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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Plasma and magnetospheric research

Methods employed in the analysis of plasmas and the magnetosphere are examined. Computer programs which generate distribution functions are used in the analysis of charging phenomena and non maxwell plasmas in terms of density and average energy. An analytical model for spin curve analysis is presented. A program for the analysis of the differential ion flux probe on the space shuttle mission is complete. Satellite data analysis for ion heating, plasma flows in the polar cap, polar wind flow, and density and temperature profiles for several plasmasphere transits are included.

Comfort, R. H.↗
NASA NTRS1998

Characterization of Plasma Discharges in a High-Field Magnetic Tandem Mirror

High density magnetized plasma discharges in open-ended geometries, like Tandem Mirrors, have a variety of space applications. Chief among them is the production of variable Specific Impulse (I(sub sp)) and variable thrust in a magnetic nozzle. Our research group is pursuing the experimental characterization of such discharges in our high-field facility located at the Advanced Space Propulsion Laboratory (ASPL). These studies focus on identifying plasma stability criteria as functions of density, temperature and magnetic field strength. Plasma heating is accomplished by both Electron and Ion Cyclotron Resonance (ECR and ICR) at frequencies of 2-3 Ghz and 1-30 Mhz respectively, for both Hydrogen and Helium. Electron density and temperature has measured by movable Langmuir probes. Macroscopic plasma stability is being investigated in ongoing research.

Chang-Diaz, Franklin R.↗
NASA NTRS1982

Dynamical features of moving double layers

Numerical simulations of the dynamics of double layers that form in response to an applied potential drop across a plasma are carried out for plasmas of lengths much greater than previously considered. The evolution of finite-size plasmas of lengths 100, 200 and 400 Debye lengths at the low-potential end of the simulation region was followed by the solution of the Vlasov and Poisson equations. Results show that the double layer moves towards the high-potential side of the layer, at a speed directly dependent on the length of the plasma. The moving double layer is accompanied by a moving density front which is similar to an ion acoustic shock created by the expansion of a high-density plasma into a low-density plasma, as well as plasma heating and evacuation, electron and ion current interruptions and recovery. Double layer formation, motion, and accompanying phenomena are found to repeat periodically. Results are in good agreement with laboratory experiments, and may be used to explain certain phenomena observed in auroral plasmas.

Singh, N.↗
NASA NTRS1991

Transverse conductivity of a relativistic plasma in oblique electric and magnetic fields

Resistive tearing in a primary candidate for flares occurring in stressed magnetic fields. Its possible application to the strongly magnetized environments (Hz about 10 to the 12th G) near the surface of neutron stars, particularly as a mechanism for generating the plasma heating and particle acceleration leading to gamma-ray bursts, has motivated a quantum treatment of this process, which requires knowledge of the electrical conductivity sigma of a relativistic gas in a new domain (i.e., that of a low-density n/e/) plasma in oblique electric and magnetic fields. This paper discusses the mathematical formalism for calculating sigma and present numerical results for a wide range of parameter values. The results indicate that sigma depends very strongly on both the applied electric and magnetic fields.

Melia, Fulvio↗
NASA NTRS1986

Acceleration of low-energy magnetospheric plasma

Low-energy plasma originates in the ionosphere and is accelerated and transported to the plasma sheet and ultimately to the ring current. Using observations and basic MHD concepts, it is argued that the acceleration results basically from entrainment in flows that are rapid compared with initial ion thermal speeds. Spatial or temporal variations of such flows launch impulsive waves of the appropriate variety (acoustic, shear Alfven, or magnetosonic) to effect readjustment to the imposed boundary conditions. The most violent transient events are the earthward inductive surges of plasma in the inner plasma sheet, which launch magnetosonic waves. A number of observations strongly suggest that the induction surge waves break as they reach the inner plasma sheet or outer plasmasphere, forming transient shock waves and dissipating their energy in turbulent flows, plasma heating, and acceleration of energetic particles, forming the substorm injection boundary. Preliminary work indicates that the magnetosphere is typically configured so as to produce wave breaking near synchronous orbit, and has other interesting optical properties for MHD wave propagation as well. Exploration of magnetospheric plasma wave optics will require a better empirical knowledge of the plasma distribution.

