SEARCH · Search NASA

Results for “Signatures with jets”

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.

SourceResearch connectionFrom yearThrough year

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

At least 181 records · Page 10

All sources NASA NTRS DOE OSTI

NASA NTRS2014

Prediction of the Aero-Acoustic Performance of Open Rotors

The rising cost of jet fuel has renewed interest in contrarotating open rotor propulsion systems. Contemporary design methods offer the potential to maintain the inherently high aerodynamic efficiency of open rotors while greatly reducing their noise output, something that was not feasible in the 1980's designs. The primary source mechanisms of open rotor noise generation are thought to be the front rotor wake and tip vortex interacting with the aft rotor. In this paper, advanced measurement techniques and high-fidelity prediction tools are used to gain insight into the relative importance of the contributions to the open rotor noise signature of the front rotor wake and rotor tip vortex. The measurements include three-dimensional particle image velocimetry of the intra-rotor flowfield and the acoustic field of a model-scale open rotor. The predictions provide the unsteady flowfield and the associated acoustic field. The results suggest that while the front rotor tip vortex can have a significant influence on the blade passing tone noise produced by the aft rotor, the front rotor wake plays the decisive role in the generation of the interaction noise produced as a result of the unsteady aerodynamic interaction of the two rotors. At operating conditions typical of takeoff and landing operations, the interaction noise level is easily on par with that generated by the individual rotors, and in some cases is even higher. This suggests that a comprehensive approach to reducing open rotor noise should include techniques for mitigating the wake of the front rotor as well as eliminating the interaction of the front rotor tip vortex with the aft rotor blade tip.

VanZante, Dale↗

NASA NTRS2014

Prediction of the Aero-Acoustic Performance of Open Rotors

Van Zante, Dale E.↗

NASA NTRS1984

Some properties of transient phenomena in the extra-tropical region and their importance in the seasonal mean flow

When studying data for one season, it is convenient to divide transient eddies into those of the synoptic time scale and those of lower frequency. Where the dividing line is placed is not crucial, but a 10-day period is used in a study of the 1979-1980 Northern Hemisphere winter. The synoptic time scale eddies exhibit maximum kinetic energy in stormtracks slightly downstream from and poleward of the Atlantic and Pacific jet maximum. An alternative approach is via the anisotropic part of the horizontal velocity correlation tensor, the axis of which gives the local orientation of the eddies and the magnitude a measure of the extension of the eddies. When the man velocity field is almost that of the plane waves, the horizontal group velocity relative to the mean field is also related to this tensor. The synoptic time scale eddies force the mean flow in the sense of reducing the baroclinic component in the upstream of the region of the stormtrack. The lower frequency eddies have a very different signature.

Hoskins, B. J.↗

NASA NTRS2007

Shuttle Entry Imaging Using Infrared Thermography

During the Columbia Accident Investigation, imaging teams supporting debris shedding analysis were hampered by poor entry image quality and the general lack of information on optical signatures associated with a nominal Shuttle entry. After the accident, recommendations were made to NASA management to develop and maintain a state-of-the-art imagery database for Shuttle engineering performance assessments and to improve entry imaging capability to support anomaly and contingency analysis during a mission. As a result, the Space Shuttle Program sponsored an observation campaign to qualitatively characterize a nominal Shuttle entry over the widest possible Mach number range. The initial objectives focused on an assessment of capability to identify/resolve debris liberated from the Shuttle during entry, characterization of potential anomalous events associated with RCS jet firings and unusual phenomenon associated with the plasma trail. The aeroheating technical community viewed the Space Shuttle Program sponsored activity as an opportunity to influence the observation objectives and incrementally demonstrate key elements of a quantitative spatially resolved temperature measurement capability over a series of flights. One long-term desire of the Shuttle engineering community is to calibrate boundary layer transition prediction methodologies that are presently part of the Shuttle damage assessment process using flight data provided by a controlled Shuttle flight experiment. Quantitative global imaging may offer a complementary method of data collection to more traditional methods such as surface thermocouples. This paper reviews the process used by the engineering community to influence data collection methods and analysis of global infrared images of the Shuttle obtained during hypersonic entry. Emphasis is placed upon airborne imaging assets sponsored by the Shuttle program during Return to Flight. Visual and IR entry imagery were obtained with available airborne imaging platforms used within DoD along with agency assets developed and optimized for use during Shuttle ascent to demonstrate capability (i.e., tracking, acquisition of multispectral data, spatial resolution) and identify system limitations (i.e., radiance modeling, saturation) using state-of-the-art imaging instrumentation and communication systems. Global infrared intensity data have been transformed to temperature by comparison to Shuttle flight thermocouple data. Reasonable agreement is found between the flight thermography images and numerical prediction. A discussion of lessons learned and potential application to a potential Shuttle boundary layer transition flight test is presented.

