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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 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

VLA-Max '91 tests of high energy flare physics

The potential for the Very Large Array (VLA) contributions during the coming maximum in solar activity is illustrated by unpublished observations of solar flares on 28 May, 8 June, 24 June, and 30 September 1988. Some of this data appears in the two papers by Willson et al., referenced in this article. The VLA can be used to spatially resolve flaring active regions and their magnetic fields. These results can be compared with simultaneous x ray and gamma ray observations from space. Examples are provided in which spatially separated radio sources are resolved for the pre-burst, impulsive and decay phases of solar flares. The emergence of precursor coronal loops probably triggers the release of stored magnetic energy in adjacent coronal loops. Noise storm enhancements can originate in large-scale coronal loops on opposite sides of the visible solar disk. An interactive feedback mechanism may exist between activity in high-lying 90 cm coronal loops and lower-lying 20 cm ones.

Lang, Kenneth R.↗
NASA NTRS2007

Imaging Thermal He(+)in Geospace from the Lunar Surface

By mass, thermal plasma dominates near-earth space and strongly influences the transport of energy and mass into the earth's atmosphere. It is proposed to play an important role in modifying the strength of space weather storms by its presence in regions of magnetic reconnection in the dayside magnetopause and in the near to mid-magnetotail. Ionospheric-origin thermal plasma also represents the most significant potential loss of atmospheric mass from our planet over geological time. Knowledge of the loss of convected thermal plasma into the solar wind versus its recirculation across high latitudes and through the magnetospheric flanks into the magnetospheric tail will enable determination of the mass balance for this mass-dominant component of the Geospace system and of its influence on global magnetospheric processes that are critical to space weather prediction and hence to the impact of space processes on human technology in space and on Earth. Our proposed concept addresses this basic issue of Geospace dynamics by imaging thermal He(+) ions in extreme ultraviolet light with an instrument on the lunar surface. The concept is derived from the highly successful Extreme Ultraviolet imager (EUV) flown on the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft. From the lunar surface an advanced EUV imager is anticipated to have much higher sensitivity, lower background noise, and higher communication bandwidth back to Earth. From the near-magnetic equatorial location on the lunar surface, such an imager would be ideally located to follow thermal He(+) ions to high latitudes, into the magnetospheric flanks, and into the magnetotail.

Gallagher, D. L.↗
NASA NTRS2008

Simulating the Fate of an Ionospheric Mass Ejection

We report global ion kinetic (GIK) simulations of the 24-25 Sep 1988 storm, with all relevant ionospheric outflows including polar, auroral, and plasmaspheric winds. This storm included substantial periods of northward interplanetary magnetic field, but did develop a Dst of -200nT at its peak. The solar disturbance resulted from a coronal mass ejection that reached a peak dynamic pressure at the magnetosphere of 6.2 nPa, and produced a substantial enhancement of auroral wind oxygen outflow from the dayside, which has been termed an "ionospheric mass ejection" in an earlier paper. We use the LFM global simulation model to produce electric and magnetic fields in the outer magnetosphere, the Strangeway-Zheng outflow scalings with Delcourt ion trajectories to include ionospheric outflows, and the Fok-Obner inner magnetospheric model for the plasmaspheric and ring current response to all particle populations. We assess the combined contributions of heliospheric and geospheric plasmas to the ring current for this event.

Moore, Thomas E.↗
NASA NTRS2009

Stereo Science Results at Solar Minimum

The magnetic fields that drive solar activity are complex and inherently three-dimensional structures. Twisted flux ropes, magnetic reconnection and the initiation of solar storms, as well as space weather propagation through the heliosphere, are just a few of the topics that cannot properly be observed or modeled in only two dimensions. Examination of this three-dimensional complex has been hampered by the fact that solar remote sensing observations have occurred only from the Earth-Sun line, and in situ observations, while available from a greater variety of locations, have been sparse throughout the heliosphere.

Christian, Eric R.↗
NASA NTRS2011

Rapid Rebuilding of the Outer Radiation Belt

Recent observations by the radiation monitor (RDM) on the spacecraft Akebono have shown several cases of greater than 2.5 MeV radiation belt electron enhancements occurring on timescales of less than a few hours. Similar enhancements are also seen in detectors on board the NOAA/POES and TWINS 1 satellites. These intervals are shorter than typical radial diffusion or wave-particle interactions can account for. We choose two so-called "rapid rebuilding" events that occur during high speed streams (4 September 2008 and 22 July 2009) and simulated them with the Space Weather Modeling Framework configured with global magnetosphere, radiation belt, ring current, and ionosphere electrodynamics model. Our simulations produce a weaker and delayed dipolarization as compared to observations, but the associated inductive electric field in the simulations is still strong enough to rapidly transport and accelerate MeV electrons resulting in an energetic electron flux enhancement that is somewhat weaker than is observed. Nevertheless, the calculated flux enhancement and dipolarization is found to be qualitatively consistent with the observations. Taken together, the modeling results and observations support the conclusion that storm-time dipolarization events in the magnetospheric magnetic field result in strong radial transport and energization of radiation belt electrons.

