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Geiss, J.

Publications and source records attributed to Geiss, J..

At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Interpretation of 3He variations in the solar wind

The ion composition instrument (ICI) on ISEE-3 observed the isotopes of helium of mass 3 and 4 in the solar wind almost continuously between August 1978 and July 1982. This period included the increase towards the maximum of solar activity cycle 21, the maximum period, and the beginning of the descent towards solar minimum. Observations were made when the solar wind speed was between 300 and 620 km/s. For part of the period evidence for regular interplanetary magnetic sector structure was clear and a number of 3He flares occurred during this time.

Coplan, M. A.↗
NASA NTRS1983

Initial hot plasma composition results from the Dynamics Explorer

Initial observations from the energetic ion composition spectrometer on the DE-1 spacecraft have found mass or charge dependent processes to be operating in the vicinity of an inverted-V event in the auroral acceleration region, above the polar cap ionosphere, and in the mid-altitude dayside cusp. Separate color spectrograms for the different ion species provide a synoptic picture of these processes that can contribute significantly to our understanding of both the solar wind and the ionosphere as sources of energetic magnetospheric ions.

Shelley, E. G.↗
NASA NTRS1982

The polar ionosphere as a source of energetic magnetospheric plasma

Data are presented on an additional ionospheric source composed of ions flowing upward out of the high latitude polar cap with energies in the range of approximately 10 eV to more than about 100 eV. The data are from the energetic ion composition spectrometer (EICS) on board the Dynamics Explorer-1 satellite, launched in August 1981. It is noted that the results presented are not inconsistent with the existence of a polar wind of the type predicted by Axford (1968) since ions with energies less than about 1 eV would have been excluded from the instrument by the generally positive vehicle potential. The results suggest that the polar wind is either modified in mass composition and energy by some as yet unidentified process or is supplemented by a new unrelated source of plasma. What is more, owing to the higher energies, the energetic polar cap ions described here enter the plasma sheet at greater distances than Cowley (1980) estimated and probably represent a significant source of plasma for the maintenance of the plasma sheet.

Shelley, E. G.↗
NASA NTRS1980

Abundance ratios of He-4/2+//He-3/2+/ in the solar wind

The ion composition experiment aboard the Isee 3 spacecraft has been used to measure the He-4(2+)/He-3(2+) ratio in the solar wind. Using 4334 observations made between Aug. 18 and Nov. 24, 1978, and March 24 and Aug. 25, 1979, the average ratio He-4(2+)/He-3(2+) was 2.1 + or - 0.2 x 1000, in agreement with previous foil measurements. Individual observations vary widely from the average and the low He-4(2+)/He-3(2+) ratios occur at times of low He-4(2+) flux.

Ogilvie, K. W.↗
NASA NTRS1980

Observations of the velocity distribution of solar wind ions

Measurements made by the Isee 3 ion composition experiment have been used to determine the kinetic temperatures of 3He(++), 4He(++), 16O(6+), and 16O(7+) in the solar wind. It is found that these temperatures generally obey the relation that T(i)/m(i) equals const, but fluctuations, some of which are caused by dynamical effects in the flow, are observed. The temperature of oxygen sometimes rises above 10 K, which is very strong evidence for heating outside the collisional region of the corona. The tendency toward equal temperatures per nucleon occurs everywhere where collisions are unimportant, suggesting that the temperatures are set up close to the sun rather than elsewhere in the interplanetary medium. The velocity distribution function of helium is observed to be non-Maxwellian, with a pronounced high velocity tail.

Ogilvie, K. W.↗
NASA NTRS1980

On temperature and speed of He/2+/ and O/6+/ ions in the solar wind

First results on fluid parameters of heavy ions in the solar wind from ISEE-1 mass spectrometer data are presented. Temperatures and speeds of the He(2+) and O(6+) ions have been determined for about 150 hours of data in late 1977. It is found that the temperatures are roughly proportional to atomic mass of the ion species. When temperatures are comparatively low, this proportionality does not hold for H(+). At high speeds and high temperatures the minor ions stream somewhat faster than H(+), but there is on average practically no difference between speeds of He(2+) and O(6+).