Horvath, Thomas↗

NASA NTRS2005

Unveiling the High Energy Obscured Universe: Hunting Collapsed Objects Physics

A large part of energy from space is coming from collapsing stars (SN, Hypernovae) and collapsed stars (black holes, neutron stars and white dwarfs). The peak of their energy release is in the hard-X and gamma-ray wavelengths where photons are insensitive to absorption and can travel from the edge the Universe or the central core of the Galaxy without loosing the primordial information of energy, time signature and polarization. The most efficient process to produce energetic photons is gravitational accretion of matter from a "normal" star onto a collapsed companion (L~GxMcollxdMacc/dtx( 1Rdisc)-dMacc/dt x c2), exceeding by far the nuclear reaction capability to generate high energy quanta. Thus our natural laboratory for "in situ" investigations are collapsed objects in which matter and radiation co-exist in extreme conditions of temperature and density due to gravitationally bent geometry and magnetic fields. This is a unique opportunity to study the physics of accretion flows in stellar mass and super-massive Black Holes (SMBHs), plasmoids generated in relativistic jets in galactic microQSOs and AGNs, ionised plasma interacting at the touching point of weakly magnetized NS surface, GRB/Supernovae connection, and the mysterious origins of "dark" GRB and X-ray flash.

Ubertini, P.↗

NASA NTRS2017

Feeding and Feedback in the Powerful Radio Galaxy 3C 120

We present a spectral analysis of a 200-kilosecond observation of the broad-line radio galaxy 3C 120, performed with the high-energy transmission grating spectrometer on board the Chandra X-Ray Observatory. We find (i) a neutral absorption component intrinsic to the source with a column density of log N (sub H) equals 20.67 plus or minus 0.05 square centimeters; (ii) no evidence for a warm absorber (WA) with an upper limit on the column density of just log N (sub H) less than 19.7 square centimeters, assuming the typical ionization parameter log xi approximately equal to 2.5 ergs per second per centimeter; the WA may instead be replaced by (iii) a hot emitting gas with a temperature kT approximately equal to 0.7 kiloelectronvolts observed as soft X-ray emission from ionized Fe L-shell lines, which may originate from a kiloparsec-scale shocked bubble inflated by the active galactic nucleus (AGN) wind or jet with a shock velocity of about 1000 kilometers per second determined by the emission line width; (iv) a neutral Fe K alpha line and accompanying emission lines indicative of a Compton-thick cold reflector with a low reflection fraction R approximately equal to 0.2, suggesting a large opening angle of the torus; (v) a highly ionized Fe XXV emission feature indicative of photoionized gas with an ionization parameter log xi equal to 3.75 (sup plus 0.38) (sub minus 0.27) ergs per second per centimeter and a column density of log N (sub H) greater than 22 square centimeters localized within approximately 2 pc from the X-ray source; and (vi) possible signatures of a highly ionized disk wind. Together with previous evidence for intense molecular line emission, these results indicate that 3C 120 is likely a late-state merger undergoing strong AGN feedback.

black hole physics â€“ galaxies: active â€“ line: ↗

NASA NTRS2020

Evidence for Magnetic Activity at Starbirth: a Powerful X-ray Flare From the Class 0 Protostar HOPS 383