Moore, T. E.↗
NASA NTRS2003

Tether-Cutting Energetics of a Solar Quiet Region Prominence Eruption

We study the morphology and energetics of a slowly-evolving quiet region solar prominence eruption occurring on 1999 February 8-9 in the solar north polar crown region, using soft X-ray data from the soft X-ray telescope (SXT) on Yohkoh and Fe xv EUV 284 A data from the EUV Imaging Telescope (EIT) on SOHO. After rising at approx. 1 km/s for about six hours, the prominence accelerates to a velocity of approx. 10 km/s, leaving behind EUV and soft X-ray loop arcades of a weak flare in its source region. Intensity dimmings occur in the eruption region cospatially in EUV and soft X-rays, indicating that the dimmings result from a depletion of material. Over the first two hours of the prominence s rapid rise, flare-like brightenings occur beneath the rising prominence which may correspond to "tether cutting" magnetic reconnection. These brightenings have heating requirements of up to approx. 10(exp 28)-10(exp 29) ergs, and this is comparable to the mechanical energy required for the rising prominence over the same time period. If the ratio of mechanical energy to heating energy remains constant through the early phase of the eruption, then we infer that coronal signatures for the tether cutting may not be apparent at or shortly after the start of the fast phase in this or similar low-energy eruptions, since the plasma-heating energy levels would not exceed that of the background corona.

Sterling, Alphonse C.↗
NASA NTRS2003

Tether-Cutting Energetics of a Solar Quiet Region Prominence Eruption

We study the morphology and energetics of a slowly evolving quiet-region solar prominence eruption occurring on 1999 February 8-9 in the solar north polar crown region, using soft X-ray data from the soft X-ray telescope (SXT) on Yohkoh and Fexv EUV 284 Angstrom data from the EUV Imaging Telescope (EIT) on the Solar and Heliospheric Observatory (SOHO). After rising at approximately equal to l kilometer per second for about six hours, the prominence accelerates to a velocity of approximately equal to 10 kilometers per second, leaving behind EUV and soft X-ray loop arcades of a weak flare in its source region. Intensity dimmings occur in the eruption region cospatially in EUV and soft X-rays, indicating that the dimmings result from a depletion of material. Over the first two hours of the prominences rapid rise, flare-like brightenings occur beneath the rising prominence that might correspond to tether-cutting magnetic reconnection. These brightenings have heating requirements of up to approximately 10(exp 28)-10(exp 29) ergs, and this is comparable to the mechanical energy required for the rising prominence over the same time period. If the ratio of mechanical energy to heating energy remains constant through the early phase of the eruption, then we infer that coronal signatures for the tether cutting may not be apparent at or shortly after the start of the fast phase in this or similar low-energy eruptions, since the plasma-heating energy levels would not exceed that of the background corona.

Sterling, Alphonse C.↗
NASA NTRS1999

The Origin of the Near-Earth Plasma Population During a Substorm on November 24, 1996

We investigate the origins and the transport of ions observed in the near-Earth plasma sheet during the growth and expansion phases of a magnetospheric substorm that occurred on November 24, 1996. Ions observed at Geotail were traced backward in time in time-dependent magnetic and electric fields to determine their origins and the acceleration mechanisms responsible for their energization. Results from this investigation indicate that, during the growth phase of the substorm, most of the ions reaching Geotail had origins in the low latitude boundary layer (LLBL) and had already entered the magnetosphere when the growth phase began. Late in the growth phase and in the expansion phase a higher proportion of the ions reaching Geotail had their origin in the plasma mantle. Indeed, during the expansion phase more than 90% of the ions seen by Geotail were from the mantle. The ions were accelerated enroute to the spacecraft; however, most of the ions' energy gain was achieved by non-adiabatic acceleration while crossing the equatorial current sheet just prior to their detection by Geotail. In general, the plasma mantle from both southern and northern hemispheres supplied non-adiabatic ions to Geotail, whereas the LLBL supplied mostly adiabatic ions to the distributions measured by the spacecraft. Distribution functions computed at the ion sources indicate that ionospheric ions reaching Geotail during the expansion phase were significantly heated. Plasma mantle source distributions indicated the presence of a high-latitude reconnection region that allowed ion entry into the magnetosphere when the IMF was northward. These ions reached Geotail during the expansion phase. Ions from the traditional plasma mantle had access to the spacecraft throughout the substorm.