Glocer, A.↗
NASA NTRS2012

The Sun and Earth

Thus the Sun forms the basis for life on Earth via the black body radiation it emits. The Sun also emits mass in the form of the solar wind and the coronal mass ejections (CMEs). Mass emission also occurs in the form of solar energetic particles (SEPs), which happens during CMEs and solar flares. Both the mass and electromagnetic energy output of the Sun vary over a wide range of time scales, thus introducing disturbances on the space environment that extends from the Sun through the entire heliosphere including the magnetospheres and ionospheres of planets and moons of the solar system. Although our habitat is located in the neutral atmosphere of Earth, we are intimately connected to the non-neutral space environment starting from the ionosphere to the magnetosphere and to the vast interplanetary space. The variability of the solar mass emissions results in the interaction between the solar wind plasma and the magnetospheric plasma leading to huge disturbances in the geospace. The Sun ionizes our atmosphere and creates the ionosphere. The ionosphere can be severely disturbed by the transient energy input from solar flares and the solar wind during geomagnetic storms. The complex interplay between Earth's magnetic field and the solar magnetic field carried by the solar wind presents varying conditions that are both beneficial and hazardous to life on earth. This seminar presents some of the key aspects of this Sun-Earth connection that we have learned since the birth of space science as a scientific discipline some half a century ago.

Gopalswamy, Natchimuthuk↗
NASA NTRS2020

Conditions of Loss Cone Filling by Scattering on the Curved Field Lines for 30 keV Protons During Geomagnetic Storm as Inferred From Numerical Trajectory Tracing

The rate of pitch angle scattering on the curved magnetic field lines is well parameterized by the ratio of the minimum field line curvature radius to the maximum effective particle gyroradius (K = RC/rg). The critical value of this ratio (Kcr) corresponding to the loss cone filling is of special interest since it corresponds to the low altitude isotropic boundaries (IBs). The early theoretical estimates gave Kcr = 8, whereas recent estimations of the K parameter on the field lines corresponding to the observed IBs during the geomagnetic storms revealed KIB values in the range of 3–30. We numerically trace the trajectories of the 30 keV protons in the magnetic field of the global magnetohydrodynamic simulation of the intense storm in order to infer statistical distribution of Kcr. The electric field and effects of nonstationarity are neglected in this study. It is found that although the Kcr values do show some variations during the course of the storm, its range is rather narrow 4 < Kcr < 8. The result suggests that higher KIB values found in the observational studies, if not caused by the magnetosphere-ionosphere mapping error, should be attributed to some other mechanism of pitch angle scattering. The Kcr values tend to be lower (4–6) during the main phase because the region of low K values approaches the Earth and the equatorial loss cone size becomes larger due to a larger equatorial magnetic field in the near earth region. The remaining variation of Kcr is explained by the presence of the guide component of the magnetic field.

S Dubyagin↗
NASA NTRS1980

Decametric radio bursts associated with coronal loop structures

The association of X-ray loop structures with type III bursts is examined using soft X-ray (2-54 A) pictures which were obtained from the Skylab S-054 experiment. The properties of meter-decameter wavelength radio bursts (type III) appear to be associated with two different kinds of loop structures: (1) short lived small scale loops, which are found to link magnetic fields of opposite polarity, called X-ray bright points (XBP); and (2) long lasting loop systems which connect opposite magnetic polarities of an active region as well as active region complexes. It is judged that the presence of active region loop complexes on the disk is a necessary yet insufficient condition for the occurrence of a decametric storm and that conditions concerning the geometry of the magnetic field must also be important in the process.

Gergely, T. E.↗
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 NTRS2014

Two-Step Forecast of Geomagnetic Storm Using Coronal Mass Ejection and Solar Wind Condition