Context. Class 0 protostars represent the earliest evolutionary stage of solar-type stars, during which the majority of the system mass resides in an infalling envelope of gas and dust and not yet in the central, nascent star. Although X-rays are a key signature of magnetic activity in more evolved protostars and young stars, whether such magnetic activity is present at the Class 0 stage is still debated. Aims. We aim to detect a bona fide Class 0 protostar in X-rays. Methods. We observed HOPS 383 in 2017 December in X-rays with the Chandra X-ray Observatory (~84 ks) and in near-infrared imaging with the Southern Astrophysical Research Telescope (SOAR). Results. HOPS 383 was detected in X-rays during a powerful flare. This hard (E > 2 keV) X-ray counterpart was spatially coincident with the northwest 4-cm component of HOPS 383, which would be the base of the radio thermal jet launched by HOPS 383. The flare duration was ~3.3 h; at the peak, the X-ray luminosity reached ~4 x 10(exp 31) erg/s in the 2–8 keV energy band, a level at least an order of magnitude larger than that of the undetected quiescent emission from HOPS 383. The X-ray flare spectrum is highly absorbed (N(H) ~ 7 x 10(exp 23) per sq.cm), and displays a 6.4 keV emission line with an equivalent width of ~1:1 keV, arising from neutral or low-ionization iron. Conclusions. The detection of a powerful X-ray flare from HOPS 383 constitutes direct proof that magnetic activity can be present at the earliest formative stages of solar-type stars.

Nicolas Grosso↗

NASA NTRS2017

Retroreflective Background Oriented Schlieren Imaging Results from the NASA Plume/Shock Interaction Test

In support of NASA's Commercial Supersonics Technology (CST) project, a test was conducted in the 9-by-7 ft. supersonic section of the NASA Ames Unitary Plan Wind Tunnel (UPWT). The tests were designed to study the interaction of shocks with a supersonic jet characteristic of those that may occur on a commercial supersonic aircraft. Multiple shock generating geometries were tested to examine the interaction dynamics as they pertain to sonic boom mitigation. An integral part of the analyses of these interactions are the interpretation of the data generated from the retroreflective Background Oriented Schlieren (RBOS) imaging technique employed for this test. The regularization- based optical flow methodology used to generate these data is described. Sample results are compared to those using normalized cross-correlation. The reduced noise, additional feature detail, and fewer false artifacts provided by the optical flow technique produced clearer time-averaged images, allowing for better interpretation of the underlying flow phenomena. These images, coupled with pressure signatures in the near field, are used to provide an overview of the detailed interaction flowfields.

optical flow↗

NASA NTRS2002

Application of DPIV to Enhanced Mixing Heated Nozzle Flows

Digital Particle Imaging Velocimetry (DPIV) is a planar velocity measurement technique that continues to be applied to new and challenging engineering research facilities while significantly reducing facility test time. DPIV was used in the GRC Nozzle Acoustic Test Rig (NATR) to characterize the high temperature (560 C), high speed (is greater than 500 m/s) flow field properties of mixing enhanced jet engine nozzles. The instantaneous velocity maps obtained using DPIV were used to determine mean velocity, rms velocity and two-point correlation statistics to verify the true turbulence characteristics of the flow. These measurements will ultimately be used to properly validate aeroacoustic model predictions by verifying CFD input to these models. These turbulence measurements have previously not been possible in hot supersonic jets. Mapping the nozzle velocity field using point based techniques requires over 60 hours of test time, compared to less than 45 minutes using DPIV, yielding a significant reduction in testing time. A dual camera DPIV configuration was used to maximize the field of view and further minimize the testing time required to map the nozzle flow. The DPIV system field of view covered 127 by 267 mm. Data were acquired at 19 axial stations providing coverage of the flow from the nozzle exit to 2.37 in downstream. At each measurement station, 400 image frame pairs were acquired from each camera. The DPIV measurements of the mixing enhanced nozzle designs illustrate the changes in the flow field resulting in the reduced noise signature.

Wernet, Mark P.↗

NASA NTRS1989

Prediction and measurement of low-frequency harmonic noise of a hovering model helicopter rotor

Far-field acoustic data for a model helicopter rotor have been gathered in a large open-jet, acoustically treated wind tunnel with the rotor operating in hover and out of ground-effect. The four-bladed Boeing 360 model rotor with advanced airfoils, planform, and tip shape was run over a range of conditions typical of today's modern helicopter main rotor. Near in-plane acoustic measurements were compared with two independent implementations of classical linear theory. Measured steady thrust and torque were used together with a free-wake analysis (to predict the thrust and drag distributions along the rotor radius) as input to this first-principles theoretical approach. Good agreement between theory and experiment was shown for both amplitude and phase for measurements made in those positions that minimized distortion of the radiated acoustic signature at low-frequencies.