Ashour-Abdalla, M.↗
NASA NTRS1988

Explosive plasma flows in a solar flare

Solar Maximum Mission soft X-ray data and Sacramento Peak Observatory H-alpha observations are combined in a study of the impulsive phase of a solar flare. A blue asymmetry, indicative of upflows, was observed in the coronal Ca XIX line during the soft X-ray rise phase. A red asymmetry, indicative of downflows, was observed simultaneously in chromospheric H-alpha emitted from bright flare kernels during the period of hard X-ray emission. Combining the velocity data with a measurement of coronal electron density, it is shown that the impulsive phase momentum of upflowing soft X-ray-emitting plasma equalled that of the downflowing H-alpha-emitting plasma to within one order of magnitude. In particular, the momentum of the upflowing plasma was 2 x 10 to the 21st g cm/s while that of the downflowing plasma was 7 x 10 to the 21st g cm/s, with a factor of 2 uncertainty on each value. This equality supports the explosive chromospheric evaporation model of solar flares, in which a sudden pressure increase at the footprint of a coronal loop produces oppositely directed flows in the heated plasma.

Zarro, Dominic M.↗
NASA NTRS1989

Excitation of kinetic Alfven waves by resonant mode conversion and longitudinal heating of magnetized plasmas

The excitation of the kinetic Alfven wave by resonant mode conversion and longitudinal heating of the plasma by the kinetic Alfven wave were demonstrated on the basis of a macroscale particle simulation. The longitudinal electron current was shown to be cancelled by the ions. The kinetic Alfven wave produced an ordered motion of the plasma particles in the wave propagation direction. The electrons were pushed forward along the ambient magnetic field by absorbing the kinetic Alfven wave through the Landau resonance.

Tanaka, Motohiko↗
DOE OSTI2025

Thermal and kinematic properties of ejecta in SN1987A revealed by XRISM

We present an analysis of high-resolution spectra from the shock-heated plasmas in SN 1987A, based on an observation using the Resolve instrument onboard the X-Ray Imaging and Spectroscopy Mission (XRISM). The 1.7–10 keV Resolve spectra are accurately represented by a single-component, plane-parallel shock plasma model, with a temperature of $2.84_{-0.08}^{+0.09}$ keV and an ionization parameter of $2.64_{-0.45}^{+0.58}$ × $10^{11}\,\,{\rm s\,\, cm}^{-3}$. The Resolve spectra are also well reproduced by the 3D magneto-hydrodynamic simulation presented by Orlando et al. (2020, A&A, 636, A22) suggesting substantial contribution from the ejecta. The metal abundances obtained with Resolve align with the Large Magellanic Cloud value, indicating that the X-rays in 2024 originate from “non-metal-rich” shock-heated ejecta and the reverse shock has not reached the inner metal-rich region of ejecta. Doppler widths of the atomic lines from Si, S, and Fe correspond to velocities of 1500–1700 km s$^{-1}$, where the thermal broadening effects in this non-metal-rich plasma are negligible. Therefore, the line broadening seen in Resolve spectra is determined by the large bulk motion of ejecta. For reference, we determined a $90\%$ upper limit on non-thermal emission from a pulsar wind nebula at $4.3 \times 10^{-13}$ erg cm$^{-2}$ s$^{-1}$ in the 2–10 keV range, aligning with NuSTAR findings by Greco et al. (2022, ApJ, 931, 132). Additionally, we searched for the $^{44}$Sc K line feature and found a $1\sigma$ upper limit of $1.0 \times 10^{-6}$ photons cm$^{-2}$ s$^{-1}$, which translates to an initial $^{44}$Ti mass of approximately $2 \times 10^{-4}\, M_{\odot }$, consistent with previous X-ray to soft gamma-ray observations (Boggs et al. 2015, Science, 348, 670; Grebenev et al. 2012, Nature, 490, 373; Leising 2006, ApJ, 651, 1019).

