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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS2009

Physical Processes for Driving Ionospheric Outflows in Global Simulations

We review and assess the importance of processes thought to drive ionospheric outflows, linking them as appropriate to the solar wind and interplanetary magnetic field, and to the spatial and temporal distribution of their magnetospheric internal responses. These begin with the diffuse effects of photoionization and thermal equilibrium of the ionospheric topside, enhancing Jeans' escape, with ambipolar diffusion and acceleration. Auroral outflows begin with dayside reconnexion and resultant field-aligned currents and driven convection. These produce plasmaspheric plumes, collisional heating and wave-particle interactions, centrifugal acceleration, and auroral acceleration by parallel electric fields, including enhanced ambipolar fields from electron heating by precipitating particles. Observations and simulations show that solar wind energy dissipation into the atmosphere is concentrated by the geomagnetic field into auroral regions with an amplification factor of 10-100, enhancing heavy species plasma and gas escape from gravity, and providing more current carrying capacity. Internal plasmas thus enable electromagnetic driving via coupling to the plasma, neutral gas and by extension, the entire body " We assess the Importance of each of these processes in terms of local escape flux production as well as global outflow, and suggest methods for their implementation within multispecies global simulation codes. We complete 'he survey with an assessment of outstanding obstacles to this objective.

Moore, Thomas Earle↗
NASA NTRS1989

Influence of charging environments on spacecraft materials and system performance

An overview is presented of potential interactions that can occur on spacecraft operating in space environments. These interactions are discussed in detail. The environment acts on spacecraft in such a way that charging of exterior surfaces occurs. The consequences from this charging then affect system operational performance. Hence, it is the coupling of this exterior charging to system performance that is of concern here. These interactions were first discovered in the spacecraft charging phenomena in which the geomagnetic substorms charged external surfaces to a level that discharges occurred. As a result of the discharge, electronic systems either changed logic state (anomalous switching) or failed. These interactions can occur in all orbits. The type associated with geosynchronous orbits is called passive since the environment provides the charging mechanism. This type can also occur in polar orbits due to auroral charging environments. In low Earth orbits, the thermal plasma alleviates charging environment concerns, but system operations can induce similar effects.

Stevens, N. John↗
NASA NTRS1994

Investigation of S3-2 satellite data for local time variation of energetic electron precipitation

Data on precipitating electrons from the S3-2 satellite were investigated for local time variation at four L = 4 stations in the southern hemisphere. The equatorial pitch angles of electrons mirroring at 100 km, assumed to be the edge of the bounce loss cone, are calculated for L = 4 using the International Geomagnetic Reference Field for the epoch of the S3-2 data, along with the variation in mirror altitude per degree of equatorial pitch angle. The largest obstacle to the investigation was uneven sampling in terms of local time for all of the stations. However, this situation was improved upon by the use of S3-2 measurements at the conjugate locations of the four stations which provided additional data on electrons in the southern hemisphere bounce loss cone. Evidence for an effect of the dawn-to-dusk geoelectric field was found at two of the stations, Halley Bay and Siple, in the form of a minimum in electron precipitation at dusk. However, the present study does not completely resolve the question of local time modulation of electron precipitation at L = 4 in the southern hemisphere. Furthermore, while the average precipitation was lowest at the Kerguelen site, as would be expected on the basis of drift loss cone (DLC) theories, the intensity at that site exceeds the level that is expected on the basis of these DLC theories.