Aggarawal, H. R.↗

NASA NTRS2010

Reevaluating the Role of Saharan Air Layer in Atlantic Tropical Cyclogenesis and Evolution

The existence of the Saharan air layer (SAL), a layer of warm, dry, dusty air that frequently moves westward off of the Saharan desert of Africa and over the tropical Atlantic Ocean, has long been appreciated. As air moves over the desert, it is strongly heated from below, producing a very hot air mass at low levels. Because there is no moisture source over the Sahara, the rise in temperature causes a sharp drop in relative humidity, thus drying the air. In addition, the warm air produces a very strong jet of easterly flow in the middle troposphere called the African easterly jet that is thought to play a critical role in hurricane formation. In recent years, there has been an increased focus on the impact that the SAL has on the formation and evolution of hurricanes in the Atlantic. However, the nature of its impact remains unclear, with some researchers arguing that the SAL amplifies hurricane development and with others arguing that it inhibits it. The argument for positively influencing hurricane development is based upon the fact that the African easterly jet provides an energy source for the waves that eventually form hurricanes and that it leads to rising motion south of the jet that favors the development of deep thunderstorm clouds. The potential negative impacts of the SAL include 1) low-level vertical wind shear associated with the African easterly jet; 2) warm SAL air aloft, which increases thermodynamic stability and suppresses cloud development; and 3) dry air, which produces cold downdrafts in precipitating regions, thereby removing energy needed for storm development. As part of this recent focus on the SAL and hurricanes (which motivated a 2006 NASA field experiment), there has been little emphasis on the SAL s potential positive influences and almost complete emphasis on its possible negative influences, almost to the point of claims that the SAL is the major suppressing influence on hurricanes in the Atlantic. In this study, multiple NASA satellite data sets (TRMM, MODIS, CALIPSO, and AIRS/AMSU) and National Centers for Environmental Prediction global analyses are used to see if the proposed negative influences deserve all of the attention they have recently received. The results show that storms generally form on the southern side of the African jet, where favorable background rotation is high. The jet often helps to form the northern side of the storms and is typically stronger in storms that intensify than those that weaken, suggesting that jet-induced vertical wind shear is not a negative influence on developing storms. Warm SAL air is confined to regions north of the jet and generally does not impact the tropical cyclone precipitation south of the jet. A comparison of the environments of strongly strengthening storms and of weakening storms shows no differences in SAL structure, indicating that the SAL has little influence on whether storms weaken or intensify. The large-scale flow at upper levels above the SAL was found to be most important, with the environment of strengthening storms having very little vertical wind shear and also favoring more expansive outflow from the storm. The SAL is shown to occur in a large-scale environment that is already characteristically dry as a result of large-scale subsidence (sinking air motions). Strong surface heating and deep dry convective mixing enhance dryness at low levels, but moisten the air at midlevels. Therefore, mid-to-upper-level dryness is not a defining characteristic of the SAL, but is instead a signature of subsidence. As a result, we conclude that the SAL is not the major negative influence on hurricanes that recent studies have emphasized. It is just one of many possible influences and can be both positive and negative.

Braun, Scott A.↗

NASA NTRS2000

Remotely-Sensed Geology from Lander-Based to Orbital Perspectives: Results for FIDO Rover Field Tests

Tests of the FIDO (Field Integration Design and Operations) rover and Athena-like operational scenarios were conducted May 7-16, 2000. A group located at the Jet Propulsion Lab, Pasadena, CA, formed the Core Operations Team (COT) that designed experiments and command sequences while another team tracked, maintained, and secured the rover in the field. The COT had no knowledge of the specific field location, thus the tests were done "blind." In addition to FIDO rover instrumentation, the COT had access to LANDSAT 7, TIMS, and AVIRIS regional coverage and color descent images. Using data from the FIDO instruments, primarily a color microscopic imager (CMI), infrared point spectrometer (IPS; 1.5-2.4 microns), and a three-color stereo panoramic camera (Pancam), the COT correlated lithologic features (mineralogy, rock types) from the simulated landing site to a regional scale. The May test results provide an example of how to relate site geology from landed rover investigations to the regional geology using remote sensing. The capability to relate mineralogic signatures using the point IR spectrometer to remotely sensed, multispectral or hyperspectral data proved to be key to integration of the in-situ and remote data. This exercise demonstrated the potential synergy between lander-based and orbital data, and highlighted the need to investigate a landing site in detail and at multiple scales.

