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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Two successful geomagnetic-field-line tracing experiments.

Two field-line tracing experiments were conducted on an L = 1.26 magnetic flux tube over Kauai, Hawaii. Barium vapor was created by the detonation of a highly explosive shaped charge aligned with the geomagnetic field at a 467-km altitude. Barium ions traveled along the field line to the conjugate ionosphere in a tube 3 to 5 km in diameter, producing a visible streak along the entire 6900-km path length. Electric fields perpendicular to the magnetic field caused the ions to drift away from the true conjugate during transit, but extrapolation from subsequent ion drift rates allowed the conjugate to be identified and compared with several field models. Differing ion drift rates and directions at the conjugate points indicated that the electric field is not transferred unattenuated along field lines.

Wescott, E. M.↗
NASA NTRS1974

L = 1.24 conjugate magnetic field line tracing experiments with barium shaped charges

Description of three experiments involving the injection of barium ions into magnetic flux tubes with the aid of high-explosive shaped charges with hollow conical liners of barium metal. In these experiments (called Alco, Bubia, and Loro, respectively) the explosive charges were detonated at altitudes above 500 km, producing jets of barium plasma with initial velocities ranging from 8 to 20 km/sec. The most interesting result of the experiments, which were carried out near L = 1.24 and were successful in tracing an entire field line some 7000 km to the conjugate ionosphere, was the observation that for Loro and probably Alco the direction and rate of drift of the two ends of the field line were identical, whereas those for Bubia differed significantly. In the case of the Bubia event significant differences in magnitude and direction at the conjugate points are noted, which lead to the conclusion that the field line could not have been equipotential during the interval of observation.

Wescott, E. M.↗
NASA NTRS2018

The Twisted Configuration of the Martian Magnetotail: MAVEN Observations

Measurements provided by the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft are analyzed to investigate the Martian magnetotail configuration as a function of interplanetary magnetic field (IMF) BY. We find that the magnetotail lobes exhibit a ~45deg twist, either clockwise or counterclockwise from the ecliptic plane, up to a few Mars radii downstream. Moreover, the associated cross-tail current sheet is rotated away from the expected location for a Venus-like induced magnetotail based on nominal IMF draping. Data-model comparisons using magnetohydrodynamic simulations are in good agreement with the observed tail twist. Model field line tracings indicate that a majority of the twisted tail lobes are composed of open field lines, surrounded by draped IMF. We infer that dayside magnetic reconnection between the crustal fields and draped IMF creates these open fields and may be responsible for the twisted tail configuration, similar to what is observed at Earth.

Martian↗
NASA NTRS2018

The Twisted Configuration of the Martian Magnetotail: MAVEN Observations

Measurements provided by the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft are analyzed to investigate the Martian magnetotail configuration as a function of interplanetary magnetic field (IMF) BY. We find that the magnetotail lobes exhibit a ~45° twist, either clockwise or counterclockwise from the ecliptic plane, up to a few Mars radii downstream. Moreover, the associated cross‐tail current sheet is rotated away from the expected location for a Venus‐like induced magnetotail based on nominal IMF draping. Data‐model comparisons using magnetohydrodynamic simulations are in good agreement with the observed tail twist. Model field line tracings indicate that a majority of the twisted tail lobes are composed of open field lines, surrounded by draped IMF. We infer that dayside magnetic reconnection between the crustal fields and draped IMF creates these open fields and may be responsible for the twisted tail configuration, similar to what is observed at Earth.

Gina A. DiBraccio↗
NASA NTRS1972

Field line motion in the presence of finite conductivity.

The relation of plasma motion to field line motion is determined in the case where the conductivity is imperfect. The imperfect conductivity may result from collisions between plasma particles and neutrals, as in the case of the earth's ionosphere, or from the scattering of charged particles by the enhanced field fluctuations which characterize a turbulent plasma. A magnetic field is assumed which is a given, known function of space and time, and it is further assumed that all field lines intersect an ideally conducting surface and are identified by their points of intersection. It is shown that the relative displacement between drifting particles and moving field lines has significance only when compared with some other pertinent length such as the total particle drift distance. In such a comparison, when the latter quantity is much larger than the first, the particles can be followed by tracing field lines.