Robbe, S.↗
NASA NTRS2018

Geomagnetically Induced Currents Caused by Interplanetary Shocks with Different Impact Angles and Speeds

The occurrence of geomagnetically induced currents (GICs) poses serious threats to modern technological infrastructure. Large GICs result from sharp variations of the geomagnetic field (dB∕dt) caused by changes of large-scale magnetospheric and ionospheric currents. Intense dB∕dt perturbations are known to occur often in high-latitude regions as a result of storm time substorms. Magnetospheric compressions usually caused by interplanetary shocks increase the magnetopause current leading to dB∕dt perturbations more evident in midlatitude to low-latitude regions, while they increase the equatorial electrojet current leading to dB∕dt perturbations in dayside equatorial regions. We investigate the effects of shock impact angles and speeds on the subsequent dB∕dt perturbations with a database of 547 shocks observed at the L1 point. By adopting the threshold of dB∕dt = 100 nT/min, identified as a risk factor to power systems, we find that dB∕dt generally surpasses this threshold when following impacts of high-speed and nearly frontal shocks in dayside high-latitude locations. The same trend occurs at lower latitudes and for all nightside events but with fewer high-risk events. Particularly, we found nine events in equatorial locations with dB∕dt > 100 nT/min. All events were caused by high-speed and nearly frontal shock impacts and were observed by stations located around noon local time. These high-risk perturbations were caused by sudden strong and symmetric magnetospheric compressions, more effectively intensifying the equatorial electrojet current, leading to sharp dB∕dt perturbations. We suggest that these results may provide insights for GIC forecasting aiming at preventing degradation of power systems due to GICs.

Oliveira, D. M.↗
NASA NTRS1990

Near equatorial signatures of dynamic auroral processes

Low energy electrons detected in the midmagnetosphere near the geomagnetic equator are hypothesized to originate from the auroral region near the ionospheric ends of the flux tubes. Electrons between 0.1 and 25 eV having pitch angle distributions peaked within 5 deg of B are routinely observed with electron spectrometers on the AMPTE/CCE satellite at radial distances of 7 R(e) to apogee at 9 R(e). If of auroral origin, as suggested, the detection of such fluxes provides important information about the auroral acceleration process, its dynamics, and about the effects of pitch angle scattering mechanisms in the magnetosphere.

Klumpar, D. M.↗
NASA NTRS1986

Solar wind control of the Geomagnetic Mass Spectrometer

Evidence from Dynamics Explorer retarding-ion mass-spectrometer data collected between 1981 and 1983 for the mass dispersion of ionospheric plasma in the polar cap, known as the Geomagnetic Mass Spectrometer, is discussed, and implications of this new source of ionospheric ions for the magnetosphere are considered. A localized source of energization of ionspheric H(+), He(+), O(+) and N(+) ions in the polar cusp yields a source of upswelling plasma that is transported into the magnetosphere, and equal heating of the ion species results in field-aligned flow velocities which are inversely proportional to the square root of the ion mass. The present phenomenon is produced by the resulting velocity filter effect of solar-driven ExB ion convection. The influence of solar wind conditions on the outflow via the polar cap ExB convection pattern is also discussed.

Waite, J. H., Jr.↗
NASA NTRS1992

Prediction of LDEF ionizing radiation environment

The Long Duration Exposure Facility (LDEF) spacecraft flew in a 28.5 deg inclination circular orbit with an altitude in the range from 172 to 258.5 nautical miles. For this orbital altitude and inclination two components contribute most of the penetrating charge particle radiation encountered - the galactic cosmic rays and the geomagnetically trapped Van Allen protons. Where shielding is less than 1.0 g/sq cm geomagnetically trapped electrons make a significant contribution. The 'Vette' models together with the associated magnetic filed models were used to obtain the trapped electron and proton fluences. The mission proton doses were obtained from the fluence using the Burrell proton dose program. For the electron and bremsstrahlung dose we used the Marshall Space Flight Center (MSFC) electron dose program. The predicted doses were in general agreement with those measured with on-board thermoluminescent detector (TLD) dosimeters. The NRL package of programs, Cosmic Ray Effects on MicroElectronics (CREME), was used to calculate the linear energy transfer (LET) spectrum due to galactic cosmic rays (GCR) and trapped protons for comparison with LDEF measurements.

