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At least 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

LHC EFT WG note: SMEFT predictions, event reweighting, and simulation

This note provides a comprehensive overview of tools for predicting observables in the Standard Model effective field theory (SMEFT) at both tree level and one loop using event generators. We evaluate three primary methodologies–event reweighting, separate simulation of squared matrix elements, and full SMEFT process simulation–focusing on their statistical performance, computational efficiency, and potential biases. Each approach is assessed in terms of its accuracy, highlighting trade-offs between precision and resource demands. Practical insights into their applicability for high-energy physics analyses are offered, with particular attention to processes where SMEFT effects are significant. Additionally, we discuss the role of helicity in reweighting strategies and its impact on the quality of predictions. By comparing the methods across various LHC processes, this note provides guidance for selecting the most effective strategy for various SMEFT studies, ensuring robust predictions while optimizing computational resources.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2026

A total of 19 months of daily weather logging on the US east coast: the WFIP3 event log

The Third Wind Forecast Improvement Project (WFIP3) is a multi-institutional field campaign designed to advance the understanding and prediction of the offshore atmospheric boundary layer along the US east coast. Extending from February 2024 through August 2025, WFIP3 combines long-term coastal and offshore measurements with targeted modeling and forecasting efforts. This data paper presents the WFIP3 event log, a curated record of 578 d of meteorological phenomena and field observations that complements the campaign's extensive high-frequency datasets. The event log provides both manually documented daily weather discussions and automatically derived indicators of atmospheric processes – including low-level jets, wind ramps, extreme wind veer, and weak wind conditions – based on observations from scanning lidars deployed at three coastal and offshore sites. The dataset offers structured metadata, standardized time and site identifiers, and consistent terminology to facilitate its integration with WFIP3's observational and modeling data products. The log supports diverse applications, from model evaluation and forecast verification to the selection of case studies on offshore boundary-layer dynamics. The WFIP3 event log is publicly available through the US Department of Energy's Wind Data Hub, providing the research community with a transparent and enduring contextual reference for the interpretation and use of WFIP3 measurements.

17 WIND ENERGY↗
NASA NTRS2006

The STEREO Mission: A New Approach to Space Weather Research

With the launch of the twin STEREO spacecraft in July 2006, a new capability will exist for both real-time space weather predictions and for advances in space weather research. Whereas previous spacecraft monitors of the sun such as ACE and SOH0 have been essentially on the sun-Earth line, the STEREO spacecraft will be in 1 AU orbits around the sun on either side of Earth and will be viewing the solar activity from distinctly different vantage points. As seen from the sun, the two spacecraft will separate at a rate of 45 degrees per year, with Earth bisecting the angle. The instrument complement on the two spacecraft will consist of a package of optical instruments capable of imaging the sun in the visible and ultraviolet from essentially the surface to 1 AU and beyond, a radio burst receiver capable of tracking solar eruptive events from an altitude of 2-3 Rs to 1 AU, and a comprehensive set of fields and particles instruments capable of measuring in situ solar events such as interplanetary magnetic clouds. In addition to normal daily recorded data transmissions, each spacecraft is equipped with a real-time beacon that will provide 1 to 5 minute snapshots or averages of the data from the various instruments. This beacon data will be received by NOAA and NASA tracking stations and then relayed to the STEREO Science Center located at Goddard Space Flight Center in Maryland where the data will be processed and made available within a goal of 5 minutes of receipt on the ground. With STEREO's instrumentation and unique view geometry, we believe considerable improvement can be made in space weather prediction capability as well as improved understanding of the three dimensional structure of solar transient events.

Kaiser, michael L.↗
NASA NTRS2024

Ion Diffusive Transport Across the Separatrix Between the Low-Latitude Mantle and the Plasma Sheet By Kinetic Alfvén Waves: MMS Observation

To understand the entry of the cool low‐latitude mantle ions into the tail plasma sheet near the flanks under persistent interplanetary magnetic field B y , we evaluate the role of the cross‐field diffusive transport by kinetic Alfvén waves (KAWs) by investigating two events observed by multiscale (MMS) spacecraft. Around the separatrix between the open and closed field‐line regions, a two‐component mixing of hot plasma sheet ions of a few keV with cool mantle ions of a few hundred eV was observed, indicating transport across the separatrix. The waves observed between 0.01 and 10 Hz around the separatrix had characteristics consistent with those of KAWs. The consistency allowed us to estimate the wave vectors as a function of frequency by fitting KAW dispersion to the observations. Using the observed wave powers, plasma moments, and the estimated wave vectors, we computed the cross‐field diffusion rates associated with KAWs. The diffusion rates were found to be comparable to or larger than the Bohm diffusion rates during the intervals when the two‐component mixing was observed, indicating that the KAW diffusive transport can play a role in the entry of low‐latitude mantle ions into the plasma sheet.

