Ultra-sensitive high-precision spectroscopy of a fast molecular ion beam
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Andrew A. Mills↗
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Origin of 'energetic' ions from laser-produced plasmas.
A fast-ion current peak, measured with an ion collector placed in the path of an expanding laser-produced plasma, was identified as carbon, nitrogen, and oxygen contaminants which originated from a tungsten target surface.
Ehler, W.↗
Charged particle modification of ices in the Saturnian and Jovian systems
The modification by ion bombardment of the surfaces of icy objects in the Saturnian and Jovian systems is discussed. Chemical changes in ices are induced by breaking of bonds and by implantation of incident ions. Long-term irradiation by fast ions produces physical changes such as increasing the surface reflectivity and ability to scatter light. On large satellites, molecules which are ejected by ion bombardment are redistributed across the surfaces of large satellites. For small satellites and ring particles bombarded by ions, such as those of Saturn, most or all of the sputtered material is lost to space, forming a neutral torus in the locale of the satellite orbits and rings and supplying ions to the magnetosphere. Noting the existence of such a torus, the sputter erosion and possible stabilization of the E-ring of Saturn is discussed.
Johnson, R. E.↗
Anomalous ion mixing within a Kelvin-Helmholtz vortex in a collisionless plasma
Anomalously fast ion mixing is observed in a hybrid code simulation (particle ions and a massless electron fluid) of the Kelvin-Helmholtz instability in a collisionless plasma. While the traditional view predicts that the ion mixing occurs on a time scale longer than the roll-up time T(v) of the Kelvin-Helmholtz vortex by a factor of (velocity shear scale length)/(ion Larmor radius), the simulation results show that the mixing occurs within a time scale comparable to T(v). It is shown that this fast mixing is due to the scattering of ions by unsteady electromagnetic fields.
Terasawa, T.↗
Fundamental Aspects of Ion Transport in Solid Electrolytes
Solid electrolytes (also termed as superionic solids or fast ion conductors) are characterized by high electrical conductivity, comparable to concentrated liquid electrolytes or even molten salt electrolytes, made possible by rapid transport of ions in the crystalline lattice.
electrochemistry solid state ionics superionic sol↗
Mobilities of uranium and mercury ions in helium
The mobilities of mass-identified U(+) and Hg (+) ions in helium were determined in a drift tube-mass spectrometer. For uranium ions, a reduced mobility value is obtained at 305 K and a standard gas density of 2.69 x 10 to the 19th power/cu cm. The mobility of mercury ions is in agreement with two previous determinations. The effect of fast ion injection in drift mobility measurements is discussed, and a technique to circumvent these problems is described. The results are compared with existing theories of ion mobilities.
Johnsen, R.↗
Quiet-time intensifications along the poleward auroral boundary near midnight
Radar and optical measurements from Sondrestrom are combined with satellite and Goose Bay data in a study of the poleward edge of the nightside auroral oval during a quiet period. The B(sub y) and B(sub z) components of the interplanetary magnetic field were close to zero, and the B(sub x) component was approximately 8 nT for more than 24 hours. On a large scale, the convection and precipitation patterns remained almost constant during this period; on a small scale, however, the conditions were quite dynamic. At 10- to 20-min intervals the arc that marked the poleward auroral boundary intensified, and a new arc appeared poleward of it. About once per hour, stronger intensifications were observed. One such event is examined in detail. The auroral arcs first appeared to dim, and then they brightened, with a factor of 10 increase in E region electron density. At the time of the brightening a new arc formed poleward of all the arcs. The arcs then drifted southward at velocities of approximately 270 m/s. A plasma drift disturbance, characterized by a doubling of the southward velocity and a reversal in the east-west component, propagated westward at 900 m/s through the fields of view of the Sondrestrom and Goose Bay radars. A simultaneous satellite overpass close to the radars revealed the presence of an energetic ion event similar to the 'velocity dispersed ion structures' observed on the Aureol satellite and presumed to be the signature of fast ion beams within the plasma sheet boundary layer. The stronger arc intensification events observed by the Sondrestrom radar are associated with an increase in plasma flow across the boundary between open and closed magnetic field lines. We interpret this increased flow as the ionospheric signature of abrupt, localized increases in the reconnection rate in the midnight sector.