Schmidt, W. K. H.↗
NASA NTRS1979

Solar and terrestrial noble gases in magnetospheric precipitation

Metal-foil collectors were installed on the external structure of Skylab to entrap precipitating magnetospheric particles. The foils were retrieved, and the entrapped helium, neon, and argon were isotopically analyzed in a high-resolution mass spectrometer. Solar and terrestrial helium and neon and terrestrial argon were detected. As expected, the isotopic composition of neon and argon in the high atmosphere was found to be strongly fractionated. Special techniques were used to estimate the initial particle energy of He-3. The measured He-3 flux is consistent with the assumption that precipitating solar He-3 is the major source of terrestrial He-3.

Lind, D. L.↗
NASA NTRS1979

H/+/ and He/2+/ in the dawnside magnetosheath

Mass and energy analyses of energetic ions in the dawnside magnetosheath have been made by the energetic ion composition experiment on the ISEE-1 spacecraft over the energy range 10 eV/e to 17 keV/e. The significant observations are: the bulk flows of the H(+) and He(2+) components determined from first moments of the distributions averaged over several minutes are equal within the uncertainties of the measurement. The H(+) and He(2+) distributions are similar in that they both show temperature anisotropies with perpendicular temperature not less than parallel temperature; however, the distributions are not well characterized by temperatures derived from second moments. In at least one case high energy tails of both distributions can be characterized by an additional higher temperature component. The major difference between the H(+) and He(2+) distributions is the depletion of the low velocity (in the center of mass frame) part of the He(2+) distributions, relative to the H(+) distributions.

Peterson, W. K.↗
NASA NTRS1978

Ion composition experiment

An investigation using a novel ion mass spectrometer for measuring the ionic composition of the solar wind from the ISEE-C spacecraft is described. The resolution and dynamic range of the instrument are sufficient to be able to resolve up to twelve individual ions or groups of ions. This will permit the solution of a number of fundamental problems related to solar abundances and the formation of the solar wind. The spectrometer is composed of a stigmatic Wien filter and hemispherical electrostatic energy analyzer. The use of curved electric field plates in the filter results in a substantial saving of weight with respect to a conventional filter of the same resolution and angular acceptance. The spectrometer is controlled by a microprocessor based on a special purpose computer which has three modes of operations: full and partial survey modes and a search mode. In the search mode, the instrument locks on to the solar wind. This allows four times the time resolution of the full survey mode and yields a full mass spectrum every 12.6 min.

Coplan, M. A.↗
NASA NTRS1976

A satellite-borne ion mass spectrometer for the energy range 0 to 16 keV

The Ion Composition Experiment (ICE) on GEOS represents the first comprehensive attempt to measure the positive ion composition at high altitudes in the magnetosphere. Due to the heterogeneous nature of the magnetospheric plasma a novel mass spectrometer has been developed to cover the mass per charge range from H-1(+) to beyond Ba-138(+) and the energy per charge range from 0 to 16 keV/e. The ICE consists primarily of a cylindrical electrostatic analyzer followed by a curved analyzer incorporating crossed magnetic and electric fields. This combination has limited angular and energy focusing properties, but it maintains a mass resolution of about 4 over a wide range in energy and mass, sufficient for the objectives of measuring plasmas of both solar and terrestrial origin. High sensitivity and low background should allow measurements of rarer ion constituents down to flux levels of 0.01 ions/sq cm sec ster eV. A sophisticated electronics combined with powerful ground computer and telecommand systems allow for very efficient scanning of the mass-energy space.

Balsiger, H.↗
NASA NTRS1974

Magnetospheric particle composition experiment

Thin foils of aluminum and platinum were mounted on the exterior of the Skylab spacecraft where they were bombarded by particles that penetrate to the 400-km spacecraft altitude, including auroral particles precipitating from the earth magnetosphere. These foils have a high trapping efficiency for both charged and neutral particles above 1 keV and a decreasing but appreciable efficiency below that energy. Some sections of the foils were double layered to obtain an estimate of the energy of the entrapped particles. The foils were retrieved and returned for analysis in an ultrahigh-vacuum mass spectrometer. So far, the noble gas components of the entrapped particles have been analyzed in selected sections of two foils. Helium-4, helium-3, neon-20, and neon-22 have been detected.