Kinetic Alfvén waves↗
NASA NTRSDate not supplied

Investigation of the Alfven Wave Turbulence on the Dynamics of SEPs

Solar energetic particles (SEPs) are high-energy particles originating from the Sun that pose potential risks to space missions, especially those outside Earth's protective magnetosphere. Understanding their behavior within the heliosphere and Earth's magnetosphere is vital for the safety and functionality of space exploration. The study focuses on how the pitch angle scattering, the angle change between a particle's velocity and the magnetic field due to interactions with magnetic irregularities, impacts the decay phase of SEP events. By solving the focused transport equation, the study models the transport of SEPs along magnetic field lines, extending these lines up to 5 AU (Astronomical Units) to understand their behavior even beyond the typical proximity to the Sun. Incorporating the effects of pitch angle scattering at such vast distances is crucial for understanding the decay dynamics of a SEP event. This modeling of SEPs is integrated with simulations of other vital space phenomena: the solar wind, interplanetary magnetic field, and Alfven wave turbulence. This presentation covers the modeling approach used in this research and the role of pitch angle scattering at various heliocentric distances on the dynamics of the SEP events' decay phase.

solar energetic particles↗
NASA NTRS1988

Substorm variations in the magnitude of the magnetic field - AMPTE/CCE observations

Using energetic-particle data taken in the near-earth tail by the AMPTE/Charge Composition Explorer (CCE) satellite, 167 ion injection events, that were essentially dispersionless over a 25-285 keV energy range, were identified, and the variations in the total magnetic field strength over the course of these events were examined in order to determine the dependence of the magnetic field strength on dipole latitude. Results indicate that, during periods of substorm activity, the latitudinal position of the current sheet varied significantly within the 32-deg wedge centered on the dipole equator traversed by CCE. Results also suggest that, even in the near-earth magnetotail out to 8.8 R(E) (CCE apogee), the local field measurements are a better guide to the determination of satellite's position relative to the current shield during a substorm, than is the magnetic latitude.

Lopez, R. E.↗
NASA NTRS1980

Distribution functions of type III electrons observed in interplanetary space

Simultaneous energetic electron and solar radio observations from the ISEE-3 spacecraft of several solar type III radio bursts are analyzed and discussed. Two types of electron events are found: (1) normal flare associated electron events in the 20 to greater than 100 keV range, and (2) low energy, 2 to 10 keV, electron events which appear to be associated with individual type III bursts from low frequency type III storms. The arrival direction and frequency of the radio emission are identified and the temporal behavior of the in situ radio intensity and the electron intensity are compared. Calculations of the electron velocity distribution function parallel to the magnetic field are made, implying that for electron events above 20 keV, scattering in the pitch angle is significant in modifying this function.

Lin, R. P.↗
NASA NTRS1988

Time-dependent polar wind modeling

In the presence of a strong magnetic field (such as the geomagnetic field) the plasma tends to flow along the magnetic-field lines; therefore, in most ionospheric flow calculations the use of the gyrotropic approximation is justified. Here, it is shown that the gyrotropic 20-moment approximation is equivalent to the gyrotropic 16-moment approximation. Consideration is then given to return-current-generated polar wind transients. Ionospheric return currents generate significant downward heavy ion flows in the topside ionosphere with peak values well exceeding 10 to the 8th/sq cm sec. When the return current ceases, the polar ionosphere rapidly returns to its previous equilibrium state. During the recovery phase of the return-current event, an upward-propagating heavy-ion transient is formed, which is mainly characterized by a relatively short O(+) upwelling event. The H(+) escape flux remains a relatively constant (within 10-20 percent) during field-aligned-current events.

