ACE-SWICS In Situ Plasma Composition of Fragmented Comet 73P/Schwassmann-Wachmann 3

NASA Astrophysics Data System (ADS)

Gilbert, J. A.; Lepri, S. T.; Rubin, M.; Zurbuchen, T.

2013-12-01

The interiors of comets contain some of the most pristine material in the solar system. Comet 73P/Schwassmann-Wachmann 3, discovered in 1930 with a double nucleus, is a Jupiter-family comet with a 5.34-year period. This comet split into 5 fragments in 1995 and disintegrated into nearly 70 pieces in 2006. In May and June of 2006, recently ionized cometary particles originating from some of these fragments were collected with the ACE-SWICS sensor. Due to a combination of the close proximity of the fragments passing between ACE-SWICS and the Sun, and the instrument characteristics, unique measurements regarding the charge state composition and the elemental abundances of both cometary and heliospheric plasma were made during this time. The cometary material released from some of these fragments can be identified by the concentrations of water-group pick-up ions having a mass-per-charge of 16-18 amu/e. With a focus on Helium, Carbon, and water-group ions, we present an analysis of the cometary plasma. Charge state ratios of C+/O+ fall below 0.1 during detection of comet fragment plasma, and there is a clear increase in He+ during fragment crossings. The C/O ratio and He charge states are used to provide constraints on the activity of the cometary fragments and also the spatial distribution of the extended and ionized cometary tail.

In Situ Plasma Measurements of Fragmented Comet 73P Schwassmann-Wachmann 3

NASA Astrophysics Data System (ADS)

Gilbert, J. A.; Lepri, S. T.; Rubin, M.; Combi, M.; Zurbuchen, T. H.

2015-12-01

The interiors of comets contain some of the most pristine material in the solar system. Comet 73P/Schwassmann-Wachmann 3, discovered in 1930, is a Jupiter-family comet with a 5.34-year period. This comet split into 5 fragments in 1995 and disintegrated into nearly 70 major pieces in 2006. In 2006 May and June, recently ionized cometary particles originating from fragments including and surrounding some of these major objects were collected with the ACE/SWICS and Wind/STICS sensors. Due to a combination of the instrument characteristics and the close proximity of the fragments passing between those spacecraft and the Sun, unique measurements regarding the charge state composition and the elemental abundances of both cometary and heliospheric plasma were made during that time. The cometary material released from some of these fragments can be identified by the concentrations of water-group pickup ions having a mass-per-charge ratio of 16-18 amu e-1, indicating that while these fragments are small, they are still actively sublimating. We present an analysis of cometary composition, spatial distribution, and heliospheric interactions, with a focus on helium, C+/O+, and water-group ions.

IN SITU PLASMA MEASUREMENTS OF FRAGMENTED COMET 73P SCHWASSMANN–WACHMANN 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gilbert, J. A.; Lepri, S. T.; Combi, M.

2015-12-10

The interiors of comets contain some of the most pristine material in the solar system. Comet 73P/Schwassmann–Wachmann 3, discovered in 1930, is a Jupiter-family comet with a 5.34-year period. This comet split into 5 fragments in 1995 and disintegrated into nearly 70 major pieces in 2006. In 2006 May and June, recently ionized cometary particles originating from fragments including and surrounding some of these major objects were collected with the ACE/SWICS and Wind/STICS sensors. Due to a combination of the instrument characteristics and the close proximity of the fragments passing between those spacecraft and the Sun, unique measurements regarding themore » charge state composition and the elemental abundances of both cometary and heliospheric plasma were made during that time. The cometary material released from some of these fragments can be identified by the concentrations of water-group pickup ions having a mass-per-charge ratio of 16–18 amu e{sup −1}, indicating that while these fragments are small, they are still actively sublimating. We present an analysis of cometary composition, spatial distribution, and heliospheric interactions, with a focus on helium, C{sup +}/O{sup +}, and water-group ions.« less

Bulk properties and velocity distributions of water group ions at Comet Halley - Giotto measurements

NASA Astrophysics Data System (ADS)

Coates, A. J.; Wilken, B.; Johnstone, A. D.; Jockers, K.; Glassmeier, K.-H.; Huddleston, D. E.

1990-07-01

In the region upstream of Comet Halley, pickup heavy ions of cometary origin were directly observed by the implanted ion spectrometer on Giotto. Diffusion of this population in pitch angle and in energy, during the approach to the comet and on the outbound leg is discussed. The two data sets are compared and qualitative ideas on scattering timescales are inferred. In addition the bulk parameters of these distributions have been computed and a comparison of the observed speed in the solar wind frame and the observed density with expectations is presented. Pitch angle scattering occurs more slowly than expected with filled shells appearing at 2,500,000 km, and significant energy diffusion does not occur until the bow shock region. Also the shell distributions downstream of the shock flow at the bispherical bulk speed (related to the Alfven speed) along the magnetic field with respect to the solar wind in accordance with conservation of energy between the pickup ions and the wave turbulence.

The solar corona as probed by comet Lovejoy (C/2011 W3)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raymond, J. C.; McCauley, P. I.; Cranmer, S. R.

2014-06-20

Extreme-ultraviolet images of Comet Lovejoy (C/2011 W3) from the Atmospheric Imaging Assembly show striations related to the magnetic field structure in both open and closed magnetic regions. The brightness contrast implies coronal density contrasts of at least a factor of six between neighboring flux tubes over scales of a few thousand kilometers. These density structures imply variations in the Alfvén speed on a similar scale. They will drastically affect the propagation and dissipation of Alfvén waves, and that should be taken into account in models of coronal heating and solar wind acceleration. In each striation, the cometary emission moves alongmore » the magnetic field and broadens with time. The speed and the rate of broadening are related to the parallel and perpendicular components of the velocities of the cometary neutrals when they become ionized. We use a magnetohydrodynamic model of the coronal magnetic field and the theory of pickup ions to compare the measurements with theoretical predictions, in particular with the energy lost to Alfvén waves as the cometary ions isotropize.« less

Interaction of the solar wind with comets: a Rosetta perspective

NASA Astrophysics Data System (ADS)

Glassmeier, Karl-Heinz

2017-05-01

The Rosetta mission provides an unprecedented possibility to study the interaction of comets with the solar wind. As the spacecraft accompanies comet 67P/Churyumov-Gerasimenko from its very low-activity stage through its perihelion phase, the physics of mass loading is witnessed for various activity levels of the nucleus. While observations at other comets provided snapshots of the interaction region and its various plasma boundaries, Rosetta observations allow a detailed study of the temporal evolution of the innermost cometary magnetosphere. Owing to the short passage time of the solar wind through the interaction region, plasma instabilities such as ring-beam and non-gyrotropic instabilities are of less importance during the early life of the magnetosphere. Large-amplitude ultra-low-frequency (ULF) waves, the `singing' of the comet, is probably due to a modified ion Weibel instability. This instability drives a cross-field current of implanted cometary ions unstable. The initial pick-up of these ions causes a major deflection of the solar wind protons. Proton deflection, cross-field current and the instability induce a threefold structure of the innermost interaction region with the characteristic Mach cone and Whistler wings as stationary interaction signatures as well as the ULF waves representing the dynamic aspect of the interaction. This article is part of the themed issue 'Cometary science after Rosetta'.

Observation of Magnetic Waves Excited by Newborn Interstellar Pickup He+ Observed by the Voyager 2 Spacecraft at 30 au

DOE Office of Scientific and Technical Information (OSTI.GOV)

Argall, Matthew R.; Hollick, Sophia J.; Pine, Zackary B., E-mail: Matthew.Argall@unh.edu, E-mail: sjhollick@hotmail.com, E-mail: zbpine@gmail.com

We report two observations of magnetic waves due to He{sup +} pickup ions observed by the Voyager 2 spacecraft in mid-1989 to demonstrate that such waves occur as far out as ∼30 au from the Sun. The observations are sufficiently far from planets, interplanetary shocks, and other possible sources of energetic particles to make newborn interstellar He{sup +} the only likely explanation for the source of the waves. Additionally, the low-frequency waves that might be expected for a variety of cometary pickup species are not seen. The events studied here were picked from a preliminary list of ∼300 events thatmore » were discovered based on polarization signatures in daily spectrograms of the magnetic field between 1977 and 1990. Analysis of those observations is ongoing. We present an analysis of these two observations using the same techniques we have employed for recently reported observations closer to the Sun.« less

Interaction of the solar wind with comets: a Rosetta perspective

PubMed Central

2017-01-01

The Rosetta mission provides an unprecedented possibility to study the interaction of comets with the solar wind. As the spacecraft accompanies comet 67P/Churyumov–Gerasimenko from its very low-activity stage through its perihelion phase, the physics of mass loading is witnessed for various activity levels of the nucleus. While observations at other comets provided snapshots of the interaction region and its various plasma boundaries, Rosetta observations allow a detailed study of the temporal evolution of the innermost cometary magnetosphere. Owing to the short passage time of the solar wind through the interaction region, plasma instabilities such as ring--beam and non-gyrotropic instabilities are of less importance during the early life of the magnetosphere. Large-amplitude ultra-low-frequency (ULF) waves, the ‘singing’ of the comet, is probably due to a modified ion Weibel instability. This instability drives a cross-field current of implanted cometary ions unstable. The initial pick-up of these ions causes a major deflection of the solar wind protons. Proton deflection, cross-field current and the instability induce a threefold structure of the innermost interaction region with the characteristic Mach cone and Whistler wings as stationary interaction signatures as well as the ULF waves representing the dynamic aspect of the interaction. This article is part of the themed issue ‘Cometary science after Rosetta’. PMID:28554976

Ion cyclotron waves near comet C/2013 A1 (Siding Spring) and Mars

NASA Astrophysics Data System (ADS)

Crary, F. J.; Dols, V. J.; Connerney, J. E. P.; Espley, J. R.

2014-12-01

On October 19, 2014, comet C/2013 A1 (Siding Spring) passed approximately 135,000 km from Mars. Previously,we predicted the amplitude of ion cyclotron waves which might be observed during the Siding Spring encounter. Ioncyclotron waves have been observed both in the vicinity of comets and of Mars. These waves are generated by theionization of neutrals in the flowing solar wind, which produces an unstable ring-beam velocity distribution. We estimated that, for a production rate of 2x1028 s-1, ion cyclotron wave with amplitudes over 0.1 nT would be present within ‡5 hours (1.2 million km) of closest approach. We will compare the actual observations made by the MAVEN spacecraft with these predictions. The spacecraft was close to or downstream of the martian bow shock, which complicates the interpretation of the data. Taking thisinto account, we will describe the observations and their implications for wave activity and cometary neutral production. We also present updated hybrid simulations of ion cyclotron wave generation. The simulations use our best estimate of solar wind conditions at the time of the encounter and a variable injection of 18 AMU pickup ions, at a rates consistent a model of the cometary neutrals.

Relationship between wave energy and free energy from pickup ions in the Comet Halley environment

NASA Technical Reports Server (NTRS)

Huddleston, D. E.; Johnstone, A. D.

1992-01-01

The free energy available from the implanted heavy ion population at Comet Halley is calculated by assuming that the initial unstable velocity space ring distribution of the ions evolves toward a bispherical shell. Ultimately this free energy adds to the turbulence in the solar wind. Upstream and downstream free energies are obtained separately for the conditions observed along the Giotto spacecraft trajectory. The results indicate that the waves are mostly upstream propagating in the solar wind frame. The total free energy density always exceeds the measured wave energy density because, as expected in the nonlinear process of ion scattering, the available energy is not all immediately released. An estimate of the amount which has been released can be obtained from the measured oxygen ion distributions and again it exceeds that observed. The theoretical analysis is extended to calculate the k spectrum of the cometary-ion-generated turbulence.

Generalized Jeans' Escape of Pick-Up Ions in Quasi-Linear Relaxation

NASA Technical Reports Server (NTRS)

Moore, T. E.; Khazanov, G. V.

2011-01-01

Jeans escape is a well-validated formulation of upper atmospheric escape that we have generalized to estimate plasma escape from ionospheres. It involves the computation of the parts of particle velocity space that are unbound by the gravitational potential at the exobase, followed by a calculation of the flux carried by such unbound particles as they escape from the potential well. To generalize this approach for ions, we superposed an electrostatic ambipolar potential and a centrifugal potential, for motions across and along a divergent magnetic field. We then considered how the presence of superthermal electrons, produced by precipitating auroral primary electrons, controls the ambipolar potential. We also showed that the centrifugal potential plays a small role in controlling the mass escape flux from the terrestrial ionosphere. We then applied the transverse ion velocity distribution produced when ions, picked up by supersonic (i.e., auroral) ionospheric convection, relax via quasi-linear diffusion, as estimated for cometary comas [1]. The results provide a theoretical basis for observed ion escape response to electromagnetic and kinetic energy sources. They also suggest that super-sonic but sub-Alfvenic flow, with ion pick-up, is a unique and important regime of ion-neutral coupling, in which plasma wave-particle interactions are driven by ion-neutral collisions at densities for which the collision frequency falls near or below the gyro-frequency. As another possible illustration of this process, the heliopause ribbon discovered by the IBEX mission involves interactions between the solar wind ions and the interstellar neutral gas, in a regime that may be analogous [2].

Early Evolution of Comet 67P Studied with the RPC-LAP onboard Rosetta

NASA Astrophysics Data System (ADS)

Miloch, W. J.; Yang, L.; Paulsson, J. J.; Wedlund, C. S.; Odelstad, E.; Edberg, N. J. T.; Koenders, C.; Eriksson, A.

2016-12-01

In-situ measurements within the Rosetta mission allow for studies of the cometary environment at different stages of cometary evolution. The Rosetta Plasma Consortium (RPC) is a set of five instruments on board the spacecraft that specialise in the measurements of plasma environment of comet 67P. One of the instruments is RPC-LAP, which consists of two Langmuir Probes and can measure the density, temperature, and flow speed of the plasma in the vicinity of the comet. At the early stage of the Rosetta mission, when the spacecraft is far from the nucleus of comet 67P, the ion part of the current-voltage characteristics of RPC-LAP1 is dominated by the photoemission current, which surpasses the currents from the dilute solar wind plasma. As Rosetta starts orbiting around the nucleus in September 2014, LAP1 picks up signatures of local plasma density enhancements corresponding to variations of water-group ions observed in the vicinity of the comet. With the help of current-voltage characteristics and the spacecraft potential, we identify and characterise in space and time the entering of this coma-dominated, high-density plasma region. This high-density region is observed at the northern hemisphere of the comet during early activity. The transition manifests as a steep gradient in the density with respect to the distance to the comet nucleus. We discuss these RPC-LAP results together with the corresponding measurements by other instruments to provide a comprehensive picture of the transition. We show that the early cometary plasma can be seen as composed of two distinct regions: an outer region characterised by solar wind plasma and small quantities of pickup ions, and an inner region with enhanced plasma densities.

Cometary MHD and chemistry

NASA Technical Reports Server (NTRS)

Wegmann, R.; Schmidt, H. U.; Huebner, W. F.; Boice, D. C.

1987-01-01

An MHD and chemical comet-coma model was developed, applying the computer program of Huebner (1985) for the detailed chemical evolution of a spherically expanding coma and the program of Schmidt and Wegman (1982) and Wegman (1987) for the MHD flow of plasma and magnetic field in a comet to the Giotto-mission data on the ion abundances measured by the HIS ion mass spectrometer. The physics and chemistry of the coma are modeled in great detail, including photoprocesses, gas-phase chemical kinetics, energy balance with a separate electron temperature, multifluid hydrodynamics with a transition to free molecular flow, fast-streaming atomic and molecular hydrogen, counter and cross streaming of the ionized species relative to the neutral species in the coma-solar wind interaction region with momentum exchange by elastic collisions, mass-loading through ion pick-up, and Lorentz forces of the advected magnetic field. The results, both inside and outside of the contact surface, are discussed and compared with the relevant HIS ion mass spectra.

The ion population between 1300 km and 230000 km in the coma of comet P/Halley

NASA Technical Reports Server (NTRS)

Altwegg, K.; Balsiger, H.; Geiss, J.; Goldstein, R.; Ip, W. -H.; Meier, A.; Neugebauer, M.; Rosenbauer, H.; Shelley, E.

1993-01-01

During the encounter of the spacecraft Giotto with Comet Halley the two sensors of the ion mass spectrometer (IMS), high energy range spectrometer (HERS) and high intensity spectrometer (HIS), measured the mass and the three-dimensional velocity distributions of cometary ions. HIS looked mainly at the cold, slow part of the distribution close to the nucleus, HERS at the more energetic pick-up ions further out. After a thorough recalibration of the HIS flight spare unit and an extensive data analysis we present here continuous ion density-, composition-, velocity-, and temperature profiles for the water group ion (mass range 16-19 amu/e) along Giotto's inbound trajectory from 230,000 to 1300 km from the comet nucleus. The two sensors are in very good agreement in the region where their measurements overlap thus giving an excellent data base for the discussion of theoretical comet models. The most prominent feature where models and observations disagree is the so called pile up region between 8000 and 15,000 km from the nucleus.

High resolution integral-field spectroscopy of gas and ion distributions in the coma of Comet C/2012 S1 ISON

NASA Astrophysics Data System (ADS)

Schmidt, Carl

2016-02-01

Neutral and ion species in cometary comae exhibit significant differences in their spatial distributions. These distributions reflect the combined effects of sublimation, ion pickup, collisions, solar radiation pressure, photolysis scale lengths of any parent molecules, and photolysis of the species of interest. An image-slicer spectrograph (R ∼ 20,000) is used here to measure C2, NH2, Na, and H2O+ emission lines in Comet C/2012 S1 ISON's coma within a narrow spectral window spanning 5868-5926 Å. These species are mapped over a 1.6 × 2.7 arcmin field made up of 240 individual spectra. While prior cometary observations have found that peak column densities of these species appear either sunward or anti-sunward, ISON's coma was elongated several thousand kilometers along an axis perpendicular to its motion and the sunward vector. The peak brightness of each species was located within 5000 km of the dusty continuum concentration. ISON's water ion tail appeared distinctly broader than the neutral Na tail and no evidence is seen for an extended source of Na by dissociative recombination of a molecular ion. The Na D2/D1 ratio in the head is 1.49 ± 0.06 despite being optically thin, increasing to 1.93 ± 0.07 in the tail. The dust distribution falls off less steeply than the canonical inverse with distance from the nucleus and C2 and NH2 scale lengths indicate an extended source, possibly due to nucleus fragmentation.

Hybrid Simulations of Pickup Ions and Ion Cyclotron Waves at Enceladus

NASA Astrophysics Data System (ADS)

Cowee, M.; Wei, H.; Tokar, R. L.

2014-12-01

Saturn's moon Enceladus releases tens of kilograms per second of water-group neutrals from its southern plumes. These neutrals are ionized and accelerated by the background co-rotation electric field, producing a local population of pickup ions with a ring distribution in velocity space. This velocity space distribution is highly unstable to the growth of electromagnetic ion cyclotron waves whose amplitudes are generally related to the pickup ion production rate, the mass of the pickup ion, the pickup velocity, and the degree of damping by the background plasma. Observations from the Cassini spacecraft show the amplitudes of the waves generally increase with distance within 2 Enceladus radii of the Moon, consistent with an increasing density of pickup ion source, but then decrease right at the Moon, consistent with zero pickup velocity in the stagnating plasma flow. In order to interpret the observed wave amplitudes in terms of ion production rates at Enceladus, we carry out self-consistent hybrid simulations of the growth of ion cyclotron waves from pickup ions to determine the relationship between wave amplitude and background plasma and ion pickup conditions.

Transport of Helium Pickup Ions within the Focusing Cone: Reconciling STEREO Observations with IBEX

NASA Astrophysics Data System (ADS)

Quinn, P. R.; Schwadron, N. A.; Möbius, E.

2016-06-01

Recent observations of the pickup helium focusing cone by STEREO/Plasma and Suprathermal Ion Composition indicate an inflow longitude of the interstellar wind that differs from the observations of IBEX by 1\\buildrel{\\circ}\\over{.} 8+/- 2\\buildrel{\\circ}\\over{.} 4. It has been under debate whether the transport of helium pickup ions with an anisotropic velocity distribution is the cause of this difference. If so, the roughly field-aligned pickup ion streaming relative to the solar wind should create a shift in the pickup ion density relative to the focusing cone. A large pickup ion streaming depends on the size of the mean free path. Therefore, the observed longitudinal shift in the pickup ion density relative to the neutral focusing cone may carry fundamental information about the mean free path experienced by pickup ions inside 1 au. We test this hypothesis using the Energetic Particle Radiation Environment Module (EPREM) model by simulating the transport of helium pickup ions within the focusing cone finding a mean free path of {λ }\\parallel =0.19+0.29(-0.19) au. We calculate the average azimuthal velocity of pickup ions and find that the anisotropic distribution reaches ˜8% of the solar wind speed. Lastly, we isolate transport effects within EPREM, finding that pitch-angle scattering, adiabatic focusing, perpendicular diffusion, and particle drift contribute to shifting the focusing cone 20.00%, 69.43%, 10.56%, and \\lt 0.01 % , respectively. Thus we show with the EPREM model that the transport of pickup ions does indeed shift the peak of the focusing cone relative to the progenitor neutral atoms and this shift provides fundamental information on the scattering of pickup ions inside 1 au.

Lunar Neutral Exposphere Properties from Pickup Ion Analysis

NASA Technical Reports Server (NTRS)

Hartle, R. E.; Sarantos, M.; Killen, R.; Sittler, E. C. Jr.; Halekas, J.; Yokota, S.; Saito, Y.

2009-01-01

Composition and structure of neutral constituents in the lunar exosphere can be determined through measurements of phase space distributions of pickup ions borne from the exosphere [1]. An essential point made in an early study [ 1 ] and inferred by recent pickup ion measurements [2, 3] is that much lower neutral exosphere densities can be derived from ion mass spectrometer measurements of pickup ions than can be determined by conventional neutral mass spectrometers or remote sensing instruments. One approach for deriving properties of neutral exospheric source gasses is to first compare observed ion spectra with pickup ion model phase space distributions. Neutral exosphere properties are then inferred by adjusting exosphere model parameters to obtain the best fit between the resulting model pickup ion distributions and the observed ion spectra. Adopting this path, we obtain ion distributions from a new general pickup ion model, an extension of a simpler analytic description obtained from the Vlasov equation with an ion source [4]. In turn, the ion source is formed from a three-dimensional exospheric density distribution, which can range from the classical Chamberlain type distribution to one with variable exobase temperatures and nonthermal constituents as well as those empirically derived. The initial stage of this approach uses the Moon's known neutral He and Na exospheres to deriv e He+ and Na+ pickup ion exospheres, including their phase space distributions, densities and fluxes. The neutral exospheres used are those based on existing models and remote sensing studies. As mentioned, future ion measurements can be used to constrain the pickup ion model and subsequently improve the neutral exosphere descriptions. The pickup ion model is also used to estimate the exosphere sources of recently observed pickup ions on KAGUYA [3]. Future missions carrying ion spectrometers (e.g., ARTEMIS) will be able to study the lunar neutral exosphere with great sensitivity, yielding the necessary ion velocity spectra needed to further analysis of parent neutral exosphere properties.

Small is different: RPC observations of a small scale comet interacting with the solar wind

NASA Astrophysics Data System (ADS)

Nilsson, Hans; Burch, James L.; Carr, Christopher M.; Eriksson, Anders I.; Glassmeier, Karl-Heinz; Henri, Pierre; Rosetta Plasma Consortium Team

2016-10-01

Rosetta followed comet 67P from low activity at more than 3 AU heliocentric distance to peak activity at perihelion and then out again. We study the evolution of the dynamic plasma environment using data from the Rosetta Plasma Consortium (RPC). Observations of cometary plasma began in August 2014, at a distance of 100 km from the comet nucleus and at 3.6 AU from the Sun. As the comet approached the Sun, outgassing from the comet increased, as did the density of the cometary plasma. Measurements showed a highly heterogeneous cold ion environment, permeated by the solar wind. The solar wind was deflected due to the mass loading from newly added cometary plasma, with no discernible slowing down. The magnetic field magnitude increased significantly above the background level, and strong low frequency waves were observed in the magnetic field, a.k.a. the "singing comet". Electron temperatures were high, leading to a frequently strongly negative spacecraft potential. In mid to late April 2015 the solar wind started to disappear from the observation region. This was associated with a solar wind deflection reaching nearly 180°, indicating that mass loading became efficient enough to form a solar wind-free region. Accelerated water ions, moving mainly in the anti-sunward direction, kept being observed also after the solar wind disappearance. Plasma boundaries began to form and a collisionopause was tentatively identified in the ion and electron data. At the time around perihelion, a diamagnetic cavity was also observed, at a surprisingly large distance from the comet. In late 2016 the solar wind re-appeared at the location of Rosetta, allowing for studies of asymmetry of the comet ion environment with respect to perihelion. A nightside excursion allowed us to get a glimpse of the electrodynamics of the innermost part of the plasma tail. Most of these phenomena are dependent on the small-scale physics of comet 67P, since for most of the Rosetta mission the solar wind - comet atmosphere interaction region is smaller than the pickup ion gyroradius in the undisturbed solar wind.

Interstellar Pickup Ion Observations to 38 au

NASA Astrophysics Data System (ADS)

McComas, D. J.; Zirnstein, E. J.; Bzowski, M.; Elliott, H. A.; Randol, B.; Schwadron, N. A.; Sokół, J. M.; Szalay, J. R.; Olkin, C.; Spencer, J.; Stern, A.; Weaver, H.

2017-11-01

We provide the first direct observations of interstellar H+ and He+ pickup ions in the solar wind from 22 to 38 au. We use the Vasyliunas and Siscoe model functional form to quantify the pickup ion distributions, and while the fit parameters generally lie outside their physically expected ranges, this form allows fits that quantify variations in the pickup H+ properties with distance. By ˜20 au, the pickup ions already provide the dominant internal pressure in the solar wind. We determine the radial trends and extrapolate them to the termination shock at ˜90 au, where the pickup H+ to core solar wind density reaches ˜0.14. The pickup H+ temperature and thermal pressure increase from 22 to 38 au, indicating additional heating of the pickup ions. This produces very large extrapolated ratios of pickup H+ to solar wind temperature and pressure, and an extrapolated ratio of the pickup ion pressure to the solar wind dynamic pressure at the termination shock of ˜0.16. Such a large ratio has profound implications for moderating the termination shock and the overall outer heliospheric interaction. We also identify suprathermal tails in the H+ spectra and complex features in the He+ spectra, likely indicating variations in the pickup ion history and processing. Finally, we discover enhancements in both H+ and He+ populations just below their cutoff energies, which may be associated with enhanced local pickup. This study serves to document the release and serves as a citable reference of these pickup ion data for broad community use and analysis.

Potential Role of the Mirror and Ion Bernstein Instabilities on the Pickup Ion Dynamics in the Outer Heliosheath: Linear Theory and Hybrid Simulations

NASA Astrophysics Data System (ADS)

Min, K.; Liu, K.; Gary, S. P.

2017-12-01

The main challenge of the secondary ENA mechanism, a theory put forth to explain the IBEX ENA ribbon, is maintaining the stability of the pickup ion velocity distribution before the pickup ions in the outer heliosheath go through two consecutive charge exchanges. The Alfvén/ion-cyclotron instability, which has its maximum growth at propagation parallel to Bo, the background magnetic field, is believed to be the main agent leading to rapid isotropization of the pickup ions. However, recent studies found that this instability can be suppressed when parallel temperatures of the background plasma and the pickup ion ring distribution are comparable, allowing the pickup ion distribution to remain stable for a long period. This paper demonstrates that a pickup ion ring distribution can also drive the mirror and ion Bernstein instabilities which lead to growing modes at propagation oblique to Bo. For idealized proton-electron plasmas where relatively cool background electron and proton populations are represented by isotropic Maxwellian distributions and tenuous (1%) pickup protons are represented by a Maxwellian-ring distribution (assuming a 90˚ pickup angle), linear Vlasov theory predicts unstable mirror and ion Bernstein modes with growth rates comparable to or exceeding that of the Alfvén-cyclotron instability. According to quasilinear theory, interactions with these obliquely-propagating modes can lead to substantial pitch angle scattering of the ring protons. Two-dimensional hybrid (kinetic ions and massless fluid electrons) simulations are carried out to examine the nonlinear consequences of the mirror and Bernstein instabilities. The preliminary simulation results are presented. The study suggests a scenario that the oblique mirror and ion Bernstein modes can be an active agent of the pickup ion isotropization when the condition is such that the Alfvén-cyclotron instability is suppressed.

Mass-loading, pile-up, and mirror-mode waves at comet 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Volwerk, M.; Richter, I.; Tsurutani, B.; Götz, C.; Altwegg, K.; Broiles, T.; Burch, J.; Carr, C.; Cupido, E.; Delva, M.; Dósa, M.; Edberg, N. J. T.; Eriksson, A.; Henri, P.; Koenders, C.; Lebreton, J.-P.; Mandt, K. E.; Nilsson, H.; Opitz, A.; Rubin, M.; Schwingenschuh, K.; Stenberg Wieser, G.; Szegö, K.; Vallat, C.; Vallieres, X.; Glassmeier, K.-H.

2016-01-01

The data from all Rosetta plasma consortium instruments and from the ROSINA COPS instrument are used to study the interaction of the solar wind with the outgassing cometary nucleus of 67P/Churyumov-Gerasimenko. During 6 and 7 June 2015, the interaction was first dominated by an increase in the solar wind dynamic pressure, caused by a higher solar wind ion density. This pressure compressed the draped magnetic field around the comet, and the increase in solar wind electrons enhanced the ionization of the outflow gas through collisional ionization. The new ions are picked up by the solar wind magnetic field, and create a ring/ring-beam distribution, which, in a high-β plasma, is unstable for mirror mode wave generation. Two different kinds of mirror modes are observed: one of small size generated by locally ionized water and one of large size generated by ionization and pick-up farther away from the comet.

Mass-loading, pile-up, and mirror-mode waves at comet 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Volwerk, Martin

2016-04-01

The data from all Rosetta Plasma Consortium instruments and from the ROSINA COPS instrument are used to study the interaction of the solar wind with the outgassing cometary nucleus of 67P/Churyumov-Gerasimenko. During 6 and 7 June 2015, the interaction was first dominated by an increase in the solar wind dynamic pressure, caused by a higher solar wind ion density. This pressure compressed the draped magnetic field around the comet, and the increase in solar wind electrons enhanced the ionization of the outflow gas through collisional ionization. The new ions are picked up by the solar wind magnetic field, and create a ring/ring-beam distribution, which, in a high-β plasma, is unstable for mirror mode wave generation. Two different kinds of mirror modes are observed: one of small size generated by locally ionized water and one of large size generated by ionization and pick-up farther away from the comet.

Pickup Ion Effect of the Solar Wind Interaction with the Local Interstellar Medium

DOE PAGES

Pogorelov, N. V.; Bedford, M. C.; Kryukov, I. A.; ...

2016-11-22

Pickup ions are created when interstellar neutral atoms resonantly exchange charge with the solar wind (SW) ions, especially in the supersonic part of the wind, where they carry most of the plasma pressure. Here we present numerical simulation results of the 3D heliospheric interface treating pickup ions as a separate proton fluid. To satisfy the fundamental conservation laws, we solve the system of equations describing the flow of the mixture of electrons, thermal protons, and pickup ions. To find the density and pressure of pickup ions behind the termination shock, we employ simple boundary conditions that take into account themore » \\emph{Voyager} observations that showed that the decrease in the kinetic energy of the mixture at the termination shock predominantly contributed to the increase in the pressure of pickup ions. We show that this model adequately describes the flow of the plasma mixture and results in a noticeable decrease in the heliosheath width.« less

Finite Gyroradius Effects Observed in Pickup Oxygen Ions at Venus

NASA Technical Reports Server (NTRS)

Hartle, Richard E.; Intriligator, Devrie; Grebowsky, Joseph M.; Einaudi, Franco (Technical Monitor)

2000-01-01

On the dayside of Venus, the hot oxygen corona extending above the ionopause is the principal source of pickup oxygen ions. The ions are born here and picked up by the ionosheath plasma as it is deflected around the planet. These pickup ions have been observed by the Orbiter Plasma Analyzer (OPA) throughout the Pioneer Venus Orbiter (PVO) mission. They were observed over a region extending from their dayside source to great distances downstream (about 10 Venus radii), in the solar wind wake, as PVO passed through apoapsis. Finite gyroradius effects in the velocity distribution of the oxygen pickup ions are expected in the source region because the gyroradius is several times larger than the scale height of the hot oxygen source. Such effects are also expected in those regions of the ionosheath where the scale lengths of the magnetic field and the ambient plasma velocity field are less than the pickup ion gyroradius. While explicitly accounting for the spatial distribution of the hot oxygen source, an analytic expression for the pickup oxygen ion velocity distribution is developed to study how it is affected by finite gyroradii. The analysis demonstrates that as the gyroradius increases by factors of three to six above the hot oxygen scale height, the peak of the pickup oxygen ion flux distribution decreases 25 to 50% below the maximum allowed speed, which is twice the speed of the ambient plasma times the sine of the angle between the magnetic field and the flow velocity. The pickup oxygen ion flux distribution observed by OPA is shown to follow this behavior in the source region. It is also shown that this result is consistent with the pickup ion distributions observed in the wake, downstream of the source, where the flux peaks are usually well below the maximum allowed speed.

Inner Source Pickup Ions Observed by Ulysses

NASA Astrophysics Data System (ADS)

Gloeckler, G.

2016-12-01

The existence of an inner source of pickup ions close to the Sun was proposed in order to explain the unexpected discovery of C+ in the high-speed polar solar wind. Here I report on detailed analyses of the composition and the radial and latitudinal variations of inner source pickup ions measured with the Solar Wind Ion Composition Spectrometer on Ulysses from 1991 to 1998, approaching and during solar minimum. We find that the C+ intensity drops off with radial distance R as R-1.53, peaks at mid latitudes and drops to its lowest value in the ecliptic. Not only was C+ observed, but also N+, O+, Ne+, Na+, Mg+, Ar+, S+, K+, CH+, NH+, OH+, H2O+, H3O+, MgH+, HCN+, C2H4+, SO+ and many other singly-charged heavy ions and molecular ions. The measured velocity distributions of inner source pickup C+ and O+ indicate that these inner source pickup ions are most likely produced by charge exchange, photoionization and electron impact ionization of neutrals close to the Sun (within 10 to 30 solar radii). Possible causes for the unexpected latitudinal variations and the neutral source(s) producing the inner source pickup ions as well as plausible production mechanisms for inner source pickup ions will be discussed.

Contributions of Mirror and Ion Bernstein Instabilities to the Scattering of Pickup Ions in the Outer Heliosheath

NASA Astrophysics Data System (ADS)

Min, Kyungguk; Liu, Kaijun

2018-01-01

Maintaining the stability of pickup ions in the outer heliosheath is a critical element for the secondary energetic neutral atom (ENA) mechanism, a theory put forth to explain the nearly annular band of ENA emission observed by the Interstellar Boundary EXplorer. A recent study showed that a pickup ion ring can remain stable to the Alfvén/ion cyclotron (AC) instability at propagation parallel to the background magnetic field when the parallel thermal spread of the ring is comparable to that of a background population. This study investigates the potential role that the mirror or ion Bernstein (IB) instabilities can play in the stability of pickup ions when conditions are such that the AC instability is suppressed. Linear Vlasov theory predicts relatively fast mirror and IB instability growth even though AC instability growth is suppressed. For a few such cases, two-dimensional hybrid and macroscopic quasi-linear simulations are carried out to examine how the unstable mirror and IB modes evolve and affect the pickup ion ring beyond the linear theory picture. For the parameters used, the mirror mode dominates initially and leads to a rapid parallel heating of the pickup ions in excess of the parallel temperature of the background protons. The heated pickup ions subsequently trigger onset of the AC mode, which grows sufficiently large to be the dominant pitch angle scattering agent after the mirror mode has decayed away. The present results indicate that the pickup ion stability needed may not be guaranteed once the mirror and IB instabilities are taken into account.

O+ pickup ions outside of Venus' bow shock: Venus Express observation

NASA Astrophysics Data System (ADS)

Wei, Y.; Fraenz, M.; Dubinin, E.; Zhang, T. L.; Wan, W.; Barabash, S.; Woch, J.; Lundin, R.

2012-09-01

Pickup ions are ions of planetary origin that become assimilated into the solar wind flow through their interaction with the solar wind magnetic and electric field. The speed of pickup ions varies between zero and twice the underlying plasma flow component perpendicular to magnetic field vector. For the unmagnetized planet Venus and Mars, oxygen (O+) pickup ions are known to be important because they can modify the global configuration of planetary plasma environment and significantly contribute to the atmospheric O+ loss [1]. Since the kinetic energy of an O+ pickup ion can reach 64 times that of a co-moving proton, an instrument must be able to measure O+ ions with energy of at least tens of keV to investigate the O+ pickup ion distribution from planetary ionosphere to solar wind. The in-situ observations and simulations at Mars have shown that the energy of O+ pickup ions can be 55-72 keV outside of the bow shock [2]. For Venus case, the plasma analyzer (OPA) onboard Pioneer Venus Orbiter (PVO), which was designed for solar wind monitoring, has an 8 keV energy limit for O+ detection and the limited sampling and data rate [3]. Therefore, OPA can only measure the O+ pickup ions in the sheath flow or inside the induced magnetosphere where the speed of ambient plasma flow is significantly lower than that of the unshocked solar wind outside of the bow shock. The Ion Mass Analyzer (IMA), included in the Analyzer of Space Plasma and Energetic Atoms (ASPERA-4) package on board Venus Express (VEX), determines the composition, energy, and angular distribution of ions in the energy range ~10 eV/q to 30 keV/q. Note that an O+ ion moving at the typical solar wind speed 400 km/s has kinetic energy 13.4 keV. Therefore, IMA has ability to measure the O+ pickup ions outside of Venus' bow shock. We have examined the IMA data during the solar minimum period 2006-2010, and identified about ten cases with clear signature of O+ pickup ion. With these observations, we will determine the location and the scale height of the source region of O+ pickup ions and describe the relationship between the behavior of these O+ and the upstream solar wind condition. The results would provide new information for numerical simulation of plasma environment near Venus and contribute to estimation of total O+ ion loss from Venus.

Composition of inner-source heavy pickup ions at 1 AU: SOHO/CELIAS/CTOF observations. Implications for the production mechanisms

NASA Astrophysics Data System (ADS)

Taut, A.; Berger, L.; Drews, C.; Wimmer-Schweingruber, R. F.

2015-04-01

Context. Pickup ions in the inner heliosphere mainly originate in two sources, one interstellar and one in the inner solar system. In contrast to the interstellar source that is comparatively well understood, the nature of the inner source has not been clearly identified. Former results obtained with the Solar Wind Ion Composition Spectrometer on-board the Ulysses spacecraft revealed that the composition of inner-source pickup ions is similar, but not equal, to the elemental solar-wind composition. These observations suffered from very low counting statistics of roughly one C+ count per day. Aims: Because the composition of inner-source pickup ions could lead to identifying their origin, we used data from the Charge-Time-Of-Flight sensor on-board the Solar and Heliospheric Observatory. It offers a large geometry factor that results in about 100 C+ counts per day combined with an excellent mass-per-charge resolution. These features enable a precise determination of the inner-source heavy pickup ion composition at 1 AU. To address the production mechanisms of inner-source pickup ions, we set up a toy model based on the production scenario involving the passage of solar-wind ions through thin dust grains to explain the observed deviations of the inner-source PUI and the elemental solar-wind composition. Methods: An in-flight calibration of the sensor allows identification of heavy pickup ions from pulse height analysis data by their mass-per-charge. A statistical analysis was performed to derive the inner-source heavy pickup ion relative abundances of N+, O+, Ne+, Mg+, Mg2+, and Si+ compared to C+. Results: Our results for the inner-source pickup ion composition are in good agreement with previous studies and confirm the deviations from the solar-wind composition. The large geometry factor of the Charge-Time-of-Flight sensor even allowed the abundance ratios of the two most prominent pickup ions, C+ and O+, to be investigated at varying solar-wind speeds. We found that the O+/C+ ratio increases systematically with higher solar-wind speeds. This observation is an unprecedented feature characterising the production of inner-source pickup ions. Comparing our observations to the toy model results, we find that both the deviation from the solar-wind composition and the solar-wind-speed dependent O+/C+ ratio can be explained.

O+ pickup ions outside of Venus' bow shock: Venus Express observations

NASA Astrophysics Data System (ADS)

Wei, Yong; Fraenz, Markus; Dubinin, Eduard; Zhang, Tielong; Jarvinen, Riku; Wan, Weixing; Kallio, Esa; Collinson, Glyn; Barabash, Stars; Norbert, Krupp; Woch, Joachim; Lundin, Rickard; delva, Magda

2013-04-01

Pickup ions are ions of planetary origin that become assimilated into the solar wind flow through their interaction with the solar wind magnetic and electric field. The speed of pickup ions varies between zero and twice the underlying plasma flow component perpendicular to magnetic field vector. For the unmagnetized planet Venus and Mars, oxygen (O+) pickup ions are known to be important because they can modify the global configuration of planetary plasma environment and significantly contribute to the atmospheric O+ loss [1]. Since the kinetic energy of an O+ pickup ion can reach 64 times that of a co-moving proton, an instrument must be able to measure O+ ions with energy of at least tens of keV to investigate the O+ pickup ion distribution from planetary ionosphere to solar wind. The in-situ observations and simulations at Mars have shown that the energy of O+ pickup ions can be 55-72 keV outside of the bow shock [2]. For Venus case, the plasma analyzer (OPA) onboard Pioneer Venus Orbiter (PVO), which was designed for solar wind monitoring, has an 8 keV energy limit for O+ detection and the limited sampling and data rate [3]. Therefore, OPA can only measure the O+ pickup ions in the sheath flow or inside the induced magnetosphere where the speed of ambient plasma flow is significantly lower than that of the unshocked solar wind outside of the bow shock. In addition, Galileo also did not capture O+ outside bowshock during its 1-hour Venus flyby though its plasma instrument had ability to cover the energy band of O+ pickup ions [4]. The Ion Mass Analyzer (IMA), included in the Analyzer of Space Plasma and Energetic Atoms (ASPERA-4) package on board Venus Express (VEX), determines the composition, energy, and angular distribution of ions in the energy range ~10 eV/q to 30 keV/q. Note that an O+ ion moving at the typical solar wind speed 400 km/s has kinetic energy 13.4 keV. Therefore, IMA has ability to measure the O+ pickup ions outside of Venus' bow shock. We have examined the IMA data during the solar minimum period 2006-2010, and identified 80 cases with clear signature of O+ pickup ion. With these observations, we can determine the location and the scale height of the source region of O+ pickup ions and describe the relationship between the behavior of these O+ and the upstream solar wind condition. The results would provide new information for numerical simulation of plasma environment near Venus and contribute to estimation of total O+ ion loss from Venus. Reference: [1] Dubinin, E., M. Fränz, J. Woch, E. Roussos, S. Barabash, R. Lundin, J. D. Winningham, R. A. Frahm, and M. Acuña (2006a), Plasma morphology at Mars: Aspera-3 observations, Space Sci. Rev., 126, 209-238, doi:10.1007/s11214-006-9039-4. [2] Cravens, T. E., A. Hoppe, S. A. Ledvina, and S. McKenna-Lawlor (2002), Pickup ions near Mars associated with escaping oxygen atoms, J. Geophys. Res., 107, 1170, doi:10.1029/2001JA000125. [3] Luhmann, J. G., S. A. Ledvina, J. G. Lyon, and C. T. Russell (2006), Venus O+ pickup ions: Collected PVO results and expectations for Venus Express, Planet. Space Sci., 54, 1457-1471, doi:10.1016/j.pss.2005.10.009. [4] Williams, D. J. et al.(1991), Energetic Particles at Venus: Galileo Results. Science 253, 1525-1528.

Simulating Negative Pickup Ions and Ion Cyclotron Wave Generation at Europa (Invited)

NASA Astrophysics Data System (ADS)

Desai, R. T.; Cowee, M.; Gary, S. P.; Wei, H.; Coates, A. J.; Kataria, D. O.; Fu, X.

2015-12-01

The mass loading of space environments through the ionisation of planetary atmospheres is a fundamental process governing the plasma interactions and long term evolution of celestial bodies across the solar system. Regions containing significant pickup ion populations have been observed to exhibit a rich variety of electromagnetic plasma wave phenomena, the characteristics and properties of which can be used to infer the ion species present, their spatial and temporal distributions, and the global ionisation rates of the neutral material. In this study we present hybrid (kinetic ion, massless fluid electron) simulations of ion pickup and Ion Cyclotron (IC) waves observed in the Jovian magnetosphere and draw comparisons to sub-alfvénic pickup observed by Cassini in the Saturnian system, and also to supra-alfvénic pickup at planetary bodies immersed directly in the solar wind. At Jupiter, Europa has been identified as the secondary mass loader in the magnetosphere, orbiting within a neutral gas torus at ~9.38 Rj. Near Europa, Galileo magnetometer observations displayed bursty IC wave characteristics at the gyrofrequency of a number of species including SO2, K, Cl, O2, and Na, suggesting a complex mass loading environment. A particular deduction from the dataset was the presence of both positively and negatively charged pickup ions, inferred from the left and right hand polarisations of the transverse waves. Using hybrid simulations for both positively and negatively charged Cl pickup ions we are able to self-consistently reproduce the growth of both right and left hand near-circularly polarised waves in agreement with linear theory and, using the observed wave amplitudes, estimate Cl pickup ion densities at Europa.

Probing the Martian Exosphere and Neutral Escape Using Pickup Ions Measured by MAVEN

NASA Astrophysics Data System (ADS)

Rahmati, A.; Larson, D. E.; Cravens, T.; Halekas, J. S.; Lillis, R. J.; McFadden, J. P.; Mitchell, D. L.; Thiemann, E.; Connerney, J. E. P.; Dunn, P.; DiBraccio, G. A.; Espley, J. R.; Eparvier, F. G.; Jakosky, B. M.

2016-12-01

Soon after the MAVEN (Mars Atmosphere and Volatile EvolutioN) spacecraft started orbiting Mars in September 2014, the SEP (Solar Energetic Particle), SWIA (Solar Wind Ion Analyzer), and STATIC (Supra-Thermal and Thermal Ion Composition) instruments onboard the spacecraft started detecting planetary pickup ions. SEP can measure energetic (>50 keV) oxygen pickup ions, the source of which is the extended hot oxygen exosphere of Mars. Model results show that these pickup ions originate from tens of Martian radii upstream of Mars and are energized by the solar wind motional electric field as they gyrate back towards Mars. SEP is blind to pickup hydrogen, as the low energy threshold for detection of hydrogen in SEP is 20 keV; well above the maximum pickup hydrogen energy, which is four times the solar wind proton energy. SWIA and STATIC, on the other hand, can detect both pickup oxygen and pickup hydrogen with energies below 30 keV and created closer to Mars. During the times when MAVEN is outside the Martian bow shock and in the upstream undisturbed solar wind, the solar wind velocity measured by SWIA and the solar wind (or interplanetary) magnetic field measured by the MAG (magnetometer) instrument can be used to model pickup oxygen and hydrogen fluxes near Mars. Solar wind flux measurements of the SWIA instrument are used in calculating charge-exchange frequencies, and data from the EUVM (Extreme Ultraviolet Monitor) and SWEA (Solar Wind Electron Analyzer) instruments are also used in calculating photo-ionization and electron impact frequencies of neutral species in the Martian exosphere. By comparing SEP, SWIA, and STATIC measured pickup ion fluxes with model results, the Martian thermal hydrogen and hot oxygen neutral densities can be probed outside the bow shock, which would place constraints on estimates of oxygen and hydrogen neutral escape rates. We will present model-data comparisons of pickup ions measured outside the Martian bow shock. Our analysis reveals an order of magnitude density change with Mars season in the hydrogen exosphere, whereas the hot oxygen exosphere densities vary less than a factor of 2.

Effects of multiscale phase-mixing and interior conductance in the lunar-like pickup ion plasma wake. First results from 3-D hybrid kinetic modeling

NASA Astrophysics Data System (ADS)

Lipatov, A. S.; Sarantos, M.; Farrell, W. M.; Cooper, J. F.

2018-07-01

The study of multiscale pickup ion phase-mixing in the lunar plasma wake with a hybrid model is the main subject of our investigation in this paper. Photoionization and charge exchange of protons with the lunar exosphere are the ionization processes included in our model. The computational model includes the self-consistent dynamics of the light (H+ or H2+ and He+), and heavy (Na+) pickup ions. The electrons are considered as a fluid. The lunar interior is considered as a weakly conducting body. In this paper we considered for the first time the cumulative effect of heavy neutrals in the lunar exosphere (e.g., Al, Ar), an effect which was simulated with one species of Na+ but with a tenfold increase in total production rates. We find that various species produce various types of plasma tail in the lunar plasma wake. Specifically, Na+ and He+ pickup ions form a cycloid-like tail, whereas the H+ or H2+ pickup ions form a tail with a high density core and saw-like periodic structures in the flank region. The length of these structures varies from 1.5RM to 3.3RM depending on the value of gyroradius for H+ or H2+ pickup ions. The light pickup ions produce more symmetrical jump in the density and magnetic field at the Mach cone which is mainly controlled by the conductivity of the interior, an effect previously unappreciated. Although other pickup ion species had little effect on the nature of the interaction of the Moon with the solar wind, the global structure of the lunar tail in these simulations appeared quite different when the H2+ production rate was high.

Possible Ceres bow shock surfaces based on fluid models

NASA Astrophysics Data System (ADS)

Jia, Y.-D.; Villarreal, M. N.; Russell, C. T.

2017-05-01

The hot electron beams that Dawn detected at Ceres can be explained by fast-Fermi acceleration at a temporary bow shock. A shock forms when the solar wind encounters a temporary atmosphere, similar to a cometary coma. We use a magnetohydrodynamic model to quantitatively reproduce the 3-D shock surface at Ceres and deduce the atmosphere characteristics that are required to create such a shock. Our most simple model requires about 1.8 kg/s, or 6 × 1025/s water vapor production rate to form such a shock. Such an estimate relies on characteristics of the solar wind-Ceres interaction. We present several case studies to show how these conditions affect our estimate. In addition, we contrast these cases with the smaller and narrower shock caused by a subsurface induction. Our multifluid model reveals the asymmetry introduced by the large gyroradius of the heavy pickup ions and further constrains the IMF direction during the events.

Hybrid simulations of positively and negatively charged pickup ions and cyclotron wave generation at Europa

DOE Office of Scientific and Technical Information (OSTI.GOV)

Desai, Ravindra T.; Cowee, Misa; Wei, Hanying

In the vicinity of Europa, Galileo observed bursty Alfvén-cyclotron wave power at the gyrofrequencies of a number of species including K +, math formula, Na +, and Cl +, indicating the localised pickup of these species. Additional evidence for the presence of Chlorine was the occurrence of both left-hand (LH) and right-hand (RH) polarised transverse wave power near the Cl + gyrofrequency, thought to be due to the pickup of both Cl + and the easily formed Chlorine anion, Cl –. To test this hypothesis we use one-dimensional hybrid (kinetic ion, massless fluid electron) simulations for both positive and negativemore » pickup ions and self-consistently reproduce the growth of both LH and RH Alfvén-cyclotron waves in agreement with linear theory. We show how the simultaneous generation of LH and RH waves can result in non-gyrotropic ion distributions and increased wave amplitudes, and how even trace quantities of negative pickup ions are able to generate an observable RH signal. Here, through comparing simulated and observed wave amplitudes, we are able to place the first constraints on the densities of Chlorine pickup ions in localised regions at Europa.« less

Hybrid simulations of positively and negatively charged pickup ions and cyclotron wave generation at Europa

DOE PAGES

Desai, Ravindra T.; Cowee, Misa; Wei, Hanying; ...

2017-09-19

In the vicinity of Europa, Galileo observed bursty Alfvén-cyclotron wave power at the gyrofrequencies of a number of species including K +, math formula, Na +, and Cl +, indicating the localised pickup of these species. Additional evidence for the presence of Chlorine was the occurrence of both left-hand (LH) and right-hand (RH) polarised transverse wave power near the Cl + gyrofrequency, thought to be due to the pickup of both Cl + and the easily formed Chlorine anion, Cl –. To test this hypothesis we use one-dimensional hybrid (kinetic ion, massless fluid electron) simulations for both positive and negativemore » pickup ions and self-consistently reproduce the growth of both LH and RH Alfvén-cyclotron waves in agreement with linear theory. We show how the simultaneous generation of LH and RH waves can result in non-gyrotropic ion distributions and increased wave amplitudes, and how even trace quantities of negative pickup ions are able to generate an observable RH signal. Here, through comparing simulated and observed wave amplitudes, we are able to place the first constraints on the densities of Chlorine pickup ions in localised regions at Europa.« less

Hybrid Simulations of Positively and Negatively Charged Pickup Ions and Cyclotron Wave Generation at Europa.

PubMed

Desai, R T; Cowee, M M; Wei, H; Fu, X; Gary, S P; Volwerk, M; Coates, A J

2017-10-01

In the vicinity of Europa, Galileo observed bursty Alfvén-cyclotron wave power at the gyrofrequencies of a number of species including K + , O 2+, Na + , and Cl + , indicating the localized pickup of these species. Additional evidence for the presence of chlorine was the occurrence of both left-hand (LH) and right-hand (RH) polarized transverse wave power near the Cl + gyrofrequency, thought to be due to the pickup of both Cl + and the easily formed chlorine anion, Cl - . To test this hypothesis, we use one-dimensional hybrid (kinetic ion, massless fluid electron) simulations for both positive and negative pickup ions and self-consistently reproduce the growth of both LH and RH Alfvén-cyclotron waves in agreement with linear theory. We show how the simultaneous generation of LH and RH waves can result in nongyrotropic ion distributions and increased wave amplitudes, and how even trace quantities of negative pickup ions are able to generate an observable RH signal. Through comparing simulated and observed wave amplitudes, we are able to place the first constraints on the densities of Chlorine pickup ions in localized regions at Europa.

Numerical simulation of the generation of turbulence from cometary ion pick-up

NASA Technical Reports Server (NTRS)

Goldstein, M. L.; Roberts, D. A.; Matthaeus, W. H.

1987-01-01

Observations of magnetic field fluctuations near Comet Halley have revealed a rapid development of a Kolmogoroff-like turbulence spectrum extending from below 0.01 Hz to above 0.1 Hz. Spectra obtained far from the comet have a strong peak in power near the Doppler-shifted ion-cyclotron frequency of singly ionized water. Closer to the comet, the spectrum at higher frequencies is enhanced in power level over the background solar wind spectrum by approximately an order of magnitude. The equations of incompressible MHD are solved using a two-dimensional 256 x 256 mode spectral method code to simulate this spectral evolution as an inertial range turbulent cascade. The initial conditions contained a constant magnetic field and a single coherent wave mode at a low wave number. The solar wind turbulence was modeled by a background noise spectrum having a Kolmogoroff spectral index. The coherent mode decayed into an inertial range spectrum with Kolmogoroff slope within a few eddy-turnover times. Both the time scale and the increase in power level of the turbulence seen in the simulation are in accord with the Giotto observations.

The structure of mass-loading shocks. [interaction of solar wind with cometary coma or local interstellar medium using two-fluid model

NASA Technical Reports Server (NTRS)

Zank, G. P.; Khabibrakhmanov, I. KH.; Story, T.