De La Beaujardiere, O.↗
Fast O(sup +) ion flow observed around Venus at low altitudes
The Pioneer Venus Orbiter Neutral Mass Spectrometer (ONMS) has observed fast O(+) ions with an energy exceeding 40 eV in the spacecraft reference frame. The orbit of the spacecraft is nearly polar with periapsis near the equator. The ONMS is mounted at an angle to the spin axis which, in turn, is perpendicular to the ecliptic plane. From the spin modulated data the direction of the ion flow in that plane can be determined. Data from the first 11 diurnal cycles (orbits 1 to 2475) are vector averaged in order to display the general flow pattern. Plots of the averaged data are presented. On the dayside and near the terminators, where fast O(+) is observed near the ionopause, the directions are more or less parallel to the planet's surface with evidence of an asymmetry about the Sun-Venus line. On the nightside below 2000 km and near the equator there is a preferred dawn to dusk direction while at higher altitudes (lower solar zenith angles and higher latitudes) the flow direction is more antisunward. The averaged flux for this time period is 8x10 to the 5th/sq cm/s with a maximum of 5x10 to the 8th.
Kasprzak, W. T.↗
Energetic ion fluxes in the inner coma of Comet P/Halley
The particle phenomenon observed inside the magnetic field-free cavity near the nucleus of Comet P/Halley by the Giotto Ion Mass Spectrometer High-Energy Range Spectrometer sensor is studied. The question of access to the cavity of particles ionized farther out in the coma is addressed. A quantitative model of a mechanism for creating the observed fast-ion fluxes in the cavity is presented.
Eviatar, Aharon↗
Electron velocity space hole modes
In space plasmas the local electron distribution is formed by ballistic motion from different source regions. Since electrons with positive and negative parallel (v-parallel) velocities have different sources and experience different interactions with the large-scale electromagnetic fields, the electron distribution function near v-parallel = 0 should possess considerable structure, including the possibility of velocity space holes, i.e., regions where the phase space density is zero, and sharp discontinuities. A particular hole distribution, which may occur upstream of slow shocks in the distant geomagnetic tail, is shown to support a nonstandard plasma wave mode with frequencies between the ion and electron plasma frequencies and parallel phase speed above the ion, but well below the electron, thermal speed. The hole mode can be destabilized by a positive slope in the low parallel velocity electron distribution, and the growth rate is strongly enhanced if the electron parallel temperature exceeds the perpendicular temperature; the mode can also be excited by a hot, fast ion beam. The hole modes exist only for a narrow range of propagation angles about the magnetic field direction.
Coroniti, Ferdinand V.↗
Some features of the small-scale solar wind fluctuations
We have investigated small-scale variations of the solar wind ion flux measured with Faraday cups onboard the Prognoz-8 satellite. These measurements have a high time resolution of 1.24 seconds for intervals with a duration of several hours and as high as 0.02 seconds for some periods of about 1 hour duration. The main goal of this work is the determination of the quantitative features of fast ion flux fluctuations using mainly spectral analysis but also other methods. We also identify their association with interplanetary plasma parameters. Particularly, it is shown that the slope of the power spectra in the frequency range from 1E-4 to 6E-2 Hz is close to the classical Kolmogorov (-5/3) law. We also discuss some intervals with a very high level of the relative amplitude of flux fluctuations (10-20 percent) which were observed near the Earth's bow shock in the foreshock region. The use of the wavelet method for the long time series allows us to study the temporal evolution of power spectra.
Zastenker, G.↗
The Giotto three-dimensional positive ion analyser
An instrument to measure the three-dimensional energy distribution of positive ions in order to study the interaction between the solar wind and ionized Halley cometary particles was designed. Two sensors measure the distribution from 10 eV to 20 keV once per spacecraft spin and the distribution from 90 eV to 90 keV, with coarse mass discrimination, once every 32 spins. The instrument was turned on September 8, 1985. The performance throughout all testing was nominal. The spacecraft was greater than 10 million km from the earth in the solar wind. The only population identified is the solar wind. The Fast Ion Sensor follows solar wind variations with its autoranging capability. The Implanted Ion Sensor identifies higher mass ions such as O(6+) and O(5+) in the solar wind.
Johnstone, A. D.↗
Spectroscopy with gas targets.
