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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Radial transport of radiation belt electrons in kinetic field-line resonances

A representative case study from the Van Allen Probes during a geomagnetic storm recovery phase reveals enhanced electron fluxes at intermediate pitch angles over energies from ~100 keV to 5 MeV coincident with broadband low-frequency electromagnetic waves. The statistical properties of these waves are used to build a model for radial diffusion via drift-bounce resonances in kinetic Alfvén eigenmodes/kinetic field-line resonances. Estimated diffusion coefficients indicate timescales for radial transport on the order of hours in storm time events at energies from <100 keV to MeVs over equatorial pitch angles from the edge of the loss cone to nearly perpendicular to the geomagnetic field. In conclusion, the correlation of kinetic resonances with electron depletions and enhancements during storm main phase and recovery, and the rapid diffusion these waves drive, suggests that they may modulate the outer radiation belt.

58 GEOSCIENCES↗
DOE OSTI2015

The global context of the 14 November 2012 storm event

From 2 to 5 UT on 14 November 2012, the Van Allen Probes observed repeated particle flux dropouts during the main phase of a geomagnetic storm as the satellites traversed the post-midnight to dawnside inner magnetosphere. Each flux dropout corresponded to an abrupt change in the magnetic topology, i.e., from a more dipolar configuration to a configuration with magnetic field lines stretched in the dawn-dusk direction. Geosynchronous GOES spacecraft located in the dusk and near-midnight sectors and the LANL constellation with wide local time coverage also observed repeated flux dropouts and stretched field lines with similar occurrence patterns to those of the Van Allen Probe events. THEMIS recorded multiple transient abrupt expansions of the evening-side magnetopause ~20–30 min prior to the sequential Van Allen Probes observations. Ground-based magnetograms and all sky images demonstrate repeatable features in conjunction with the dropouts. We combine the various in-situ and ground-based measurements to define and understand the global spatiotemporal features associated with the dropouts observed by the Van Allen Probes. We discuss various proposed hypotheses for the mechanism that plausibly caused this storm-time dropout event as well as formulate a new hypothesis that explains the combined in-situ and ground-based observations: the earthward motion of magnetic flux ropes containing lobe plasmas that form along an extended magnetotail reconnection line in the near-Earth plasma sheet.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1972

Storm-associated Pc 5 micropulsation events observed at the synchronous equatorial orbit.

Quasi-sinusoidal magnetic-field (micropulsations) are regularly observed at ATS 1 during geomagnetic storms. The wave events typically occur during the main phase and tend to be confined to the afternoon sector. All observed events have been closely correlated with magnetospheric substorm activity. Power spectral analysis shows that the observed oscillations are composed of harmonically related components. Twenty-six wave events were observed in 1967; the analysis of three typical Pc 5 events is presented here. The observations are compared with the predictions of theory for a hot inhomogeneous plasma. It is suggested that the observed micropulsations can be understood as the occurrence of either an Alfven wave instability, or a drift instability, of the enhanced storm-time ring current.

Barfield, J. N.↗
NASA NTRS1989

Access of energetic particles to storm time ring current through enhanced radial 'diffusion'

It is proposed that the transport of particles with energy of at least approximately 40 keV into the geomagnetic storm time ring current can result from enhanced stochastic radial transport driven by fluctuating electric fields during a storm's main phase. The effects of such electric fields are estimated by applying radial diffusion theory, assuming a preexisting trapped-particle population as the initial condition. The feasibility of explaining observed flux increases of particles of at least approximately 40 keV at no more than approximately 4 earth radii by enhanced radial 'diffusion' is then demonstrated. It is estimated that the at least approximately 40-keV portion of the storm time ring current at approximately 3 earth radii consists of about 50 percent preexisting and about 50 percent new particles. The formation of the storm time ring current is found to be perhaps explainable via a combination of direct radial transport at energies no greater than approximately 40 keV and 'diffusive' radial transport at higher energies.