Jolliff, B.↗

NASA NTRSDate not supplied

Assessing Organic Preservation and the Implications for Potential Biosignatures in the Bastide Member of the Séítah Formation, Jezero Crater

Introduction: Olivine has the highest CO2 trapping potential of ultramafic minerals, due to its rapid rate of dissolution and high percentage of divalent cations/unpolymerized silicate tetrahedra [1]. It generates divalent carbonates from CO2 and sequesters CO2 into the mineral matrix of the target lithology. The co-occurrence of olivine and carbonate within abraded targets from the Bastide Member of the Séítah Formation (Fm) of the Jezero crater floor [2] suggests the carbonation of olivine occurred within the mineral matrix hosted in a subsurface system. Hydrothermal origins for the subsurface system are hypothesized from orbital data [3]. This is supported by the detection of hydration features within the rock as well as the carbonate features are solely detected within the abrasion patch but not the rock’s surface. Organic preservation potential of abrasion patches: We incorporated the SHERLOC/WATSON results acquired from the Dourbes, Garde, and Quartier abrasion patches in the Séítah Fm to investigate the organomineral associations, and determine the biosignature preservation potential of these rocks. Dourbes is dominated by olivine and has minor amounts of carbonate, hydrated Ca-sulfate, and amorphous or microcrystalline silicate. Fluorescence features (330-340 nm) are detected in discrete locales and could be consistent with double ring aromatic organic molecules; yet, these features do not appear to be associated with an identified mineral phase. Dark subhedral to euhedral olivine grains within the Garde abrasion patch often co-occur with carbonate-consistent spectral signatures in all analyzed scans. The availability of Fe2+ is a known influence on olivine dissolution rates [1] and SuperCam estimates of the olivine composition (Forsterite-60 average for Sols 202-234) may thereby provide a constraint on the carbonation extent. Carbonated olivine phenocrysts within the matrix may be due to aqueous alteration, as the carbonation of nodules is consistent with observations in other hydrothermal systems and within Martian meteorites (ALH84001) [4]. In comparison, the Quartier abrasion patch represents an extensively altered endmember within the Bastide Member of the Séítah Fm. It contains a fluorescence doublet at 305/325 nm that coexists with multiple species of Na-sulfate and Mg-sulfate, Mg-carbonates, olivine [5]. Aqueous alteration and implications for habitability: The identification of primary and secondary mineral phases observed in the Bastide Member suggests the release of cations from primary ultramafic minerals through aqueous alteration. Within Garde, the carbonate detected appears to be Mg-rich and likely formed from the in situ alteration of Mg-rich olivine within the region as carbonate has only been detected within the rock via in situ analysis. Carbonates derived from abiotic and biotic reactions preserve biosignatures (i.e. indices of habitability) on Earth. The detected carbonate phase found in association with fluorescent features within the rock matrix may also indicate potential organic compounds preserved in a putative hydrothermal system. Fluorescent features (~330 nm) are unique to Garde and Dourbes, though they are co-located to carbonate signatures solely within Garde, and between the light toned minerals. Identification of these fluorescent features may be consistent with 1-2 ring aromatic compounds. The limit of detection for Raman is multiple orders of magnitude greater than the limit of detection required for fluorescence [6]. Implications for provenance: Hydrothermal systems represent disequilibrium chemical conditions that are hypothesized to have supported the emergence of life and also preserve ancient carbon within precipitated carbonates [7]. Hydrothermal system associated carbonates are capable of preserving biosignatures up to an estimated ~3.77 – 4.28 Gya [8]. Thus, carbonated olivine found within the Séítah Fm may represent a high-potential biosignature preserving environment on Mars. The formation of carbonates by an aqueous alteration process, such as carbonation of olivine is also consistent with hypotheses for carbonate within the greater regional-olivine bearing unit [2,3], which contains Garde, Dourbes, and Quartier. Acknowledgments: This work was carried out at the Jet Propulsion Laboratory, The California Institute of Technology under a contract from NASA. References: [1] Wood et al., (2019) ES&T, 6, 10. [2] Stack, K. et al., (2020) Space Sci Rev, 216, 127. [3] Tarnas, J. et al., (2021) JGR: Planets, 126, 11. [4] Steele et al., (2007) Meteorit. Planet. Sci., 42, 9. [5] Murphy, A.E. et al., (2022) LPSC [6] Bhartia et al., (2021) Space Sci Rev, 217, 58. [7] Luther (2021) GRL, 48, e2021GL094869. [8] Dodd et al., (2017) Nature, 543, 60-64