To forecast geomagnetic storms, we had examined initially observed parameters of coronal mass ejections (CMEs) and introduced an empirical storm forecast model in a previous study. Now we suggest a two-step forecast considering not only CME parameters observed in the solar vicinity but also solar wind conditions near Earth to improve the forecast capability. We consider the empirical solar wind criteria derived in this study (Bz ≤ −5 nT or Ey ≥ 3 mV/m for t ≥ 2 h for moderate storms with minimum Dst less than −50 nT) (i.e. Magnetic Field Magnitude, B (sub z) less than or equal to -5 nanoTeslas or duskward Electrical Field, E (sub y) greater than or equal to 3 millivolts per meter for time greater than or equal to 2 hours for moderate storms with Minimum Disturbance Storm Time, Dst less than -50 nanoTeslas) and a Dst model developed by Temerin and Li (2002, 2006) (TL [i.e. Temerin Li] model). Using 55 CME-Dst pairs during 1997 to 2003, our solar wind criteria produce slightly better forecasts for 31 storm events (90 percent) than the forecasts based on the TL model (87 percent). However, the latter produces better forecasts for 24 nonstorm events (88 percent), while the former correctly forecasts only 71 percent of them. We then performed the two-step forecast. The results are as follows: (i) for 15 events that are incorrectly forecasted using CME parameters, 12 cases (80 percent) can be properly predicted based on solar wind conditions; (ii) if we forecast a storm when both CME and solar wind conditions are satisfied (∩, i.e. cap operator - the intersection set that is comprised of all the elements that are common to both), the critical success index becomes higher than that from the forecast using CME parameters alone, however, only 25 storm events (81 percent) are correctly forecasted; and (iii) if we forecast a storm when either set of these conditions is satisfied (∪, i.e. cup operator - the union set that is comprised of all the elements of either or both), all geomagnetic storms are correctly forecasted.

geomagnetic storm forecast↗
NASA NTRS2023

Thermal Electron Heat Fluxes Associated with Precipitated Auroral Electrons During the Saint Patrick's Days 2013 and 2015 Geomagnetic Storms

The Rice Convection Model-Equilibrium (RCM-E) and SuperThermal Electron Transport (STET) are combined to investigate electron heat flux formation in the region of the diffuse aurora for the geomagnetic storms of 17 March 2013 and 17 March 2015. The primary electron precipitation into the atmosphere resulting from wave particle scattering in the magnetosphere are simulated by the magnetically and electrically RCM-E during these two geomagnetic storms. The primary precipitating electron fluxes are modified by the STET model by taking into account atmospheric backscatter processes. The modified electron energy fluxes and their mean energies are coupled to the STET code to calculate electron thermal fluxes associated with diffuse aurora on a global scale. We use the simulated heat flux to estimate electron temperatures at the upper ionospheric altitudes and compare them with corresponding observations from the Defense Meteorological Satellite Program satellite.

George V. Khazanov↗
NASA NTRS1995

Large Enhancements in the O/N2 Ratio in the Evening Sector of the Winter Hemisphere During Geomagnetic Storms

In this paper, we have looked for enhancements of the O/N2 ratio in data measured by the Dynamics Explorer 2 (DE 2) satellite in the middle latitudes of the winter hemisphere, based on a prediction that was made by the National Center for Atmospheric Research thermosphere/tonosphere general circulation model (NCAR-TIGCM) that such increases occur. The NCAR-TIGCM predicts that these enhancements should be seen throughout the low latitude region and in many middle latitude locations, but that the enhancements in O/N2 are particularly strong in the middle-latitude, evening-to-midnight sector of the winter hemisphere. When this prediction was used to look for these effects in DE 2 NACS (neutral atmosphere composition spectrometer) data, large enhancements in the O/N2 ratio (approx. 50 to 90%) were seen. These enhancements were observed during the main phase of a storm that occurred on November 24, 1982, and were seen in the same region of the winter hemisphere predicted by the NCAR-TIGCM. They are partially the result of the depletion of N2 and, as electron loss is dependent on dissociative recombination at F(sub 2) altitudes, they have implications for electron densities in this area. Parcel trajectories, which have been followed through the NCAR-TIGCM history file for this event, show that large O/N2 enhancements occur in this limited region in the winter hemisphere for two reasons. First, these parcels of air are decelerated by the antisunward edge of the ion convection pattern; individual parcels converge and subsidence occurs. Thus molecular-nitrogen-poor air is brought from higher to lower heights. Because neutral parcels that are found a little poleward of the equatorial edge of the eveningside convection pattern are swept inward toward the center of the auroral oval, the enhancements occur only in a very limited range of latitudes. Second, nitrogen-poor air is transported from regions close to the magnetic pole in the winter hemisphere. During geomagnetic storms, enhanced meridional winds are driven by the increased pressure-gradient force that is associated with intensified Joule heating in the auroral oval. These pressure-driven winds decrease rapidly on the dayside beyond the auroral oval where the parcels originate, limiting the region into which the parcels can be transported. Thus these two processes drive values of O/N2 in a limited region of the winter hemisphere, and reinforce only in the evening sector, causing large changes in this region.

Burns, A. G.↗
NASA NTRS1971

Geomagnetic storm particles in the high-latitude magnetotail.