ISM: supernova remnants↗
NASA NTRS2016

The Potential for Ambient Plasma Wave Propulsion

A truly robust space exploration program will need to make use of in-situ resources as much as possible to make the endeavor affordable. Most space propulsion concepts are saddled with one fundamental burden; the propellant needed to produce momentum. The most advanced propulsion systems currently in use utilize electric and/or magnetic fields to accelerate ionized propellant. However, significant planetary exploration missions in the coming decades, such as the now canceled Jupiter Icy Moons Orbiter, are restricted by propellant mass and propulsion system lifetimes, using even the most optimistic projections of performance. These electric propulsion vehicles are inherently limited in flexibility at their final destination, due to propulsion system wear, propellant requirements, and the relatively low acceleration of the vehicle. A few concepts are able to utilize the environment around them to produce thrust: Solar or magnetic sails and, with certain restrictions, electrodynamic tethers. These concepts focus primarily on using the solar wind or ambient magnetic fields to generate thrust. Technically immature, quasi-propellantless alternatives lack either the sensitivity or the power to provide significant maneuvering. An additional resource to be considered is the ambient plasma and magnetic fields in solar and planetary magnetospheres. These environments, such as those around the Sun or Jupiter, have been shown to host a variety of plasma waves. Plasma wave propulsion takes advantage of an observed astrophysical and terrestrial phenomenon: Alfven waves. These are waves that propagate in the plasma and magnetic fields around and between planets and stars. The generation of Alfven waves in ambient magnetic and plasma fields to generate thrust is proposed as a truly propellantless propulsion system which may enable an entirely new matrix of exploration missions. Alfven waves are well known, transverse electromagnetic waves that propagate in magnetized plasmas at frequencies below the ion cyclotron frequency. They have been observed in both laboratory and astrophysical settings. On Earth, they are being investigated as a possible means for plasma heating, current drive, and momentum addition in magnetic confinement fusion systems. In addition, Alfven waves have been proposed as a mechanism for acceleration of the solar wind away from the sun.

THE POTENTIAL FOR AMBIENT PLASMA WAVE PROPULSION↗
NASA NTRSDate not supplied

Nanoflare Heating Frequency of an X-ray Bright Point Observed by MaGIXS

Nanoflares have been considered to be one of the most likely candidates for heating the solar corona to multi-million kelvin temperatures. Individual nanoflares are difficult to detect with today's instruments, but their presence may be established by comparing simulated nanoflare-heated plasma emissions to observed emissions. We present a simulation of emission from an X-ray Bright Point (XBP) detected by the MaGIXS, as well as simultaneous observations from SDO/AIA and Hinode/XRT. To simulate the XBP loops, we utilize the HYDRAD code. The length and magnetic field strength of these loops are determined using potential field extrapolation of SDO/HMI's observed photospheric magnetogram. Each loop is considered to be heated by random nanoflares, the amplitude and frequency of which are governed by the length of the loop and the strength of the magnetic field. The simulated outputs are used to estimate the intensity of spectrally pure maps of Fe-18, Fe-17, Ne-9, O-8, O-9, Ne-9, and so on, which is then compared to the intensity determined from MaGIXS observations. In addition, we derived the intensity maps obtained by AIA and XRT and compared them to the observed data. The composite distribution of the delay time of the nanoflares for which the simulated loops morphology and intensities match with observation shows a peak at 200s-500s, indicating that most of the nanoflares have a high/intermediate frequency.

coronal heating↗
DOE OSTI2025

Saturation and decay of an induced scattering instability driven by static field asymmetries in a non-neutral plasma

Experimental data on the saturation and decay of a previously described induced scattering instability are presented. The instability is driven by static background field asymmetries and initially produces a single growing mode (ω 1 , k 1 ). As the instability develops, several harmonically related (ω n =nω 1 , k n =nk 1 ) eigenmodes of the plasma column grow up, resulting in a spatially localized moving potential perturbation with δϕ/T ≈ 20%. After a period of rapid growth, the mode amplitudes saturate and vary slowly for roughly 10 5 ω 1 −1 . This quasi-equilibrium ends with an unusual change in the eigenmode phases, wherein δϕ changes from positive to negative. Plasma heating during this period increases the damping of all modes and rapidly quenches the instability. This instability is of particular interest because the coupling with the field asymmetry produces an enhanced level of radial transport.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2001

Conceptual Design of an MTF Space Propulsion System

Most fusion propulsion concepts that have been investigated in the past employ some form of inertial or magnetic confinement separately, and are encumbered by the need for advanced drivers (e.g. laser) or steady-state magnetic confinement systems (e.g. superconductors) that have historically resulted in large, massive spacecraft designs. Here we present a comparatively new approach, Magnetized Target Fusion (MTF), which offers a nearer-term avenue for realizing the tremendous performance benefits of fusion propulsion. MTF attempts to combine the favorable attributes of both inertially and magnetically confined fusion to achieve both efficient and low-cost compressional plasma heating and energy confinement. The key advantage of MTF is its less demanding requirements for driver energy and power processing. Additional features include: 1) very low system masses and volumes, 2) high gain and relatively low waste heat, 3) substantial utilization of energy from product neutrons, 4) efficient, low peak-power drivers based on existing pulsed power technology, and 5) very high I(sub sp), specific power and thrust. MTF overcomes many of the problems associated with traditional fusion techniques, thus making it particularly attractive for space applications. I(sub sp) greater than 50,000 seconds and specific powers greater than 20 kilowatts/kilogram appear feasible using relatively near-term pulse power and plasma gun technology.

