Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “event study”

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.

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

At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Seismo-Acoustic Wave Simulation for Earthquake-Generated Infrasound

It is well known that underground explosions or earthquakes can generate infrasound in the atmosphere. Seismoacoustic coupling between the ground motions and atmosphere is a key mechanism for infrasound generation. Epicentral infrasound which is direct response to epicentral ground motions are extensively studied for event detection and discrimination. Diffracted infrasound generated from Rayleigh waves are often observed and reported. Recent studies suggested the surface topography is also important for infrasound generation, and mountains or topographic peaks can act as effective secondary infrasound sources. In this study, we perform full 3-D seismoacoustic simulations to understand a coupled seismic and acoustic wave generation by an earthquake and energy partitioning across the solid Earthocean-atmosphere system. By including the effects of realistic topography, bathymetry, and earthquake focal mechanism, we provide quantitative information about seismoacoustic wavefields and secondary infrasound sources across the solid-water, solid-air, and water-air interfaces. Acoustic wave transmission across water-air interface is also investigated by using synthetic waveforms. Our study suggests that shallow seas near the coastline or over elevated seafloors can transmit significant amount of energy from acoustic waves in water and can be effective secondary infrasound sources.

58 GEOSCIENCES↗
NASA NTRS1992

Thermospheric composition changes seen during a geomagnetic storm

The largest magnitude winds observed using the instruments on board the Dynamics Explorer 2 (DE-2) satellite were measured during the large geomagnetic storm that occurred on November 24, 1982. Neutral temperatures exceeded 2000 K during this storm, and these high temperatures, combined with the very large observed winds and the very full instrumental coverage available in both hemispheres, make it a unique event to study. This paper presents results obtained using these DE-2 data and a time dependent simulation of the event made using the NCAR Thermosphere/Ionosphere General Circulation Model (NCAR-TIGCM). In general, the agreement between model calculations and the data is very good, implying that most of the important physical processes controlling the energetics and dynamics of the thermosphere are reasonably well represented in the model. The modeled summer hemisphere changes in the mass mixing ratio of N2 (Psi(N2)) are in very good agreement with the averaged data in both hemispheres. This paper describes model-experiment comparisons for the November 24, 1982 geomagnetic storm changes.

Burns, A. G.↗
NASA NTRS1983

Survey of He(+)/He(2+) abundance ratios in energetic particle events

The helium charge distribution in the energy range 0.4 to 0.62 MeV/nucleon in energetic particle events was studied. An average He+/He2+ ratio of 0.12 + or - 0.04 with ratios exceeding 0.3 for 41 out of 420 days events richest in He+ and no significant differences of the proton energy spectra, and the abundance of helium relative to protons and heavy ions for He+ rich events (He+/He2+ 0.3) and for events with He+/He2+ 0.3, respectively. It is also found that He+ rich events are predominantly low in energetic particle intensity.

Hovestadt, D.↗
NASA NTRS1991

Prompt arrival of solar energetic particles from far eastern events - The role of large-scale interplanetary magnetic field structure

Intensity-time profiles of solar energetic particle enhancements generally show an asymmetry with respect to the heliolongitude of the associated solar event. Particles arrive promptly from events to the west of an observer because of good magnetic connection, whereas particle enhancements from poorly connected eastern source regions usually show much slower onsets. However, some 15 percent of eastern events do show prompt onsets. Two prompt particle enhancements associated with eastern solar events are studied using data from the Goddard Space Flight Center instruments on the ISEE 3 and IMP 8 spacecraft. In both events the prompt particle onset was observed when the spacecraft were in a postshock plasma region, apparently within a magnetic bottle. It is suggested that the magnetic bottle extended back to the sun and served as a channel for fast particle propagation to the spacecraft. Particles accelerated at an expanding coronal shock initiated by the eastern event could be injected onto field lines in the foot of the bottle.