1993-01-01

A new two-fluid model which describes mass loading in the solar wind (e.g., the interaction of the solar wind with a cometary coma or the local interstellar medium) is presented. The self-consistent back-reaction of the mass-loaded ions is included through their effective scattering in low-frequency MHD turbulence and the invocation of a diffusive approximation. Such an approximation has the advantage of introducing self-consistent dissipation coefficients into the governing equations, thereby facilitating the investigation of the internal structure of shocks in mass-loading environments. To illustrate the utility of the new model, we consider the structure of cometary shocks in the hypersonic one-dimensional limit, finding that the incoming solar wind is slowed by both mass loading and the development of a large cometary ion pressure gradient. The shock is broadened and smoothed by the cometary ions with a thickness of the order of the cometary ion diffusion scale.

Background and Pickup Ion Velocity Distribution Dynamics in Titan's Plasma Environment: 3D Hybrid Simulation and Comparison with CAPS T9 Observations

NASA Technical Reports Server (NTRS)

Lipatov, A. S.; Sittler, E. C., Jr.; Hartle, R. E.; Cooper, J. F.; Simpson, D. G.

2011-01-01

In this report we discuss the ion velocity distribution dynamics from the 3D hybrid simulation. In our model the background, pickup, and ionospheric ions are considered as a particles, whereas the electrons are described as a fluid. Inhomogeneous photoionization, electron-impact ionization and charge exchange are included in our model. We also take into account the collisions between the ions and neutrals. The current simulation shows that mass loading by pickup ions H(+); H2(+), CH4(+) and N2(+) is stronger than in the previous simulations when O+ ions are introduced into the background plasma. In our hybrid simulations we use Chamberlain profiles for the atmospheric components. We also include a simple ionosphere model with average mass M = 28 amu ions that were generated inside the ionosphere. The moon is considered as a weakly conducting body. Special attention will be paid to comparing the simulated pickup ion velocity distribution with CAPS T9 observations. Our simulation shows an asymmetry of the ion density distribution and the magnetic field, including the formation of the Alfve n wing-like structures. The simulation also shows that the ring-like velocity distribution for pickup ions relaxes to a Maxwellian core and a shell-like halo.

Comparison of magnetosonic wave and water group ion energy densities at Comet Giacobini-Zinner

NASA Technical Reports Server (NTRS)

Staines, K.; Balogh, A.; Cowley, S. W. H.; Forster, P. M. De F.; Hynds, R. J.; Yates, T. S.; Sanderson, T. R.; Wenzel, K.-P.; Tsurutani, B. T.

1991-01-01

Measurements of the Comet Giacobini-Zinner (GZ) are presented to determine to what extent wave-particle scattering redistributed the initial pick-up energy of the ion population. Also examined is the difference between the ion thermal energy and the energy in the magnetic fields of the waves. In spite of uncertainty of about a factor of 2 noted in the pick-up and mass-loaded regions, it is shown that less than approximately 50 percent of the pick-up energy is converted into wave magnetic energy in the inbound pick-up region.

Systematic Variability of the He+ Pickup Ion Velocity Distribution Function Observed with SOHO/CELIAS/CTOF

NASA Astrophysics Data System (ADS)

Taut, A.; Drews, C.; Berger, L.; Wimmer-Schweingruber, R. F.

2015-12-01

The 1D Velocity Distribution Function (VDF) of He+ pickup ions shows two distinct populations that reflect the sources of these ions. The highly suprathermal population is the result of the ionization and pickup of almost resting interstellar neutrals that are injected into the solar wind as a highly anisotropic torus distribution. The nearly thermalized population is centered around the solar wind bulk speed and is mainly attributed to inner-source pickup ions that originate in the inner heliosphere. It is generally believed that the initial torus distribution of interstellar pickup ions is rapidly isotropized by resonant wave-particle interactions, but recent observations by Drews et al. (2015) of a torus-like VDF strongly limit this isotropization. This in turn means that more observational data is needed to further characterize the kinetic behavior of pickup ions. In this study we use data from the Charge-Time-Of-Flight sensor on-board SOHO. As this sensor offers unrivaled counting statistics for He+ together with a sufficient mass-per-charge resolution it is well-suited for investigating the He+ VDF on comparatively short timescales. We combine this data with the high resolution magnetic field data from WIND via an extrapolation to the location of SOHO. With this combination of instruments we investigate the He+ VDF for time periods of different solar wind speeds, magnetic field directions, and wave power. We find a systematic trend of the short-term He+ VDF with these parameters. Especially by varying the considered magnetic field directions we observe a 1D projection of the anisotropic torus-like VDF. In addition, we investigate stream interaction regions and coronal mass ejections. In the latter we observe an excess of inner-source He+ that is accompanied by a significant increase of heavy pickup ion count rates. This may be linked to the as yet ill understood production mechanism of inner-source pickup ions.

Preliminary Interpretation of Ambient Pickup Ions at Titan Observed by the Cassini Plasma Spectrometer

NASA Technical Reports Server (NTRS)

Hartle, R. E.; Sittler, E. C.; Johnson, R. E.

2004-01-01

The Cassini Plasma Spectrometer (CAPS) instrument is scheduled to observe the plasma environment at Titan October 26,2004 from the Cassini Orbiter. Preliminary CAPS ion measurements from this encounter will be compared with measurements made by the Voyager I Plasma Science Instrument (PSI). The comparison will be used to evaluate previous interpretations and predictions of the Titan plasma environment that have been made using PSI measurements. The comparisons will focus on the composition and nature of the ambient plasma and pickup ions. Using the CAPS ion measurements, some of the questions to be addressed, as stimulated by the previous interpretations and predictions made evaluating PSI data, are the following: A) Are H+ and N+ the major ion components of Saturn's rotating magnetosphere in the vicinity of Titan? B) Are other ambient ions present? C) Are finite gyroradius effects apparent in ambient N+ as the result of its interaction with Titans atmosphere? D) Are the principal pickup ions composed of H+, H2+, N+, N2+ and CH4+? E) Is the dominant pickup ion closest to Titan's ionopause N2+? F) Is there evidence of slowing down of the ambient plasma due to pickup ion mass loading? F) If so, does the ambient plasma slow down rapidly, as the ionopause is approached and heavier pickup ions like N2+ are added? During the Voyager I flyby, Titan was in Saturn's magnetosphere. If Titan is in Saturn's magnetosheath or the solar wind at the encounter, questions similar to the above will be addressed as appropriate.

Pickup Ion Velocity Distributions at Titan: Effects of Spatial Gradients

NASA Technical Reports Server (NTRS)

Hartle, R. E.; Sittler, E. C.

2004-01-01

The principle source of pickup ions at Titan is its neutral exosphere, extending well above the ionopause into the magnetosphere of Saturn or the solar wind, depending on the moon's orbital position. Thermal and nonthermal processes in the thermosphere generate the distribution of neutral atoms and molecules in the exosphere. The combination of these processes and the range of mass numbers, 1 to over 28, contribute to an exospheric source structure that produces pickup ions with gyroradii that are much larger or smaller than the corresponding scale heights of their neutral sources. The resulting phase space distributions are dependent on the spatial structure of the exosphere as well as that of the magnetic field and background plasma. When the pickup ion gyroradius is less than the source gas scale height, the pickup ion velocity distribution is characterized by a sharp cutoff near the maximum speed, which is twice that of the ambient plasma times the sine of the angle between the magnetic field and the flow velocity. This was the case for pickup H(sup +) ions identified during the Voyager 1 flyby. In contrast, as the gyroradius becomes much larger than the scale height, the peak of the velocity distribution in the source region recedes from the maximum speed. Iri addition, the amplitude of the distribution near the maximum speed decreases. These more beam like distributions of heavy ions were not observed from Voyager 1 , but should be observable by more sensitive instruments on future spacecraft, including Cassini. The finite gyroradius effects in the pickup ion velocity distributions are studied by including in the analysis the possible range of spatial structures in the neutral exosphere and background plasma.

Oxygen Pickup Ions Measured by MAVEN Outside the Martian Bow Shock

NASA Astrophysics Data System (ADS)

Rahmati, A.; Cravens, T.; Larson, D. E.; Lillis, R. J.; Dunn, P.; Halekas, J. S.; Connerney, J. E. P.; Eparvier, F. G.; Thiemann, E.; Mitchell, D. L.; Jakosky, B. M.

2015-12-01

The MAVEN (Mars Atmosphere and Volatile EvolutioN) spacecraft entered orbit around Mars on September 21, 2014 and has since been detecting energetic oxygen pickup ions by its SEP (Solar Energetic Particles) and SWIA (Solar Wind Ion Analyzer) instruments. The oxygen pickup ions detected outside the Martian bowshock and in the upstream solar wind are associated with the extended hot oxygen exosphere of Mars, which is created mainly by the dissociative recombination of molecular oxygen ions with electrons in the ionosphere. We use analytic solutions to the equations of motion of pickup ions moving in the undisturbed upstream solar wind magnetic and motional electric fields and calculate the flux of oxygen pickup ions at the location of MAVEN. Our model calculates the ionization rate of oxygen atoms in the exosphere based on the hot oxygen densities predicted by Rahmati et al. (2014), and the sources of ionization include photo-ionization, charge exchange, and electron impact ionization. The photo-ionization frequency is calculated using the FISM (Flare Irradiance Spectral Model) solar flux model, based on MAVEN EUVM (Extreme Ultra-Violet Monitor) measurements. The frequency of charge exchange between a solar wind proton and an oxygen atom is calculated using MAVEN SWIA solar wind proton flux measurements, and the electron impact ionization frequency is calculated based on MAVEN SWEA (Solar Wind Electron Analyzer) solar wind electron flux measurements. The solar wind magnetic field used in the model is from the measurements taken by MAVEN MAG (magnetometer) in the upstream solar wind. The good agreement between our predicted pickup oxygen fluxes and the MAVEN SEP and SWIA measured ones confirms detection of oxygen pickup ions and these model-data comparisons can be used to constrain models of hot oxygen densities and photochemical escape flux.

2D He+ Pickup Ion Velocity Distribution Functions: STEREO PLASTIC Observations

NASA Astrophysics Data System (ADS)

Drews, C.; Berger, L.; Peleikis, T.; Wimmer-Schweingruber, R. F.

2014-12-01

He+ pickup ions are either born from the ionization of interstellar neutral helium atoms inside our heliosphere, the so called interstellar pickup ions, or through the interaction of solar wind ions with small dust particles close to the Sun, the so called inner-source of pickup ions. Until now, most observations of He+ pickup ions were limited to reduced 1D velocity spectra, which are insufficient to study certain characteristics of the He+ Velocity Distribution Function (VDF). It is generally assumed that rapid pitch-angle scattering of freshly created pickup ions quickly leads to a fully isotropic He+ VDF. In the light of recent observations, this assumption has found to be oversimplified and needs to be re-investigated. Using He+ pickup ion data from the PLASTIC instrument on board the STEREO A spacecraft we reconstruct a reduced form of the He+ VDF in 2 dimensions (see figure). The reduced form of the He+ VDF allows us to study the pitch-angle distribution and anisotropy of the He+ VDF as a function of the solar magnetic field, B. Our observations show clear signs of a significant anisotropy of the He+ VDF and even indicates that, at least for certain configurations of B, it is not even fully gyrotropic. Our results further suggest, that the observed velocity and pitch-angle of He+ depends strongly on the solar magnetic field vector, B, the ecliptic longitude, λ, the solar wind speed, vsw, and the history of B. Consequently, we argue that reduced 1D velocity spectra of He+ are insufficient to study quantities like the pitch-angle scattering rate, τ, or the adiabatic cooling index γ.

Lunar Pickup Ions Observed by ARTEMIS: Spatial and Temporal Distribution and Constraints on Species and Source Locations

NASA Technical Reports Server (NTRS)

Halekas, Jasper S.; Poppe, A. R.; Delory, G. T.; Sarantos, M.; Farrell, W. M.; Angelopoulos, V.; McFadden, J. P.

2012-01-01

ARTEMIS observes pickup ions around the Moon, at distances of up to 20,000 km from the surface. The observed ions form a plume with a narrow spatial and angular extent, generally seen in a single energy/angle bin of the ESA instrument. Though ARTEMIS has no mass resolution capability, we can utilize the analytically describable characteristics of pickup ion trajectories to constrain the possible ion masses that can reach the spacecraft at the observation location in the correct energy/angle bin. We find that most of the observations are consistent with a mass range of approx. 20-45 amu, with a smaller fraction consistent with higher masses, and very few consistent with masses below 15 amu. With the assumption that the highest fluxes of pickup ions come from near the surface, the observations favor mass ranges of approx. 20-24 and approx. 36-40 amu. Although many of the observations have properties consistent with a surface or near-surface release of ions, some do not, suggesting that at least some of the observed ions have an exospheric source. Of all the proposed sources for ions and neutrals about the Moon, the pickup ion flux measured by ARTEMIS correlates best with the solar wind proton flux, indicating that sputtering plays a key role in either directly producing ions from the surface, or producing neutrals that subsequently become ionized.

Korteweg-deVries-Burgers (KdVB) equation in a five component cometary plasma with kappa described electrons and ions

NASA Astrophysics Data System (ADS)

Michael, Manesh; Willington, Neethu T.; Jayakumar, Neethu; Sebastian, Sijo; Sreekala, G.; Venugopal, Chandu

2016-12-01

We investigate the existence of ion-acoustic shock waves in a five component cometary plasma consisting of positively and negatively charged oxygen ions, kappa described hydrogen ions, hot solar electrons, and slightly colder cometary electrons. The KdVB equation has been derived for the system, and its solution plotted for different kappa values, oxygen ion densities, as well as the temperature ratios for the ions. It is found that the amplitude of the shock wave decreases with increasing kappa values. The strength of the shock profile decreases with increasing temperatures of the positively charged oxygen ions and densities of negatively charged oxygen ions.

MAVEN Pickup Ion Constraints on Mars Neutral Escape

NASA Astrophysics Data System (ADS)

Rahmati, A.; Larson, D. E.; Cravens, T.; Lillis, R. J.; Dunn, P.; Halekas, J. S.; McFadden, J. P.; Mitchell, D. L.; Thiemann, E.; Connerney, J. E. P.; DiBraccio, G. A.; Espley, J. R.; Eparvier, F. G.

2017-12-01

Mars is currently losing its atmosphere mainly due to the escape of neutral hydrogen and oxygen. Directly measuring the rate of escaping neutrals is difficult, because the neutral density in the Mars exosphere is dominated, up to several Martian radii, by atoms that are gravitationally bound to the planet. Neutral atoms in the Martian exosphere, however, can get ionized, picked up, and accelerated by the solar wind motional electric field and energized to energies high enough for particle detectors to measure them. The MAVEN SEP instrument detects O+ pickup ions that are created at altitudes where the escaping part of the exosphere is dominant. Fluxes of these ions reflect neutral densities in the distant exosphere of Mars, allowing us to constrain neutral oxygen escape rates. The MAVEN SWIA and STATIC instruments measure pickup H+ and O+ created closer to Mars; comparisons of these data with models can be used to constrain exospheric hot O and thermal H densities and escape rates. In this work, pickup ion measurements from SEP, SWIA, and STATIC, taken during the first 3 Earth years of the MAVEN mission, are compared to the outputs of a pickup ion model to constrain the variability of neutral escape at Mars. The model is based on data from six MAVEN instruments, namely, MAG providing magnetic field used in calculating pickup ion trajectories, SWIA providing solar wind velocity as well as 3D pickup H+ and O+ spectra, SWEA providing solar wind electron spectrum used in electron impact ionization rate calculations, SEP providing pickup O+ spectra, STATIC providing mass resolved 3D pickup H+ and O+ spectra, and EUVM providing solar EUV spectra used in photoionization rate calculations. A variability of less than a factor of two is observed in hot oxygen escape rates, whereas thermal escape of hydrogen varies by an order of magnitude with Mars season. This hydrogen escape variability challenges our understanding of the H cycle at Mars, but is consistent with other recent measurements.

Positive and negative ion outflow at Rhea as observed by Cassini

NASA Astrophysics Data System (ADS)

Desai, Ravindra; Jones, Geraint; Regoli, Leonardo; Cowee, Misa; Coates, Andrew; Kataria, Dhiren

2017-04-01

Rhea is Saturn's largest icy moon and hosts an ethereal oxygen and carbon-dioxide atmosphere as was detected when Cassini observed positive and negative pickup ions outflowing from the moon and an extended neutral exosphere. These pickup ions can form current systems which, with the resulting jxB force, act to slow-down the incident magneto-plasma and cause field-line draping. As well as impacting the plasma interaction, the composition and density of picked up ions provide key diagnostics of the moon's sputter-induced atmosphere and surface. During the first Cassini-Rhea encounter (R1), the Cassini Plasma Spectrometer (CAPS) observed positively and negatively charged pickup ions before and after passing through the moon's plasma wake respectively, in agreement with their anticipated cycloidal trajectories. On the subsequent more distant wake encounter (R1.5) however, only positively charged pickup ions were observed, indicating high loss rates of the negative ions in Saturn's magnetosphere. Here, using an updated model of Cassini's Electron Spectrometer response function, we are able to estimate the outward flux of negatively charged pickup ions, the first time such a plasma population has been constrained. Using test-particle simulations we trace both the positive and negative particles back to Rhea's exobase to better understand their production and loss processes and the implications for Rhea's sputter-induced exosphere. We also look to examine whether the calculated ion densities could generate ion cyclotron wave activity.

Systematic Variability of the He+ Pickup Ion Velocity Distribution Function Observed with SOHO/CELIAS/CTOF

NASA Astrophysics Data System (ADS)

Taut, Andreas; Drews, Christian; Berger, Lars; Wimmer-Schweingruber, Robert

2016-04-01

The 1D Velocity Distribution Function (VDF) of He+ pickup ions shows two distinct populations that reflect the sources of these ions. The highly suprathermal population is the result of the ionization and pickup of almost resting interstellar neutrals that are injected into the solar wind as a highly anisotropic torus distribution. The nearly thermalized population is centered around the solar wind bulk speed and is mainly attributed to inner-source pickup ions that originate in the inner heliosphere. Current pickup ion models assume a rapid isotropization of the initial VDF by resonant wave-particle interactions, but recent observations by Drews et al. (2015) of a torus-like VDF strongly limit this isotropization. This in turn means that more observational data is needed to further characterize the kinetic behavior of pickup ions. The Charge-Time-Of-Flight sensor on-board SOHO offers unrivaled counting statistics for He+ and a sufficient mass-per-charge resolution. Thus, the He+ VDF can be observed on comparatively short timescales. We combine this data with the magnetic field data from WIND via an extrapolation to the location of SOHO. On the one hand we investigate the 1D VDF of He+ pickup ions with respect to different magnetic field orientations. Our findings complement on previous studies with other instruments that show an anisotropy of the VDF that is linked to the initial torus VDF. On the other hand we find a significant modification of the VDF during stream-interaction region. This may be linked to a different cooling behaviour in these regions and/or the absence of inner-source He+ during these times. Here, we report on our preliminary results.

Cometary ion dynamics observed in the close vicinity of comet 67P/Churyumov-Gerasimenko during the intermediate activity period

NASA Astrophysics Data System (ADS)

Berčič, L.; Behar, E.; Nilsson, H.; Nicolaou, G.; Wieser, G. Stenberg; Wieser, M.; Goetz, C.

2018-06-01

Aims: Cometary ions are constantly produced in the coma, and once produced they are accelerated and eventually escape the coma. We describe and interpret the dynamics of the cometary ion flow, of an intermediate active comet, very close to the nucleus and in the terminator plane. Methods: We analysed in situ ion and magnetic field measurements, and characterise the velocity distribution functions (mostly using plasma moments). We propose a statistical approach over a period of one month. Results: On average, two populations were observed, separated in phase space. The motion of the first is governed by its interaction with the solar wind farther upstream, while the second one is accelerated in the inner coma and displays characteristics compatible with an ambipolar electric field. Both populations display a consistent anti-sunward velocity component. Conclusions: Cometary ions born in different regions of the coma are seen close to the nucleus of comet 67P/Churyumov-Gerasimenko with distinct motions governed in one case by the solar wind electric field and in the other case by the position relative to the nucleus. A consistent anti-sunward component is observed for all cometary ions. An asymmetry is found in the average cometary ion density in a solar wind electric field reference frame, with higher density in the negative (south) electric field hemisphere. There is no corresponding signature in the average magnetic field strength.

Direct Acceleration of Pickup Ions at The Solar Wind Termination Shock: The Production of Anomalous Cosmic Rays

NASA Technical Reports Server (NTRS)

Ellison, Donald C.; Jones, Frank C.; Baring, Matthew G.

1998-01-01

We have modeled the injection and acceleration of pickup ions at the solar wind termination shock and investigated the parameters needed to produce the observed Anomalous Cosmic Ray (ACR) fluxes. A non-linear Monte Carlo technique was employed, which in effect solves the Boltzmann equation and is not restricted to near-isotropic particle distribution functions. This technique models the injection of thermal and pickup ions, the acceleration of these ions, and the determination of the shock structure under the influence of the accelerated ions. The essential effects of injection are treated in a mostly self-consistent manner, including effects from shock obliquity, cross- field diffusion, and pitch-angle scattering. Using recent determinations of pickup ion densities, we are able to match the absolute flux of hydrogen in the ACRs by assuming that pickup ion scattering mean free paths, at the termination shock, are much less than an AU and that modestly strong cross-field diffusion occurs. Simultaneously, we match the flux ratios He(+)/H(+) or O(+)/H(+) to within a factor approx. 5. If the conditions of strong scattering apply, no pre-termination-shock injection phase is required and the injection and acceleration of pickup ions at the termination shock is totally analogous to the injection and acceleration of ions at highly oblique interplanetary shocks recently observed by the Ulysses spacecraft. The fact that ACR fluxes can be modeled with standard shock assumptions suggests that the much-discussed "injection problem" for highly oblique shocks stems from incomplete (either mathematical or computer) modeling of these shocks rather than from any actual difficulty shocks may have in injecting and accelerating thermal or quasi-thermal particles.

Survey of pickup ion signatures in the vicinity of Titan using CAPS/IMS

NASA Astrophysics Data System (ADS)

Regoli, L. H.; Coates, A. J.; Thomsen, M. F.; Jones, G. H.; Roussos, E.; Waite, J. H.; Krupp, N.; Cox, G.

2016-09-01

Pickup ion detection at Titan is challenging because ion cyclotron waves are rarely detected in the vicinity of the moon. In this work, signatures left by freshly produced pickup heavy ions (m/q ˜ 16 to m/q ˜ 28) as detected in the plasma data by the Cassini Plasma Spectrometer/Ion Mass Spectrometer (CAPS/IMS) instrument on board Cassini are analyzed. In order to discern whether these correspond to ions of exospheric origin, one of the flybys during which the reported signatures were observed is investigated in detail. For this purpose, ion composition data from time-of-flight measurements and test particle simulations to constrain the ions' origin are used. After being validated, the detection method is applied to all the flybys for which the CAPS/IMS instrument gathered valid data, constraining the region around the moon where the signatures are observed. The results reveal an escape region located in the anti-Saturn direction as expected from the nominal corotation electric field direction. These findings provide new constraints for the area of freshly produced pickup ion escape, giving an approximate escape rate of 3.3-2+3×1023 ions· s-1.

Three dimensional Particle-in-Cell (PIC) simulations of the 67P environment

NASA Astrophysics Data System (ADS)

Divin, Andrey; Deca, Jan; Henri, Pierre; Horanyi, Mihaly; Markidis, Stefano; Lapenta, Giovanni; Olshevsky, Vyacheslav; Eriksson, Anders

2017-04-01

ESA's Rosetta orbiter spacecraft escorted comet 67P/Churyumov-Gerasimenko for two years, carrying 21 scientific instruments. Five of those were dedicated to plasma measurements. The mission revealed for the first time, and in unprecedented detail, the fascinating evolution of a comet and its interaction with our Sun as it races along its 6.45yr elliptical orbit around the Sun. Using a self-consistent 3-D fully kinetic electromagnetic particle-in-cell approach, we focus on the global cometary environment and, in particular, on the collisionless electron-kinetic interaction. We include cometary ions and electrons produced by the ionization of the outgassing cometary atmosphere in addition to the solar wind ion and electron plasma flow. We approximate mass-loading of the cold cometary ion and electron populations using a 1/r relation with distance to the comet with a total neutral production rate of Q = 1026 s-1. Our simulation results disentangle for the first time the kinetic ion and electron dynamics of the solar wind interaction with a weakly outgassing comet. The simulated global structure of the solar wind-comet interaction confirms the results reported in hybrid simulations of the induced cometary magnetosphere. Moreover, we show that cometary and solar wind electrons neutralize the solar wind protons and cometary ions, respectively, in the region of influence around the comet, representing to first order a four-fluid behavior. The electron energy distribution close to the comet is shown to be a mix of cometary and solar wind electrons that appear as, respectively, a thermal and a suprathermal components. Analyzing ion and electron energy distribution functions, and comparing with plasma measurements from ESA's Rosetta mission to comet 67P/Churyumov-Gerasimenko, we conclude that a detailed kinetic treatment of the electron dynamics is critical to fully capture the complex physics of mass-loading plasmas.

Three Dimensional Explicit Model for Cometary Tail Ions Interactions with Solar Wind

NASA Astrophysics Data System (ADS)

Al Bermani, M. J. F.; Alhamed, S. A.; Khalaf, S. Z.; Ali, H. Sh.; Selman, A. A.

2009-06-01

The different interactions between cometary tail and solar wind ions are studied in the present paper based on three-dimensional Lax explicit method. The model used in this research is based on the continuity equations describing the cometary tail-solar wind interactions. Three dimensional system was considered in this paper. Simulation of the physical system was achieved using computer code written using Matlab 7.0. The parameters studied here assumed Halley comet type and include the particle density rho, the particles velocity v, the magnetic field strength B, dynamic pressure p and internal energy E. The results of the present research showed that the interaction near the cometary nucleus is mainly affected by the new ions added to the plasma of the solar wind, which increases the average molecular weight and result in many unique characteristics of the cometary tail. These characteristics were explained in the presence of the IMF.

Solar wind pickup of ionized Venus exosphere atoms

NASA Technical Reports Server (NTRS)

Curtis, S. A.

1981-01-01

Previous calculations of electrostatic and electromagnetic growth rates for plasma instabilities have neglected the thermal spread of the distribution function of the planetary ions. We consider the effects of finite temperatures for exospheric ions borne in the solar wind. Specifically, growth rates are calculated for electromagnetic instabilities in the low-frequency case for Alfven waves and the intermediate frequency case for whistlers. Also, electrostatic growth rates are calculated for the intermediate frequency regime. From these growth rates, estimates are derived for the pickup times of the planetary ions. The electromagnetic instabilities are shown to produce the most rapid pickup. In the situation where the angle between the local Venus magnetic field and the plasma flow direction is small, the pickup times for both electromagnetic and electrostatic instabilities become very long. A possible consequence of this effect is to produce regions of enhanced planetary ion density in favorable Venus magnetic field-solar wind flow geometries.

Momentum transport at the Mars magnetopause

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perez-de-Tejada, H.

1991-07-01

The conditions leading to the transport of momentum of the shocked solarwind to the Mars magnetosphere are examined. It is argued that planetary pickup ions born in the magnetosheath and scattered across the magnetopause by local turbulent waves carry that momentum and deliver it to the magnetospheric plasma. It is further suggested that as the pickup ions experience momentum scattering interactions with the wave field in the velocity shear adjacent to the magnetosphere they are subject to a gradual internment within that region of space. The end effect of this phenomenon is that the pickup ions deliver a larger amountmore » of momentum to the local flow than what they can subtract from it. Calculations of the efficiency of the process lead to values of the effective mean free path of the pickup ions of the order of a few hundred kilometers.« less

Theoretical studies of the solar atmosphere and interstellar pickup ions

NASA Technical Reports Server (NTRS)

1994-01-01

Solar atmosphere research activities are summarized. Specific topics addressed include: (1) coronal mass ejections and related phenomena; (2) parametric instabilities of Alfven waves; (3) pickup ions in the solar wind; and (4) cosmic rays in the outer heliosphere. Also included is a list of publications covering the following topics: catastrophic evolution of a force-free flux rope; maximum energy release in flux-rope models of eruptive flares; sheet approximations in models of eruptive flares; material ejection, motions of loops and ribbons of two-ribbon flares; dispersion relations for parametric instabilities of parallel-propagating; parametric instabilities of parallel-propagating Alfven waves; beat, modulation, and decay instabilities of a circularly-polarized Alfven wave; effects of time-dependent photoionization on interstellar pickup helium; observation of waves generated by the solar wind pickup of interstellar hydrogen ions; ion thermalization and wave excitation downstream of the quasi-perpendicular bowshock; ion cyclotron instability and the inverse correlation between proton anisotrophy and proton beta; and effects of cosmic rays and interstellar gas on the dynamics of a wind.

Cometary Plasma Probed by Rosetta

NASA Astrophysics Data System (ADS)

Galand, Marina; Vigren, Erik; Raghuram, Susarla; Schwartz, Steve; Eriksson, Anders; Edberg, Niklas; Lebreton, Jean-Pierre; Henri, Pierre; Burch, Jim; Fuselier, Stephen; Haessig, Myrtha; Mandt, Kathy; Altwegg, Kathrin; Tzou, Chia-You

2015-04-01

In Fall 2014, comet 67P/Churyumov-Gerasimenko, the main target of the Rosetta mission, was at 3 AU from the Sun. Its outgassing rate was only of the order of 5×1025 s-1 based on Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) / Cometary Pressure Sensor (COPS). Despite such a thin coma, a plasma of cometary origin has been detected by Rosetta Plasma Consortium (RPC) sensors and ROSINA/ Double Focusing Mass Spectrometer (DFMS). Close to the comet they have revealed the presence of a cometary ionosphere, with a hot electron population, consistent with the deposition of Extreme UltraViolet (EUV) solar radiation. We will present a comparison between RPC sensors and an energy deposition model in terms of suprathermal electron intensities [RPC/ Ion and Electron Sensor (IES)] and electron temperature and density [RPC/ LAngmuir Probe (LAP) and RPC/ Mutual Impedance Probe (MIP)]. We will also compare ion composition among the main species, between our ionospheric model and ROSINA/DFMS. We will discuss effects of the space environment on the cometary plasma. Finally, we will highlight any evolution in the cometary plasma as the comet is getting closer to perihelion.

Pickup Ion Distributions from Three Dimensional Neutral Exospheres

NASA Technical Reports Server (NTRS)

Hartle, R. E.; Sarantos, M.; Sittler, E. C., Jr.

2011-01-01

Pickup ions formed from ionized neutral exospheres in flowing plasmas have phase space distributions that reflect their source's spatial distributions. Phase space distributions of the ions are derived from the Vlasov equation with a delta function source using three.dimensional neutral exospheres. The ExB drift produced by plasma motion picks up the ions while the effects of magnetic field draping, mass loading, wave particle scattering, and Coulomb collisions near a planetary body are ignored. Previously, one.dimensional exospheres were treated, resulting in closed form pickup ion distributions that explicitly depend on the ratio rg/H, where rg is the ion gyroradius and H is the neutral scale height at the exobase. In general, the pickup ion distributions, based on three.dimensional neutral exospheres, cannot be written in closed form, but can be computed numerically. They continue to reflect their source's spatial distributions in an implicit way. These ion distributions and their moments are applied to several bodies, including He(+) and Na(+) at the Moon, H(+2) and CH(+4) at Titan, and H+ at Venus. The best places to use these distributions are upstream of the Moon's surface, the ionopause of Titan, and the bow shock of Venus.

Low-frequency waves at comet 67P/Churyumov-Gerasimenko. Observations compared to numerical simulations

NASA Astrophysics Data System (ADS)

Koenders, C.; Perschke, C.; Goetz, C.; Richter, I.; Motschmann, U.; Glassmeier, K. H.

2016-10-01

Context. A new type of low-frequency wave was detected by the magnetometer of the Rosetta Plasma Consortium at the comet during the initial months after the arrival of the Rosetta spacecraft at comet 67P/Churyumov-Gerasimenko. This large-amplitude, nearly continuous wave activity is observed in the frequency range from 30 mHz to 80 mHz where 40 mHz to 50 mHz is the dominant frequency. This type of low frequency is not closely related to the gyrofrequency of newborn cometary ions, which differs from previous wave activity observed in the interaction region of comets with the solar wind. Aims: This work aims to reveal a global view on the wave activity region using simulations of the comet-solar wind interaction region. Parameters, such as wavelength, propagation direction, and propagation patterns, are within the focus of this study. While the Rosetta observations only provide local information, numerical simulations provide further information on the global wave properties. Methods: Standard hybrid simulations were applied to the comet-solar wind interaction scenario. In the model, the ions were described as particles, which allows us to describe kinetic processes of the ions. The electrons were described as a fluid. Results: The simulations exhibit a threefold wave structure of the interaction region. A Mach cone and a Whistler wing are observed downstream of the comet. The third kind of wave activity found are low-frequency waves at 97 mHz, which corresponds to the waves observed by Richter et al. (2015, Ann. Geophys., 33, 1031). These waves are caused by the initial pick-up of the cometary ions that are perpendicular to the solar wind flow and in the interplanetary magnetic field direction. The associated electric current becomes unstable. The simulations show that wave activity is only detectable in the + E hemisphere and that the Mach cone and whistler wings need to be distinguished from the newly found instability driven wave activity. The movie associated to Fig. 10 is available at http://www.aanda.org

Unusual characteristics of electromagnetic waves excited by cometary newborn ions with large perpendicular energies

NASA Technical Reports Server (NTRS)

Brinca, A. L.; Tsurutani, B. T.

1987-01-01

The characteristics of electromagnetic waves excited by cometary newborn ions with large perpendicular energies are examined using a model of solar wind permeated by dilute drifting ring distributions of electrons and oxygen ions with finite thermal spreads. The model has parameters compatible with the ICE observations at the Giacobini-Zinner comet. It is shown that cometary newborn ions with large perpendicular energies can excite a wave mode with rest frame frequencies in the order of the heavy ion cyclotron frequency, Omega(i), and unusual propagation characteristics at small obliquity angles. For parallel propagation, the mode is left-hand circularly polarized, might be unstable in a frequency range containing Omega(i), and moves in the direction of the newborn ion drift along the static magnetic field.

Sodium Pick-Up Ion Observations in the Solar Wind Upstream of Mercury

NASA Astrophysics Data System (ADS)

Jasinski, J. M.; Raines, J. M.; Slavin, J. A.; Regoli, L. R.; Murphy, N.

2018-05-01

We present the first observations of sodium pick-up ions upstream of Mercury’s magnetosphere. From these observations we infer properties of Mercury’s sodium exosphere and implications for the solar wind interaction with Mercury’s magnetosphere.

Studies of Interstellar Pickup Ions in the Solar Wind

NASA Technical Reports Server (NTRS)

Isenberg, Philip A.; Lee, Martin A.; Mobius, Eberhard

1996-01-01

The work under this grant involves studies of the interaction of interstellar pickup ions with the solar wind, with the goal of a comprehensive model of the particle distributions and wave intensities to be expected throughout the heliosphere, as well as the interactions of those distributions with the solar wind termination shock. In the past year, we have completed a number of projects, including observations and modeling of the effects of a large scattering mean free path on the pickup He(+) seen at AMPTE, an analytical model of anisotropic pickup tons in a steady radial magnetic field, and a derivation of a reduced solar wind Mach number due to increased estimates on the inflowing hydrogen density allowing for a weak termination shock. In the next year, we plan to investigate in more detail the correspondence between our models of anisotropic pickup ions and the data on spectra, variations, and proton-He(+) correlation provided by AMPTE, Ulysses, and our instrument on SOHO. We will model the time-dependent pickup ion density resulting from finite periods of radial magnetic field. We will also incorporate the effects of a large mean free path into our analysis of the He(+) focusing cone, leading to more accurate parameter values for the interstellar helium gas. This progress report also includes a discussion of our Space Physics Educational Outreach activities in the past year and plans for the next year.

On the Effects of Pickup Ion-driven Waves on the Diffusion Tensor of Low-energy Electrons in the Heliosphere

DOE Office of Scientific and Technical Information (OSTI.GOV)

Engelbrecht, N. Eugene, E-mail: n.eugene.engelbrecht@gmail.com

The effects of Alfvén cyclotron waves generated due to the formation in the outer heliosphere of pickup ions on the transport coefficients of low-energy electrons is investigated here. To this end, parallel mean free path (MFP) expressions are derived from quasilinear theory, employing the damping model of dynamical turbulence. These are then used as inputs for existing expressions for the perpendicular MFP and turbulence-reduced drift coefficient. Using outputs generated by a two-component turbulence transport model, the resulting diffusion coefficients are compared with those derived using a more typically assumed turbulence spectral form, which neglects the effects of pickup ion-generated waves.more » It is found that the inclusion of pickup ion effects greatly leads to considerable reductions in the parallel and perpendicular MFPs of 1–10 MeV electrons beyond ∼10 au, which are argued to have significant consequences for studies of the transport of these particles.« less

On the role of the quasi-parallel bow shock in ion pickup - A lesson from Venus?

NASA Technical Reports Server (NTRS)

Luhmann, J. G.; Russell, C. T.; Phillips, J. L.; Barnes, A.

1987-01-01

Previous observations at Venus show convincing evidence of planetary O(+) ion pickup by the largescale motional -V x B electric field in the magnetosheath when the interplanetary magnetic field is perpendicular to the solar wind flow. However, the presence of magnetic field fluctuations in the magnetosheath downstream from the quasi-parallel bow shock should allow pickup to occur even when the upstream magnetic field B and plasma velocity V are practically coaligned. Single-particle calculations are used to demonstrate the convecting magnetic field fluctuations similar to those observed in the Venus magnetosheath when the subsolar bow shock is quasi-parallel can efficiently accelerate cold planetary ions by means of the electric field associated with their transverse components. This ion pickup process, which is characterized by a spatial dependence determined by the bow shock shape and the orientation of the upstream magnetic field, is likely also to occur at Mars and may be effective at comets.

Observations of high-plasma density region in the inner coma of 67P/Churyumov-Gerasimenko during early activity

NASA Astrophysics Data System (ADS)

Yang, Lei; Paulsson, J. J. P.; Wedlund, C. Simon; Odelstad, E.; Edberg, N. J. T.; Koenders, C.; Eriksson, A. I.; Miloch, W. J.

2016-11-01

In 2014 September, as Rosetta transitioned to close bound orbits at 30 km from comet 67P/Churyumov-Gerasimenko, the Rosetta Plasma Consortium Langmuir probe (RPC-LAP) data showed large systematic fluctuations in both the spacecraft potential and the collected currents. We analyse the potential bias sweeps from RPC-LAP, from which we extract three sets of parameters: (1) knee potential, that we relate to the spacecraft potential, (2) the ion attraction current, which is composed of the photoelectron emission current from the probe as well as contributions from local ions, secondary emission, and low-energy electrons, and (3) an electron current whose variation is, in turn, an estimate of the electron density variation. We study the evolution of these parameters between 4 and 3.2 au in heliocentric and cometocentric frames. We find on September 9 a transition into a high-density plasma region characterized by increased knee potential fluctuations and plasma currents to the probe. In conjunction with previous studies, the early cometary plasma can be seen as composed of two regions: an outer region characterized by solar wind plasma, and small quantities of pick-up ions, and an inner region with enhanced plasma densities. This conclusion is in agreement with other RPC instruments such as RPC-MAG, RPC-IES and RPC-ICA, and numerical simulations.

On the Anisotropy of the He+, C+, O+, and Ne+ Pickup Ion Velocity Distribution Function: STEREO PLASTIC Observations

NASA Astrophysics Data System (ADS)

Taut, A.; Drews, C.; Berger, L.; Peleikis, T.; Wimmer-Schweingruber, R. F.

2015-12-01

PickUp Ions (PUIs) are typically characterized by (1) their almost exclusively single charge state, (2) a highly non-thermal and anisotropic Velocity Distribution Function (VDF) [Drews et al., 2015], and (3) an extended source population of neutral atoms somewhere between the observer and the Sun. The origin of pickup ions ranges from sources only several solar radii away from the Sun, the so-called inner-source of pickup ions, up to a distance of several hundreds of astronomical units, the local interstellar medium. Their continuous production inside the heliosphere and complex interactions with the magnetized solar wind plasma leads to the development of non-thermal, anisotropic features of both the solar wind and pickup ion velocity distribution functions. In this study, we present observations of the VDF of He+, C+, N+, O+ and Ne+ pickup ions with PLASTIC on STEREO A. We have found a PUI flux increase during perpendicular configurations of the local magnetic field that is generally linked to the existence of a so-called torus-distribution [Drews et al., 2015] which is attributed to the production of PUIs close to the observer. A comparison of the PUI VDF between radial and perpendicular configurations of the local magnetic field vector is used to quantify the anisotropy of the PUI VDF and thereby enables us to estimate the mean free path for pitch-angle scattering of He, C, N, O and Ne pickup ions without the necessity of an over-simplified heliospheric model to describe the PUI phase space transport. Our results show a clear signature of a C+ torus signature at 1 AU as well as significant differences between the anisotropies of the He+ and O+ VDF. We will discuss our results in the light of recent studies about the nature of the inner-source of PUIs [Berger et al., 2015] and observations of the 2D VDF of He+[Drews et al., 2015]. Figure Caption: Velocity space diagrams of a pickup ion torus distribution as a (vx-vy)-projection (top left panel) and in the vz = 0 km/s plane (top right) are shown for magnetic configuration in which B is almost perpendicular. The bottom two panels show the torus distribution under the influence of pitch-angle scattering (right) and adiabatic cooling (left). To illustrate the torus character of the distribution the (vx-vy)-plane is slightly tilted in this diagram.

Detection of singly ionized energetic lunar pick-up ions upstream of earth's bow shock

NASA Technical Reports Server (NTRS)

Hilchenbach, M.; Hovestadt, D.; Klecker, B.; Moebius, E.

1992-01-01

Singly ionized suprathermal ions upstream of the earth's bow shock have been detected by using the time-of-flight spectrometer SULEICA on the AMPTE/IRM satellite. The data were collected between August and December 1985. The flux of the ions in the mass range between 23 and 37 amu is highly anisotropic towards the earth. The ions are observed with a period of about 29 days around new moon (+/- 3 days). The correlation of the energy of the ions with the solar wind speed and the interplanetary magnetic field orientation indicates the relation to the pick-up process. We conclude that the source of these pick-up ions is the moon. We argue that due to the impinging solar wind, atoms are sputtered off the lunar surface, ionized in the sputtering process or by ensuing photoionization and picked up by the solar wind.

Models for Cometary Comae Containing Negative Ions

NASA Technical Reports Server (NTRS)

Cordiner, M. A.; Charnley, S. B.

2012-01-01

The presence of negative ions (anions) in cometary comae is known from Giotto mass spectrometry of IP/Halley. The anions O(-), OH(-), C(-), CH(-) and CN(-) have been detected, as well as unidentified anions with masses 22-65 and 85-110 amu [I]. Organic molecular anions such as C4H(-) and C6H(-) are known to have a significant impact on the charge balance of interstellar clouds and circumstellar envelopes and have been shown to act as catalysts for the gas phase synthesis of larger hydrocarbon molecules in the ISM, but their importance in cometary comae has not yet been fully explored. We present details of our new models for the chemistry of cometary comae that include atomic and molecular anions. We calculate the impact of these anions on the charge balance and examine their importance for cometary coma chemistry.

Charge exchange in solar wind-cometary interactions

NASA Technical Reports Server (NTRS)

Gombosi, T. I.; Horanyi, M.; Kecskemety, K.; Cravens, T. E.; Nagy, A. F.

1983-01-01

A simple model of a cometary spherically symmetrical atmosphere and ionosphere is considered. An analytic solution of the governing equations describing the radial distribution of the neutral and ion densities is found. The new solution is compared to the well-known solution of the equations containing only ionization terms. Neglecting recombination causes a significant overestimate of the ion density in the vicinity of the comet. An axisymmetric model of the solar wind-cometary interaction is considered, taking into account the loss of solar wind ions due to charge exchange. The calculations predict that for active comets, solar wind absorption due to charge exchange becomes important at a few thousand kilometers from the nucleus, and a surface separating the shocked solar wind from the cometary ionosphere develops in this region. These calculations are in reasonable agreement with the few observations available for the ionopause location at comets.

Near Earth Inner-Source and Interstellar Pickup Ions Observed with the Hot Plasma Composition Analyzer of the Magnetospheric Multiscale Mission Mms-Hpca

NASA Astrophysics Data System (ADS)

Gomez, R. G.; Fuselier, S. A.; Mukherjee, J.; Gonzalez, C. A.

2017-12-01

Pickup ions found near the earth are generally picked up in the rest frame of the solar wind, and propagate radially outward from their point of origin. While propagating, they simultaneously gyrate about the magnetic field. Pickup ions come in two general populations; interstellar and inner source ions. Interstellar ions originate in the interstellar medium, enter the solar system in a neutral charge state, are gravitationally focused on the side of the sun opposite their arrival direction and, are ionized when they travel near the sun. Inner-source ions originate at a location within the solar system and between the sun and the observation point. Both pickup ion populations share similarities in composition and charge states, so measuring of their dynamics, using their velocity distribution functions, f(v)'s, is absolutely essential to distinguishing them, and to determining their spatial and temporal origins. Presented here will be the results of studies conducted with the four Hot Plasma Composition Analyzers of the Magnetospheric Multiscale Mission (MMS-HPCA). These instruments measure the full sky (4π steradians) distribution functions of near earth plasmas at a 10 second cadence in an energy-to-charge range 0.001-40 keV/e. The instruments are also capable of parsing this combined energy-solid angle phase space with 22.5° resolution polar angle, and 11.25° in azimuthal angle, allowing for clear measurement of the pitch angle scattering of the ions.

In situ energetic particle observations at Comet Halley recorded by instrumentation aboard the Giotto and VEGA 1 missions

NASA Astrophysics Data System (ADS)

McKenna-Lawlor, S.; Daly, P.; Kirsch, E.; Wilken, B.; O'Sullivan, D.; Thompson, A.; Kecskemety, K.; Somogyi, A.; Coates, A.

1989-04-01

Energetic particle data on quasi-periodic variations of cometary ion fluxes recorded by instrumentation aboard the Vega 1 and Giotto spacecraft during March 1986 are compared. It is suggested that the ion fluxes measured by the Giotto EPONA instrument were of the water group. Large fluxes of electrons and ions recorded by the EPONA instrument in the magnetic cavity appear to be cometary in origin.

Mechanical and electrostatic experiments with dust particles collected in the inner coma of comet 67P by COSIMA onboard Rosetta.

PubMed

Hilchenbach, Martin; Fischer, Henning; Langevin, Yves; Merouane, Sihane; Paquette, John; Rynö, Jouni; Stenzel, Oliver; Briois, Christelle; Kissel, Jochen; Koch, Andreas; Schulz, Rita; Silen, Johan; Altobelli, Nicolas; Baklouti, Donia; Bardyn, Anais; Cottin, Herve; Engrand, Cecile; Fray, Nicolas; Haerendel, Gerhard; Henkel, Hartmut; Höfner, Herwig; Hornung, Klaus; Lehto, Harry; Mellado, Eva Maria; Modica, Paola; Le Roy, Lena; Siljeström, Sandra; Steiger, Wolfgang; Thirkell, Laurent; Thomas, Roger; Torkar, Klaus; Varmuza, Kurt; Zaprudin, Boris

2017-07-13

The in situ cometary dust particle instrument COSIMA (COmetary Secondary Ion Mass Analyser) onboard ESA's Rosetta mission has collected about 31 000 dust particles in the inner coma of comet 67P/Churyumov-Gerasimenko since August 2014. The particles are identified by optical microscope imaging and analysed by time-of-flight secondary ion mass spectrometry. After dust particle collection by low speed impact on metal targets, the collected particle morphology points towards four families of cometary dust particles. COSIMA is an in situ laboratory that operates remotely controlled next to the comet nucleus. The particles can be further manipulated within the instrument by mechanical and electrostatic means after their collection by impact. The particles are stored above 0°C in the instrument and the experiments are carried out on the refractory, ice-free matter of the captured cometary dust particles. An interesting particle morphology class, the compact particles, is not fragmented on impact. One of these particles was mechanically pressed and thereby crushed into large fragments. The particles are good electrical insulators and transform into rubble pile agglomerates by the application of an energetic indium ion beam during the secondary ion mass spectrometry analysis.This article is part of the themed issue 'Cometary science after Rosetta'. © 2017 The Author(s).

Coulomb thermal properties and stability of the Io plasma torus

NASA Technical Reports Server (NTRS)

Barbosa, D. D.; Coroniti, F. V.; Eviatar, A.

1983-01-01

Coulomb collisional energy exchange rates are computed for a model of the Io plasma torus consisting of newly created pickup ions, a background of thermally degraded intermediary ions, and a population of cooler electrons. The electrons are collisionally heated by both the pickup ions and background ions and are cooled by electron impact excitation of plasma ions which radiate in the EUV. It is found that a relative concentration of S III pickup ions forbidden S III/electrons = 0.1 with a temperature of 340 eV can deliver energy to the electrons at a rate of 3 x 10 to the -13th erg/cu cm per sec, sufficient to power the EUV emissions in the Io torus. The model predicts a background ion temperature Ti of about 53 eV and an electron temperature Te of about 5.5 eV on the basis of steady-state energy balance relations at Coulomb rates. The model also predicts electron temperature fluctuations at the 30 percent level on a time scale of less than 11 hours, consistent with recent observations of this phenomenon.

The Velocity Distribution Of Pickup He+ Measured at 0.3 AU by MESSENGER

NASA Astrophysics Data System (ADS)

Gershman, Daniel J.; Fisk, Lennard A.; Gloeckler, George; Raines, Jim M.; Slavin, James A.; Zurbuchen, Thomas H.; Solomon, Sean C.

2014-06-01

During its interplanetary trajectory in 2007-2009, the MErcury Surface, Space ENvrionment, GEochemistry, and Ranging (MESSENGER) spacecraft passed through the gravitational focusing cone for interstellar helium multiple times at a heliocentric distance R ≈ 0.3 AU. Observations of He+ interstellar pickup ions made by the Fast Imaging Plasma Spectrometer sensor on MESSENGER during these transits provide a glimpse into the structure of newly formed inner heliospheric pickup-ion distributions. This close to the Sun, these ions are picked up in a nearly radial interplanetary magnetic field. Compared with the near-Earth environment, pickup ions observed near 0.3 AU will not have had sufficient time to be energized substantially. Such an environment results in a nearly pristine velocity distribution function that should depend only on pickup-ion injection velocities (related to the interstellar gas), pitch-angle scattering, and cooling processes. From measured energy-per-charge spectra obtained during multiple spacecraft observational geometries, we have deduced the phase-space density of He+ as a function of magnetic pitch angle. Our measurements are most consistent with a distribution that decreases nearly monotonically with increasing pitch angle, rather than the more commonly modeled isotropic or hemispherically symmetric forms. These results imply that pitch-angle scattering of He+ may not be instantaneous, as is often assumed, and instead may reflect the velocity distribution of initially injected particles. In a slow solar wind stream, we find a parallel-scattering mean free path of λ || ~ 0.1 AU and a He+ production rate of ~0.05 m-3 s-1 within 0.3 AU.

Derivation Of Local Interstellar Medium Parame-ters From Pickup Ion Observations

NASA Astrophysics Data System (ADS)

Gloeckler, G.; Geiss, G.

2002-05-01

Pickup ions provide us with a new tool to probe remote regions in and beyond the heliosphere. Comprehensive and continuous meas-urements of H, He, C, N, O, and Ne, especially with the Solar Wind Ion Composition Spectrometer (SWICS) on both Ulysses and ACE, have given us a wealth of data that are being used to infer the chemi-cal and physical properties of the Local Interstellar Cloud (LIC). Knowledge gained from this work will be reviewed with an emphasis on LIC characteristics, such as the isotopic and elemental composi-tion of the LIC gas, its density, temperature and ionization state, and limits on the strength of the LIC magnetic field. Using pressure-balance arguments and the latest values of the LIC parameters we will estimate the location of the heliospheric termination shock. Future directions for further dramatic advances in pickup ion meas-urements will also be discussed.

A survey of bimolecular ion-molecule reactions for use in modeling the chemistry of planetary atmospheres, cometary comae, and interstellar clouds

NASA Technical Reports Server (NTRS)

Anicich, V. G.; Huntress, W. T., Jr.

1986-01-01

All bimolecular positive ion-molecule reactions reported from 1965 to 1985 for temperatures below 1000 K are included in the present survey of those ion-molecule reactions pertinent to the chemistries of planetary atmospheres, cometary comae, and interstellar clouds. This survey is intended as an update of the first, by Huntress (1977). The tabular presentation is organized according to reactant ion, with cross-references for both the ionic and the neutral reactants as well as the ionic and neutral products.

Comets: Gases, ices, grains and plasma

NASA Technical Reports Server (NTRS)

Wilkening, L. L.

1981-01-01

The program and abstracts of the 97 papers delivered at the colloquium are presented. Cometary nuclei, comet dust, the coma, ion tails, several comet missions, and cometary origin and evolution were discussed.

Anisotropy of the He+, C+, N+, O+, and Ne+ Pickup Ion Velocity Distribution Function

NASA Astrophysics Data System (ADS)

Drews, Christian; Berger, Lars; Taut, Andreas; Wimmer-Schweingruber, Robert F.

2016-04-01

Interstellar and inner-source PickUp Ions (PUIs) are produced by the ionization of neutral atoms that originate either outside or inside the heliosphere. Just after the ionization, the singly charged ions are picked up by the magnetized solar wind plasma and develop strong anisotropic toroidal features in their Velocity Distribution Functions (VDF). As the plasma parcel moves outward with the solar wind, the pickup-ion VDF gets more and more affected by resonant wave-particle interactions, changing heliospheric conditions, and plasma drifts, which lead to a gradual isotropization of the pickup ion VDF. Past investigations of the pickup ion torus distribution were limited to He+ pickup ions at 1 Astronomical Unit (AU). The aim of this study is to quantify the state of anisotropy of the He+, C+, N+, O+, and Ne+ pickup ion VDF at 1 AU. Changes between the state of anisotropy between PUIs of different mass-per charges can be used to estimate the significance of resonant wave particle interactions for the isotropization of their VDF, and to investigate the numerous simplifications that are generally made for the description of the phase space transport of PUIs. Pulse height analysis data by the PLAsma and SupraThermal Ion Composition instrument (PLASTIC) on board the Solar Terrestrial RElations Observatory Ahead (STEREO A) is used to obtain velocity spectra of He+, C+, N+, O+, and Ne+ relative to the solar wind, f(wsw). The wsw-spectra are sorted by two different configurations of the local magnetic field - one in which the torus distribution lies within the instrument's aperture, φ⊥, and one in which the torus distribution lies exclusively outside the instrument's field of view, φ∥. The ratio of the PUI spectra between φ⊥ and φ∥ is used to determine the degree of anisotropy of the PUI VDF. The data shows that the formation of a torus distribution at 1 AU is significantly more prominent for O+ (and N+) than for He+ (and Ne+). This cannot be explained by resonant wave-particle interactions as the sole mechanism for the isotropization of the PUI VDF. The anisotropy of the O+ VDF compared to He+ is highly fluctuating but consistently higher over an observation period of 6 years and therefore unlikely to be related to either specific heliospheric conditions or solar activity variations. To our surprise, we also found a clear signature of a C+ torus distribution at 1 AU very similar to the one of He+, although as an inner-source PUI, C+ should have a considerably different spectral and spatial injection pattern than interstellar PUIs.

