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At least 577 records · Page 32
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NASA NTRS2014

Three-Dimensional Magnetic Restructuring in Two Homologous Solar Flares in the Seismically Active NOAA AR 11283

We carry out a comprehensive investigation comparing the three-dimensional magnetic field restructuring, flare energy release, and the helioseismic response of two homologous flares, the 2011 September 6 X2.1 (FL1) and September 7 X1.8 (FL2) flares in NOAA AR 11283. In our analysis, (1) a twisted flux rope (FR) collapses onto the surface at a speed of 1.5 km s(exp−1) after a partial eruption in FL1. The FR then gradually grows to reach a higher altitude and collapses again at 3 km s(exp−1) after a fuller eruption in FL2. Also, FL2 shows a larger decrease of the flux-weighted centroid separation of opposite magnetic polarities and a greater change of the horizontal field on the surface. These imply a more violent coronal implosion with corresponding more intense surface signatures in FL2. (2) The FR is inclined northward and together with the ambient fields, it undergoes a southward turning after both events. This agrees with the asymmetric decay of the penumbra observed in the peripheral regions. (3) The amounts of free magnetic energy and nonthermal electron energy released during FL1 are comparable to those of FL2 within the uncertainties of the measurements. (4) No sunquake was detected in FL1; in contrast, FL2 produced two seismic emission sources S1 and S2 both lying in the penumbral regions. Interestingly, S1 and S2 are connected by magnetic loops, and the stronger source S2 has a weaker vertical magnetic field. We discuss these results in relation to the implosion process in the low corona and the sunquake generation.

Sun: X-rays↗
NASA NTRSDate not supplied

Future Arctic (Wild) Fires

Wildland fires in the boreal and Arctic are increasing in frequency and severity, with extreme fire seasons documented across the Pan-Arctic and boreal in five of the last seven years – including an early start to extreme fires in 2023.Human-caused and wildland fires above 60°N were larger sources of black carbon and methane than current modeled estimates of anthropogenic sectors like energy extraction and transportation. Further, these large boreal and Arctic fires have the potential to release large amounts of carbon dioxide and subsequent methane emissions from degraded permafrost and peat fires, as well as negatively impacting air quality thousands of miles south. By end of this century, current extreme fire years in the Arctic will likely be a normal fire year for much of Greenland, North America, Northern Europe, and Eurasia. As a new horizon in global wildland fire science, novel scientific pathways must be undertaken to improve our understanding and management of wildfires in the High Northern Latitudes – including understanding how NASA and U.S. researchers can enhance collaboration and develop near-real-time fire and smoke monitoring and modeling between North American and European ecology, fire, and climate scientists and stakeholders. Issues of inclusion, diversity, and equity are inherent to understanding fire ecology, impacts, and management in the Arctic and boreal, including centering and deferring to Indigenous and local communities when constructing best management practices.

Future↗
NASA NTRS2000

A Simulation of Bromoform's Contribution to Stratospheric Bromine

Many chlorinated and brominated compounds that are inert in the troposphere are destroyed in the stratosphere and act as an in-situ source of stratospheric reactive chlorine and bromine. Other halogenated compounds that are reactive in the troposphere might contribute to the stratosphere's halogen budget in two ways. First, like their unreactive companions, rapid convective transport might carry them to the upper troposphere and make them available for subsequent advection by the mean circulation into the stratosphere before they are oxidized or photolyzed. Second, it is more likely that they are destroyed in the troposphere, and the chlorine and bromine that is released might then be transported to the stratosphere. We evaluate the relative influence of these processes on stratospheric bromine in a three-dimensional chemistry and transport model which simulates the distribution of bromoform (CHBr3). CHBr3 is parameterized as a short-lived, ocean-surface source gas whose destruction by photolysis and reaction with hydroxyl (OH) in the troposphere and stratosphere yields inorganic bromine (Br(sub y)). Many of the observed features of CHBr3 are simulated well, and comparisons with observations are used to show that the model represents aspects of transport in the upper troposphere and lower stratosphere that are critical to the evaluation. In particular, the model maintains the observed troposphere-stratosphere distinctness in transport pathways and reproduces the observed seasonal dependence of the mixture of air in the middle- and high-latitude lowermost stratosphere. We estimate that adding CHBr3 to models which already include the long-lived organic brominated compounds (halons and methyl bromide) will increase the simulated stratospheric mass of Br(sub y) by about 15 percent. In-situ stratospheric destruction of CHBr3 produces Br(sub y) in amounts which are comparable to that transported into the stratosphere after photolysis and oxidation of CHBr3 in the troposphere. In our simulations the mass of Br(sub y) produced from the destruction of CHBr3 does not exceed the mass of Br(sub y) produced from the destruction of the long-lived compounds at any level in the stratosphere. However, Br(sub y) from the loss of CHBr3 accounts for approximately one-third of the total Br(sub y) in the lowest kilometer of the stratosphere.