Richardson, I. G.↗
NASA NTRS2021

Seventeen Tidal Disruption Events from the First Half of ZTF Survey Observations: Entering a New Era of Population Studies

While tidal disruption events(TDEs) have long been heralded as laboratories for the study of quiescent blackholes, the small number of known TDEs and uncertainties in their emission mechanism have hindered progress toward this promise. Here we present 17 new TDEs that have been detected recently by the Zwicky Transient Facility along with Swift UV and X-ray follow-up observations. Our homogeneous analysis of the optical/UV light curves, including 22 previously known TDEs from the literature, reveals a clean separation of light-curve properties with spectroscopic class. The TDEs with Bowen fluorescence features in their optical spectra have smaller blackbody radii, lower optical luminosities, and higher disruption rates compared to the rest of the sample. The small subset of TDEs that show only helium emission lines in their spectra have the longest rise times, the highest luminosities, and the lowest rates. A high detection rate of Bowen lines in TDEs with small photometric radii could be explained by the high density that is required for this fluorescence mechanism. The stellar debris can provide a source for this dense material. Diffusion of photons through this debris may explain why the rise and fade timescale of the TDEs in our sample are not correlated. We also report, for the first time, the detection of soft X-ray flares from a TDE on∼day timescales. Based on the fact that the X-ray flares peak at a luminosity similar to the optical/UV blackbody luminosity, we attribute them to brief glimpses through a reprocessing layer that otherwise obscures the inner accretion flow.

Sjoert van Velzen↗
NASA NTRS2011

An Experimental Study of the Rainfall Variability Within TRMM/GPM Precipitation Radar and Microwave Sensor Instantaneous Field of View During MC3E

Dual tipping bucket gauges were operated at 16 sites in support of ground based precipitation measurements during Mid-latitude Continental Convective Clouds Experiment (MC3E). The experiment is conducted in North Central Oklahoma from April 22 through June 6, 2011. The gauge sites were distributed around Atmospheric Radiation Measurement (ARM) Climate Research facility where the minimum and maximum separation distances ranged from 1 to 12 km. This study investigates the rainfall variability by employing the stretched exponential function. It will focus on the quantitative assessment of the partial beam of the experiment area in both convective and stratiform rain. The parameters of the exponential function will also be determined for various events. This study is unique for two reasons. First is the existing gauge setup and the second is the highly convective nature of the events with rain rates well above 100 mm/h for 20 minutes. We will compare the findings with previous studies.

Tokay, Ali↗
NASA NTRS1978

Bidirectional anisotropies in solar cosmic ray events - Evidence for magnetic bottles

During the period 1967-1973 data were obtained from five satellites in order to investigate bidirectional anisotropies in low-energy solar protons and to study electron events. Detailed consideration is given to the characteristics of two observed solar electron events. It is particularly noted that (1) the mean duration of bidirectional anisotropy is about 9 hours, (2) for most events the bidirectional anisotropy occurs at the minimum of the associated Forbush decrease, (3) the existence of bidirectional anisotropy in subrelativistic electrons associated with an interplanetary shock is not expected as anisotropies in impulsive solar electron events usually decay quickly within a time of not more than an hour at 1 AU, and (4) simultaneous observations show a significant difference in the nature of the angular distributions first between electrons and protons and second between different proton energies. The formation of bidirectional anisotropy by propagation and by energy change is also discussed.

Palmer, I. D.↗
NASA NTRS2011

An Experimental Study of the Rainfall Variability Within TRMM/GPM Precipitation Radar and Microwave Sensor Instantaneous Field of View During MC3E

Dual tipping bucket gauges were operated at 16 sites in support of ground based precipitation measurements during Mid-latitude Continental Convective Clouds Experiment (MC3E). The experiment is conducted in North Central Oklahoma from April 22 through June 6, 2011. The gauge sites were distributed around Atmospheric Radiation Measurement (ARM) Climate Research facility where the minimum and maximum separation distances ranged from 1 to 12 km. This study investigates the rainfall variability by employing the stretched exponential function. It will focus on the quantitative assessment of the partial beam of the experiment area in both convective and stratiform rain. The parameters of the exponential function will also be determined for various events. This study is unique for two reasons. First is the existing gauge setup and the second is the highly convective nature of the events with rain rates well above 100 mm h-1 for 20 minutes. We will compare the findings with previous studies.