Cometary jets in interaction with the solar wind: a hybrid simulation study

NASA Astrophysics Data System (ADS)

Wiehle, Stefan; Motschmann, Uwe; Gortsas, Nikolaos; Mueller, Joachim; Kriegel, Hendrik; Koenders, Christoph; Glassmeier, Karl-Heinz

The effect of a cometary jet on the solar wind interaction is studied using comet 67P/Churyumov-Gerasimenko as case study. This comet is the target of the Rosetta-mission which will arrive in 2014. Observations suggest that cometary outgassing is confined to only a few percent of the cometary surface; thus, the measurement of jets is expected. Most former comet simulations did not attend to this fact and used an isotropic outgassing scheme or simplified outgassing patterns. Here, a single sun-facing jet is set to be the only source of cometary gas produc-tion. Using an analytic profile, this outgassing jet was implemented in a hybrid simulation code which treats protons and cometary heavy ions as particles and electrons as massless fluid. In a simulation series, the geometric parameters of the jet were varied to study the effect of different opening angles while the integrated outgassing rate remained constant. It was shown that the resulting solar wind interaction is highly dependent on the geometry of the jet. The plasma-structures like the solar wind pile-up found in the situation with isotropic outgassing are moved more and more sunward as the opening angle of the jet decreases. Furthermore, the cometary ion tail shows some kind of splitting which is not known from isotropic models.

Preshock region acceleration of implanted cometary H(+) and O(+)

NASA Astrophysics Data System (ADS)

Gombosi, T. I.

1988-01-01

A self-consistent, three-fluid model of plasma transport and implanted ion acceleration in the unshocked solar wind is presented. The solar wind plasma is depleted by charge exchange with the expanding cometary exosphere, while implanted protons and heavy ions are produced by photoionization and charge transfer and lost by charge exchange. A generalized transport equation describing convection, adiabatic and diffusive velocity change, and the appropriate production terms is used to describe the evolution of the two cometary ion components, while the moments of the Boltzmann equation are used to calculate the solar wind density and pressure. The flow velocity is obtained self-consistently by combining the conservation equations of the three ion species. The results imply that second-order Fermi acceleration can explain the implanted spectra observed in the unshocked solar wind. Comparison of measured and calculated distribution indicates that spatial diffusion of implanted ions probably plays an important role in forming the energetic particle environment in the shock vicinity.

Comparative pick-up ion distributions at Mars and Venus: Consequences for atmospheric deposition and escape

NASA Astrophysics Data System (ADS)

Curry, Shannon M.; Luhmann, Janet; Ma, Yingjuan; Liemohn, Michael; Dong, Chuanfei; Hara, Takuya

2015-09-01

Without the shielding of a substantial intrinsic dipole magnetic field, the atmospheres of Mars and Venus are particularly susceptible to similar atmospheric ion energization and scavenging processes. However, each planet has different attributes and external conditions controlling its high altitude planetary ion spatial and energy distributions. This paper describes analogous test particle simulations in background MHD fields that allow us to compare the properties and fates, precipitation or escape, of the mainly O+ atmospheric pick-up ions at Mars and Venus. The goal is to illustrate how atmospheric and planetary scales affect the upper atmospheres and space environments of our terrestrial planet neighbors. The results show the expected convection electric field-related hemispheric asymmetries in both precipitation and escape, where the degree of asymmetry at each planet is determined by the planetary scale and local interplanetary field strength. At Venus, the kinetic treatment of O+ reveals a strong nightside source of precipitation while Mars' crustal fields complicate the simple asymmetry in ion precipitation and drive a dayside source of precipitation. The pickup O+ escape pattern at both Venus and Mars exhibits low energy tailward escape, but Mars exhibits a prominent, high energy 'polar plume' feature in the hemisphere of the upward convection electric field while the Venus ion wake shows only a modest poleward concentration. The overall escape is larger at Venus than Mars (2.1 ×1025 and 4.3 ×1024 at solar maximum, respectively), but the efficiency (likelihood) of O+ escaping is 2-3 times higher at Mars. The consequences of these comparisons for pickup ion related atmospheric energy deposition, loss rates, and detection on spacecraft including PVO, VEX, MEX and MAVEN are considered. In particular, both O+ precipitation and escape show electric field controlled asymmetries that grow with energy, while the O+ fluxes and energy spectra at selected spatial locations show characteristic signatures of the pickup related acceleration and precipitation.

Plasma wave observations at comet giacobini-zinner.

PubMed

Scarf, F L; Coroniti, F V; Kennel, C F; Gurnett, D A; Ip, W H; Smith, E J

1986-04-18

The plasma wave instrument on the International Cometary Explorer (ICE) detected bursts of strong ion acoustic waves almost continuously when the spacecraft was within 2 million kilometers of the nucleus of comet Giacobini-Zinner. Electromagnetic whistlers and low-level electron plasma oscillations were also observed in this vast region that appears to be associated with heavy ion pickup. As ICE came closer to the anticipated location of the bow shock, the electromagnetic and electrostatic wave levels increased significantly, but even in the midst of this turbulence the wave instrument detected structures with familiar bow shock characteristics that were well correlated with observations of localized electron heating phenomena. Just beyond the visible coma, broadband waves with amplitudes as high as any ever detected by the ICE plasma wave instrument were recorded. These waves may account for the significant electron heating observed in this region by the ICE plasma probe, and these observations of strong wave-particle interactions may provide answers to longstanding questions concerning ionization processes in the vicinity of the coma. Near closest approach, the plasma wave instrument detected broadband electrostatic noise and a changing pattern of weak electron plasma oscillations that yielded a density profile for the outer layers of the cold plasma tail. Near the tail axis the plasma wave instrument also detected a nonuniform flux of dust impacts, and a preliminary profile of the Giacobini-Zinner dust distribution for micrometer-sized particles is presented.

Comparison of picked-up protons and water group ions upstream of Comet Halley's bow shock

NASA Technical Reports Server (NTRS)

Neugebauer, M.; Coates, A. J.; Neubauer, F. M.

1990-01-01

The similarities and differences between the picked-up cometary protons and water-group (WG) ions upstream of the bow shock of Comet Halley are examined using measurements obtained by the ion mass spectrometer and plasma analyzer experiments on board Giotto. It was found that the dependencies of the pitch angle and the energy diffusion rates of the cometary protons and WG ions on the ion densities and on the angle alpha between the interplanetary field and the solar wind velocity vector were very different. This finding could not be explained in terms of presently available theories and models.

Seasonal variation of Martian pick-up ions: Evidence of breathing exosphere

NASA Astrophysics Data System (ADS)

Yamauchi, M.; Hara, T.; Lundin, R.; Dubinin, E.; Fedorov, A.; Sauvaud, J.-A.; Frahm, R. A.; Ramstad, R.; Futaana, Y.; Holmstrom, M.; Barabash, S.

2015-12-01

The Mars Express (MEX) Ion Mass Analyser (IMA) found that the detection rate of the ring-like distribution of protons in the solar wind outside of the bow shock to be quite different between Mars orbital summer (around perihelion) and orbital winter (around aphelion) for four Martian years, while the north-south asymmetry is much smaller than the perihelion-aphelion difference. Further analyses using eight years of MEX/IMA solar wind data between 2005 and 2012 has revealed that the detection frequency of the pick-up ions originating from newly ionized exospheric hydrogen with certain flux strongly correlates with the Sun-Mars distance, which changes approximately every two years. Variation due to the solar cycle phase is not distinguishable partly because this effect is masked by the seasonal variation under the MEX capability of plasma measurements. This finding indicates that the variation in solar UV has a major effect on the formation of the pick-up ions, but this is not the only controlling factor.

VOYAGER OBSERVATIONS OF MAGNETIC WAVES DUE TO NEWBORN INTERSTELLAR PICKUP IONS: 2–6 au

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aggarwal, Poornima; Taylor, David K.; Smith, Charles W.

We report observations by the Voyager 1 and 2 spacecraft of low-frequency magnetic waves excited by newborn interstellar pickup ions H{sup +} and He{sup +} during 1978–1979 when the spacecraft were in the range from 2 to 6.3 au. The waves have the expected association with the cyclotron frequency of the source ions, are left-hand polarized in the spacecraft frame, and have minimum variance directions that are quasi-parallel to the local mean magnetic field. There is one exception to this in that one wave event that is excited by pickup H{sup +} is right-hand polarized in the spacecraft frame, butmore » similar exceptions have been reported by Cannon et al. and remain unexplained. We apply the theory of Lee and Ip that predicts the energy spectrum of the waves and then compare growth rates with turbulent cascade rates under the assumption that turbulence acts to destroy the enhanced wave activity and transport the associated energy to smaller scales where dissipation heats the background plasma. As with Cannon et al., we find that the ability to observe the waves depends on the ambient turbulence being weak when compared with growth rates, thereby allowing sustained wave growth. This analysis implies that the coupled processes of pitch-angle scattering and wave generation are continuously associated with newly ionized pickup ions, despite the fact that the waves themselves may not be directly observable. When waves are not observed, but wave excitation can be argued to be present, the wave energy is simply absorbed by the turbulence at a rate that prevents significant accumulation. In this way, the kinetic process of wave excitation by scattering of newborn ions continues to heat the plasma without producing observable wave energy. These findings support theoretical models that invoke efficient scattering of new pickup ions, leading to turbulent driving in the outer solar wind and in the IBEX ribbon beyond the heliopause.« less

Wind Enhanced Escape, Ion Pickup and the Evolution of Water on Mars

NASA Technical Reports Server (NTRS)

Hartle, Richard

1999-01-01

Preferential loss of hydrogen over deuterium from Mars has produced a deuterium rich atmosphere possessing a D/B ratio 5.2 times that of terrestrial water. Rayleigh fractionation is applied, constrained by the deuterium enrichment factor, to determine the magnitudes of ancient and present water reservoirs on the planet. The dominant lose mechanisms of R and D from the current atmosphere are thought to be thermal escape and solar wind ion pickup of the neutral and ion forms of theme constituents, respectively. During an earlier martian epoch, only thermal escape was significant because Mars had a terrestrial sized magnetosphere that protected the atmosphere from solar wind scavenging processes. The magnitudes of present and ancient water reservoirs are estimated when thermal escape is considered alone and subsequently when the effects of ion pickup are added. The escape fluxes of R and D are significantly increased above the respective Jeans fluxes when the effects of thermospheric winds and planetary rotation are accounted for at the exobase. Such wind enhanced escape also increases as the mass of an escaping constituent increases; thus, the increase in the escape flux of D is greater than that of H. When the fractionation process is also constrained by the D/H ratio observed in hydrous minerals of SNC meteorites, an ancient crustal reservoir of Martian water in derived, tens of meters in global-equivalent depth, considerably exceeding that obtained with no winds. The reservoir becomes even larger when ion pickup processes are added.

Pickup Ions at Dione and Enceladus

NASA Technical Reports Server (NTRS)

Sittler, E.; Johnson, R. E.; Jurac, S.; Richardson, J.; McGrath, M.; Crary, F.; Young, D.; Nordholt, J. E.

2002-01-01

Voyager images of the icy satellites of Saturn, Dione and Enceladus, suggest they have been geologically active and are not only composed of ice. Recent observations by HST have shown the presence of ozone at both Dione and Rhea which also implies the presence of molecular oxygen at these bodies. The Cassini Plasma Spectrometer (CAPS) will provide the capability to determine the global composition of these bodies by measuring the pickup ions produced by the ionization of their sputter produced atmospheres. We will present a model of these atmospheres and associated pickup ions and demonstrate CAPS ability to distinguish the freshly produced picked up ions from the ambient plasma. Such ions are expected to form a ring distribution that will have a uniquely different energy-angle dependence than the ambient plasma ions. In the case of Dione we expect the potential for a moderate strength interaction for which both Voyager 1 and Pioneer 11 spacecraft measured ion cyclotron waves centered on the Dione L shell and near the equatorial plane. Since Enceladus may be the source of the E-ring, some surprises may be encountered during its close encounter with the Cassini spacecraft. In the case of Dione we will show that a wake pass at 500 km altitude is more than an order of magnitude better than an upstream pass at 500 km altitude. Pickup ion detection for minor ion species such as NH3+ is possible for 500 km altitude wake pass but not for a 500 km altitude upstream pass at closest approach. For navigation reasons a 100 km pass is not allowed and therefore it is essential to have a wake pass to maximize the science return for a targeted flyby with Dione. The CAPS observations when combined with magnetometer, plasma wave and energetic particle observations will allow us to estimate the source of ions into Saturn's magnetosphere due to these two bodies and to characterize the nature of the interaction with Saturn's magnetosphere.

Modeling and Observation of Interstellar He+ Pickup Ions in the Inner Heliosphere

NASA Astrophysics Data System (ADS)

Chen, Junhong

Interstellar pickup ions constitute a charged particle population that originates from interstellar neutrals inside the heliosphere. They are produced by photoionization, charge exchange with solar wind ions, and electron impact ionization (EI). Once ionized, they are picked up by the interplanetary magnetic field (IMF) and rapidly swept outward with the solar wind. Typically, pickup ion distributions have been described in terms of a velocity distribution function that evolves through fast pitch angle scattering followed by adiabatic cooling during radial transport in the reference frame of the solar wind [e.g., Vasyliunas & Siscoe, 1976, VS76 hereafter]. In the VS76 model, the slope of the isotropic velocity distributions is controlled by the combination of the ionization rate and the cooling process. Thus far, for the cooling index that relates the slope of the velocity distribution to the radial transport and expansion of the pickup ions a constant value of 3/2 has been widely used. The implicit assumptions to arrive at this value are immediate PUI isotropization due to pitch angle scattering and solar wind expansion with the square of the distance from the Sun. Any experimental determination of the cooling index depends on the knowledge of the ionization rate and its spatial variation, as well as solar wind and interplanetary conditions. In this thesis, we study their influences on the PUI cooling index and separate them by making use of the two complementary helium PUI data sets from SWICS instrument on the ACE spacecraft, and PLASTIC instrument on STEREO spacecraft. We use the pickup ion observations from ACE SIWCS in the last solar cycle to determine the cooling index, and the possible effects of the electron impact ionization on the determination of the cooling index. With pickup ion observations from STEREO PLASTIC, we determine how solar wind expansion patterns affect the cooling index. We find that the cooling index varies substantially with solar activity and suspect that these variations may be due to the influence of electron impact ionization, solar wind structures, and slow pitch angle scattering. Electron impact ionization, which does not scale as 1/r 2, is shown to have negligible influence on the cooling index and its variations. However, the effects of solar wind compression and rarefaction regions are found to be important. Comparisons of the pickup ion cooling behavior in the compression and rarefaction regions show that the radial solar wind expansion behaviors that differer from the usual 1/r 2 scaling may play the leading roles in the observed variations. A kinetic model of PUI is used to quantitatively describe their behavior in co-rotating interaction regions (CIR). The simulated distributions mimic closely the observed variations in the cooling behavior of PUIs in these regions. In addition, suprathermal tails appear to emerge from the PUI distributions inside compression regions, which provide further evidence that some particles of this population are accelerated locally in CIR compression regions even in the absence of shocks.

Complete positive ion, electron, and ram negative ion measurements near Comet Halley (COPERNIC) plasma experiment for the European Giotto Mission

NASA Technical Reports Server (NTRS)

Lin, Robert P.

1988-01-01

Participation of U.S. scientists on the COPERNIC (COmplete Positive ions, Electrons and Ram Negative Ion measurements near Comet Halley) plasma experiment on the Giotto mission is described. The experiment consisted of two detectors: the EESA (electron electrostatic analyzer) which provided three-dimensional measurements of the distribution of electrons from 10 eV to 30 keV, and the PICCA (positive ion cluster composition analyzer) which provided mass analysis of positively charged cold cometary ions from mass 10 to 210 amu. In addition, a small 3 deg wide sector of the EESA looking in the ram direction was devoted to the detection of negatively charged cold cometary ions. Both detectors operated perfectly up to near closest approach (approx. 600 km) to Halley, but impacts of dust particles and neutral gas on the spacecraft contaminated parts of the data during the last few minutes. Although no flight hardware was fabricated in the U.S., The U.S. made very significant contributions to the hardware design, ground support equipment (GSE) design and fabrication, and flight and data reduction software required for the experiment, and also participated fully in the data reduction and analysis, and theoretical modeling and interpretation. Cometary data analysis is presented.

Ion composition at comet 67P near perihelion: Rosetta/ROSINA measurements and modeling

NASA Astrophysics Data System (ADS)

Beth, Arnaud; Altwegg, Kathrin; Balsiger, Hans; Berthelier, Jean-Jacques; Calmonte, Ursina; Combi, Michael R.; De Keyser, Johan; Dhooghe, Frederik; Fiethe, Björn; Fuselier, Stephen; Galand, Marina; Gasc, Sébastien; Gombosi, T. I.; Hansen, Kenneth C.; Hässig, Myrtha; Héritier, Kévin; Kopp, Ernest; Le Roy, Léna; Peroy, Solène; Rubin, Martin; Sémon, Thierry; Tzou, Chia-Yu; Vigren, Erik

2016-10-01

On August 13th, 2015, comet 67P/Churyumov-Gerasimenko reached its perihelion at 1.24 AU, a milestone for its cometary activity observed by the European Space Agency's Rosetta spacecraft which arrived in August 2014. The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA)/Comet Pressure Sensor (COPS) instrument onboard Rosetta measured local outgassing rates over 1028 molecules.s-1 in summer 2015. In the meantime, the ROSINA/Double Focusing Mass Spectrometer (DFMS) instrument measured the ion composition in the coma which was expected to be more diversified than during the early phase of the mission. Indeed, the increase in the cometary activity is expected to trigger new chemical pathways, yielding the formation of new cometary ions, other than the major water ions observed at larger heliocentric distances. Such new ion species can be produced from minor neutral species, such as those with proton affinity higher than that of water. This includes NH4+ whose detection has been recently reported (Beth et al., 2016).In this study, we propose to investigate other ion species during the perihelion period by:- analysing DFMS data to find any signature of substantial ion species,- modeling the ionosphere of 67P by driving the model with the neutral densities measured by DFMS and COPS to support or constrain the absence or the presence of these ion species,- discussing any discrepancy between observations and simulations.

A survey of bimolecular ion-molecule reactions for use in modeling the chemistry of planetary atmospheres, cometary comae, and interstellar clouds - 1993 supplement

NASA Technical Reports Server (NTRS)

Anicich, V. G.

1993-01-01

This is a supplement to a previous paper (Anicich & Huntress 1986). It is a survey of bimolecular positive ion-molecule reactions with potential importance to the chemistry of planetary atmospheres, cometary comae, and interstellar clouds. This supplement covers the literature from 1986 through 1991, with some additional citations missed in the original survey. Over 200 new citations are included. A table of reactions is listed by reactant ion, and cross-references are provided for both ionic and neutral reactants and also for both ionic and neutral products.

Rogue Waves in Multi-Ion Cometary Plasmas

NASA Astrophysics Data System (ADS)

Sreekala, G.; Manesh, M.; Neethu, T. W.; Anu, V.; Sijo, S.; Venugopal, C.

2018-01-01

The effect of pair ions on the formation of rogue waves in a six-component plasma composed of two hot and one colder electron component, hot ions, and pair ions is studied. The kappa distribution, which provides an unambiguous replacement for a Maxwellian distribution in space plasmas, is connected with nonextensive statistical mechanics and provides a continuous energy spectrum. Hence, the colder and one component of the hotter electrons is modeled by kappa distributions and the other hot electron component, by a q-nonextensive distribution. It is found that the rogue wave amplitude is different for various pair-ion components. The magnitude, however, increases with increasing spectral index and nonextensive parameter q. These results may be useful in understanding the basic characteristics of rogue waves in cometary plasmas.

COSIMA-Rosetta calibration for in situ characterization of 67P/Churyumov-Gerasimenko cometary inorganic compounds

NASA Astrophysics Data System (ADS)

Krüger, Harald; Stephan, Thomas; Engrand, Cécile; Briois, Christelle; Siljeström, Sandra; Merouane, Sihane; Baklouti, Donia; Fischer, Henning; Fray, Nicolas; Hornung, Klaus; Lehto, Harry; Orthous-Daunay, Francois-Régis; Rynö, Jouni; Schulz, Rita; Silén, Johan; Thirkell, Laurent; Trieloff, Mario; Hilchenbach, Martin

2015-11-01

COmetary Secondary Ion Mass Analyzer (COSIMA) is a time-of-flight secondary ion mass spectrometry (TOF-SIMS) instrument on board the Rosetta space mission. COSIMA has been designed to measure the composition of cometary dust particles. It has a mass resolution m/Δm of 1400 at mass 100 u, thus enabling the discrimination of inorganic mass peaks from organic ones in the mass spectra. We have evaluated the identification capabilities of the reference model of COSIMA for inorganic compounds using a suite of terrestrial minerals that are relevant for cometary science. Ground calibration demonstrated that the performances of the flight model were similar to that of the reference model. The list of minerals used in this study was chosen based on the mineralogy of meteorites, interplanetary dust particles and Stardust samples. It contains anhydrous and hydrous ferromagnesian silicates, refractory silicates and oxides (present in meteoritic Ca-Al-rich inclusions), carbonates, and Fe-Ni sulfides. From the analyses of these minerals, we have calculated relative sensitivity factors for a suite of major and minor elements in order to provide a basis for element quantification for the possible identification of major mineral classes present in the cometary particles.

Cassini CAPS Identification of Pickup Ion Compositions at Rhea

NASA Astrophysics Data System (ADS)

Desai, R. T.; Taylor, S. A.; Regoli, L. H.; Coates, A. J.; Nordheim, T. A.; Cordiner, M. A.; Teolis, B. D.; Thomsen, M. F.; Johnson, R. E.; Jones, G. H.; Cowee, M. M.; Waite, J. H.

2018-02-01

Saturn's largest icy moon, Rhea, hosts a tenuous surface-sputtered exosphere composed primarily of molecular oxygen and carbon dioxide. In this Letter, we examine Cassini Plasma Spectrometer velocity space distributions near Rhea and confirm that Cassini detected nongyrotropic fluxes of outflowing CO2+ during both the R1 and R1.5 encounters. Accounting for this nongyrotropy, we show that these possess comparable along-track densities of ˜2 × 10-3 cm-3. Negatively charged pickup ions, also detected during R1, are surprisingly shown as consistent with mass 26 ± 3 u which we suggest are carbon-based compounds, such as CN-, C2H-, C2-, or HCO-, sputtered from carbonaceous material on the moon's surface. The negative ions are calculated to possess along-track densities of ˜5 × 10-4 cm-3 and are suggested to derive from exogenic compounds, a finding consistent with the existence of Rhea's dynamic CO2 exosphere and surprisingly low O2 sputtering yields. These pickup ions provide important context for understanding the exospheric and surface ice composition of Rhea and of other icy moons which exhibit similar characteristics.

The effect of mass loading outside cometary bow shock for the plasma and wave measurements in the coming cometary missions

NASA Astrophysics Data System (ADS)

Sagdeev, R. Z.; Shapiro, V. D.; Shevchenko, V. I.; Szego, K.

1987-02-01

The neutral gas emitted by comets is partly photoionized along its path. The interaction of the ions with the solar wind leads to observable particle and wave effects in the ambient plasma. These are described in the present paper.

LADEE/LDEX observations of lunar pickup ion distribution and variability

NASA Astrophysics Data System (ADS)

Poppe, A. R.; Halekas, J. S.; Szalay, J. R.; Horányi, M.; Levin, Z.; Kempf, S.

2016-04-01

We report fortuitous observations of low-energy lunar pickup ion fluxes near the Moon while in the solar wind by the Lunar Dust Experiment (LDEX) on board the Lunar Atmosphere and Dust Environment Explorer (LADEE). We describe the method of observation and the empirical calibration of the instrument for ion observations. LDEX observes several trends in the exospheric ion production rate, including a scale height of approximately 100 km, a positive, linear correlation with solar wind flux, and evidence of a slight enhancement near 7-8 h local time. We compare the LDEX observations to both LADEE Neutral Mass Spectrometer ion mode observations and theoretical models. The LDEX data are best fit by total exospheric ion production rates of ≈6 × 103 m-3 s-1 with dominant contributions from Al+, CO+, and Ar+, although the LDEX data suggest that the aluminum neutral density and corresponding ion production rate are lower than predicted by recent models.

Densities and abundances of hot cometary ions in the coma of P/Halley

NASA Technical Reports Server (NTRS)

Neugebauer, M.; Goldstein, R.; Goldstein, B. E.; Fuselier, S. A.; Balsiger, H.; Ip, W.-H.

1991-01-01

On its flight by P/Halley, the Giotto spacecraft carried a High Energy Range Spectrometer (HERS) for measuring the properties of cometary ions picked up by the solar wind in the nearly collisionless regions of the coma. Preliminary estimates of the ion densities observed by HERS were reevaluated and extended; density profiles along the Giotto trajectory are presented for 13 values of ion mass/charge. Comparison with the physical-chemical model of the interaction of sunlight and the solar wind with the comet by other researchers reveals that, with the exception of protons and H2(+), all ion densities were at least an order of magnitude higher than predicted. The high ion densities cannot be explained on the basis of compression of the plasma, but require additional or stronger ionization mechanisms. Ratios of the densities of different ion species reveal an overabundance of carbonaceous material and an underabundance of H2(+) compared to the predictions of the Schmidt. While the densities of solar wind ions (H(+) and He(++)) changed sharply across a magnetic discontinuity located 1.35(10)(exp 5) km from the comet, this feature, which has been called both the 'cometopause' and the 'magnetic pileup boundary' was barely distinguishable in the density profiles of hot cometary ions. This result is consistent with the interpretation that the magnetic pileup boundary detected by Giotto was caused by a discontinuity in the solar wind and is not an intrinsic feature of the interaction of the solar wind with an active comet.

Ultraviolet spectrophotometry of comet Giacobini-Zinner during the ICE encounter. [International Cometary Explorer (ICE)

NASA Technical Reports Server (NTRS)

Ahearn, Michael F.; Mcfadden, Lucy A.; Feldman, Paul D.; Boehnhardt, Hermann; Rahe, Juergen; Festou, Michael; Brandt, John C.; Maran, Stephen P.; Niedner, Malcom B.; Smith, Andrew M.

1986-01-01

The IUE spectrophotometry of Comet P/Giacobini-Zinner was acquired in support of the International Cometary Explorer (ICE) mission. The abundances (or upper limits) of UV-active species were calculated. During the ICE encounter the H2O production rate was 3 times 10 to the 28th power/sec, + or - 50%, consistent with values derived from the ICE experiments. Comparison of the abundance of CO2(+) ions with the total electron density measured by the plasma electron experiment on ICE indicates a deficiency of ions relative to electrons indicating a population of ions not detected by remote sensing. The absence of detectable Mg(+) rules out this species as a possible ion of M/Q = 24 detected by the Ion Composition Instrument, part of the ICE complement of instruments.

A -100 kV Power Supply for Ion Acceleration in Space-based Mass Spectrometers

NASA Astrophysics Data System (ADS)

Gilbert, J. A.; Zurbuchen, T.; Battel, S.

2017-12-01

High voltage power supplies are used in many space-based time-of-flight (TOF) mass spectrometer designs to accelerate incoming ions and increase the probability of their measurement and proper identification. Ions are accelerated in proportion to their charge state, so singly charged ions such as pickup ions are accelerated less than their multiple-charge state solar wind counterparts. This lack of acceleration results in pickup ion measurements with lower resolution and without determinations of absolute energy. Acceleration reduces the effects of angular scattering and energy straggling when ions pass through thin membranes such as carbon foils, and it brings ion energies above the detection threshold of traditional solid state detectors. We have developed a power supply capable of operating at -100 kV for ion acceleration while also delivering up to 10 W of power for the operation of a floating TOF system. We also show results of benchtop calibration and ion beam tests to demonstrate the functionality and success of this approach.

Detection of negative pickup ions at Saturn's moon Dione

NASA Astrophysics Data System (ADS)

Nordheim, T.; Jones, G. H.; Coates, A. J.; Wellbrock, A.; Hand, K. P.; Waite, J. H., Jr.

2015-12-01

Negative ions may be formed in both tenuous and dense planetary atmospheres and have been observed in-situ at Earth, Titan [Coates et al., 2007, 2009; Wellbrock et al., 2013] and Enceladus [Coates et al., 2010] as well as at comet Halley [Chaizy et al., 1991]. In the case of Titan, heavy hydrocarbon and nitrile based ions with masses reaching almost 14,000 amu/q have been observed using the CAPS Electron Spectrometer (ELS) onboard Cassini. These are believed to form even more massive organic aerosols termed tholins which fall to lower altitudes where they make up the distinct haze layers, and eventually rain down onto Titan's surface perhaps forming the organic-rich dunes. Very tenuous atmospheres were predicted at the smaller icy moons of Saturn [Sittler et al., 2004; Saur and Strobel, 2005], and subsequently detected [Teolis et al., 2010; Tokar et al., 2012]. These are produced when charged particles from Saturn's magnetosphere interact with moon surfaces, ejecting neutral species. Some portion of these atmospheric neutrals will in turn become ionized and 'picked up' by Saturn's corotating magnetosphere. These pickup ions will then move in cycloidal trajectories that we may intercept using the Cassini spacecraft, even at considerable distance from the moon itself. In this fashion, negative and positive pickup ions have been used to infer a tenuous CO2-O2 atmosphere at Saturn's moon Rhea [Teolis et al., 2010], and positive pickup ions at Dione [Tokar et al., 2012]. Here we report on the detection of negative pickup ions during a close flyby of Dione by the Cassini CAPS ELS instrument, and the implications that these observations may have for the Dionian atmosphere. Chaizy, P., et al. (1991), Nature, 349(6308), 393-396 Coates, A. J., et al. (2007), Geophys. Res. Lett., 34(22), 6-11 Coates, A. J., et al. (2009), Planet. Space Sci., 57(14-15), 1866-1871 Coates, A. J., et al. (2010), Icarus, 206(2), 618-622 Saur, J., and D. F. Strobel (2005), Astrophys. J. Lett., 620, L115. Sittler, E. C., et al. (2004), J. Geophys. Res., 109(A1) Teolis, B. D., et al. (2010), Science, 330(6012), 1813-5 Tokar, R. L., et al. (2012) Geophys. Res. Lett., 39(3), 1-7 Wellbrock, A., et al.(2013), Geophys. Res. Lett., 40(17), 4481-4485

Determining the spatial and temporal variability of Enceladus' mass-loading rate from ion-cyclotron wave observations and hybrid simulations

NASA Astrophysics Data System (ADS)

Powell, Ronald; Wei, Hanying; Cowee, Misa; Russell, Christopher; Leisner, Jared; Dougherty, Michele

2014-05-01

The southern plume of Enceladus releases a significant amount of neutrals, ions and dust into the inner magnetosphere of Saturn, thus it plays a critical role in the dynamics of plasma transport. The moon is also considered to be the ultimate source for the dusty E-ring and the extended neutral cloud from 3.5 to 6.5 Saturn radii. The mass loading rate from the plume can not only be directly measured from plasma instruments, but can also be obtained from the magnetic signatures produced by the plume and the properties of ion-cyclotron waves (ICW) generated by pickup ions from the plume. The ICWs grow from the free energy of the highly anisotropic distribution of the pickup ions, and their powers are proportional to the density and energy of the pickup ions. At Enceladus, ICWs are detected by Cassini not only near the moon but throughout the extended neutral cloud in all local times. However, the wave power is largely enhanced near the moon's longitude rather than far away from it. This indicates that on top of the relatively azimuthally symmetric mass-loading source of the neutral cloud, there is a much denser cloud of neutrals centered on the moon and rotating with it. The latter source is the instantaneous mass loading from Enceladus' plume, which leads to asymmetry and dynamics in the magnetosphere. From hybrid simulations, we study the ICW generation and understand the relationship between wave power and pickup ion densities. From observations, we obtain the spatial profiles of the ICW power near and far from the moon. Through comparison with waves at longitudes far away from the moon, we investigate how significant is the plume's mass-loading with respect to the neutral cloud mass-loading. We also compare the waves along several groups of identical trajectories and find that the temporal variability of the plume is within a factor of two.

Mass loading and heating of the Enceladus torus from ion-cyclotron wave observations and hybrid simulations in the Saturn magnetosphere

NASA Astrophysics Data System (ADS)

Russell, C. T.; Dougherty, Michele K.; Cowee, Misa M.; Wei, Hanying; Leisner, Jared; Powell, Ronald

The southern plume of Enceladus releases a significant amount of neutrals, ions and dust into the inner magnetosphere of Saturn, thus it plays a critical role in the dynamics of plasma transport. The moon is also considered to be the ultimate source for the dusty E-ring and the extended neutral cloud from 3.5 to 6.5 Saturn radii. The mass loading rate from the plume can not only be directly measured from plasma instruments, but can also be obtained from the magnetic signatures produced by the plume and the properties of ion-cyclotron waves (ICW) generated by pickup ions from the plume. The ICWs grow from the free energy of the highly anisotropic distribution of the pickup ions, and their powers are proportional to the density and energy of the pickup ions. At Enceladus, ICWs are detected by Cassini not only near the moon but throughout the extended neutral cloud in all local times. However, the wave power is largely enhanced near the moon’s longitude rather than far away from it. This indicates that on top of the relatively azimuthally symmetric mass-loading source of the neutral cloud, there is a much denser cloud of neutrals centered on the moon and rotating with it. The latter source is the instantaneous mass loading from Enceladus’ plume, which leads to asymmetry and dynamics in the magnetosphere. From hybrid simulations, we study the ICW generation and understand the relationship between wave power and pickup ion densities. From observations, we obtain the spatial profiles of the ICW power near and far from the moon. Through comparison with waves at longitudes far away from the moon, we investigate how significant is the plume’s mass-loading with respect to the neutral cloud mass-loading. We also compare the waves along several groups of identical trajectories and find that the temporal variability of the plume is within a factor of two.

Suprathermal electron environment of comet 67P/Churyumov-Gerasimenko: Observations from the Rosetta Ion and Electron Sensor

NASA Astrophysics Data System (ADS)

Clark, G.; Broiles, T. W.; Burch, J. L.; Collinson, G. A.; Cravens, T.; Frahm, R. A.; Goldstein, J.; Goldstein, R.; Mandt, K.; Mokashi, P.; Samara, M.; Pollock, C. J.

2015-11-01

Context. The Rosetta spacecraft is currently escorting comet 67P/Churyumov-Gerasimenko until its perihelion approach at 1.2 AU. This mission has provided unprecedented views into the interaction of the solar wind and the comet as a function of heliocentric distance. Aims: We study the interaction of the solar wind and comet at large heliocentric distances (>2 AU) using data from the Rosetta Plasma Consortium Ion and Electron Sensor (RPC-IES). From this we gain insight into the suprathermal electron distribution, which plays an important role in electron-neutral chemistry and dust grain charging. Methods: Electron velocity distribution functions observed by IES fit to functions used to previously characterize the suprathermal electrons at comets and interplanetary shocks. We used the fitting results and searched for trends as a function of cometocentric and heliocentric distance. Results: We find that interaction of the solar wind with this comet is highly turbulent and stronger than expected based on historical studies, especially for this weakly outgassing comet. The presence of highly dynamical suprathermal electrons is consistent with observations of comets (e.g., Giacobinni-Zinner, Grigg-Skjellerup) near 1 AU with higher outgassing rates. However, comet 67P/Churyumov-Gerasimenko is much farther from the Sun and appears to lack an upstream bow shock. Conclusions: The mass loading process, which likely is the cause of these processes, plays a stronger role at large distances from the Sun than previously expected. We discuss the possible mechanisms that most likely are responsible for this acceleration: heating by waves generated by the pick-up ion instability, and the admixture of cometary photoelectrons.

Comparative study of ion cyclotron waves at Mars, Venus and Earth

NASA Astrophysics Data System (ADS)

Wei, H. Y.; Russell, C. T.; Zhang, T. L.; Blanco-Cano, X.

2011-08-01

Ion cyclotron waves are generated in the solar wind when it picks up freshly ionized planetary exospheric ions. These waves grow from the free energy of the highly anisotropic distribution of fresh pickup ions, and are observed in the spacecraft frame with left-handed polarization and a wave frequency near the ion's gyrofrequency. At Mars and Venus and in the Earth's polar cusp, the solar wind directly interacts with the planetary exospheres. Ion cyclotron waves with many similar properties are observed in these diverse plasma environments. The ion cyclotron waves at Mars indicate its hydrogen exosphere to be extensive and asymmetric in the direction of the interplanetary electric field. The production of fast neutrals plays an important role in forming an extended exosphere in the shape and size observed. At Venus, the region of exospheric proton cyclotron wave production may be restricted to the magnetosheath. The waves observed in the solar wind at Venus appear to be largely produced by the solar-wind-Venus interaction, with some waves at higher frequencies formed near the Sun and carried outward by the solar wind to Venus. These waves have some similarity to the expected properties of exospherically produced proton pickup waves but are characterized by magnetic connection to the bow shock or by a lack of correlation with local solar wind properties respectively. Any confusion of solar derived waves with exospherically derived ion pickup waves is not an issue at Mars because the solar-produced waves are generally at much higher frequencies than the local pickup waves and the solar waves should be mostly absorbed when convected to Mars distance as the proton cyclotron frequency in the plasma frame approaches the frequency of the solar-produced waves. In the Earth's polar cusp, the wave properties of ion cyclotron waves are quite variable. Spatial gradients in the magnetic field may cause this variation as the background field changes between the regions in which the fast neutrals are produced and where they are re-ionized and picked up. While these waves were discovered early in the magnetospheric exploration, their generation was not understood until after we had observed similar waves in the exospheres of Mars and Venus.

Origin of cometary and chondritic refractory organics: Ion irradiation experiments

NASA Astrophysics Data System (ADS)

Quirico, E.; Faure, M.; Faure, A.; Baklouti, D.; Boduch, P.; Rothard, H.; Ballanzat, E.; Dartois, E.; Brunetto, R.; Bonal, L.; Beck, P.; Schmitt, B.; Duprat, J.; Engrand, C.

2017-09-01

The formation process of Refractory Organic matter present in chondrites and Interplanetary Dust Particles (IDPs) of cometary and asteroidal origin is a debated issue. Earlier studies have advocated a formation step in a hot environment, however the potential role of ion irradiation has been so far poorly constrained. We present here experimental simulations that address this issue, comprising thermal degradation and ion irradiation experiments conducted at GANIL (Caen France) and CSNSM (Orsay France). We show that unlike thermal reactions, ion irradiation might lead to ROM-like material under very stringent conditions on both the nuclear dose and the nature of precursor. These very narrow conditions suggest that forming ROM without any action of thermal reactions is extremely difficult in astrophysical environments, either ISM or the proto-solar disk.

DYNAMIC DEUTERIUM ENRICHMENT IN COMETARY WATER VIA ELEY–RIDEAL REACTIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yao, Yunxi; Giapis, Konstantinos P., E-mail: giapis@cheme.caltech.edu

2017-01-20

The deuterium-to-hydrogen ratio (D/H) in water found in the coma of Jupiter family comet (JFC) 67P/Churyumov–Gerasimenko was reported to be (5.3 ± 0.7) × 10{sup −4}, the highest among comets and three times the value for other JFCs with an ocean-like ratio. This discrepancy suggests the diverse origins of JFCs and clouds the issue of the origin of Earth’s oceanic water. Here we demonstrate that Eley–Rideal reactions between accelerated water ions and deuterated cometary surface analogs can lead to instantaneous deuterium enrichment in water scattered from the surface. The reaction proceeds with H{sub 2}O{sup +} abstracting adsorbed D atoms, formingmore » an excited H{sub 2}DO* state, which dissociates subsequently to produce energetic HDO. Hydronium ions are also produced readily by the abstraction of H atoms, consistent with H{sub 3}O{sup +} detection and abundance in various comets. Experiments with water isotopologs and kinematic analysis on deuterated platinum surfaces confirmed the dynamic abstraction mechanism. The instantaneous fractionation process is independent of the surface temperature and may operate on the surface of cometary nuclei or dust grains, composed of deuterium-rich silicates and carbonaceous chondrites. The requisite energetic water ions have been detected in the coma of 67P in two populations. This dynamic fractionation process may temporarily increase the water D/H ratio, especially as the comet gets closer to the Sun. The magnitude of the effect depends on the water ion energy-flux and the deuterium content of the exposed cometary surfaces.« less

Anions in Cometary Comae

NASA Technical Reports Server (NTRS)

Charnley, Steven B.

2011-01-01

The presence of negative ions (anions) in cometary comae is known from Giotto mass spectrometry of IP/Halley. The anions 0-, OH-, C-, CH- and CN- have been detected, as well as unidentified anions with masses 22-65 and 85-110 amu (Chaizy et al. 1991). Organic molecular anions are known to have a significant impact on the charge balance of interstellar clouds and circumstellar envelopes and have been shown to act as catalysts for the gas-phase synthesis of larger hydrocarbon molecules in the ISM, but their importance in cometary comae has not yet been explored. We present details of the first attempt to model the chemistry of anions in cometary comae. Based on the combined chemical and hydro dynamical model of Rodgers & Charnley (2002), we investigate the role of large carbon-chain anions in cometary coma chemistry. We calculate the effects of these anions on coma thermodynamics, charge balance and examine their impact on molecule formation.

A New Model for the Heliosphere’s “IBEX Ribbon”

NASA Astrophysics Data System (ADS)

Giacalone, J.; Jokipii, J. R.

2015-10-01

We present a model for the narrow, ribbon-like enhancement in the emission of ∼keV energetic neutral atoms (ENA) coming from the outer heliosphere, coinciding roughly with the plane of the very local interstellar magnetic field (LISMF). We show that the pre-existing turbulent LISMF has sufficient amplitude in magnitude fluctuations to efficiently trap ions with initial pitch-angles near 90°, primarily by magnetic mirroring, leading to a narrow region of enhanced pickup-proton intensity. The pickup protons interact with cold interstellar hydrogen to produce ENAs seen at 1 AU. The computed width of the resulting ribbon of emission is consistent with observations. We also present results from a numerical model that are also generally consistent with the observations. Our interpretation relies only on the pre-existing turbulent interstellar magnetic field to trap the pickup protons. This leads to a broader local pitch-angle distribution compared to that of a ring. Our numerical model also predicts that the ribbon is double-peaked with a central depression. This is a further consequence of the (primarily) magnetic mirroring of pickup ions with pitch-angles close to 90° in the pre-existing, turbulent interstellar magnetic field.

A NEW MODEL FOR THE HELIOSPHERE’S “IBEX RIBBON”

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giacalone, J.; Jokipii, J. R.

We present a model for the narrow, ribbon-like enhancement in the emission of ∼keV energetic neutral atoms (ENA) coming from the outer heliosphere, coinciding roughly with the plane of the very local interstellar magnetic field (LISMF). We show that the pre-existing turbulent LISMF has sufficient amplitude in magnitude fluctuations to efficiently trap ions with initial pitch-angles near 90°, primarily by magnetic mirroring, leading to a narrow region of enhanced pickup-proton intensity. The pickup protons interact with cold interstellar hydrogen to produce ENAs seen at 1 AU. The computed width of the resulting ribbon of emission is consistent with observations. Wemore » also present results from a numerical model that are also generally consistent with the observations. Our interpretation relies only on the pre-existing turbulent interstellar magnetic field to trap the pickup protons. This leads to a broader local pitch-angle distribution compared to that of a ring. Our numerical model also predicts that the ribbon is double-peaked with a central depression. This is a further consequence of the (primarily) magnetic mirroring of pickup ions with pitch-angles close to 90° in the pre-existing, turbulent interstellar magnetic field.« less

PROTON HEATING BY PICK-UP ION DRIVEN CYCLOTRON WAVES IN THE OUTER HELIOSPHERE: HYBRID EXPANDING BOX SIMULATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hellinger, Petr; Trávníček, Pavel M., E-mail: petr.hellinger@asu.cas.cz

Using a one-dimensional hybrid expanding box model, we investigate properties of the solar wind in the outer heliosphere. We assume a proton–electron plasma with a strictly transverse ambient magnetic field and, aside from the expansion, we take into account the influence of a continuous injection of cold pick-up protons through the charge-exchange process between the solar wind protons and hydrogen of interstellar origin. The injected cold pick-up protons form a ring distribution function, which rapidly becomes unstable, and generate Alfvén cyclotron waves. The Alfvén cyclotron waves scatter pick-up protons to a spherical shell distribution function that thickens over that timemore » owing to the expansion-driven cooling. The Alfvén cyclotron waves heat solar wind protons in the perpendicular direction (with respect to the ambient magnetic field) through cyclotron resonance. At later times, the Alfvén cyclotron waves become parametrically unstable and the generated ion-acoustic waves heat protons in the parallel direction through Landau resonance. The resulting heating of the solar wind protons is efficient on the expansion timescale.« less

Stability of the magnetosonic wave in a cometary multi-ion plasma

NASA Astrophysics Data System (ADS)

Sreekala, G.; Varghese, Anu; Jayakumar, Neethu; Michael, Manesh; Sebastian, Sijo; Venugopal, Chandu

2017-05-01

A generalized dispersion relation of the magnetosonic wave in a four component plasma consisting of electrons and hydrogen ions of solar origin and positively and negatively charged oxygen ions of cometary origin has been derived by using the Vlasov-Maxwell kinetic model. Parallel to the magnetic field, the hydrogen and electron components are modeled by a drifting Maxwellian distribution; perpendicular to the magnetic field, we use a loss cone type distribution obtained by the subtraction of two Maxwellian distributions having different temperatures. The effect of change in the drift velocity of streaming components and number densities and temperatures of each species in driving the instability has been analyzed both analytically and numerically. For typical parameters at comet Halley, we find that both positively and negatively charged oxygen ions can drive the wave unstable.

Effects of the non-extensive parameter on the propagation of ion acoustic waves in five-component cometary plasma system

NASA Astrophysics Data System (ADS)

Mahmoud, Abeer A.

2018-01-01

Some important evolution nonlinear partial differential equations are derived using the reductive perturbation method for unmagnetized collisionless system of five component plasma. This plasma system is a multi-ion contains negatively and positively charged Oxygen ions (heavy ions), positive Hydrogen ions (lighter ions), hot electrons from solar origin and colder electrons from cometary origin. The positive Hydrogen ion and the two types of electrons obey q-non-extensive distributions. The derived equations have three types of ion acoustic waves, which are soliton waves, shock waves and kink waves. The effects of the non-extensive parameters for the hot electrons, the colder electrons and the Hydrogen ions on the propagation of the envelope waves are studied. The compressive and rarefactive shapes of the three envelope waves appear in this system for the first order of the power of the nonlinearity strength with different values of non-extensive parameters. For the second order, the strength of nonlinearity will increase and the compressive type of the envelope wave only appears.

Modeling of pickup ion distributions in the Halley cometosheath: Empirical limits on rates of ionization, diffusion, loss and creation of fast neutral atoms

NASA Technical Reports Server (NTRS)

Huddleston, D. E.; Neugebauer, M.; Goldstein, B. E.

1994-01-01

The shape of the velocity distribution of water group ions observed by the Giotto ion mass spectrometer on its approach to comet Halley is modeled to derive empirical values for the rates of ionization, energy diffusion, and loss in the midcometosheath. The model includes the effect of rapid pitch angle scattering into a bispherical shell distribution as well as the effect of the magnetization of the plasma on the charge exchange loss rate. It is found that the average rate of ionization of cometary neutrals in this region of the cometosheath appears to be of the order of a factor 3 faster than the `standard' rates approx. 1 x 10(exp -6)/s that are generally assumed to model the observations in most regions of the comet environment. For the region of the coma studied in the present work (approx. 1 - 2 x 10(exp 5) km from the nucleus), the inferred energy diffusion coefficient is D(sub 0) approx. equals 0.0002 to 0.0005 sq km/cu s, which is generally lower than values used in other models. The empirically obtained loss rate appears to be about an order of magnitude greater than can be explained by charge exchange with the `standard' cross section of approx. 2 x 10(exp -15)sq cm. However such cross sections are not well known and for water group ion/water group neutral interactions, rates as high as 8 x 10(exp -15) sq cm have previously been suggested in the literature. Assuming the entire loss rate is due to charge exchange yields a rate of creation of fast neutral atoms of the order of approx. 10(exp -4)/s or higher, depending on the level of velocity diffusion. The fast neutrals may, in turn, be partly responsible for the higher-than-expected ionization rate.

The interaction of heavy ions from Comet P/Giacobini-Zinner with the solar wind

NASA Astrophysics Data System (ADS)

Sanderson, T. R.; Wenzel, K.-P.; Daly, P.; Cowley, S. W. H.; Hynds, R. J.; Smith, E. J.; Bame, S. J.; Zwickl, R. D.

1986-04-01

The encounter between the ICE spacecraft and Comet P/Giacobini-Zinner was characterized in the solar wind by intense fluxes of heavy ions, measurable over a region 6 x 10 to the 6th km in extent. The ions are observed with highly anisotropic angular distributions, steep energy spectra, and a change in the energy spectrum at around 80 keV, consistent with a composition predominantly of the water group. Flux versus time profiles follow a general fall off with increasing distance from the comet, but with a marked inbound/outbound asymmetry. This asymmetry is due to the higher solar wind velocity on the outbound pass, giving rise to an increased energy gain of the pick-up ions. The flux versus time profiles are strongly modulated by the rapid changes in the direction of interplanetary magnetic field. Correlated observations of energetic ions, the interplanetary magnetic field and the solar wind are presented, and these observations are compared with theoretical predictions of the ion pick-up process.

Ion cyclotron waves at Saturn: Implications of latitudinal distribution for the neutral water torus

NASA Astrophysics Data System (ADS)

Crary, F. J.; Dols, V. J.

2016-12-01

Ion cyclotron waves in Saturn's magnetosphere, produced by freshly produced pickup ions, are an indication of plasma production and constrain the distribution of the parent neutrals. Cassini spacecraft observations have shown that these waves are generally present between 4 and 6 Saturn radii, are generated near the equator and propagate to higher latitudes. Wave amplitudes peak at approximately 2 degrees off the equator, where the amplitude is roughly twice its equatorial value. At higher latitudes, the wave amplitudes decrease, dropping by over an order of magnitude by 5 degrees latitude. This has been interpreted as advective growth, from due to equatorially confined pickup ions. Away from this source population, the waves are damped by the thermal background ions. Here, we present an analysis of this growth and damping. Using both analytic theory and hybrid simulations, calculate ion cyclotron wave amplitudes as a function of latitude. These results allow us to estimate the vertical extent of the neutral cloud.

The Phobos neutral and ionized torus

NASA Astrophysics Data System (ADS)

Poppe, A. R.; Curry, S. M.; Fatemi, S.

2016-05-01

Charged particle sputtering, micrometeoroid impact vaporization, and photon-stimulated desorption are fundamental processes operating at airless surfaces throughout the solar system. At larger bodies, such as Earth's Moon and several of the outer planet moons, these processes generate tenuous surface-bound exospheres that have been observed by a variety of methods. Phobos and Deimos, in contrast, are too gravitationally weak to keep ejected neutrals bound and, thus, are suspected to generate neutral tori in orbit around Mars. While these tori have not yet been detected, the distribution and density of both the neutral and ionized components are of fundamental interest. We combine a neutral Monte Carlo model and a hybrid plasma model to investigate both the neutral and ionized components of the Phobos torus. We show that the spatial distribution of the neutral torus is highly dependent on each individual species (due to ionization rates that span nearly 4 orders of magnitude) and on the location of Phobos with respect to Mars. Additionally, we present the flux distribution of torus pickup ions throughout the Martian system and estimate typical pickup ion fluxes. We find that the predicted pickup ion fluxes are too low to perturb the ambient plasma, consistent with previous null detections by spacecraft around Mars.

The mini-CIDEX GC/IMS: Analysis of cometary ice and dust

NASA Technical Reports Server (NTRS)

Kojiro, Daniel R.; Carle, Glenn C.; Humphry, Donald E.; Shao, Maxine; Takeuchi, Nori

1995-01-01

Comets are recognized as among the most scientifically important objects in the solar system. They are presumed relics of the early primitive material in the solar nebula and are believed to have provided a general enrichment of volatiles to the inner solar system. The Cometary Coma Chemical Composition (C4) Mission, a proposed Discovery-Class Mission, will analyze materials released into the coma, providing information leading to the understanding of the chemical composition and make-up of the cometary nucleus. As one of two scientific instruments in the C4 spacecraft, an advanced and streamlined version of the Cometary Ice and Dust Experiment (CIDEX), a mini-CIDEX, will employ an X-Ray Fluorescence (XRF) spectrometer to determine bulk elemental composition of cometary dust grains and a Gas Chromatograph/Ion Mobility Spectrometer (GC/IMS) for determination of the molecular composition of dust and ices following stepwise pyrolysis and combustion. A description of the mini-CIDEX IMS will be provided as well as data from analyses conducted using the mini-CIDEX breadboard instrument.

Cometary particulate analyzer. [mass spectrometry of laser plasmas

NASA Technical Reports Server (NTRS)

Friichtenicht, J. F.; Miller, D. J.; Utterback, N. G.

1979-01-01

A concept for determining the relative abundance of elements contained in cometary particulates was evaluated. The technique utilizes a short, high intensity burst of laser radiation to vaporize and ionize collected particulate material. Ions extracted from this laser produced plasma are analyzed in a time of flight mass spectrometer to yield an atomic mass spectrum representative of the relative abundance of elements in the particulates. Critical aspects of the development of this system are determining the ionization efficiencies for various atomic species and achieving adequate mass resolution. A technique called energy-time focus, which utilizes static electric fields to alter the length of the ion flight path in proportion to the ion initial energy, was used which results in a corresponding compression to the range of ion flight times which effectively improves the inherent resolution. Sufficient data were acquired to develop preliminary specifications for a flight experiment.

On charge exchange effect in the vicinity of the cometopause of Comet Halley

NASA Astrophysics Data System (ADS)

Ip, W.-H.

1989-08-01

In order to explore the physical nature of the cometopause observed at Comet Halley by the Vega spacecraft and by the Giotto probe, the chemical compositional changes and variations of the thermal-energy distributions of the water-group ions are examined, adopting a two-dimensional cometary-plasma flowfield model based on three-dimensional MHD simulations of Fedder et al. (1986). The charge-exchange loss of hot cometary ions and the solar-wind protons could be used to explain the observed number-density profiles quantitatively. The resulting exponential depletion of the hot-ion populations with a scale length of about 10,000 km occurs near 60,000-80,000 km along the trajectory of Giotto, as indicated by both theoretical computations and the ion-mass-spectrometer measurements. The formation of the cometopause located at about 140,000 km is therefore not necessarily as closely related to the charge-exchange process.

Preliminary Interpretation of Titan Plasma Interaction as Observed by the Cassini Plasma Spectrometer: Comparisons With Voyager 1

NASA Technical Reports Server (NTRS)

Hartle, R. E.; Sittler, E. C.; Johnson, R. E.; Simpson, D. G.; Smith, H. T.; Crary, F.; McComas, D. J.; Young, D. T.; Coates, A. J.; Neubauer, F. M.