Watts, John W.↗
NASA NTRS1982

Proton temperature anisotropy in the polar wind

The steady state flow of a fully ionized H(+)-O(+) electron plasma along geomagnetic field lines in the high-latitude topside ionosphere is studied. The theoretical formulation is based on a 13-moment system of transport equations, and allows for different species temperatures parallel and perpendicular to the geomagnetic field and nonclassical heat flows. For subsonic and supersonic flows, an appreciable H(+) temperature anisotropy occurs at all altitudes above 1500 km, and tends to be regulated at high altitudes. The direction of the temperature anisotropy is related to the direction of the H(+) heat flow to some extent; for supersonic flow an upward flow of heat from the lower ionosphere is required, while for subsonic flow solutions can be obtained with a downward H(+) heat flow. For subsonic flow, H(+)-H(+) collisions have an important effect on the H(+) stress and heat flow balance at all altitudes between 1500 and 12,000 km.

Schunk, R. W.↗
NASA NTRS1990

Longitudinal variation of mid-latitude hiss from six long duration balloon flights

The longitudinal variation of midlatitude hiss as measured on six balloons at latitudes of 35-55 deg S, shows a significant minimum at 70-80 deg E, about 1000 km east of the geomagnetic conjugate of the Soviet transmitter UMS (17.1 kHz). It is suggested that the well documented pitch-angle diffusion induced by the UMS signal removes the ability of the trapped electrons to maintain the amplification of the hiss to at least the reflection and reducting losses (about 20 dB) at the ends of the echoing ducted path. The eastward shift of the minimum from the conjugate of UMS is primarily caused by the time taken by the eastward-drifting electrons to recover this ability, though the effect is enhanced by the east-west asymmetry in the propagation of hiss under the ionosphere.

Dowden, R. L.↗
NASA NTRS1990

Cleft contribution to ring current formation

The storm time transport of ionospheric plasma from the 'cleft fountain' to the plasma sheet and ring current is investigated by means of three-dimensional trajectory codes. Using observations to define the source location and flow rate, test particles are traced during a 'taillike' to 'dipolelike' reconfiguration of the geomagnetic field. Emphasis is placed on the behavior of heavy ions of low charge state, O(+). As a result of their long periods of gyration, these ions are highly sensitive to rapid field variations and possibly display transient nonadiabatic motions. It is demonstrated that O(+) which have originated in the high-latitude ionosphere but which find themselves in the vicinity of the equator at substorm onset can experience considerable energization (from several keV up to several hundred keV) and pitch angle increase leading to trapping, as an effect of the induced electric field.

Delcourt, D. C.↗
NASA NTRS1994

Dynamics Explorer 2 observations of equatorial thermospheric winds and temperatures: Local time and longitudinal dependences

We have analyzed a large database of Dynamics Explorer 2 (DE 2) measurements of equatorial (less than + or - 9 degs latitude) thermospheric neutral temperatures and horizontal wind components in the altitude range from 200 to 400 km for quiet and active geomagnetic conditions (Kp less than 3 and Kp greater than 3, respectively). Local time variations and longitudinal dependences on the duskside, dayside, and nightside have been separately examined. The dayside hourly averaged neutral zonal winds are relatively insensitive to variations in geomagnetic activity and appear to show an inverse dependence (lower zonal wind speed for higher Kp) in the midnight-dawn local time sector. The duskside neutral temperatures show a region of enhancement (by approximately 60 K) over the South Atlantic magnetic anomaly. The quiet time zonal winds are weaker than the corresponding active time zonal winds on the dayside near the South Atlantic magnetic anomaly. Enhanced ionization in the region, which increases the ion drag on the neutral gas, is suggested as the causal mechanism for these effects. The DE 2 averaged measurements have also been compared with MSIS-86/HWM90 and VSH models. The data and models are in good general agreement, though, the MSIS-86/HWM90 model predicts stronger dayside zonal winds than are observed under active conditions and the VSH model appears to underestimate the magnitude of the dayside zonal winds for both high and low Kp cases.