Tokay, Ali↗
NASA NTRS1988

An ISEE-1/2 spacecraft study of an unusual flux transfer event

Using the ISEE-1/2 spacecraft, an unusual FTE was studied. The perturbation in the direction normal to the magnetopause reached a maximum size of 64 nT, exceeding the field amplitude in the adjacent magnetosphere. The observation was made at 1500 Local Time in the Southern Hemisphere (10 deg below the magnetic equator). From two point observations, it was found that the structure has a scale length of 2R(E) in the north-south direction in boundary normal coordinates. The velocity of the structure in that direction was about 50 km/sec. The dimension and the velocity in the east-west direction could not be established. The FTE signature recurred after about 9 minutes.

Zhu, X. M.↗
DOE OSTI2024

Investigating the effects of cooperative transmission expansion planning on grid performance during heat waves with varying spatial scales

There is growing recognition of the advantages of interregional transmission capacity to decarbonize electricity grids. A less explored benefit is potential performance improvements during extreme weather events. This study examines the impacts of cooperative transmission expansion planning using an advanced modeling chain to simulate power grid operations of the United States Western Interconnection in 2019 and 2059 under different levels of collaboration between transmission planning regions. Two historical heat waves in 2019 with varying geographical coverage are replayed under future climate change in 2059 to assess the transmission cooperation benefits during grid stress. The results show that cooperative transmission planning yields the best outcomes in terms of reducing wholesale electricity prices and minimizing energy outages both for the whole interconnection and individual transmission planning regions. Compared to individual planning, cooperative planning reduces wholesale electricity prices by 64.3 % and interconnection-wide total costs (transmission investments + grid operations) by 34.6 % in 2059. It also helps decrease greenhouse gas emissions by increasing renewable energy utilization. However, the benefits of cooperation diminish during the widespread heat wave when all regions face extreme electricity demand due to higher space cooling needs. Despite this, cooperative transmission planning remains advantageous, particularly for California Independent System Operator with significant diurnal solar generation capacity. This study suggests that cooperation in transmission planning is crucial for reducing costs and increasing reliability both during normal periods and extreme weather events. It highlights the importance of optimizing the strategic investments to mitigate challenges posed by wider-scale extreme weather events of the future.

24 POWER TRANSMISSION AND DISTRIBUTION↗
NASA NTRS1983

Mass composition of substorm-related energetic ion dispersion events

The mass dependent characteristics in two ion dispersion events is studied using data obtained by an ion mass spectrometer flown onboard the SCATHA (P78-2) spacecraft. It is found that the dispersion events are associated with substorm activity and that the dispersing ions originated in the dusk-midnight sector near the time of substorm onset. The question of the source of the dispersing plasma is examined since the mass spectrometer can discriminate between protons and oxygen. It is shown that a local injection of ionosphere plasma near the time of substorm onset can explain some of the signatures in the energetic ion spectra for different masses.

Strangeway, R. J.↗
NASA NTRS2008

Global Circulation and Impact of Plasmaspheric Plumes

We report results from the global circulation model of Lyon, Fedder, and Mobarry with an embedded model of the inner magnetosphere including the plasmasphere. The combination is used to initiate large numbers of representative protons on the geosynchronous orbit L shell, to assign particle weightings, to track their: subsequent trajectories in the 3D fields. This permits us to study the global circulation of plasmaspheric plumes and to compare these with Polar observations from the dayside magnetopause region . A range of events is studied from an isolated period of SBz in the solar wind,to a large storm sequence. We consider effects on circulating plasma reaching the dayside reconnection X-line, the population of the plasma sheet with ionospheric protons and the generation of ring current pressure from this source, compared with solar wind, polar wind, and auroral wind sources. We find that the transient plasmaspheric plume source is large in terms of total fluence, but of modest proportions in terms of contribution to the ring current. Implications of this and other results for improved space weather modeling and prediction will be discussed.

