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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 109 records · Page 6
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NASA NTRS1973

The electric potential of the lunar surface

Acceleration and detection of the lunar thermal ionosphere in the presence of the lunar electric field yields a value of at least +10 V for the lunar electric potential for solar zenith angles between approximately 20 and 45 deg and in the magnetosheath or solar wind. An enhanced positive ion flux is observed with the ALSEP Suprathermal Ion Detector when a pre-acceleration voltage attains certain values. This enhancement is greater when the moon is in the solar wind as opposed to the magnetosheath.

Fenner, M. A.↗
NASA NTRS1973

Lunar ion energy spectra and surface potential

The acceleration model for lunar ions and the resulting ionosphere dynamics are reviewed briefly. An application is made to lunar atmosphere trapped in the surface fines, and the enhancement in the Ar-40/Ar-36 ratio in samples from the Apennine Front compared to the adjacent mare is calculated to be about 2.0. The predicted lunar ion energy spectra is shown and found to agree well with Suprathermal Ion Detector measurements; from this spectra, the neutral atmosphere scale height can be studied and the neutral atmosphere number density is found to be 100,000 to 300,000 per cu cm at the sunrise and sunset terminators. The lunar surface potential is calculated and is found to be several volts positive over much of the sunlit face of the moon but to go tens of volts negative at the terminator.

Manka, R. H.↗
NASA NTRS1974

Observation of low energy protons in the geomagnetic tail at lunar distances

Three suprathermal ion detectors stationed on the moon were used to detect a region of plasma flowing antisunward along the ordered field lines of the geomagnetic tail, exterior to the plasma sheet. The particle flow displays an integral flux, a bulk velocity, temperatures, and number densities uniquely different from the other particle regimes traversed by the moon. No consistent deviation in the field was found to correspond with the occurrence of the events, which have an angular distribution extending between 50 and 100 deg and a spatial distribution over a wide region in both the Y sub sm and Z sub sm directions. The duration of observable particles varies widely between tail passages, with an apparent correlation between the number of hours of observation and the Kp index averages over these times. It is proposed that these particles may have entered through the cusp region.

Hardy, D. A.↗
NASA NTRS1974

Observation of a driver gas-tangential discontinuity

A complete analysis of an interplanetary disturbance of Nov. 19, 1970 using the Apollo 12-SIDE (Suprathermal Ion Detector Experiment) is presented. The SIDE detectors were pointing at 26.3 degrees from the normal solar-wind direction during the observations. The data were least-squares fitted (using a parabolic hypersurface approximation) to a convected Maxwell-Boltzmann distribution function. The results of the fit combined with two other experiments showed a drastic change in the wind speed (from an steady 352 km/sec down to 219 km/sec), direction, and temperature. Except for a delta-function increase at the onset, the density remained constant. There was a considerable enhancement in the abundance of He and probably of heavier elements. The interplanetary magnetic field exhibited a jump of 21 gamma with a change in latitude from -56 to -76 degrees in solar ecliptic coordinates. It is concluded that the disturbance was due to the driver gas-tangential discontinuity of a solar flare-induced shock wave. The characteristic of the tangential discontinuity fit well with theoretical prediction.

Medrano, R. A.↗
NASA NTRS1975

A new plasma regime in the distant geomagnetic tail

Observations are reported of an extensive region of low-energy plasma particles (LEP) flowing antisunward along the ordered field lines in the lobes of the geomagnetic tail at lunar distances. The flow was detected by three suprathermal ion detectors deployed on the lunar surface during the Apollo 12, 14, and 15 missions. This particle regime is found to be similar to the 'boundary layer' and 'plasma mantle' observed at smaller geocentric distances and to an interior flow region parallel to the magnetopause in the dayside magnetosphere. It is located exterior to the plasma sheet across essentially the entire tail and adjacent to the magnetopause on both the dawn and dusk sides of the magnetosphere. Variations in the integral flux, temperature, and number density are described. It is suggested that this flow and the three similar regimes are simply connected along the inner surface of the magnetopause and are, in fact, the same phenomenon.