Wu, Q↗
NASA NTRS1972

A brief review of ionospheric scintillation fading effects as observed in NASA satellite tracking and data acquisition networks.

Discussion of some results of the effects of ionospheric irregularities on NASA satellite tracking and data acquisition operations. Ionospheric scintillation fading produced by irregularities has been observed at 136 MHz (vhf), 400 MHz (uhf), 1550 MHz (L-band) and 1700 to 2200 MHz (S-band). Details of these observations are presented. Vhf scintillation effects are evident in both auroral and equatorial regions. Fading effects decrease with increasing radio frequency in the auroral region. The same frequency dependence for fading is not observed in the equatorial region. Although there is a seasonal and diurnal character to scintillation in the equatorial region, fading effects are usually more severe than in the auroral region for a given radio frequency. Space diversity measurements indicate that reasonable solutions for vhf telemetry problems are available for either region. Space diversity should provide a solution for microwave frequencies as well. Ionospheric fading amplitude for 1700 MHz is relatively small in the auroral region. In the equatorial region amplitude fading levels for 1550-MHz signals from ATS-5 are often much larger than expected. Observations of the Apollo Lunar Surface Experiment Package (ALSEP) operating at 2300 MHz observed near the geomagnetic equator show fading peaks in excess of 15 dB.

Golden, T. S.↗
NASA NTRS1972

Geomagnetically trapped carbon, nitrogen, and oxygen nuclei.

Results of measurements carried out with the University of Chicago nuclear composition telescope on the Ogo 5 satellite, establishing the presence of 13- to 33-MeV/nucleon geomagnetically trapped C and O nuclei, with some evidence for N nuclei. These trapped nuclei were found at L less than or equal to 5 and near the geomagnetic equator. The data cover the period from Mar. 3, 1968, to Dec. 31, 1969. The distribution of CNO flux as a function of L is given. No change in the intensity of the average trapped CNO flux was detected by comparing data for 1968 and 1969. The results reported set a new value for the observed high energy limit of trapping as described by the critical adiabaticity parameter. The penetration of solar flare CNO up to L = 4 was observed twice in 1968, in disagreement with Stormer theory predictions. The effects of these results on some models for the origin of the trapped radiation are discussed.

Mogro-Campero, A.↗
NASA NTRS1973

A satellite measurement of cosmic-ray abundances and spectra in the charge range 2 less than or equal to 7 less than or equal to 10

The composition of the nuclear component of the cosmic radiation was studied to yield information concerning the source, propagation, and confinement of cosmic rays within the galaxy. The first comprehensive satellite measurement is presented of cosmic-ray composition and spectra in the charge range 2 equal to or less than Z equal to or less than 10 using the geomagnetic field as a rigidity analyzer through the entire range of vertical cutoffs. The results indicate that the spectra of all the elements in the observed range are similar, and thus that various ratios of elemental abundances are nearly independent of rigidity over the range 2 equal to or less than P equal to or less than 15 GV. Calculations of the propagation of cosmic rays through the interstellar and interplanetary media predict that there should be a variation with rigidity of ratios of various elements, because of the charge-dependent effects of ionization of the interstellar gas by the cosmic rays. The absence of this variation can be explained by assuming a rigidity-dependent confinement of the cosmic rays in the galaxy.

Brown, J. W.↗
NASA NTRS1973

Solar wind and substorm-related changes in the lobes of the geomagnetic tail

The relationship of the geomagnetic tail lobe energy density to solar wind dynamic pressure, the north-south component of the interplanetary magnetic field, and substorm expansion onsets is investigated. Enhanced lobe energy densities are observed to follow both southward turnings of the interplanetary magnetic field and solar wind dynamic pressure increases. An empirical relationship is developed relating the tail lobe magnetic energy density to the solar wind dynamic pressure by using data obtained when the interplanetary field was northward. Localized, off-center, or multiple-onset substorm expansion phases are shown to have little effect on the lobe magnetic field. A positive correlation is found between magnetosphere-wide substorm expansions and decreases in the lobe energy density. The positive correlation of the energy density with both the solar wind dynamic pressure and a southward interplanetary magnetic field and the positive correlation between magnetospheric substorm activity and lobe energy density decreases are demonstrated to be consistent with a phenomenological model of substorm behavior.