Moore, Thomas E.↗
DOE OSTI2026

Event Reconstruction for Water-based Liquid Scintillator Detectors

Water Cherenkov and liquid scintillator detectors represent two complementary approaches in neutrino physics. Water Cherenkov detectors provide particle track direction and particle identification (PID) through Cherenkov ring topology, while liquid scintillator detectors offer higher light yield and lower energy thresholds. Water-based liquid scintillator (WbLS) is designed to combine the advantages of both technologies. However, the simultaneous detection of Cherenkov and scintillation light by photosensors introduces significant challenges for event reconstruction. This poster presents event reconstruction studies for WbLS detectors. A likelihood-based reconstruction framework, fiTQun, has been successfully used in Super-Kamiokande to reconstruct water Cherenkov events in cylindrical detectors. We extend and improve this framework to demonstrate event reconstruction in WbLS detectors, enabling the concurrent reconstruction of particle energy, PID, vertex, and direction. The results demonstrate competitive performance in energy resolution, PID separation, and vertex and direction reconstruction, highlighting the strong potential of WbLS for next-generation neutrino experiments.

Xie, Zhenxiong [Minnesota U.] (ORCID:0009000301442↗
NASA NTRS1977

Observations of large transient magnetospheric electric fields

Transient electric field events were studied by means of the long double-probe instrumentation carried by the Imp 6 satellite, and nine clearly defined exceptionally large amplitude events are described. The events were observed in the midnight sector at geocentric distances of 3.5 to 5.5 earth radii at middle latitudes within a magnetic L shell range of 4.8 to 7.5; the duration is from one to several minutes with peak power spectra amplitudes occurring at a frequency of about 0.3 Hz. The events occur under magnetically disturbed conditions and are often associated with negative dH/dt excursions. The magnetospheric motions calculated for these electric fields indicate a quasi-stochastical diffusive process rather than the general inward magnetospheric collapsing motion expected during the expansive phases of auroral substorm activity. It is likely that the transient electric fields are responsible for the impulsive acceleration and injection of plasma to populate the outer radiation belt.

Aggson, T. L.↗
NASA NTRS1981

Soil moisture variation patterns observed in Hand County, South Dakota

Soil moisture data were taken during 1976 (April, June, October), 1977 (April, May, June), and 1978 (May, June, July) Hand County, South Dakota as part of the ground truth used in NASA's aircraft experiments to study the use of microwave radiometers for the remote sensing of soil moisture. The spatial variability observed on the ground during each of the sampling events was studied. The data reported are the mean gravimetric soil moisture contained in three surface horizon depths: 0 to 2.5, 0 to 5 and 0 to 10 cm. The overall moisture levels ranged from extremely dry conditions in June 1976 to very wet in May 1978, with a relatively even distribution of values within that range. It is indicated that well drained sites have to be partitioned from imperfectly drained areas when attempting to characterize the general moisture profile throughout an area of varying soil and cover type conditions. It is also found that the variability in moisture content is greatest in the 0 to 2.5 cm measurements and decreases as the measurements are integrated over a greater depth. It is also determined that the sampling intensity of 10 measurements per km is adequate to estimate the mean moisture with an uncertainty of + or - 3 percent under average moisture conditions in areas of moderate to good drainage.

