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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 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Satellite operations support expert system

The Satellite Operations Support Expert System is an effort to identify aspects of satellite ground support activity which could profitably be automated with artificial intelligence (AI) and to develop a feasibility demonstration for the automation of one such area. The hydrazine propulsion subsystems (HPS) of the International Sun Earth Explorer (ISEE) and the International Ultraviolet Explorer (IUS) were used as applications domains. A demonstration fault handling system was built. The system was written in Franz Lisp and is currently hosted on a VAX 11/750-11/780 family machine. The system allows the user to select which HPS (either from ISEE or IUE) is used. Then the user chooses the fault desired for the run. The demonstration system generates telemetry corresponding to the particular fault. The completely separate fault handling module then uses this telemetry to determine what and where the fault is and how to work around it. Graphics are used to depict the structure of the HPS, and the telemetry values displayed on the screen are continually updated. The capabilities of this system and its development cycle are described.

Source record↗
NASA NTRS1986

Satellite interferometric measurements of auroral kilometric radiation

The first satellite interferometric measurements of auroral kilometric radiation were performed by cross-correlating the waveforms detected by the ISEE 1 and ISEE 2 spacecraft. High correlations were found for all projected baselines, with little or no tendency to decrease even for the longest baselines. For incoherent radiation, the correlation as a function of the baseline is the Fourier transform of the source brightness distribution, implying an average source region diameter for all of the bursts analyzed of less than about 10 km. For such small source diameters, the required growth rates are too large to be explained by existing incoherent theories, strongly indicating that the radiation must be coherent. For coherent radiation, an upper limit to the source region diameter can be inferred instead from the angular width of the radiation pattern. The angular width of the radiation pattern must be at least 2.5 deg, implying that the diameter of the source must be less than about 20 km.

Baumback, M. M.↗
NASA NTRS1987

Enhancements of energetic ions associated with travelling compression regions in the deep geomagnetic tail

This paper presents a representative example of an enhancement in energetic ion flux associated with the International Sun-Earth Explorer 3 (ISEE 3) spacecraft's encounter with a traveling compression region (TCR). Data from the energetic particle anisotropy spectrometer (EPAS) instrument on ISEE 3 are studied, along with magnetic field data from the vector helium magnetometer. It is concluded that the ion enhancements seen are spatial in nature, thus supporting the idea that TCRs are the lobe signatures of plasmoids moving along the magnetotail, away from earth.

Murphy, N.↗
NASA NTRS1986

Compositional changes, time and density variations in the magnetosphere associated with Birkeland currents and particle acceleration

Birkeland currents, parallel electric fields and plasma instabilities often occur together in time and space and play an important role in large scale plasma motions between the ionosphere and magnetosphere and along the magnetic field in the magnetosphere. The results of the plasma movements are large density and composition variations in the ionosphere and magnetosphere. Observations from ISIS-2 at 1400 km altitude show large densities with heavy ions dominating in regions with upward Birkeland currents, and low densities and light ions in regions with downward currents. Observations from ISEE-1 in field aligned current regions at 10,000 to 15,000 km altitude show transverse heating of protons and oxygen ions to 250 eV. Because of the different mobility of the protons and oxygen ions the proton flow is important in the beginning of the events but later the outflow becomes almost pure oxygen. Similarly ISEE-1 observations of outgoing field ion beams at 10,000 to 15,000 km altitude show time variations in the H+/O+ ratios and a dominance of O+ later in the events.

Ungstrup, E.↗
NASA NTRS1987

Do flux transfer events cause long-period micropulsations in the dayside magnetosphere?

Russell and Elphic (1979) suggested the possibility that flux transfer events (FTEs) generate long-period micropulsations in the outer, dayside magnetosphere. The reasons for this hypothesis are examined and results are presented for two pulsation surveys designed to test it. In the first survey, observations of micropulsations by GOES 2 are compared with ISEE 3 and IMP observations of interplanetary magnetic field (IMF) direction; since FTEs are highly correlated with southward IMF, a similar correlation between pulsations and southward IMF was sought. In the second survey, a catalog of ISEE 1 and 2 magnetopause crossings is compared with magnetometer readings from GOES 2 and 3 to determine whether Pc 4 and Pc 5 pulsations are more likely to occur after FTEs have taken place. Results indicate that there is a correlation between FTEs and transversely polarized Pc 4 pulsations with periods between 60 and 120 s, but not between FTEs and Pc pulsations with periods greater than 120 s. This suggests that the generating (or driving) frequency associated with FTEs lies between 60 and 120

Gillis, E. J.↗
NASA NTRS1987

Statistical properties of magnetic field fluctuations in the distant plasmasheet

Short (less than 1 min) and long time (greater than 5 min) variations of the plasmasheet magnetic field have been examined during all intervals when ISEE-3 was at distances x less than -200 earth radii. It is determined that short period magnetic turbulence increases by a factor of about 3 with increasing geomagnetic activity, as indicated by AE. In contrast, long period field variations with North-then-South signatures at plasmasheet entry occur about 2.5 times more frequently than South-then-North signatures. This result, combined with other previous ISEE-3 results, is in agreement with the interpretation that the North-South plasmasheet features are plasmoids propagating tailward. However, a statistical examination of the geomagnetic activity relationship indicates that there does not appear to be any substorm dependence on these North-South events.