2005-01-01

The Cassini Plasma Spectrometer (CAPS) instrument made measurements of Titan s plasma environment when the Cassini Orbiter flew through the moon s plasma wake October 26,2004 (flyby TA) and December 13,2004 (flyby TB). Preliminary CAPS ion and electron measurements from these encounters (1,2) are compared with measurements made by the Voyager I Plasma Science Instrument (PLS). The comparisons are used to evaluate previous interpretations and predictions of the Titan plasma environment that have been made using PLS measurements (3,4). The plasma wake trajectories of flybys TA, TB and Voyager 1 are similar because they occurred when Titan was near Saturn s local noon. These similarities make possible direct, meaningful comparisons between the various plasma wake measurements. The inquiries stimulated by the previous interpretations and predictions made using PLS data have produced the following results from the CAPS ion measurements: A) The major ambient ion components of Saturn s rotating magnetosphere in the vicinity of Titan are H+, H2+, and O+. B) Finite gyroradius effects are apparent in ambient 0 as the result of its interaction with Titan s atmosphere. C) The principal pickup ions are composed of H+, H2+, CH4+ and N2+. D) There is clear evidence of slowing down of the ambient plasma due to pickup ion mass loading; and, as the ionopause is approached, heavier pickup ions such as N2+ become dominant. The similarities and differences between the magnitudes and structures of the electron densities and temperatures along the three flyby trajectories are described

The structure of a cometary type I tail - Ground-based and ICE observations of P/Giacobini-Zinner

NASA Technical Reports Server (NTRS)

Slavin, J. A.; Goldberg, B. A.; Smith, E. J.; Mccomas, D. J.; Bame, S. J.

1986-01-01

Comparison of ground-based and in situ observations of P/Giacobini-Zinner are used to investigate the morphology of a type I cometary tail. ICE magnetic field and plasma measurements show a well-defined cometary magnetotail composed of two magnetic lobes in pressure equilibrium with a central plasma sheet. A dependence of ion tail width on IMF direction is found which strongly suggests that the classical type I ion tails observed on the ground consist predominantly of emissions from the slab-shaped plasma sheet separating the magnetic lobes. The width of the G-Z magnetotail is determined to be 9.8 (+ or - 0.5) x 10 to the 3rd km with a quasi-circular cross section. The results of this study also indicate that some of the dynamical thinnings and thickenings observed in long type I tails may be caused by IMF variations changing the angle with which the plasma sheet is viewed at earth.

The development and testing of the fast imaging plasma spectrometer and its application in the plasma environment at Mercury

NASA Astrophysics Data System (ADS)

Koehn, Patrick Leo

The plasma environment at Mercury is a rich laboratory for studying the interaction of the solar wind with a planet. Three primary populations of ions exist at Mercury: solar wind, magnetospheric particles, and pickup ions. Pickup ions are generated through the ionization of Mercury's exosphere or are sputtered particles from the Mercury surface. A comprehensive mission to Mercury should include a sensor that is able to determine the dynamical properties and composition of all three plasma components. The Fast Imaging Plasma Spectrometer (FIPS) is an instrument to measure the composition of these ion populations and their three-dimensional velocity distribution functions. It is lightweight, fast, and has a very large field of view, and these properties made possible its accommodation within the highly mass- constrained payload of MESSENGER (MErcury: Surface, Space ENvironment, GEochemistry, Ranging) mission, a Mercury orbiter. This work details the development cycle of FIPS, from concept to prototype testing. It begins with science studies of the magnetospheric and pickup ion environments of Mercury, using state-of-the-art computer simulations to produce static and quasi-dynamic magnetospheric systems. Predictions are made of the spatially variable plasma environment at Mercury, and the temporally varying magnetosphere-solar wind interaction is examined. Pickup ion studies provide insights to particle loss mechanisms and the nature of the radar-bright regions at the Hermean poles. These studies produce science requirements for successfully measuring this environment with an orbiting mass spectrometer. With these science requirements in mind, a concept for a new electrostatic analyzer is created. This concept is considered from a theoretical standpoint, and compared with other, similarly performing instruments, both of the past and currently in use. The development cycle continues with instrument simulation, which allows the design to be adjusted to fit within the science requirements of the mission. Finally, a prototype electrostatic is constructed and tested in a space- simulating vacuum chamber system. The results of these tests are compared with the simulation results, and ultimately shown to fit within the science requirements for the MESSENGER mission.

CoMA: A high resolution Time-Of-Flight Secondary Ion Mass Spectrometer (TOF-SIMS) for in situ analysis of cometary matter

NASA Technical Reports Server (NTRS)

Zscheeg, Harry; Kissel, J.; Natour, G.

1992-01-01

A lot of clues concerning the origin of the solar system can be found by sending an exploring spacecraft to a rendezvous with a comet. The space experiment CoMA, which will measure the elemental, isotopic, and molecular composition of cometary dust grains is described. It will be flown on NASA's Comet Rendezvous Asteroid Flyby (CRAF) mission.

What can meteorites tell us about comets?

NASA Technical Reports Server (NTRS)

Anders, Edward

1986-01-01

Cometary silicates, carbon, and volatiles are reviewed using data from the Halley probes, interplanetary dust particles, and cometary spectra. The origins of anhydrous Fe(2+)-bearing silicates; whether hydrated silicates, if present, were made by gaseous or liquid H2O3; sources of organic compounds: ion-molecule reactions, photochemistry, grain catalysis; sources of CO2 and of organic polymers; and interstellar molecules and grains in comets are discussed.

Magnetofluid Simulations of the Global Solar Wind Including Pickup Ions and Turbulence Modeling

NASA Technical Reports Server (NTRS)

Goldstein, Melvyn L.; Usmanov, Arcadi V.; Matthaeus, William H.

2011-01-01

I will describe a three-dimensional magnetohydrodynamic model of the solar wind that takes into account turbulent heating of the wind by velocity and magnetic fluctuations as well as a variety of effects produced by interstellar pickup protons. In this report, the interstellar pickup protons are treated as one fluid and the protons and electrons are treated together as a second fluid. The model equations include a Reynolds decomposition of the plasma velocity and magnetic field into mean and fluctuating quantities, as well as energy transfer from interstellar pickup protons to solar wind protons that results in the deceleration of the solar wind. The model is used to simulate the global steady-state structure of the solar wind in the region from 0.3 to 100 AU. Where possible, the model is compared with Voyager data. Initial results from generalization to a three-fluid model is described elsewhere in this session.

Interstellar Pickup Ion Acceleration in the Turbulent Magnetic Field at the Solar Wind Termination Shock Using a Focused Transport Approach

NASA Astrophysics Data System (ADS)

Ye, Junye; le Roux, Jakobus A.; Arthur, Aaron D.

2016-08-01

We study the physics of locally born interstellar pickup proton acceleration at the nearly perpendicular solar wind termination shock (SWTS) in the presence of a random magnetic field spiral angle using a focused transport model. Guided by Voyager 2 observations, the spiral angle is modeled with a q-Gaussian distribution. The spiral angle fluctuations, which are used to generate the perpendicular diffusion of pickup protons across the SWTS, play a key role in enabling efficient injection and rapid diffusive shock acceleration (DSA) when these particles follow field lines. Our simulations suggest that variation of both the shape (q-value) and the standard deviation (σ-value) of the q-Gaussian distribution significantly affect the injection speed, pitch-angle anisotropy, radial distribution, and the efficiency of the DSA of pickup protons at the SWTS. For example, increasing q and especially reducing σ enhances the DSA rate.

Mechanisms of Ionospheric Mass Escape

NASA Technical Reports Server (NTRS)

Moore, T. E.; Khazanov, G. V.

2010-01-01

The dependence of ionospheric O+ escape flux on electromagnetic energy flux and electron precipitation into the ionosphere is derived for a hypothetical ambipolar pick-up process, powered the relative motion of plasmas and neutral upper atmosphere, and by electron precipitation, at heights where the ions are magnetized but influenced by photo-ionization, collisions with gas atoms, ambipolar and centrifugal acceleration. Ion pick-up by the convection electric field produces "ring-beam" or toroidal velocity distributions, as inferred from direct plasma measurements, from observations of the associated waves, and from the spectra of incoherent radar echoes. Ring-beams are unstable to plasma wave growth, resulting in rapid relaxation via transverse velocity diffusion, into transversely accelerated ion populations. Ion escape is substantially facilitated by the ambipolar potential, but is only weakly affected by centrifugal acceleration. If, as cited simulations suggest, ion ring beams relax into non-thermal velocity distributions with characteristic speed equal to the local ion-neutral flow speed, a generalized "Jeans escape" calculation shows that the escape flux of ionospheric O+ increases with Poynting flux and with precipitating electron density in rough agreement with observations.

THE ROLE OF PICKUP IONS ON THE STRUCTURE OF THE VENUSIAN BOW SHOCK AND ITS IMPLICATIONS FOR THE TERMINATION SHOCK

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu Quanming; Shan Lican; Zhang Tielong

2013-08-20

The recent crossing of the termination shock by Voyager 2 has demonstrated the important role of pickup ions (PUIs) in the physics of collisionless shocks. The Venus Express (VEX) spacecraft orbits Venus in a 24 hr elliptical orbit that crosses the bow shock twice a day. VEX provides a unique opportunity to investigate the role of PUIs on the structure of collisionless shocks more generally. Using VEX observations, we find that the strength of the Venusian bow shock is weaker when solar activity is strong. We demonstrate that this surprising anti-correlation is due to PUIs mediating the Venusian bow shock.

The effect of electron collisions on rotational excitation of cometary water

NASA Technical Reports Server (NTRS)

Xie, Xingfa; Mumma, Michael J.

1991-01-01

The e-H2O collisional rate for exciting rotational transitions in cometary water is evaluated for conditions found in Comet Halley. The e-H2O collisional rate exceeds that for excitation by neutral-neutral collisions at distances exceeding 3000 km from the cometary nucleus, in the case of the O sub 00 yields 1 sub 11 transition. The estimates are based on theoretical and experimental studies of e-H2O collisions, on ion and electron parameters acquired in-situ by instruments on the Giotto and Vega spacecraft, and on results obtained from models of the cometary ionosphere. The contribution of electron collisions may explain the need for large water-water cross-sections in models which neglect the effect of electrons. The importance of electron collisions is enhanced for populations of water molecules in regions where their rotational lines are optically thick.

The effect of electron collisions on rotational populations of cometary water

NASA Technical Reports Server (NTRS)

Xie, Xingfa; Mumma, Michael J.

1992-01-01

The e-H2O collisional rate for exciting rotational transitions in cometary water is evaluated for conditions found in Comet Halley during the Giotto spacecraft encounter. In the case of the 0(00)-1(11) rotational transition, the e-H2O collisional rate exceeds that for excitation by neutral-neutral collisions at distances exceeding 3000 km from the cometary nucleus. The estimates are based on theoretical and experimental studies of e-H2O collisions, on ion and electron parameters acquired in situ by instruments on the Giotto and Vega spacecraft, and on results obtained from models of the cometary ionosphere. Thus, the rotational temperature of the water molecule in the intermediate coma may be controlled by collisions with electrons rather than with neutral molecules, and the rotational temperature retrieved from high-resolution IR spectra of water in Comet Halley may reflect electron temperatures rather than neutral gas temperatures in the intermediate coma.

The oxygen isotopic composition (18O/16O) in the dust of comet 67P/Churyumov-Gerasimenko measured by COSIMA on-board Rosetta

NASA Astrophysics Data System (ADS)

Paquette, J. A.; Engrand, C.; Hilchenbach, M.; Fray, N.; Stenzel, O. J.; Silen, J.; Rynö, J.; Kissel, J.

2018-07-01

The oxygen isotopic ratio 18O/16O has been measured in cometary gas for a wide variety of comets, but the only measurements in cometary dust were performed by the Stardust cometary sample return mission. Most such measurements find a value of the ratio that is consistent with Vienna Standard Mean Ocean Water (VSMOW) within errors. In this work we present the result of a measurement, using the COSIMA (the COmetary Secondary Ion Mass Analyser) instrument on the Rosetta orbiter, of the oxygen isotopic ratio in dust from Comet 67P/Churyumov-Gerasimenko. Measuring the 18O/16O ratio with COSIMA is challenging for a number of reasons, but it is possible with a reasonable degree of precision. We find a result of 2.00 × 10-3 ± 1.2 × 10-4, which is consistent within errors with VSMOW.

Electromagnetic ion instabilities in a cometary environment

NASA Astrophysics Data System (ADS)

Gary, S. P.; Madland, C. D.

1988-01-01

This paper considers the linear theory of electromagnetic ion beam and ion ring-beam instabilities in a homogeneous Vlasov plasma. Propagation parallel or antiparallel to a uniform magnetic field and frequencies at or below the proton cyclotron frequency are considered. For parameters representative of the distant cometary environment, the authors show that instabilities with right-hand polarization in the zero momentum frame have larger linear growth rates than left-hand polarized instabilities at α values up to 90° where α is the angle between the solar wind velocity and the uniform interplanetary magnetic field. If both a proton beam and an oxygen beam are present with α = 0°, two right-hand resonant instabilities may grow; these two modes are distinct and relatively independent of one another for a very wide range of proton/oxygen beam density ratios.

Global hybrid simulation of the solar wind interaction with the dayside of Venus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moore, K.R.; Thomas, V.A.; McComas, D.J.

1991-05-01

The authors present a 3-dimensional global hybrid simulation of the interaction of the solar wind with the entire dayside of Venus. The model obstacle is half the size of Venus, and planetary ion mass loading is included self-consistently. Results are compared to observations as well as to results from gasdynamic convected field modeling. Magnetic field magnitudes and bulk flow speeds along the planet-Sun line are comparable in both models, but only the hybrid model reproduces the experimentally observed magnetic barrier proton density depletions. The finite gyroradius of the planetary pickup ions causes a number density asymmetry in the direction ofmore » the convective ({minus}V {times} B) electric field, as predicted and observed. Mass addition consistent with photoionization of the planetary neutral hot oxygen corona has little effect on the geometry of the shock, including the subsolar and terminator shock altitudes. Mass addition rates well in excess of likely values are required to significantly affect the model shock geometry. The hybrid model results imply that oxygen ions originating deep within the dayside Venus magnetic barrier are nearly fluidlike while oxygen ions produced higher on the dayside, at much lower densities, behave more as test particles. Gasdynamic modeling incorporating both fluid and test particle mass addition reproduces the O{sup +} terminator escape flux (a few times 10{sup 24} s{sup {minus}1}) found in the hybrid model and inferred from observations, but underestimates the escape region spatial extent. The hybrid model predictions include a shock asymmetry dependent on the upstream IMF orientation, asymmetries in the magnetic barrier position and field magnitude, an asymmetry in pickup ion speed altitude profiles, and a finite gyroradius effect asymmetry in pickup ion number density caused by field draping.« less

Oxygen Loss from Venus and the Influence of Extreme Solar Wind Conditions

NASA Astrophysics Data System (ADS)

McEnulty, Tess Rose

2012-06-01

The purpose of this dissertation is to expand our understanding of oxygen ion escape to space from Venus and its dependence on extreme solar wind conditions found during interplanetary coronal mass ejections (ICMEs). The solar wind dynamic pressure outside of the Venus bow shock did not exceed ˜12 nPa, during 2006-2009, while the solar wind dynamic pressure was higher than this for ˜10% of the time during the PVO mission. Oxygen ions escape Venus through multiple regions near the planet. One of these regions is the magnetosheath, where high energy pick-up ions are accelerated by the solar wind convection electric field. High energy (>1 keV) O+ pick-up ions within the Venus magnetosheath reached higher energy at lower altitude when the solar wind was disturbed by ICMEs compared to pick-up ions when the external solar wind was not disturbed, between 2006-2007. However, the count rate of O+ was not obviously affected by the ICMEs during this time period. In addition to high energy pick-up ions, VEX also detects low energy (˜10-100 eV) O+ within the ionosphere and wake of Venus. These low energy oxygen ions are difficult to interpret, because the spacecraft's relative velocity and potential can significantly affect the measured energy. If VEX ion data is not corrected for the spacecraft's relative velocity and potential, gravitationally bound O+ could be misinterpreted as escaping. These gravitationally bound oxygen ions can extend on the nightside to ˜-2 Venus radii and may even return to the planet after reaching high altitudes in the wake. Gravitationally bound ions will lower the total O+ escape estimated from Venus if total escape is calculated including these ions. However, if the return flux is low compared to the total escaping outflow, this effect is not significant. An ICME with a dynamic pressure of 17.6 nPa impacted Venus on November 11, 2011. During this ICME, the high energy pick-up O+ and the low energy O+ ions were affected. Oxygen ions in the magnetosheath, ionosphere, and tail had higher energies during the ICME, compared to O + energies when the external solar wind conditions were undisturbed. High energy ions were escaping within the dayside magnetosheath region when the ICME was passing as well as when the solar wind was undisturbed. However, during the ICME passage, these O+ ions had three orders of magnitude higher counts. The low energy O+ during the undisturbed days was gravitationally bound, while during the ICME a portion of the low energy ions were likely escaping. The most significant difference in O + during the ICME was high energy pickup ions measured in the wake on the outbound portion of the orbit. These ions had an escape flux of 2.5 X 108 O+cm-2sec-1, which is higher than the average escape flux in all regions of the wake. In addition, the interplanetary magnetic field (IMF) was in a configuration that may have rotated an even higher escape flux O+ away from the VEX orbit. This needs to be confirmed with sampling of other regions in the wake during large ICMEs. A lower bound on the total O+ escape during this event could be ˜2.8 X1026 to 6.5 X 1027 O +/sec, which is 2-3 orders of magnitude higher than the average escape flux measured by VEX. Hence, ICMEs could have played a major role in the total escape of O+ from Venus. The results presented in this dissertation can be used as a guide for future studies of O+ escape at Venus. As we move into solar maximum, Venus will likely be impacted by more large ICMEs. The ICME from the last study of this dissertation was the largest yet measured by VEX, but its 17.6 nPa dynamic pressure is lower than the largest ICMEs during the PVO time period (˜ 80 nPa). The work in this dissertation is also relevant to Mars, since Mars interacts with the solar wind in a similar manner and has analogous ion escape mechanisms. The upcoming MAVEN (Mars Atmosphere and Volatile Evolution) mission will launch at the end of 2013 to study the Martian atmosphere, escape processes, and history of volatiles. This mission will have an in-situ ion instrument and magnetometer similar to those used for the studies in this dissertation, so one could conduct similar studies of the oxygen ion escape from Mars during extreme solar wind conditions. (Abstract shortened by UMI.)

Modeling of Pickup Ion Distributions in the Halley Cometo-Sheath: Empirical Rates of Ionization, Diffusion, Loss and Creation of Fast Neutral Atoms

NASA Technical Reports Server (NTRS)

Huddleston, D.; Neugebauer, M.; Goldstein, B.

1994-01-01

The shape of the velocity distribution of water-group ions observed by the Giotto ion mass spectrometer on its approach to comet Halley is modeled to derive empirical values for the rates on ionization, energy diffusion, and loss in the mid-cometosheath.

Plasma IMS Composition Measurements for Europa and the Other Galilean Moons

NASA Technical Reports Server (NTRS)

Sittler, Edward; Cooper, John; Hartle, Richard; Lipatov, Alexander; Mahaffy, Paul; Paterson, William; Pachalidis, Nick; Coplan, Mike; Cassidy, Tim

2010-01-01

NASA and ESA are planning the joint Europa Jupiter System Mission (EJSM) to the Jupiter system with specific emphasis to Europa and Ganymede, respectively. The Japanese Space Agency is also planning an orbiter mission to explore Jupiter's magnetosphere and the Galilean satellites. For NASA's Jupiter Europa Orbiter (JEO) we are developing the 3D Ion Mass Spectrometer (IMS) with two main goals which can also be applied to the other Galilean moons, 1) measure the plasma interaction between Europa and Jupiter's magnetosphere and 2) infer the 4 pi surface composition to trace elemental and significant isotopic levels. The first goal supports the magnetometer (MAG) measurements, primarily directed at detection of Europa's sub-surface ocean, while the second gives information about transfer of material between the Galilean moons, and between the moon surfaces and subsurface layers putatively including oceans. The measurement of the interactions for all the Galilean moons can be used to trace the in situ ion measurements of pickup ions back to either Europa's or Ganymede's surface from the respectively orbiting spacecraft. The IMS instrument, being developed under NASA's Astrobiology Instrument Development Program, would maximally achieve plasma measurement requirements for JEO and EJSM while moving forward our knowledge of Jupiter system composition and source processes to far higher levels than previously envisaged. The composition of the global surfaces of Europa and Ganymede can be inferred from the measurement of ejected neutrals and pick-up ions using at minimum an in situ payload including MAG and IMS also fully capable of meeting Level 1 mission requirements for ocean detection and survey. Elemental and isotopic analysis of potentially extruded oceanic materials at the moon surfaces would further support the ocean objectives. These measurements should be made from a polar orbiting spacecraft about Europa or Ganymede at height 100 km. The ejecta produced by sputtering of the surfaces of Europa and Ganymede has been shown to be representative of the surface composition. Level 2 science on surface geology and composition can then be further enhanced by addition of the following: 3D Ion Neutral Mass Spectrometer (INNS), 3D plasma electron spectrometer (ELS), and hot plasma energetic particle instrument. The measurement approach is to alternate between times measuring pickup ions and times measuring plasma and magnetic field parameters along the spacecraft trajectory. By measuring the pickup ion energy, arrival direction and mass-per-charge, the ion can be traced back along the ejection trajectory to the approximate area of origin if the 3-D electric field and magnetic field are known. In situ observations of plasma flow velocities and vector magnetic fields can be used to determine the local convective electric field (E = -VXB) along the spacecraft trajectory. By combining this information with models of the magnetospheric interaction with Europa, one can generate 3D maps of the electric and magnetic field and compute the trajectories of the pickup ions back to the surface or exospheric points of origin. In the case of Ganymede there is the additional complexity of its own internal dipole magnetic field, while Io's volcanic activity introduces the complexity of a highly structured denser atmosphere. Callisto with its less globally extended exosphere will have a simpler interaction than for Europa (i.e., more like our moon). We will discuss these differences in light of the above proposed technique. Finally, the INNS observations and neutral exosphere models are needed to estimate production rates of pickup ions. The hot plasma measurements are needed to correct for sputtering rates which can be time dependent and electron plasma observations for electron impact ionization rates. Instrument characteristics, field-of-view requirements, modes of operation and effects of radiation on instrument functionality will be discussed.

Titan Ion Composition at Magnetosphere-Ionosphere Transition Region

NASA Technical Reports Server (NTRS)

Sittler, Edward C.; Hartle, R. E.; Shappirio, M.; Simpson, D. J.; COoper, J. F.; Burger, M. H.; Johnson, R. E.; Bertucci, C.; Luhman, J. G.; Ledvina, S. A.;

Workshop on Cometary Dust in Astrophysics

NASA Technical Reports Server (NTRS)

2003-01-01

The paper include contribution of each Lunar and Planetary Institute. Contents include the following: Mass flux in the ancient Earth-Moon system and benign implications for the origin of life on Earth. In-situ analysis of complex organic matter in cometary dust by ion microprobe. Pristine presolar silicon carbide. Infrared spectra of melilite solid solution. Comet observations with SIRTF. Ice and carbon chemistry in comets. The nature in interstellar dust. Modeling the infrared emission from protoplanetary dust disks.

The atmosphere of a dirty-clathrate cometary nucleus - A two-phase, multifluid model

NASA Astrophysics Data System (ADS)

Marconi, M. L.; Mendis, D. A.

1983-10-01

The dynamical and thermal structure of a dirty-clathrate cometary nucleus' gas atmosphere is presently given a self-consistent, transonic multifluid solution in which, although the heavy neutron and ion species are treated as a single fluid in the collision-dominated region, the photoproduced H is treated separately. The thermal profile of the atmosphere thus obtained is entirely different from those predicted by the earlier, single-fluid models as well as the multifluid models which assumed equipartition of energy between electrons and ions. While the electron gas, like the neutrals and the ions, cools due to expansion, its main mode of energy loss in the inner coma is by way of inelastic collisions with the predominant H2O molecule. The high electron temperature in the outer coma also decreases the efficiency of electron removal by dissociative recombination, thereby increasing electron density throughout the coma.

Ultraviolet spectrophotometry of Comet Giacobini-Zinner during the ICE encounter. [International Cometary Explorer

NASA Technical Reports Server (NTRS)

Mcfadden, Lucy A.; Ahearn, Michael F.; Feldman, Paul D.; Boehnhardt, Hermann; Rahe, Juergen; Festou, Michel C.; Brandt, John C.; Maran, Stephen P.; Niedner, Malcolm B.; Smith, Andrew M.

1987-01-01

The IUE's UV spectrophotometer was used to monitor Comet Giacobini-Zinner's H2O production rate from June to October, 1985, in support of the International Cometary Explorer (ICE) mission. Observation results for the spatial and temporal variation and the abundance or upper limits of C, CO, CO(+), CO2(+), CS, H, Mg(+), O, OH, and S, between September 9 and 12, included the time of the ICE encounter: at this time, the H2O production rate obtained was consistent with a number of gas production rates derived indirectly from the ICE experiments. A comparison of the CO2(+) ion abundance with the total electron density measured by the plasma electron and radio science experiments on ICE implies an ion deficiency relative to electrons, so that the satisfaction of charge balance criteria requires the presence of a major ion population not detected by remote sensing.

Mass spectra of heavy ions near comet Halley

NASA Astrophysics Data System (ADS)

Korth, A.; Richter, A. K.; Loidl, A.; Anderson, K. A.; Carlson, C. W.; Curtis, D. W.; Lin, R. P.; Reme, H.; Sauvaud, J. A.; D'Uston, C.; Cotin, F.; Cros, A.; Mendis, D. A.

1986-05-01

The heavy-ion analyser aboard the Giotto spacecraft, detected the first cometary ions at a distance of ≡1.05x106km from the nucleus of comet Halley. In the inner coma the major ions identified are associated with the H2O, CO and CO2 groups. Ions of larger atomic mass unit are also present, corresponding possibly to various hydrocarbons, heavy metals of the iron-group or to sulphur compounds.

Mass spectra of heavy ions near comet Halley

NASA Technical Reports Server (NTRS)

Korth, A.; Richter, A. K.; Loidl, A.; Anderson, K. A.; Carlson, C. W.

1986-01-01

The heavy-ion analyzer, RPA2-PICCA, aboard the Giotto spacecraft, detected the first cometary ions at a distance of about 1.05 million km from the nucleus of comet Halley. In the inner coma the major ions identified are associated with the H2O, CO and CO2 groups. Ions of larger atomic mass unit are also present, corresponding possibly to various hydrocarbons, heavy metals of the iron-group or to sulphur compounds.

Multifluid MHD Simulations of the Plasma Environment of Comet Churyumov-Gerasimenko at Different Heliocentric Distances

NASA Astrophysics Data System (ADS)

Huang, Z.; Jia, X.; Rubin, M.; Fougere, N.; Gombosi, T. I.; Tenishev, V.; Combi, M. R.; Bieler, A. M.; Toth, G.; Hansen, K. C.; Shou, Y.

2014-12-01

We study the plasma environment of the comet Churyumov-Gerasimenko, which is the target of the Rosetta mission, by performing large scale numerical simulations. Our model is based on BATS-R-US within the Space Weather Modeling Framework that solves the governing multifluid MHD equations, which describe the behavior of the cometary heavy ions, the solar wind protons, and electrons. The model includes various mass loading processes, including ionization, charge exchange, dissociative ion-electron recombination, as well as collisional interactions between different fluids. The neutral background used in our MHD simulations is provided by a kinetic Direct Simulation Monte Carlo (DSMC) model. We will simulate how the cometary plasma environment changes at different heliocentric distances.

Medium-energy electrons and heavy ions in Jupiter's magnetosphere - Effects of lower hybrid wave-particle interactions

NASA Technical Reports Server (NTRS)

Barbosa, D. D.

1986-01-01

A theory of medium-energy (about keV) electrons and heavy ions in Jupiter's magnetosphere is presented. Lower hybrid waves are generated by the combined effects of a ring instability of neutral wind pickup ions and the modified two-stream instability associated with transport of cool Iogenic plasma. The quasi-linear energy diffusion coefficient for lower hybrid wave-particle interactions is evaluated, and several solutions to the diffusion equation are given. Calculations based on measured wave properties show that the noise substantially modifies the particle distribution functions. The effects are to accelerate superthermal ions and electrons to keV energies and to thermalize the pickup ions on time scales comparable to the particle residence time. The S(2+)/S(+) ratio at medium energies is a measure of the relative contribution from Iogenic thermal plasma and neutral wind ions, and this important quantity should be determined from future measurements. The theory also predicts a preferential acceleration of heavy ions with an accleration time that scales inversely with the root of the ion mass. Electrons accelerated by the process contribute to further reionization of the neutral wind by electron impact, thus providing a possible confirmation of Alfven's critical velocity effect in the Jovian magnetosphere.

Multifluid Simulations of the Global Solar Wind Including Pickup Ions and Turbulence Modeling

NASA Technical Reports Server (NTRS)

Goldstein, Melvyn L.; Usmanov, A. V.

2011-01-01

I will describe a three-dimensional magnetohydrodynamic model of the solar wind that takes into account turbulent heating of the wind by velocity and magnetic fluctuations as well as a variety of effects produced by interstellar pickup protons. The interstellar pickup protons are treated in the model as one fluid and the protons and electrons are treated together as a second fluid. The model equations include a Reynolds decomposition of the plasma velocity and magnetic field into mean and fluctuating quantities, as well as energy transfer from interstellar pickup protons to solar wind protons that results in the deceleration of the solar wind. The model is used to simulate the global steady-state structure of the solar wind in the region from 0.3 to 100 AU. The simulation assumes that the background magnetic field on the Sun is either a dipole (aligned or tilted with respect to the solar rotation axis) or one that is deduced from solar magnetograms.

Chemical and Hydrodynamical Models of Cometary Comae

NASA Technical Reports Server (NTRS)

Charnley, Steven

2012-01-01

Multi-fluid modelling of the outflowing gases which sublimate from cometary nuclei as they approach the Sun is necessary for understanding the important physical and chemical processes occurring in this complex plasma. Coma chemistry models can be employed to interpret observational data and to ultimately determine chemical composition and structure of the nuclear ices and dust. We describe a combined chemical and hydrodynamical model [1] in which differential equations for the chemical abundances and the energy balance are solved as a function of distance from the cometary nucleus. The presence of negative ions (anions) in cometary comae is known from Giotto mass spectrometry of 1P/Halley. The anions O(-), OH(-), C(-), CH(-) and CN(-) have been detected, as well as unidentified anions with masses 22-65 and 85-110 amu [2]. Organic molecular anions such as C4H(-) and C6H(-) are known to have a significant impact on the charge balance of interstellar clouds and circumstellar envelopes and have been shown to act as catalysts for the gas-phase synthesis of larger hydrocarbon molecules in the ISM, but their importance in cometary comae has not yet been fully explored. We present details of new models for the chemistry of cometary comae that include atomic and molecular anions and calculate the impact of these anions on the coma physics and chemistry af the coma.

Observation of Bernstein Waves Excited by Newborn Interstellar Pickup Ions in the Solar Wind

NASA Technical Reports Server (NTRS)

Joyce, Colin J.; Smith, Charles W.; Isenberg, Philip A.; Gary, S. Peter; Murphy, Neil; Gray, Perry C.; Burlaga, Leonard F.

2012-01-01

A recent examination of 1.9 s magnetic field data recorded by the Voyager 2 spacecraft in transit to Jupiter revealed several instances of strongly aliased spectra suggestive of unresolved high-frequency magnetic fluctuations at 4.4 AU. A closer examination of these intervals using the highest resolution data available revealed one clear instance of wave activity at spacecraft frame frequencies from 0.2 to 1 Hz. Using various analysis techniques, we have characterized these fluctuations as Bernstein mode waves excited by newborn interstellar pickup ions. We can find no other interpretation or source consistent with the observations, but this interpretation is not without questions. In this paper, we report a detailed analysis of the waves, including their frequency and polarization, that supports our interpretation.

Determining the Interstellar Wind Longitudinal Inflow Evolution Using Pickup Ions in the Helium Focusing Cone

NASA Astrophysics Data System (ADS)

Spitzer, S. A.; Gilbert, J. A.; Lepri, S. T.

2017-12-01

We propose to determine the longitudinal inflow direction of the local interstellar medium through the Heliosphere. This longitudinal inflow direction directly correlates to the longitudinal direction of the helium focusing cone with respect to the Sun. We can calculate this direction by finding the He+ pickup ion density peak as mass spectrometers such as ACE/SWICS, Wind/STICS, and Helios/Micrometeoroid Detector and Analyzer pass through the focusing cone. Mapping from the location of this density peak to the Sun, around which the helium is focused, will directly yield the desired longitudinal direction. We will find this direction for each year since the first measurements in the 1970s through the present and thereby analyze its evolution over time. This poster outlines our proposed method and initial results.

Modeling the cometary environment using a fluid approach

NASA Astrophysics Data System (ADS)

Shou, Yinsi

Comets are believed to have preserved the building material of the early solar system and to hold clues to the origin of life on Earth. Abundant remote observations of comets by telescopes and the in-situ measurements by a handful of space missions reveal that the cometary environments are complicated by various physical and chemical processes among the neutral gases and dust grains released from comets, cometary ions, and the solar wind in the interplanetary space. Therefore, physics-based numerical models are in demand to interpret the observational data and to deepen our understanding of the cometary environment. In this thesis, three models using a fluid approach, which include important physical and chemical processes underlying the cometary environment, have been developed to study the plasma, neutral gas, and the dust grains, respectively. Although models based on the fluid approach have limitations in capturing all of the correct physics for certain applications, especially for very low gas density environment, they are computationally much more efficient than alternatives. In the simulations of comet 67P/Churyumov-Gerasimenko at various heliocentric distances with a wide range of production rates, our multi-fluid cometary neutral gas model and multi-fluid cometary dust model have achieved comparable results to the Direct Simulation Monte Carlo (DSMC) model, which is based on a kinetic approach that is valid in all collisional regimes. Therefore, our model is a powerful alternative to the particle-based model, especially for some computationally intensive simulations. Capable of accounting for the varying heating efficiency under various physical conditions in a self-consistent way, the multi-fluid cometary neutral gas model is a good tool to study the dynamics of the cometary coma with different production rates and heliocentric distances. The modeled H2O expansion speeds reproduce the general trend and the speed's nonlinear dependencies of production rate and heliocentric distance, which are found in remote observations. In the multi-fluid dust model, we use a newly developed numerical mesh to resolve the real shaped nucleus in the center and to facilitate prescription of the outer boundary conditions that accommodate the rotating frame. The model studies the effects of the rotating nucleus and the cometary activity in time-dependent simulations for the first time. The result also suggests that the rotation of the nucleus explains why there is no clear dust speed dependence on size in some of the dust observations. We developed a new multi-species comet MHD model to simulate the plasma environment of comet C/2006 P1 (McNaught) over a wide range of heliocentric distances from 0.17 AU to 1.75 AU, with the constraints provided by remote and in situ observations. Typical subsolar standoff distances of bow shock and contact surface are modeled and presented to characterize the solar wind interaction of the comet at various heliocentric distances. In addition, the model is also the first one to be used to study the composition and dynamics in the distant cometary tail. The results agree well with the measured water group ion abundances from the Ulysses/SWICS 1.7 AU down-tail from the comet and the velocity and temperature measured by Ulysses/SWOOPS.

The density of cometary protons upstream of Comet Halley's bow shock

NASA Astrophysics Data System (ADS)

Neugebauer, M.; Goldstein, B. E.; Balsiger, H.; Neubauer, F. M.; Schwenn, R.; Shelley, E. G.

1989-02-01

Cometary protons picked up by the solar wind were detected by the high energy range spectrometer of the Giotto ion mass spectrometer starting at a cometocentric distance of about 12 million km. On the average, the density of cometary protons varied approximately as the inverse square of the cometocentric distance, reaching a value of 0.11/cu cm just outside the bow shock. The data can be successfully fit to models that include substantial amounts of both slow (1 km/s) and fast (8 km/s or greater) H atoms beyond the bow shock. Large local variations in the density of picked-up protons can be explained on the basis of variations in the direction of the interplanetary magnetic field in upstream regions where pitch angle scattering was weak.

Characterization of biogenic elements in interplanetary dust particles

NASA Technical Reports Server (NTRS)

Bunch, T. E.

1986-01-01

Those particles that were designated cometary are aggregates of amorphous materials including carbon, iron-magnesium silicates, sulfides, metal and trace amounts of unusual phases. Most aggregates are carbon-rich with major and minor element abundances similar to a fine grained matrix of carbonaceous chondrites. Several particles were analyzed by a laser microprobe. The negative ionic species identified to date include carbon clusters, protonated carbon clusters, CN-, HCN-, CNO-, PO2-, PO3-, S-, S2- asnd OH-. These species are similar to those observed in cometary spectra and they support the assumption that organic materials are present. The occurance of phosphate ions suggests the presence of apatite or whitlockite. Cometary particle characteristics may indicate that the component grains represent primitive unaltered dust whose overall properties are extremely similar to altered primitive dust in carbonaceous chondrites.

VizieR Online Data Catalog: X-ray line ratios for diverse ion collisions (Mullen+, 2017)

NASA Astrophysics Data System (ADS)

Mullen, P. D.; Cumbee, R. S.; Lyons, D.; Gu, L.; Kaastra, J.; Shelton, R. L.; Stancil, P. C.

2018-03-01

Charge exchange (CX) has emerged in X-ray emission modeling as a significant process that must be considered in many astrophysical environments- particularly comets. Comets host an interaction between solar wind ions and cometary neutrals to promote solar wind charge exchange (SWCX). X-ray observatories provide astronomers and astrophysicists with data for many X-ray emitting comets that are impossible to accurately model without reliable CX data. Here, we utilize a streamlined set of computer programs that incorporate the multi-channel Landau-Zener theory and a cascade model for X-ray emission to generate cross sections and X-ray line ratios for a variety of bare and non-bare ion single electron capture (SEC) collisions. Namely, we consider collisions between the solar wind constituent bare and H-like ions of C, N, O, Ne, Na, Mg, Al, and Si and the cometary neutrals H2O, CO, CO2, OH, and O. To exemplify the application of this data, we model the X-ray emission of Comet C/2000 WM1 (linear) using the CX package in SPEX and find excellent agreement with observations made with the XMM-Newton RGS detector. Our analyses show that the X-ray intensity is dominated by SWCX with H, while H2O plays a secondary role. This is the first time, to our knowledge, that CX cross sections have been implemented into a X-ray spectral fitting package to determine the H to H2O ratio in cometary atmospheres. The CX data sets are incorporated into the modeling packages SPEX and Kronos. (1 data file).

NOVEL POLY-GLUTAMIC ACID FUNCTIONALIZED MICROFILTRATION MEMBRANES FOR SORPTION OF HEAVY METALS AT HIGH CAPACITY

EPA Science Inventory

Various sorbent/ion exchange materials have been reported in the literature for metal ion entrapment. We have developed a highly innovative and new approach to obtain high metal pick-up utilizing poly-amino acids (poly-L-glutamic acid, 14,000 MW) covalently attached to membrane p...

Ion bombardment experiments suggesting an origin for organic particles in pre-cometary and cometary ices

NASA Technical Reports Server (NTRS)

Wdowiak, Thomas J.; Robinson, Edward L.; Flickinger, Gregory C.; Boyd, David A.

1989-01-01

During the Giotto and Vega encounters with Comet Halley both organic particles called CHON and energetic ions were detected. The acceleration of ions to hundreds of keV in the vicinity of the bow shock and near the nucleus may be a demonstration of a situation occurring in the early solar system (perhaps during the T Tauri stage) that led to the formation of organic particles only now released. Utilizing a Van de Graaff accelerator and a target chamber having cryogenic and mass spectrometer capabilities, frozen gases were bombarded at 10 K with 175 keV protons with the result that fluffy solid material remains after sublimation of the ice. Initial experiments were carried out with a gas mixture in parts of 170 carbon monoxide, 170 argon, 25 water, 20 nitrogen, and 15 methane formulated to reflect an interstellar composition in experiments involving the freezing out of the products of a plasma. The plasma experiments resulted in a varnish-like film residue that exhibited luminescence when excited with ultraviolet radiation, while the ion bombardment created particulate material that was not luminescent.

Simulated orbits of heavy planetary ions at Mars for different IMF configurations

NASA Astrophysics Data System (ADS)

Curry, Shannon; Luhmann, Janet; Livi, Roberto; Hara, Takuya; Dong, Chuanfei; Ma, Yingjuan; McFadden, James; Bougher, Stephen

2014-11-01

We present simulated detections of O+, O2+ and CO2+ ions at Mars along a virtual orbit in the Mars space environment. Planetary pick-up ions are formed through the direct interaction of the solar wind with the neutral upper atmosphere, causing the newly created ions to be picked up and accelerated by the background convective electric field. Because previous missions such as Mars Global Surveyor (MGS) and Mars Express (MEX) have not been able to measure the interplanetary magnetic field (IMF) components simultaneously with plasma measurements, the response of heavy planetary pick-up ions to changes in the IMF has not been well characterized. Using a steady-state multi-species MHD model to provide the background electric and magnetic fields, the Mars Test Particle (MTP) simulation can trace each of these particles along field lines in near-Mars space and construct virtual ion detections from a spacecraft orbit. Specifically, we will present energy-time spectrograms and velocity space distributions (VSDs) for a selection of orbits during different IMF configurations and solar cycle conditions. These simulated orbits have broader implications for how to measure ion escape. Using individual particle traces, the origin and trajectories of different ion populations can be analyzed in order to assess how and where they contribute to the total atmospheric escape rate, which is a major objective of the upcoming MAVEN mission.

ULF waves in the Martian foreshock: MAVEN observations

NASA Astrophysics Data System (ADS)

Shan, Lican; Mazelle, Christian; Meziane, Karim; Ruhunusiri, Suranga; Espley, Jared; Halekas, Jasper; Connerney, Jack; McFadden, Jim; Mitchell, Dave; Larson, Davin; Brain, Dave; Jakosky, Bruce; Ge, Yasong; Du, Aimin

2016-04-01

Foreshock ULF waves constitute a significant physical phenomenon of the plasma environment for terrestrial planets. The occurrence of these ULF waves, associated with backstreaming ions reflected and accelerated at the bow shock, implies specific conditions and properties of the shock and its foreshock. Using measurements from MAVEN, we report clear observations of this type of ULF waves in the Martian foreshock. We show from different case studies that the peak frequency of the wave case in spacecraft frame is too far from the local ion cyclotron frequency to be associated with local pickup ions taking into account the Doppler shifted frequency from a cyclotron resonance, the obliquity of the mode, resonance broadening and experimental uncertainties. On the opposite their properties fit very well with foreshock waves driven unstable by backtreaming field-aligned ion beams. The propagation angle is usually less than 30 degrees from ambient magnetic field. The waves also display elliptical and left-hand polarizations with respect to interplanetary magnetic field in the spacecraft frame. It is clear for these cases that foreshock ions are simultaneous present for the ULF wave interval. Such observation is important in order to discriminate with the already well-reported pickup ion (protons) waves associated with exospheric hydrogen in order to quantitatively use the later to study seasonal variations of the hydrogen corona.

MAVEN Observations of Escaping Planetary Ions from the Martian Atmosphere: Mass, Velocity, and Spatial Distributions

NASA Astrophysics Data System (ADS)

Dong, Yaxue; Fang, Xiaohua; Brain, D. A.; McFadden, James P.; Halekas, Jasper; Connerney, Jack

2015-04-01

The Mars-solar wind interaction accelerates and transports planetary ions away from the Martian atmosphere through a number of processes, including ‘pick-up’ by electromagnetic fields. The MAVEN spacecraft has made routine observations of escaping planetary ions since its arrival at Mars in September 2014. The SupraThermal And Thermal Ion Composition (STATIC) instrument measures the ion energy, mass, and angular spectra. It has detected energetic planetary ions during most of the spacecraft orbits, which are attributed to the pick-up process. We found significant variations in the escaping ion mass and velocity distributions from the STATIC data, which can be explained by factors such as varying solar wind conditions, contributions of particles from different source locations and different phases during the pick-up process. We also study the spatial distributions of different planetary ion species, which can provide insight into the physics of ion escaping process and enhance our understanding of atmospheric erosion by the solar wind. Our results will be further interpreted within the context of the upstream solar wind conditions measured by the MAVEN Solar Wind Ion Analyzer (SWIA) instrument and the magnetic field environment measured by the Magnetometer (MAG) instrument. Our study shows that the ion spatial distribution in the Mars-Sun-Electric-Field (MSE) coordinate system and the velocity space distribution with respect to the local magnetic field line can be used to distinguish the ions escaping through the polar plume and those through the tail region. The contribution of the polar plume ion escape to the total escape rate will also be discussed.

The singing comet 67P: utilizing fully kinetic simulations to study its interaction with the solar wind plasma

NASA Astrophysics Data System (ADS)

Deca, J.; Divin, A. V.; Horanyi, M.; Henri, P.

2016-12-01

We present preliminary results of the first 3-D fully kinetic and electromagnetic simulations of the solar wind interaction with 67P/Churyumov-Gerasimenko at 3 AU, before the comet transitions into its high-activity phase. We focus on the global cometary environment and the electron-kinetic activity of the interaction. In addition to the background solar wind plasma flow, our model includes also plasma-driven ionization of cometary neutrals and collisional effects. We approximate mass loading of cold cometary oxygen and hydrogen using a hyperbolic relation with distance to the comet. We consider two primary cases: a weak outgassing comet (with the peak ion density 10x the solar wind density) and a moderately outgassing comet (with the peak ion density 50x the solar wind density). The weak comet is characterized by the formation of a narrow region containing a compressed solar wind (the density of the solar wind ion population is 3x the value far upstream of the comet) and a magnetic barrier ( 2x to 4x the interplanetary magnetic field). Blobs of plasma are detached continuously from this sheath region. Standing electromagnetic waves are excited in the cometary wake due to a strong anisotropy in the plasma pressure, as the density and the magnetic field magnitude are anti-correlated.The moderate mass-loading case shows more dynamics at the dayside region. The stagnation of the solar wind flow is accompanied by the formation of elongated density stripes, indicating the presence of a Rayleigh-Taylor instability. These density cavities are elongated in the direction of the magnetic field and encompass the dayside ionopause. To conclude, we believe that our results provide vital information to disentangle the observations made by the Rosetta spacecraft and compose a global solar wind - comet interaction model.

A radio source occultation experiment with comet Austin 1982g, with unusual results

NASA Technical Reports Server (NTRS)

De Pater, I.; Ip, W.-H.

1984-01-01

A radio source occultation by comet Austin 1982g was observed on September 15-16, 1982. A change in the apparent position of 1242 + 41 by 1.3 arcsec occurred when the source was 220,000 km away from the cometary ion tail. If this change was due to refraction by the cometary plasma, it indicates an electron density of the plasma of about 10,000/cu cm. When the radio source was on the other side of the plasma tail, at a distance of 230,000 km, the position angle of the electric vector of the radio source changed gradually over about 140 deg within two hours. This observation cannot be explained in terms of ionospheric Faraday rotation, and results from either an intrinsic change in the radio source or Faraday rotation in the cometary plasma due to a change in the direction and/or strength of the magnetic field. In the latter case, the cometary coma must have an electron density and a magnetic field strength orders of magnitude larger than current theories predict.

Analysis of the Cometary Plasma Environment of 67P/Churyumov-Gerasimenko Near Perihelion

NASA Astrophysics Data System (ADS)

Ostaszewski, K.; Goetz, C.; Motschmann, U.; Glassmeier, K. H.

2017-09-01

Over the course of its two year escort phase the Rosetta spacecraft has provided various observations that furthered our understanding of the cometary plasma environment. The use of numerical simulations is essential for this understanding because they allow to place the in situ measurements in a global context, in turn, through observations the numerical models can be ex- tended and improved. We use the simulation code A.I.K.E.F (Müller [7]) to simulate the cometary plasma environment of 67P/Churyumov-Gerasimenko (67P/CG). Based on observations made by the Rosetta spacecraft we extend the numerical model by electron impact ionization and the anisotropic outgassing model by Hansen et al. (2016). Both extensions result in an increase in the cometary ion production rate on the dayside. Therefore, the size of the interaction region and the contained structures increases. This causes the position of the different boundaries, e.g. bow shock, to shift further away from the comet. Considering this we can explain why no bow shock crossings could be observed during the dayside excursion of Rosetta in September 2015.

THE IBEX RIBBON AND THE PICKUP ION RING STABILITY IN THE OUTER HELIOSHEATH. II. MONTE-CARLO AND PARTICLE-IN-CELL MODEL RESULTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Niemiec, J.; Florinski, V.; Heerikhuisen, J.

2016-08-01

The nearly circular ribbon of energetic neutral atom (ENA) emission discovered by NASA’s Interplanetary Boundary EXplorer satellite ( IBEX ), is most commonly attributed to the effect of charge exchange of secondary pickup ions (PUIs) gyrating about the magnetic field in the outer heliosheath (OHS) and the interstellar space beyond. The first paper in the series (Paper I) presented a theoretical analysis of the pickup process in the OHS and hybrid-kinetic simulations, revealing that the kinetic properties of freshly injected proton rings depend sensitively on the details of their velocity distribution. It was demonstrated that only rings that are notmore » too narrow (parallel thermal spread above a few km s{sup −1}) and not too wide (parallel temperature smaller than the core plasma temperature) could remain stable for a period of time long enough to generate ribbon ENAs. This paper investigates the role of electron dynamics and the extra spatial degree of freedom in the ring ion scattering process with the help of two-dimensional full particle-in-cell (PIC) kinetic simulations. A good agreement is observed between ring evolution under unstable conditions in hybrid and PIC models, and the dominant modes are found to propagate parallel to the magnetic field. We also present more realistic ribbon PUI distributions generated using Monte Carlo simulations of atomic hydrogen in the global heliosphere and examine the effect of both the cold ring-like and the hot “halo” PUIs produced from heliosheath ENAs on the ring stability. It is shown that the second PUI population enhances the fluctuation growth rate, leading to faster isotropization of the solar-wind-derived ring ions.« less

The IBEX Ribbon and the Pickup Ion Ring Stability in the Outer Heliosheath II. Monte-Carlo and Particle-in-cell Model Results

NASA Astrophysics Data System (ADS)

Niemiec, J.; Florinski, V.; Heerikhuisen, J.; Nishikawa, K.-I.

2016-08-01

The nearly circular ribbon of energetic neutral atom (ENA) emission discovered by NASA’s Interplanetary Boundary EXplorer satellite (IBEX), is most commonly attributed to the effect of charge exchange of secondary pickup ions (PUIs) gyrating about the magnetic field in the outer heliosheath (OHS) and the interstellar space beyond. The first paper in the series (Paper I) presented a theoretical analysis of the pickup process in the OHS and hybrid-kinetic simulations, revealing that the kinetic properties of freshly injected proton rings depend sensitively on the details of their velocity distribution. It was demonstrated that only rings that are not too narrow (parallel thermal spread above a few km s-1) and not too wide (parallel temperature smaller than the core plasma temperature) could remain stable for a period of time long enough to generate ribbon ENAs. This paper investigates the role of electron dynamics and the extra spatial degree of freedom in the ring ion scattering process with the help of two-dimensional full particle-in-cell (PIC) kinetic simulations. A good agreement is observed between ring evolution under unstable conditions in hybrid and PIC models, and the dominant modes are found to propagate parallel to the magnetic field. We also present more realistic ribbon PUI distributions generated using Monte Carlo simulations of atomic hydrogen in the global heliosphere and examine the effect of both the cold ring-like and the hot “halo” PUIs produced from heliosheath ENAs on the ring stability. It is shown that the second PUI population enhances the fluctuation growth rate, leading to faster isotropization of the solar-wind-derived ring ions.

On the development and global oscillations of cometary ionospheres

NASA Technical Reports Server (NTRS)

Houpis, H. L. F.; Mendis, D. A.

1981-01-01

Representing the cometary ionosphere by a single fluid model characterized by an average ionization time scale, both the ionosphere's development as a comet approaches the sun and its response to sudden changes in solar wind conditions are investigated. Three different nuclear sizes (small, average, very large) and three different modes of energy addition to the atmosphere (adiabatic, isothermal, suprathermal) are considered. It is found that the crucial parameter determining both the nature and the size of the ionosphere is the average ionization time scale within the ionosphere. Two different scales are identified. It is noted that the ionosphere can also be characterized by the relative sizes of three different scale lengths: the neutral standoff distance from the nucleus, the ion standoff distance from the nucleus, and the nuclear distance at which the ions and the neutrals decouple collisionally.

Loss of Water from Saturn's E-Ring Through Ion Pick-Up

NASA Technical Reports Server (NTRS)

Leisner, J. S.; Russell, C. T.; Dougherty, M. K.; Blanco-Cano, X.; Smith, E. J.; Tsurutani, B. T.

2005-01-01

One of the possible loss processes for Saturn s E-ring is ionization followed by acceleration by the electric field associated with the corotating magnetized plasma. It is possible to determine if this process is occurring by detecting electromagnetic waves at the gyrofrequency of water group ions. If the energy the particle gains in this pick-up process is sufficiently great, the picked up ions will generate ion cyclotron waves. Pioneer 11 and Voyager 1 both observed intervals of such waves associated with water group ions during their passes through Saturn s E-ring. Presently the magnetometer onboard the Cassini spacecraft is also seeing water group ion cyclotron oscillations. The Cassini data allow the spatial and temporal behavior of the waves to be mapped in ways not possible during the previous flybys. Analyses of these waves allow us to study the rate of mass loading and its latitudinal and local time variation. In conjunction with previous data, we can then determine the variation as the inclination of the ring to the Sun changes, in accordance with Saturn's seasons. These waves may be the clue to how Saturn powers its magnetosphere as the newly born ions could be the driver for the radial motion of the plasma and to how the E-ring may play the equivalent role to that of Io in the jovian magnetosphere.

Cometary coma ions. [which occur when water is the major constituent

NASA Technical Reports Server (NTRS)

Aikin, A. C.

1974-01-01

For comets whose nuclei are composed of water ice conglomerates it is shown that the ion H3O(+) can predominate to distances of 5000 km in the subsolar direction. Beyond this distance H2O(+) is the most important ion. The crossover point is a sensitive function of the rate of evaporation from the nucleus. The presence of ammonia or metals such as sodium, in concentrations greater than 0.1% H2O, can lead to NH4(+) and Na(+) ions.

A cometary ion mass spectrometer

NASA Technical Reports Server (NTRS)

Shelley, E. G.; Simpson, D. A.

1984-01-01

The development of flight suitable analyzer units for that part of the GIOTTO Ion Mass Spectrometer (IMS) experiment designated the High Energy Range Spectrometer (HERS) is discussed. Topics covered include: design of the total ion-optical system for the HERS analyzer; the preparation of the design of analyzing magnet; the evaluation of microchannel plate detectors and associated two-dimensional anode arrays; and the fabrication and evaluation of two flight-suitable units of the complete ion-optical analyzer system including two-dimensional imaging detectors and associated image encoding electronics.

Note: Low temperature superconductor superconducting quantum interference device system with wide pickup coil for detecting small metallic particles

NASA Astrophysics Data System (ADS)

Kandori, Akihiko; Ogata, Kuniomi; Kawabata, Ryuzo; Tanimoto, Sayaka; Seki, Yusuke

2012-07-01

A one-channel low temperature superconductor superconducting quantum interference device system comprising a second-order axial gradiometer with a sensing area of 10 mm × 190 mm was developed. The gradiometer was mounted in a liquid-helium dewar (450-mm diameter; 975-mm length), with a gap of 12 mm between the pickup coil and the dewar-tail surface. The magnetic field sensitivity was measured to be 16 fT/Hz1/2 in the white noise regime above 2 Hz. The system was used to measure stainless steel particles of different sizes passing through the sensing area. A 100-μm diameter SUS304 particle was readily detected passing at different positions underneath the large pickup coil by measuring its 1.3-pT magnetic field. Thus, the system was shown to be applicable to quality control of lamination sheet products such as lithium ion batteries.