Geiss, J.↗
NASA NTRS1972

Auroral helium precipitation.

Application of the metal foil sampling technique, which has been used to measure helium, neon, and argon fluxes in the solar wind, to the problem of measuring the fluxes of these gases in the auroral primary radiation. Aluminum and platinum foils have been flown into two bright auroras and have been recovered. The foils have been analyzed for helium and neon isotopes with a mass spectrometer; so far only He4 has been detected. In the first flight the precipitating flux of He4 with particle energies above about 1 keV was approximately 1,000,000 per sq cm per sec, and the backscattered flux was smaller by about a factor of 10. In the second flight the aurora was less bright, and the He4 fluxes were lower by a factor of about 2. A rough analysis suggests that the mean energy of the incident particles was greater than 3 keV.

Axford, W. I.↗
NASA NTRS1972

Solar-wind composition experiment

The Apollo program techniques for studying elemental and isotopic abundances in the solar wind are described. During Apollo 11, 12, 14 and 15 missions, aluminum foils were deployed on the lunar surface as targets for collecting solar wind ions. The foils were returned to earth, and the implanted solar wind particles were analyzed. The preliminary results showing the helium and neon concentrations are presented.

Geiss, J.↗
NASA NTRS1972

Solar wind rare gas analysis: Trapped solar wind helium and neon in Surveyor 3 material

The He-4 and Ne-20 contents in sections of the Surveyor 3 support strut samples were determined by optical and scanning electron microscopy and are compared to the results of the Apollo solar wind composition (SWC) experiments. The He-4/Ne-20 ratio in the samples from the sunlit side of the strut was approximately 300; the ratios determined in Apollo 12 lunar fines and SWC foil were below 100. The He-4/He-3 ratios were also determined, and the ratio obtained from Surveyor 3 material is higher than those found with Apollo 11 and 12 SWC experiments. The effects of spallation by cosmic rays or solar protons, stripping by cosmic ray or energetic solar alpha particles, recycling of solar wind He and radiogenic Ne, He from terrestrial atmosphere, mass discrimination near the moon, mass dependence of trapping probability, diffusion, and contamination by lunar dust are considered.

Buehler, F.↗
NASA NTRS1972

Elemental and isotopic abundances in the solar wind

The use of collecting foils and lunar material to assay the isotopic composition of the solar wind is reviewed. Arguments are given to show that lunar surface correlated gases are likely to be most useful in studying the history of the solar wind, though the isotopic abundances are thought to give a good approximation to the solar wind composition. The results of the analysis of Surveyor material are also given. The conditions leading to a significant component of the interstellar gas entering the inner solar system are reviewed and suggestions made for experimental searches for this fraction. A critical discussion is given of the different ways in which the basic solar composition could be modified by fractionation taking place between the sun's surface and points of observation such as on the Moon or in interplanetary space. An extended review is made of the relation of isotopic and elemental composition of the interplanetary gas to the dynamic behavior of the solar corona, especially processes leading to fractionation. Lastly, connection is made between the subject of composition, nucleosynthesis and the convective zone of the sun, and processes leading to modification of initial accretion of certain gases on the Earth and Moon.

Geiss, J.↗
NASA NTRS1972

Solar wind composition experiment

The Apollo 16 SWC experiment is a continuation of the earlier experiments; however, an essential change was introduced in the solar wind particle collection technique. Platinum surfaces were incorporated in the collector foil, and use was made of a layer technique for distinguishing particles of different energies and different directions of arrival. The improvements and the expanded scope of the Apollo 16 experiment, relative to the earlier SWC experiments, can be summarized as follows: elimination of possible residual dust contamination by treating the platinum foil sections with dilute hydrofluoric acid before analysis; increased accuracy of solar wind argon abundance; determination of solar wind albedo; and search for helium in the energy range above approximately 40 KeV/nucleon.

Geiss, J.↗