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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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NASA NTRS2009

Blowout Jets: Evidence from Hinode/XRT for X-Ray Jets Made by Blowout Eruption of the Emerging Bipole

Yamauchi et al (2004, ApJ, 605, 511) found that there are two structurally and dynamically distinct types of H macrospicules in polar coronal holes: single-column jet macrospicules and erupting-loop macrospicules. The structure and motion of the single-column jet macrospicules fit the standard Shibata reconnection picture for solar X-ray jets (Shibata et al 1992, PASJ, 44, L173). The form and motion of the erupting-loop macrospicules is reminiscent of the ejective eruption of the sheared-core-field flux rope in the filament-eruption birth of a bubble-type coronal mass ejection (CME). That roughly half of all polar H macrospicules were observed to be erupting-loop macrospicules suggests that there should be a corresponding large class of X-ray jets in which the emerging bipole at the base of the jet undergoes a blowout eruption as in a bubble-type CME, instead of staying closed as in the standard picture for X-ray jets. Along with a cartoon of the standard picture, we present a cartoon depicting the signatures to be expected of a blowout jet in high-resolution coronal X-ray movies such as from Hinode/XRT. From Hinode/XRT movies in polar coronal holes, we show: (1) examples of X-ray jets that fit the standard picture very well, and (2) other examples that do not fit the standard picture but do show signatures appropriate for blowout jets. These signatures are (1) a flare arcade inside the emerging bipole in addition to the flare arcade produced between the emerging bipole and the ambient high-reaching unipolar field by reconnection of these two fields as in the standard picture, and (2) in addition to the jet prong expected from the standard reconnection, a second jet prong or strand, one that could not be produced by the standard reconnection but could be produced by reconnection between the ambient unipolar field and one leg of an erupting core-field flux rope that has blown out the emerging bipole. We therefore infer that these "two pronged" jets are made by miniature versions of the sheared-core-bipole explosions that produce bubble-type CMEs. This work was funded by NASA s Science Mission Directorate through the Heliophysics Guest Investigators Program, the Hinode Project, and the Living With a Star Targeted Research and Technology Program.

Moore, Ronald L.↗
NASA NTRS2002

Synchrotron and Synchrotron Self-Compton Spectral Signatures and Blazar Emission Models

We find that energy losses due to synchrotron self-Compton (BBC) emission in Blazar jets can produce distinctive signatures in the time-averaged synchrotron and SSC spectra of these objects. For a fairly broad range of particle injection distributions, SSC-loss-dominated synchrotron emission exhibits a spectral dependence Fv approximately v (exp -3/2). The presence or absence of this dependence in the optical and ultraviolet spectra of flat-spectrum radio quasars such as PC 279 and in the soft X-ray spectra of high-frequency BL Lac objects such as Mark 501 gives a robust measure of the importance of SSC losses. Furthermore, for partially cooled particle distributions, spectral breaks of varying sizes can appear in the synchrotron and SSC spectra and will be related to the spectral indices of the emission below the break. These spectral signatures place constraints on the size scale and the nonthermal particle content of the emitting plasma, as well as the observer orientation relative to the jet axis.

Chiang, James↗
NASA NTRS2010

Blowout Jets: Hinode X-Ray Jets that Don't Fit the Standard Model

Nearly half of all H-alpha macrospicules in polar coronal holes appear to be miniature filament eruptions. This suggests that there is a large class of X-ray jets in which the jet-base magnetic arcade undergoes a blowout eruption as in a CME, instead of remaining static as in most solar X-ray jets, the standard jets that fit the model advocated by Shibata. Along with a cartoon depicting the standard model, we present a cartoon depicting the signatures expected of blowout jets in coronal X-ray images. From Hinode/XRT movies and STEREO/EUVI snapshots in polar coronal holes, we present examples of (1) X-ray jets that fit the standard model, and (2) X-ray jets that do not fit the standard model but do have features appropriate for blowout jets. These features are (1) a flare arcade inside the jet-base arcade in addition to the small flare arcade (bright point) outside that standard jets have, (2) a filament of cool (T is approximately 80,000K) plasma that erupts from the core of the jetbase arcade, and (3) an extra jet strand that should not be made by the reconnection for standard jets but could be made by reconnection between the ambient unipolar open field and the opposite-polarity leg of the filament-carrying flux-rope core field of the erupting jet-base arcade. We therefore infer that these non-standard jets are blowout jets, jets made by miniature versions of the sheared-core-arcade eruptions that make CMEs