Tsurutani, Bruce T.↗
NASA NTRS1987

Aspects of interplanetary plasma turbulence

Data acquired in the free solar wind by the ISEE 1 and ISEE 2 propagation experiment were used to obtain the power spectra of fluctuations in electron density; a maximum-entropy technique has made it possible to exploit fully the intrinsic precision of the in situ measurements. The results have led to a new determination of the anisotropy of density fluctuations in the solar wind, which is in conflict with certain expectations based on the propagation of Langmuir waves, but is in agreement with multistation interplanetary-scintillation measurements: it could well be that Langmuir wave growth rates during type III solar bursts are much larger than has been inferred from the electron distribution function, whose measurement involves averaging over relatively long time intervals. The relation between the fluctuation level and the mean density is studied, and tentative evidence for a correlation between the relative fluctuation level and proton temperature is presented.

Celnikier, L. M.↗
NASA NTRS1987

Strong electron heating at the earth's bow shock

The paper reports on two sets of bow shock crossings observed by the ISEE 1 and ISEE 2 spacecraft, in which very large electron temperature increases were found. When the two sets of shocks with the large electron heating were compared with the rest of the 52 bow shock crossings of the compiled series, these sets were found to correlate with an unusually high upstream solar wind flow speed. The highest correlation was found between the amount of electron heating, expressed by the difference in temperature between the downstream and upstream electrons (rather than their ratio), and the total change in the bulk flow energy per particle across the shock. The results suggest that the appropriate quantity to consider in studies of electron heating at shocks is the temperature difference rather than the temperature ratio. The latter can be artificially elevated by low upstream temperatures.

Thomsen, M. F.↗
NASA NTRS1987

Criteria of interplanetary parameters causing intense magnetic storms (Dst less than -100nT)

Ten intense storms occurred during the 500 days of August 16, 1978 to December 28, 1979. From the analysis of ISEE-3 field and plasma data, it is found that the interplanetary cause of these storms are long-duration, large and negative IMF B sub Z events, associated with interplanetary duskward-electric fields greater than 5 mV/m. Because a one-to-one relationship was found between these interplanetary events and intense storms, it is suggested that these criteria can, in the future, be used as predictors of intense storms by an interplanetary monitor such as ISEE-3. These B sub Z events are found to occur in association with large amplitudes of the IMF magnitude within two days after the onset of either high-speed solar wind streams or of solar wind density enhancement events, giving important clues to their interplanetary origin. Some obvious possibilities will be discussed. The close proximity of B sub Z events and magnetic storms to the onset of high speed streams or density enhancement events is in sharp contrast to interplanetary Alfven waves and HILDCAA events previously reported, and thus the two interplanetary features corresponding geomagnetic responses can be thought of as being complementary in nature. An examination of opposite polarity B sub Z events with the same criteria show that their occurrence is similar both in number as well as in their relationship to interplanetary disturbances, and that they lead to low levels of geomagnetic activity.

Gonzalez, Walter D.↗
NASA NTRS1987

Observations of polar rain at low and high altitudes

Data from the low-altitude DMSP spacecraft were used to compare polar rain electron intensities, energy spectra, and time variations at low altitudes with concurrent bidirectional electron properties in the magnetotail measured by ISEE 3. The DMSP-measured polar rain phase space densities near the polar cap agreed well with the field-aligned magnetotail lobe electron phase space densities above about 200 eV. Below 100-200 eV, a thermal electron population was observed (by ISEE) in the distant tail which is absent at the DMSP altitudes. The results suggest that the suprathermal tail lobe electrons can move freely along field lines to form polar rain, whereas the thermal electrons are bound to the tailward flowing lobe ion population far down the tail and thus cannot reach the polar cap regions.

Baker, D. N.↗
NASA NTRS1988

A search for lower hybrid drift turbulence in slow shocks

The slow shocks which have been observed in the distant geomagnetic tail by ISEE 3 do not exhibit the large-amplitude magnetic field rotations which are theoretically expected. A possible explanation is that the rotation trailing wave train is resistively damped by strong lower hybrid drift turbulence excited in the shock front. Magnetic wave spectra for three slow shocks are constructed from ISEE 3 dc magnetometer and search coil experiments. The observed magnetic amplitudes near the lower hybrid frequency are below the level at which anomalous resistance would damp the slow shock magnetic rotations.

