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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

The Solar Wind in the Third Dimension

For many years, solar-wind physicists have been using plasma and field data acquired near the ecliptic plane together with data on the scintillation of radio sources and remote sensing of structures in the solar corona to estimate the properties of the high-latitude solar wind. Because of the highly successful Ulysses mission, the moment of truth is now here. This talk summarizes the principal differences between the Ulysses observations and expectations.

Solar↗
NASA NTRS2003

Wave and Particle Interactions in the High and Low-Altitude Auroral Region During Rising Solar Activity

The project has resulted in four separate investigations, which are each in various stages of publication in the refereed scientific journals. The first investigation was of the generation of electrostatic electron cyclotron waves observed by the Polar spacecraft throughout the auroral regions, dayside cusp, and polar magnetosphere. We have since discovered that these waves are also present within the magnetopause and magnetosheath, which is one of the topics of a second study, entitled: 'Polar observations of plasma waves in and near the dayside magnetopause/magnetosheath.' A third study of plasma waves focussed on kilometric continuum (KC) emission. This work is reported in a paper entitled 'Near-source and Remote Observations of Kilometric Continuum Radiation From Multi-spacecraft Observations'.The final investigation of this program concerns the possible transverse heating of auroral ions by impulsive wave structures. We summarize that substantial transverse ion heating has already occurred at lower altitudes. Abstracts of the above four studies are included in the Appendix to this final report.

Gurnett, Donald A.↗
NASA NTRS1994

Feedback Control of Plasma Instabilities with Charged Particle Beams and Study of Plasma Turbulence

A new non-perturbing technique for feedback control of plasma instabilities has been developed in the Columbia Linear Machine (CLM). The feedback control scheme involves the injection of a feedback modulated ion beam as a remote suppressor. The ion beam was obtained from a compact ion beam source which was developed for this purpose. A Langmuir probe was used as the feedback sensor. The feedback controller consisted of a phase-shifter and amplifiers. This technique was demonstrated by stabilizing various plasma instabilities to the background noise level, like the trapped particle instability, the ExB instability and the ion-temperature-gradient (ITG) driven instability. An important feature of this scheme is that the injected ion beam is non-perturbing to the plasma equilibrium parameters. The robustness of this feedback stabilization scheme was also investigated. The principal result is that the scheme is fairly robust, tolerating about 100% variation about the nominal parameter values. Next, this scheme is extended to the unsolved general problem of controlling multimode plasma instabilities simultaneously with a single sensor-suppressor pair. A single sensor-suppressor pair of feedback probes is desirable to reduce the perturbation caused by the probes. Two plasma instabilities the ExB and the ITG modes, were simultaneously stabilized. A simple 'state' feedback type method was used where more state information was generated from the single sensor Langmuir probe by appropriate signal processing, in this case, by differentiation. This proof-of-principle experiment demonstrated for the first time that by designing a more sophisticated electronic feedback controller, many plasma instabilities may be simultaneously controlled. Simple theoretical models showed generally good agreement with the feedback experimental results. On a parallel research front, a better understanding of the saturated state of a plasma instability was sought partly with the help of feedback. A plasma instability is usually observed in its saturated state and appears as a single feature in the frequency spectrum with a single azimuthal and parallel wavenumbers. The physics of the non-zero spectral width was investigated in detail because the finite spectral width can cause "turbulent" transport. One aspect of the "turbulence" was investigated by obtaining the scaling of the linear growth rate of the instabilities with the fluctuation levels. The linear growth rates were measured with the established gated feedback technique. The research showed that the ExB instability evolves into a quasi-coherent state when the fluctuation level is high. The coherent aspects were studied with a bispectral analysis. Moreover, the single spectral feature was discovered to be actually composed of a few radial harmonics. The radial harmonics play a role in the nonlinear saturation of the instability via three-wave coupling.

Tham, Philip Kin-Wah↗
NASA NTRS1996

Remote Sensing Measurements of the Corona with the Solar Probe

Remote sensing measurements of the solar corona are indespensible for the exploration of the source and acceleration regions of the solar wind which are inaccessible to in situ plasma, paritcles and field experiments.Furthermore, imaging the solar disk and coronal from the unique vantage point of the trajectory and the proximity of the Solar Probe spacecraft, will provide the first ever opportunity to explore the small scale structures within coronal holes and streamers from viewing angles and with spatial resolutions never attained before.

remote sensing solar wind solar corona situ plasma↗
NASA NTRS2004

A Detection of the Same Hot Plasma in the Corona: During a CME and Later at Ulysses