Hardy, D. A.↗
NASA NTRS1975

Solar cosmic ray 'square wave' of August 1972

Three Rice University suprathermal ion detector experiments (sides) were deployed on the lunar surface during the Apollo 12, 14, and 15 missions. During the exceptional period of solar activity in August 1972, penetrating particles were observed by all side detectors on the night side of the moon. The penetrating particles are tentatively identified as solar protons with energies (approximately 25 MeV or greater) that were able to penetrate the shielding of all detectors. Of particular interest is the occurrence on August 5 of a 'square wave' flux enhancement of 2-hour duration. Data from a variety of ground-based and space experiments are examined in relation to the square wave. Based on the results of this investigation a model relating the square wave to the flare plasma propagation is proposed. This model hypothesizes transport of energetic particles along a 'corridor' formed by the tangential discontinuity produced by the driver gas of a flare-induced shock wave. This model could explain other frequently observed delayed particle events.

Medrano, R. A.↗
NASA NTRS1975

The plasma sheet boundary and Kp

The paper studies data obtained by the suprathermal ion detector aboard the ATS-1 geostationary satellite in order to establish a relation between the local time occurrence of the plasma sheet at the geostationary orbit (6.6 earth radii) and the Kp index. This relation is then used along with Alfven and Falthammer's (1963) equation for the drift path of an electron moving under the combined influence of a homogeneous electric field and a dipole magnetic field to derive an expression that shows the manner in which the inner boundary of the plasma sheet can be expected to vary radially with Kp along the midnight meridian for Kp less than about 4.

Freeman, J. W.↗
NASA NTRS1975

Dawn-dusk magnetosheath plasma asymmetries at 60 earth radii

A study of data from the Apollo lunar surface suprathermal ion detector experiment (Side) package shows that plasma flow and energy parameters in the dusk magnetosheath are much better correlated with geomagnetic activity than those in the dawn magnetosheath. This result is in agreement with a dawn-dusk asymmetry in the magnetosheath magnetic field and in the bow shock configuration. The different orientations between the mean interplanetary magnetic field direction and the shock normal for the magnetosheaths suggest an explanation of the difference in the plasma parameters on the two sides.

Fenner, M. A.↗
NASA NTRS1974

Apollo scientific experiments data handbook

A brief description of each of the Apollo scientific experiments was described, together with its operational history, the data content and formats, and the availability of the data. The lunar surface experiments described are the passive seismic, active seismic, lunar surface magnetometer, solar wind spectrometer, suprathermal ion detector, heat flow, charged particle, cold cathode gage, lunar geology, laser ranging retroreflector, cosmic ray detector, lunar portable magnetometer, traverse gravimeter, soil mechanics, far UV camera (lunar surface), lunar ejecta and meteorites, surface electrical properties, lunar atmospheric composition, lunar surface gravimeter, lunar seismic profiling, neutron flux, and dust detector. The orbital experiments described are the gamma-ray spectrometer, X-ray fluorescence, alpha-particle spectrometer, S-band transponder, mass spectrometer, far UV spectrometer, bistatic radar, IR scanning radiometer, particle shadows, magnetometer, lunar sounder, and laser altimeter. A brief listing of the mapping products available and information on the sample program were also included.

Eichelman, W. F.↗
NASA NTRS1977

Direct measurement of the plasma screening length and surface potential near the lunar terminator

Direct measurement of the lunar dayside surface potential and screening length has been made by the suprathermal ion detector experiment (Side) near the terminator. In a region 20-30 deg from the terminator at the Apollo 14 and 15 sites the surface potential is found to be approximately 50 V negative, and the screening length to be about 1 km. This value of the screening length is more than 2 orders of magnitude greater than the solar wind 'Debye' length. The strong negative surface potential in this region may be due to enhanced temperature and density of the solar wind plasma.

Benson, J.↗
NASA NTRS1980

Half-life of Si-32 from tandem-accelerator mass spectrometry

A newly developed mass-spectrometry technique employing a tandem Van de Graaff accelerator together with a special beam-transport system and heavy-ion detector has been used to determine the half-life of Si-32. The result obtained, 108 plus or minus 18 yr, disagrees with the accepted value of 330 plus or minus 40 yr. The implications of the new half-life of Si-32, which is used for dating studies, are discussed.