E L Cardarelli↗

NASA NTRS2007

Flight Testing of the Gulfstream Quiet Spike(TradeMark) on a NASA F-15B

Gulfstream Aerospace has long been interested in the development of an economically viable supersonic business jet (SBJ). A design requirement for such an aircraft is the ability for unrestricted supersonic flight over land. Although independent studies continue to substantiate that a market for a SBJ exists, regulatory and public acceptance challenges still remain for supersonic operation over land. The largest technical barrier to achieving this goal is sonic boom attenuation. Gulfstream's attention has been focused on fundamental research into sonic boom suppression for several years. This research was conducted in partnership with the NASA Aeronautics Research Mission Directorate (ARMD) supersonic airframe cruise efficiency technical challenge. The Quiet Spike, a multi-stage telescopic nose boom and a Gulfstream-patented design (references 1 and 2), was developed to address the sonic boom attenuation challenge and validate the technical feasibility of a morphing fuselage. The Quiet Spike Flight Test Program represents a major step into supersonic technology development for sonic boom suppression. The Gulfstream Aerospace Quiet Spike was designed to reduce the sonic boom signature of the forward fuselage for an aircraft flying at supersonic speeds. In 2004, the Quiet Spike Flight Test Program was conceived by Gulfstream and NASA to demonstrate the feasibility of sonic boom mitigation and centered on the structural and mechanical viability of the translating test article design. Research testing of the Quiet Spike consisted of numerous ground and flight operations. Each step in the process had unique objectives, and involved numerous test team members from the NASA Dryden Flight Research Center (DFRC) and Gulfstream Aerospace. Flight testing of the Quiet Spike was conducted at the NASA Dryden Flight Research Center on an F-15B aircraft from August, 2006, to February, 2007. During this period, the Quiet Spike was flown at supersonic speeds up to Mach 1.8 at the maximum design dynamic pressure of 685 pounds per square foot. Extension and retraction tests were conducted at speeds up to Mach 1.4. The design of the Quiet Spike to shape the forward shock wave environment of the aircraft was confirmed during near-field shock wave probing at Mach 1.4. Thirty-two flights were performed without incident and all project objectives were achieved. The success of the Quiet Spike Flight Test Program represents an important step towards developing commercial aircraft capable of supersonic flight over land within the continental United States and in international airspace.

Smolka, James W.↗

NASA NTRS1999

Microflaring in Low-Lying Core Fields and Extended Coronal Heating in the Quiet Sun

We have previously reported analyses of Yohkoh SXT data examining the relationship between the heating of extended coronal loops (both within and stemming from active regions) and microflaring in core fields lying along neutral lines near their footpoints (J. G. Porter, D. A. Falconer, and R. L. Moore 1998, in Solar Jets and Coronal Plumes, ed. T. Guyenne, ESA SP-421, and references therein). We found a surprisingly poor correlation of intensity variations in the extended loops with individual microflares in the compact heated areas at their feet, despite considerable circumstancial evidence linking the heating processes in these regions. Now, a study of Fe XII image sequences from SOHO EIT show that similar associations of core field structures with the footpoints of very extended coronal features can be found in the quiet Sun. The morphology is consistent with the finding of Wang et al. (1997, ApJ 484, L75) that polar plumes are rooted at sites of mixed polarity in the magnetic network. We find that the upstairs/downstairs intensity variations often follow the trend, identified in the active region observations, of a weak correspondence. Apparently much of the coronal heating in the extended loops is driven by a type of core field magnetic activity that is "cooler" than the events having the coronal signature of microflares, i.e., activity that results in little heating within the core fields themselves. This work was funded by the Solar Physics Branch of NASA's Office of Space Science through the SR&T Program and the SEC Guest Investigator Program.