Challenges in the determination of the interstellar flow longitude from the pickup ion cutoff

NASA Astrophysics Data System (ADS)

Taut, A.; Berger, L.; Möbius, E.; Drews, C.; Heidrich-Meisner, V.; Keilbach, D.; Lee, M. A.; Wimmer-Schweingruber, R. F.

2018-03-01

Context. The interstellar flow longitude corresponds to the Sun's direction of movement relative to the local interstellar medium. Thus, it constitutes a fundamental parameter for our understanding of the heliosphere and, in particular, its interaction with its surroundings, which is currently investigated by the Interstellar Boundary EXplorer (IBEX). One possibility to derive this parameter is based on pickup ions (PUIs) that are former neutral ions that have been ionized in the inner heliosphere. The neutrals enter the heliosphere as an interstellar wind from the direction of the Sun's movement against the partially ionized interstellar medium. PUIs carry information about the spatial variation of their neutral parent population (density and flow vector field) in their velocity distribution function. From the symmetry of the longitudinal flow velocity distribution, the interstellar flow longitude can be derived. Aim. The aim of this paper is to identify and eliminate systematic errors that are connected to this approach of measuring the interstellar flow longitude; we want to minimize any systematic influences on the result of this analysis and give a reasonable estimate for the uncertainty. Methods: We use He+ data measured by the PLAsma and SupraThermal Ion Composition (PLASTIC) sensor on the Solar TErrestrial RElations Observatory Ahead (STEREO A) spacecraft. We analyze a recent approach, identify sources of systematic errors, and propose solutions to eliminate them. Furthermore, a method is introduced to estimate the error associated with this approach. Additionally, we investigate how the selection of interplanetary magnetic field angles, which is closely connected to the pickup ion velocity distribution function, affects the result for the interstellar flow longitude. Results: We find that the revised analysis used to address part of the expected systematic effects obtains significantly different results than presented in the previous study. In particular, the derived uncertainties are considerably larger. Furthermore, an unexpected systematic trend of the resulting interstellar flow longitude with the selection of interplanetary magnetic field orientation is uncovered.

A comb-sampling method for enhanced mass analysis in linear electrostatic ion traps.

PubMed

Greenwood, J B; Kelly, O; Calvert, C R; Duffy, M J; King, R B; Belshaw, L; Graham, L; Alexander, J D; Williams, I D; Bryan, W A; Turcu, I C E; Cacho, C M; Springate, E

2011-04-01

In this paper an algorithm for extracting spectral information from signals containing a series of narrow periodic impulses is presented. Such signals can typically be acquired by pickup detectors from the image-charge of ion bunches oscillating in a linear electrostatic ion trap, where frequency analysis provides a scheme for high-resolution mass spectrometry. To provide an improved technique for such frequency analysis, we introduce the CHIMERA algorithm (Comb-sampling for High-resolution IMpulse-train frequency ExtRAaction). This algorithm utilizes a comb function to generate frequency coefficients, rather than using sinusoids via a Fourier transform, since the comb provides a superior match to the data. This new technique is developed theoretically, applied to synthetic data, and then used to perform high resolution mass spectrometry on real data from an ion trap. If the ions are generated at a localized point in time and space, and the data is simultaneously acquired with multiple pickup rings, the method is shown to be a significant improvement on Fourier analysis. The mass spectra generated typically have an order of magnitude higher resolution compared with that obtained from fundamental Fourier frequencies, and are absent of large contributions from harmonic frequency components. © 2011 American Institute of Physics

Preliminary results seen with Rosetta/ROSINA: early cometary activity of 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Gasc, Sebastien; Altwegg, Kathrin; Jäckel, Annette; Rubin, Martin; Tzou, Chia-Yu; Wurz, Peter; Fiethe, Björn; Korth, Axel; Rème, Henri

2014-11-01

On 1 August 2014, the ROSETTA spacecraft approached the comet 67P/Churyumov-Gerasimenko (67P/CG) close enough to start its detailed characterisation. In this phase, the distance between Rosetta and 67P/CG is below 1’000 km, at a heliocentric distance of less than 3.6 AU. The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) [1] measures the composition of 67P/CG’s atmosphere and ionosphere, and additionally derives the bulk velocity of gas. ROSINA consists of the COmetary Pressure Sensor (COPS) and two mass spectrometers for the analysis of neutral gas and cometary ions in the coma of the comet: the Double Focusing Mass Spectrometer (DFMS) and the Reflectron Time Of Flight mass spectrometer (RTOF). Since beginning of August, the ROSINA sensors are continuously monitoring the density and chemical composition of the coma of 67P/CG. The goal of this work is not only to determine the abundance of major species like CO2, CO, and H2O, but also to analyse the development of the composition as a function of the heliocentric distance. We will present the first mass spectra of RTOF as well as the total density and the molecular composition measurements obtained at 67P/CG.

The International Cometary Explorer (ICE) mission to comet Giacobini-Zinner (G/Z)

NASA Technical Reports Server (NTRS)

Brandt, J. C.; Farquhar, R. W.; Maran, S. P.; Niedner, M. B.; Von Rosenvinge, T.

1985-01-01

The primary objectives of the International Cometary Explorer (ICE) mission is to provide in situ data on the interaction between solar wind and the atmosphere of the P/Giacobini-Zinner comet (G/Z), making measurements of particles, fields, and waves while passing through the cometary tail of G/Z on September 11, 1985. Following the G/Z tail intercept, the ICE measurements will complement the later upstream measurements obtained by the Comet Halley probe. The major ICE payload includes a vector helium magnetometer, the plasma-wave experiment, the radio-wave experiment, the plasma-electron experiment, and the plasma ion experiment. Other experiments are intended to measure energetic protons, X-rays, low energy to high energy cosmic rays, cosmic ray electrons, and gamma-ray bursts. The ICE measurements of G/Z will be supplemented with ground-based measurements. Schematic diagrams are included.

An investigation of solar wind effects on the evolution of the Martian atmosphere

NASA Technical Reports Server (NTRS)

Luhmann, Janet G.

1994-01-01

This investigation concentrated on the question of how atmosphere escape, related to both photochemistry and the Mars solar wind interaction, may have affected the evolution of Mars' atmosphere over time. The principal investigator and postdoctoral researcher adopted the premise that contemporary escape processes have dominated the losses to space over the past 3.5 billion years, but that the associated loss rates have been modified by solar evolution. A model was constructed for the contemporary escape scenario based on knowledge gained from both Venus in-situ measurements from Pioneer Venus Orbiter and Mars measurements from Phobos-2. Venus provided a valuable second example of a weakly magnetized planet having a similar solar wind interaction where we have more knowledge from observations. The model included photochemical losses from recombining ionospheric molecular ions, scavenging Martian upper atmosphere ('pickup') ions by the solar wind, and sputtering of the atmosphere by reentering pickup ions. The existence of the latter mechanism was realized during the course of the supported investigation, and is now thought by Jakosky and Pepin to explain some of the Martian noble gas isotope ratios.

Numerical and Analytical Investigation of the Energy and Momentum Exchange Between the Shocked Solar Wind and Topside Ionosphere for Non-Magnetic Planets and Moons

NASA Astrophysics Data System (ADS)

Dobe, Z.; Shapiro, V. D.; Quest, K.; Szego, K.; Huba, J.

1998-11-01

Previously[1], we proposed a model of the planetary ions pick-up by the shocked solar wind flow developing in the mantle-turbulent boundary region surrounding the ionospheres of non-magnetic planets-Mars and Venus. In the present paper we are modifying this model taking into account the flow of the planetary elections immediately pick-up by E x B forces of the shocked solar wind. It is shown that flow of the cold planetary electrons drives a strong hydrodynamical instability of the electrostatic whistlers efficiently coupling planetary ions with the flow of the solar wind. The linear stage of the instability is investigated both analytically and numerically, and results are found to be in a good agreement. Nonlunear stage of the instability is investigated with the modified numerical hybrid code[2], and demonstrates both effects of acceleration and heating of the planetary ions by the solar wind. Field aligned electron acceleration is also investigated in a test particle approximation using wave power spectrum obtained in a self-consistent numerical simulation.

Iogenic Plasma and its Rotation-Driven Transport in Jupiter's Magnetosphere

NASA Technical Reports Server (NTRS)

Smyth, William H.

2001-01-01

Model calculations are reported for the Iogenic plasma source created by atomic oxygen and sulfur above Io's exobase in the corona and extended clouds (Outer Region). On a circumplanetary scale, two-dimensional distributions produced by integrating the proper three dimensional rate information for electron impact and charge exchange processes along the magnetic field lines are presented for the pickup ion rates, the net-mass and total-mass loading rates, the mass per unit magnetic flux rate, the pickup conductivity, the radial pickup current, and the net-energy loading rate for the plasma torus. All of the two-dimensional distributions are highly peaked at Io's location and hence highly asymmetric about Jupiter. The Iogenic plasma source is also calculated on a much smaller near-Io scale to investigate the structure of the highly peak rates centered about lo's instantaneous location. The Iogenic plasma source for the Inner Region (pickup rates produced below Io's exobase) is, however, expected to be the dominant source near lo for the formation of the plasma torus ribbon and to be a comparable source, if not a larger contributor, to the energy budget of the plasma torus, so as to provide the necessary power to sustain the plasma torus radiative loss rate.

Line Ratios for Solar Wind Charge Exchange with Comets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mullen, P. D.; Cumbee, R. S.; Lyons, D.

Charge exchange (CX) has emerged in X-ray emission modeling as a significant process that must be considered in many astrophysical environments—particularly comets. Comets host an interaction between solar wind ions and cometary neutrals to promote solar wind charge exchange (SWCX). X-ray observatories provide astronomers and astrophysicists with data for many X-ray emitting comets that are impossible to accurately model without reliable CX data. Here, we utilize a streamlined set of computer programs that incorporate the multi-channel Landau–Zener theory and a cascade model for X-ray emission to generate cross sections and X-ray line ratios for a variety of bare and non-baremore » ion single electron capture (SEC) collisions. Namely, we consider collisions between the solar wind constituent bare and H-like ions of C, N, O, Ne, Na, Mg, Al, and Si and the cometary neutrals H{sub 2}O, CO, CO{sub 2}, OH, and O. To exemplify the application of this data, we model the X-ray emission of Comet C/2000 WM1 (linear) using the CX package in SPEX and find excellent agreement with observations made with the XMM-Newton RGS detector. Our analyses show that the X-ray intensity is dominated by SWCX with H, while H{sub 2}O plays a secondary role. This is the first time, to our knowledge, that CX cross sections have been implemented into a X-ray spectral fitting package to determine the H to H{sub 2}O ratio in cometary atmospheres. The CX data sets are incorporated into the modeling packages SPEX and Kronos .« less

Pick-Up Ion Instabilities at Planetary Magnetospheres

NASA Technical Reports Server (NTRS)

Strangeway, Robert J.; Sharber, James (Technical Monitor)

2001-01-01

This effort involved the analysis of low frequency waves as observed by the Galileo spacecraft near the Galilean moon, Io. Io is a significant source of material, especially SO2, and various products of dissociation, and further these atoms and molecules are readily ionized. The initial velocity of the ions is essentially that of the neutral species, i.e., the Keplerian velocity. The plasma, on the other hand is co-rotating, and there is a differential flow of the order 57 km/s between the plasma and the neutral particles. Thus pick-up ion instabilities are Rely to occur within the Jovian magnetosphere. Indeed, magnetometer observations from the Galileo spacecraft clearly show ion cyclotron waves that have been identified with a large variety of plasma species, such as O+, S++ (which has the same gyro-frequency as O+), S+, and SO2+. Typically, however, the dominant frequency is near the SO2+ gyro-frequency. The research effort was originally planned to be a team effort between Robert J. Strangeway as the Principal Investigator, and Debbie Huddleston, who was an Assistant Research Geophysicist at UCLA. Unfortunately, Dr. Huddleston took a position within Industry. The effort was therefore descoped, and Dr. Strangeway instead pursued a collaboration with Dr. Xochitl Blanco-Cano, of the Instituto de Geofisica, Universidad Nacional Autonoma de Mexico. This has proved to be a productive collaboration, with several papers and publications arising out of the effort. The magnetic field oscillations near lo generally fall into two types: ion cyclotron waves, with frequencies near an ion gyro-frequency, and lower frequency mirror-mode waves. The ion cyclotron waves are mainly transverse, and frequently propagate along the ambient magnetic field. The mirror-mode waves are compressional waves, and they have essentially zero frequency in the plasma rest frame. One of the purposes of our investigation is to understand what controls the types of wave modes that occur, since both wave modes can be drive unstable by the pressure anisotropy associated with the pick up ions. The pick ion velocity is perpendicular to the ambient magnetic field, and is generally much larger than the thermal velocity, at least initially. At its simplest, we found that the ion cyclotron waves are controlled by the parameters of the species in gyro-resonance with the wave. Thus, while the growth rates for the lower mass (higher gyro-frequency) pick-up ions are generally larger, we found that the heavier SO2+ ion cyclotron waves are generally preferred. This is because one of the effects of the wave instability is to diffuse the ions in pitch angle and energy. The lower mass ions therefore consist of both a ring of recently created pick-up ions, and a thermal background. This thermal background quenches the ion cyclotron instability. SO2+ is different, however. Being a molecule, the species can also dissociate. Our analysis suggests that the dissociation acts on a time scale comparable to or faster than the velocity space diffusion time scale. There are consequently no thermal SO2+ ions to quench the instability. We have also investigated the mirror-mode. This mode can at times grow more rapidly than the individual ion cyclotron waves. This is mainly because the mirror-mode can grow off the pressure anisotropy of the individual species with which the waves are in resonance. Lastly, as part of this effort we have begun to investigate the instability for obliquely propagating modes. Galileo observations show that at times the ion cyclotron waves are significantly elliptically polarized, and further the wave vector is at a large angle to the field, significant growth can occur for oblique propagation. Depending on the group velocity of the waves, it is possible that obliquely propagating modes have higher advective growth rate, but this has yet to be determined.

Sensitivity and fragmentation calibration of the time-of-flight mass spectrometer RTOF on board ESA's Rosetta mission

NASA Astrophysics Data System (ADS)

Gasc, Sébastien; Altwegg, Kathrin; Jäckel, Annette; Le Roy, Léna; Rubin, Martin; Fiethe, Björn; Mall, Urs; Rème, Henri

2014-05-01

The European Space Agency's Rosetta mission will rendez-vous comet 67P/Churyumov-Gerasimenko (67P) in September 2014. The Rosetta spacecraft with the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) onboard will follow and survey 67P for more than a year until the comet reaches its perihelion and beyond. ROSINA will provide new information on the global molecular, elemental, and isotopic composition of the coma [1]. ROSINA consists of a pressure sensor (COPS) and two mass spectrometers, the Double Focusing Mass Spectrometer (DFMS) and the Reflectron Time Of Flight mass spectrometer (RTOF). RTOF has a wide mass range, from 1 amu/e to >300 amu/e, and contains two ion sources, a reflectron and two detectors. The two ion sources, the orthogonal and the storage source, are capable to measure cometary ions while the latter also allows measuring cometary neutral gas. In neutral gas mode the ionization is performed through electron impact. A built-in Gas Calibration Unit (GCU) contains a known gas mixture composed of He, CO2, and Kr that can be used for in-flight calibration of the instrument. Among other ROSINA specific scientific goals, RTOF's task will be to determine molecular composition of volatiles via measuring and separating heavy hydrocarbons; it has been designed to study the development of the cometary activity as well as the coma chemistry between 3.5 AU and perihelion. From the spectroscopic studies and in-situ observations of other comets, we expect to find molecules such as H2O, CO, CO2, hydrocarbons, alcohols, formaldehyde, and other organic compounds in the coma of 67P/Churyumov-Gerasimenko [2]. To demonstrate and quantify the sensitivity and functionality of RTOF, calibration measurements have been realized with more than 20 species among the most abundant molecules quoted above, as well as other species such as PAHs. We will describe the applied methods used to realize this calibration and will discuss our preliminary results, i.e. RTOF capabilities in terms of sensitivity, isotopic ratios, and fragmentation patterns. We will demonstrate that RTOF is well capable to meet the requirements to address the scientific questions discussed above. [1] Balsiger, H. et al.: ROSINA-Rosetta Orbiter Spectrometer for Ion and Neutral Analysis, Space Science Reviews, Vol. 128, 745-801, 2007. [2] Bockelée-Morvan, D., Crovisier, J., Mumma, M. J., and Weaver, H. A.: The Composition of Cometary Volatiles, in Comets II (M. C. Festou et al., eds), Univ. Arizona Press, Tucson, 2004

Responses of the Jovian Atmosphere to Cometary Particles and Photon Impacts

NASA Technical Reports Server (NTRS)

Dalgarno, A.

1998-01-01

Spectra of soft x-ray and EUV emissions of oxygen ions, precipitating into the Jovian atmosphere, are calculated, taking into account the dynamical character of the energy and charge distributions of the ions as they propagate. Monte-Carlo simulations are performed using experimental and theoretical cross sections of ion collisions with the atmospheric gases. The numbers of x-ray and EUV photons produced per precipitating oxygen ion are calculated as functions of the initial ion energy and charge. The energy and charge distribution functions are used to evaluate the intensities of characteristic x-ray and EUV spectral emission lines of oxygen ions in the Jovian aurora.

Plasma IMS Composition Measurements for Europa and the Other Galilean Moons

NASA Astrophysics Data System (ADS)

Sittler, Edward; Cooper, John; Hartle, Richard; Lipatov, Alexander; Mahaffy, Paul; Paterson, William; Pachalidis, Nick; Coplan, Mike; Cassidy, Tim

2010-05-01

NASA and ESA are planning the joint Europa Jupiter System Mission (EJSM) to the Jupiter system with specific emphasis to Europa and Ganymede, respectively. The Japanese Space Agency is also planning an orbiter mission to explore Jupiter's magnetosphere and the Galilean satellites. For NASA's Jupiter Europa Orbiter (JEO) we are developing the 3D Ion Mass Spectrometer (IMS) with two main goals which can also be applied to the other Galilean moons, 1) measure the plasma interaction between Europa and Jupiter's magnetosphere and 2) infer the 4? surface composition to trace elemental [1] and significant isotopic levels. The first goal supports the magnetometer (MAG) measurements, primarily directed at detection of Europa's sub-surface ocean, while the second gives information about transfer of material between the Galilean moons, and between the moon surfaces and subsurface layers putatively including oceans. The measurement of the interactions for all the Galilean moons can be used to trace the in situ ion measurements of pickup ions back to either Europa's or Ganymede's surface from the respectively orbiting spacecraft. The IMS instrument, being developed under NASA's Astrobiology Instrument Development Program, would maximally achieve plasma measurement requirements for JEO and EJSM while moving forward our knowledge of Jupiter system composition and source processes to far higher levels than previously envisaged. The composition of the global surfaces of Europa and Ganymede can be inferred from the measurement of ejected neutrals and pick-up ions using at minimum an in situ payload including MAG and IMS also fully capable of meeting Level 1 mission requirements for ocean detection and survey. Elemental and isotopic analysis of potentially extruded oceanic materials at the moon surfaces would further support the ocean objectives. These measurements should be made from a polar orbiting spacecraft about Europa or Ganymede at height ~ 100 km. The ejecta produced by sputtering of the surfaces of Europa and Ganymede has been shown to be representative of the surface composition [2,3]. Level 2 science on surface geology and composition can then be further enhanced by addition of the following: 3D Ion Neutral Mass Spectrometer (INMS), 3D plasma electron spectrometer (ELS), and hot plasma energetic particle instrument. The measurement approach is to alternate between times measuring pickup ions and times measuring plasma and magnetic field parameters along the spacecraft trajectory. By measuring the pickup ion energy, arrival direction and mass-per-charge, the ion can be traced back along the ejection trajectory to the approximate area of origin if the 3-D electric field and magnetic field are known. In situ observations of plasma flow velocities and vector magnetic fields can be used to determine the local convective electric field (E = -VXB) along the spacecraft trajectory. By combining this information with models of the magnetospheric interaction with Europa [3,4], one can generate 3D maps of the electric and magnetic field and compute the trajectories of the pickup ions back to the surface or exospheric points of origin. In the case of Ganymede there is the additional complexity of its own internal dipole magnetic field, while Io's volcanic activity introduces the complexity of a highly structured denser atmosphere. Callisto with its less globally extended exosphere will have a simpler interaction than for Europa (i.e., more like our moon). We will discuss these differences in light of the above proposed technique. Finally, the INMS observations and neutral exosphere models are needed to estimate production rates of pickup ions. The hot plasma measurements are needed to correct for sputtering rates which can be time dependent and electron plasma observations for electron impact ionization rates. Instrument characteristics, field-of-view requirements, modes of operation and effects of radiation on instrument functionality will be discussed. 1. Cassidy, T. A., Johnson, R. E., Tucker, O. J., 2009. Trace constituents of Europa's atmosphere. Icarus 201, 182-190. 2. Johnson, R. E., et al., Europa (ed R. Pappalardo et al.), Univ of Arizona Press, in press, 2009. 3. Schilling, N., Neubauer, F. M., Saur, J., 2008. Influence of the internally induced magnetic field on the plasma interaction of Europa. Journal of Geophysical Research (Space Physics) 113, 3203. 4. Lipatov, A. S., Cooper, J. F., Paterson, W. R., Sittler, E. C., and Hartle, R. E., Jovian's plasma torus interaction with Europa: 3D Hybrid kinetic simulation. First results, submitted to Plan. Sp. Sci., 2009.

Evolution of Cometary Activity at 67P/Churyumov-Gerasimenko as seen by ROSINA/Rosetta

NASA Astrophysics Data System (ADS)

Jäckel, A.; Altwegg, K.; Balsiger, H.; Calmonte, U.; Gasc, S.; Le Roy, L.; Rubin, M.; Tzou, C. Y.; Wurz, P.; Bieler, A.; Berthelier, J.-J.; Fiethe, B.; Hässig, M.; deKeyser, J.; Mall, U.; Rème, H.

2015-10-01

Since nine months the European Space Agency's spacecraft Rosetta, with the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) onboard, is in the comet escort phase. ROSINA is a suite of three instruments, consisting of the COmetary Pressure Sensor (COPS), the Double Focusing Mass Spectrometer (DFMS), and the Reflectron-type Time-Of-Flight (RTOF) mass spectrometer [1]. The two mass spectrometers measure in situ the neutral and ionized volatile material in the coma of comet 67P/Churyumov- Gerasimenko (67P/C-G). With COPS we are able to derive the total gas density, bulk velocities and temperatures of the coma.

Comets - Chemistry and chemical evolution

NASA Technical Reports Server (NTRS)

Donn, B.

1982-01-01

Research on the chemical composition and conditions in comets and their possible role in the origin of life on earth is surveyed. The inorganic and organic compounds and ions indicated in the ultraviolet and visible spectra of comets are noted, and evidence for the existence of at least a small proportion of complex organic molecules in comets is presented. It is then pointed out that while cometary material could have reached the earth and provided volatile elements from which biochemical compounds could have formed, it is unlikely that a cometary nucleus could have withstood the temperatures and pressures necessary to sustain an environment in which life could have originated.

Solar wind composition

NASA Technical Reports Server (NTRS)

Ogilvie, K. W.; Coplan, M. A.

1995-01-01

Advances in instrumentation have resulted in the determination of the average abundances of He, C, N, O, Ne, Mg, Si, S, and Fe in the solar wind to approximately 10%. Comparisons with solar energetic particle (SEP) abundances and galactic cosmic ray abundances have revealed many similarities, especially when compared with solar photospheric abundances. It is now well established that fractionation in the corona results in an overabundance (with respect to the photosphere) of elements with first ionization potentials less than 10 eV. These observations have in turn led to the development of fractionation models that are reasonably successful in reproducing the first ionization (FIP) effect. Under some circumstances it has been possible to relate solar wind observations to particular source regions in the corona. The magnetic topologies of the source regions appear to have a strong influence on the fractionation of elements. Comparisons with spectroscopic data are particularly useful in classifying the different topologies. Ions produced from interstellar neutral atoms are also found in the solar wind. These ions are picked up by the solar wind after ionization by solar radiation or charge exchange and can be identified by their velocity in the solar wind. The pick-up ions provide most of the pressure in the interplanetary medium at large distances. Interstellar abundances can be derived from the observed fluxes of solar wind pick-up ions.

Extremely Low-Frequency Waves Inside the Diamagnetic Cavity of Comet 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Madsen, B.; Wedlund, C. Simon; Eriksson, A.; Goetz, C.; Karlsson, T.; Gunell, H.; Spicher, A.; Henri, P.; Vallières, X.; Miloch, W. J.

2018-05-01

The European Space Agency/Rosetta mission to comet 67P/Churyumov-Gerasimenko has provided several hundred observations of the cometary diamagnetic cavity induced by the interaction between outgassed cometary particles, cometary ions, and the solar wind magnetic field. Here we present the first electric field measurements of four preperihelion and postperihelion cavity crossings on 28 May 2015 and 17 February 2016, using the dual-probe electric field mode of the Langmuir probe (LAP) instrument of the Rosetta Plasma Consortium. We find that on large scales, variations in the electric field fluctuations capture the cavity and boundary regions observed in the already well-studied magnetic field, suggesting the electric field mode of the LAP instrument as a reliable tool to image cavity crossings. In addition, the LAP electric field mode unravels for the first time extremely low-frequency waves within two cavities. These low-frequency electrostatic waves are likely triggered by lower-hybrid waves observed in the surrounding magnetized plasma.

MAVEN SupraThermal and Thermal Ion Compostion (STATIC) Instrument

NASA Astrophysics Data System (ADS)

McFadden, J. P.; Kortmann, O.; Curtis, D.; Dalton, G.; Johnson, G.; Abiad, R.; Sterling, R.; Hatch, K.; Berg, P.; Tiu, C.; Gordon, D.; Heavner, S.; Robinson, M.; Marckwordt, M.; Lin, R.; Jakosky, B.

2015-12-01

The MAVEN SupraThermal And Thermal Ion Compostion (STATIC) instrument is designed to measure the ion composition and distribution function of the cold Martian ionosphere, the heated suprathermal tail of this plasma in the upper ionosphere, and the pickup ions accelerated by solar wind electric fields. STATIC operates over an energy range of 0.1 eV up to 30 keV, with a base time resolution of 4 seconds. The instrument consists of a toroidal "top hat" electrostatic analyzer with a 360° × 90° field-of-view, combined with a time-of-flight (TOF) velocity analyzer with 22.5° resolution in the detection plane. The TOF combines a -15 kV acceleration voltage with ultra-thin carbon foils to resolve H+, He^{++}, He+, O+, O2+, and CO2+ ions. Secondary electrons from carbon foils are detected by microchannel plate detectors and binned into a variety of data products with varying energy, mass, angle, and time resolution. To prevent detector saturation when measuring cold ram ions at periapsis (˜10^{1 1} eV/cm2 s sr eV), while maintaining adequate sensitivity to resolve tenuous pickup ions at apoapsis (˜103 eV/cm2 s sr eV), the sensor includes both mechanical and electrostatic attenuators that increase the dynamic range by a factor of 103. This paper describes the instrument hardware, including several innovative improvements over previous TOF sensors, the ground calibrations of the sensor, the data products generated by the experiment, and some early measurements during cruise phase to Mars.

Instabilities and Turbulence Generation by Pick-Up Ion Distributions in the Outer Heliosheath

NASA Astrophysics Data System (ADS)

Weichman, K.; Roytershteyn, V.; Delzanno, G. L.; Pogorelov, N.

2017-12-01

Pick-up ions (PUIs) play a significant role in the dynamics of the heliosphere. One problem that has attracted significant attention is the stability of ring-like distributions of PUIs and the electromagnetic fluctuations that could be generated by PUI distributions. For example, PUI stability is relevant to theories attempting to identify the origins of the IBEX ribbon. PUIs have previously been investigated by linear stability analysis of model (e.g. Gaussian) rings and corresponding computer simulations. The majority of these simulations utilized particle-in-cell methods which suffer from accuracy limitations imposed by the statistical noise associated with representing the plasma by a relatively small number of computational particles. In this work, we utilize highly accurate spectral Vlasov simulations conducted using the fully kinetic implicit code SPS (Spectral Plasma Solver) to investigate the PUI distributions inferred from a global heliospheric model (Heerikhuisen et al., 2016). Results are compared with those obtained by hybrid and fully kinetic particle-in-cell methods.

On the stability of pick-up ion ring distributions in the outer heliosheath

DOE Office of Scientific and Technical Information (OSTI.GOV)

Summerlin, Errol J.; Viñas, Adolfo F.; Moore, Thomas E.

The 'secondary energetic neutral atom (ENA)' hypothesis for the ribbon feature observed by the Interstellar Boundary Explorer (IBEX) posits that the neutral component of the solar wind continues beyond the heliopause and charge exchanges with interstellar ions in the Outer Heliosheath (OHS). This creates pick-up ions that gyrate about the draped interstellar magnetic field (ISMF) lines at pitch angles near 90° on the locus where the ISMF lies tangential to the heliopause and perpendicular to the heliocentric radial direction. This location closely coincides with the location of the ribbon feature according to the prevailing inferences of the ISMF orientation andmore » draping. The locally gyrating ions undergo additional charge exchange and escape as free-flying neutral atoms, many of which travel back toward the inner solar system and are imaged by IBEX as a ribbon tracing out the locus described above. For this mechanism to succeed, the pick-up ions must diffuse in pitch angle slowly enough to permit secondary charge exchange before their pitch angle distribution substantially broadens away from 90°. Previous work using linear Vlasov dispersion analysis of parallel propagating waves has suggested that the ring distribution in the OHS is highly unstable, which, if true, would make the secondary ENA hypothesis incapable of rendering the observed ribbon. In this paper, we extend this earlier work to more realistic ring distribution functions. We find that, at the low densities necessary to produce the observed IBEX ribbon via the secondary ENA hypothesis, growth rates are highly sensitive to the temperature of the beam and that even very modest temperatures of the ring beam corresponding to beam widths of <1° are sufficient to damp the self-generated waves associated with the ring beam. Thus, at least from the perspective of linear Vlasov dispersion analysis of parallel propagating waves, there is no reason to expect that the ring distributions necessary to produce the observed IBEX ENA flux via the secondary ENA hypothesis will be unstable to their own self-generated turbulence.« less

On the Stability of Pick-up Ion Ring Distributions in the Outer Heliosheath

NASA Astrophysics Data System (ADS)

Summerlin, Errol J.; Viñas, Adolfo F.; Moore, Thomas E.; Christian, Eric R.; Cooper, John F.

2014-10-01

The "secondary energetic neutral atom (ENA)" hypothesis for the ribbon feature observed by the Interstellar Boundary Explorer (IBEX) posits that the neutral component of the solar wind continues beyond the heliopause and charge exchanges with interstellar ions in the Outer Heliosheath (OHS). This creates pick-up ions that gyrate about the draped interstellar magnetic field (ISMF) lines at pitch angles near 90° on the locus where the ISMF lies tangential to the heliopause and perpendicular to the heliocentric radial direction. This location closely coincides with the location of the ribbon feature according to the prevailing inferences of the ISMF orientation and draping. The locally gyrating ions undergo additional charge exchange and escape as free-flying neutral atoms, many of which travel back toward the inner solar system and are imaged by IBEX as a ribbon tracing out the locus described above. For this mechanism to succeed, the pick-up ions must diffuse in pitch angle slowly enough to permit secondary charge exchange before their pitch angle distribution substantially broadens away from 90°. Previous work using linear Vlasov dispersion analysis of parallel propagating waves has suggested that the ring distribution in the OHS is highly unstable, which, if true, would make the secondary ENA hypothesis incapable of rendering the observed ribbon. In this paper, we extend this earlier work to more realistic ring distribution functions. We find that, at the low densities necessary to produce the observed IBEX ribbon via the secondary ENA hypothesis, growth rates are highly sensitive to the temperature of the beam and that even very modest temperatures of the ring beam corresponding to beam widths of <1° are sufficient to damp the self-generated waves associated with the ring beam. Thus, at least from the perspective of linear Vlasov dispersion analysis of parallel propagating waves, there is no reason to expect that the ring distributions necessary to produce the observed IBEX ENA flux via the secondary ENA hypothesis will be unstable to their own self-generated turbulence.

Low-frequency electromagnetic plasma waves at comet P/Grigg-Skjellerup: Overview and spectral characteristics

NASA Technical Reports Server (NTRS)

Glassmeier, Karl-Heinz; Neubauer, Fritz M.

1993-01-01

Large-amplitude electromagnetic plasma waves are one of the dominant features of the solar wind-comet interaction. Wave characteristics strongly depend on parameters such as the solar wind flow and Alfven velocities and the angle between flow and interplanetary magnetic field as well as the production rate. With respect to the latter the flyby of the spacecraft Giotto at comet P/Griff-Skjellerup provides a unique possibility to study such waves in further detail. Pickup ion-related wave signatures have been observed up to a distance of 600,000 km from the nucleus. Peak spectral power in the spacecraft frame of reference occurs at frequencies mainly somewhat below the water group ion gyrofrequency. From this the waves are determined to be mainly left-hand polarized waves, causing one-sided pitch angle diffusion outbound. The wave activity strongly increases close to the comet; upstream it exhibits a quadratic dependence on the water group pickup ion free energy. Furthermore, a phenomenological study of the wave characteristics provides a unique description of the fine-structure of the interaction region. Indications of steepened magnetosonic waves have been found in the outbound magnetosheath region.

On the energy crisis in the Io plasma torus

NASA Technical Reports Server (NTRS)

Smith, Robert A.; Bagenal, Fran; Cheng, Andrew F.; Strobel, Darrell

1988-01-01

Recent calculations of the energy balance of the Io plasma torus show that the observed UV and EUV radiation cannot be maintained solely via energy input by the ion pickup mechanism. Current theoretical models of the torus must be modified to include non-local energy input. It is argued that the required energy may be supplied by inward diffusion of energetic heavy ions with energies less than about 20 keV.

Review: Observations of recent comets, ion tails

NASA Technical Reports Server (NTRS)

Brandt, J. C.

1976-01-01

Photographic plates of the moving structures in the cometary tail are examined. Several divergent explanations for the case of comet Kohoutek are presented. It is suggested that these hypotheses be tested by observing the motion of the material spectroscopically by means of the Doppler effect.

Double-modulation spectroscopy of molecular ions - Eliminating the background in velocity-modulation spectroscopy

NASA Technical Reports Server (NTRS)

Lan, Guang; Tholl, Hans Dieter; Farley, John W.

1991-01-01

Velocity-modulation spectroscopy is an established technique for performing laser absorption spectroscopy of molecular ions in a discharge. However, such experiments are often plagued by a coherent background signal arising from emission from the discharge or from electronic pickup. Fluctuations in the background can obscure the desired signal. A simple technique using amplitude modulation of the laser and two lock-in amplifiers in series to detect the signal is demonstrated. The background and background fluctuations are thereby eliminated, facilitating the detection of molecular ions.

Dynamic molecular oxygen production in cometary comae.

PubMed

Yao, Yunxi; Giapis, Konstantinos P

2017-05-08

Abundant molecular oxygen was discovered in the coma of comet 67P/Churyumov-Gerasimenko. Its origin was ascribed to primordial gaseous O 2 incorporated into the nucleus during the comet's formation. This thesis was put forward after discounting several O 2 production mechanisms in comets, including photolysis and radiolysis of water, solar wind-surface interactions and gas-phase collisions. Here we report an original Eley-Rideal reaction mechanism, which permits direct O 2 formation in single collisions of energetic water ions with oxidized cometary surface analogues. The reaction proceeds by H 2 O + abstracting a surface O-atom, then forming an excited precursor state, which dissociates to produce O 2 - . Subsequent photo-detachment leads to molecular O 2 , whose presence in the coma may thus be linked directly to water molecules and their interaction with the solar wind. This abiotic O 2 production mechanism is consistent with reported trends in the 67P coma and raises awareness of the role of energetic negative ions in comets.

Dynamic molecular oxygen production in cometary comae

NASA Astrophysics Data System (ADS)

Yao, Yunxi; Giapis, Konstantinos P.

2017-05-01

Abundant molecular oxygen was discovered in the coma of comet 67P/Churyumov-Gerasimenko. Its origin was ascribed to primordial gaseous O2 incorporated into the nucleus during the comet's formation. This thesis was put forward after discounting several O2 production mechanisms in comets, including photolysis and radiolysis of water, solar wind-surface interactions and gas-phase collisions. Here we report an original Eley-Rideal reaction mechanism, which permits direct O2 formation in single collisions of energetic water ions with oxidized cometary surface analogues. The reaction proceeds by H2O+ abstracting a surface O-atom, then forming an excited precursor state, which dissociates to produce O2-. Subsequent photo-detachment leads to molecular O2, whose presence in the coma may thus be linked directly to water molecules and their interaction with the solar wind. This abiotic O2 production mechanism is consistent with reported trends in the 67P coma and raises awareness of the role of energetic negative ions in comets.

Electron distributions upstream of the Comet Halley bow shock - Evidence for adiabatic heating

NASA Technical Reports Server (NTRS)

Larson, D. E.; Anderson, K. A.; Lin, R. P.; Carlson, C. W.; Reme, H.; Glassmeier, K. H.; Neubauer, F. M.

1992-01-01

Three-dimensional plasma electron (22 eV to 30 keV) observations upstream of Comet Halley bow shock, obtained by the RPA-1 COPERNIC (Reme Plasma Analyzer - Complete Positive Ion, Electron and Ram Negative Ion Measurements near Comet Halley) experiment on the Giotto spacecraft are reported. Besides electron distributions typical of the undisturbed solar wind and backstreaming electrons observed when the magnetic field line intersects the cometary bow shock, a new type of distribution, characterized by enhanced low energy (less than 100 eV) flux which peaks at 90-deg pitch angles is found. These are most prominent when the spacecraft is on field lines which pass close to but are not connected to the bow shock. The 90-deg pitch angle electrons appear to have been adiabatically heated by the increase in the magnetic field strength resulting from the compression of the upstream solar wind plasma by the cometary mass loading. A model calculation of this effect which agrees qualitatively with the observed 90-deg flux enhancements is presented.

Discovery of Suprathermal Ionospheric Origin Fe+ in and Near Earth's Magnetosphere

NASA Astrophysics Data System (ADS)

Christon, S. P.; Hamilton, D. C.; Plane, J. M. C.; Mitchell, D. G.; Grebowsky, J. M.; Spjeldvik, W. N.; Nylund, S. R.

2017-11-01

Suprathermal (87-212 keV/e) singly charged iron, Fe+, has been discovered in and near Earth's 9-30 RE equatorial magnetosphere using 21 years of Geotail STICS (suprathermal ion composition spectrometer) data. Its detection is enhanced during higher geomagnetic and solar activity levels. Fe+, rare compared to dominant suprathermal solar wind and ionospheric origin heavy ions, might derive from one or all three candidate lower-energy sources: (a) ionospheric outflow of Fe+ escaped from ion layers near 100 km altitude, (b) charge exchange of nominal solar wind iron, Fe+≥7, in Earth's exosphere, or (c) inner source pickup Fe+ carried by the solar wind, likely formed by solar wind Fe interaction with near-Sun interplanetary dust particles. Earth's semipermanent ionospheric Fe+ layers derive from tons of interplanetary dust particles entering Earth's atmosphere daily, and Fe+ scattered from these layers is observed up to 1000 km altitude, likely escaping in strong ionospheric outflows. Using 26% of STICS's magnetosphere-dominated data when possible Fe+2 ions are not masked by other ions, we demonstrate that solar wind Fe charge exchange secondaries are not an obvious Fe+ source. Contemporaneous Earth flyby and cruise data from charge-energy-mass spectrometer on the Cassini spacecraft, a functionally identical instrument, show that inner source pickup Fe+ is likely not important at suprathermal energies. Consequently, we suggest that ionospheric Fe+ constitutes at least a significant portion of Earth's suprathermal Fe+, comparable to the situation at Saturn where suprathermal Fe+ is also likely of ionospheric origin.

Inner Source and Interstellar Pickup Ions observed by MMS-HPCA

NASA Astrophysics Data System (ADS)

Gomez, Roman; Fuselier, Stephen; Burch, James L.; Mukherjee, Joey; Valek, Phillip W.; Allegrini, Frederic; Desai, Mihir I.

2017-04-01

Pickup Ions in the solar system are either of interstellar origin, or come from an inner source whose existence is confirmed, but which has not been directly observed. The Hot Plasma Composition Analyzer of the Magnetospheric Multiscale mission (MMS-HPCA) measures the energy and directional flux of ions with M/Q from 1 eV/e to 40 keV/e and is used measure the composition and dynamics of reconnection plasmas near the earth. During the first phase of the mission, from 1 September 2015 to 8 March 2016, the spacecraft at 12 Earth Radii apogee swept through the dayside from 1800 to 0600 local time. Although the apogee was designed to maximize encounters with the magnetopause, there were many instances when the spacecraft crossed the bow shock and sampled the solar wind. In November and December, while the spacecraft were downstream of the interstellar neutral focusing cone, HPCA detected pick up ions, such as He+, O+, and Ne+. He+ was distributed in an energy range of 14 eV - 20.6 keV, peaking at 757 eV; presumably of interstellar origin. O+ was observed in the energy range of 390 eV - 10.6 keV, and also seems to come from the interstellar medium. Ne+ was observed to be tightly distributed around a center energy of 5.5 keV, which implies an inner source origin. The mass - energy - angle analysis of these pick up ion distributions is presented, and their interpretation in terms of interstellar and inner source ions is discussed.

Isotopes and Minor Volatiles in the Coma of Comet 67P/Churyumov-Gerasimenko Observed by the Rosetta/ROSINA Instrument: Planetary Implications

NASA Astrophysics Data System (ADS)

Marty, B.; Altwegg, K.; Balsiger, H. R.; Calmonte, U.; Hässig, M.; Le Roy, L.; Rubin, M.; Bieler, A. M.; Fuselier, S. A.; De Keyser, J. M.; Mousis, O.

2015-12-01

The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) instrument suite is part of the payload of the European Space Agency's Rosetta spacecraft. Part of this suite, the Double Focusing Mass Spectrometer (DFMS) has been analyzing major (e.g., H2O,) as well as minor (CO, CO2, N2, NHx, noble gases) species and elements and some of their isotopes thanks to its high mass resolution of 3,000 at 1% peak height and its high sensitivity. In parallel to the presentation by Rubin et al. (this meeting) who discuss temporal variation of the coma composition as a function of heliospheric distance, we present here the on-going measurements done on the above species and isotopes. Besides temporal variability, one of the goals of ROSINA is to document the composition of cometary volatiles in the context of the formation of planets and of the origin of atmospheres. The first detection of a noble gas, Ar, in a cometary coma (Balsiger et al, in press), together with the measured D/H isotope ratio and carbon species, constrains the origin of the inner planet atmospheres and the terrestrial oceans. Assuming that 67P is representative of the cometary reservoir, major volatiles (H, C, N) of the inner planets are unlikely to have originated from comets, but a cometary origin for atmospheric noble gases is a viable hypothesis. However, these cometary measurements were done during a short interval of time (in autumn 2014) when the comet was at 3.5 AU from the Sun, which raises the question of how well they represent the bulk cometary composition. Further measurements of the bulk composition are planned close to the perihelion. Also of interest is the isotope composition of nitrogen in N-bearing compounds. Spectroscopic measurements of cometary HCN and NH2+ done so far indicate a two-fold enrichment in 15N, that needs to be confirmed by in-situ mass spectrometry. Measurements of other noble gases, in particular Xe (a very difficult measurement), may set stringent constraints on the nature (clathrate vs. amorphous) of cometary ice. Results from these measurements before and after the perihelion will be presented.

Cometary Coma Chemical Composition (C4) Mission

NASA Technical Reports Server (NTRS)

Carle, Glenn C.; Clark, Benton C.; Knocke, Philip C.; OHara, Bonnie J.; Adams, Larry; Niemann, Hasso B.; Alexander, Merle; Veverka, Joseph; Goldstein, Raymond; Huebner, Walter;

Ion Composition of Comet 19P/Borrelly as Measured by the PEPE Ion Mass Spectrometer on DS1

NASA Astrophysics Data System (ADS)

Nordholt, J. E.; Reisenfeld, D. B.; Wiens, R. C.; Gary, P.

2002-12-01

Cometary compositions are of great interest because they hold important clues to the formation of the outer solar system, and to the sources of volatiles in the solar system, including the terrestrial planets. In order to understand the primordial compositions of cometary nuclei, it is important to also understand their evolution, as many of the comets most accessible to spacecraft are highly evolved. It is also important to understand the ion and neutral chemistry that occurs in the coma surrounding the nucleus if the coma ion composition is to be used to determine the original composition of the nucleus. Deep Space One (DS1) was only the second spacecraft, after Giotto, to use an ion mass-resolving instrument to explore cometary coma compositions in-situ, which it did during the flyby of Comet Borrelly on September 22, 2001. Borrelly is significantly more evolved than Halley. In addition, the encounter occurred at a significantly greater distance from the sun (1.36 AU vs 0.9 AU for Giotto at Halley). The Plasma Experiment for Planetary Exploration (PEPE) on board DS1 was capable of resolving electron and ion energy, angle of incidence, and ion mass composition. The PEPE ion data from the seven minutes surrounding closest approach (2171 km) have been extensively analyzed. The instrument response was modeled using SIMION and TRIM codes for all of the major species through 20 AMU plus CO (at its operating voltage PEPE was very insensitive to heavier molecules). Chi-squared minimization analysis is being carried out to determine the best fit and the uncertainties. Preliminary results for the predominant heavy ions are OH+ at (72 +/- 9)% of the total water-group ion density, H2O+ at (25 +/- 7)%, CH3+ at (5 +/- 3)%, and O+ at (4 +/- 5)%. Uncertainties are quoted at the 90% confidence level. Comparison with reported Halley compositions from Giotto shows that Borrelly clearly has a lower H3O+ abundance (< 9%), consistent with a more evolved comet. The presence of relatively high amounts of CH3+, proposed in the context of Halley to be produced by protonation of CH2+, is somewhat surprising in this context. Because the H3O+/H2O+ ratio is an indicator of the degree of protonation in the coma, a low H3O+/H2O+ ratio would predict a low CH3+/CH2+ ratio as well. However, this is not the case at Borrelly. The CH3+/H3O+ ratio will need further study in future comet models and observations.

Plasma IMS Composition Measurements for Europa, Ganymede, and the Jovian System

NASA Technical Reports Server (NTRS)

Sittler, E. C., Jr.; Cooper, J. F.; Hartle, R. E.; Paterson, W. R.; Christian, E. R.; Lipatov, A. S.; Mahaffy, P R.; Paschalidis, N.; Sarantos, M.; Coplan, M. A.;

Plasma IMS Composition Measurements for Europa, Ganymede, and the Jovian Systems

NASA Technical Reports Server (NTRS)

Sittler, E.; Cooper, J.; Hartle, R.; Paterson ,W.; Christian, E.; Mahaffy, P.; Paschalidis, N.; Lipatov, A.; Sarantos, M.; Coplan, M.;

Website for the Astrochemistry Laboratory, Astrophysics Branch, Space Sciences Division

NASA Technical Reports Server (NTRS)

Sandford, Scott; DeVincenzi, D. (Technical Monitor)

2002-01-01

The Astrochemistry Laboratory in the Astrophysics Branch (SSA) of the Space Sciences Division at NASA's Ames Research Center specializes in the study of extraterrestrial materials and their analogs. The staff has pioneered laboratory studies of space environments including interstellar, cometary, and planetary ices, simulations of the so-called 'Unidentified' Infrared Emission Bands and Diffuse Interstellar Bands using PAHs (Polycyclic Aromatic Hydrocarbons) and PAH-related materials, and has extensive experience with low-temperature spectroscopy and astronomical observation. Important discoveries made by the Astrochemistry Group include: (1) The recognition that polycyclic aromatic hydrocarbons and their ions are common in space; (2) The identification of a major fraction of the known molecular species frozen in interstellar/pre-cometary ices; (3) The recognition that a significant fraction of the carbon in the interstellar medium is carried by both microdiamonds and organic materials; (4) The expansion of the types of molecules expected to be synthesized in interstellar/pre-cometary ices. These could be delivered to the early Earth (or other body) and influence the origin or early evolution of life.

Charge exchange in cometary coma: Discovery of H- ions in the solar wind close to comet 67P/Churyumov-Gerasimenko.

PubMed

Burch, J L; Cravens, T E; Llera, K; Goldstein, R; Mokashi, P; Tzou, C-Y; Broiles, T

2015-07-16

As Rosetta was orbiting comet 67P/Churyumov-Gerasimenko, the Ion and Electron Sensor detected negative particles with angular distributions like those of the concurrently measured solar wind protons but with fluxes of only about 10% of the proton fluxes and energies of about 90% of the proton energies. Using well-known cross sections and energy-loss data, it is determined that the fluxes and energies of the negative particles are consistent with the production of H - ions in the solar wind by double charge exchange with molecules in the coma.

Structure of Ion Outflow in the Martian Magnetotail

NASA Astrophysics Data System (ADS)

McFadden, J. P.; Mitchell, D.; Luhmann, J. G.; Connerney, J. E. P.; Jakosky, B. M.

2017-12-01

The Suprathermal And Thermal Ion Composition (STATIC) sensor on the MAVEN spacecraft provides a detailed look at the structure of ion outflow in the Martian magnetotail including ion composition, energization, and flow. Mars' magnetotail contains a mixture of cold (<10 eV) nearly-stationary multi-species ions, tailward-moving cold multi-species ions, suprathermal ions of a few tens of eV, warm (about 100 eV) proton populations, and heavy (primarily O+) pickup ions at energies from 1 to 10 keV which may display several simultaneous peaks in energy flux. The cold tailward-moving ions represent a significant fraction of the Martian ion loss, perhaps comparable to loses from molecular oxygen dissociation. The suprathermal tail that accompanies the cold ions varies greatly and provides clues to ion escape. The warm protons, on first examination, appear to be of sheath origin, displaying a similar energy distribution and accompanied by a tenuous warm population at M/Q=2 (which could be either solar wind alphas or molecular hydrogen ions of ionospheric origin). STATIC produces a weak ghost peak at M/Q=11-12 when observing molecular hydrogen ions, but not alphas, often allowing the instrument to distinguish the source of protons. Measurements show the warm protons are of ionospheric origin in the central tail and transition to sheath plasma in the umbra. Energetic (1-10 keV) pickup oxygen in the magnetotail is produced on the nightside, near the pole where the IMF convection electric field points toward the planet, the same hemisphere where sputtering occurs. When two spectral peaks are observed, these tailward-moving ions differ in direction by relatively small angles (about 20 degrees). These peaks can persist for tens of minutes indicating approximately time-stationary acceleration, and therefore acceleration in potential fields. Magnetotail structure and geometry can be inferred not only from the local magnetic field, but also from the measured electron distributions which indicate source populations and connectivity (closed, open, or interplanetary). This paper will be used to describe the observed tail structure and the inferred acceleration structure.

Pickup Ion Signatures in the Vicinity of Titan

NASA Astrophysics Data System (ADS)

Regoli, L.; Coates, A. J.; Feyerabend, M.; Roussos, E.; Jones, G. H.; Krupp, N.; Thomsen, M. F.

2015-12-01

Being the only moon in the solar system with a significant atmosphere, Titan possesses an ionosphere that acts as a conducting obstacle to the incoming plasma from Saturn's magnetosphere. This creates a mass-loading of the magnetic field lines with freshly picked up ions from Titan's atmosphere on a process similar to that observed in comets (e.g. Coates et al. (1993), Journal of Geophysical Research, Vol. 98, No. A12, 20985-20994) and other moons like Jupiter's Io (e.g. Russell et al. (2003), Planetary and Space Science, Vol. 51, 233-238). However, while at other celestial bodies ion cyclotron waves arise as one of the main signatures of this process, this is not the case at Titan, with e.g. Cowee et al. (2010) (Journal of Geophysical Research, Vol. 115, A10224) attributing this to the local orientation of the magnetic field and the plasma flow preventing the waves to grow to levels detectable by the instruments on-board Cassini. For the reason above, the detection of pickup ions signatures needs to be approached through other methods. For this study, we analyze data from the CAPS/IMS instrument on-board Cassini. IMS is an ion mass spectrometer capable of detecting ion fluxes with energies from 1 eV to 50 keV with an atomic resolution of M/ΔM ~ 70. During many of the dedicated Titan flybys by Cassini, IMS was able to distinguish between ions of magnetospheric origin and of ionospheric origin, the latter being freshly picked up ions from Titan's ionosphere. With the help of ion spectrograms and time of flight (TOF) information, we carried out a survey of all the flybys for which IMS has data (the CAPS instrument was switched off after the 83th. dedicated flyby, named in the project as T83) in order to obtain information about the location and frequency of occurence for the signatures.

Termination Shock Transition in Multi-ion Multi-fluid MHD Models of the Heliosphere

NASA Astrophysics Data System (ADS)

Zieger, B.; Opher, M.; Toth, G.

2013-12-01

As evidenced by Voyager 2 observations, pickup ions (PUIs) play a significant role in the termination shock (TS) transition of the solar wind [Richardson et al., Nature, 2008]. Recent kinetic simulations [Ariad and Gedalin, JGR, 2013] came to the conclusion that the contribution of the high energy tail of PUIs is negligible at the shock transition. The Rankine-Hugoniot (R-H) relations are determined by the low energy body of PUIs. Particle-in-cell simulations by Wu et al. [JGR, 2010] have shown that the sum of the thermal solar wind and non-thermal PUI distributions downstream of the TS can be approximated with a 2-Maxwellian distribution. It is important to note that this 2-Maxwellian distribution neglects the suprathermal tail population that has a characteristic power-law distribution. These results justify the fluid description of PUIs in our large-scale multi-ion multi-fluid MHD simulations of the heliospheric interface [Prested et al., JGR, 2013; Zieger et al., GRL, 2013]. The closure of the multi-ion MHD equations could be implemented with separate momentum and energy equations for the different ion species (thermal solar wind and PUIs) where the transfer rate of momentum and energy between the two ion species are considered as source terms, like in Glocer et al. [JGR, 2009]. Another option is to solve for the total energy equation with an additional equation for the PUI pressure, as suggested by Fahr and Chalov [A&A, 2008]. In this paper, we validate the energy conservation and the R-H relations across the TS in different numerical implementations of our latest multi-ion multi-fluid MHD model. We assume an instantaneous pickup process, where the convection velocity of the two ion fluids are the same, and the so-called strong scattering approximation, where newly born PUIs attain their spherical shell distribution within a short distance on fluid scales (spatial scales much larger than the respective ion gyroradius).

A Spectroscopic Tour of the Solar System with FUSE

NASA Astrophysics Data System (ADS)

Feldman, P. D.

2006-06-01

The spectral band, resolution, and sensitivity of FUSE provide a unique capability to study the principal atoms, ions and molecules in a variety of planetary environments. Moving target capability was implemented in mid-2000 and has enabled significant discoveries on the nature of the atmospheres of Mars, Jupiter, Saturn, and four comets, particularly the detection for the first time of H2 in the atmosphere of Mars and in cometary comae. FUSE showed that comets have a very rich spectrum in the far-ultraviolet although nearly half of the observed lines remain unidentified. Sensitive searches for Ar, N2, and O VI have only yielded upper limits to the abundances of these species in cometary comae. Observations of Jovian aurora, which is dominated by electron excited H2 emission, and of the Io plasma torus were made during a mini-campaign at the time of the Cassini closest approach to Jupiter in December 2000. Singly and doubly-ionized chlorine were detected in the torus spectrum and their abundances were quantitatively determined relative to the sulfur ion abundance.