Moore, Ronald L.↗
NASA NTRS2015

Numerical Experiments of Counterflowiing Jet Effects on Supersonic Slender-Body Configurations

Previous studies have demonstrated that the use of counterflowing jets can greatly reduce the drag and heat loads on blunt-body geometries, especially when the long penetration mode jet condition can be established. Previously, the authors had done some preliminary numerical studies to determine the ability to establish long penetration mode jets on a typical Mach 1.6 slender configuration, and study its impact on the boom signature. The results indicated that a jet with a longer penetration length was required to achieve any impact on the boom signature of a typical Mach 1.6 slender configuration. This paper focuses on an in-depth parametric study, done using the space-time conservation element solution element Navier-Stokes flow solver, for investigating the effect of various counterflowing jet conditions/configurations on two supersonic slender-body models (cone-cylinder and quartic body of revolution). The study is aimed at gaining a better understanding of the relationship between the shock penetration length and reduction of drag and boom signature for these two supersonic slender-body configurations. Different jet flow rates, Mach numbers, nozzle jet exit diameters and jet-to-base diameter ratios were examined. The results show the characteristics of a short-to-long-to-short penetration-mode pattern with the increase of jet mass flow rates, observed across various counterflowing jet nozzle configurations. Though the optimal shock penetration length for potential boom-signature mitigation is tied to the long penetration mode, it often results in a very unsteady flow and leads to large oscillations of surface pressure and drag. Furthermore, depending on the geometry of the slender body, longer jet penetration did not always result in maximum drag reduction. For the quartic geometry, the maximum drag reduction corresponds well to the longest shock penetration length, while this was not the case for the cone-cylinder-as the geometry was already optimized for drag. Numerical results and assessments obtained from this parametric study along with the recommendation for future implementation of counterflowing jets as a means for drag and noise reduction are detailed in this paper.

Venkatachari, Balaji Shankar↗
NASA NTRS1992

Comparison of jet plume shape predictions and plume influence on sonic boom signature

An Euler shock-fitting marching code yields good agreement with semiempirically determined plume shapes, although the agreement decreases somewhat with increasing nozzle angle and the attendant increase in the nonisentropic nature of the flow. Some calculations for the low boom configuration with a simple engine indicated that, for flight at altitudes above 60,000 feet, the plume effect is dominant. This negates the advantages of a low boom design. At lower altitudes, plume effects are significant, but of the order that can be incorporated into the low boom design process.

Barger, Raymond L.↗
NASA NTRS2016

MONTE's Client-Based Trajectory Propagation Architecture

The Mission Analysis, Operations, and Navigation Toolkit Environment (MONTE) is JPL's (Jet Propulsion Laboratory's) signature astrodynamic computing platform. It supports all phases of space mission development, from early stage mission design and analysis through flight navigation services. MONTE employs a client-based trajectory propagation architecture where accelerations are calculated in the main MONTE library and the integrator exists on the periphery as a client. This paper outlines this approach to a trajectory propagation system and provides a concrete set of examples showing its utility.

Smith, Jonathan↗
NASA NTRS1987

Ozone, jet streaks and severe weather

Data from three independent observing platforms are synthesized to study the role of jet streaks in severe weather. The three data types are: conventional radiosondes; 6.7 micron water vapor imagery from the GOES satellite; and total ozone imagery from Nimbus 7. Diagnoses are then made of potential vorticity, mid-tropospheric moisture, and total ozone at and below the level of jet streaks. Potential vorticity and total ozone distributions are both tracers of stratospheric air. Theoretically, both should respond to the transverse, vertical circulations expected in the vicinity of jet streaks. Both should increase due to the sinking above the left front quadrant of the streaks. Moisture, on the other hand, increases in the ascent under the left front quadrant. This study shows striking agreement between the three parameters independently observed from three different observing platforms. Moreover, the three severe weather case studies suggest a unique distribution of ozone, potential vorticity, and mid-tropospheric moisture relative to a jet streak. This, in turn, led to the creation of a new ozone/jet streak model which shows that the total ozone distribution provides a signature in the vicinity of jet streaks and permits identification of areas most likely to experience severe weather at a later time. The value of such observations to operational forecasting is discussed.

