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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 181 records · Page 10
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NASA NTRS1982

Data from ISEE-1 for the IMS period

It is pointed out that a great deal of data with potentially interesting collaborative applications has been obtained since the launch of ISEE-1 and ISEE-2 on October 22, 1977. ISEE-1 experiments are related to studies regarding electrons and protons, the plasma wave, the fast plasma, the plasma density, wave propagation, the E-field, cosmic rays and ions, energetic particles, the E-field, and ion composition. A diagram of the magnetosphere is presented, taking into account the approximate positions of the ISEE orbit at different times of the year. Procedures for obtaining data for collaborations are discussed. Early in the planning stage for the ISEE program it was suggested that collaborative experiments involving ISEE-1 and ISEE-3 on one side, and sounding rockets launched from the auroral zone on the other, might be a valuable approach for studying processes by which particles are precipitated into the auroral zone.

Ogilvie, K. W.↗
NASA NTRS1979

Magnetospheric plasma wave research 1975-1978

Research conducted from 1975 through 1978 on magnetospheric plasma waves generated in or passing through the magnetospheres of the earth and Jupiter is reviewed. Attention is given to bow shock whistlers and electrostatic waves, electromagnetic wave packets in the magnetosheath ('lion roars'), nonthermal continuum radiation apparently associated with energetic electrons in the outer radiation zone, electrostatic and magnetic noise and PI2 pulsations in the magnetotail and plasma sheet and polar cusp phenomena. Plasma waves in the auroral zone, including VLF hiss and saucers, electrostatic wave turbulence and kilometric radiation are treated, together with MHD waves and magnetic pulsations, ion cyclotron waves, VLF chorus and hiss and electrostatic electron cyclotron harmonic radiation in and beyond plasmapause, plasmaspheric hiss, whistlers, power line harmonic radiation and controlled wave generation experiments. Observations of plasmasphere and auroral zone phenomena in the ionosphere are discussed, and escaping and trapped plasma waves in the magnetospheres of Jupiter and other planets are considered. Planned future magnetospheric research for the next four years is outlined.

Shawhan, S. D.↗
NASA NTRS2001

What is the Relationship Between Heavy Ion Outflow and High-Latitude Energetic Precipitation?

Second quarter progress report for year 3 on contract NASW-99002 "What is the Relationship between heavy ion outflow and high latitude energetic particle precipitation". In this Project we are studying the relationship between the fluxes, mean energies, and field-aligned flow speeds of escaping suprathermal H+ and 0+ measured by the TEAMS instrument on FAST and the energy flux of precipitating electrons obtained from the LBHL images taken by the UVI camera on POLAR. In this portion of the project we are using UVI images to tell us when substorm onsets occur and how the auroral zone changes during the course of a substorm. We are correlating this information with TEAMS flux measurements made over the auroral zone at times close to these substorms. The goal is to understand how the flux of suprathermal ion outflow varies with substorm phase.

Wilson, Gordon R.↗
NASA NTRS1985

A simulation study of kilometric radiation generation along an auroral field line

A model for the high-altitude auroral zone is combined with local particle simulations in order to assess the quantitative implications of relativistic dispersion for the generation of auroral kilometric radiation. The auroral zone model is described, including the distribution functions for the primary and secondary electron populations and the variations of the total number density with altitude. The analysis shows that the most intense cyclotron maser emission should occur in the 1.75-2.0 R(E) altitude range. At lower altitudes, the secondary electrons are dominant, and the instability saturates at a low level. At higher altitudes, the energy of the primary electron is lower, and again the radiation level drops. The simulations indicate that linear growth rates of the order of 0.002 Omega(e) occur in this region and that the conversion of primary electron energy into AKR is about one percent.