Nielsen, J. Eric↗
NASA NTRS1984

Methane concentrations and source strengths in urban locations

The results of a six year measurement of trace gases in 18 different urban and remote areas throughout the Northern and Southern Hemispheres are reported. It is found that the measurements are consistent with a yearly atmospheric release of 30 to 60 megatons of CH4 in urban environments. Concentrations of CCl3F, CCl2F2, and CH3CCl3 were also found to be higher in the same urban samples than in corresponding samples from remote areas. The 'urban excess' (urban concentration minus remote concentration) was generally 1000 to 2000 times larger on a molar basis for CH4 than for CCl3F. The fraction of world-wide methane release occurring in the urban environment is estimated from the concentration ratios for CH4 vs CCl3F. It is shown that about 8 to 15 percent of atmospheric methane release occurs in urban areas.

Blake, D. R.↗
NASA NTRS2012

GX 3+1: The Stability of Spectral Index as a Function of Mass Accretion Rate

We present an analysis of the spectral and timing properties observed in X-rays from neutron star (NS) binary GX 3+1 (4U 1744-26) during long-term transitions between the faint and bright phases superimposed on short-term transitions between lower banana (LB) and upper banana (UB) branches in terms of its color-color diagram, We analyze all observations of this source obtained with the Rossi X-ray Timing Explorer and BeppoSAX satellites, We find that the X-ray broadband energy spectra during these spectral transitions can be adequately reproduced by a composition of a low-temperature blackbody component, a Comptonized component (COMPTB), and Gaussian component We argue that the electron temperature kTe of the Compton cloud monotonically increases from 2.3 keY to 4.5 keY, when GX 3+1 makes a transition from UB to LB. We also detect an evolution of noise components (a very low frequency noise and a high-frequency noise) during these LB-UB transitions. Using a disk seed photon normalization of COMPTB, which is proportional to the mass accretion rate, we find that the photon power-law index Gamma is almost constant (Gamma = 2.00 +/- 0.02) when mass accretion rate changes by factor four. In addition, we find that the emergent spectrum is dominated by the strong Comptonized component We interpret this quasi-stability of the index Gamma and a particular form of the spectrum in the framework of a model in which the energy release in the transition layer located between the accretion disk and NS surface dominates that in the disk. Moreover, this index stability effect now established for GX 3+ I was previously found in the atoll source 4U 1728-34 and suggested for a number of other low-mass X-ray NS binaries. This intrinsic behavior of NSs, in particular for atoll sources, is fundamentally different from that seen in black hole binary sources where the index monotonically increases during spectral transition from the low state to the high state and then finally saturates at high values of mass accretion rate.

Seifana, Elena↗
NASA NTRS1972

Source deck compression and update program (CAPS)

Computer program for compressing program source decks and other data coded in Hollerith format is described. Compression of card image record by substitution of special code characters is discussed. Program is written for IBM 360/75/95 Release 19 computer.

Merrill, E. O.↗
NASA NTRS1971

A study of an advanced confined linear energy source

A literature survey and a test program to develop and evaluate an advanced confined linear energy source were conducted. The advanced confined linear energy source is an explosive or pyrotechnic X-Cord (mild detonating fuse) supported inside a confining tube capable of being hermetically sealed and retaining all products of combustion. The energy released by initiation of the X-Cord is transmitted through the support material to the walls of the confining tube causing an appreciable change in cross sectional configuration and expansion of the tube. When located in an assembly that can accept and use the energy of the tube expansion, useful work is accomplished through fracture of a structure, movement of a load, reposition of a pin, release of a restraint, or similar action. The tube assembly imparts that energy without release of debris or gases from the device itself. This facet of the function is important to the protection of men or equipment located in close proximity to the system during the time of function.

Anderson, M. C.↗
NASA NTRS1973

Lunar atmospheric composition results from Apollo 17

The Apollo 17 mass spectrometer has confirmed the existence of helium, neon, argon, and possibly molecular hydrogen in the lunar atmosphere. Helium and neon concentrations are in agreement with model predictions based on the solar wind as a source and their being noncondensable gases. Ar-40 and Ar-36 both exhibit a predawn enhancement which indicates that they are condensable gases on the nightside and are re-released into the atmosphere at the sunrise terminator. Hydrogen probably exists in the lunar atmosphere in the molecular rather than atomic state, having been released from the surface in the molecular form. Total nighttime gas concentration of known species in the lunar atmosphere is 200,000 molecules/cu cm.