Sechrist, Frank S.↗
NASA NTRS2017

Computational Support of 9x7 Wind Tunnel Test of Sonic Boom Models with Plumes

NASA and its industry partners are performing studies of supersonic aircraft concepts with low sonic boom pressure signatures. The interaction of the nozzle jet flow with the aircrafts' aft components is typically where the greatest uncertainly in the pressure signature is observed with high-fidelity numerical simulations. An extensive wind tunnel test was conducted in February 2016 in the NASA Ames 9- by 7- Foot Supersonic Wind Tunnel to help address the nozzle jet effects on sonic boom. Five test models with a variety of shock generators of differing waveforms and strengths were tested with a convergent-divergent nozzle for a wide range of nozzle pressure ratios. The LAVA unstructured flow solver was used to generate first CFD comparisons with the new experimental database using best practice meshing and analysis techniques for sonic boom vehicle design for all five different configurations. LAVA was also used to redesign the internal flow path of the nozzle and to better understand the flow field in the test section, both of which significantly improved the quality of the test data.

9x7 Wind Tunnel↗
NASA NTRS2016

A Model for Straight and Helical Solar Jets: II. Parametric Study of the Plasma Beta

Context. Jets are dynamic, impulsive, well-collimated plasma events that develop at many different scales and in different layers of the solar atmosphere. Aims. Jets are believed to be induced by magnetic reconnection, a process central to many astrophysical phenomena. Within the solar atmosphere, jet-like events develop in many different environments, e.g. in the vicinity of active regions as well as in coronal holes, and at various scales, from small photospheric spicules to large coronal jets. In all these events, signatures of helical structure and/or twisting/rotating motions are regularly observed. The present study aims to establish that a single model can generally reproduce the observed properties of these jet-like events. Methods. In this study, using our state-of-the-art numerical solver ARMS, we present a parametric study of a numerical tridimensional magnetohydrodynamic (MHD) model of solar jet-like events. Within the MHD paradigm, we study the impact of varying the atmospheric plasma beta on the generation and properties of solar-like jets. Results. The parametric study validates our model of jets for plasma beta ranging from 10(sup 3) to 1, typical of the different layers and magnetic environments of the solar atmosphere. Our model of jets can robustly explain the generation of helical solar jet-like events at various beta less than or equal to 1. We show that the plasma beta modifies the morphology of the helical jet, explaining the different observed shapes of jets at different scales and in different layers of the solar atmosphere. Conclusions. Our results allow us to understand the energisation, triggering, and driving processes of jet-like events. Our model allows us to make predictions of the impulsiveness and energetics of jets as determined by the surrounding environment, as well as the morphological properties of the resulting jets.

Magnetic Field↗
NASA NTRS2012

Disc-jet Coupling in the 2009 Outburst of the Black Hole Candidate H1743-322

We present an intensive radio and X-ray monitoring campaign on the 2009 outburst of the Galactic black hole candidate X-ray binary H1743-322. With the high angular resolution of the Very Long Baseline Array, we resolve the jet ejection event and measure the proper motions of the jet ejecta relative to the position of the compact core jets detected at the beginning of the outburst. This allows us to accurately couple the moment when the jet ejection event occurred with X-ray spectral and timing signatures. We find that X-ray timing signatures are the best diagnostic of the jet ejection event in this outburst, which occurred as the X-ray variability began to decrease and the Type C quasi-periodic oscillations disappeared from the X-ray power density spectrum. However, this sequence of events does not appear to be replicated in all black hole X-ray binary outbursts, even within an individual source. In our observations of H1743-322, the ejection was contemporaneous with a quenching of the radio emission, prior to the start of the major radio flare. This contradicts previous assumptions that the onset of the radio flare marks the moment of ejection. The jet speed appears to vary between outbursts with a positive correlation outburst luminosity. The compact core radio jet reactivated on transition to the hard intermediate state at the end of the outburst and not when the source reached the low hard spectral state. Comparison with the known near-infrared behaviour of the compact jets suggests a gradual evolution of the compact jet power over a few days near beginning the and end of an outburst

