; at a slower rate secondary electrons are successively selected from individual emitters to provide three-dimensional measurements. Speed of the ion measurements is increased by a factor of two by using an active proton peak tracking system to reduce the total range of energy per charge which has to be covered.

Bame, S. J.↗
NASA NTRS2019

NuStar Hard X-Ray View of Low-Luminosity Active Galactic Nuclei: High-Energy Cutoff and Truncated Thin Disk

We report the analysis of simultaneous XMM-Newton+Nuclear Spectroscopic Telescope Array (NuSTAR) observations of two low-luminosity active galactic nuclei (LLAGNs), NGC3998 and NGC4579. We do not detect any significant variability in either source over the ∼3 day length of the NuSTAR observations. The broadband 0.5–60 keV spectrum of NGC3998 is best fit with a cutoff power law, while the one for NGC4579 is best fit with a combination of a hot thermal plasma model, a power law, and a blend of Gaussians to fit an Fe complex observed between 6 and 7 keV. Our main spectral results are the following: (1) neither source shows any reflection hump with 3σ reflection fraction upper limits of R < 0.3 and R < 0.18 for NGC3998 and NGC4579, respectively; (2) the 6–7 keV line complex in NGC4579 could be fit with either a narrow Fe K line at 6.4 keV and a moderately broad Fe XXV line or with three relatively narrow lines, which include contribution from Fe XXVI; (3) the NGC4579 flux is 60% brighter than previously detected with XMM-Newton, accompanied by a hardening in the spectrum; (4) we measure a cutoff energy = - E 107+ cut 18 27 keV in NGC3998, which represents the lowest and best constrained high-energy cutoff ever measured for an LLAGN; (5) the NGC3998 spectrum is consistent with a Comptonization model with either a sphere (τ ≈ 3 ± 1) or slab (τ ≈ 1.2 ± 0.6) geometry, corresponding to plasma temperatures between 20 and 150 keV. We discuss these results in the context of hard X-ray emission from bright AGNs, other LLAGNs, and hot accretion flow models.

Younes, George↗
DOE OSTI2020

Validation of neutron emission and neutron energy spectrum calculations on a Mega Ampere Spherical Tokamak with directional relativistic spectrum simulator

The recently developed directional relativistic spectrum simulator (DRESS) code has been validated for the first time against numerical calculations and experimental measurements performed on the Mega Ampere Spherical Tokamak . In this validation, the neutron emissivities and rates computed by DRESS are benchmarked against TRANSP/NUBEAM predictions while the neutron energy spectra provided by DRESS taking as input TRANSP/NUBEAM and ASCOT/BBNBI in Gyro-Orbit mode fast ion distributions are validated against proton pulse height spectra measured by the neutron flux monitor. Finally, excellent agreement was found between DRESS and TRANSP/NUBEAM predictions of local and total neutron emission.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