We show direct evidence for the same very hot plasma being detected remotely from SOHO in the corona and subsequently, at Ulysses in the solar wind. This is, to our knowledge, the first time that such an unambiguous identification has been made in the case of hot plasma. This detection complements studies correlating other plasma and field properties observed to the properties measured at the source in the corona. This observation takes advantage of a SOHO-Sun-Ulysses quadrature, during which the Sun-Ulysses included angle is $90^\circ$ and it is possible to observe with Ulysses instruments the same plasma that has previously been remotely observed with SOHO instruments in the corona on the limb of the Sun. The identification builds on an existing base of separate SOHO and interplanetary detections of hot plasma. SOHO/UVCS has found evidence for very hot coronal plasma in current sheets in the aftermath of CMEs in the [Fe XVIII] $\lambda$ \AA\ line, implying a temperature on the order of $6\times 10(exp 6)$ K. This temperature is unusually high even for active regions, but is compatible with the high temperature predicted in current sheets. In the solar wind, ACE data from early 1998 to middle 2000 revealed high frozen-in Fe charge state in many cases to be present in interplanetary plasma.

Suess, S. T.↗
NASA NTRS1988

Experiments on optical discharges in hydrogen

The rudiments of a rocket thruster that receives its enthalpy from a remote energy source, a laser, are described. An experimental study is discussed that provides details of the physics for assessing the feasibility of using hydrogen plasmas for accepting and converting this energy to enthalpy. A plasma ignition scheme that uses a pulsed CO2 laser has been developed and the properties of the ignition spark documented, including breakdown intensities in hydrogen. A complete diagnostic system, capable of determining plasma temperature and the plasma absorptivity for subsequent steady-state absorption of a high-power CO2 laser beam, is developed and demonstrative use is discussed for the preliminary case study, a 2 atm laser-supported argon plasma.

Mccay, T. D.↗
NASA NTRS1978

The diffuse component of the cosmic X-radiation

The A-2 experiment on HEAO-1 is specifically developed to study the diffuse radiation of the entire X-ray sky over a wide bandwidth, covering both the soft X-ray emission from nearby regions of the galaxy and the isotropic hard X-radiation indicative of remote extragalactic origins. A partial conclusion from the experiment is that a hot thermal plasma, on a scale comparable to that of the universe, may be the principal source of hard X-radiation characteristic of the extragalactic sky. Some key features of this background were defined.

Boldt, E. A.↗
NASA NTRS2000

Mapping the Solar Wind from its Source Region into the Outer Corona

The solar wind not only forms the space environment of Earth and other planets, but is also the cause of many phenomena observed in the Earth's atmosphere, such as aurorae. The expansion of the coronal plasma of the Sun is characteristic to many main sequence stars, and thus provides an example for understanding stellar winds as well. In spite of its importance for both space science and stellar physics, basic solar wind properties remain essentially unresolved. Since its discovery about 50 years ago, the complexity of the Sun corona - solar wind system has complicated the interpretation of observations. Recent progress in remote sensing observations as provided for example by YOHKOH, SOHO, SPARTAN and ULYSSES as well as some ground based techniques such as Interplanetary Scintillation observations, offer a compelling opportunity to unravel the 50 year old puzzle regarding the heat source or sources that cause the expansion of the solar corona. The new era of solar wind observations initiated by SOHO and ULYSSES, have also led to a wealth of new theoretical approaches. The goal of the proposed research was to carry out an integrated study of the coronal and solar wind plasma making use of the opportunities provided by the above spacecraft, as well as plasma emission calculations and new ideas on solar wind expansion theory.

Esser, Ruth↗
NASA NTRS1984

Detection of a radio emission at 3 kHz in the outer heliosphere

A radio source in the outer heliosphere has been detected by the plasma wave receivers on Voyagers 1 and 2. The radio emission is observed in the frequency range 2-3 kHz, and is above the local solar wind electron plasma frequency whenever supporting plasma density data are available. The maximum spectral density of the emission recorded is about 10 to the -14th V-squared/m-squared/Hz. The bandwidth of the radio noise is about 1 kHz. Possible sources include continuum radiation from Jupiter's distant magnetotail and radiation at the second harmonic of the plasma frequency at the heliopause. If the latter interpretation is correct, these data represent the first remote observations of the heliopause.