Miller-Jones, J. C. A.↗
NASA NTRS2019

Multiwavelength Study of Equatorial Coronal-Hole Jets

Jets (transient/collimated plasma ejections) occur frequently throughout the solar corona and contribute mass/energy to the corona and solar wind. By combining numerical simulations and high-resolution observations, we have made substantial progress recently on determining the energy buildup and release processes in these jets. Here we describe a study of 27 equatorial coronal-hole jets using Solar Dynamics Observatory/Atmospheric Imaging Assembly and Helioseismic and Magnetic Imager observations on 2013 June 27–28 and 2014 January 8–10. Out of 27 jets, 18 (67%) are associated with mini-filament ejections; the other nine (33%) do not show mini-filament eruptions but do exhibit mini-flare arcades and other eruptive signatures. This indicates that every jet in our sample involved a filament-channel eruption. From the complete set of events, six jets (22%) are apparently associated with tiny flux-cancellation events at the polarity inversion line, and two jets (7%) are associated with sympathetic eruptions of filaments from neighboring bright points. Potential-field extrapolations of the source-region photospheric magnetic fields reveal that all jets originated in the fan-spine topology of an embedded bipole associated with an extreme ultraviolet coronal bright point. Hence, all our jets are in agreement with the breakout model of solar eruptions. We present selected examples and discuss the implications for the jet energy buildup and initiation mechanisms.

Sun Activity↗
NASA NTRS2010

Observed Aspects of Reconnection in Solar Eruptions

Signatures of reconnection in major CME (coronal mass ejection)/flare eruptions and in coronal X-ray jets are illustrated and interpreted. The signatures are magnetic field lines and their feet that brighten in flare emission. CME/flare eruptions are magnetic explosions in which: 1. The field that erupts is initially a closed arcade. 2. At eruption onset, most of the free magnetic energy to be released is not stored in field bracketing a current sheet, but in sheared field in the core of the arcade. 3. The sheared core field erupts by a process that from its start or soon after involves fast tether-cutting reconnection at an initially small current sheet low in the sheared core field. If the arcade has oppositely-directed field over it, the eruption process from its start or soon after also involves fast breakout reconnection at an initially small current sheet between the arcade and the overarching field. These aspects are shown by the small area of the bright field lines and foot-point flare ribbons in the onset of the eruption. 4. At either small current sheet, the fast reconnection progressively unleashes the erupting core field to erupt with progressively greater force. In turn, the erupting core field drives the current sheet to become progressively larger and to undergo progressively greater fast reconnection in the explosive phase of the eruption, and the flare arcade and ribbons grow to become comparable to the pre-eruption arcade in lateral extent. In coronal X-ray jets: 1. The magnetic energy released in the jet is built up by the emergence of a magnetic arcade into surrounding unipolar "open" field. 2. A simple jet is produced when a burst of reconnection occurs at the current sheet between the arcade and the open field. This produces a bright reconnection jet and a bright reconnection arcade that are both much smaller in diameter that the driving arcade. 3. A more complex jet is produced when the arcade has a sheared core field and undergoes an ejective eruption in the manner of a miniature CME/flare eruption. The jet is then a combination of a miniature CME and the products of more widely distributed reconnection of the erupting arcade with the open field than in simple jets. Cartoons illustrating the above characteristics are presented along with representative examples of observed CME/flare eruptions and jets. The main point drawn to be drawn from the observations is that, for either a pre-eruption current sheet or a pre-simple-jet current sheet to remain quasi-static and stable against fast reconnection, it must remain much smaller in span than the driving arcade. Conversely, a current sheet comparable in span to the driving arcade can be made only dynamically, by eruption of the driving arcade, and continually undergoes massive fast reconnection.

Moore, Ronald L.↗
NASA NTRS2016

Wind Tunnel Model Design for Sonic Boom Studies of Nozzle Jet with Shock Interactions

NASA and Industry are performing vehicle studies of configurations with low sonic boom pressure signatures. The computational analyses of modern configuration designs have matured to the point where there is confidence in the prediction of the pressure signature from the front of the vehicle, but uncertainty in the aft signatures with often greater boundary layer effects and nozzle jet pressures. Wind tunnel testing at significantly lower Reynolds numbers than in flight and without inlet and nozzle jet pressures make it difficult to accurately assess the computational solutions of flight vehicles. A wind tunnel test in the NASA Ames 9- by 7-Foot Supersonic Wind Tunnel from Mach 1.6 to 2.0 will be used to assess the effects of shocks from components passing through nozzle jet plumes on the sonic boom pressure signature and provide datasets for comparison with CFD codes. A large number of high-fidelity numerical simulations of wind tunnel test models with a variety of shock generators that simulate horizontal tails and aft decks have been studied to provide suitable models for sonic boom pressure measurements using a minimally intrusive pressure rail in the wind tunnel. The computational results are presented and the evolution of candidate wind tunnel models is summarized and discussed in this paper.