Gombosi, T. I.↗
NASA NTRS2019

A New Model of the Crustal Magnetic Field of Mars Using MGS and MAVEN

While devoid of an active magnetic dynamo field today, Mars possesses a remanent magnetic field that may reach several thousand nanoteslas locally. The exact origin and the events that have shaped the crustal magnetization remain largely enigmatic. Three magnetic field data sets from two spacecraft collected over 13 cumulative years have sampled the Martian magnetic field over a range of altitudes from 90 up to 6,000 km: (a) Mars Global Surveyor (MGS) magnetometer (1997–2006), (b) MGS Electron Reflectometer (1999–2006), and (c) Mars Atmosphere and Volatile EvolutioN (MAVEN) magnetometer (2014 to today). In this paper we combine these complementary data sets for the first time to build a new model of the Martian internal magnetic field. This new model improves upon previous ones in several aspects: comprehensive data coverage, refined data selection scheme, modified modeling scheme, discrete-to-continuous transformation of the model, and increased model resolution. The new model has a spatial resolution of ∼160 km at the surface, corresponding to spherical harmonic degree 134. It shows small scales and well-defined features, which can now be associated with geological signatures.

Magnetic↗
NASA NTRS1994

Observations of Pc5 micropulsation-related electric field oscillations in equatorial ionosphere

A 54.95-MHz coherent backscatter radar, an ionosonde and the magnetometer located at Trivandrum in India (8.5 deg N, 77 deg E, 0.5 deg N dip angle) recorded large-amplitude ionospheric fluctuations and magnetic field fluctuations associated with a Pc5 micropulsation event, which occurred during an intense magnetic storm on 24 March 1991 (A(sub p) = 161). Simultaneous 100-n T-level fluctuations are also observed in the H-component at Brorfelde, Denmark (55.6 deg N gm) and at Narsarsuaq, Greenland (70.6 deg N gm). Our study of the above observations shows that the E-W electric field fluctuations in the E- and F-regions and the magnetic field fluctuations at Thumba are dominated by a near-sinusoidal oscillation of 10 min during 1730-1900 IST (1200-1330 UT), the amplitude of the electric field oscillation in the equatorial electrojet (EEJ) is 0.1-0.25 mV/m and it increases with height, while it is about 1.0 mV/m in the F-region, the ground-level H-component oscillation can be accounted for by the ionospheric current oscillation generated by the observed electric field oscillation in the EEJ and the H-component oscillations at Trivandrum and Brofelde are in phase with each other. The observations are interpreted in terms of a compressional cavity mode resonance in the inner magnetosphere and the assoicated ionospheric electric field penetrating from high latitudes to the magnetic equator.

Reddy, C. A.↗
NASA NTRS1996

AMPTE/CCE and SCATHA simultaneous observations of magnetic signatures associated with a substorm onset

Magnetic field signatures associated with a substorm onset event are examined by making use of simultaneous observations from the Active Magnetosphere Particle Tracer Explorer (AMPTE)/Charge Composition Explorer (CCE) and Spacecraft Charging AT High Altitude (SCATHA). The observations of the two satellites are discussed in relation to their differences and the relative positions of the satellites. Despite the small separation between the satellites, AMPTE/CCE observed the start of irregular magnetic field fluctuations a few tens of seconds earlier than SCATHA, indicating that the CCE was within, or closer to, the onset region. It was found that the amplitude of the fluctuations was largest in the north-south component. The results indicate that the magnetic field fluctuations were excited locally and the coherence length was less than a multiple of Larmor radius of thermal protons. It is suggested that the tail current disruption is described as a system of chaotic filamentary electric currents which flow in various directions, but preferentially anti-parallel to the cross-tail current, and that ions play an important role in the triggering of the tail current disruption.

Ohtani, S.↗
NASA NTRS1995

Theoretical study of hole initiated impact ionization in bulk silicon and GaAs using a wave-vector-dependent numerical transition rate formulation within an ensemble Monte Carlo calculation

In this paper, calculations of the hole initiated interband impact ionization rate in bulk silicon and GaAs are presented based on an ensemble Monte Carlo simulation with the inclusion of a wave-vector-dependent numerical transition rate formulation. The ionization transition rate is determined for each of the three valence bands, heavy, light, and split-off, using Fermi's golden rule with a two-body, screened Coulomb interaction. The dielectric function used within the calculation is assumed to be wave-vector-dependent. Calculations of the field-dependent impact ionization rate as well as the quantum yield are presented. It is found from both the quantum yield results and examination of the hole distribution function that the effective threshold energy for hole initiated impact ionization is relatively soft, similar to that predicted for the corresponding electron initiated ionization events occur more frequently than either heavy or split-offf initiated ionization events in bulk silicon over the applied electric field strengths examined here, 250-500 kV/cm. Conversely,in GaAs, the vast majority of hole initated ionization events originate from holes within the split-off band.