Lyons, L. R.↗
NASA NTRS2021

Dynamics of the Terrestrial Radiation Belts: a Review of Recent Results During the VarSITI (Variability of the Sun and Its Terrestrial Impact) Era, 2014–2018

The Earth’s magnetosphere is region that is carved out by the solar wind as it flows past and interacts with the terrestrial magnetic field. The inner magnetosphere is the region that contains the plasmasphere, ring current, and the radiation belts all co-located within about 6.6 Re, nominally taken to be bounding this region. This region is highly dynamic and is home to a variety of plasma waves and particle populations ranging in energy from a few eV to relativistic and ultra-relativistic electrons and ions. The interplanetary magnetic field (IMF) embedded in the solar wind via the process of magnetic reconnection at the sub-solar point sets up plasma convection and creates the magnetotail. Magnetic reconnection also occurs in the tail and is responsible for explosive phenomena known as substorms. Substorms inject low-energy particles into the inner magnetosphere and help generate and sustain plasma waves. Transients in the solar wind such as coronal mass ejections (CMEs), co-rotating interaction regions (CIRs), and interplanetary shocks compress the magnetosphere resulting in geomagnetic storms, energization, and loss of energetic electrons in the outer radiation belt and enhance the ring current, thereby driving the geomagnetic dynamics. The Specification and Prediction of the Coupled Inner-Magnetospheric Environment (SPeCIMEN) is one of the four elements of VarSITI (Variability of the Sun and Its Terrestrial Impact) program which seeks to quantitatively predict and specify the inner magnetospheric environment based on Sun/solar wind driving inputs. During the past 4 years, the SPeCIMEN project has brought together scientists and researchers from across the world and facilitated their efforts to achieve the project goal. This review provides an overview of some of the significant scientific advances in understanding the dynamical processes and their interconnectedness during the VarSITI era. Major space missions, with instrument suites providing in situ measurements, ground-based programs, progress in theory, and modeling are briefly discussed. Open outstanding questions and future directions of inner magnetospheric research are explored.

Shrikanth Kanekal↗
NASA NTRS1972

Variations of atmospheric density near 400 km with magnetic activity during the storm period of 28 September to 2 October 1969

Neutral density data were obtained near 400 km (1600 LT) from a microphone density gage on OGO-6 from 0 to 40 deg N geomagnetic latitude for 25 September through 3 October 1969. Several geomagnetic storms occurred during this period. Least squares fits were made to data points on density scatter diagrams. An equation representing the least squares fit was computed for each delay time. The equation of best fit (and the corresponding time delay between the density and the magnetic index which resulted in this best fit) was found by choosing the equation that gave the minimum standard error. The implications of the time differences associated with the best fits at various latitudes and longitudes are discussed with regard to the time delays involved in geomagnetic heating of the neutral upper atmosphere.

Anderson, A. D.↗
NASA NTRS1982

Vertical density and temperature structure over northern Europe

Vertical profiles of upper-atmosphere temperature and density over northern Europe constructed from data obtained in November and December 1980, as part of the Energy Budget Campaign, are presented and discussed. Temperature sondes, passive spheres, accelerometers, mass and IR spectrometers, and density gauges were rocket launched from ESRANGE, Sweden and Andoya, Norway; the data are combined with ground measurements to construct 20-120-km-altitude profiles for night periods of severe, moderate, and minimal geomagnetic storm activity. The profiles are compared with each other and with the 1976 U.S. Standard Atmosphere (USSA). In the temperature profiles, increased geomagnetic activity is associated with lower temperatures and flattened profiles in the stratopause region, and higher temperatures in the 70-90-km range. The density profiles show a variation of less than about 15 percent, except for a 25-percent range for the moderate-geomagnetic-activity period. The inferred wavelengths and periods are those expected for internal gravity waves at this altitude, and the divergence from USSA is accounted for by season and latitude dependence.

Philbrick, C. R.↗
NASA NTRS2021

A Comparison of the CIR- and CME-Induced Geomagnetic Activity Effects on Mesosphere and Lower Thermospheric Temperature

Neutral temperature responses in the mesosphere and lower thermosphere (MLT) to severe geomagnetic storms induced by coronal mass ejections (CMEs) are of growing interest to the space science research community. Recently, it was found that geomagnetic activities produced by the corotating interaction regions (CIRs) caused comparable effects on the Earth's upper atmosphere. In this work, we carried out a comparative study of the temperature responses in the MLT region to these two types of geomagnetic activities, using the temperature measured by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instruments onboard the Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics (TIMED) satellite. Our results demonstrate that CIR-induced geomagnetic activity produced temperature variations in the MLT region and that this effect can penetrate downward to ∼100 km at high latitudes in both hemispheres. Temperature enhancements penetrated deeper during CME-induced geomagnetic activities, but the heating effects lasted longer during CIR-induced geomagnetic activities. There is a hemispherical asymmetry in the geomagnetical activity induced temperature changes in the MLT region. The temperature enhancements are stronger in the southern hemisphere than in the northern hemisphere during CME events.