Jones, E. B.↗
DOE OSTI2025

Remote Sensing Improves Multi‐Hazard Flooding and Extreme Heat Detection by Fivefold Over Current Estimates

The co‐occurrence of multiple hazards is of growing concern globally as the frequency and magnitude of extreme climate events increases. Despite studies examining the spatial distribution of such events, there has been little work in examining if all relevant life threatening and damaging hazards are captured in existing hazard databases and by common hazard metrics. For example, local/regional flash flooding events are seldom captured by optical satellite instruments and are subsequently excluded from global hazard databases. Similarly, the heat hazard definitions most frequently used in multi‐hazard studies inherently fail to capture events that are life‐threatening but climatologically within an expected range. Our goal is to determine the potential for increasing multi‐hazard event detection capabilities by inferring additional hazard footprints from widely accessible satellite data. We use daily precipitation and temperature satellite data to develop an open‐source framework that infers additional hazard footprints that are not included in traditional methods. With the state of Texas as our study area, we detected 2.5 times as many flood hazards, equivalent to $320 million in property and crop damages. Furthermore, our expanded heat hazard definition increases the impacted area by 56.6%, equivalent to 91.5 million km 2 over an 18 year period. Increasing hazard detection capabilities and expanding existing definitions of hazards using daily satellite data increases the temporal and spatial resolutions at which multi‐hazard events are detected. Having more complete data sets of all relevant hazard extents improves our ability to track global trends and more accurately determine the magnitude of hazard exposure inequities.

equity↗
DOE OSTI2023

Beryllium Isotopes in Rainfall for Stratospheric-Tropospheric Exchange Dynamics Experiment (BIRDIE) (Field Campaign Report)

The Beryllium Isotopes in Rainfall for Stratospheric-Tropospheric Exchange Dynamics Experiment or BIRDIE was a precipitation collection campaign designed to measure cosmogenic isotopes of beryllium in rainfall and other forms of precipitation across the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) user facility’s Southern Great Plains (SGP) atmospheric observatory. Precipitation samples were collected over three weeks (May 21-June 10, 2022) at 11 SGP sites across a 120-km 2 domain in northern and central Oklahoma. The field campaign targeted summertime convection rain events. We aimed to capture any spatial and/or temporal variability in the concentrations of beryllium-10 (10Be) and beryllium-7 (7Be) across the ARM SGP site during these rainfall events. The ratio of 10Be to 7Be (10/7Be) has been shown to be a powerful tracer for transport processes in the stratosphere-troposphere exchange (STE) system (e.g., Koch and Rind 1998). Any observed variability is analyzed to see if it could be linked to STE processes, including overshooting of deep convection clouds that penetrate the lower stratosphere. Six wet weather system events were collected within our three-week span. Five out of six of these rainfall events are classified as moderately to strongly convective. Those events are studied in more detail. The five systems also follow each other over a short period of 11 days. In our rainfall samples we observed spatial and event variability in the concentrations of beryllium-10 and -7 that resulted in variability of 10/7Be ratios. Each weather event appeared to exhibit a unique 10/7Be pattern across the domain that was not directly linked to storm total precipitation amount. To better understand the causes for this spatial variability, cloud characteristics in the domain were looked at to assess cloud type, cloud height, and depth information. We also ran Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model back trajectories to identify possible air mass and moisture origins across our events. Detailed analysis is ongoing. The purpose of this technical report is to provide background on using cosmogenic isotopes as atmospheric tracers, describe the experimental design, and present the beryllium concentration and ratio data. Lastly, we note that BIRDIE coincided with two other deep convection field campaigns in the area: The National Aeronautics and Space Administration (NASA)’s Dynamics and Chemistry of the Summer Stratosphere (DCOTSS) experiment (https://dcotss.org/) centered in Salina, Kansas, and the Targeted Observation by Radars and (uncrewed aerial systems) UAS of Supercells (TORUS) experiment (https://catalog.eol.ucar.edu/torus_2022) across the U.S. Central Plains. Additionally, a Lawrence Livermore National Laboratory ( LLNL) team at DCOTSS attempted to measure 10Be/7Be ratios on aerosols collected in situ in the lower and mid-stratosphere over Kansas using high-altitude balloons. Precipitation samples were also collected on the ground in Salina, Kansas.

54 ENVIRONMENTAL SCIENCES↗