Birmingham, T. J.↗
NASA NTRS2013

Source Regions of the Interplanetary Magnetic Field and Variability in Heavy-Ion Elemental Composition in Gradual Solar Energetic Particle Events

Gradual solar energetic particle (SEP) events are those in which ions are accelerated to their observed energies by interactions with a shock driven by a fast coronal mass-ejection (CME). Previous studies have shown that much of the observed event-to-event variability can be understood in terms of shock speed and evolution in the shock-normal angle. But an equally important factor, particularly for the elemental composition, is the origin of the suprathermal seed particles upon which the shock acts. To tackle this issue, we (1) use observed solar-wind speed, magnetograms, and the PFSS model to map the Sun-L1 interplanetary magnetic field (IMF) line back to its source region on the Sun at the time of the SEP observations; and (2) then look for correlation between SEP composition (as measured by Wind and ACE at approx. 2-30 MeV/nucleon) and characteristics of the identified IMF-source regions. The study is based on 24 SEP events, identified as a statistically-significant increase in approx. 20 MeV protons and occurring in 1998 and 2003-2006, when the rate of newly-emergent solar magnetic flux and CMEs was lower than in solar-maximum years and the field-line tracing is therefore more likely to be successful. We find that the gradual SEP Fe/O is correlated with the field strength at the IMF-source, with the largest enhancements occurring when the footpoint field is strong, due to the nearby presence of an active region. In these cases, other elemental ratios show a strong charge-to-mass (q/M) ordering, at least on average, similar to that found in impulsive events. These results lead us to suggest that magnetic reconnection in footpoint regions near active regions bias the heavy-ion composition of suprathermal seed ions by processes qualitatively similar to those that produce larger heavy-ion enhancements in impulsive SEP events. To address potential technical concerns about our analysis, we also discuss efforts to exclude impulsive SEP events from our event sample.

magnetic field↗
NASA NTRS1973

Magnetospheric mapping with quantitative geomagnetic field models

The Mead-Fairfield geomagnetic field models were used to trace field lines between the outer magnetosphere and the earth's surface. The results are presented in terms of ground latitude and local time contours projected to the equatorial plane and into the geomagnetic tail. With these contours various observations can be mapped along field lines between high and low altitudes. Low altitudes observations of the polar cap boundary, the polar cusp, the energetic electron trapping boundary and the sunward convection region are projected to the equatorial plane and compared with the results of the model and with each other. The results provide quantitative support to the earlier suggestions that the trapping boundary is associated with the last closed field line in the sunward hemisphere, the polar cusp is associated with the region of the last closed field line, and the polar cap projects to the geomagnetic tail and has a low latitude boundary corresponding to the last closed field line.

Fairfield, D. H.↗
NASA NTRS1978

Linear force-free fields in the lower corona

Boundary conditions are imposed on the normal component of B on two parallel planes which delineate the force-free volume of linear magnetic fields in low coronal levels of the solar atmosphere. Green's function is employed to ensure that equations for the magnetic field energy remain bounded and smooth. Field line tracings of a simple bipolar source distribution are developed and compared with empirical data obtained from visual observations in H(alpha), EUV, and X-rays.

Barbosa, D. D.↗
NASA NTRS1980

Spacelab energetic ion mass spectrometer

Basic design criteria are given for an ion mass spectrometer for use in studying magnetospheric ion populations. The proposed instrument is composed of an electrostatic analyzer followed by a magnetic spectrometer and simultaneously measures the energy per unit and mass per unit charge of the ion species. An electromagnet is used for momentum analysis to extend the operational energy range over a much wider domain than is possible with the permanent magnets used in previous flights. The energetic ion source regions, ion energization mechanisms, field line tracing, coordinated investigations, and orbit considerations are discussed and operations of the momentum analyzer and of the electrostatic energy analyzer are examined.