Hoffmann, J. H.↗
NASA NTRS1985

Hoop/column antenna deployment mechanism overview

The hoop/column antenna program is directed toward the development of a cost effective, large area, self deploying reflector antenna system. Large surface area antenna systems are required in future space missions involving improved land communications, Earth resources observation, and the study of intergalactic energy sources. The hoop/column antenna is a concept where a large antenna system can be packaged within the Space Transportation System (Shuttle) payload bay, launched into Earth orbit where it is released either for deployment as an Earth observation or communications antenna, or boosted into deep space as an intergalactic energy probe. Various mechanisms and support structures are described that are required to deploy the hoop, which is used to support the antenna reflective surface, and the column that is used to position the antenna feeds and the reflector. It also describes a proof-of-concept model (15 meters in diameter) that is currently being ground tested to determine the adequacy of the deployment mechanisms.

Allen, B. B.↗
NASA NTRS2000

Rapid Changes in Mercury's Sodium Exosphere

Sodium in the atmosphere of Mercury can be detected by sunlight scattered in the D1 and D2 resonance lines. Images of the sodium emission show that the sodium density changes from day to day and is often concentrated in regions at high or mid latitudes. Drew Potter (NASA/JSC) and Tom Morgan (SWRI) suggested that sputtering by magnetospheric particles was the origin of the sodium. A problem with this is that the magnetic field of Mercury is strong enough that it is believed to shield the surface from solar particles much of the time, although particle precipitation at the magnetospheric cusps could deposit particles to the surface at high latitudes. Ann Sprague (UA/LPL) noted that the "spots" of sodium emission tended to coincide with major geologic features, such as the Caloris Basin. She proposed that the sodium is released from sodiumrich surface rocks that are associated with these features; however, some spots have appeared where there are no obvious geologic features. Some of the difficulty in ascribing a source for the sodium arises from the effect of terrestrial atmospheric blurring of the image. It is hard to tell exactly where the sodium emission originates after the atmosphere has blurred the image. Potter, Killen (SWRI), and Morgan recently developed a technique for correcting sodium images for atmospheric blurring, using images made with a large-area image slicer. They applied this technique to a series of Mercury sodium observations made in November, 1997 at the McMath-Pierce Solar Telescope. Their technique for producing images from the spectroscopic data provides images of both the sodium emission and of the sunlight reflected from the surface.

Potter, Drew↗
NASA NTRS2014

Building the Fire Energetics and Emissions Research (FEER) Smoke Emissions Inventory Version 1.0

The Fire Energetics and Emissions Research (FEER) group's new coefficient of emission global gridded product at 1x1 resolution that directly relates fire readiative energy (FRE) to smoke aerosol release, FEERv1.0 Ce, made its public debut in August 2013. Since then, steps have been taken to generate corresponding maps and totals of total particulate matter (PM) emissions using different sources of FRE, and subsequently to simulate the resulting PM(sub 2.5) in the WRF-Chem 3.5 model using emission rates from FEERv1.0 as well as other standard biomass burning emission inventories. An flowchart of the FEER algorithm to calculate Ce is outlined here along with a display of the resulting emissions of total PM globally and also regionally. The modeling results from the WRF-Chem3.5 simulations are also shown.

particulate matter↗
NASA NTRS2020

NASA Advanced Composites Project

The recently-completed NASA Advanced Composites Project (ACP) successfully developed several new technologies aimed at reducing the timeline to design and certify composite aircraft structures. Advancements in the areas of manufacturing simulation, nondestructive inspection and advanced structural design and analysis methodologies were completed in late 2019 under the Advanced Composites Consortium (ACC) public/private partnership as well as NRA-funded university contracts. In the area of Structures, the ACC made significant improvements in rapid design tools for preliminary sizing of structure, along with developing detailed static and fatigue strength prediction methods and methods for modeling high energy impact events in composite structures. These new methodologies and toolsets were validated against a range of representative test data using a comprehensive verification and validation approach which has been published and is now used extensively on other programs. Specific new tool improvements supported by ACC include NASA’s CompDam code and Floating Node Method code. CompDam is now available from NASA as open source code. The team alsoworked on improved impact modeling using LS-Dyna™ and improved delamination modeling using Abaqus™. Rapid design tool improvements are available through Hypersizer. The ACC team released well over 50 publications documenting these method improvements, and the ACP recently received the prestigious NASA Group Achievement Award for their work.Typical Hat Stiffened Panel Test Article Used for Method Validation

ACC↗
NASA NTRS1971

What can nuclear energy do for society.