Pritchett, P. L.↗
NASA NTRS2007

Stellar Ablation of Planetary Atmospheres

We review observations and theories of the solar ablation of planetary atmospheres, focusing on the terrestrial case where a large magnetosphere holds off the solar wind, so that there is little direct atmospheric impact, but also couples the solar wind electromagnetically to the auroral zones. We consider the photothermal escape flows known as the polar wind or refilling flows, the enhanced mass flux escape flows that result from localized solar wind energy dissipation in the auroral zones, and the resultant enhanced neutral atom escape flows. We term these latter two escape flows the "auroral wind." We review observations and theories of the heating and acceleration of auroral winds, including energy inputs from precipitating particles, electromagnetic energy flux at magnetohydrodynamic and plasma wave frequencies, and acceleration by parallel electric fields and by convection pickup processes also known as "centrifugal acceleration." We consider also the global circulation of ionospheric plasmas within the magnetosphere, their participation in magnetospheric disturbances as absorbers of momentum and energy, and their ultimate loss from the magnetosphere into the downstream solar wind, loading reconnection processes that occur at high altitudes near the magnetospheric boundaries. We consider the role of planetary magnetization and the accumulating evidence of stellar ablation of extrasolar planetary atmospheres. Finally, we suggest and discuss future needs for both the theory and observation of the planetary ionospheres and their role in solar wind interactions, to achieve the generality required for a predictive science of the coupling of stellar and planetary atmospheres over the full range of possible conditions.

Moore, Thomas E.↗
NASA NTRS1990

Observation of the Z mode with DE 1 and its analysis by three-dimensional ray tracing

Certain Z-mode wave emissions in the earth's magnetosphere have been identified using the wave spectra and polarization measurements of the DE 1 satellite. Although such emissions accompany the aurora, and thus presumably originate from the evening-sector auroral zone, they are found to occur over much wider ranges of latitude and longitude. Since the predicted cyclotron maser emission at the cyclotron frequency could not have produced waves which travel such great distances, as shown by three-dimensional ray tracing, it is proposed instead that these emissions must originate from lower altitudes within the auroral zone and probably from near the plasma frequency inside the auroral plasma cavity.

Hashimoto, Kozo↗
NASA NTRS1992

Auroral X-ray imaging from high- and low-earth orbit

Observations of bremsstrahlung X-rays emitted by energetic electrons impacting the earth's atmosphere can be used for remotely sensing the morphology, intensity, and energy spectra of electron precipitation from the magnetosphere. Two auroral X-ray imagers, developed for future spaceflight, will be discussed. Polar Ionospheric X-ray Imaging Experiment is scheduled for launch on the NASA International Solar-Terrestrial Physics/Global Geospace Science program POLAR satellite in May, 1994. The POLAR orbit, with an apogee and perigee of 9 and 1.8 R(E) (earth radii), respectively, affords the opportunity to image the aurora from high altitude above the north pole continuously for several hours. The Magnetospheric Atmospheric X-ray Imaging Experiment is scheduled for launch aboard the NOAA-I satellite in late 1992. The 800-km polar orbit passes over both the northern and southern auroral zones every 101 minutes. The presentation emphasizes the experimental approaches used to exploit these very different orbits for remote sensing of the earth's auroral zones.

Mckenzie, D. L.↗
NASA NTRS1972

Vlf hiss and related plasma observations in the polar magnetosphere.

This paper presents a study of auroral-zone vlf hiss and low-energy charged-particle observations with the Injun 5 satellite. The results of this study provide a direct verification of the association between auroral-zone vlf hiss and intense fluxes of low-energy electrons with energies on the order of 100 eV to several keV. On the dayside of the magnetosphere, these low-energy electrons are identified with the dayside polar-cusp region observed at higher latitudes with the Imp 5 satellite. At other local times, through the dawn and dusk regions and into the nightside of the magnetosphere, the vlf hiss and low-energy electron precipitation regions are believed to correspond to the extension of the dayside polar cusp into the distant plasma sheet and downstream magnetosheath on the nightside of the magnetosphere. Intense fluxes of upgoing electrons are often observed in a narrow latitudinal band near the low-energy electron precipitation bands. These upgoing electrons are believed to be associated with another type of vlf emission called a saucer, which is frequently observed with Injun 5.

Gurnett, D. A.↗
NASA NTRS1979

Ultralow frequency oscillations of the high-latitude ionospheric electric field

Balloon observations of the horizontal electric field, from six Canadian sites during August 2, 3, 8 and 9 of 1969, have been analyzed for coherent oscillations: right, left, and linearly polarized in the 1-16 mHz range. On any particular day there are 'calm' periods where a number of frequencies in the 1-16 mHz range exist. The length of these periods may vary from a few hours to several hours. The 'disturbed' periods can occur at any time of the day. The length of disturbed periods, number of significant frequencies in the band, and their probability of occurrence show a tendency to increase with latitude up to the auroral zone, beyond which no significant increase has been seen. The regions of the disturbed electric field sometimes cover a wide range of latitudes (greater than 10 deg) and longitudes in the auroral zone. Some of these regions are well defined and fixed in space and may remain unchanged for several hours to sometimes more than a day. For the frequency band studied, polarization of one kind (right or left) may dominate over the other for several hours after which the roles may interchange. These reversals do not show any clear-cut latitudinal dependence. Instead, there is more similarity in their behavior.