Kurth, W. S.↗
NASA NTRS1992

H Ly-alpha transmittance of thin foils of C, Si/C, and Al/C for keV particle detectors

A class of instruments designed for remote sensing of space plasmas by measuring energetic neutral atoms (ENA) uses a thin foil as both a signal generator and a light shield. An ENA imager must look directly at the ENA source region, which is also usually an intense source of H Ly-alpha (1216 A) photons. It is desirable to minimize the energy threshold for ENA detectors, at the same time maximizing the blocking of H Ly-alpha. Optimizing filter design to meet these two contrary requirements has led us to measure the transmittance of thin C, Si/C, and Al/C foils at H Ly-alpha. Our results indicate that (1) transmittance of less than 0.0007 can be achieved with 7 micro-g/sq cm Si on 1.7 micro-g/sq cm C; (2) an Si/C composite foil with a thin carbon layer is more effective in blocking UV radiation while having the lowest energy threshold of all the foils measured; and (3) transmittance of Si/C foils of known Si and C thicknesses cannot be accurately predicted, but must be measured.

Drake, V. A.↗
NASA NTRS2011

Compositional Impact of Io Volcanic Emissions on Jupiter's Magnetosphere and the Icy Galilean Moons

The magnetospheric ion population of Jupiter is dominated by the 1000 kg/s of iogenic material constantly ejected by IO volcanism as neutral gas (approx. 1 kg/s goes out as high speed dust grains), subsequent atmospheric losses to the IO torus, and radial transport of torus ions throughout the magnetosphere. As that magnetosphere is greatly distended in radial size by the iogenic plasma loading, so are surfaces of the other Galilean moons also significantly, and perhaps even dominantly, affected by iogenic plasma bombardment, e.g. at the level up to 0.2 kg/s heavy ions (mostly O and S) onto Europa as per local plasma ion measurements. In comparison, cometary impacts onto IO deliver about 0.02 kg/s of impact ejecta to Europa via ballistic transfer through the Jupiter system. The magnetosphere of this system operates as a powerful engine to produce and transport ions from the IO source to the surfaces of these other moons, and any future orbiter missions to these moons must account for surface distributions of the iogenic material and its chemical effects before real assessments can be made of sensible chemical materials otherwise arising from primordial formation and subsequent evolution of these moons. This is a fundamental problem of space weathering that must be addressed for all planetary bodies with thin atmospheres and direct surface exposure to their space plasma environments. Long-standing debates from Galileo Orbiter measurements about the origins of hydrate sulfates at Europa present examples of this problem, as to whether the sulfates arise from oceanic minerals or from iogenic sulfur chemistry. Any orbiter or landed mission to Europa for astrobiological investigations would further need to separate the potential chemical biosignatures of life or its precursors from the highly abundant background of iogenic material. Although no single ion carries a tag identifying it as of iogenic or other origin, the elemental abundance distributions of ions to be measured throughout the jovian magnetosphere and in the local moon environments can act as tracers if we know from direct measurements and models the distributions at the mostly likely sources, i.e. at IO. However, our knowledge of these abundances are very limited from earlier in-situ and remote measurements, mainly confined to major (S, O) and some minor (Na, K, Cl) species with abundances at or above a few percent relative to O. Future in-situ plasma measurements by the planned Jupiter Europa Orbiter and Jupiter Ganymede Orbiter missions should extend the abundance coverage to minor and even trace elemental species. For Europa astrobiological investigations it is also important to specify iogenic inputs and surface processing of isotopic species. We discuss the range of abundance distributions arising from models for IO hot volcanic emissions, and from the subsequent dynamics of ion injection, magnetospheric transport, and icy moon surface bombardment.

Cooper, John↗
NASA NTRS1986

Measurements of Siple transmitter signals on the DE 1 satellite - Wave normal direction and antenna effective length

A new experimental technique is developed to simultaneously measure the wave propagation direction and the effective length of a small (L value much smaller than wavelength) electric dipole antenna on a spin-stabilized satellite in the magnetosphere. The technique relies on the near simultaneous measurement of single components of the electric and magnetic fields of a coherent VLF signal injected into the medium from a ground-based source. The spin fading characteristics of the signal received by the electric dipole and the magnetic loop antenna permit the measurement of the wave normal direction assuming whistler-mode propagation. In-situ and remote measurements of the local cold plasma density are used to determine the refractive index. The wave electric field is then inferred from the wave magnetic field as measured on the loop antenna, the refractive index and the direction of propagation. Comparing this electric field with the measured voltage across the dipole antenna leads to the determination of the effective length of the receiving electric dipole. The technique is applied to data from the Dynamics Explorer 1 satellite observations of whistler mode signals injected into the magnetosphere from the Siple, Antarctica, VLF transmitter. In one case, with the measured background cold plasma density being 15 el/cu cm, the effective length of the 200 m-long electric dipole antenna is found to be 222 + or - 56 m, i.e., about twice the conventional value.