Physical Roles of Interstellar-origin Pickup Ions at Heliospheric Termination Shock. II. Impact of the Front Nonstationary on the Energy Partition and Particle Velocity Distribution

NASA Astrophysics Data System (ADS)

Lembège, Bertrand; Yang, Zhongwei

2018-06-01

The impact of the nonstationarity of the heliospheric termination shock in the presence of pickup ions (PUIs) on the energy partition between different plasma components is analyzed self-consistently by using a one-dimensional particle-in-cell simulation code. Solar wind ions (SWIs) and PUIs are introduced as Maxwellian and shell distributions, respectively. For a fixed time, (a) with a percentage of 25% PUIs, a large part of the downstream thermal pressure is carried by reflected PUIs, in agreement with previous hybrid simulations; (b) the total downstream distribution includes three main components: (i) a low-energy component dominated by directly transmitted (DT) SWIs, (ii) a high-energy component dominated by reflected PUIs, and (iii) an intermediate-energy component dominated by reflected SWIs and DT PUIs. Moreover, results show that the front nonstationarity (self-reformation) persists even in presence of 25% PUIs, and has some impacts on both SWIs and PUIs: (a) the rate of reflected ions suffers some time fluctuations for both SWIs and PUIs; (b) the relative percentage of downstream thermal pressure transfered to PUIs and SWIs also suffers some time fluctuations, but depends on the relative distance from the front; (c) the three components within the total downstream heliosheath distribution persist in time, but the contribution of the ion subpopulations to the low- and intermediate-energy components are redistributed by the front nonstationarity. Our results allow clarifying the respective roles of SWIs and PUIs as a viable production source of energetic neutral atoms and are compared with previous results.

The Plasma and Suprathermal Ion Composition (PLASTIC) Investigation on the STEREO Observatories

NASA Astrophysics Data System (ADS)

Galvin, A. B.; Kistler, L. M.; Popecki, M. A.; Farrugia, C. J.; Simunac, K. D. C.; Ellis, L.; Möbius, E.; Lee, M. A.; Boehm, M.; Carroll, J.; Crawshaw, A.; Conti, M.; Demaine, P.; Ellis, S.; Gaidos, J. A.; Googins, J.; Granoff, M.; Gustafson, A.; Heirtzler, D.; King, B.; Knauss, U.; Levasseur, J.; Longworth, S.; Singer, K.; Turco, S.; Vachon, P.; Vosbury, M.; Widholm, M.; Blush, L. M.; Karrer, R.; Bochsler, P.; Daoudi, H.; Etter, A.; Fischer, J.; Jost, J.; Opitz, A.; Sigrist, M.; Wurz, P.; Klecker, B.; Ertl, M.; Seidenschwang, E.; Wimmer-Schweingruber, R. F.; Koeten, M.; Thompson, B.; Steinfeld, D.

2008-04-01

The Plasma and Suprathermal Ion Composition (PLASTIC) investigation provides the in situ solar wind and low energy heliospheric ion measurements for the NASA Solar Terrestrial Relations Observatory Mission, which consists of two spacecraft (STEREO-A, STEREO-B). PLASTIC-A and PLASTIC-B are identical. Each PLASTIC is a time-of-flight/energy mass spectrometer designed to determine the elemental composition, ionic charge states, and bulk flow parameters of major solar wind ions in the mass range from hydrogen to iron. PLASTIC has nearly complete angular coverage in the ecliptic plane and an energy range from ˜0.3 to 80 keV/e, from which the distribution functions of suprathermal ions, including those ions created in pick-up and local shock acceleration processes, are also provided.

Propagation of Interplanetary Disturbances in the Outer Heliosphere

NASA Technical Reports Server (NTRS)

Wang, Chi

2005-01-01

Contents include the following: 1. We have developed a one-dimensional, spherically symmetric, multi-fluid MHD model that includes solar wind protons and electrons, pickup ions, and interstellar neutral hydrogen. This model advances the existing solar wind models for the outer heliosphere in two important ways: one is that it distinguishes solar wind protons from pickup ions, and the other is that it allows for energy transfer from pickup ions to the solar wind protons. Model results compare favorably with the Voyager 2 observations. 2. 2. Solar wind slowdown and interstellar neutral density. The solar wind in the outer heliosphere is fundamentally different from that in the inner heliosphere since the effects of interstellar neutrals become significant. 3. ICME propagation from the inner to outer heliosphere. Large coronal mass ejections (CMEs) have major effects on the structure of the solar wind and the heliosphere. The plasma and magnetic field can be compressed ahead of interplanetary CMEs. 4. During the current solar cycle (Cycle 23), several major CMEs associated with solar flares produced large transient shocks which were observed by widely-separated spacecraft such as Wind at Earth and Voyager 2 beyond 60 AU. Using data from these spacecraft, we use the multi-fluid model to investigate shock propagation and interaction in the heliosphere. Specifically, we studied the Bastille Day 2000, April 2001 and Halloween 2003 events. 5. Statistical properties of the solar wind in the outer heliosphere. In a collaboration with L.F. Burlaga of GSFC, it is shown that the basic statistical properties of the solar wind in the outer heliosphere can be well produced by our model. We studied the large-scale heliospheric magnetic field strength fluctuations as a function of distance from the Sun during the declining phase of a solar cycle, using our numerical model with observations made at 1 AU during 1995 as input. 6. Radial heliospheric magnetic field events. The heliospheric magnetic field (HMF) direction, on average, conforms well to the Parker spiral.

On the decades-long stability of the interstellar wind through the solar system

NASA Astrophysics Data System (ADS)

Lallement, R.; Bertaux, J. L.

2014-05-01

We have revisited the series of observations recently used to infer a temporal variation in the interstellar helium flow over the past forty years. Concerning the recent IBEX-Lo direct detection of helium neutrals, there are two types of precise and unambiguous measurements that do not rely on the exact response of the instrument: the count rate maxima as a function of the spin angle, which determines the ecliptic latitude of the flow, and the count rate maxima as a function of IBEX longitude, which determines a tight relationship between the ecliptic longitude of the flow and its velocity far from the Sun. These measurements provide parameters (and couples of parameters in the second case) that are remarkably similar to the canonical, old values. In contrast, the preferred choice of a lower velocity and higher longitude reported before from IBEX data is only based on the count rate variation (at each spin phase maximum) as a function of the satellite longitude, when drifting across the region of high fluxes. We have examined the consequences of dead-time counting effects and conclude that including them at a realistic level is sufficient to reconcile the data with the old parameters, calling for further investigations. We discuss the analyses of the STEREO pickup ion data and argue that the statistical method that has been preferred to infer the neutral flow longitude (instead of the more direct method based on the pickup ion maximum flux directions) is not appropriate. Moreover, transport effects may have been significant at the very weak solar activity level of 2007-2009, in which case the longitudes of the pickup ion maxima are only upper limits on the flow longitude. Finally, we found that using some flow longitude determinations based on UV glow data is not adequate. Based on this global study, and at variance with recent conclusions, we find no evidence for a temporal variability of the interstellar helium flow. This has implications for inner and outer heliosphere studies.

Charge exchange cross sections in slow collisions of Si3+ with Hydrogen atom

NASA Astrophysics Data System (ADS)

Joseph, Dwayne; Quashie, Edwin; Saha, Bidhan

2011-05-01

In recent years both the experimental and theoretical studies of electron transfer in ion-atom collisions have progressed considerably. Accurate determination of the cross sections and an understanding of the dynamics of the electron-capture process by multiply charged ions from atomic hydrogen over a wide range of projectile velocities are important in various field ranging from fusion plasma to astrophysics. The soft X-ray emission from comets has been explained by charge transfer of solar wind ions, among them Si3+, with neutrals in the cometary gas vapor. The cross sections are evaluated using the (a) full quantum and (b) semi-classical molecular orbital close coupling (MOCC) methods. Adiabatic potentials and wave functions for relavent singlet and triplet states are generated using the MRDCI structure codes. Details will be presented at the conference. In recent years both the experimental and theoretical studies of electron transfer in ion-atom collisions have progressed considerably. Accurate determination of the cross sections and an understanding of the dynamics of the electron-capture process by multiply charged ions from atomic hydrogen over a wide range of projectile velocities are important in various field ranging from fusion plasma to astrophysics. The soft X-ray emission from comets has been explained by charge transfer of solar wind ions, among them Si3+, with neutrals in the cometary gas vapor. The cross sections are evaluated using the (a) full quantum and (b) semi-classical molecular orbital close coupling (MOCC) methods. Adiabatic potentials and wave functions for relavent singlet and triplet states are generated using the MRDCI structure codes. Details will be presented at the conference. Work supported by NSF CREST project (grant #0630370).

Statistical analysis of suprathermal electron drivers at 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Broiles, Thomas W.; Burch, J. L.; Chae, K.; Clark, G.; Cravens, T. E.; Eriksson, A.; Fuselier, S. A.; Frahm, R. A.; Gasc, S.; Goldstein, R.; Henri, P.; Koenders, C.; Livadiotis, G.; Mandt, K. E.; Mokashi, P.; Nemeth, Z.; Odelstad, E.; Rubin, M.; Samara, M.

2016-11-01

We use observations from the Ion and Electron Sensor (IES) on board the Rosetta spacecraft to study the relationship between the cometary suprathermal electrons and the drivers that affect their density and temperature. We fit the IES electron observations with the summation of two kappa distributions, which we characterize as a dense and warm population (˜10 cm-3 and ˜16 eV) and a rarefied and hot population (˜0.01 cm-3 and ˜43 eV). The parameters of our fitting technique determine the populations' density, temperature, and invariant kappa index. We focus our analysis on the warm population to determine its origin by comparing the density and temperature with the neutral density and magnetic field strength. We find that the warm electron population is actually two separate sub-populations: electron distributions with temperatures above 8.6 eV and electron distributions with temperatures below 8.6 eV. The two sub-populations have different relationships between their density and temperature. Moreover, the two sub-populations are affected by different drivers. The hotter sub-population temperature is strongly correlated with neutral density, while the cooler sub-population is unaffected by neutral density and is only weakly correlated with magnetic field strength. We suggest that the population with temperatures above 8.6 eV is being heated by lower hybrid waves driven by counterstreaming solar wind protons and newly formed, cometary ions created in localized, dense neutral streams. To the best of our knowledge, this represents the first observations of cometary electrons heated through wave-particle interactions.

Evolution of the physical properties of dust and cometary dust activity from 67P/Churyumov-Gerasimenko measured in situ by Rosetta/COSIMA

NASA Astrophysics Data System (ADS)

Merouane, Sihane; Stenzel, Oliver; Hilchenbach, Martin; Schulz, Rita; Altobelli, Nicolas; Fischer, Henning; Hornung, Klaus; Kissel, Jochen; Langevin, Yves; Mellado, Eva; Rynö, Jouni; Zaprudin, Boris

2017-07-01

The Cometary Secondary Ion Mass Analyzer (COSIMA) collects dust particles in the coma of 67P/Churyumov-Gerasimenko, images them with a resolution of 14 μm × 14 μm, and measures their composition via time-of-flight secondary ion mass spectrometry. The particles are collected on targets exposed to the cometary flux for periods ranging from several hours to a week. Images are acquired with the internal camera, the COSISCOPE, before and after each exposure period. This paper focuses on the evolution of the dust flux and of the size distribution of the particles derived from the COSISCOPE images during the two years of the mission. The dust flux reaches its maximum at perihelion. We suggest that the delay of 20 d between the activity measured by COSIMA and the gas activity measured by the other instruments on Rosetta is caused by the presence of a volatile-poor dust layer on the nucleus that is removed around perihelion, uncovering volatile-rich layers that then become active. The difference in morphology between the northern and southern hemispheres observed by OSIRIS, the south being more sintered, is also recorded in the COSIMA data by a change in the size distribution during the southern summer, as the large porous aggregates disappear from the COSIMA collection. The properties of the particles collected during an outburst in early September 2016 indicate that these particles were ejected by a violent event and might originate from regions of low tensile strength.

Possible modification of the cooling index of interstellar helium pickup ions by electron impact ionization in the inner heliosphere

NASA Astrophysics Data System (ADS)

Chen, Jun Hong; Bochsler, Peter; Möbius, Eberhard; Gloeckler, George

2014-09-01

Interstellar neutrals penetrating into the inner heliosphere are ionized by photoionization, charge exchange with solar wind ions, and electron impact ionization. These processes comprise the first step in the evolution of interstellar pickup ion (PUI) distributions. Typically, PUI distributions have been described in terms of velocity distribution functions that cool adiabatically under solar wind expansion, with a cooling index of 3/2. Recently, the cooling index has been determined experimentally in observations of He PUI distributions with Advanced Composition Explorer (ACE)/Solar Wind Ion Composition Spectrometer and found to vary substantially over the solar cycle. The experimental determination of the cooling index depends on the knowledge of the ionization rates and their spatial variation. Usually, ionization rates increase with 1/r2 as neutral particles approach the Sun, which is not exactly true for electron impact ionization, because the electron temperature increases with decreasing distance from the Sun due to the complexity of its distributions and different radial gradients in temperature. This different dependence on distance may become important in the study of the evolution of PUI distributions and is suspected as one of the potential reasons for the observed variation of the cooling index. Therefore, we investigate in this paper the impact of electron ionization on the variability of the cooling index. We find that the deviation of the electron ionization rate from the canonical 1/r2 behavior of other ionization processes plays only a minor role.

Volatiles (H, C, N, O, noble gases) in comets as tracers of early solar system events (Invited)

NASA Astrophysics Data System (ADS)

Marty, B.

2013-12-01

Volatiles (H, C, N, O, noble gases) present the largest variations in their relative abundances and, importantly, in their isotopic ratios, among solar system elements. The original composition of the protosolar nebula has been investigated through the measurements of primitive meteorites and of in-situ (e.g. Galileo probe analysis of the Jupiter's atmosphere) and sample-return (Genesis, recovery and analysis of solar wind) missions. The protosolar gas was poor in deuterium, in 15N and in 17,18O. Variations among solar system reservoir reach several hundreds of percents for the D/H and 15N/14N ratios. These variations are possibly : (i) due to interactions between XUV photons of the proto-Sun and the-dust, (ii) result from low temperature ion-molecule reactions, or (iii) constitute an heritage on interstellar volatiles trapped in dust (e.g., organics). Likewise, noble gases are elementally and isotopically (1% per amu for xenon) fractionated with respect to the composition of the solar wind (our best proxy for the protosolar nebula composition). Cometary matter directly measured on coma, or in Stardust material, or in IDPs, seems to present among the largest heterogeneities in their stable isotope compositions but knowledge on their precise compositions of the different phases and species is partial and mosty lacking. Among the several important issues requiring a better knowledge of cometary volatiles are the origin(s) of volatile elements on Earth and Moon, on Mars and on Venus, understanding large scale circulation of matter between hot and frozen zones, and the possibility of interstellar heritage for organics. Critical measurements to be made by the next cometary missions include the value of the D/H ratio in water ice, in NH3 and organics. Nitrogen is particularly interesting as cometary HCN and CN are rich in 15N, but an isotoppe mass balance will require to measure the main host species (N2 ?). Noble gases are excellent tracers of physical processes, including the delivery of volatile elements onto planets and atmospheric escape processes, but their cometary inventory is almost not known. The only noble gas (helium and neon) measurement in cometary matter from Stardust suggests that they may be genetically linked to organic matter found in primitive meteorites rather than to the proto-solar gas. Trapping of noble gases in comets is an important issue not only for the physical conditions of cometary formation and evolution, but also for better understanding the possible contribution of cometary matter to Earth and Moon.

On the role of electron-driven processes in planetary atmospheres and comets

NASA Astrophysics Data System (ADS)

Campbell, L.; Brunger, M. J.

2009-11-01

After the presence of ionized layers in the Earth's atmosphere was inferred, it took 50 years to quantitatively understand them. The electron density could not be accounted for until Sir David Bates first suggested (along with Sir Harrie Massey) that the main electron-loss process was dissociative recombination with molecular ions, and he and colleagues then developed a theory to predict those rates of dissociative recombination. However, electron impact processes, particularly excitation, have been considered insignificant in most situations, in both planetary and cometary atmospheres. Here we describe cases where recent calculations have shown that electron impact excitation of molecules is important, suggesting that, just as in the time of Sir David Bates, electron-driven processes remain fundamental to our quantitative understanding of atmospheric and cometary phenomena.

Organic chemistry of cometary dust as derived from PUMA 1 data

NASA Technical Reports Server (NTRS)

Kissel, J.; Krueger, F. R.

1989-01-01

Onboard the Halley Fly-By spacecrafts Vega 1, Vega 2, and Giotto were the dust impact mass spectrometers PUMA 1, PUMA 2, and PIA respectively. PUMA 1 was the most sensitive instrument among them. From its data the occurrence of masslines greater than 60 Daltons could be shown to be statistically significant. An analysis of these masslines lead to a scenario, which could explain the masslines as fragment ions from larger molecules which characterize the chemical nature of cometary organic matter as: (1) highly unsaturated hydrocarbons; (2) some of them containing oxygen; (3) less containing nitrogen; and (4) a few containing oxygen and nitrogen as heteroatoms. From the properties of the spectrometer, also some physical parameters of the dust particles could be inferred, such as their density and structure.

Cometary activity in 2060 Chiron

NASA Technical Reports Server (NTRS)

Luu, Jane X.; Jewitt, David C.

1990-01-01

Results of a 2-yr (1988-90) investigation of cometary activity in 2060 Chiron based on CCD photometry and spectroscopy are reported. The photometry observations include a new rotational light curve of Chiron, a newly refined rotation period, recent developments of its long-term photometric behavior and surface brightness profiles, a deep image of the coma of Chiron, and narrowband images at wavelengths ranging from 3200 to 6840 A. The spectroscopic data include moderate resolution CCD spectra (10-20 A FWHM). Major results include the detection of impulsive brightening on a time scale of hours, evidence for a secular change in the blue portion of the reflectivity spectrum of the nucleus, no evidence for Rayleigh scattering in the near ultraviolet, and an upper limit of the column density of CO(+) ions in the coma.

Charge exchange in cometary coma: Discovery of H− ions in the solar wind close to comet 67P/Churyumov‐Gerasimenko

PubMed Central

Cravens, T. E.; Llera, K.; Goldstein, R.; Mokashi, P.; Tzou, C.‐Y.; Broiles, T.

2015-01-01

Abstract As Rosetta was orbiting comet 67P/Churyumov‐Gerasimenko, the Ion and Electron Sensor detected negative particles with angular distributions like those of the concurrently measured solar wind protons but with fluxes of only about 10% of the proton fluxes and energies of about 90% of the proton energies. Using well‐known cross sections and energy‐loss data, it is determined that the fluxes and energies of the negative particles are consistent with the production of H− ions in the solar wind by double charge exchange with molecules in the coma. PMID:27656008

Angular and energy distribution of low energy cometary ions measured in the outer coma of Comet Halley

NASA Technical Reports Server (NTRS)

Berthelier, J. J.; Illiano, J. M.; Hodges, R. R.; Krankowsky, D.; Eberhardt, P.; Laemmerzahl, P.; Hoffman, J. H.; Herrwerth, I.; Woweries, J.; Dolder, U.

1986-01-01

During the early phase of the Giotto encounter with comet Halley, at distances from the nucleus greater than 350,000 km, the neutral mass spectrometer was operated in a mode allowing the measurement of low energy ions. Data reveal two important features of the outer coma: the presence of a sharp discontinuity in the plasma flow at 550,000 km from the nucleus which results in a significant decrease of the plasma flow accompanied by an increase in temperature; and the detection of newly born ions identified as O(+) and CO(+), at distances from the comet greater than 800,000 km.

Correlated microanalysis of cometary organic grains returned by Stardust

NASA Astrophysics Data System (ADS)

de Gregorio, Bradley T.; Stroud, Rhonda M.; Cody, George D.; Nittler, Larry R.; David Kilcoyne, A. L.; Wirick, Sue

2011-09-01

Abstract- Carbonaceous matter in Stardust samples returned from comet 81P/Wild 2 is observed to contain a wide variety of organic functional chemistry. However, some of this chemical variety may be due to contamination or alteration during particle capture in aerogel. We investigated six carbonaceous Stardust samples that had been previously analyzed and six new samples from Stardust Track 80 using correlated transmission electron microscopy (TEM), X-ray absorption near-edge structure spectroscopy (XANES), and secondary ion mass spectroscopy (SIMS). TEM revealed that samples from Track 35 containing abundant aliphatic XANES signatures were predominantly composed of cometary organic matter infilling densified silica aerogel. Aliphatic organic matter from Track 16 was also observed to be soluble in the epoxy embedding medium. The nitrogen-rich samples in this study (from Track 22 and Track 80) both contained metal oxide nanoparticles, and are likely contaminants. Only two types of cometary organic matter appear to be relatively unaltered during particle capture. These are (1) polyaromatic carbonyl-containing organic matter, similar to that observed in insoluble organic matter (IOM) from primitive meteorites, interplanetary dust particles (IDPs), and in other carbonaceous Stardust samples, and (2) highly aromatic refractory organic matter, which primarily constitutes nanoglobule-like features. Anomalous isotopic compositions in some of these samples also confirm their cometary heritage. There also appears to be a significant labile aliphatic component of Wild 2 organic matter, but this material could not be clearly distinguished from carbonaceous contaminants known to be present in the Stardust aerogel collector.

Titan's ion exosphere observed from Voyager 1

NASA Technical Reports Server (NTRS)

Hartle, R. E.; Sittler, E. C., Jr.; Ogilvie, K. W.; Scudder, J. D.; Lazarus, A. J.; Atreya, S. K.

1982-01-01

The plasma wake surrounding Titan in Saturn's rotating magnetosphere is characterized by a plasma which is denser and cooler than the surrounding subsonic magnetospheric plasma, and which is produced by the deflection of magnetospheric plasma around Titan and the addition of exospheric ions picked up by the rotating magnetosphere. A resemblance to the interaction between the solar wind and Venus is shown for the case of ion pickup in the ion exosphere outside Titan's magnetic tail and ion flow within the boundaries of the tail as Saturn's rotating magnetosphere interacts with Titan. The boundary of the tail is indicated by a sharp reduction in the flux of high-energy electrons, which are removed by inelastic scattering with the atmosphere and centrifugal drift produced when the electrons traverse the magnetic field draped around Saturn.

Effective doping of low energy ions into superfluid helium droplets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Jie; Chen, Lei; Freund, William M.

2015-08-21

We report a facile method of doping cations from an electrospray ionization (ESI) source into superfluid helium droplets. By decelerating and stopping the ion pulse of reserpine and substance P from an ESI source in the path of the droplet beam, about 10{sup 4} ion-doped droplets (one ion per droplet) can be recorded, corresponding to a pickup efficiency of nearly 1 out of 1000 ions. We attribute the success of this simple approach to the long residence time of the cations in the droplet beam. The resulting size of the doped droplets, on the order of 10{sup 5}/droplet, is measuredmore » using deflection and retardation methods. Our method does not require an ion trap in the doping region, which significantly simplifies the experimental setup and procedure for future spectroscopic and diffraction studies.« less

Laboratory simulation of charge exchange-produced X-ray emission from comets.

PubMed

Beiersdorfer, P; Boyce, K R; Brown, G V; Chen, H; Kahn, S M; Kelley, R L; May, M; Olson, R E; Porter, F S; Stahle, C K; Tillotson, W A

2003-06-06

In laboratory experiments using the engineering spare microcalorimeter detector from the ASTRO-E satellite mission, we recorded the x-ray emission of highly charged ions of carbon, nitrogen, and oxygen, which simulates charge exchange reactions between heavy ions in the solar wind and neutral gases in cometary comae. The spectra are complex and do not readily match predictions. We developed a charge exchange emission model that successfully reproduces the soft x-ray spectrum of comet Linear C/1999 S4, observed with the Chandra X-ray Observatory.

Cometary and interstellar dust grains - Analysis by ion microprobe mass spectrometry and other techniques

NASA Technical Reports Server (NTRS)

Zinner, Ernst

1991-01-01

A survey of microanalytical measurements on interplanetary dust particles (IDPs) and interstellar dust grains from primitive meteorites is presented. Ion-microprobe mass spectrometry with its capability to determine isotopic compositions of many elements on a micron spatial scale has played a special role. Examples are measurements of H, N, and O isotopes and refractory trace elements in IDPs; C, N, Mg, and Si isotopes in interstellar SiC grains; and C and N isotopes and H, N, Al, and Si concentrations in interstellar graphite grains.

Energetic Particles in the far and near Environment of Pluto

NASA Astrophysics Data System (ADS)

Kollmann, P.; Hill, M. E.; McNutt, R. L., Jr.; Brown, L. E.; Kusterer, M. B.; Vandegriff, J. D.; Smith, H. T.; Mitchell, D. G.; Haggerty, D. K.; Bagenal, F.; Krimigis, S. M.; Lisse, C. M.; Delamere, P. A.; Elliott, H. A.; Horanyi, M.; McComas, D. J.; Piquette, M. R.; Poppe, A. R.; Sidrow, E. J.; Strobel, D. F.; Szalay, J.; Valek, P. W.; Weidner, S.; Zirnstein, E.; Ennico Smith, K.; Olkin, C.; Weaver, H. A., Jr.; Young, L. A.; Stern, A.

2015-12-01

The New Horizons spacecraft was launched in 2006, passed Jupiter and its magnetotail, took continuous measurements in the solar wind throughout the recent years, and flew by Pluto in July 2015. The onboard PEPSSI instrument measures ion and electron intensities, masses, and energies in the keV to MeV range. The closest approach distance to Pluto was 11 Pluto radii, inside the orbit of Charon. Data taken near Pluto is downlinked throughout August. We will present analysis of this data and set it into context with previous measurements. We expect a number of interesting particle structures around Pluto. Parts of Pluto's molecular nitrogen atmosphere is escaping and will co-orbit with Pluto, potentially forming a partial gas torus. This torus can be additionally sourced by other Kuiper belt objects. The neutrals are eventually ionized and pick-up by the solar wind brings them into the PEPSSI energy range. The measured ion densities can be used to constrain the Pluto torus. Pluto is not expected to have an intrinsic magnetic field, but the energetic particle data can be used to infer its properties, if any. Pluto interacts instead with the solar wind via the pick-up of its ions and the magnetic fields created by currents in its ionosphere. The relative role of these mechanisms can be revealed by the flyby data and directly compared to data that was taken at Jupiter with identical instrumentation.

Discovery of Suprathermal Fe+ in and near Earth's Magnetosphere

NASA Astrophysics Data System (ADS)

Christon, S. P.; Hamilton, D. C.; Plane, J. M. C.; Mitchell, D. G.; Grebowsky, J. M.; Spjeldvik, W. N.; Nylund, S. R.

2017-12-01

Suprathermal (87-212 keV/e) singly charged iron, Fe+, has been observed in and near Earth's equatorial magnetosphere using long-term ( 21 years) Geotail/STICS ion composition data. Fe+ is rare compared to dominant suprathermal solar wind and ionospheric origin heavy ions. Earth's suprathermal Fe+ appears to be positively associated with both geomagnetic and solar activity. Three candidate lower-energy sources are examined for relevance: ionospheric outflow of Fe+ escaped from ion layers altitude, charge exchange of nominal solar wind Fe+≥7, and/or solar wind transported inner source pickup Fe+ (likely formed by solar wind Fe+≥7 interaction with near sun interplanetary dust particles, IDPs). Semi-permanent ionospheric Fe+ layers form near 100 km altitude from the tons of IDPs entering Earth's atmosphere daily. Fe+ scattered from these layers is observed up to 1000 km altitude, likely escaping in strong ionospheric outflows. Using 26% of STICS's magnetosphere-dominated data at low-to-moderate geomagnetic activity levels, we demonstrate that solar wind Fe charge exchange secondaries are not an obvious Fe+ source then. Earth flyby and cruise data from Cassini/CHEMS, a nearly identical instrument, show that inner source pickup Fe+ is likely not important at suprathermal energies. Therefore, lacking any other candidate sources, it appears that ionospheric Fe+ constitutes at least an important portion of Earth's suprathermal Fe+, comparable to observations at Saturn where ionospheric origin suprathermal Fe+ has also been observed.

Structure and dynamics of the umagnetized plasma around comet 67P/CG

NASA Astrophysics Data System (ADS)

Henri, P.; Vallières, X.; Gilet, N.; Hajra, R.; Moré, J.; Goetz, C.; Richter, I.; Glassmeier, K. H.; Galand, M. F.; Heritier, K. L.; Eriksson, A. I.; Nemeth, Z.; Tsurutani, B.; Rubin, M.; Altwegg, K.

2016-12-01

At distances close enough to the Sun, when comets are characterised by a significant outgassing, the cometary neutral density may become large enough for both the cometary plasma and the cometary gas to be coupled, through ion-neutral and electron-neutral collisions. This coupling enables the formation of an unmagnetised expanding cometary ionosphere around the comet nucleus, also called diamagnetic cavity, within which the solar wind magnetic field cannot penetrate. The instruments of the Rosetta Plasma Consortium (RPC), onboard the Rosetta Orbiter, enable us to better constrain the structure, dynamics and stability of the plasma around comet 67P/CG. Recently, magnetic field measurements (RPC-MAG) have shown the existence of such a diamagnetic region around comet 67P/CG [Götz et al., 2016]. Contrary to a single, large scale, diamagnetic cavity such as what was observed around comet Halley, Rosetta have crossed several diamagnetic structures along its trajectory around comet 67P/CG. Using electron density measurements from the Mutual Impedance Probe (RPC-MIP) during the different diamagnetic cavity crossings, identified by the flux gate magnetometer (RPC-MAG), we map the unmagnetised plasma density around comet 67P/CG. Our aims is to better constrain the structure, dynamics and stability of this inner cometary plasma layer characterised by cold electrons (as witnessed by the Langmuir Probes RPC-LAP). The ionisation ratio in these unmagnetised region(s) is computed from the measured electron (RPC-MIP) and neutral gas (ROSINA/COPS) densities. In order to assess the importance of solar EUV radiation as a source of ionisation, the observed electron density will be compared to a the density expected from an ionospheric model taking into account solar radiation absorption. The crossings of diamagnetic region(s) by Rosetta show that the unmagnetised cometary plasma is particularly homogeneous, compared to the highly dynamical magnetised plasma observed in adjacent magnetised regions. Moreover, during the crossings of multiple, successive diamagnetic region(s) over time scales of tens of minutes or hours, the plasma density is almost identical in the different unmagnetised regions, suggesting that these unmagnetised regions may be a single diamagnetic structure crossed several times by Rosetta.

Focused Ion Beam Recovery of Hypervelocity Impact Residue in Experimental Craters on Metallic Foils

NASA Technical Reports Server (NTRS)

Graham, G. A.; Teslich, N.; Dai, Z. R.; Bradley, J. P.; Kearsley, A. T.; Horz, F.

2006-01-01

The Stardust sample return capsule will return to Earth in January 2006 with primitive debris collected from Comet 81P/Wild-2 during the fly-by encounter in 2004. In addition to the cometary particles embedded in low-density silica aerogel, there will be microcraters preserved in the Al foils (1100 series; 100 micrometers thick) that are wrapped around the sample tray assembly. Soda lime spheres (approximately 49 m in diameter) have been accelerated with a light-gas-gun into flight-grade Al foils at 6.35 km s(sup -1) to simulate the potential capture of cometary debris. The preserved crater penetrations have been analyzed using scanning electron microscopy (SEM) and x-ray energy dispersive spectroscopy (EDX) to locate and characterize remnants of the projectile material remaining within the craters. In addition, ion beam induced secondary electron imaging has proven particularly useful in identifying areas within the craters that contain residue material. Finally, high-precision focused ion beam (FIB) milling has been used to isolate and then extract an individual melt residue droplet from the interior wall of an impact penetration. This enabled further detailed elemental characterization, free from the background contamination of the Al foil substrate. The ability to recover pure melt residues using FIB will significantly extend the interpretations of the residue chemistry preserved in the Al foils returned by Stardust.

Progress in Electron Beam Mastering of 100 Gbit/inch2 Density Disc

NASA Astrophysics Data System (ADS)

Takeda, Minoru; Furuki, Motohiro; Yamamoto, Masanobu; Shinoda, Masataka; Saito, Kimihiro; Aki, Yuichi; Kawase, Hiroshi; Koizumi, Mitsuru; Miyokawa, Toshiaki; Mutou, Masao; Handa, Nobuo

2004-07-01

We developed an electron beam recorder (EBR) capable of recording master discs under atmospheric conditions using a novel differential pumping head. Using the EBR and optimized fabrication process for Si-etched discs with reactive ion etching (RIE), a bottom signal jitter of 9.6% was obtained from a 36 Gbit/inch2 density disc, readout using a near-field optical pickup with an effective numerical aperture (NA) of 1.85 and a wavelength of 405 nm. We also obtained the eye patterns from a 70 Gbit/inch2 density disc readout using an optical pickup with a 2.05 NA and the same wavelength, and showed almost the same modulation ratio as the simulation value. Moreover, the capability of producing pit patterns corresponding to a 104 Gbit/inch2 density is demonstrated.

Pickup Ion Dynamics in the Outer Heliosheath Associated with the Growth of Kelvin-Helmholtz Instability at the Heliopause

NASA Astrophysics Data System (ADS)

Tsubouchi, K.

2017-12-01

A discovery of "IBEX ribbon", localized bright emission of energetic neutral atoms, has brought new insights into the plasma environment of its source region beyond the heliosphere. It has been basically established that its geometrical property is associated with the local interstellar magnetic field draped on the heliopause, and pickup ions (PUIs) in the outer heliosheath (OHS) must be its primary source particles. Understanding the PUI dynamics in OHS more in detail is our motivation for this study. We performed two-dimensional hybrid simulations to evaluate the response of PUIs to the structural variation in the heliosheath. We assumed the simulation system such that the background plasma is hot solar wind in the inner heliosheath and cold interstellar plasma in OHS, and the directions of these flows are tangential to the heliopause. Such a situation leads to the growth of Kelvin-Helmholtz instability (KHI), where the plasma mixing and turbulence excitation takes place. We identified that non-stationarity and non-uniformity emerges in the PUI density structure in a specific energy range as KHI process advances. Relevance of these results to the expected observation like IBEX ribbon will be discussed.

Plasmas in the outer heliosphere

NASA Technical Reports Server (NTRS)

Belcher, J. W.; Richardson, J. D.; Lazarus, A. J.; Gazis, P. R.; Barnes, A.

1995-01-01

We review the observed properties of the solar wind in the outer heliosphere, including observations from Voyager and the Pioneers, as well as from inner heliospheric probes as appropriate. These observations are crucial to modeling of the heliosphere and its interactions with the interstellar medium, since the wind ram pressure and its temporal variations are important in understanding the distance to the termination shock and heliopause and how those boundaries might vary in time. We focus on results since Solar Wind 7. Among the issues we will discuss are: (1) the time scales for and statistical properties of variations in the ram pressure in the outer heliosphere, and how those variations might affect the morphology of the heliospheric/interstellar medium interface; (2) the question of possible solar wind slowing in the outer heliosphere due to the pick-up of interstellar ions; (3) the issue of whether there is bulk heating of the solar wind associated either with interstellar ion pick-up or with continued heating due to stream-stream interactions; (4) evidence for latitudinal variations in solar wind properties; and (5) the 1.3 year periodicities apparent in the outer heliosphere, and the close correspondence with similar variations seen with inner heliospheric probes.

CHANDRA OBSERVATIONS OF COMETS C/2012 S1 (ISON) AND C/2011 L4 (PanSTARRS)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Snios, Bradford; Kharchenko, Vasili; Lisse, Carey M.

2016-02-20

We present our results on the Chandra X-ray Observatory Advanced CCD Imaging Spectrometer (ACIS) observations of the bright Oort Cloud comets C/2012 S1 (ISON) and C/2011 L4 (PanSTARRS). ISON was observed between 2013 October 31–November 06 during variable speed solar wind (SW), and PanSTARRS was observed between 2013 April 17–23 during fast SW. ISON produced an extended parabolic X-ray morphology consistent with a collisionally thick coma, while PanSTARRS demonstrated only a diffuse X-ray-emitting region. We consider these emissions to be from charge exchange (CX) and model each comet's emission spectrum from first principles accordingly. Our model agrees with the observationalmore » spectra and also generates composition ratios for heavy, highly charged SW ions interacting with the cometary atmosphere. We compare our derived SW ion compositions to observational data and find a strong agreement between them. These results further demonstrate the utility of CX emissions as a remote diagnostics tool of both astrophysical plasma interaction and SW composition. In addition, we observe potential soft X-ray emissions via ACIS around 0.2 keV from both comets that are correlated in intensity to the hard X-ray emissions between 0.4–1.0 keV. We fit our CX model to these emissions, but our lack of a unique solution at low energies makes it impossible to conclude if they are cometary CX in origin. Finally, we discuss probable emission mechanism sources for the soft X-rays and explore new opportunities these findings present in understanding cometary emission processes via Chandra.« less

ORTHO-TO-PARA ABUNDANCE RATIO OF WATER ION IN COMET C/2001 Q4 (NEAT): IMPLICATION FOR ORTHO-TO-PARA ABUNDANCE RATIO OF WATER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shinnaka, Yoshiharu; Kawakita, Hideyo; Kobayashi, Hitomi

2012-04-20

The ortho-to-para abundance ratio (OPR) of cometary molecules is considered to be one of the primordial characteristics of cometary ices, and contains information concerning their formation. Water is the most abundant species in cometary ices, and OPRs of water in comets have been determined from infrared spectroscopic observations of H{sub 2}O rovibrational transitions so far. In this paper, we present a new method to derive OPR of water in comets from the high-dispersion spectrum of the rovibronic emission of H{sub 2}O{sup +} in the optical wavelength region. The rovibronic emission lines of H{sub 2}O{sup +} are sometimes contaminated by othermore » molecular emission lines but they are not affected seriously by telluric absorption compared with near-infrared observations. Since H{sub 2}O{sup +} ions are mainly produced from H{sub 2}O by photoionization in the coma, the OPR of H{sub 2}O{sup +} is considered to be equal to that of water based on the nuclear spin conservation through the reaction. We have developed a fluorescence excitation model of H{sub 2}O{sup +} and applied it to the spectrum of comet C/2001 Q4 (NEAT). The derived OPR of water is 2.54{sup +0.32}{sub -0.25}, which corresponds to a nuclear spin temperature (T{sub spin}) of 30{sup +10}{sub -4} K. This is consistent with the previous value determined in the near-infrared for the same comet (OPR = 2.6 {+-} 0.3, T{sub spin} = 31{sup +11}{sub -5} K).« less

Higher Energy Plasma Ions found near the Termination Shock: Analyses of Voyager 2 Data in the Heliosheath and in the Outer Heliosphere

NASA Technical Reports Server (NTRS)

Intriligator, Devrie S.; Intriligator, James; Miller, W. David; Webber, William R.; Decker, Robert B.

2010-01-01

We have found in the Voyager 2 (V2) plasma science data in the heliosheath (HS) near the termination shock (TS) high-energy ions (HEIs) in addition to the bulk plasma convective flow ions. The HEI detections temporally coincide with increased V2 plasma wave subsystem (PWS) activity in "event A"h of Gurnett and Kurth. Maxwellian fits to HEI detections indicate the HEIs are moving radially anti -Sunward with a proton speed of 600 km/s, a density of 10(exp -4) (exp -3), and a thermal speed of 10 km/s. The heliosheath bulk convective protons have a speed of 204 km/s, a density of 0.0029 cm(exp -3), and a thermal speed of 26.7 km/s. The HEI flux and ram pressure are approximately 10% and 30% of those of the bulk HS flow. Since the HEI speed is both close to twice the solar wind speed and independent of the heliosheath bulk plasma speed, the HEIs may be detections of pickup protons formed in the solar wind and convected through the TS. The HEIs also are reminiscent of the pickup protons upstream of the Mars bow shock where their energy also was independent of the bulk plasma speed and attributed to multiple reflections off the Mars bow shock. Gurnett and Kurth 's (2008) event A enhanced PWS activity may be generated by a two ]stream instability from the interaction of these HEIs with the heliosheath bulk plasma ions. We present our findings, discuss their implications, and also present alternative interpretations.

Cometary activity in 2060 Chiron

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luu, J.X.; Jewitt, D.C.

Results of a 2-yr (1988-90) investigation of cometary activity in 2060 Chiron based on CCD photometry and spectroscopy are reported. The photometry observations include a new rotational light curve of Chiron, a newly refined rotation period, recent developments of its long-term photometric behavior and surface brightness profiles, a deep image of the coma of Chiron, and narrowband images at wavelengths ranging from 3200 to 6840 A. The spectroscopic data include moderate resolution CCD spectra (10-20 A FWHM). Major results include the detection of impulsive brightening on a time scale of hours, evidence for a secular change in the blue portionmore » of the reflectivity spectrum of the nucleus, no evidence for Rayleigh scattering in the near ultraviolet, and an upper limit of the column density of CO(+) ions in the coma. 46 refs.« less

The study of comets, part 1. [conference on photometry and spectrum analysis of Kohoutek comet and comet tails

NASA Technical Reports Server (NTRS)

Donn, B. (Editor); Mumma, M. J. (Editor); Jackson, W. M. (Editor); Ahearn, M. (Editor); Harrington, R. (Editor)

1976-01-01

Papers are presented dealing with observations of comets. Topic discussed include: photometry, polarimetry, and astrometry of comets; detection of water and molecular transitions in comets; ion motions in comet tails; determination of comet brightness and luminosity; and evolution of cometary orbits. Emphasis is placed on analysis of observations of comet Kohoutek.

Observation of pick-up ions in the solar wind: Evidence for the source of the anomalous cosmic ray component?

NASA Technical Reports Server (NTRS)

Hovestadt, D.; Moebius, E.; Klecker, B.; Scholer, M.; Gloeckler, G.; Ipavich, F. M.

1985-01-01

Singly ionized energetic helium has been observed in the solar wind by using the time of flight spectrometer SULEICA on the AMPTE/IRM satellite between September and December, 1984. The energy density spectrum shows a sharp cut off which is strongly correlated with the four fold solar wind bulk energy. The absolute flux of the He(+)ions of about 10000 ion/sq cm.s is present independent of the IPL magnetic field orientation. The most likely source is the neutral helium of the interstellar wind which is ionized by solar UV radiation. It is suggested that these particles represent the source of the anomalous cosmic ray component.

ULF waves at comets Halley and Giacobini-Zinner - Comparison with simulations

NASA Astrophysics Data System (ADS)

Le, G.; Russell, C. T.; Gary, S. P.; Smith, E. J.; Riedler, W.; Schwingenschuh, K.

1989-09-01

A comparison is made between observations and numerical simulations of magnetic fluctuations near the proton and water group ion cyclotron frequencies as a function of distance from the comets Halley and Giacobini-Zinner. The amplitude of waves due to different cyclotron resonant instabilities is monitored by examining the amplitude of waves near the gyrofrequency of the respective ions, measured in by the ICE spacecraft. The results are compared with a one-dimensional electromagnetic hybrid simulation of two-ion pickup based on the predictions of Gary et al. (1989). The observations are consistent with the prediction that amplitudes are dependent on the properties of the injected beams and the local injection rate.

Protein and peptide cross sections and mass spectra in an electrostatic ion beam trap

NASA Astrophysics Data System (ADS)

Fradkin, Z.; Strasser, D.; Heber, O.; Rappaport, M. L.; Sharon, M.; Thomson, B. A.; Rahinov, I.; Toker, Y.; Zajfman, D.

2017-05-01

Among the advantages of an electrostatic ion beam trap (EIBT), which is based on purely electrostatic fields, are mass-unlimited trapping and ease of operation. We have developed a new system that couples an electrospray ion source to an EIBT. Between the source and EIBT there is a Paul trap in which the ions are accumulated before being extracted and accelerated. After the ion bunch has entered the EIBT, the ions are trapped by rapidly raising the voltages on the entrance mirror. The oscillations of the bunch are detected by amplifying the charge induced on a pickup ring in the center of the trap, the ion mass being directly proportional to the square of the oscillation period. The trapping of biomolecules in the RF-bunching mode of the EIBT is used for measurement of mass spectra and collision cross sections. Coalescence of bunches of ions of nearby mass in the self-bunching mode is also demonstrated.

Pickup ion acceleration in the successive appearance of corotating interaction regions

NASA Astrophysics Data System (ADS)

Tsubouchi, K.

2017-04-01

Acceleration of pickup ions (PUIs) in an environment surrounded by a pair of corotating interaction regions (CIRs) was investigated by numerical simulations using a hybrid code. Energetic particles associated with CIRs have been considered to be a result of the acceleration at their shock boundaries, but recent observations identified the ion flux peaks in the sub-MeV to MeV energy range in the rarefaction region, where two separate CIRs were likely connected by the magnetic field. Our simulation results confirmed these observational features. As the accelerated PUIs repeatedly bounce back and forth along the field lines between the reverse shock of the first CIR and the forward shock of the second one, the energetic population is accumulated in the rarefaction region. It was also verified that PUI acceleration in the dual CIR system had two different stages. First, because PUIs have large gyroradii, multiple shock crossing is possible for several tens of gyroperiods, and there is an energy gain in the component parallel to the magnetic field via shock drift acceleration. Second, as the field rarefaction evolves and the radial magnetic field becomes dominant, Fermi-type reflection takes place at the shock. The converging nature of two shocks results in a net energy gain. The PUI energy acquired through these processes is close to 0.5 MeV, which may be large enough for further acceleration, possibly resulting in the source of anomalous cosmic rays.

Kinetic Properties of the Neutral Solar Wind

NASA Astrophysics Data System (ADS)

Florinski, V.; Heerikhuisen, J.

2017-03-01

Charge-exchange collisions between the solar wind protons and interstellar hydrogen produce a distinctive population of neutral hydrogen streaming radially at nearly the solar-wind speed. This tenuous population, known as the neutral solar wind (NSW) is thought to play a key role in the appearance of the Interplanetary Boundary EXplorer ribbon, a bright circular band in the sky that is the source of neutral hydrogen with energies near 1 keV. According to the leading model of the ribbon, the velocity distribution of NSW hydrogen is imparted on the pickup ions (PUIs) generated via charge exchange with the interstellar protons beyond the heliopause, and in this way controls the stability of the resulting ring distribution of PUIs against hydromagnetic wave generation. In this paper, we examine the velocity distributions of the NSW atoms in the heliosphere and the outer heliosheath regions by following the phase-space trajectories of the Boltzmann equation. It is demonstrated that these distributions are highly anisotropic, with the parallel (radial) temperature greatly exceeding the perpendicular temperature. Ions picked up near 90° from the anisotropic NSW would form a stable ring distribution capable of generating the ribbon flux. We also discuss a second population of neutrals born in charge transfer collisions with interstellar PUIs, the so-called neutralized pickup ion (NPI) component. Their high thermal velocities translate into large parallel velocity spread of the daughter ribbon PUIs, which would adversely affect plasma stability in local interstellar space.

Chemical Recycling of Molecules in Cometary Comae

NASA Astrophysics Data System (ADS)

Boice, Daniel C.; Kawakita, Hideyo; Shinnaka, Yoshiharu; Kobayashi, Hitomi

2015-08-01

Modeling is essential to understand the important physical and chemical processes that occur in cometary comae, especially the relationship between native and sibling molecules, such as, HCN and CN. Photochemistry is a major source of ions and electrons that further initiate key gas-phase reactions, leading to the plethora of molecules and atoms observed in comets. The effects of photoelectrons that react via impacts are important to the overall ionization in the inner coma. We have found that many molecules undergo protonation reactions with primarily water, followed by electron recombination resulting in the original molecules in a vibrationally excited state. These excited molecules spontaneously emit photons back to the ground state. We identify this series of reactions as chemical “recycling.” We discuss the importance of this mechanism for HCN, NH3, and water in comets. We also identify other relevant processes in the collision-dominated, inner coma of a comet within a global modeling framework to better understand observations and in situ measurements of cometary species, especially relationships between native and sibling molecules for the Rosetta Mission to Comet 67P/Churyumov-Gerasimenko.Acknowledgements: We appreciate support from the NSF Planetary Astronomy Program under Grant No. 0908529. This program is partially supported by the MEXT Supported Program for the Strategic Research Foundation at Private Universities, 2014-2018.

Strong plume fluxes at Mars observed by MAVEN: An important planetary ion escape channel

NASA Astrophysics Data System (ADS)

Dong, Y.; Fang, X.; Brain, D. A.; McFadden, J. P.; Halekas, J. S.; Connerney, J. E.; Curry, S. M.; Harada, Y.; Luhmann, J. G.; Jakosky, B. M.

2015-11-01

We present observations by the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission of a substantial plume-like distribution of escaping ions from the Martian atmosphere, organized by the upstream solar wind convection electric field. From a case study of MAVEN particle-and-field data during one spacecraft orbit, we identified three escaping planetary ion populations: plume fluxes mainly along the upstream electric field over the north pole region of the Mars-Sun-Electric field (MSE) coordinate system, antisunward ion fluxes in the tail region, and much weaker upstream pickup ion fluxes. A statistical study of O+ fluxes using 3 month MAVEN data shows that the plume is a constant structure with strong fluxes widely distributed in the MSE northern hemisphere, which constitutes an important planetary ion escape channel. The escape rate through the plume is estimated to be ~30% of the tailward escape and ~23% of the total escape for > 25 eV O+ ions.

The Influence of Pickup Protons, from Interstellar Neutral Hydrogen, on the Propagation of Interplanetary Shocks from the Halloween 2003 Solar Events to ACE and Ulysses: A 3-D MHD Modeling Study

NASA Technical Reports Server (NTRS)

Detman, T. R.; Intriligator, D. S.; Dryer, M.; Sun, W.; Deehr, C. S.; Intriligator, J.

2012-01-01

We describe our 3-D, time ]dependent, MHD solar wind model that we recently modified to include the physics of pickup protons from interstellar neutral hydrogen. The model has a time-dependent lower boundary condition, at 0.1 AU, that is driven by source surface map files through an empirical interface module. We describe the empirical interface and its parameter tuning to maximize model agreement with background (quiet) solar wind observations at ACE. We then give results of a simulation study of the famous Halloween 2003 series of solar events. We began with shock inputs from the Fearless Forecast real ]time shock arrival prediction study, and then we iteratively adjusted input shock speeds to obtain agreement between observed and simulated shock arrival times at ACE. We then extended the model grid to 5.5 AU and compared those simulation results with Ulysses observations at 5.2 AU. Next we undertook the more difficult tuning of shock speeds and locations to get matching shock arrival times at both ACE and Ulysses. Then we ran this last case again with neutral hydrogen density set to zero, to identify the effect of pickup ions. We show that the speed of interplanetary shocks propagating from the Sun to Ulysses is reduced by the effects of pickup protons. We plan to make further improvements to the model as we continue our benchmarking process to 10 AU, comparing our results with Cassini observations, and eventually on to 100 AU, comparing our results with Voyager 1 and 2 observations.

Synthesis of formamide and isocyanic acid after ion irradiation of frozen gas mixtures

NASA Astrophysics Data System (ADS)

Kaňuchová, Z.; Urso, R. G.; Baratta, G. A.; Brucato, J. R.; Palumbo, M. E.; Strazzulla, G.

2016-01-01

Context. Formamide (NH2HCO) and isocyanic acid (HNCO) have been observed as gaseous species in several astronomical environments such as cometary comae and pre- and proto-stellar objects. A debate is open on the formation route of those molecules, in particular if they are formed by chemical reactions in the gas phase and/or on grains. In this latter case it is relevant to understand if the formation occurs through surface reactions or is induced by energetic processing. Aims: We present arguments that support the formation of formamide in the solid phase by cosmic-ion-induced energetic processing of ices present as mantles of interstellar grains and on comets. Formamides, along with other molecules, are expelled in the gas phase when the physical parameters are appropriate to induce the desorption of ices. Methods: We have performed several laboratory experiments in which ice mixtures (H2O:CH4:N2, H2O:CH4:NH3, and CH3OH:N2) were bombarded with energetic (30-200 keV) ions (H+ or He+). FTIR spectroscopy was performed before, during, and after ion bombardment. In particular, the formation of HNCO and NH2HCO was measured quantiatively. Results: Energetic processing of ice can quantitatively reproduce the amount of NH2HCO observed in cometary comae and in many circumstellar regions. HNCO is also formed, but additional formation mechanisms are requested to quantitatively account for the astronomical observations. Conclusions: We suggest that energetic processing of ices in the pre- and proto-stellar regions and in comets is the main mechanism to produce formamide, which, once it is released in the gas phase because of desorption of ices, is observed in the gas phase in these astrophysical environments.

Ulysses Observations of Magnetic Waves due to Newborn Interstellar Pickup Ions. I. New Observations and Linear Analysis

NASA Astrophysics Data System (ADS)

Cannon, Bradford E.; Smith, Charles W.; Isenberg, Philip A.; Vasquez, Bernard J.; Murphy, Neil; Nuno, Raquel G.

2014-04-01

We have examined Ulysses magnetic field data using dynamic spectrogram techniques that compute wave amplitude, polarization, and direction of propagation over a broad range of frequencies and time. Events were identified that showed a strong polarization signature and an enhancement of power above the local proton gyrofrequency. We perform a statistical study of 502 wave events in an effort to determine when, where, and why they are observed. Most notably, we find that waves arising from newborn interstellar pickup ions are relatively rare and difficult to find. The quantities normally employed in theories of wave growth are neutral atom density and quantities related to their ionization and the subsequent dynamics such as wind speed, solar wind flux, and magnetic field orientation. We find the observations of waves to be largely uncorrelated to these quantities except for mean field direction where quasi-radial magnetic fields are favored and solar wind proton flux where wave observations appear to be favored by low flux conditions which runs contrary to theoretical expectations of wave generation. It would appear that an explanation based on source physics and instability growth rates alone is not adequate to account for the times when these waves are seen.

Solar cycle variation of interstellar neutral He, Ne, O density and pick-up ions along the Earth's orbit

NASA Astrophysics Data System (ADS)

Sokół, Justyna M.; Bzowski, Maciej; Kubiak, Marzena A.; Möbius, Eberhard

2016-06-01

We simulated the modulation of the interstellar neutral (ISN) He, Ne, and O density and pick-up ion (PUI) production rate and count rate along the Earth's orbit over the solar cycle (SC) from 2002 to 2013 to verify if SC-related effects may modify the inferred ecliptic longitude of the ISN inflow direction. We adopted the classical PUI model with isotropic distribution function and adiabatic cooling, modified by time- and heliolatitude-dependent ionization rates and non-zero injection speed of PUIs. We found that the ionization losses have a noticeable effect on the derivation of the ISN inflow longitude based on the Gaussian fit to the crescent and cone peak locations. We conclude that the non-zero radial velocity of the ISN flow and the energy range of the PUI distribution function that is accumulated are of importance for a precise reproduction of the PUI count rate along the Earth orbit. However, the temporal and latitudinal variations of the ionization in the heliosphere, and particularly their variation on the SC time-scale, may significantly modify the shape of PUI cone and crescent and also their peak positions from year to year and thus bias by a few degrees the derived longitude of the ISN gas inflow direction.