Spectroscopy of fast atoms resulting from fast ion impact with gas targets and electron capture into excited state
Hughes, R. H.↗
University of Florida nuclear pumped laser program
The mechanism of excitation of laser gases by fast ions (triton, proton, or fission fragments) and especially any role UF6 might play in radiative deexcitation of these gases were investigated. Population densities of excited important for laser action were obtained. Nuclear pumped CW-laser systems, especially He-Ne and CO2, were studied using steady state reactors. It was demonstrated that He-Ne lases in a CW-mode with nuclear pumping at both the red and the infrared transition. The infrared transition was observed to be superradiant.
Richard T. Schneider↗
Study of photon emission by electron capture during solar nuclei acceleration, 1: Temperature-dependent cross section for charge changing processes
The study of charge changing cross sections of fast ions colliding with matter provides the fundamental basis for the analysis of the charge states produced in such interactions. Given the high degree of complexity of the phenomena, there is no theoretical treatment able to give a comprehensive description. In fact, the involved processes are very dependent on the basic parameters of the projectile, such as velocity charge state, and atomic number, and on the target parameters, the physical state (molecular, atomic or ionized matter) and density. The target velocity, may have also incidence on the process, through the temperature of the traversed medium. In addition, multiple electron transfer in single collisions intrincates more the phenomena. Though, in simplified cases, such as protons moving through atomic hydrogen, considerable agreement has been obtained between theory and experiments However, in general the available theoretical approaches have only limited validity in restricted regions of the basic parameters. Since most measurements of charge changing cross sections are performed in atomic matter at ambient temperature, models are commonly based on the assumption of targets at rest, however at Astrophysical scales, temperature displays a wide range in atomic and ionized matter. Therefore, due to the lack of experimental data , an attempt is made here to quantify temperature dependent cross sections on basis to somewhat arbitrary, but physically reasonable assumptions.
Perez-Peraza, J.↗
The cyclotron energization through auroral wave experiments (CENTAUR 2B)
The CENTAUR 2B mission, a dual payload program, is in many aspects the same as the previous missions from Cape Perry and Norway in 1985. It was planned that these payloads would be launched from Andoya, Norway, Nov. 1989 from the Universal II launcher. The payloads are identical, but would have been launched at different azimuths as far north and as far west as possible. Particle experiments include the angular resolving energy analyzer (AREA), the fast ion mass spectrometer (FIMS), the spectrographic particle images (SPI), and finally, the differential ion flux probe (DIFP). SwRI was responsible for the scientific payload, which includes the power supplies, the power supply interfacing, the manipulating of the data from the instruments to format it for the telemetry system, all mechanical structure and restraint mechanisms, and the payload subskin. The status of the various components of this program is given.
Winningham, J. D.↗
Observations of energetic ion enhancements and fast neutrals upstream and downstream of Uranus' bow shock by the Voyager 2 spacecraft
Measurements of energetic ions and electrons upstream and downstream from Uranus obtained during the low energy charged particle experiment on Voyager 2 are discussed. The results indicate that energetic ions were present upstream of Uranus' bow shock and that their charcteristics, in terms of anisotropies and energy spectra, are consistent with an Uranian magnetospheric origin and are inconsistent with predictions of in situ acceleration via the Fermi mechanism. An upper limit to the flux of energetic neutrals escaping the magnetosphere is established, and the volume-averaged neutral hydrogen density inside 5 Uranian radii is constrained.
Krimigis, S. M.↗
The Relationship of Ion Beams and Fast Flows in the Plasma Sheet Boundary Layer
We report new findings on the behavior of plasmas in the vicinity of the plasma sheet boundary layer (PSBL). A large geometrical factor detector on WIND (3D plasma experiment) has discovered a unidirectional ion beam streaming in the tailward direction missed by previous observations. This tailward beam is as intense as the earthward streaming beam and it is found just inside the outer edge of the PSBL where earthward streaming beams are observed. The region where this tailward beam is observed includes an isotropic plasma component which is absent in the outer edge where earthward streaming beams are found. When these different distributions are convolved to calculate the velocity moments, fast flows (greater than 400 km/s) result in the earthward direction and much slower flows (less than 200 km/s) in the tailward direction. These new findings are substantially different from previous observations. Thus, the interpretation of fast flows and earthward and counterstreaming ion beams in terms of a neutral line model must be reexamined.
Parks, G. K.↗