Sonwalker, V. S.↗
NASA NTRS1992

Observation of local radio emission associated with type III radio bursts and Langmuir waves

The first clear detection of fundamental and harmonic radiation from the type III radio source region is presented. This radiation is characterized by its lack of frequency drift, its short rise and decay times, its relative weakness compared to the remotely observed radiation and its temporal coincidence with observed Langmuir waves. The observations were made with the radio and plasma frequency (URAP) receivers on the Ulysses spacecraft between about 1 and 2 AU from the Sun.

Reiner, M. J.↗
NASA NTRS1983

Longitudinal asymmetry of the Io plasma torus

Remote observations of the Io plasma torus have revealed a persistent longitudinal asymmetry in the brightness of optical S(+) emission lines but not of ultraviolet S(2+) emission lines. The S(+) asymmetry (with respect to the corotating System III coordinates) has been attributed to an asymmetric plasma source; the question then arises, why do the higher ionization states of sulfur not reflect a similar asymmetry? The explanation proposed here is based on the fact that torus ions do not quite corotate at the System III rate because of mass loading. If the resulting System III drift period of the ions is intermediate between the ionization lifetimes of S(+) and S(2+), then the asymmetry of the source will be obscured by longitudinal drift for the relatively long-lived multiply-ionized sulfur ions, but not for short-lived S(+).

Hill, T. W.↗
NASA NTRS2021

The First Widespread Solar Energetic Particle Event Observed By Solar Orbiter on 2020 November 29

Context. On 2020 November 29, the first widespread solar energetic particle (SEP) event of solar cycle 25 was observed at four widely separated locations in the inner (. 1AU) heliosphere. Relativistic electrons as well as protons with energies > 50MeV were observed by Solar Orbiter (SolO), Parker Solar Probe (PSP), the Solar Terrestrial Relations Observatory (STEREO)-A and multiple near-Earth spacecraft. The SEP event was associated with an M4.4 class X-ray flare and accompanied by a coronal mass ejection (CME) and an extreme ultraviolet (EUV) wave as well as a type II radio burst and multiple type III radio bursts. Aims. We present multi-spacecraft particle observations and place them in context with source observations from remote sensing instruments and discuss how such observations may further our understanding of particle acceleration and transport in this widespread event. Methods. Velocity dispersion analysis (VDA) and time shift analysis (TSA) were used to infer the particle release times at the Sun. Solar wind plasma and magnetic field measurements were examined to identify structures that influence the properties of the energetic particles such as their intensity. Pitch angle distributions and first-order anisotropies were analyzed in order to characterize the particle propagation in the interplanetary medium. Results. We find that during the 2020 November 29 SEP event, particles spread over more than 230° in longitude close to 1AU. The particle onset delays observed at the different spacecraft are larger as the flare–footpoint angle increases and are consistent with those from previous STEREO observations. Comparing the timing when the EUV wave intersects the estimated magnetic footpoints of each spacecraft with particle release times from TSA and VDA, we conclude that a simple scenario where the particle release is only determined by the EUV wave propagation is unlikely for this event. Observations of anisotropic particle distributions at SolO, Wind, and STEREO-A do not rule out that particles are injected over a wide longitudinal range close to the Sun. However, the low values of the first-order anisotropy observed by near-Earth spacecraft suggest that diffusive propagation processes are likely involved.

A Kollhoff↗
NASA NTRS2007

SOHO-Ulysses Coordinated Studies During the Two Extended Quadratures and the Alignment of 2007-2008