Elmore, D.↗
NASA NTRS1980

Observation of the plasma boundary layer at lunar distances - Direct injection of plasma into the plasma sheet

The paper presents observational evidence from the Apollo suprathermal ion detector experiments that the injection of magnetosheath particles at the low-latitude magnetopause operates at lunar distances as well. An interface between the magnetosheath and the plasma sheet, termed the plasma sheet boundary layer (PSBL), is identified and believed to be the extension of the magnetospheric boundary layer (also called the plasma boundary layer) observed on the dayside. Using measurements of the PSBL's thickness, magnetic field, and plasma velocity the average electric potential drop across the PSBL is estimated at 4.2 kV and compared with the potential drop which is needed to insure that the magnetopause is an equipotential for a closed magnetosphere. It was concluded though that the magnetosphere is open since this drop is much larger than 4.2 kV.

Sanders, G. D.↗
NASA NTRS1981

A two-temperature plasma distribution in the magnetosheath at lunar distances

Least squares Maxwellian fits have been made to data from the Apollo 15 suprathermal ion detector experiment (SIDE) during the moon's passage through the dusk magnetosheath. It is found that the data are best fit by superimposing two co-moving proton populations whose temperatures differ radically: kT roughly 10 eV and kT roughly 100 eV. This two-temperature distribution cannot be explained by alpha particles. The higher temperature population is typical of that expected for the fully shocked magnetosheath at lunar distances. The colder distribution could arise from cold plasma from within the magnetosphere brought up to magnetosheath flow speeds, but it is more probably due to unshocked solar wind.

Sanders, G. D.↗
NASA NTRS1981

Nighttime observations of 0.2- to 26-keV electrons in the South Atlantic anomaly made by Atmosphere Explorer C

Atmosphere Explorer C satellite observations have determined that the flux of low energy ions in the South Atlantic Anomaly is much smaller than that of electrons, allowing the satellite's low-energy ion detector to monitor the high-energy background and correct the low-energy electron detector accordingly. It is shown that the electron spectra can be represented by a power law in the range 0.2-26.0 keV, with the spectral index close to -1.0, and that the mean energy flux carried by electrons in the middle of the anomaly is about 0.003 erg/sq cm/sec and may reach 5 times this value. Maps of the downward energy flux are included.

Gledhill, J. A.↗
NASA NTRS1984

Helium ionization detection apparatus

In a gas chromatograph apparatus comprising a gas supply (He carrier gas), a sample injection apparatus, a chromatograph column, a He ion detector, and connecting tubes, a foreign gas (other than He) injection apparatus is installed between the sample injection apparatus and the detector. Mixing of the sample gas and foreign gas takes place readily, the sample gas is always maintained at a stable concentrator range, and accurate measurements are possible, especially at low sample gas concentrations.

Nagai, R.↗
NASA NTRS1985

Atmosphere monitoring requirements

Atmospheric monitoring needs and requirements associated with the use of the Mass Spectrometer Electro-Optical Ion Detector for space stations contamination studies are discussed. Instrument performance requirements and design specifications are examined. A general overview is presented of the types of chemical contaminants found in spacecraft environments.

Ruecker, M.↗
NASA NTRS1986

Electrometer Amplifier With Overload Protection

Circuit features low noise, input offset, and high linearity. Input preamplifier includes input-overload protection and nulling circuit to subtract dc offset from output. Prototype dc amplifier designed for use with ion detector has features desirable in general laboratory and field instrumentation.

Woeller, F. H.↗
NASA NTRS1987

Intercomparison among plasma wake models for plasmaspheric and ionospheric conditions

The angular distributions of ions in the wake of a body moving through a space plasma computed from three different models are compared in order to investigate wake current depletion ratios under conditions simulating the topside ionosphere and plasmasphere. Results demonstrate the importance of taking into account the thermal flux at low Mach numbers and the angular acceptance of ion detectors in making theory-experiment comparisons. For all models considered, gradients in the angular variations of the fluxes are shown to be steeper near the wake-ambient interface than closer to the maximum rarefaction region.

Samir, U.↗