Wind↗
NASA NTRS2016

Wind Tunnel Model Design for Sonic Boom Studies of Nozzle Jet Flows with Shock Interactions

NASA and the U.S. aerospace industry are performing studies of supersonic aircraft concepts with low sonic boom pressure signatures. The computational analyses of modern aircraft designs have matured to the point where there is confidence in the prediction of the pressure signature from the front of the vehicle, but uncertainty remains in the aft signatures due to boundary layer and nozzle exhaust jet effects. Wind tunnel testing without inlet and nozzle exhaust jet effects at lower Reynolds numbers than in-flight make it difficult to accurately assess the computational solutions of flight vehicles. A wind tunnel test in the NASA Ames 9- by 7-Foot Supersonic Wind Tunnel is planned for February 2016 to address the nozzle jet effects on sonic boom. The experiment will provide pressure signatures of test articles that replicate waveforms from aircraft wings, tails, and aft fuselage (deck) components after passing through cold nozzle jet plumes. The data will provide a variety of nozzle plume and shock interactions for comparison with computational results. A large number of high-fidelity numerical simulations of a variety of shock generators were evaluated to define a reduced collection of suitable test models. The computational results of the candidate wind tunnel test models as they evolved are summarized, and pre-test computations of the final designs are provided.

Wind Tunnel↗
NASA NTRS1998

Radar Backscatter Across the Gulf Stream Sea Surface Temperature Front

Ocean backscatter signatures were measured by the Jet Propulsion Laboratory airborne NUSCAT K(sub u)-band scatterometer across the Gulf Stream sea surface temperature front. The measurements were made during the Surface Wave Dynamics Experiment (SWADE) off the coast of Virginia and Maryland in the winter of 1991.

Ocean Backscatter Temperature front Gulf Stream↗
NASA NTRS2010

Characteristics of Gamma-Ray Loud Blazars in the VLBA Imaging and Polarimetry Survey

The radio properties of blazars detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope have been observed as part of the VLBA Imaging and Polarimetry Survey. This large, flux-limited sample of active galactic nuclei (AGNs) provides insights into the mechanism that produces strong gamma-ray emission. At lower flux levels, radio flux density does not directly correlate with gamma-ray flux. We find that the LAT-detected BL Lac objects tend to be similar to the non-LAT BL Lac objects, but that the LAT-detected FSRQs are often significantly different from the non-LAT FSRQs. The differences between the gamma-ray loud and quiet FSRQS can be explained by Doppler boosting; these objects appear to require larger Doppler factors than those of the BL Lac objects. It is possible that the gamma-ray loud FSRQs are fundamentally different from the gamma-ray quiet FSRQs. Strong polarization at the base of the jet appears to be a signature for gamma-ray loud AGNs.

LAT(LARGE AREA TELESCOPE)↗
NASA NTRS2016

Electron Scale Structures and Magnetic Reconnection Signatures in the Turbulent Magnetosheath

Collisionless space plasma turbulence can generate reconnecting thin current sheets as suggested by recent results of numerical magnetohydrodynamic simulations. The Magnetospheric Multiscale (MMS) mission provides the first serious opportunity to verify whether small ion-electron-scale reconnection, generated by turbulence, resembles the reconnection events frequently observed in the magnetotail or at the magnetopause. Here we investigate field and particle observations obtained by the MMS fleet in the turbulent terrestrial magnetosheath behind quasi-parallel bow shock geometry. We observe multiple small-scale current sheets during the event and present a detailed look of one of the detected structures. The emergence of thin current sheets can lead to electron scale structures. Within these structures, we see signatures of ion demagnetization, electron jets, electron heating, and agyrotropy suggesting that MMS spacecraft observe reconnection at these scales.

Yordanova, E.↗
NASA NTRS2016

MONTE Python for Deep Space Navigation

The Mission Analysis, Operations, and Navigation Toolkit Environment (MONTE) is the Jet Propulsion Laboratory’s (JPL) signature astrodynamic computing platform. It was built to support JPL’s deep space exploration program, and has been used to fly robotic spacecraft to Mars, Jupiter, Saturn, Ceres, and many solar system small bodies. At its core, MONTE consists of low-level astrodynamic libraries that are written in C++ and presented to the end user as an importable Python language module. These libraries form the basis on which Python-language applications are built for specific astrodynamic applications, such as trajectory design and optimization, orbit determination, flight path control, and more. The first half of this paper gives context to the MONTE project by outlining its history, the field of deep space navigation and where MONTE fits into the current Python landscape. The second half gives an overview of the main MONTE libraries and provides a narrative example of how it can be used for astrodynamic analysis.

aerospace↗