During SOHO-Sun-Ulysses quadratures the geometry of the configuration makes it possible to sample "in situ" the plasma parcels that are remotely observed in the corona. Although the quadrature position occurs at a well defined instant in time, we typically take data while Ulysses is within +/- 5 degrees of the limb, with the understanding that plasma sampled by Ulysses over this time interval can all be traced to its source in the corona. The relative positions of SOHO and Ulysses in winter 2007 (19 Dec 2006-28 May 2007) are unusual: the SOHO-Sun-Ulysses included angle is always between 85 and 95 degrees - the quadrature lasts for 5 months! This provides an opportunity for extended observations of specific observing objectives. In addition, in summer 2007, Ulysses (at 1.34 AU) is in near-radial alignment with Earth/ACE/Wind and SOHO, allowing us to analyze radial gradients and propagation in the solar wind and inner heliosphere. Our own quadrature campaigns rely heavily on LASCO and UVCS coronal observations: LASCO giving the overall context above 2 solar radii while the UVCS spectrograph acquired data from - 1.5 to, typically, 4-5 solar radii. In the past, coronal parameters have been derived from data acquired by these two experiments and compared with "in situ" data of Ulysses' SWOOPS and SWICS. Data from other experiments like EIT, CDS, SUMER, Sac Peak Fe XIV maps, magnetic field maps from the Wilcox solar magnetograph, MLSO, from MDI, and from the Ulysses magnetograph experiment have been, and will be, used to complement LASCO/UVCS/SWOOPS and SWICS data. We anticipate that observations by ACE/WIND/STEREO/Hinode and other missions will be relevant as well. During the IHY campaigns, Ulysses will be 52-80 degrees south in winter 2007, near sunspot minimum. Hence, our own scientific objective will be to sample high speed wind or regions of transition between slow and fast wind. This might be a very interesting situation - not met in previous quadratures - allowing us to study the variation of element abundances across streamer borders in the corona and,correspondingly, "in situ". Also, observing plasma over prolonged time intervals and at different latitudes, we may examine the latitude variation of the fractionation effect (e.g. Yon Steiger, 2002) and its dependence on time (e.g. Woo, 2004). For instance, if the FIP bias is dictated by the duration of plasma confinement in solar loops, its value in streamers should depend on the streamer age. Analogous variations should be found in the abundances of "in situ" plasma released by the streamer. All Ulysses and SOHO data is in the public domain and accessible so different objectives could be addressed by others. The winter 2008 quadrature will be well into the next sunspot cycle and there might be significant high mid-latitude activity. Ulysses will be up to 80 degrees in the northern hemisphere at this time and able to detect the resulting ICMEs and ejecta, allowing us to study the physical parameters of the propagating CME bubble/core/front, and/or to study the coronal and "in situ" characteristics of the current sheet associated with the event (e.g. Bemporad et al. 2005), so far still vaguely defined.

Suess, S. T.↗
NASA NTRS1992

Detection of fundamental and harmonic type III radio emission and the associated Langmuir waves at the source region

Type III radio emission generated in the vicinity of the Ulysses spacecraft has been detected at both the fundamental and harmonic of the local plasma frequency. The observations represent the first clear evidence of locally generated type III radio emission. This local emission shows no evidence of frequency drift, exhibits a relatively short rise time, is less intense than the observed remotely generated radio emission, and is temporally correlated with observed in situ Langmuir waves. The observations were made with the unified radio astronomy and wave (URAP) experiment on the Ulysses spacecraft between 1990 November 4 and 1991 April 30, as it traveled from 1 to 3 AU from the sun. During this time period many thousands of bursts were observed. However, only three examples of local emission and associated Langmuir waves were identified. This supports previous suggestions that type III radio emission is generated in localized regions of the interplanetary medium, rather than uniformly along the extent of the electron exciter beam.

Reiner, M. J.↗
NASA NTRS1994

(abstract) Tropospheric Calibration for the Mars Observer Gravity Wave Experiment

In spring 1993, microwave radiometer-based tropospheric calibration was provided for the Mars Observer gravitational wave search. The Doppler shifted X-band radio signals propagating between Earth and the Mars Observer satellite were precisely measured to determine path length variations that might signal passage of gravitational waves. Experimental sensitivity was restricted by competing sources of variability in signal transit time. Principally, fluctuations in the solar wind and ionospheric plasma density combined with fluctions in tropospheric refractivity determined the detection limit. Troposphere-induced path delay fluctions are dominated by refractive changes caused by water vapor inhomogeneities blowing through the signal path. Since passive microwave remote sensing techniques are able to determine atmospheric propagation delays, radiometer-based tropospheric calibration was provided at the Deep Space Network Uranus tracking site (DSS-15). Two microwave water vapor radiometers (WVRs), a microwave temperature profiler (MTP), and a ground based meterological station were deployed to determine line-of-sight vapor content and vertical temperature profile concurrently with Mars Observer tracking measurements. This calibration system provided the capability to correct Mars Observer Doppler data for troposphere-induced path variations. We present preliminary analysis of the Doppler and WVR data sets illustrating the utility of WVRs to calibrate Doppler data. This takes an important step toward realizing the ambitious system required to support future Ka-band Cassini satellite gravity wave tropospheric calibration system.

atmospheric water vapor microwave remote sensing↗