Whalen, B. A.↗
NASA NTRS1992

Probing the magnetosphere using chemical releases from the Combined Release and Radiation Effects Satellite

An overview is presented of the chemical release experiments from NASA's Combined Release and Radiation Effects Satellite (CRRES) program. Preliminary results are given for the CRRES investigations of (1) stimulated electron and ion precipitation, (2) ion transport in the magnetotail, (3) critical ionization velocity, (4) field line tracing and parallel acceleration, (5) diamagnetic cavity formation and collapse, and (6) plasma instabilities. The chemical vapor properties from a thermite release mechanism are also briefly described.

Bernhardt, P. A.↗
NASA NTRS1995

Interactive data exploration and particle tracking for general circulation models

The SCENE environment for interactive visualization of complex data sets is discussed. This environment is used to create tools for graphical exploration of atmospheric flow models. These tools may be extended by the user in a seamless manner, so that no programming is required. A module for accurately tracing field lines and particle trajectories in SCENE is presented. This is used to examine the flowfield qualitatively with streamlines and pathlines and to identify critical points in the velocity field. The paper also describes a visualization tool for general circulation models on which the primary features of the environment are demonstrated.

Rosenbaum, R. I.↗
NASA NTRSDate not supplied

Magnetic Mapping in the Inner Magnetosphere using Kamodo

Many models require specialized access and interpolation schemes to effectively extract and interpolate their outputs. In particular, the Block-Adaptive Tree Solarwind Roe Upwind Scheme (BATSRUS) component of the Space Weather Modeling Framework (SWMF) requires Kamodo to take advantage of its block-based adaptive grid structure, and the Lyon-Fedder Mobarry magnetosphere model (or its successor GAMERA) needs a scheme that appreciates the distorted spherical arrangement of grid vertices on a non-orthogonal grid. With the flythrough layer developed by Ringuette et al. (SH42E-2337), the underlying model readers have been adapted to use multiple time steps in a single Python session to perform 4- dimensional interpolations in time and space. Kamodo now utilizes lazy interpolation that loads data only when needed. We present the successful integration of SWMF/BATSRUS magnetosphere access and interpolation into the new 4D Kamodo framework utilizing an external library of C code. Through function composition, Kamodo facilitates the calculation of derived quantities and the transformation of positions and vectors into different coordinate systems. This work is a significant step towards performing field line tracing in Kamodo with SWMF magnetosphere outputs.

Lutz Rastaetter↗
NASA NTRS2023

Prediction and Verification of Parker Solar Probe Solar Wind Sources at 13.3 Rs

Drawing connections between heliospheric spacecraft and solar wind sources is a vital step in understanding the evolution of the solar corona into the solar wind and contextualizing in situ timeseries. Furthermore, making advanced predictions of this linkage for ongoing heliospheric missions, such as Parker Solar Probe (Parker), is necessary for achieving useful coordinated remote observations and maximizing scientific return. The general procedure for estimating such connectivity is straightforward (i.e., magnetic field line tracing in a coronal model) but validating the resulting estimates is difficult due to the lack of an independent ground truth and limited model constraints. In its most recent orbits, Parker has reached perihelia of 13.3R⊙ and moreover travels extremely fast prograde relative to the solar surface, covering over 120° longitude in 3 days. Here we present footpoint predictions and subsequent validation efforts for Parker Encounter 10, the first of the 13.3R⊙ orbits, which occurred in November 2021. We show that the longitudinal dependence of in situ plasma data from these novel orbits provides a powerful method of footpoint validation. With reference to other encounters, we also illustrate that the conditions under which source mapping is most accurate for near-ecliptic spacecraft (such as Parker) occur when solar activity is low, but also require that the heliospheric current sheet is strongly warped by mid-latitude or equatorial coronal holes. Lastly, we comment on the large-scale coronal structure implied by the Encounter 10 mapping, highlighting an empirical equatorial cut of the Alfvèn surface consisting of localized protrusions above unipolar magnetic separatrices.