Coroniti, F. V.↗
NASA NTRS1988

Electrostatic waves stimulated by coherent VLF signals propagating in and near the inner radiation belt

The excitation of electrostatic waves by whistler-mode VLF signals propagating along magnetic-field lines in and near the earth's inner radiation belt is examined on the basis of ISEE-1 observations obtained during July-December 1983. The data are presented in extensive graphs and characterized in detail. The effect is seen in about 60 percent of the ISEE-1 orbits penetrating the belt and for signals originating in both hemispheres, with an electrostatic-wave effective bandwidth roughly proportional to the local magnetic-field strength. These results are interpreted in terms of a theoretical model in which scattering of the VLF waves off magnetic-field-aligned plasma density irregularities is followed by particle pitch-angle scattering and precipitation in the radiation belt; the latter effect could then produce new irregularities via a feedback mechanism.

Bell, T. F.↗
NASA NTRS1988

Directivity of 100 keV-1 MeV photon sources in solar flares

Stereoscopic observations of 0.1-1.0 MeV photon sources in solar flares made with spectrometers aboard the ISEE 3 and PVO (Pioneer Venus Orbiter) have been analyzed to determine the directivity of the photon sources and its possible dependence on photon energy. During the period October 1, 1978-October 31, 1980, a total of 44 solar flares were observed simultaneously by the two instruments. Of these, 39 flares were in full view of both the instruments, the remaining five being partially occulted by the photosphere from the line of sight of at least one instrument. The view angles theta(P) and theta(I) of the PVO and ISEE 3 instruments with respect to the outward solar radius at the flare site varied from one flare to another and were in the range 9-88 deg. The difference between the two view angles varied from 1 deg to 66 deg. The observations of differential photon energy spectra averaged over more than about 16 s do not indicate any systematic directivity. In most flares the directivity of 0.1-1.0 MeV photon sources is found to be less than about 2.5.

Kane, S. R.↗
NASA NTRS1988

Asessment of the boundary layer model of the magnetospheric substorm

Data on energetic protons, thermal electrons, and magnetic field characteristics obtained by the ISEE 3 in the magnetotail at the distance of 80 R(E) from the earth were analyzed. Many features were found that were present in the ISEE 1 and 2 data. In particular, flow directions of the plasma observed at 80 R(E) were found to be quite consistent with the formation of the near-earth neutral line during the expansion phase, giving further support to the near-earth reconnection model of the magnetospheric substorm described by Eastman et al. (1985).

Nishida, A.↗
NASA NTRS1988

Forward-reverse shock pairs associated with transient disturbances in the solar wind at 1 AU

Using color-coded plots of the ISEE-3 solar wind electron data and magnetic field data from ISEE-3 for the period from August 1978 through February 1980, evidence was obtained on two transient disturbances which contained reverse shocks in addition to forward shocks. These disturbances are considered to be associated with coronal mass ejections (CMEs). In the stronger of the two disturbances, the reverse shock was found within the CME and was separated from the forward shock by about 0.2 AU; the pressure between the two shocks was nearly constant. In the weaker disturbance, the reverse shock propagated entirely through the CME, trailing the forward shock by about 0.3-0.4 AU; the pressure between the shocks declined substantially and monotonically. Each disturbance profile can be compared favorably with one of the simple one-dimensional fluid simulations used by Hundhausen (1985) to illustrate the general principles underlying transient disturbance propagation in the solar wind.

Gosling, J. T.↗
NASA NTRS1986

Interplanetary medium data book. Supplement 3: 1977-1985

The updating of the hourly resolution, near-Earth solar wind data compilation is discussed. Data plots and listings are then presented. In the text, the time shifting of ISEE 3 fine-scale magnetic field and and plasma data, using corotation delay, and the normalization of IMP-MIT and ISEE densities and temperatures to equivalent IMP-LANL values, are discussed in detail. The levels of arbitrariness in combining data sets, and of random differences between data sets, are elucidated.

Couzens, David A.↗
NASA NTRS1989

Relaxation of magnetotail plasmas with field-aligned currents

Equilibria of low free energy have been constructed for magnetotail plasmas (Bhattacharjee, 1987). This model is extended to obtain axisymmetric states which have the structure of flux ropes containing field-aligned currents. An interesting feature of these equilibria is a chain of magnetic islands along the tail axis. Theoretical results are compared with observations from ISEE 1 and ISEE 2 on flux ropes (Elphic et al., 1986).

Paranicas, C.↗
NASA NTRS1988

The CDAW-8 substorm event on 28 January 1983 - A detailed global study

A small, isolated substorm with an expansion phase onset at 0739 UT on January 28, 1983 was well observed by ground-based instrumentation as well as by low- and high-altitude spacecraft. Because of the comprehensive nature of the data coverage, including ISEE-3 identification of plasmoid signatures in the deep tail (about 220 earth radii) associated with the substorm, a detailed timeline of the growth, expansion, and recovery phases of the substorm can be provided. The plasma, energetic particle, and field signatures at ISEE-3 are considered within the framework of the near-earth data. Quantitative estimates of substorm energy input and output relationships are made for this case, and the timing and physical dimensions of the deep tail disturbance implied are evaluated by the global observations available.

Baker, D. N.↗