Thio, Y. C. Francis↗
NASA NTRS2002

Conceptual Design of an MTF Space Propulsion System

Most fusion propulsion concepts that have been investigated in the past employ some form of inertial or magnetic confinement separately, and are encumbered by the need for advanced drivers (e.g. laser) or steady-state magnetic confinement systems (e.g. superconductors) that have historically resulted in large, massive spacecraft designs. Here we present a comparatively new approach, Magnetized Target Fusion (MTF), which offers a nearer-term avenue for realizing the tremendous performance benefits of fusion propulsion. MTF attempts to combine the favorable attributes of both inertially and magnetically confined fusion to achieve both efficient and low-cost compressional plasma heating and energy confinement. The key advantage of MTF is its less demanding requirements for driver energy and power processing. Additional features include: 1) very low system masses and volumes, 2) relatively low waste heat, 3) substantial utilization of energy from product neutrons, 4) efficient, low peak-power drivers based on existing pulsed power technology, 5) very high Isp , specific power and thrust, and 6) relatively affordable R&D pathways. MTF overcomes many of the problems associated with traditional fusion techniques, thus making it particularly attractive for space applications. Isp greater than 50,000 seconds and specific powers greater than 20 kilowatts/kilogram appear feasible using relatively near-term pulse power and plasma gun technology.

Thio, Y. C. F.↗
NASA NTRSDate not supplied

Nanoflare Heating Frequency of an X-Ray Bright Point Observed By MaGIXS

Nanoflares are thought to be one of the prime candidates that can heat the solar corona to its multimillion kelvin temperature. Individual nanoflares are difficult to detect with the present generation instruments, however their presence can be inferred by comparing simulated nanoflare-heated plasma emissions with the observed emission. Using HYDRAD coronal loop simulations, we model the emission from an X-ray bright point observed by the Marshall Grazing Incidence X-ray Spectrometer (MaGIXS), along with concurrent observations from the Atmospheric Imaging Assembly (AIA) onboard Solar Dynamics Observatory (SDO) and X-Ray Telescope (XRT) onboard Hinode observatory. The length and magnetic field strength of the coronal loops are derived from the potential field extrapolation of the observed photospheric magnetogram by Helioseismic and Magnetic Imager (HMI) onboard SDO. Each loop is assumed to be heated by random nanoflares, whose magnitude and frequency are determined by the loop length and magnetic field strength. The simulation results are then compared and matched against the measured intensity from AIA, XRT, and MaGIXS. Our model results indicate the loop morphology and emissions from the XBP under study could be well matched by a distribution of nanoflares with average delay times 400 s to 800 s, which strongly suggest that the heating is dominated by high-frequency events. Further, we demonstrate the high sensitivity of MaGIXS and XRT to diagnose the heating frequency using this method, while AIA passbands are found to be the least sensitive.

coronal heating↗
DOE OSTI2025

Velocity-space signatures of shock-drift acceleration at quasi-perpendicular collisionless shocks

The shock-drift acceleration of ions at quasi-perpendicular shocks is a well-known kinetic mechanism for the acceleration of a small fraction of incoming ions to high energy. Here, we use a suite of sixteen hybrid simulations of quasi-perpendicular collisionless shocks over the range of Alfvén Mach number 4.3 ≤ M A ≤ 15.8 (corresponding to a range of fast magnetosonic Mach numbers 2.6 ≤ M f ≤ 9.4) and shock-normal angle 45°≤ θ Bn ≤ 90° to identify the velocity-space signature of shock-drift acceleration using the field-particle correlation technique. We show that the features of the ion velocity distribution in the shock foot and ramp regions can be clearly interpreted by analysis of the single-particle trajectory of a reflected ion through the full 3D-3V phase space. The characteristic features of the velocity-space signature of shock-drift acceleration remain qualitatively robust over the full parameter range of our simulations, providing a potential means for its identification using single-point spacecraft measurements. At higher Alfvén Mach numbers M A ≳8 (M f ≳5), kinetic instabilities generate fluctuations of the electromagnetic fields within the shock transition region, leading to fluctuations in and smearing out of the resulting velocity-space signatures, but the signature remains generally robust and identifiable. The results on the shock-drift acceleration of ions presented here represent a novel means to determine more completely the partitioning of upstream bulk flow kinetic energy into plasma heating, particle acceleration, and electromagnetic fields in collisionless shocks.

Howes, Gregory G. [Univ. of Iowa, Iowa City, IA (U↗