INTERSTELLAR PICK-UP IONS OBSERVED BETWEEN 11 AND 22 AU BY NEW HORIZONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Randol, B. M.; McComas, D. J.; Schwadron, N. A., E-mail: brentrandol@gmail.com

We report new observations by the Solar Wind Around Pluto instrument on the New Horizons spacecraft, which measures energy per charge (E/q) spectra of solar wind and interstellar pick-up ions (PUIs) between 11 AU and 22 AU from the Sun. The data provide an unprecedented look at PUIs as there have been very few measurements of PUIs beyond 10 AU. We analyzed the PUI part of the spectra by comparing them to the classic Vasyliunas and Siscoe PUI model. Our analysis indicates that PUIs are usually well-described by this distribution. We derive parameters relevant to PUI studies, such as themore » ionization rate normalized to 1 AU. Our result for the average ionization rate between 11 and 12 AU agrees with an independently derived average value found during the same time. Later, we find a general increase in the ionization rate, which is consistent with the increase in solar activity. We also calculate the PUI thermal pressure, which appears to be roughly consistent with previous results. Through fitting of the solar wind proton peaks in our spectra, we derive solar wind thermal pressures. Based on our analysis, we predict a ratio of PUI thermal pressure to solar wind thermal pressure just inside the termination shock to be between 100 and >1000.« less

Reactions of nitriles in ices relevant to Titan, comets, and the interstellar medium: formation of cyanate ion, ketenimines, and isonitriles

NASA Astrophysics Data System (ADS)

Hudson, R. L.; Moore, M. H.

2004-12-01

Motivated by detections of nitriles in Titan's atmosphere, cometary comae, and the interstellar medium, we report laboratory investigations of the low-temperature chemistry of acetonitrile, propionitrile, acrylonitrile, cyanoacetylene, and cyanogen (CH 3CN, CH 3CH 2CN, CH 2CHCN, HCCCN, and NCCN, respectively). A few experiments were also done on isobutyronitrile and trimethylacetonitrile ((CH 3) 2CHCN and (CH 3) 3CCN, respectively). Trends were sought, and found, in the photo- and radiation chemical products of these molecules at 12-25 K. In the absence of water, all of these molecules isomerized to isonitriles, and CH 3CN, CH 3CH 2CN, and (CH 3) 2CHCN also formed ketenimines. In the presence of H 2O, no isonitriles were detected but rather the cyanate ion (OCN -) was seen in all cases. Although isonitriles, ketenimines, and OCN - were the main focus of our work, we also describe cases of hydrogen loss, to make smaller nitriles, and hydrogen addition (reduction), to make larger nitriles. HCN formation also was seen in most experiments. The results are presented in terms of nitrile ice chemistry on Titan, in cometary ice, and in the interstellar medium. Possible connections to prebiotic chemistry are briefly discussed.

75 FR 3252 - Ford Motor Company, Dearborn Truck Plant, Dearborn, MI; Notice of Negative Determination on...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-01-20

... hand, the like articles are specifically Ford F Series pickups and Lincoln Mark LT sports-utility... Series pickups and Lincoln Mark LR sports-utility pickups and there was no shift/acquisition of production of Ford F Series pickups and Lincoln Mark LR sports-utility pickups to/from a foreign country. The...

XUV-Exposed, Non-Hydrostatic Hydrogen-Rich Upper Atmospheres of Terrestrial Planets. Part II: Hydrogen Coronae and Ion Escape

PubMed Central

Lammer, Helmut; Holmström, Mats; Panchenko, Mykhaylo; Odert, Petra; Erkaev, Nikolai V.; Leitzinger, Martin; Khodachenko, Maxim L.; Kulikov, Yuri N.; Güdel, Manuel; Hanslmeier, Arnold

2013-01-01

Abstract We studied the interactions between the stellar wind plasma flow of a typical M star, such as GJ 436, and the hydrogen-rich upper atmosphere of an Earth-like planet and a “super-Earth” with a radius of 2 REarth and a mass of 10 MEarth, located within the habitable zone at ∼0.24 AU. We investigated the formation of extended atomic hydrogen coronae under the influences of the stellar XUV flux (soft X-rays and EUV), stellar wind density and velocity, shape of a planetary obstacle (e.g., magnetosphere, ionopause), and the loss of planetary pickup ions on the evolution of hydrogen-dominated upper atmospheres. Stellar XUV fluxes that are 1, 10, 50, and 100 times higher compared to that of the present-day Sun were considered, and the formation of high-energy neutral hydrogen clouds around the planets due to the charge-exchange reaction under various stellar conditions was modeled. Charge-exchange between stellar wind protons with planetary hydrogen atoms, and photoionization, lead to the production of initially cold ions of planetary origin. We found that the ion production rates for the studied planets can vary over a wide range, from ∼1.0×1025 s−1 to ∼5.3×1030 s−1, depending on the stellar wind conditions and the assumed XUV exposure of the upper atmosphere. Our findings indicate that most likely the majority of these planetary ions are picked up by the stellar wind and lost from the planet. Finally, we estimated the long-time nonthermal ion pickup escape for the studied planets and compared them with the thermal escape. According to our estimates, nonthermal escape of picked-up ionized hydrogen atoms over a planet's lifetime within the habitable zone of an M dwarf varies between ∼0.4 Earth ocean equivalent amounts of hydrogen (EOH) to <3 EOH and usually is several times smaller in comparison to the thermal atmospheric escape rates. Key Words: Stellar activity—Low-mass stars—Early atmospheres—Earth-like exoplanets—Energetic neutral atoms—Ion escape—Habitability. Astrobiology 13, 1030–1048. PMID:24283926

Charge exchange avalanche at the cometopause

NASA Astrophysics Data System (ADS)

Gombosi, T. I.

1987-11-01

A sharp transition from a solar wind proton dominated flow to a plasma population primarily consisting of relatively cold cometary heavy ions has been observed at a cometocentric distance of about 160,000 km by the VEGA and GIOTTO missions. This boundary (the cometopause) was thought to be related to charge transfer processes, but its location and thickness are inconsistent with conventionally estimated ion - neutral coupling boundaries. In this paper a two-fluid model is used to investigate the major physical processes at the cometopause. By adopting observed comet Halley parameters the model is able to reproduce the location and the thickness of this charge exchange boundary.

The identification of H3S(+) with the ion of mass per charge (m/q) 35 observed in the coma of Comet Halley

NASA Technical Reports Server (NTRS)

Marconi, M. L.; Mendis, D. A.; Korth, A.; Lin, R. P.; Mitchell, D. L.

1990-01-01

A sharp peak in the mass spectrum at 35 amu is observed by the heavy ion analyzer on board the Giotto spacecraft just inside the ionopause. This peak is identified with H3S(+) and it is argued that the dominant source of its likely parent molecule (H2S) is the observed distributed source of circumnuclear dust, rather than the central nucleus. In this case, the total production rate of H2S is more than about 0.5 percent that of the dominant cometary molecule H2O.

Solar wind mass-loading at Comet Halley - A lesson from Venus?

NASA Astrophysics Data System (ADS)

Breus, T. K.; Krymskii, A. M.; Luhmann, J. G.

1987-05-01

Recent observations at comet Halley show that the region within which cometary ions become the dominant component lies outside of the magnetic field-free cavity. This behavior resembles that found at Venus under conditions where the incident solar wind dynamic pressure exceeds the ionospheric pressure. On these occasions the magnetosheath magnetic field is found well inside of the region where planetary ions are observed. Although scaling and the details of formation of the inner boundary of the magnetic field are different for these two objects, the processes by which the interplanetary magnetic field penetrates into the ionospheres at Venus and at comet Halley are in many ways analogous.

Proceedings of the Shuttle-based Cometary Science Workshop: a Forum for the Presentation and Discussion of Possible Shuttle-based Experiments and Observations of Comets and Cometary-like Materials

NASA Technical Reports Server (NTRS)

Gary, G. A. (Editor); Clifton, K. S. (Editor)

1976-01-01

The prospects of cometary research from the space shuttle are examined. Topics include: the shuttle as research environment; on-board experiments at zero-gravity and release of gas and dust to simulate cometary phenomena; and cometary observations from space.

Multi-fluid MHD Study of the Solar Wind Interaction with Mars' Upper Atmosphere during the 2015 March 8th ICME Event

NASA Astrophysics Data System (ADS)

Dong, C.; Ma, Y.; Bougher, S. W.; Toth, G.; Nagy, A. F.; Halekas, J. S.; Dong, Y.; Curry, S.; Luhmann, J. G.; Brain, D. A.; Connerney, J. E. P.; Espley, J. R.; Mahaffy, P. R.; Benna, M.; McFadden, J. P.; Mitchell, D. L.; DiBraccio, G. A.; Lillis, R. J.; Jakosky, B. M.; Grebowsky, J. M.

2015-12-01

The 3-D Mars multi-fluid BATS-R-US MHD code is used to study the solar wind interaction with the Martian upper atmosphere during the 2015 March 8th interplanetary coronal mass ejection (ICME). We studied four steady-state cases, corresponding to three major ICME phases: pre-ICME phase (Case 1), sheath phase (Cases 2--3), and ejecta phase (Case 4). Detailed data-model comparisons demonstrate that the simulation results are in good agreement with Mars Atmosphere and Volatile EvolutioN (MAVEN) measurements, indicating that the multi-fluid MHD model can reproduce most of the features observed by MAVEN, thus providing confidence in the estimate of ion escape rates from its calculation. The total ion escape rate is increased by an order of magnitude, from 2.05×1024 s-1 (pre-ICME phase) to 2.25×1025 s-1 (ICME sheath phase), during this time period. The calculated ion escape rates were used to examine the relative importance of the two major ion loss channels from the planet: energetic pickup ion loss through the dayside plume and cold ionospheric ion loss through the nightside plasma wake region. We found that the energetic pickup ions escaping from the dayside plume could be as much as ~23% of the total ion loss prior to the ICME arrival. Interestingly, the tailward ion escape rate is significantly increased at the ejecta phase, leading to a reduction of the dayside ion escape to ~5% of the total ion loss. Under such circumstance, the cold ionospheric ions escaping from the plasma wake comprise the majority of the ion loss from the planet. Furthermore, by comparing four simulation results along the same MAVEN orbit, we note that there is no significant variation in the Martian lower ionosphere. Finally, both bow shock and magnetic pileup boundary (BS, MPB) locations are decreased from (1.2 RMars, 1.57 RMars) at the pre-ICME phase to (1.16 RMars, 1.47 RMars) respectively during the sheath phase along the dayside Sun-Mars line. MAVEN has provided a great opportunity to study the evolution of the Martian atmosphere and climate over its history. A large quantity of useful data has been returned for future studies. These kinds of data-model comparisons can help the community to better understand the Martian upper atmosphere response to the (extreme) variation in the solar wind and its interplanetary environment from a global perspective.

Study of the coma of comet 67P/Churyumov-Gerasimenko based on the ROSINA/RTOF instrument onboard Rosetta

NASA Astrophysics Data System (ADS)

Hoang, M.; Garnier, P.; Lasue, J.; Reme, H.; Altwegg, K.; Balsiger, H. R.; Bieler, A. M.; Calmonte, U.; Fiethe, B.; Galli, A.; Gasc, S.; Gombosi, T. I.; Jäckel, A.; Mall, U.; Le Roy, L.; Rubin, M.; Tzou, C. Y.; Waite, J. H., Jr.; Wurz, P.

2015-12-01

The ROSETTA spacecraft of ESA is in the environment of comet 67P/Churyumov-Gerasimenko since August 2014. Among the experiments onboard the spacecraft, the ROSINA experiment (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) includes two mass spectrometers (DFMS and RTOF) to analyze the composition of neutrals and ions, and a pressure sensor (COPS) to monitor the density and velocity of neutrals in the coma [1]. We will here analyze and discuss the data of the ROSINA/RTOF instrument during the comet escort phase. The Reflectron-type Time-Of-Flight (RTOF) mass spectrometer possesses a wide mass range and a high temporal resolution [1,2]. It was designed to measure cometary neutral gas as well as cometary ions. A detailed description of the main volatiles (H2O, CO2, CO) dynamics and of the heterogeneities of the coma will then be provided. The influence of various parameters on the coma measurements is investigated on a statistical basis, with the parameters being distance to the comet, heliocentric distance, longitude and latitude of nadir point. Our analysis of the northern hemisphere summer season shows the presence of water vapor mostly in the illuminated northern hemisphere near the neck region with cyclic diurnal variations whereas CO2 was confined to the cold southern hemisphere with a more spatially homogeneous composition, in agreement with previous observations of 67P [2] or Hartley 2 [3]. A comparison will also be provided with the COPS total density and DFMS abundance measurements. [1] Balsiger et al., "ROSINA - Rosetta Orbiter Spectrometer for Ion and Neutral Analysis", Space Sci. Rev., 2007. [2] Scherer et al., "A novel principle for an ion mirror design in time-of-flight mass spectrometry," Int. Jou. Mass Spectr., 2006. [3] Hässig et al., "Time variability and heterogeneity in the coma of 67P/Churyumov-Gerasimenko", Science, 2015. [4] A'Hearn et al., "EPOXI at comet Hartley 2", Science, 2011.

Investigating Global Ion and Neutral Atom Populations with IBEX and Voyager

NASA Technical Reports Server (NTRS)

Florinski, Vladimir

2016-01-01

The main objective of this project was to investigate pickup ion (PUI) production in the solar wind and heliosheath (the region between the termination shock and the heliopause) and compute the distributed energetic neutral atom fluxes throughout the helioshpere. The simulations were constrained by comparing the model output against observations from Ulysses, New Horizons, Voyager 1 and 2, and IBEX space probes. As evidenced by the number of peer reviewed journal publications resulting from the project (13 plus three submitted) and their citation rate (156 citations over three years), the project has made a lasting contribution to the field. The outcome is a significant improvement of our understanding of the pickup ion production and distribution in the distant heliosphere. The team has accomplished the entire set of tasks A-H set forth in the proposal. Namely, the transport modeling framework has been augmented with two populations of pickup ions (PUIs), the boundary conditions for the plasma and interstellar neutral hydrogen were verified against Ulysses and New Horizons PUI and an optimal set of velocity diffusion parameters established. The multi-component fluxes of PUIs were computed and isotropic velocity distributions generated for each cell in the computer simulation that covered the heliosphere from 1.5 AU to the heliopause. The distributions were carefully compared with in situ measurements at 3 AU (Ulysses), 12 AU (New Horizons), and 80-90 AU (Voyager 1 and 2) as well as those inferred from ENA fluxes measured by Cassini and IBEX (Wu et al., 2016). Some examples of modeldata comparison are shown in Figure 1. We have used coupled MHD-plasma and kinetic-neutral code to investigate the likely range of plasma and magnetic field parameters in the local interstellar medium (LISM), based on the assumption that the shape of the IBEX ribbon could be used to determine the orientation of the interstellar magnetic field. While the magnetic field is believed to be oriented toward the center of the ribbon, constraining its strength requires comparing the model-predicted angular diameter and circularity of the ribbon with the observations. The study, published in Heerikhuisen et al. (2014), found that the most likely range for the LISM magnetic field strength is between 0.2 and 0.3 nT, which is less than previously thought. Figure 2 shows the IBEX data (left) and compares it to the simulation with a 0.2 nT interstellar magnetic field (center) and a 0.4 nT (right).

An overview of atmosphere and plasma observations planned for the New Horizons flyby of 2014 MU69

NASA Astrophysics Data System (ADS)

Gladstone, R.; Young, L. A.; Parker, J. W.; Elliott, H. A.; Hill, M. E.; Piquette, M. R.; Stern, A.; Weaver, H. A., Jr.; Olkin, C.; Spencer, J. R.

2017-12-01

Due to its small size, it is highly likely that all volatiles that might have once been present on 2014 MU69 are now gone, having long ago escaped to space. However, it is possible that 2014 MU69 retains some volatiles (e.g., methanol, acetylene, ethane, hydrogen cyanide, ammonia) at the present day. Although these volatiles are likely quite stable on the surface at their current temperature, ongoing radiation processing and occasional impacts provide a possible source for a transient atmosphere. Such a transient atmosphere will be searched for by the Alice ultraviolet spectrograph, e.g., in absorption, using stellar and solar appulses, and in emission, using resonantly scattered solar emissions. Dust associated with 2014 MU69 will be searched for with high phase angle LORRI and MVIC imaging, and with in situ SDC observations. In addition, the particle and plasma environment of KBOs is largely unknown. SWAP and PEPSSI observations will establish the interaction of the interplanetary medium with 2014 MU69, e.g., looking for pickup ions resulting from sputtering of surface materials. Although it is likely that only upper limits will be set on neutrals and ions in the vicinity of 2014 MU69, the New Horizons observations will characterize the fluxes of UV, solar wind, interstellar pickup ions, and energetic particles, i.e., space weathering, that can modify the surface of 2014 MU69 and other KBOs. In this presentation, we will outline the plans for New Horizons plasma and atmospheres observations during the flyby of 2014 MU69.

Physical Roles of Interstellar-origin Pickup Ions at the Heliospheric Termination Shock: Impact on the Shock Front Microstructures and Nonstationarity

NASA Astrophysics Data System (ADS)

Lembège, Bertrand; Yang, Zhongwei

2016-08-01

The nonstationary dynamics of the heliospheric termination shock in the presence of pickup ions (PUI) is analyzed by using a one-dimensional particle-in-cell simulation code. This work initially stimulated by Voyager 2 data focusses on this nonstationarity for different percentages of PUIs and for different Alfvén Mach numbers M A. Solar wind ions (SWIs) and PUIs are described, respectively, as Maxwellian and shell distributions (with a zero/finite thickness). For a moderate M A, present results show that (1) the shock front is still nonstationary even in the presence of 25% of PUIs; its instantaneous velocity varies, which is in favor for shock multicrossing; (2) the presence of PUIs tends to smooth out the time fluctuations of field amplitude and of microstructure widths at the front and overshoot; (3) the shock has a multiple overshoot, which is analyzed by identifying the contributions of SWIs and the PUIs; (4) as the PUI percentage increases, the shock moves faster and the downstream compression becomes weaker, which is explained by a Rankine-Hugoniot model; (5) the reflection rate of SWIs and PUIs decreases as the PUI percentage increases; (6) the shock structure is almost insensitive to the shell thickness and (7) for the PUIs dominated shock case (PUI = 55%), the shock becomes stationary. However, for higher M A regime, the front nonstationarity persists even in the PUI = 55% case. In summary, high M A regime allows to compensate the smoothing of the microstructures and the time fluctuations of the shock front brought by the presence of PUIs.

Mercury's magnetosphere after MESSENGER's first flyby.

PubMed

Slavin, James A; Acuña, Mario H; Anderson, Brian J; Baker, Daniel N; Benna, Mehdi; Gloeckler, George; Gold, Robert E; Ho, George C; Killen, Rosemary M; Korth, Haje; Krimigis, Stamatios M; McNutt, Ralph L; Nittler, Larry R; Raines, Jim M; Schriver, David; Solomon, Sean C; Starr, Richard D; Trávnícek, Pavel; Zurbuchen, Thomas H

2008-07-04

Observations by MESSENGER show that Mercury's magnetosphere is immersed in a comet-like cloud of planetary ions. The most abundant, Na+, is broadly distributed but exhibits flux maxima in the magnetosheath, where the local plasma flow speed is high, and near the spacecraft's closest approach, where atmospheric density should peak. The magnetic field showed reconnection signatures in the form of flux transfer events, azimuthal rotations consistent with Kelvin-Helmholtz waves along the magnetopause, and extensive ultralow-frequency wave activity. Two outbound current sheet boundaries were observed, across which the magnetic field decreased in a manner suggestive of a double magnetopause. The separation of these current layers, comparable to the gyro-radius of a Na+ pickup ion entering the magnetosphere after being accelerated in the magnetosheath, may indicate a planetary ion boundary layer.

MAVEN observations of the response of Mars to an interplanetary coronal mass ejection.

PubMed

Jakosky, B M; Grebowsky, J M; Luhmann, J G; Connerney, J; Eparvier, F; Ergun, R; Halekas, J; Larson, D; Mahaffy, P; McFadden, J; Mitchell, D F; Schneider, N; Zurek, R; Bougher, S; Brain, D; Ma, Y J; Mazelle, C; Andersson, L; Andrews, D; Baird, D; Baker, D; Bell, J M; Benna, M; Chaffin, M; Chamberlin, P; Chaufray, Y-Y; Clarke, J; Collinson, G; Combi, M; Crary, F; Cravens, T; Crismani, M; Curry, S; Curtis, D; Deighan, J; Delory, G; Dewey, R; DiBraccio, G; Dong, C; Dong, Y; Dunn, P; Elrod, M; England, S; Eriksson, A; Espley, J; Evans, S; Fang, X; Fillingim, M; Fortier, K; Fowler, C M; Fox, J; Gröller, H; Guzewich, S; Hara, T; Harada, Y; Holsclaw, G; Jain, S K; Jolitz, R; Leblanc, F; Lee, C O; Lee, Y; Lefevre, F; Lillis, R; Livi, R; Lo, D; Mayyasi, M; McClintock, W; McEnulty, T; Modolo, R; Montmessin, F; Morooka, M; Nagy, A; Olsen, K; Peterson, W; Rahmati, A; Ruhunusiri, S; Russell, C T; Sakai, S; Sauvaud, J-A; Seki, K; Steckiewicz, M; Stevens, M; Stewart, A I F; Stiepen, A; Stone, S; Tenishev, V; Thiemann, E; Tolson, R; Toublanc, D; Vogt, M; Weber, T; Withers, P; Woods, T; Yelle, R

2015-11-06

Coupling between the lower and upper atmosphere, combined with loss of gas from the upper atmosphere to space, likely contributed to the thin, cold, dry atmosphere of modern Mars. To help understand ongoing ion loss to space, the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft made comprehensive measurements of the Mars upper atmosphere, ionosphere, and interactions with the Sun and solar wind during an interplanetary coronal mass ejection impact in March 2015. Responses include changes in the bow shock and magnetosheath, formation of widespread diffuse aurora, and enhancement of pick-up ions. Observations and models both show an enhancement in escape rate of ions to space during the event. Ion loss during solar events early in Mars history may have been a major contributor to the long-term evolution of the Mars atmosphere. Copyright © 2015, American Association for the Advancement of Science.

Ionising sources in the coma of 67P probed by Rosetta

NASA Astrophysics Data System (ADS)

Heritier, Kevin; Galand, Marina; Henri, Pierre; Eriksson, Anders; Odelstad, Elias; Altwegg, Kathrin; Beth, Arnaud; Broiles, Thomas; Burch, Jim; Carr, Christopher; Cupido, Emanuele; Glassmeier, Karl-Heinz; Nilsson, Hans; Richter, Ingo; Rubin, Martin; Vallieres, Xavier; Vigren, Erik

2017-04-01

An ionospheric model has been developed in order to quantify the ion number density in the coma of 67P/Churyumov-Gerasimenko. The model is driven by Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA)/Cometary Pressure Sensor (COPS) neutral density and assumes isentropic expansion for the neutral density profile. The two ionisation sources considered are photo-ionisation by solar extreme ultraviolet (EUV) radiation and electron-impact ionisation. The EUV radiation is estimated from fluxes measured by the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED)/ Solar EUV Experiment (SEE), taking into account the phase shift and the heliocentric distance ratio; between Earth and comet 67P. The electron-impact ionisation production rates are derived from Rosetta Plasma Consortium (RPC)-Ion and Electron Sensor (IES) integrated electron fluxes and corrected for the S/C potential from RPC/LAngmuir Probe (LAP) measurements. Our results are compared with in situ measurements of the plasma density from RPC-Mutual Impedance Probe (MIP) and RPC-LAP. There is a good agreement between the modelled and RPC observed electron densities. The ionospheric model enables to distinguish the relative contributions of the different sources to the total cometary plasma. At high heliocentric distances, electron-impact ionisation becomes the dominant ionisation source and is enhanced over the winter hemisphere. As the solar activity has decreased since the beginning of the mission in 2014, the relative importance of photo-ionisation has decreased as well. However, at low heliocentric distances, photo-ionisation seems to be the most dominant ionising source, in particular through the perihelion period in summer 2015.

Interaction between solar energetic particles and interplanetary grains

NASA Astrophysics Data System (ADS)

Strazzulla, G.; Calcagno, L.; Foti, G.; Sheng, K. L.

Some laboratory-studied effects induced by the fluence of fast ions on frosts of astrophysical interest are summarized. The results are applied to the interaction between energetic solar ions and interplanetary dust grains assumed to be cometary debris which spends about one-million yr before being collected in the earth's atmosphere or colliding on the moon's surface. The importance of erosion by particles to the stability of ice grains is confirmed. The build up of carbonaceous material by ion fluence on hydrocarbon containing grains is discussed. It is suggested that these new materials could be the glue which cements submicron silicate particles to form a complex agglomeration whose density increases with increasing proton fluence (packing effect). The IR spectra of laboratory synthesized carbonaceous material are compared with those observed in some carbonaceous meteoritic extracts.

MgB2 magnetometer with a directly coupled pick-up loop

NASA Astrophysics Data System (ADS)

Portesi, C.; Mijatovic, D.; Veldhuis, D.; Brinkman, A.; Monticone, E.; Gonnelli, R. S.

2006-05-01

In this work, we show the results obtained in the fabrication and characterization of an MgB2 magnetometer with a directly coupled pick-up loop. We used an all in situ technique for fabricating magnesium diboride films, which consists of the co-evaporation of B and Mg by means of an e-gun and a resistive heater respectively. Consequently, we realized the superconducting device, which incorporates two nanobridges as weak links in a superconducting loop. The nanobridges were realized by focused ion beam milling; they were 240 nm wide and had a critical current density of 107 A cm-2. The magnetometer was characterized at different temperatures and also measurements of the noise levels have been performed. The device shows Josephson quantum interference up to 20 K and the calculated effective area at low temperatures was 0.24 mm2. The transport properties of the magnetometer allow determining fundamental materials properties of the MgB2 thin films, such as the penetration depth.

XUV-exposed, non-hydrostatic hydrogen-rich upper atmospheres of terrestrial planets. Part II: hydrogen coronae and ion escape.

PubMed

Kislyakova, Kristina G; Lammer, Helmut; Holmström, Mats; Panchenko, Mykhaylo; Odert, Petra; Erkaev, Nikolai V; Leitzinger, Martin; Khodachenko, Maxim L; Kulikov, Yuri N; Güdel, Manuel; Hanslmeier, Arnold

2013-11-01

We studied the interactions between the stellar wind plasma flow of a typical M star, such as GJ 436, and the hydrogen-rich upper atmosphere of an Earth-like planet and a "super-Earth" with a radius of 2 R(Earth) and a mass of 10 M(Earth), located within the habitable zone at ∼0.24 AU. We investigated the formation of extended atomic hydrogen coronae under the influences of the stellar XUV flux (soft X-rays and EUV), stellar wind density and velocity, shape of a planetary obstacle (e.g., magnetosphere, ionopause), and the loss of planetary pickup ions on the evolution of hydrogen-dominated upper atmospheres. Stellar XUV fluxes that are 1, 10, 50, and 100 times higher compared to that of the present-day Sun were considered, and the formation of high-energy neutral hydrogen clouds around the planets due to the charge-exchange reaction under various stellar conditions was modeled. Charge-exchange between stellar wind protons with planetary hydrogen atoms, and photoionization, lead to the production of initially cold ions of planetary origin. We found that the ion production rates for the studied planets can vary over a wide range, from ∼1.0×10²⁵ s⁻¹ to ∼5.3×10³⁰ s⁻¹, depending on the stellar wind conditions and the assumed XUV exposure of the upper atmosphere. Our findings indicate that most likely the majority of these planetary ions are picked up by the stellar wind and lost from the planet. Finally, we estimated the long-time nonthermal ion pickup escape for the studied planets and compared them with the thermal escape. According to our estimates, nonthermal escape of picked-up ionized hydrogen atoms over a planet's lifetime within the habitable zone of an M dwarf varies between ∼0.4 Earth ocean equivalent amounts of hydrogen (EO(H)) to <3 EO(H) and usually is several times smaller in comparison to the thermal atmospheric escape rates.

Correlated Microanalysis of Cometary Organic Grains Returned by Stardust

NASA Technical Reports Server (NTRS)

DeGregorio, B. T.; Stroud, R. M.; Nittler, L. R.; Cody, G. D,; Kilcoyne, A. L. D.

2011-01-01

Preliminary examination (PE) of samples returned from Comet 81P/Wild 2 by the NASA Stardust mission revealed a wide variety of carbonaceous samples [e.g. 1]. Carbonaceous matter is present as inclusions, rinds, and films in polyminerallic terminal particles [2-4], as carbon-rich particles along track walls [2, 5, 6], and as organic matter in aerogel around tracks [7, 8]. The organic chemistry of these samples ranges from purely aliphatic hydrocarbons to highly-aromatic material, often modified by various organic functional groups [2, 4, 5, 9-11]. Difficulty arises when interpreting the genesis of these carbonaceous samples, since contaminants could be introduced from the spacecraft [12], aerogel [1, 8], or during sample preparation. In addition, hypervelocity capture into aerogel may have heated cometary material in excess of 1000 C, which could have significantly altered the structure and chemistry of carbonaceous matter. Fortunately, much of this contamination or alteration can be identified through correlated microanalysis with transmission electron microscopy (TEM), scanning-transmission X-ray microscopy (STXM), and nanoscale secondary ion mass spectroscopy (SIMS).

Titan's atomic nitrogen torus - Inferred properties and consequences for the Saturnian aurora

NASA Astrophysics Data System (ADS)

Barbosa, D. D.

1987-10-01

This paper follows up the lead suggested by Barbosa and Eviatar (1986) that Titanogenic nitrogen ions are a key component of the magnetospheric particle populations and can account for the energetics of the Saturnian aurora without undue assumptions. Nitrogen atoms resulting from electron impact dissociations of N2 (Strobel and Shemansky 1982) escape from Titan and form a large doughnut-shaped ring around the satellite's orbit that is cospatial with the McDonough-Brice (1973) hydrogen cloud. Processes attendant to the ionization and pickup of nitrogen ions include the production of a warm kiloelectronvolt electron population and the excitation of the UV aurora by particle precipitation from the outer magnetosphere.

Thermal instability in the inner coma of a comet

NASA Technical Reports Server (NTRS)

Milikh, G. M.; Sharma, A. S.

1995-01-01

The spacecraft and ground based observations of comet Halley inner coma showed a localized ion density depletion region whose origin is not well understood. Although it has been linked to a thermal instability associated with negative ions, the photodetachment lifetime of negative ions (approximately 1 sec) is too short compared to the electron attachment time scale (approximately 100 sec) for this process to have a significant effect. A mechanism for the ion density depletion based on the thermal instability of the cometary plasma due to the excitation of rotational and vibrational levels of water molecules is proposed. The electron energy losses due to these processes peak near 4000 K (0.36 eV) and at temperatures higher than this value a localized cooling leads to further cooling (thermal instability) due to the increased radiation loss. The resulting increase in recombination leads to an ion density depletion and the estimates for this depletion at comet Halley agree with the observations.

In Situ Space Gas Dynamic Measurements by the ROSINA Comet Pressure Sensor COPS Onboard Rosetta Spacecraft

NASA Astrophysics Data System (ADS)

Tzou, Chia-Yu; Altwegg, Kathrin; Fiethe, Björn; Gasc, Sébastien; Rubin, Martin

2015-04-01

Rosetta is part of the cornerstone missions executed by the European Space Agency. It is the first space mission to orbit and also land on a comet. The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) is one of the core payloads on board of the Rosetta spacecraft [Balsiger et al, 2007]. ROSINA's main objective is to determine the major atmospheric and ionospheric composition in the coma and to investigate the gas dynamics around the comet. ROSINA consists of two mass spectrometers and a pressure sensor. The COmet Pressure Sensor (COPS) includes two gauges: the "nude gauge" measures total neutral density in the coma and the "ram gauge" measures the dynamic pressure of the cometary gas flux. The combination of these two gauges makes COPS capable to derive the gas dynamics (velocity and temperature) at the location of the spacecraft. Over several months Rosetta has been carrying out a close study of comet 67P/Churyumov-Gerasimenko. In early August 2014 COPS detected the faint and expanding atmosphere of the comet while it was still outside of 3.5 AU from the Sun. We will present ROSINA COPS observations of the evolution and gas dynamics of the cometary coma following these first observations until spring 2015. Reference: Balsiger, H. et al.: ROSINA-Rosetta Orbiter Spectrometer for Ion and Neutral Analysis, Space Science Reviews, Vol. 128, 745-801, 2007.

Mass-loading of the solar wind at 67P/Churyumov-Gerasimenko. Observations and modelling

NASA Astrophysics Data System (ADS)

Behar, E.; Lindkvist, J.; Nilsson, H.; Holmström, M.; Stenberg-Wieser, G.; Ramstad, R.; Götz, C.

2016-11-01

Context. The first long-term in-situ observation of the plasma environment in the vicinity of a comet, as provided by the European Rosetta spacecraft. Aims: Here we offer characterisation of the solar wind flow near 67P/Churyumov-Gerasimenko (67P) and its long term evolution during low nucleus activity. We also aim to quantify and interpret the deflection and deceleration of the flow expected from ionization of neutral cometary particles within the undisturbed solar wind. Methods: We have analysed in situ ion and magnetic field data and combined this with hybrid modeling of the interaction between the solar wind and the comet atmosphere. Results: The solar wind deflection is increasing with decreasing heliocentric distances, and exhibits very little deceleration. This is seen both in observations and in modeled solar wind protons. According to our model, energy and momentum are transferred from the solar wind to the coma in a single region, centered on the nucleus, with a size in the order of 1000 km. This interaction affects, over larger scales, the downstream modeled solar wind flow. The energy gained by the cometary ions is a small fraction of the energy available in the solar wind. Conclusions: The deflection of the solar wind is the strongest and clearest signature of the mass-loading for a small, low-activity comet, whereas there is little deceleration of the solar wind.

The forest and the trees. [comments on comet nuclei, cometary origin, and correlations among cometary data

NASA Technical Reports Server (NTRS)

Whipple, Fred L.

1991-01-01

Comments on the nature of cometary nuclei, some problems regarding cometary origin, and some correlations among cometary data are presented. Comparisons with an earlier report on cometary nuclei are noted, and most of the earlier advances in concept are substantiated. The mean density of the Halley nucleus may have been underestimated, while the nature of the rotation remains uncertain. The dust/gas ratio apparently needs to be increased by as much as two times, perhaps to unity or higher. CHON grains appear to be important sources of gas. Evidence is presented to support the thesis that aging among long-period comets increases statistically as the periods decrease. Data on the orientation of cometary axes with respect to the Galaxy and the properties of clusters defined by these axes are presented.

Planetary exploration with electrically propelled vehicles.

NASA Technical Reports Server (NTRS)

Stuhlinger, E.

1972-01-01

The characteristics of propulsion systems required for carrying out flight missions within the solar system, as desired by planetary physicists and astronomers, are reviewed. It is shown that an encouraging answer to these requirements is available in the form of electrostatic or ion propulsion systems. The design and performance characteristics of an electrostatic thrustor employing an ion source, accelerating electrode, beam neutralizer, and power source are discussed, together with those of the Kaufmann engine (electrostatic thrustor employing bombardment type ionization). More demanding missions which will become feasible with the advent of nuclear-electric power sources (such as the incore thermionic reactor) may include close orbiters around all the planets, and asteroid and cometary missions.

47 CFR 74.431 - Special rules applicable to remote pickup stations.

Code of Federal Regulations, 2010 CFR

2010-10-01

... system. (b) Remote pickup mobile or base stations may be used for communications related to production... pickup mobile or base stations may communicate with any other station licensed under this subpart. (d... additional frequency is limited to 2.5 watts. (f) Remote pickup base and mobile stations in Alaska, Guam...

PICKUP Wales, U.K. Assurance of Quality Vocational Continuing Education and Training.

ERIC Educational Resources Information Center

Daniels, C. E. J.

The Professional, Industrial, and Commercial Updating Programme (PICKUP) of the United Kingdom is aimed at improving the performance of British industry through the colleges. In Wales, PICKUP is part of the Welsh Office Education Department. Various factors have encouraged educational institutions to take on PICKUP work: the Education Reform Act…

A statistical study of ions and magnetic fields in the Venus magnetotail

NASA Technical Reports Server (NTRS)

Moore, K. R.; Mccomas, D. J.; Russell, C. T.; Mihalov, J. D.

1990-01-01

A statistical characterization is made of the combined ion and magnetic field properties of the Venus magnetosheath and magnetotail, on the basis of plasma and magnetic field data from 223 Pioneer Venus orbits; no assumptions are made as to existing regions or their plasma and field characteristics. Plasma is found to flow tailward in all locations, and the magnetotail is highly draped. Weak magnetic field asymmetries are associated with the plasma dropouts. A high-E/q plasma population, previously interpreted as planetary-pickup ions, is found asymmetrically both within the tail and in the adjacent sheath. The Venus tail is filled with plasma that is primarily shocked solar wind, at fluxes that are sometimes undetectable; the tail coexists with a photoion population which generates asymmetries in the bulk plasma and magnetic field properties.

Three-Dimensional Magnetohydrodynamic Modeling of the Solar Wind Including Pickup Protons and Turbulence Transport

NASA Technical Reports Server (NTRS)

Usmanov, Arcadi V.; Goldstein, Melvyn L.; Matthaeus, William H.

2012-01-01

To study the effects of interstellar pickup protons and turbulence on the structure and dynamics of the solar wind, we have developed a fully three-dimensional magnetohydrodynamic solar wind model that treats interstellar pickup protons as a separate fluid and incorporates the transport of turbulence and turbulent heating. The governing system of equations combines the mean-field equations for the solar wind plasma, magnetic field, and pickup protons and the turbulence transport equations for the turbulent energy, normalized cross-helicity, and correlation length. The model equations account for photoionization of interstellar hydrogen atoms and their charge exchange with solar wind protons, energy transfer from pickup protons to solar wind protons, and plasma heating by turbulent dissipation. Separate mass and energy equations are used for the solar wind and pickup protons, though a single momentum equation is employed under the assumption that the pickup protons are comoving with the solar wind protons.We compute the global structure of the solar wind plasma, magnetic field, and turbulence in the region from 0.3 to 100 AU for a source magnetic dipole on the Sun tilted by 0 deg - .90 deg and compare our results with Voyager 2 observations. The results computed with and without pickup protons are superposed to evaluate quantitatively the deceleration and heating effects of pickup protons, the overall compression of the magnetic field in the outer heliosphere caused by deceleration, and the weakening of corotating interaction regions by the thermal pressure of pickup protons.

Measurements of H(+), He(2+), and He(+), in Corotating Interaction Regions at 1 AU

NASA Astrophysics Data System (ADS)

Chotoo, Kancham

Using the Supra-Thermal Ion Composition Spectrometer (STICS) from the SMS experiment on the WIND spacecraft, measurements of H+, He2+, and He+ were made during two corotating interacting regions (CIRs) at 1 AU. The unique energy range of STICS (6-198 keV/e) allowed simultaneous observation of the pre- and post-accelerated ions. These observations gave important clues about the source population, injection, acceleration mechanism, and ion transport in CIRs. The abundance of He2+ relative to H+ in the velocity range 2.5-6.0 times the solar wind velocity, VSW, (5-90 keV/amu) was between 0.11-0.18, which is more than double the solar wind values. However, the same ratio was observed in the suprathermal tail above 1.4 VSW in the spacecraft frame or above ~0.4 VSW in the solar wind frame. This suggests that the H+ and He2+ ions are injected equally into the CIR acceleration process from the suprathermal tail of the solar wind. At 1 AU the H+ and He2+ ions are primarily from the solar wind, but the He+ ions are interstellar pickup ions. The He+/He2+ ratio at 1 AU was ~0.15 for the same velocity range as above. However, this ratio was greater than 1.0 at 4.5 AU as measured previously (Gloeckler et al., 1994). This shows that the relative contribution of the pickup He+ ions to the seed population increases with radial distance away from the Sun. By combining data from three separate sensors on WIND (SMS-MASS, SMS-STICS, and EPACT-STEP), the extended helium distribution was presented for solar wind ions (~1 keV/amu) through energetic particles up to ~1 MeV/amu. The distribution covered 14 orders of magnitude in phase space density. This is the first time such an extended helium distribution is being reported at any radial distance. Using the Fisk and Lee (1980) model to fit the data between ~10-1000 keV/amu, the energetic particles were found to originate from 1.0-1.2 AU and not from beyond 2 AU, as is conventional believed. Anisotropy measurements were made using STICS for both the H+ and He2+ ions in the solar wind frame, and the results were compared to those made by EPACT-STEP. For both time intervals, the anisotropy directions showed significant deviations away from the average magnetic field direction in agreement with the STEP observations of Dwyer et al. (1997).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mazarakis, Michael G.; Kiefer, Mark L.; Leckbee, Joshua J.

This paper describes our effort to measure the back-streaming ions emitted from the target x-ray convertor and thus estimate the ion contribution to the A-K gap bipolar current flow. Knowing the ion contribution is quite important in order to calculate the expected x-ray dose and compare it with the actual measurements. Our plans were first to measure the total ion current using B-dot monitors, Rogowski coils, and Faraday cups and then to utilize filtered Faraday cups and time of flight techniques to identify and measure the various ionic species. The kinetic energy (velocities) of the ions should help evaluate themore » actual voltage applied at the anode-cathode (A-K) gap. LSP simulations found that the most prominent ions are protons and carbon single plus (C+). For an 8-MV A-K voltage, the estimated proton current back-streaming through an 1 cm in diameter hollow cathode tip was on the average 3 kA and the carbon current 0.7 kA. Since only a small fraction of the ions will make it through the cylindrical aperture, the corresponding total currents were calculated to be respectively 25kA for proton and 7 kA for carbon ions, a quite substantial contribution to the total bipolar beam current. Hence, approximately only 10% of the total back-streaming ionic currents could make it through the hollow cathode tip aperture. Unfortunately the diagnostic cables connecting the Faraday cup and the B-dot monitors to the screen room scopes experienced a large amount of charge pick-up that obliterated our effort to directly measure those relatively small currents. However, we succeeded in measuring those currents indirectly with activation techniques [Contribution of the back-streaming ions to the self-magnetic pinch (SMP) diode Current., M. G. Mazarakis, M. G. Mazarakis, M. E. Cuneo, S. D. Fournier, M. D. Johnston, M. L. Kiefer, J. J. Leckbee, D. S. Nielsen, B.V.Oliver, M. E. Sceiford, S. C. Simpson, T. J. Renk, C. L. Ruiz, T. J. Webb, and D. Ziska. Subitted for publication.]. In the following sections we present some typical cable pick-up results and also our efforts to verify that the observed “current” scope traces were indeed not ion currents but instead cable charge pic-up. Interestingly enough we also discovered that the appearance of those “currents” are in synchronism with the A-K gap impedance variation (decrease) and the MITL sheath current re-trapping. Hence those B-dots or Faraday cups could be utilized as diode behavior diagnostics.« less

Will the light truck bumper height-matching standard reduce deaths in cars?

PubMed

Ossiander, Eric M; Koepsell, Thomas D; McKnight, Barbara

2013-03-01

In a collision between a car and a sport utility vehicle (SUV) or pickup truck, car occupants are more likely to be killed than if they crashed with another car. Some of the excess risk may be due to the propensity of SUVs and pickups with high bumpers to override the lower bumpers in cars. To reduce this incompatibility, particularly in head-on collisions, in 2003 automobile manufacturers voluntarily established a bumper height-matching standard for pickups and SUVs. To assess whether height-matching bumpers in pickups and SUVs were associated with the risk of death in either car occupants or pickup and SUV occupants. Case-control study of collisions between one car and one SUV or pickup in the US during 2000-2008, in which the SUV or pickup was model year 2000-2006. Cases were all decedents in fatal crashes; one control was selected from each crash in a national probability sample of crashes. Occupants of cars that crashed with SUVs or pickups with height-matching bumpers may be at slightly reduced risk of death compared to those that crashed with other SUVs or pickups (adjusted odds ratio: 0.83 (95% confidence interval 0.61-1.13)). There was no evidence of a reduction in risk in head-on crashes (1.09 (0.66-1.79)). In crashes in which the SUV or pickup struck the car on the side, height-matched bumpers were associated with a reduced risk of death (0.68 (0.48-0.97)). Occupants of SUVs and pickups with height-matching bumpers may also be at slightly reduced risk of death (0.91 (0.64-1.28)). Height-matching bumpers were associated with a reduced risk of death among car occupants in crashes in which SUVs or pickups struck cars in the side, but there was little evidence of an effect in head-on crashes. The new bumper height-matching standard may not achieve its primary goal of reducing deaths in head-on crashes, but may modestly reduce overall deaths in crashes between cars and SUVs or pickups because of unanticipated benefits to car occupants in side crashes, and a possible beneficial effect to SUV and pickup occupants. Copyright © 2012 Elsevier Ltd. All rights reserved.

Laboratory investigations

NASA Technical Reports Server (NTRS)

Russell, Ray W.

1988-01-01

Laboratory studies related to cometary grains and the nuclei of comets can be broken down into three areas which relate to understanding the spectral properties, the formation mechanisms, and the evolution of grains and nuclei: (1) Spectral studies to be used in the interpretation of cometary spectra; (2) Sample preparation experiments which may shed light on the physical nature and history of cometary grains and nuclei by exploring the effects on grain emissivities resulting from the ways in which the samples are created; and (3) Grain processing experiments which should provide insight on the interaction of cometary grains with the environment in the immediate vicinity of the cometary nucleus as the comet travels from the Oort cloud through perihelion, and perhaps even suggestions regarding the relationship between interstellar grains and cometary matter. A summary is presented with a different view of lab experiments than is found in the literature, concentrating on measurement techniques and sample preparations especially relevant to cometary dust.

Ultra Compact Optical Pickup with Integrated Optical System

NASA Astrophysics Data System (ADS)

Nakata, Hideki; Nagata, Takayuki; Tomita, Hironori

2006-08-01

Smaller and thinner optical pickups are needed for portable audio-visual (AV) products and notebook personal computers (PCs). We have newly developed an ultra compact recordable optical pickup for Mini Disc (MD) that measures less than 4 mm from the disc surface to the bottom of the optical pickup, making the optical system markedly compact. We have integrated all the optical components into an objective lens actuator moving unit, while fully satisfying recording and playback performance requirements. In this paper, we propose an ultra compact optical pickup applicable to portable MD recorders.

Pickup ion processes associated with spacecraft thrusters: Implications for solar probe plus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clemens, Adam, E-mail: a.j.clemens@qmul.ac.uk; Burgess, David

2016-03-15

Chemical thrusters are widely used in spacecraft for attitude control and orbital manoeuvres. They create an exhaust plume of neutral gas which produces ions via photoionization and charge exchange. Measurements of local plasma properties will be affected by perturbations caused by the coupling between the newborn ions and the plasma. A model of neutral expansion has been used in conjunction with a fully three-dimensional hybrid code to study the evolution and ionization over time of the neutral cloud produced by the firing of a mono-propellant hydrazine thruster as well as the interactions of the resulting ion cloud with the ambientmore » solar wind. Results are presented which show that the plasma in the region near to the spacecraft will be perturbed for an extended period of time with the formation of an interaction region around the spacecraft, a moderate amplitude density bow wave bounding the interaction region and evidence of an instability at the forefront of the interaction region which causes clumps of ions to be ejected from the main ion cloud quasi-periodically.« less

Verification Test of Jet Industries Electra-Van 1000P,

DTIC Science & Technology

1980-10-01

Assistant Secretary for Conservation and Solar Ene ion of Electric Unclassified and Hybrid Vehicles 15 I Ia. DEL S FCATIOt OWNGRADING 16. DISTRIBUTION...Propulsion Batteries Charger 24. AUSTRACT (C m ern.. Fev neeey aid Idenify by block nmtbe) - The Je 4nfduis&ieElectra-Van IOOOP is a Chrysler Corp. pickup...Electric EV -1 SCR Controller (Figure 5). The propulsion motor is a General Electric d.c. motor, 37-hp, series-wound, rated at 2039 r/min. The 1000P has a

Evolution of the coma composition at 67P/Churyumov-Gerasimenko as seen by ROSINA/Rosetta from November 2014 to April 2015

NASA Astrophysics Data System (ADS)

Gasc, Sébastien; Altwegg, Kathrin; Balsiger, Hans; Calmonte, Ursina; Galli, André; Jäckel, Annette; Le Roy, Léna; Rubin, Martin; Tzou, Chia-Yu; Wurz, Peter; Berthelier, Jean-Jacques; Fiethe, Björn; Fuselier, Stephen; Gombosi, Tamas; De Keyser, Johan; Mall, Urs; Rème, Henri

2015-04-01

The European Space Agency's Rosetta spacecraft, with the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) onboard [1], has been following and observing comet 67P/Churyumov-Gerasimenko (67P/C-G) since August 2014. ROSINA has provided new information on the molecular, elemental, and isotopic composition of 67P/C-G's coma [2,3]. ROSINA consists of a pressure sensor (COPS) and two mass spectrometers, the Double Focusing Mass Spectrometer (DFMS) and the Reflectron Time Of Flight mass spectrometer (RTOF). DFMS has a high mass resolution (ca. 3'000 at 1%) and a high sensitivity, whereas RTOF has a wide mass range (from 1 amu/e to >300 amu/e) and a high temporal resolution. Both mass spectrometers are designed to measure cometary neutral gas as well as cometary ions. In this work, we present the first results and discuss the evolution of the composition of the coma measured by ROSINA from November 2014 until the end of March 2015. During this period, Rosetta delivered the lander, then stayed in bound orbits at distances of 20-30 km away from the comet center, and finally performed comet flybys from 10 km up to 250 km away from 67P/C-G. [1] Balsiger, H. et al.: ROSINA-Rosetta Orbiter Spectrometer for Ion and Neutral Analysis, Space Science Reviews, Vol. 128, 745-801, 2007 [2] Altwegg, K. et al.: Comet 67P/Churyumov-Gerasimenko, a true Kuiper belt comet as judged from its D/H in water, Science Express, 2014 [3] Hässig, M. et al.: Time variability and heterogeneity in the coma of 67P/Churyumov-Gerasimenko, Science, in press, 2015

Electron Microscopy Studies of Comet Wild-2 Particulate Residue Preserved in the Stardust Metallic Foil Craters

NASA Astrophysics Data System (ADS)

Graham, G. A.; Kearsley, A. T.; Dai, Z.; Leroux, H.; Teslich, N. E.; Stroud, R.; Borg, J.; Bradley, J. P.; Horz, F. P.; Zolensky, M.

2006-12-01

The study of comets is fundamental to the understanding of early solar system processes. Much of the current knowledge of cometary compositions comes from `fly-by' missions or remote sensing studies but not, until now, from the laboratory analyses of samples. The Stardust spacecraft (NASA's 4th Discovery mission) was launched in 1999 and in January 2004 had a successful fly-by close to the nucleus of comet Wild 2. During the encounter, the collector tray assembly containing the principle particle capture technology of low- density silica aerogel was deployed. In addition, the metallic foils (1100 series Aluminum) wrapped around the collector frame also picked up material from the 6.1 km/s cometary particle collisions. Since the retrieval of the sample return capsule in January 2006, and as part of the preliminary examination, a selected number of foils have been scanned using SEM-EDX to locate cometary dust derived impact craters. Craters ranging from 100 nanometers to several hundreds of micrometers in diameter, containing both monomineralic and polymineralic projectile melts, have been identified, measured and analyzed. Focused ion beam microscopy techniques have been used to take cross-section slices of either individual craters or specific residue fragments, and thin them to electron transparency. TEM-EDX analysis of these slices shows that crystalline grains are occasionally preserved, despite the high shock pressures and temperatures that caused most of the particle to melt. Observations from the crater residues make a useful addition to studies of the composition and mineralogy of the cometary particulates preserved within the impact tracks in the silica aerogel. This work was in part performed under the auspices of the U.S. Department of Energy, National Nuclear Security Administration by the University of California, Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

Pre-cometary ice composition from hot core chemistry.

PubMed

Tornow, Carmen; Kührt, Ekkehard; Motschmann, Uwe

2005-10-01

Pre-cometary ice located around star-forming regions contains molecules that are pre-biotic compounds or pre-biotic precursors. Molecular line surveys of hot cores provide information on the composition of the ice since it sublimates near these sites. We have combined a hydrostatic hot core model with a complex network of chemical reactions to calculate the time-dependent abundances of molecules, ions, and radicals. The model considers the interaction between the ice and gas phase. It is applied to the Orion hot core where high-mass star formation occurs, and to the solar-mass binary protostar system IRAS 16293-2422. Our calculations show that at the end of the hot core phase both star-forming sites produce the same prebiotic CN-bearing molecules. However, in the Orion hot core these molecules are formed in larger abundances. A comparison of the calculated values with the abundances derived from the observed line data requires a chemically unprocessed molecular cloud as the initial state of hot core evolution. Thus, it appears that these objects are formed at a much younger cloud stage than previously thought. This implies that the ice phase of the young clouds does not contain CN-bearing molecules in large abundances before the hot core has been formed. The pre-biotic molecules synthesized in hot cores cause a chemical enrichment in the gas phase and in the pre-cometary ice. This enrichment is thought to be an important extraterrestrial aspect of the formation of life on Earth and elsewhere.

The Time-Dependent Chemistry of Cometary Debris in the Solar Corona

NASA Technical Reports Server (NTRS)

Pesnell, W. D.; Bryans, P.

2015-01-01

Recent improvements in solar observations have greatly progressed the study of sungrazing comets. They can now be imaged along the entirety of their perihelion passage through the solar atmosphere, revealing details of their composition and structure not measurable through previous observations in the less volatile region of the orbit further from the solar surface. Such comets are also unique probes of the solar atmosphere. The debris deposited by sungrazers is rapidly ionized and subsequently influenced by the ambient magnetic field. Measuring the spectral signature of the deposited material highlights the topology of the magnetic field and can reveal plasma parameters such as the electron temperature and density. Recovering these variables from the observable data requires a model of the interaction of the cometary species with the atmosphere through which they pass. The present paper offers such a model by considering the time-dependent chemistry of sublimated cometary species as they interact with the solar radiation field and coronal plasma. We expand on a previous simplified model by considering the fully time-dependent solutions of the emitting species' densities. To compare with observations, we consider a spherically symmetric expansion of the sublimated material into the corona and convert the time-dependent ion densities to radial profiles. Using emissivities from the CHIANTI database and plasma parameters derived from a magnetohydrodynamic simulation leads to a spatially dependent emission spectrum that can be directly compared with observations. We find our simulated spectra to be consistent with observation.

THREE-DIMENSIONAL MAGNETOHYDRODYNAMIC MODELING OF THE SOLAR WIND INCLUDING PICKUP PROTONS AND TURBULENCE TRANSPORT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Usmanov, Arcadi V.; Matthaeus, William H.; Goldstein, Melvyn L., E-mail: arcadi.usmanov@nasa.gov

2012-07-20

To study the effects of interstellar pickup protons and turbulence on the structure and dynamics of the solar wind, we have developed a fully three-dimensional magnetohydrodynamic solar wind model that treats interstellar pickup protons as a separate fluid and incorporates the transport of turbulence and turbulent heating. The governing system of equations combines the mean-field equations for the solar wind plasma, magnetic field, and pickup protons and the turbulence transport equations for the turbulent energy, normalized cross-helicity, and correlation length. The model equations account for photoionization of interstellar hydrogen atoms and their charge exchange with solar wind protons, energy transfermore » from pickup protons to solar wind protons, and plasma heating by turbulent dissipation. Separate mass and energy equations are used for the solar wind and pickup protons, though a single momentum equation is employed under the assumption that the pickup protons are comoving with the solar wind protons. We compute the global structure of the solar wind plasma, magnetic field, and turbulence in the region from 0.3 to 100 AU for a source magnetic dipole on the Sun tilted by 0 Degree-Sign -90 Degree-Sign and compare our results with Voyager 2 observations. The results computed with and without pickup protons are superposed to evaluate quantitatively the deceleration and heating effects of pickup protons, the overall compression of the magnetic field in the outer heliosphere caused by deceleration, and the weakening of corotating interaction regions by the thermal pressure of pickup protons.« less

Mission strategy for cometary exploration in the 1980's

NASA Technical Reports Server (NTRS)

Farquhar, R. W.