Gottlieb, B.↗
NASA NTRS1971

Experimental evidence in support of Joule heating associated with geomagnetic activity

High resolution accelerometer measurements in the altitude region 140 to 300 km from a satellite in a near-polar orbit during a period of extremely high geomagnetic activity indicate that Joule heating is the primary source of energy for atmospheric heating associated with geomagnetic activity. This conclusion is supported by the following observational evidence: (1) There is an atmospheric response in the auroral zone which is nearly simulataneous with the onset of geomagnetic activity, with no significant response in the equatorial region until several hours later; (2) The maximum heating occurs at geographic locations near the maximum current of the auroral electrojet; and (3) There is evidence of atmospheric waves originating near the auroral zone at altitudes where Joule heating would be expected to occur. An analysis of atmospheric response time to this heat shows time delays are apparently independent of altitude but are strongly dependent upon geomagnetic latitude.

Devries, L. L.↗
NASA NTRS1984

Variation of the auroral Birkeland and current pattern associated with the north-south component of the IMF

In this study, the data set acquired from the vector magnetometer on board MAGSAT during the period October 1979 to June 1980 is examined. Auroral zone crossings were sorted by hourly averaged values of the Interplanetary Magnetic Field. The result is a catalog of sorted data files, from which color-coded magnetic local time invariant latitude plots have been generated that image the auroral Birkeland current pattern, over each prescribed parameter range. These images are used to statistically examine the dynamics of the current pattern. Results indicate that during the periods of B(z) less than 0, the region 1 and 2 current system expands toward lower latitudes accompanied by an expansion of the auroral zones. When B(z) is greater than 0, the region 1 and 2 currents continue to flow with greatly reduced amplitude in the presence of extensive small scale structure.

Bythrow, P. F.↗
NASA NTRS1993

Atmospheric energy input and ionization by energetic electrons during the geomagnetic storm of 8-9 November 1991

The Atmospheric X-ray Imaging Spectrometer (AXIS) of the Particle Environment Monitor investigation aboard the Upper Atmosphere Research Satellite monitors energy input to the upper atmosphere due to energetic electrons. Analysis of the AXIS data from the major geomagnetic storm of 8-9 November 1991 is presented. During the November storm, electrons above a few keV flowing into a substantially expanded auroral zone provided the bulk of the ionizing power to the upper atmosphere. At the peak of the disturbance the total AXIS-observed power reached 40 GW. On 9 November the whole day average atmospheric ionization rate in the auroral zone at 80 km altitude exceeded the rate due to solar UV and solar X-rays by a factor of over 10 to 100.

Chenette, D. L.↗
NASA NTRS1984

Path-integrated growth of auroral kilometric radiation

Using Poeverlein's graphical method, three dimensional ray path calculations are performed to evaluate the path-integrated growth of auroral kilometric radiation (AKR). The ray tracing results indicate that waves whose initial wave vector lie in the local meridian plane continue to propagate in that plane and that among these waves, those with frequencies near the cutoff frequency (f sub R = 0) refract substantially, where as those with frequencies well above the cutoff frequency suffer little refraction. It is also shown that waves whose initial wave vector lie outside of the local meridian plane propagate in the longitudinal as well as the radial and the latitudinal directions. The refraction of these waves is also highly dependent upon the wave frequency, i.e., waves with frequencies near f sub R = 0 refract substantially, whereas waves with frequencies much above f sub R = 0 undergo little refraction. In order to test the electron cyclotron maser mechanisms as a method for generation of AKR, a typical electron distribution function measured in the auroral zone by the S3-3 satellite, is used to calculate path-integrated growths of representative rays. The results of this study indicate that electron distribution functions like those measured by the S3-3 satellite are not capable of amplifying cosmic noise background to the observed intensities of auroral kilometric radiation, and that much steeper slopes at the edges of the loss cone are required. The presence of such distribution functions in the auroral zone is plausible if one assumes that backscattered electrons in this region have energies less than a few hundred eV.