Nuclear fuel is a compact and abundant source of energy. Its cost per unit of energy is less than that of fossil fuel. Disadvantages of nuclear fuel are connected with the high cost of capital equipment required for releasing nuclear energy and the heavy weight of the necessary shielding. In the case of commercial electric power production and marine propulsion the advantages have outweighed the disadvantages. It is pointed out that nuclear commercial submarines have certain advantages compared to surface ships. Nuclear powerplants might make air-cushion vehicles for transoceanic ranges feasible. The problems and advantages of a nuclear aircraft are discussed together with nuclear propulsion for interplanetary space voyages.

Rom, F. E.↗
NASA NTRS1983

FeO and H-2O and the homogeneous accretion of the earth

Shock devolatilization recovery data for brunite (Mg(OH)2) shocked to 13 and 23 GPa are presented. These data combined with previous data for serpentine (Mg3Si2O5(OH)4) are used to constrain the minimum size terrestrial planet for which planetesimal infall will result in an impact generated water atmosphere. Assuming, in hydrous phyllosilicates, model calculations simulating the interaction of metallic iron with impact released free water on the surface of the accreting Earth were carried out. It is assumed that the reaction of water with iron in the presence of enstatite is the prime source of the terrestrial FeO component of silicates and oxides. Lower and upper bounds on the terrestrial FeO budget are based on mantle FeO content and possible incorporation of FeO in the outer core. We demonstrate that the iron water reaction would result in the absence of atmospheric/hydrospheric water, if homogeneous accretion is assumed.

Lange, M. A.↗
NASA NTRS1984

FeO and H2O and the homogeneous accretion of the earth

Shock devolatilization recovery data for brunite (Mg(OH)2) shocked to 13 and 23 GPa are presented. These data combined with previous data for serpentine (Mg3Si2O5(OH)4) are used to constrain the minimum size terrestrial planet for which planetesimal infall will result in an impact generated water atmosphere. Assuming, in hydrous phyllosilicates, model calculations simulating the interaction of metallic iron with impact released free water on the surface of the accreting earth were carried out. It is assumed that the reaction of water with iron in the presence of enstatite is the prime source of the terrestrial FeO component of silicates and oxides. Lower and upper bounds on the terrestrial FeO budget are based on mantle FeO content and possible incorporation of FeO in the outer core. We demonstrate that the iron water reaction would resuit in the absence of atmospheric/hydrospheric water, if homogeneous accretion is assumed.

Lange, M. A.↗
NASA NTRS1987

Release of juvenile water on Mars - Estimated amounts and timing associated with volcanism

The amount of water released on Mars in association with volcanism is estimated to equal a layer 46 meters deep over the entire planet. Most of this water was released in the first 2 billion years of Martian history. The estimate is based on mapping the volcanic materials and by inferring the volatile content of the lavas. Water from other sources, such as plutonic activity and cometary contributions, is not included in the estimate.

Greeley, Ronald↗
NASA NTRS1991

Diapirism and the origin of high TiO2 mare glasses

High TiO2 mare picritic glasses are derived from cumulate source regions that are only modestly endowed with ilmenite-enriched crystallization products. These sources are mobilized by the heat derived from the primitive interior and evolve into diapirs which rise adiabatically from depths in excess of 700 km. As these diapirs undergo pressure-release melting, they also stir in significant portions of the surrounding mantle.

Hess, Paul C.↗
NASA NTRS2008

CME-Producing Precursors to the 2006 December 13 X-Flare

We revisit one of the largest explosions observed during the Hinode era, the X4.3 class event of 2006 Dec 13. We gain insight into the main eruption through study of two sub-C-class precursor eruptions, occurring within 12 hours of and originating from the same (or nearby) neutral line as the X-flare. The precursors share some features in common with the main eruption, and their lower energy and consequent slower development renders interpretation of these features easier to decipher than in the rapidly explosive main eruption. In addition, because the weak precursors occurred in a magnetically strong region, magnetic connections indicated by soft X-ray loops are readily visible in these cases, while such connections can be much less apparent in weaker-region eruptions. Hinode/SOT magnetograms indicate that photospheric magnetic dynamic activity in the "magnetic core" is the likely ultimate source of the eruptions. All the eruptions, however, produce Coronal Mass Ejections (CMEs) that have wider spatial extent than the localized source region; this is a long-observed but puzzling phenomena, which can address directly here using the high-quality Hinode data. For the precursor eruptions, Hinode/XRT images show that the initial eruptions occur inside larger-scale magnetic structures that encompass the core. The exploding core field blows out this larger-scale structure, resulting in the CME having angular extent far exceeding that of the source-region core alone; this is the arch-arch-blowout scenario for CMEs of Moore & Sterling (2007). Similar processes occur in the main eruption, except that the much larger energy release in that eruption compared to the precursors results in much faster and larger-scale phenomena.

Sterling, Alphonse C.↗