Caan, M. N.↗
NASA NTRS1984

Observations relating changes in thermospheric composition to depletions in topside ionization during the geomagnetic storm of September 1982

In situ measurements taken over midlatitudes by the Dynamics Explorer 2 spacecraft during a geomagnetic substorm show that a direct correlation exists between depletions in the O/N2 density ratio and in the topside electron density, Ne. On the basis of this correlation, it is concluded that, for the storm of September 1982, losses of free electrons via oxygen and nitrogen chemistry near the F2 peak dominate over wind-induced plasma transport in determining the observed stormtime variations of topside Ne at higher latitudes. However, the appearance of an enhancement in topside Ne along 20-deg invariant latitude indicates that an equatorial wind did develop and was effective in increasing gas temperatures and in generating topside Ne enhancement at lower latitudes.

Miller, N. J.↗
NASA NTRS1985

Transverse motion of high-speed barium clouds in the ionosphere

Simulation results, based on a field-line-integrated, two-dimensional, electrostatic model, are presented for the motion of a barium cloud injected transverse to the geomagnetic field in the ionosphere at high speeds. It is found that the gross evaluation of injected plasma clouds depends on the initial conditions, as well as the nature of the background coupling. For a massive (mass of about 10 kg), orbital (velocity of about 5 km/s) release in the F region (350-450 km), it is found that plasma clouds can drift tens of kilometers across the magnetic field in tens of seconds after ionization. This type of release is similar to those which are planned for the Combined Release and Radiation Effects Satellite mission.

Mitchell, H. G., Jr.↗
DOE OSTI2025

Predicting cutoff L-shells of solar protons using the GPPSn particle dataset

Solar energetic protons (SEPs) arriving at the Earth trigger severe radiation storms in the near-Earth space, directly impacting space missions operating at various altitudes. Therefore, monitoring SEP events and predicting the penetration depths of solar protons are critical for aerospace sectors. Building on previous efforts, here we demonstrate the feasibility of using proton measurements from the Global Prompt Proton Sensor network (GPPSn), enabled by Los Alamos National Laboratory developed combined X-ray dosimeters aboard GPS satellites, to characterize and predict the penetration of solar protons into the geomagnetic field. The inclined medium-Earth-orbits (MEOs) of the global GPS constellation offer a unique advantage of allowing simultaneous measurements of penetrating solar protons inside both open- and closed-field line regions. Therefore, the L-profiles of ∼10s–100 MeV solar protons and their associated cutoff L-shells can be determined from the GPPSn dataset, using predefined threshold proton flux values rather than traditional flux ratios. After examining a list of SEP event intervals across solar cycles 23, 24 and 25—including the 2024 Mother’s Day superstorm, we showcase how the latest GPPSn proton dataset (release v1.10), reprocessed and calibrated, can not only be used to monitor solar proton distributions inside the dynamic geomagnetic field for individual events, but also to derive a new empirical model linking cutoff L-shells with several key space weather parameters. This newly developed SEPCL-MEO model demonstrates high predictive performance; for example, predictions for > 30 MeV solar protons yield a correlation coefficient of 0.85 and performance efficiency of 0.67 when validated against GPPSn observations. Results from this pilot study underscores the scientific and operational value of the GPPSn dataset, and this dataset—when paired with machine-learning techniques—can play a critical role in observing and predicting the effects of future incoming SEP events, including extreme ones.

58 GEOSCIENCES↗