Omidi, N.↗
NASA NTRS1975

Mid-latitude VLF emissions observed in the topside ionosphere

Narrow-band VLF emissions observed on different days by Alouette-2 are described. It is found that narrow-band VLF hiss (3.5-7.0 kHz) occurs at midlatitudes (at 54 to 64 deg) in the topside ionosphere during both the geomagnetically disturbed and quiet periods, although the hiss region moves towards the auroral zone during the disturbed period. It is likely that the midlatitude hiss at around 5 kHz is the origin of the narrow-band hiss (5 plus or minus 1 kHz) often observed at ground stations at low latitudes, since no VLF emissions above 2 kHz appear in the auroral zone. The midlatitude VLF hiss observed in the topside ionosphere may be generated by the transverse (electron cyclotron) resonance instability in the magnetosphere.

Ondoh, T.↗
NASA NTRS1989

A theoretical interpretation of upstreaming electrons and elevated conics on auroral field lines

Recent VIKING satellite observations in the auroral zone have shown the association of elevated ion conics (conics with a low energy cutoff above zero) with upward streaming electrons in the presence of low frequency electric field fluctuations. A self-consistent particle simulation was developed which assumed the presence of a steady state electric field on auroral zone field lines capable of accelerating ions up the magnetic field lines. Results from this study show that a low frequency ion-ion two stream instability can be excited. This low frequency instability creates a fluctuating electric field which heats the ions oblique to the magnetic field forming distributions similar to the elevated ion conics. The ion-ion waves also interact resonantly with electrons and accelerates them in the direction of the ion beam.

Ashour-Abdalla, Maha↗
NASA NTRS1980

Possible infrared aurorae on Jupiter

Infrared brightenings near the poles of Jupiter at 8 microns were observed in early 1980 by the NASA 3-m Infrared Telescope Facility at Mauna Kea and the Mayall 4-m telescope at the Kitt Peak National Observatory. It is suggested that these brightenings are related to the auroral zones which are determined by the magnetic mapping of the magnetotail onto the atmosphere, rather than by the Io flux tube. They were present in both hemispheres in January, present only in the north in February, and probably absent in the south in March. When visible, they were only seen in the hemisphere where the auroral zone was oriented toward the earth and absent otherwise.

Caldwell, J.↗
NASA NTRS1983

The relationship of total Birkeland currents to the merging electric field

Magsat data were used to examine the behavior of Birkeland currents during 1100-2000 UT in consecutive orbits passing near the dawn-dusk meridian. The field was measured with a three-axis fluxgate instrument with a resolution of within 0.5 nT, with the sampling occurring every 1/16th sec. A total of 32 crossings of the Northern Hemisphere auroral zone were available for analysis. The changes in the magnetic readings were correlated more closely with variation in the IMF parameters than to the latitudinal width of the changes. Evidence was found for a relationship between the reconnection electric field and the intensity of the large-scale Birkeland current system. The total conductance of the auroral zone was calculated to be about 18.7 mhos.

Bythrow, P. F.↗
NASA NTRS2006

Impact of the Ionosphere on an L-band Space Based Radar

We have quantified the impact that the ionosphere would have on a L-band interferometric Synthetic Aperture Radar (SAR) mission using a combination of simulation, modeling, Global Positioning System (GPS) data collected during the last solar maximum, and existing spaceborne SAR data. We conclude that, except for high latitude scintillation related effects, the ionosphere will not significantly impact the performance of an L-band InSAR mission in an appropriate orbit. We evaluated the strength of the ionospheric irregularities using GPS scintillation data collected at Fairbanks, Alaska and modeled the impact of these irregularities on azimuth resolution, azimuth displacement, peak sidelobe ratio (PSLR), and integrated sidelobe ratio (ISLR). Although we predict that less than 5% of auroral zone data would show scintillation related artifacts, certain sites imaged near the equinoxes could be effected up to 25% of the time because the frequency of occurrence of scintillation is a strong function of season and local time of day. Our examination of ionospheric artifacts observed in InSAR data has revealed that the artifacts occur primarily in the polar cap data, not auroral zone data as was previously thought.

Synthetic Aperture Radar (SAR) ionospheres↗