S. T. Badman↗
NASA NTRSDate not supplied

On the Solar Open Magnetic Flux Problem

The solar magnetic fields emerging from the photosphere into the chromosphere and corona are comprised of a combination of “closed” (field lines with both ends rooted at the Sun) and “open” (field lines with only one end at the Sun) fields. Since the early 2000’s, the magnitude of total unsigned open magnetic flux estimated by coronal models has been in significant disagreement with in situ spacecraft observations, especially during solar maximum. Estimates of total open unsigned magnetic flux using coronal hole observations (e.g., using extreme ultraviolet (EUV) or Helium (He) are in general agreement with the coronal model results and thus show similar disagreements with in situ observations. This paper provides a brief overview of the problem, summarizes the proposed explanations for the discrepancies, and presents results that strongly support the explanation that the discrepancy is due to dynamics at the open-closed boundary. These results are derived from determination of the total unsigned open magnetic flux, utilizing the Wang-Sheeley-Arge (WSA) model at a particular spatial resolution and different field-line tracing methods. One of these methods produces excellent agreement with in situ observations. Our results imply that active regions residing near the boundaries of mid-latitude coronal holes are the primary source of the missing open flux. Furthermore, they resolve many of the seemingly contradictory facts that have made resolving the open-flux problem so difficult.

Charles Arge↗
NASA NTRS1972

ALLMAG, GDALMG, LINTRA: Computer programs for geomagnetic field and field-line calculations

A set of computer programs has been developed for the calculation of the geomagnetic field and the tracing of field lines in space. The basic subroutine, geocentric ALLMAG, contains coefficients for seven recently-published field models as built-in data statements. At execution time the user can vary the model and/or the time period by simply changing input parameters. Subroutine GDALMG is adapted for input and output in geodetic coordinates. ALLMAG and GDALMG are equivalent to Cain's FIELD and FIELDG, with the added flexibility of the choice of seven models. LINTRA traces field lines from any point in space to a specified altitude intersect in the same or opposite hemisphere, using any of the models contained in ALLMAG. Input is in either geocentric or geodetic coordinates, and output is returned in both. McIlwain's INVAR package, which calculates B and L, has been adapted to use ALLMAG. All programs are described in detail, and sample calculations are given.

Stassinopoulos, E. G.↗
NASA NTRS1988

Mapping of auroral kilometric radiation sources to the aurora

Auroral kilometric radiation (AKR) and optical auroral emissions are observed simultaneously using plasma wave instrumentation and auroral imaging photometers carried on the DE 1 spacecraft. The DE 1 plasma wave instrument measures the relative phase of signals from orthogonal electric dipole antennas, and from these measurements, apparent source directions can be determined with a high degree of precision. Wave data are analyzed for several strong AKR events, and source directions are determined for several emission frequencies. By assuming that the AKR originates at cyclotron resonant altitudes, a candidate source field line is identified. When the selected source field line is traced down to auroral altitudes on the concurrent DE 1 auroral image, a striking correspondece between the AKR source field line and localized auroral features is produced. The magnetic mapping study provides strong evidence that AKR sources occur on field lines associated with discrete auroral arcs, and it provides confirmation that AKR is generated near the electron cyclotron frequency.

Huff, R. L.↗
NASA NTRS1990

Magnetic field configuration of the theta aurora

A magnetic configuration of the open magnetosphere is described which is conducive to the formation of the theta aurora when the IMF has a significant northward component. A magnetic field topology and polar cap configuration, derived from a quantitative model of the open magnetosphere that incorporates Crooker's antiparallel merging hypothesis, are presented. Under this hypothesis, when the IMF has a northward component, the dayside merging line bifurcates, leaving a large fraction of the subsolar magnetopause untouched by the merging process. The polar cap, defined by tracing magnetic field lines that connect from the solar wind to the earth, is similarly bifurcated, leaving a sun-aligned stagnation region that is not magnetically connected to the solar wind and may plausibly be associated with the sun-aligned 'bar' of the theta aurora. The model provides testable predictions with regard to the position of this 'convection gap' in both Northern and Southern Hemispheres as functions of IMF direction.

Toffoletto, F. R.↗