Nearly monoenergetic positive ions flowing outward along magnetic-field lines in the high-latitude magnetotail, outside the plasma sheet, have been observed with Vela satellites. These ions, probably mainly protons, are detected only during geomagnetic storms. The ?storm particles' have average energies per charge ranging from about 0.3 to 3 kV, but at any instant the energy distribution is quite narrow, sometimes less than 10%. Their angular distribution is usually narrow, sometimes about 6 deg. Particles with storm-particle characteristics are not observed in the plasma sheet. Possible sources of the storm particles are considered, including the solar wind, magnetosheath, polar cusps, polar wind, or ionosphere, plasma sheet, solar neutral hydrogen streams, reconnection transfer of plasma into the magnetotail from the polar cusps, polar wind, or polar ionosphere, and parallel electric-field acceleration of the polar wind or ionosphere ions along the polar-cap magnetic-field lines. Of these possibilities, the electric-field acceleration is favored.

Bame, S. 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 NTRS1990

Impulsive microwave burst and solar noise storm emission resolved with the VLA

The evolution of a microwave burst at 20.7 cm wavelength and a type I noise storm at 91.6 cm wavelength are examined using VLA. The magnetic loops in the two spectral regions are studied. The sizes and brightness temperatures of the 20.7 cm burst sources are compared with those predicted by multithermal and nonthermal models of microwave burst emission of Dulk and Dennis (1982). The data reveal that: (1) the precursor, impulsive, and post-impulsive phases of the 20.7 cm burst are located in spatially separated sources; (2) the gradual enhancement of a 91.6 cm noise storm continuum source suggests a feed-back mechanism exists between activity in higher and lower lying loops; and (3) the derived magnetic field strengths at 20.7 cm for the nonthermal models are 35-160 G with core field strengths of 125-220 G.

Willson, Robert F.↗
NASA NTRS2011

SA13B-1900 Auroral Charging of the International Space Station

Electrostatic potential variations of the International Space Station (ISS) relative to the space plasma environment are dominated by interaction of the negatively grounded 160 volt US photovoltaic power system with the plasma environment in sunlight and inductive potential variations across the ISS structure generated by motion of the vehicle across the Earth's magnetic field. Auroral charging is also a source of potential variations because the 51.6? orbital inclination of ISS takes the vehicle to sufficiently high magnetic latitudes to encounter precipitating electrons during geomagnetic storms. Analysis of auroral charging for small spacecraft or isolated insulating regions on ISS predict rapid charging to high potentials of hundreds of volts but it has been thought that the large capacitance of the entire ISS structure on the order of 0.01 F will limit frame potentials to less than a volt when exposed to auroral conditions. We present three candidate auroral charging events characterized by transient ISS structure potentials varying from approximately 2 to 17 volts. The events occur primarily at night when the solar arrays are unbiased and cannot therefore be due to solar array current collection. ISS potential decreases to more negative values during the events indicating electron current collection and the events are always observed at the highest latitudes along the ISS trajectory. Comparison of the events with integral >30 keV electron flux measurements from NOAA TIROS spacecraft demonstrate they occur within regions of precipitating electron flux at levels consistent with the energetic electron thresholds reported for onset of auroral charging of the DMSP and Freja satellites. In contrast to the DMSP and Freja events, one of the ISS charging events occur in sunlight.

Minow, Joseph I.↗
NASA NTRS2011

Earth Orbit Raise Design for the Artemis Mission

The Artemis mission is an extension of the Themis mission. The Themis mission1 consisted of five identical spacecraft in varying sized Earth orbits designed to make simultaneous measurements of the Earth's electric and magnetic environment. Themis was designed to observe geomagnetic storms resulting from solar wind's interaction with the Earth's magnetosphere. Themis was meant to answer the age old question of why the Earth's aurora can change rapidly on a global scale. The Themis spacecraft are spin stabilized with 20 meter long electric field booms as well as several shorter magnetometer booms. The goal of the Artemis2 mission extension is to deliver the field and particle measuring capabilities of two of the Themis spacecraft to the vicinity of the Moon. The Artemis mission required transferring two Earth orbiting Themis spacecraft on to two different low energy trans-lunar trajectories ultimately ending in lunar orbit. This paper describes the processes that resulted in successful orbit raise designs for both spacecraft.

spin stablized↗
NASA NTRS1973

Mass motion in solar flares

Mass motions in solar flares are here considered in terms of a previously proposed model. Particle acceleration occurs during reconnection of a current sheet located at coronal heights. The downward component of the particle flux produces an impulsive hard X-ray burst and heats the upper layers of the chromosphere sufficiently to lead to explosive evaporation. Some of the evaporated gas remains trapped in newly closed magnetic field lines and is responsible for the soft thermal component of X-ray emission. Gas which flows along open magnetic field lines subsequently forms a plasmoid which is ejected by magnetic stresses into interplanetary space and may subsequently cause a geomagnetic storm. Analysis of a highly simplified model leads to formulas for the density, temperature, and other parameters of the flare-produced plasma in terms of a length scale and mean magnetic field strength for the flare.

Sturrock, P. A.↗