Porter, Jason G.↗

NASA NTRS2022

Electromagnetic Time and Wavelength Domain Predictions for Accreting Binary Black Holes

Accreting massive binary black holes in gaseous environments are keymulti-messenger sources for the LISA mission. We will present some ofthe latest predictions of the observational signatures of accreting binary black holes across the electromagnetic spectrum from the fieldand provide some of our own. In particular, we will provide a briefsummary of the progress made in our group to understand these systemstheoretically using high-performance simulations of generalrelativistic magnetohydrodynamics (MHD) and dynamic spacetimes.Simulating these systems realistically is challenging asradiation-coupled MHD must be considered over large dynamic ranges inspace and time. Constraining our view to the circumbinary disk regionfirst, we will show how the evolution duration, accretion disk size,mass ratio, and thermodynamics model affect the structure andvariability of the accretion flow. We particularly emphasize how theseparameters influence the over-density feature, or "lump", which orbitsthe binary near the edge of the cavity, since it is responsible formost of the electromagnetic emission's variability---a key signatureof a system being a binary. Extending to smaller length scales, wewill report on simulations following accretion all the down to theevent horizons so that we may begin to investigate how black hole spinaffects mini-disk dynamics, accretion rate, and jet power. We willalso report on our radiative transfer predictions for how black holespin alters the spectral energy distribution of these systems.Wrapping up, we will itemize the remaining key theoreticaltechnologies and directions needed to be accomplished to betterunderstand these sources, and assess strategies for searching for themin the coming decade.

Scott C Noble↗

NASA NTRS2012

The Impact of Geometrical Constraints on Collisionless Magnetic Reconnection

One of the most often cited features associated with collisionless magnetic reconnection is a Hall-type magnetic field, which leads, in antiparallel geometries, to a quadrupolar magnetic field signature. The combination of this out of plane magnetic field with the reconnection in-plane magnetic field leads to angling of magnetic flux tubes out of the plane defined by the incoming magnetic flux. Because it is propagated by Whistler waves, the quadrupolar field can extend over large distances in relatively short amounts of time - in fact, it will extend to the boundary of any modeling domain. In reality, however, the surrounding plasma and magnetic field geometry, defined, for example, by the overall solar wind flow, will in practice limit the extend over which a flux tube can be angled out of the main plain. This poses the question to what extent geometric constraints limit or control the reconnection process and this is the question investigated in this presentation. The investigation will involve a comparison of calculations, where open boundary conditions are set up to mimic either free or constrained geometries. We will compare momentum transport, the geometry of the reconnection regions, and the acceleration if ions and electrons to provide the current sheet in the outflow jet.

Hesse, Michael↗

NASA NTRS2004

Remote Measurements of Snowfalls in Wakasa Bay, Japan with Airborne Millimeter- wave Imaging Radiometer and Cloud Radar

In this paper we explore the application of combined millimeter-wave radar and radiometry to remotely measure snowfall. During January-February of 2003, a field campaign was conducted with the NASA P-3 aircraft in Wakasa Bay, Japan for the validation of the AMSRE microwave radiometer on board the Aqua satellite. Among the suite of instruments-on board the P-3 aircraft were the Millimeter-wave Imaging Radiometer (MIR) from the NASA Goddard Space Flight Center and the 94 GHz Airborne Cloud Radar (ACR) which is co-owned and operated by NASA Jet Propulsion Laboratory/University of Massachusetts. MIR is a total power, across-track scanning radiometer that measures radiation at the frequencies of 89, 150, 183.3 +/- 1, 183.3 +/- 3, 183.3 +/-7, 220, and 340 GHz. The MIR has flown many successful missions since its completion in May 1992. ACR is a newer instrument and flew only a few times prior to the Wakasa Bay deployment. These two instruments which are particularly well suited for the detection of snowfall functioned normally during flights over snowfall and excellent data sets were acquired. On January 14, 28, and 29 flights were conducted over snowfall events. The MIR and ACR detected strong signals during periods of snowfall over ocean and land. Results from the analysis of these concurrent data sets show that (1) the scattering of millimeter-wave radiation as detected by the MIR is strongly correlated with ACR radar reflectivity profiles, and (2) the scattering is highly frequency-dependent, the higher the frequency the stronger the scattering. Additionally, the more transparent channels of the MIR (e.g., 89, 150, and 220 GHz) are found to display ambiguous signatures of snowfall because of their exposure to surface features. Thus, the snowfall detection and retrievals of snowfall parameters, such as the ice water path (IWP) and median mass diameter (D(me)) are best conducted at the more opaque channels near 183.3 GHz and 340 GHz. Retrievals of IWP and D(me) using the MIR measurements at 183.3 and 340 GHZ are currently in progress, and the results will be compared with those derived from the ACR reflectivity profiles. Implication from this comparison will be discussed.

Wang, J. R.↗