Oguzman, Ismail H.↗
NASA NTRS2004

Correlation of Lightning Flash Rates with a Microburst Event

In 1986 the MIST (Microburst and Severe - Thunderstorm) field study took place over northern Alabama. It was noted that the time of day when a peak in microburst activity was observed usually took place around 2000 UTC. It was further confirmed through the examination of the various PAM (Portable Automated Mesonet) stations that this was also the time of day where temperatures would reach their peak. On the afternoon of 18 August 2002, as the temperature approached a daily high temperature of 32 C, the first radar indication of the HSV microburst-producing storm initiated at 2020 UTC.

Altino, Karen M.↗
NASA NTRS1992

Disconnection of open coronal magnetic structures

We have examined the Solar Maximum Mission coronagraph/polarimeter observations for evidence of magnetic disconnection of previously open magnetic structures and a number of likely examples have been found. Probable coronal disconnections typically appear as pinching off of helmet streamers followed by the release and outward acceleration of a large U or V-shaped structure. The observed sequence of events is consistent with reconnection across the heliospheric current sheet between previously open magnetic field regions, and the creation of a detached magnetic structure which is open to interplanetary space at both ends. Sunward of the reconnection point, coronal disconnection events would return previously open magnetic flux to the Sun as closed field arches. Here we (1) describe one clear disconnection event (1 June 1989); (2) examine the results of a limited survey of disconnection events; and (3) discuss the potential importance of coronal disconnections for maintaining flux in interplanetary space.

Mccomas, D. J.↗
NASA NTRS1986

Doppler lidar studies of atmospheric wind field dynamics

For the past 5 years the Wave Propagation Lab. has operated a pulsed CO2 Doppler lidar system to evaluate coherent laser radar technology and to investigate applications of the technique in atmospheric research. The capability of the system to provide measurements of atmospheric winds, backscatter, and water vapor has been extensively studied over this period. Because Doppler lidar can measure atmospheric wind structure in the clear air without degradation by terrain features, it offers a unique capability as a research tool for studies of many transient or local scale atmospheric events. This capability was demonstrated in recent field experiments near Boulder, Colo. and Midland, Tex., in which the lidar clearly depicted the wind field structure associated with several types of phenomena, including thunderstorm microbursts, valley drainage flow, and passage of a dryline front. To improve sensitivity during the periods of low aerosol backscatter, the system has recently been upgraded with new transmitter/receiver hardware. The upgraded system, which transmit 2 J per pulse of output energy at a rate of 50 Hz and incorporates computer control for automated operation, underwent calibration testing during the spring of 1986.

Hardesty, R. M.↗
NASA NTRS2022

File Specification for MERRA-2 Climate Statistics Products

The Modern Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) contains a wealth of information that can be used for weather and climate studies. By combining the assimilation of observations with a frozen version of the Goddard Earth Observing System (GEOS), a global analysis is produced at an hourly temporal resolution spanning from January 1980 through present (Gelaro et al., 2017). It can be difficult to parse through a multidecadal dataset such as MERRA-2 to evaluate the interannual variability of weather that occurs on a daily timescale, let alone determine the occurrence of an extreme weather event. Furthermore, it was recognized that standard metrics were needed to evaluate climate change among climate models and international research efforts. As a result of these concerns, the Expert Team on Climate Change Detection and Indices (ETCCDI) developed a set of indices that represent the frequency and intensity of extreme weather events using a daily time series of 2-m air temperature (T2m) and precipitation (Alexander et al., 2016). These indices were used as a basis to comprise a list of fields that represent daily extreme temperature and precipitation events, heatwaves, multi-day precipitation, as well monthly percentile statistics from the MERRA-2 dataset. Also included in this data product is a climatological long term mean and standard deviation representing the interannual variability on a monthly timescale.

MERRA-2↗