geomagnetic activity↗
NASA NTRS2007

Empirical Storm-Time Correction to the International Reference Ionosphere Model E-Region Electron and Ion Density Parameterizations Using Observations from TIMED/SABER

The response of the ionospheric E-region to solar-geomagnetic storms can be characterized using observations of infrared 4.3 micrometers emission. In particular, we utilize nighttime TIMED/SABER measurements of broadband 4.3 micrometers limb emission and derive a new data product, the NO+(v) volume emission rate, which is our primary observation-based quantity for developing an empirical storm-time correction the IRI E-region electron density. In this paper we describe our E-region proxy and outline our strategy for developing the empirical storm model. In our initial studies, we analyzed a six day storm period during the Halloween 2003 event. The results of this analysis are promising and suggest that the ap-index is a viable candidate to use as a magnetic driver for our model.

Mertens, Christoper J.↗
DOE OSTI2024

Solar system storms in the lab: creating a scaled interplanetary coronal mass ejection

As an active star, the Sun frequently ejects large systems of magnetized plasma called Interplanetary Coronal Mass Ejections (ICMEs). When these ICMEs reach Earth, they cause geomagnetic storms, and, depending on their intensity, can wreak havoc on modern society [3]. In this project, we designed, executed, and diagnosed a proof-of-principle experiment aimed at studying ICMEs in a laboratory setting.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1978

Ring current electron trajectories associated with VLF emissions

The reported investigation had the objective to explain features of the ring current electron enhancements which are associated with the simultaneously observed VLF emissions during geomagnetic storms and substorms. Two examples of the electron intensity enhancements observed by Explorer 45 are presented, and the calculations of the electron trajectories injected from the geomagnetic tail into the nightside of the plasmasphere are discussed. These calculations are performed by modifying the computer program developed by Ejiri (1978) to explain the so-called nose events of the ring current protons. The presented calculation demonstrates the soundness of the models of the convective electric field and the static magnetic field.

Maeda, K.↗
NASA NTRSDate not supplied

The Ring Current ENA Instrument on the NASA STORIE Mission

NASA has recently selected the Storm Time O+ Ring current Imaging Evolution (STORIE) mission to study the evolution of Earth’s ring current and the role of composition and dynamics during geomagnetic storms. STORIE addresses this inner magnetospheric science through the use of a Ring current Energetic Neutral Atom (RENA) instrument hosted on the International Space Station (ISS). This novel vantage point for ENA imaging has a number of scientific and implementation advantages. RENA is a high sensitivity remote sensing ENA imager and composition instrument with a field of view of 90 x 2 degrees, and an angular resolution of 2 x 2 degrees. The instrument aperture points zenith and its long dimension is oriented perpendicular to the ISS ram direction. As a result, RENA acts as a “push broom” imager building up a complete sky scan of the ring current in a single 90-minute ISS orbit. The instrument employs electrostatic optics along with a foil-MCP TOF x PHA x Delay-Line position measurement technique to resolve H and O energy spectra in the energy range 10-500 KeV for each look direction. Furthermore, it employs triple+ time and position coincidence to effectively reduce background noise from geocoronal and black sky UV as well as penetrating radiation. The abundant mass, power, and telemetry, resources of the ISS allow for large instrument aperture, very high sensitivity, complex data product and simplified operations, altogether contributing towards a high signal to noise (S/N) measurement.

Space Science↗
NASA NTRS2006

The Living With a Star Geospace Program

NASA's Living With a Star program addresses research problems with societal impact. As specified by its mission definition team, the Geospace component of the program addresses two regions which pose the greatest hazards: the Earth's radiation belts and the mid-latitude ionosphere. Two Radiation Belt Storm Probe spacecraft with identical energetic particle, plasma wave, and magnetic field instrumentation will make the observations needed to distinguish spatial from temporal effects and identify the mechanisms governing particle energization, transport, and loss. Two Ionosphere- Thermosphere Storm Probes on inclined low-altitude and midlatitude orbits will make the observations needed to distinguish between special and temporal effects, characterize the response to varying solar EUV radiation and geomagnetic storms, and identify the mechanisms generating mid-latitude ionospheric irregularities. An imager on a mission of opportunity will provide the observations needed to place these in situ measurements in context.

Sibeck, D. G.↗
NASA NTRS1976

Storm-associated variations of equatorially mirroring ring current protons, 1-800 keV, at constant first adiabatic invariant

Explorer 45 observations of ring current protons mirroring near the equator, 1-800 keV, are presented at constant first adiabatic invariant mu throughout the period of the December 17, 1971, geomagnetic storm. The parameter mu is obtained from simultaneous magnetic field and particle observations. Particle deceleration in response to the storm time magnetic field decrease causes ring current measurements viewed at constant energy to underestimate the storm time increase in proton intensities at energies not exceeding 200 keV. This adiabatic deceleration also accounts for the large flux decreases observed at energies above 200 keV during the storm, in contradiction with previous results (Soraas and Davis, 1968) obtained using a model for the storm time magnetic field.

Lyons, L. R.↗
NASA NTRS1974

Environmental design criteria

Wind velocities at 140-200 km altitude were observed by a Low-G Accelerometer Calibration System (LOGACS) flown on an Agena satellite during a geomagnetic storm. An interesting wind reversal observed by the satellite at auroral latitudes is satisfactorily explained by the neutral air motion caused by the E x B drift deduced from the ground-based geomagnetic data recorded at stations near the meridian of the satellite orbit.

Wu, S. T.↗
NASA NTRS1974

An analysis of the upper atmospheric wind observed by LOGACS

Wind velocities at 140 to 200 km altitude were observed by a low-g accelerometer calibration system (LOGACS) flown on an Agena satellite during a geomagnetic storm. An interesting wind reversal observed by the satellite at auroral latitudes is satisfactorily explained by the neutral air motion caused by the E x B drift deduced from the ground-based geomagnetic data recorded at stations near the meridian of the satellite orbit.

Wu, S. T.↗
NASA NTRS1991

Geomagnetic activity associated with earth passage of interplanetary shock disturbances and coronal mass ejections

Coronal mass ejection events (CMEs) are important occasional sources of plasma and magnetic field in the solar wind at 1 AU, accounting for approximately 10 percent of all solar wind measurements in the ecliptic plane during the last solar activity maximum. Using a recently appreciated capability for distinguishing CMEs in solar wind data in the form of counterstreaming solar wind electron events, this paper explores the overall effectiveness of shock wave disturbances and CMFs in general in stimulating geomagnetic activity. The study is confined to the interval from mid-August 1978 through mid-October 1982, spanning the last solar activity maximum, when ISEE 3 was in orbit about the L1 Lagrange point 220 Re upstream from earth. It is found that all but one of the 37 largest geomagnetic storms in that era were associated with earth passage of CMEs and/or shock disturbances, with the large majority of these storms (27 out of 37) being associated with interplanetary events where earth encountered both a shock and the CME driving the shock (shock/CME events). Although CMEs and/or shock disturbances were increasingly the cause of geomagnetic activity as the level of geomagnetic activity increased, many smaller geomagnetic disturbances were unrelated to these events.

Gosling, J. T.↗
DOE OSTI2022

L -Value and Energy Dependence of 0.1–50 keV O + , He + , and H + Ions for CME and CIR Storms Over the Entire Van Allen Probes Era

Our studies report the first observation of L -value and energy sorted correlation of differential fluxes of 0.1–50 keV O + , He + , and H + ions with different geophysical parameters for 29 Coronal Mass Ejected (CME) and 40 Corotating Interaction Region (CIR)-driven geomagnetic storms during the entire Van Allen Probes era. For both solar wind drivers, ions with ≥1 keV energies show more variability in response to the solar wind changes, while the lower energy (<1 keV) ions are relatively stable. During the in-storm interval, O + ions show maximum flux enhancement and become further prominent during CME storms. O + ion (≥10 keV) fluxes show good correlation with – $V_{sw}B_z$, and Sym-H index during CME-driven storms in the L ~2.5–5.5. Apart from this, the average duration of persistence ($\langleΔt\rangle$) for enhanced fluxes is higher for CIR-driven storms with $\langleΔt\rangle_{O^+}>\langleΔt\rangle_{He^+}>\langleΔt\rangle_{H^+}$ at E ≤ 50 keV in the L ~2.5–5.5. Moreover, the observed value of $\langleΔt\rangle_i$ (where $\textit{i}$ is O + , H + or He + ) increases with the increasing L . Further, we discuss the plausible mechanisms to provide a comprehensive overview of L -values and energy sorted O + , He + and H + ion dynamics for two different categories of solar wind drivers.

79 ASTRONOMY AND ASTROPHYSICS↗