1976-01-01

A specific plan for a sequence of cometary intercept missions in the 1980's is reported. Each mission is described in detail and the supporting role of ground based cometary observations is included. Only three launches are required in the proposed mission sequence for six cometary encounters with comets Encke, Giacobini-Zinner, Borrelly and Halley. Cometary ephemerics errors are reduced to very small values because of a favorable earth-comet orbital geometry for Encke 1980, and excellent earth based sighting conditions exist for the entire 1985 mission set.

Could life have evolved in cometary nuclei

NASA Technical Reports Server (NTRS)

Bar-Nun, A.; Lazcano-Araujo, A.; Oro, J.

1981-01-01

The suggestion by Hoyle and Wickramasinghe (1978) that life might have originated in cometary nuclei rather than directly on the earth is discussed. Factors in the cometary environment including the conditions at perihelion passage leading to the ablation of cometary ices, ice temperatures, the absence of an atmosphere and discrete liquid and solid surfaces, weak cometary structure incapable of supporting a liquid core, and radiation are presented as arguments against biopoesis in comets. It is concluded that although the contribution of cometary and meteoritic matter was significant in shaping the earth environment, the view that life on earth originally arose in comets is untenable, and the proposition that the process of interplanetary infection still occurs is unlikely in view of the high specificity of host-parasite relationships.

Chemistry in cometary comae

NASA Technical Reports Server (NTRS)

Irvine, W. M.; Dickens, J. E.; Lovell, A. J.; Schloerb, F. P.; Senay, M.; Bergin, E. A.; Jewitt, D.; Matthews, H. E.

1998-01-01

Significant gas-phase chemistry occurs in the comae of bright comets, as is demonstrated here for the case of Comet Hale-Bopp. The abundance ratio of the two isomers, hydrogen cyanide and hydrogen isocyanide, is shown to vary with heliocentric distance in a way that is consistent with production of HNC by ion-molecule chemistry initiated by the photoionization of water. Likewise, the first maps of emission from HCO+ show an abundance and an extended distribution that are consistent with the same chemical model.

Are cometary nuclei primordial rubble piles?

NASA Technical Reports Server (NTRS)

Weissman, P. R.

1986-01-01

Whipple's icy conglomerate model for the cometary nucleus has had considerable sucess in explaining a variety of cometary phenomena such as gas production rates and nongravitational forces. However, as discussed here, both observational evidence and theoretical considerations suggest that the cometary nucleus may not be a well-consolidated single body, but may instead be a loosely bound agglomeration of smaller fragments, weakly bonded and subject to occasional or even frequent disruptive events. The proposed model is analogous to the 'rubble pile' model suggested for the larger main-belt asteroids, although the larger cometary fragments are expected to be primordial condensations rather than collisionally derived debris as in the asteroid case. The concept of cometary nuclei as primordial rubble piles is proposed as a modification of the basic Whipple model, not as a replacement for it.

Transverse particle acceleration and diffusion in a planetary magnetic field

NASA Technical Reports Server (NTRS)

Barbosa, D. D.

1994-01-01

A general model of particle acceleration by plasma waves coupled with adiabatic radial diffusion in a planetary magnetic field is developed. The model assumes that a spectrum of lower hybird waves is present to resonantly accelerate ions transverse to the magnetic field. The steady state Green's function for the combined radial diffusion and wave acceleration equation is found in terms of a series expansion. The results provide a rigorous demonstration of how a quasi-Maxwellian distribution function is formed in the absence of particle collisons and elucidate the nature of turbulent heating of magnetospheric plasmas. The solution is applied to the magnetosphere of Neptune for which a number of examples are given illustrating how the spectrum of pickup N(+) ions from Triton evolves.

Mars atmospheric losses induced by the solar wind: current knowledge and perspective

NASA Astrophysics Data System (ADS)

Ermakov, Vladimir; Zelenyi, Lev; Vaisberg, Oleg; Sementsov, Egor; Dubinin, Eduard

2017-04-01

Solar wind induced atmospheric losses have been studied since earlier 1970th. Several loss channels have been identified including pick-up of exospheric photo-ions and ionospheric ions escape. Measurements performed during several solar cycles showed variation of these losses by about factor of 10, being largest at maximum solar activity. MAVEN spacecraft equipped with comprehensive set of instruments with high temporal and mass resolution operating at Mars since fall 2014 ensures much better investigation of solar wind enforcing Martian environment, Mars atmospheric losses processes and mass loss rate. These issues are very important for understanding of Martian atmospheric evolution including water loss during cosmogonic time. Simultaneous observations by MAVEN and MEX spacecraft open the new perspective in study of Martian environment. In this report we discuss results of past and current missions and preliminary analysis of heavy ions escape using simultaneous measurements of MEX and MAVEN spacecraft.

Ion cyclotron emission from energetic fusion products in tokamak plasmas: A full-wave calculation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Batchelor, D.B.; Jaeger, E.F.; Colestock, P.L.

1989-06-01

A full-wave ion cyclotron resonant heating (ICRH) code has been modified to allow calculation of cyclotron emission from energetic ions in tokamaks. The immediate application is to fusion alpha particles in near-ignition devices. This permits detailed evaluation of proposed alpha particle diagnostics (Proceedings of the Thirteenth European Conference on Controlled Fusion and Plasma Heating, Schliersee, Federal Republic of Germany, 1986, edited by G. Briffod and M. Kaufmann (European Physical Society, Petit-Lancy, Switzerland, 1986), Part 1, Vol. 2, p. 37.) This full-wave approach automatically takes into account wall reflections, standing waves, and plasma absorption and overcomes the difficulties inherent in attemptingmore » to apply conventional geometrical optics to long wavelengths. By calculating the coherent radiation field caused by an ensemble of localized current sources (and retaining the phase information), the directivity of pickup antennas is correctly represented.« less

The Interaction Between the Magnetosphere of Mars and that of Comet Siding Spring

NASA Astrophysics Data System (ADS)

Holmstrom, M.; Futaana, Y.; Barabash, S. V.

2015-12-01

On 19 October 2014 the comet Siding Spring flew by Mars. This was a unique opportunity to study the interaction between a cometary and a planetary magnetosphere. Here we model the magnetosphere of the comet using a hybrid plasma solver (ions as particles, electrons as a fluid). The undisturbed upstream solar wind ion conditions are estimated from observations by ASPERA-3/IMA on Mars Express during several orbits. It is found that Mars probably passed through a solar wind that was disturbed by the comet during the flyby. The uncertainty derives from that the size of the disturbed solar wind region in the comet simulation is sensitive to the assumed upstream solar wind conditions, especially the solar wind proton density.

Steepened magnetosonic waves in the high beta plasma surrounding Comet Giacobini-Zinner

NASA Technical Reports Server (NTRS)

Tsurutani, B. T.; Smith, E. J.; Thorne, R. M.; Gosling, J. T.; Matsumoto, H.

1986-01-01

Studies of intense hydromagnetic waves at Giacobini-Zinner are extended to investigate the mode and direction of wave propagation. Simultaneous high-resolution measurements of electron density fluctuations demonstrate that long period waves propagate in the magnetosonic mode. Principal axis analyses of the long period waves and accompanying partial rotations show that the sum of the wave phase rotations is 360 deg, indicating that both are parts of the same wave oscillation. The time sequence of the steepened waveforms observed by ICE shows that the waves must propagate towards the Sun with Cph less than Vsw. Observations are consistent with wave generation by resonant ion ring or ion beam instability which predicts right-hand polarized waves propagating in the ion beam (solar) direction. The large amplitudes and small scale sizes of the cometary waves suggest that rapid pitch-angle scattering and energy transfer with energetic ions should occur. Since the waves are highly compressive, first-order Fermi acceleration is forecast.

A study of ion composition and dynamics at Comet Halley

NASA Technical Reports Server (NTRS)

Shelley, E. G.; Fuselier, S. A.

1991-01-01

This report details the participation by Lockheed co-investigators in the reduction, analysis, and interpretation of data obtained by the Ion Mass Spectrometer onboard the Giotto mission to Comet Halley. The data analysis activities and much of the scientific collaboration was shared by this team. One objective of the effort under this contract was to use data obtained by the Giotto Ion Mass Spectrometer (IMS) during the encounter with comet Halley for the purpose of advancing our understanding of the chemistry and physics of the interaction of the solar wind with comets and obtaining new information on the comet's composition. An additional objective was to make this unique data set available in a format which can be easily used by the reset of the cometary science community for other analysis in the future. The IMS has two sensors: the High Intensity Spectrometer (HIS) and the High Energy Range Spectrometer (HERS).

Changes In the Pickup Ion Cutoff Under Variable Solar Wind Conditions

NASA Astrophysics Data System (ADS)

Bower, J.; Moebius, E.; Taut, A.; Berger, L.; Drews, C.; Lee, M. A.; Farrugia, C. J.

2017-12-01

We present the first systematic analysis to determine pickup ion (PUI) cutoff speed variations,both during compression regions, identified by their structure, and during times of highly variablesolar wind (SW) speed or magnetic field strength. This study is motivated by the attempt toremove or correct these effects on the determination of the longitude of the interstellar neutralgas flow from the flow pattern related variation of the PUI cutoff with ecliptic longitude. At thesame time, this study sheds light on the physical mechanisms that lead to energy transferbetween the SW and the embedded PUI population. Using 2007-2014 STEREO A PLASTICobservations we identify compression regions in the solar wind and analyze the PUI velocitydistribution function (VDF). We developed a routine to identify stream interaction regions andCIRs, by identifying the stream interface and the successive velocity increase in the solar windspeed and density. Characterizing these individual compression events and combining them in asuperposed epoch analysis allows us to analyze the PUI population in similar conditions andfind the local cutoff shift with adequate statistics. The result of this method yields cutoff shifts forcompression regions with large solar wind speed gradients. Additionally, through sorting theentire set of PUI VDFs at high time resolution we obtain a noticeable correlation of the cutoffshift with gradients in the SW speed and interplanetary magnetic field strength. We willdiscuss implications for the understanding of the PUI VDF evolution and the PUI cutoff analysisof the interstellar gas flow.

The role of cross-shock potential on pickup ion shock acceleration in the framework of focused transport theory

DOE PAGES

Zuo, Pingbing; Zhang, Ming; Rassoul, Hamid K.

2013-10-03

The focused transport theory is appropriate to describe the injection and acceleration of low-energy particles at shocks as an extension of diffusive shock acceleration (DSA). In this investigation, we aim to characterize the role of cross-shock potential (CSP) originated in the charge separation across the shock ramp on pickup ion (PUI) acceleration at various types of shocks with a focused transport model. The simulation results of energy spectrum and spatial density distribution for the cases with and without CSP added in the model are compared. With sufficient acceleration time, the focused transport acceleration finally falls into the DSA regime withmore » the power-law spectral index equal to the solution of the DSA theory. The CSP can affect the shape of the spectrum segment at lower energies, but it does not change the spectral index of the final power-law spectrum at high energies. It is found that the CSP controls the injection efficiency which is the fraction of PUIs reaching the DSA regime. A stronger CSP jump results in a dramatically improved injection efficiency. Our simulation results also show that the injection efficiency of PUIs is mass-dependent, which is lower for species with a higher mass. Additionally, the CSP is able to enhance the particle reflection upstream to produce a stronger intensity spike at the shock front. Lastly, we conclude that the CSP is a non-negligible factor that affects the dynamics of PUIs at shocks.« less

3-D Hybrid Kinetic Modeling of the Interaction Between the Solar Wind and Lunar-like Exospheric Pickup Ions in Case of Oblique/ Quasi-Parallel/Parallel Upstream Magnetic Field

NASA Technical Reports Server (NTRS)

Lipatov, A. S.; Farrell, W. M.; Cooper, J. F.; Sittler, E. C., Jr.; Hartle, R. E.

2015-01-01

The interactions between the solar wind and Moon-sized objects are determined by a set of the solar wind parameters and plasma environment of the space objects. The orientation of upstream magnetic field is one of the key factors which determines the formation and structure of bow shock wave/Mach cone or Alfven wing near the obstacle. The study of effects of the direction of the upstream magnetic field on lunar-like plasma environment is the main subject of our investigation in this paper. Photoionization, electron-impact ionization and charge exchange are included in our hybrid model. The computational model includes the self-consistent dynamics of the light (hydrogen (+), helium (+)) and heavy (sodium (+)) pickup ions. The lunar interior is considered as a weakly conducting body. Our previous 2013 lunar work, as reported in this journal, found formation of a triple structure of the Mach cone near the Moon in the case of perpendicular upstream magnetic field. Further advances in modeling now reveal the presence of strong wave activity in the upstream solar wind and plasma wake in the cases of quasiparallel and parallel upstream magnetic fields. However, little wave activity is found for the opposite case with a perpendicular upstream magnetic field. The modeling does not show a formation of the Mach cone in the case of theta(Sub B,U) approximately equal to 0 degrees.

Chemical Recycling of HCN in Cometary Comae

NASA Astrophysics Data System (ADS)

Boice, Daniel C.; Kawakita, Hideyo; Shinnaka, Yoshiharu; Mumma, Michael J.; Kobayashi, Hitomi; Ogawa, Sayuri

2014-11-01

Modeling is essential to understand the important physical and chemical processes that occur in cometary comae, especially the relationship between putative parent and daughter molecules, such as, HCN and CN. Photochemistry is a major source of ions and electrons that further initiate key gas-phase reactions, contributing to the plethora of molecules and atoms observed in comets. The effects of photoelectrons that interact via impacts are important to the overall excitation and dissociation processes in the inner coma. We consider the relevant processes in the collision-dominated, inner coma of a comet within a global modeling framework to understand observations of HCN and CN. The CN source(s) must be able to produce highly collimated jets, be consistent with the observed CN parent scale length, and have a production rate consistent with the observed CN production. HCN fulfills these conditions in some comets (e.g., 1P/Halley, Hale-Bopp) while it does not in others (e.g., 8P/Tuttle, 6P/d’Arrest, 73P/S-W3, 2P/Encke, 9P/Temple 1 and C/2007 W1).We investigate the chemistry of HCN with our chemical kinetics coma model including a network with other possible CN parents, as well as a dust component that may be a potential source of CN. It is seen that the major destruction pathways of HCN are via photo dissociation (into H and CN) and protonation with water group ions - primarily H3O+. We point out the intriguing “recycling” of HCN via protonation reactions with H3O+, H2O+, OH+, and subsequent dissociative recombination. It seems that HCN molecules observed in the coma can consist of those initially released from the nucleus and those that are freshly formed at different locations in the coma via these protonation/dissociation reactions. We will investigate implications for reconciling discrepancies between observations of HCN and CN in cometary comae.Acknowledgements: We appreciate support from the NSF Planetary Astronomy Program. This program is partially supported by the MEXT Supported Program for the Strategic Research Foundation at Private Universities, 2014-2018.

Theory and observations of electromagnetic ion cyclotron waves in Saturn's inner magnetosphere

NASA Technical Reports Server (NTRS)

Barbosa, D. D.

1993-01-01

High-resolution Voyager 1 magnetic field observations of Saturn's inner magnetosphere are examined for the presence of ULF waves. Quasi-circular left-hand polarized transverse oscillations are found in the near-equatorial region of 5-7 Rs with a wave period about 10 s and peak amplitude of about 2 nT. The wave is identified as the electromagnetic oxygen cyclotron mode occurring at a frequency just below the O(+) ion cyclotron frequency. A theoretical model of wave excitation based on gyroresonant coupling through a temperature anisotropy of O(+) pickup ions is developed which accounts for the principal features of the wave spectrum. It is hypothesized that wave-particle interactions provide a level of scattering commensurate with the weak pitch angle diffusion regime but nonetheless one that regulates and maintains a constant thermal anisotropy of ions along the magnetic field. Arguments are also presented that O(+) was the dominant thermal ion of the Dione-Tethys plasma torus at the time of the Pioneer 11 encounter the year previous to the Voyager 1 measurements.

Multi-species analysis of ion distributions at Mars

NASA Astrophysics Data System (ADS)

Curry, S.; Liemohn, M. W.; Fang, X.; Ma, Y.; Johnson, B.; Bougher, S. W.; Dong, C.

2012-12-01

This study focuses on using the Mars Test Particle simulation to compare observations with virtual detections of O+, O2+, CO2+, and H+ in an orbital configuration in the Mars space environment. These planetary pick-up ions are formed when the solar wind directly interacts with the neutral atmosphere, causing the ions to be accelerated by the background convective electric field. The subsequent mass loading and ion escape are still the subject of great interest, specifically with respect to which species dominates ion loss from Mars. Modeling efforts and observations have found different results; some conclude that O+ is the most dominant escaping ion while others conclude that O2+ has the larger total loss rate. Furthermore, mass loss might actually favor CO2+ because of its tri-atomic structure. To address this unresolved issue, this study will present velocity space distributions for different species and discuss fluxes and escape rates using different modeling parameters. The simulation will also illustrate individual particle traces, which reveal the origin and trajectories of the different ion species. Finally, results from different solar conditions will be presented with respect to ion fluxes and energies as well as overall escape in order to robustly describe the physical processes controlling planetary ion distributions and atmospheric escape.

Structure and density of cometary nuclei

NASA Astrophysics Data System (ADS)

Weissman, Paul R.; Lowry, Stephen C.

2008-09-01

Understanding the nature of the cometary nucleus remains one of the major problems in solar system science. Whipple’s (1950) icy conglomerate model has been very successful at explaining a range of cometary phenomena, including the source of cometary activity and the nongravitational orbital motion of the nuclei. However, the internal structure of the nuclei is still largely unknown. We review herein the evidence for cometary nuclei as fluffy aggregates or primordial rubble piles, as first proposed by Donn et al. (1985) and Weissman (1986). These models assume that cometary nuclei are weakly bonded aggregations of smaller, icy- onglomerate planetesimals, possibly held together only by self-gravity. Evidence for this model comes from studies of the accretion and subsequent evolution of material in the solar nebula, from observations of disrupted comets, and in particular comet Shoemaker-Levy 9, from measurements of the ensemble rotational properties of observed cometary nuclei, and from recent spacecraft missions to comets. Although the evidence for rubble pile nuclei is growing, the eventual answer to this question will likely not come until we can place a spacecraft in orbit around a cometary nucleus and study it in detail over many months to years. ESA’s Rosetta mission, now en route to comet 67P/Churyumov- Gerasimenko, will provide that opportunity.

Handling and analysis of ices in cryostats and glove boxes in view of cometary samples

NASA Technical Reports Server (NTRS)

Roessler, K.; Eich, G.; Heyl, M.; Kochan, H.; Oehler, A.; Patnaik, A.; Schlosser, W.; Schulz, R.

1989-01-01

Comet nucleus sample return mission and other return missions from planets and satellites need equipment for handling and analysis of icy samples at low temperatures under vacuum or protective gas. Two methods are reported which were developed for analysis of small icy samples and which are modified for larger samples in cometary matter simulation experiments (KOSI). A conventional optical cryostat system was modified to allow for transport of samples at 5 K, ion beam irradiation, and measurement in an off-line optical spectrophotometer. The new system consists of a removable window plug containing nozzles for condensation of water and volatiles onto a cold finger. This plug can be removed in a vacuum system, changed against another plug (e.g., with other windows (IR, VIS, VUV) or other nozzles). While open, the samples can be treated under vacuum with cooling by manipulators (cut, removal, sample taking, irradiation with light, photons, or ions). After bringing the plug back, the samples can be moved to another site of analysis. For handling the 30 cm diameter mineral-ice samples from the KOSI experiments an 80x80x80 cm glove box made out of plexiglass was used. The samples were kept in a liquid nitrogen bath, which was filled from the outside. A stream a dry N2 and evaporating gas from the bath purified the glove box from impurity gases and, in particular, H2O, which otherwise would condense onto the samples.

Electron molecular ion recombination: product excitation and fragmentation.

PubMed

Adams, Nigel G; Poterya, Viktoriya; Babcock, Lucia M

2006-01-01

Electron-ion dissociative recombination is an important ionization loss process in any ionized gas containing molecular ions. This includes the interstellar medium, circumstellar shells, cometary comae, planetary ionospheres, fusion plasma boundaries, combustion flames, laser plasmas and chemical deposition and etching plasmas. In addition to controlling the ionization density, the process generates many radical species, which can contribute to a parallel neutral chemistry. Techniques used to obtain rate data and product information (flowing afterglows and storage rings) are discussed and recent data are reviewed including diatomic to polyatomic ions and cluster ions. The data are divided into rate coefficients and cross sections, including their temperature/energy dependencies, and quantitative identification of neutral reaction products. The latter involve both ground and electronically excited states and including vibrational excitation. The data from the different techniques are compared and trends in the data are examined. The reactions are considered in terms of the basic mechanisms (direct and indirect processes including tunneling) and recent theoretical developments are discussed. Finally, new techniques are mentioned (for product identification; electrostatic storage rings, including single and double rings; Coulomb explosion) and new ways forward are suggested.

Heavy ion-acoustic rogue waves in electron-positron multi-ion plasmas

NASA Astrophysics Data System (ADS)

Chowdhury, N. A.; Mannan, A.; Hasan, M. M.; Mamun, A. A.

2017-09-01

The nonlinear propagation of heavy-ion-acoustic (HIA) waves (HIAWs) in a four-component multi-ion plasma (containing inertial heavy negative ions and light positive ions, as well as inertialess nonextensive electrons and positrons) has been theoretically investigated. The nonlinear Schrödinger (NLS) equation is derived by employing the reductive perturbation method. It is found that the NLS equation leads to the modulational instability (MI) of HIAWs, and to the formation of HIA rogue waves (HIARWs), which are due to the effects of nonlinearity and dispersion in the propagation of HIAWs. The conditions for the MI of HIAWs and the basic properties of the generated HIARWs are identified. It is observed that the striking features (viz., instability criteria, growth rate of MI, amplitude and width of HIARWs, etc.) of the HIAWs are significantly modified by the effects of nonextensivity of electrons and positrons, the ratio of light positive ion mass to heavy negative ion mass, the ratio of electron number density to light positive ion number density, the ratio of electron temperature to positron temperature, etc. The relevancy of our present investigation to the observations in space (viz., cometary comae and earth's ionosphere) and laboratory (viz., solid-high intense laser plasma interaction experiments) plasmas is pointed out.

Heavy ion-acoustic rogue waves in electron-positron multi-ion plasmas.

PubMed

Chowdhury, N A; Mannan, A; Hasan, M M; Mamun, A A

2017-09-01

The nonlinear propagation of heavy-ion-acoustic (HIA) waves (HIAWs) in a four-component multi-ion plasma (containing inertial heavy negative ions and light positive ions, as well as inertialess nonextensive electrons and positrons) has been theoretically investigated. The nonlinear Schrödinger (NLS) equation is derived by employing the reductive perturbation method. It is found that the NLS equation leads to the modulational instability (MI) of HIAWs, and to the formation of HIA rogue waves (HIARWs), which are due to the effects of nonlinearity and dispersion in the propagation of HIAWs. The conditions for the MI of HIAWs and the basic properties of the generated HIARWs are identified. It is observed that the striking features (viz., instability criteria, growth rate of MI, amplitude and width of HIARWs, etc.) of the HIAWs are significantly modified by the effects of nonextensivity of electrons and positrons, the ratio of light positive ion mass to heavy negative ion mass, the ratio of electron number density to light positive ion number density, the ratio of electron temperature to positron temperature, etc. The relevancy of our present investigation to the observations in space (viz., cometary comae and earth's ionosphere) and laboratory (viz., solid-high intense laser plasma interaction experiments) plasmas is pointed out.

Study of Comets Composition and Structure

NASA Astrophysics Data System (ADS)

Khalaf, S. Z.; Selman, A. A.; Ali, H. S.

2008-12-01

The present paper focuses on the nature of the different interactions between cometary nucleus and tail with solar wind. The dynamics of the comet will impose many features that provide unique behavior of the comet when entering the solar system. These features are reviewed in this paper and few investigations are made. The calculations made in this work represent the analysis and interpretation of the different features of the comet, such as perihelion and eccentricity dependence on the gas production rate, and the dependence of the latter on the composition of the comet nucleus. The dependences of the heliocentric, bow shock, contact surface, and stand-off distances with gas production rate for many types of comets that cover linear and non-linear types are studied in this work. Important results are obtained which indicated the different physical interactions between cometary ions and solar wind. Furthermore, the important relation between mean molecular weight and gas production rate are analyzed and studied in this work and a conclusion is made that, as the gas production rate increases, the mean molecular weight will decrease exponentially. A detailed discussion for this unique relation is given.

Digging into the corona: A modeling framework trained with Sun-grazing comet observations

NASA Astrophysics Data System (ADS)

Jia, Y. D.; Pesnell, W. D.; Bryans, P.; Downs, C.; Liu, W.; Schwartz, S. J.

2017-12-01

Images of comets diving into the low corona have been captured a few times in the past decade. Structures visible at various wavelengths during these encounters indicate a strong variation of the ambient conditions of the corona. We combine three numerical models: a global coronal model, a particle transportation model, and a cometary plasma interaction model into one framework to model the interaction of such Sun-grazing comets with plasma in the low corona. In our framework, cometary vapors are ionized via multiple channels and then captured by the coronal magnetic field. In seconds, these ions are further ionized into their highest charge state, which is revealed by certain coronal emission lines. Constrained by observations, we apply our framework to trace back to the local conditions of the ambient corona, and their spatial/time variation over a broad range of scales. Once trained by multiple stages of the comet's journey in the low corona, we illustrate how this framework can leverage these unique observations to probe the structure of the solar corona and solar wind.

Ion cyclotron instability at Io: Hybrid simulation results compared to in situ observations

NASA Astrophysics Data System (ADS)

Šebek, Ondřej; Trávníček, Pavel M.; Walker, Raymond J.; Hellinger, Petr

2016-08-01

We present analysis of global three-dimensional hybrid simulations of Io's interaction with Jovian magnetospheric plasma. We apply a single-species model with simplified neutral-plasma chemistry and downscale Io in order to resolve the ion kinetic scales. We consider charge exchange, electron impact ionization, and photoionization by using variable rates of these processes to investigate their impact. Our results are in a good qualitative agreement with the in situ magnetic field measurements for five Galileo flybys around Io. The hybrid model describes ion kinetics self-consistently. This allows us to assess the distribution of temperature anisotropies around Io and thereby determine the possible triggering mechanism for waves observed near Io. We compare simulated dynamic spectra of magnetic fluctuations with in situ observations made by Galileo. Our results are consistent with both the spatial distribution and local amplitude of magnetic fluctuations found in the observations. Cyclotron waves, triggered probably by the growth of ion cyclotron instability, are observed mainly downstream of Io and on the flanks in regions farther from Io where the ion pickup rate is relatively low. Growth of the ion cyclotron instability is governed mainly by the charge exchange rate.

40 CFR 86.1870-12 - CO2 credits for qualifying full-size pickup trucks.

Code of Federal Regulations, 2013 CFR

2013-07-01

... broadcast battery pack voltage via an on-board diagnostics parameter ID channel. (1) Full size pickup trucks... conditioning leakage and/or efficiency credits as determined in §§ 86.1867 and 6.1868. Pickup trucks earning...

47 CFR 74.433 - Temporary authorizations.

Code of Federal Regulations, 2014 CFR

2014-10-01

... identification number of the associated broadcast station or stations, call letters of remote pickup station (if..., AUXILIARY, SPECIAL BROADCAST AND OTHER PROGRAM DISTRIBUTIONAL SERVICES Remote Pickup Broadcast Stations § 74.433 Temporary authorizations. (a) Special temporary authority may be granted for remote pickup station...

47 CFR 74.433 - Temporary authorizations.

Code of Federal Regulations, 2012 CFR

2012-10-01

... identification number of the associated broadcast station or stations, call letters of remote pickup station (if..., AUXILIARY, SPECIAL BROADCAST AND OTHER PROGRAM DISTRIBUTIONAL SERVICES Remote Pickup Broadcast Stations § 74.433 Temporary authorizations. (a) Special temporary authority may be granted for remote pickup station...

47 CFR 74.433 - Temporary authorizations.

Code of Federal Regulations, 2011 CFR

2011-10-01

... identification number of the associated broadcast station or stations, call letters of remote pickup station (if..., AUXILIARY, SPECIAL BROADCAST AND OTHER PROGRAM DISTRIBUTIONAL SERVICES Remote Pickup Broadcast Stations § 74.433 Temporary authorizations. (a) Special temporary authority may be granted for remote pickup station...

47 CFR 74.433 - Temporary authorizations.

Code of Federal Regulations, 2013 CFR

2013-10-01

... identification number of the associated broadcast station or stations, call letters of remote pickup station (if..., AUXILIARY, SPECIAL BROADCAST AND OTHER PROGRAM DISTRIBUTIONAL SERVICES Remote Pickup Broadcast Stations § 74.433 Temporary authorizations. (a) Special temporary authority may be granted for remote pickup station...

Pickup Protons: Comparisons using the Three-Dimensional MHD HHMS-PI model and Ulysses SWICS Measurements

NASA Technical Reports Server (NTRS)

Intriligator, Devrie S.; Detman, Thomas; Gloecker, George; Gloeckler, Christine; Dryer, Murray; Sun, Wei; Intriligator, James; Deehr, Charles

2012-01-01

We report the first comparisons of pickup proton simulation results with in situ measurements of pickup protons obtained by the SWICS instrument on Ulysses. Simulations were run using the three dimensional (3D) time-dependent Hybrid Heliospheric Modeling System with Pickup Protons (HHMS-PI). HHMS-PI is an MHD solar wind model, expanded to include the basic physics of pickup protons from neutral hydrogen that drifts into the heliosphere from the local interstellar medium. We use the same model and input data developed by Detman et al. (2011) to now investigate the pickup protons. The simulated interval of 82 days in 2003 2004, includes both quiet solar wind (SW) and also the October November 2003 solar events (the Halloween 2003 solar storms). The HHMS-PI pickup proton simulations generally agree with the SWICS measurements and the HHMS-PI simulated solar wind generally agrees with SWOOPS (also on Ulysses) measurements. Many specific features in the observations are well represented by the model. We simulated twenty specific solar events associated with the Halloween 2003 storm. We give the specific values of the solar input parameters for the HHMS-PI simulations that provide the best combined agreement in the times of arrival of the solar-generated shocks at both ACE and Ulysses. We show graphical comparisons of simulated and observed parameters, and we give quantitative measures of the agreement of simulated with observed parameters. We suggest that some of the variations in the pickup proton density during the Halloween 2003 solar events may be attributed to depletion of the inflowing local interstellar medium (LISM) neutral hydrogen (H) caused by its increased conversion to pickup protons in the immediately preceding shock.

Solar Wind Charge Exchange Studies Of Highly Charged Ions On Atomic Hydrogen

NASA Astrophysics Data System (ADS)

Draganić, I. N.; Seely, D. G.; McCammon, D.; Havener, C. C.

2011-06-01

Accurate studies of low-energy charge exchange (CX) are critical to understanding underlying soft X-ray radiation processes in the interaction of highly charged ions from the solar wind with the neutral atoms and molecules in the heliosphere, cometary comas, planetary atmospheres, interstellar winds, etc.. Particularly important are the CX cross sections for bare, H-like, and He-like ions of C, N, O and Ne, which are the dominant charge states for these heavier elements in the solar wind. Absolute total cross sections for single electron capture by H-like ions of C, N, O and fully-stripped O ions from atomic hydrogen have been measured in an expanded range of relative collision energies (5 eV/u-20 keV/u) and compared to previous H-oven measurements. The present measurements are performed using a merged-beams technique with intense highly charged ion beams extracted from a 14.5 GHz ECR ion source installed on a high voltage platform at the Oak Ridge National Laboratory. For the collision energy range of 0.3 keV/u-3.3 keV/u, which corresponds to typical ion velocities in the solar wind, the new measurements are in good agreement with previous H-oven measurements. The experimental results are discussed in detail and compared with theoretical calculations where available.

PAL-XFEL cavity beam position monitor pick-up design and beam test

NASA Astrophysics Data System (ADS)

Lee, Sojeong; Park, Young Jung; Kim, Changbum; Kim, Seung Hwan; Shin, Dong Cheol; Han, Jang-Hui; Ko, In Soo

2016-08-01

As an X-ray Free Electron Laser, PAL-XFEL is about to start beam commissioning. X-band cavity beam position monitor (BPM) is used in the PAL-XFEL undulator beam line. Prototypes of cavity BPM pick-up were designed and fabricated to test the RF characteristics. Also, the beam test of a cavity BPM pick-up was done in the Injector Test Facility (ITF). In the beam test, the raw signal properties of the cavity BPM pick-up were measured at a 200 pC bunch charge. According to the RF test and beam test results, the prototype cavity BPM pick-up design was confirmed to meet the requirements of the PAL-XFEL cavity BPM system.

Mineralogy, Three Dimensional Structure, and Oxygen Isotope Ratios of Four Crystalline Particles from Comet 81P/Wild 2

NASA Technical Reports Server (NTRS)

Nakamura, T.; Noguchi, T.; Tsuchiyama, A.; Ushikubo, T.; Kita, N. T.; Valley, J. W.; Zolensky, M. E.; Kakazu, Y.; Sakamoto, K.; Mashio, E.;

Measurement of 100- and 290-MeV/A Carbon Incident Neutron Production Cross Sections for Carbon, Nitrogen and Oxygen

NASA Astrophysics Data System (ADS)

Shigyo, N.; Uozumi, U.; Uehara, H.; Nishizawa, T.; Mizuno, T.; Takamiya, M.; Hashiguchi, T.; Satoh, D.; Sanami, T.; Koba, Y.; Takada, M.; Matsufuji, N.

2014-05-01

Neutron double-differential cross sections from carbon ion incident on carbon, nitrogen and oxygen targets have been measured for neutron energies down to 0.6 MeV in wide directions from 15∘ to 90∘ with 100- and 290-MeV/A incident energies at the Heavy Ion Medical Accelerator in Chiba (HIMAC), National Institute of Radiological Sciences. Two sizes of NE213 scintillators were used as neutron detectors in order to enable neutron energy from below one to several hundred MeV. The neutron energy was measured by the time-of-flight technique between the beam pickup detector and an NE213 scintillator. By using the experimental data, the validity of the calculation results by the PHITS code was examined.

Research on Orbital Plasma Electrodynamics (ROPE)

NASA Technical Reports Server (NTRS)

Intriligator, Devrie S.

1998-01-01

This final report summarizes some of the important scientific contributions to the Research on Orbital Plasma Electrodynamics (ROPE) investigation, to the Tethered Satellite System (TSS) mission, and to NASA that resulted from the work carried out under this contract at Carmel Research Center. These include Dr. Intriligator's participation in the PIT for the TSS-1R simulations and flight, her participation in ROPE team meetings and IWG meetings, her scientific analyses, and her writing and submitting technical papers to scientific journals. The scientific analyses concentrated on the characterization of energetic ions and their possible relation to pickup ion effects, correlation of particle and other effects (e.g., magnetic field, satellite surface), and collaboration with theorists including with ROPE co-investigators. In addition, scientific analyses were carried out of the effects due to satellite gas releases.

Overview of recent trends and developments for BPM systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wendt, M.; /Fermilab

2011-08-01

Beam position monitoring (BPM) systems are the workhorse of beam diagnostics for almost any kind of charged particle accelerator: linear, circular or transport-lines, operating with leptons, hadrons or heavy ions. BPMs are essential for beam commissioning, accelerator fault analysis and trouble shooting, machine optics, as well as lattice measurements, and finally, for accelerator optimization, in order to achieve the ultimate beam quality. This presentation summarizes the efforts of the beam instrumentation community on recent developments and advances on BPM technologies, i.e. BPM pickup monitors and front-end electronics (analog and digital). Principles, examples, and state-of-the-art status on various BPM techniques, servingmore » hadron and heavy ion machines, sync light synchrotron's, as well as electron linacs for FEL or HEP applications are outlined.« less

47 CFR 74.431 - Special rules applicable to remote pickup stations.

Code of Federal Regulations, 2013 CFR

2013-10-01

... damaged, stations licensed under Subpart D may be used to provide temporary circuits for a period not... SERVICES Remote Pickup Broadcast Stations § 74.431 Special rules applicable to remote pickup stations. (a..., frequency coordination, establishing microwave links, and operational communications. Operational...

47 CFR 74.431 - Special rules applicable to remote pickup stations.

Code of Federal Regulations, 2012 CFR

2012-10-01

... damaged, stations licensed under Subpart D may be used to provide temporary circuits for a period not... SERVICES Remote Pickup Broadcast Stations § 74.431 Special rules applicable to remote pickup stations. (a..., frequency coordination, establishing microwave links, and operational communications. Operational...

47 CFR 74.431 - Special rules applicable to remote pickup stations.

Code of Federal Regulations, 2014 CFR

2014-10-01

... damaged, stations licensed under Subpart D may be used to provide temporary circuits for a period not... SERVICES Remote Pickup Broadcast Stations § 74.431 Special rules applicable to remote pickup stations. (a..., frequency coordination, establishing microwave links, and operational communications. Operational...

47 CFR 74.431 - Special rules applicable to remote pickup stations.

Code of Federal Regulations, 2011 CFR

2011-10-01

... damaged, stations licensed under Subpart D may be used to provide temporary circuits for a period not... SERVICES Remote Pickup Broadcast Stations § 74.431 Special rules applicable to remote pickup stations. (a..., frequency coordination, establishing microwave links, and operational communications. Operational...

Effects of spatial transport and ambient wave intensity on the generation of MHD waves by interstellar pickup protons

NASA Technical Reports Server (NTRS)

Isenberg, P. A.

1995-01-01

Intense MHD waves generated by the isotropization of interstellar pickup protons were predicted by Lee and Ip (1987) to appear in the solar wind whenever pickup proton fluxes were high enough. However, in reality these waves have proved surprisingly difficult to identify, even in the presence of observed pickup protons. We investigate the wave excitation by isotropization from an initially broad pitch-angle distribution instead of the narrow ring-beam assumed by Lee and Ip. The pitch angle of a newly-ionized proton is given by theta(sub o), the angle between the magnetic field (averaged over a pickup proton gyroradius) and the solar wind flow at the time of ionization. Then, a broadened distribution results from spatial transport of pickup protons prior to isotropization from regions upstream along the field containing different values of theta(sub o). The value of theta(sub o) will vary as a result of the ambient long-wavelength fluctuations in the solar wind. Thus, the range of initial pitch-angles is directly related to the amplitude of these fluctuations within a length-scale determined by the isotropization time. We show that a broad initial pitch-angle distribution can significantly modify the intensity and shape of the pickup-proton-generated wave spectrum, and we derive a criterion for the presence of observable pickup-proton generated waves given the intensity of the ambient long wavelength fluctuations.

Implant Impression Techniques for the Edentulous Jaw: A Summary of Three Studies.

PubMed

Stimmelmayr, Michael; Beuer, Florian; Edelhoff, Daniel; Güth, Jan-Frederik

2016-02-01

Precise implant-supported restorations require accurate impressions. Transfer, pick-up, and splinted pick-up are commonly used techniques. Several in vitro studies have compared these impression techniques; however, all studies used mechanical evaluation methods. The purpose of this study was to compare the discrepancies of these impression techniques digitally in vitro and in vivo. Four dental implants were inserted in ten polymer mandibular models bilaterally in the regions of the first molars and canines. Three different impressions were made of each model and the models (original and stone casts) were scanned and digitized. Clinically, four implants were inserted in ten edentulous jaws; transfer and splinted pick-up impressions were made. With inspection software, discrepancies between the different impressions were calculated. The mean discrepancies in the in vitro study of the original polymer model to stone casts were 124 ± 34 μm for the transfer type, 116 ± 46 μm for the pick-up type, and 80 ± 25 μm for the splinted pick-up type, resulting in a mean discrepancy between the transfer and splinted pick-up type of 44 μm (124 - 80 μm). Clinically, the mean discrepancy between these two impression techniques was 280 μm. The differing results between the transfer and splinted pick-up techniques of in vitro and in vivo data showed the need for clinical data; however, splinted pick-up impressions seemed to produce the most precise results. © 2015 by the American College of Prosthodontists.

Hot magnetospheric O+ and cold ion behavior in magnetopause reconnection: Cluster observations

NASA Astrophysics Data System (ADS)

Wang, S.; Kistler, L. M.; Mouikis, C. G.; Liu, Y.; Genestreti, K. J.

2014-12-01

In reconnection, the presence of heavy ions like O+ increases the ion mass density reducing the fluid's Alfvén speed. In addition, it may modify the reconnection structure, which can also change the reconnection rate. However, because O+ ions have a larger Larmor radii than H+ ions at the same velocity, they may not be fully entrained in the reconnection flow and may have kinetic effects other than just increasing the mass density. In this study, for the first time, the ion velocity distribution functions of H+ and O+ from one magnetopause reconnection event with a strong guide field are analyzed to determine in detail the behavior of the different ion populations. We show that the hot magnetospheric O+ ions, along with the hot magnetospheric H+ ions almost fully participate in the reconnection exhaust flows. Finite Larmor radius effects are also apparent and control how far the ions extend on the magnetosheath side. Ion signatures consistent with heating after being picked up in the reconnection exhaust flow are observed in the H+ and O+ distribution functions. The dynamics of the cold magnetospheric ions depends on where they enter the reconnection region. If they enter the reconnection region at the downstream separatrix, they will be taken away by the magnetic field in an adiabatic way as analyzed by Drake et al. (2009a); if they enter close to the diffusion region, they behave as pick-up ions.

Continuum model for hydrogen pickup in zirconium alloys of LWR fuel cladding

NASA Astrophysics Data System (ADS)

Wang, Xing; Zheng, Ming-Jie; Szlufarska, Izabela; Morgan, Dane

2017-04-01

A continuum model for calculating the time-dependent hydrogen pickup fractions in various Zirconium alloys under steam and pressured water oxidation has been developed in this study. Using only one fitting parameter, the effective hydrogen gas partial pressure at the oxide surface, a qualitative agreement is obtained between the predicted and previously measured hydrogen pickup fractions. The calculation results therefore demonstrate that H diffusion through the dense oxide layer plays an important role in the hydrogen pickup process. The limitations and possible improvement of the model are also discussed.

Superconductive imaging surface magnetometer

DOEpatents

Overton, Jr., William C.; van Hulsteyn, David B.; Flynn, Edward R.

1991-01-01

An improved pick-up coil system for use with Superconducting Quantum Interference Device gradiometers and magnetometers involving the use of superconducting plates near conventional pick-up coil arrangements to provide imaging of nearby dipole sources and to deflect environmental magnetic noise away from the pick-up coils. This allows the practice of gradiometry and magnetometry in magnetically unshielded environments. One embodiment uses a hemispherically shaped superconducting plate with interior pick-up coils, allowing brain wave measurements to be made on human patients. another embodiment using flat superconducting plates could be used in non-destructive evaluation of materials.

Modeling Cometary Coma with a Three Dimensional, Anisotropic Multiple Scattering Distributed Processing Code

NASA Technical Reports Server (NTRS)

Luchini, Chris B.

1997-01-01

Development of camera and instrument simulations for space exploration requires the development of scientifically accurate models of the objects to be studied. Several planned cometary missions have prompted the development of a three dimensional, multi-spectral, anisotropic multiple scattering model of cometary coma.

Hyperspectral Imaging and Obstacle Detection for Robotics Navigation

DTIC Science & Technology

2005-09-01

anatomy and diffraction process. 17 3.3 Technical Specifications of the System A. Brimrose AOTF Video Adaptor Specifications: Material TeO2 Active...sampled from glass case on person 2’s belt 530 pixels 20 pick-up white sampled from body panels of pick-up 600 pixels 21 pick-up blue sampled from

Messenger Observations Inside 1 AU of Low-Frequency Magnetic Waves due to Inner Source Pickup Protons

NASA Astrophysics Data System (ADS)

Smith, C. W.; Argall, M. R.; Schwadron, N.; Joyce, C.; Isenberg, P. A.; Vasquez, B. J.; Korth, H.; Anderson, B. J.

2017-12-01

Wave excitation by pickup protons inside 1 AU have not been previously reported. Waves excited by pickup protons have a characteristic signature, a spectral peak at and above the proton gyrofrequency, that demonstrates a significant lack of particle energization beyond the initial pickup proton energy combined with pitch-angle scattering. Interstellar Hydrogen atoms cannot penetrate significantly inside about 3.5 AU due to loss of these atoms through ionization. Since the waves reported here, which are observed by the Messenger spacecraft during the cruise phase to Mercury, are not seen near the Mercury and Venus planetary encounters and there is no evidence of low-frequency waves that would indicate proximity to comets, we conclude that these waves originate from pickup protons created by the interaction of solar wind with dust relatively close to the Sun, inside 0.4 AU (Schwadron et al. 2000; Schwadron & Geiss 2000). This is the so-called inner source of pickup protons. We will present our analyses of these wave observations.Schwadron et al., J. Geophys. Res., 105, 7465, 2000.Schwadron & Geiss, J. Geophys. Res., 10, 7473, 2000.

Pickup protons and pressure-balanced structures: Voyager 2 observations in merged interaction regions near 35 AU

NASA Astrophysics Data System (ADS)

Burlaga, L. F.; Ness, N. F.; Belcher, J. W.; Szabo, A.; Isenberg, P. A.; Lee, M. A.

1994-11-01

Five pressure-balanced structures, each with a scale of the order of a few hundredths of an astonomical unit (AU), were identified in two merged interaction regions (MIRs) near 35 AU in the Voyager 2 plasma and magnetic field data. They include a tangential discontinuity, simple and complex magnetic holes, slow correlated variations among the plasma and magnetic field parameters, and complex uncorrelated variations among the parameters. The changes in the magnetic pressure in these events are balanced by changes in the pressure of interstellar pickup protons. Thus the pickup protons probably play a major role in the dynamics of the MIRs. The solar wind proton and electron pressures are relatively unimportant in the MIRs at 35 AU and beyond. The region near 35 AU is transition region: the Sun is the source of the magnetic field, but the interstellar medium in source of pickups protons. Relative to the solar wind proton guyroadius, the thicknesses of the discontinuities and simple magnetic holes observed near 35 AU are at least an order of magnitude greater than those observed at 1 AU. However, the thicknesses of the tangential discontinuity and simple magnetic holes observed near 35 AU (in units of the pickup proton Larmor radius) are comparable to those observed at 1 AU (in units of the solar wind proton gyroradius). Thus the gyroradius of interstellar pickup protons controls the thickness of current sheets near 35 AU. We determine the interstellar pickup proton pressure in the PBSs. Using a model for the pickup proton temperature, we estimate that the average interstellar pickup proton pressure, temperature, and density in the MIRs at 35 AU are (0.53 +/- 0.14) x 10-12 erg/cu cm, (5.8 +/- 0.4) x 106 K and (7 +/- 2) x 10-4/cu cm.

Ion acceleration by multiple reflections at Martian bow shock

NASA Astrophysics Data System (ADS)

Yamauchi, M.; Futaana, Y.; Fedorov, A.; Frahm, R. A.; Dubinin, E.; Lundin, R.; Sauvaud, J.-A.; Winningham, J. D.; Barabash, S.; Holmström, M.

2012-02-01

The ion mass analyzer (IMA) on board Mars Express revealed bundled structures of ions in the energy domain within a distance of a proton gyroradius from the Martian bow shock. Seven prominent traversals during 2005 were examined when the energy-bunched structure was observed together with pick-up ions of exospheric origin, the latter of which is used to determine the local magnetic field orientation from its circular trajectory in velocity space. These seven traversals include different bow shock configurations: (a) quasi-perpendicular shock with its specular direction of the solar wind more perpendicular to the magnetic field (QT), (b) quasi-perpendicular shock with its specular reflection direction of the solar wind more along the magnetic field (FS), and (c) quasi-parallel (QL) shock. In all seven cases, the velocity components of the energy-bunched structure are consistent with multiple specular reflections of the solar wind at the bow shock up to at least two reflections. The accelerated solar wind ions after two specular reflections have large parallel components with respect to the magnetic field for both QL cases whereas the field-aligned speed is much smaller than the perpendicular speed for all QT cases.

Mirror-mode structures at Comet 1P/Halley: A comparison between VEGA1 and Giotto Flyby

NASA Astrophysics Data System (ADS)

Volwerk, M.; Glassmeier, K.-H.; Schmid, D.; Delva, M.; Koenders, C.

2014-04-01

The pickup of freshly ionized particles emitted by the cometary nucleus creates a particle distribution in phase-space which is, amongst others, mirror-mode unstable. Many detailed studies have shown the presence of mirror-mode structures in the vicinity of comet 1P/Halley, using data from VEGA1/2 and Giotto. In the current presentation the almost similar flybys of VEGA1 and Giotto are compared with respect to the presence and occurrence rate of mirrormode structures. An automated search on the magnetic field data is performed, using minimum variance analysis, which has proved its usefulness in earlier mirror-mode studies at Earth, Venus and comets. It is found that there is an asymmetry between the two flybys: both missions show many events before closest approach and magnetic pile up region, however, after closest approach and magnetic pile up region the mirror-modes are strongly reduced at Giotto, whereas they increase in number for VEGA1. One source of influence could be the solar wind IMF, which is different: VEGA1 IMF ≈ (0, 0, 15) nT, Vsw ≈ 500 km/s and Giotto IMF ≈ (-3/3, -4, 5) nT (Bx rotating over the passage), Vsw ≈ 370 km/s. In this presentation we will discuss the occurrence rate, sizes and other characteristics of the mirror-mode structures.

The risk of injury to children in compact pickup trucks.

PubMed

Winston, Flaura K; Durbin, Dennis

2002-01-01

Nearly one million compact pickup trucks were sold last year in the US. Manufacturers now produce extended-cab models of pickups such as the Ford Ranger, Chevrolet S-10, Dodge Dakota, and Toyota Tacoma that can accommodate at least two rear-seated passengers, making them attractive to families with children. However, the safety of these rear seats for children has not been determined. This Issue Brief summarizes a new study that examines and quantifies the risk of injury to children riding in compact pickup trucks. Based on these findings, parents should be advised against using these vehicles as family transportation.

Non-destructive single-pass low-noise detection of ions in a beamline

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schmidt, Stefan; Institut für Kernchemie, Johannes Gutenberg–Universität Mainz, 55099 Mainz; Murböck, Tobias

2015-11-15

We have conceived, built, and operated a device for the non-destructive single-pass detection of charged particles in a beamline. The detector is based on the non-resonant pick-up and subsequent low-noise amplification of the image charges induced in a cylindrical electrode surrounding the particles’ beam path. The first stage of the amplification electronics is designed to be operated from room temperature down to liquid helium temperature. The device represents a non-destructive charge counter as well as a sensitive timing circuit. We present the concept and design details of the device. We have characterized its performance and show measurements with low-energy highlymore » charged ions (such as Ar{sup 13+}) passing through one of the electrodes of a cylindrical Penning trap. This work demonstrates a novel approach of non-destructive, low noise detection of charged particles which is, depending on the bunch structure, suitable, e.g., for ion traps, low-energy beamlines or accelerator transfer sections.« less

Progress in our understanding of cometary dust tails

NASA Technical Reports Server (NTRS)

Sekanina, Z.

1976-01-01

Various analytical techniques are employed to analyze observations on the character, composition, and size distribution of solid particles in cometary dust tails. Emphasized is the mechanical theory that includes solar gravitational attraction and solar radiation pressure to explain dust particle motions in cometary tails, as well as interactions between dust and plasma.

Cometary exploration in the shuttle era

NASA Technical Reports Server (NTRS)

Farquhar, R. W.; Wooden, W. H., II

1978-01-01

A comprehensive program plan for cometary exploration in the 1980-2000 time frame is proposed. Plans for ground-based observations, a Spacelab cometary observatory, and the Space Telescope are included in the observational program. The cometary mission sequence begins with a dual-spacecraft flyby of Halley's comet. The nominal mission strategy calls for a simultaneous launch of two spacecraft towards an intercept with Halley in March 1986. After the Halley encounter, the spacecraft are retargeted: one to intercept comet Borrelly in January 1988 and the other to intercept comet Tempel-2 in September 1988. The additional cometary intercepts are accomplished by utilizing a novel Earth-swingby technique. The next mission in the cometary program plan, a rendezvous with Encke's comet, is scheduled for launch in early 1990. It is planned to rendezvous with Encke in September 1992 at a heliocentric distance of 4 AU. Following this near-aphelion rendezvous, the spacecraft will remain with with Encke through the next two perihelion passages in February 1994 and May 1997. The rendezvous mission will be terminated about seven months after the second perihelion passage.

Stardust in STARDUST - the C, N, and O Isotopic Compositions of Wild 2 Cometary Matter in Al Foil Impacts

NASA Technical Reports Server (NTRS)

Stadermann, Frank J.; Hoppe, Peter; Floss, Christine; Heck, Philipp R.; Hoerz, Friedrich; Huth, Joachim; Kearsley, Anton T.; Leitner, Jan; Marhas, Kuljeet K.; McKeegan, Kevin D.;

Direct Detection of Complex Organic Products in Ultraviolet (Lyα) and Electron-irradiated Astrophysical and Cometary Ice Analogs Using Two-step Laser Ablation and Ionization Mass Spectrometry

NASA Astrophysics Data System (ADS)

Henderson, Bryana L.; Gudipati, Murthy S.

2015-02-01

As discovery of complex molecules and ions in our solar system and the interstellar medium has proliferated, several groups have turned to laboratory experiments in an effort to simulate and understand these chemical processes. So far only infrared (IR) and ultraviolet (UV) spectroscopy has been able to directly probe these reactions in ices in their native, low-temperature states. Here we report for the first time results using a complementary technique that harnesses two-step two-color laser ablation and ionization to measure mass spectra of energetically processed astrophysical and cometary ice analogs directly without warming the ices—a method for hands-off in situ ice analysis. Electron bombardment and UV irradiation of H2O, CH3OH, and NH3 ices at 5 K and 70 K led to complex irradiation products, including HCO, CH3CO, formamide, acetamide, methyl formate, and HCN. Many of these species, whose assignment was also strengthened by isotope labeling studies and correlate with IR-based spectroscopic studies of similar irradiated ices, are important ingredients for the building blocks of life. Some of them have been detected previously via astronomical observations in the interstellar medium and in cometary comae. Other species such as CH3CO (acetyl) are yet to be detected in astrophysical ices or interstellar medium. Our studies suggest that electron and UV photon processing of astrophysical ice analogs leads to extensive chemistry even in the coldest reaches of space, and lend support to the theory of comet-impact-induced delivery of complex organics to the inner solar system.

The footprint of cometary dust analogues - I. Laboratory experiments of low-velocity impacts and comparison with Rosetta data

NASA Astrophysics Data System (ADS)

Ellerbroek, L. E.; Gundlach, B.; Landeck, A.; Dominik, C.; Blum, J.; Merouane, S.; Hilchenbach, M.; Bentley, M. S.; Mannel, T.; John, H.; van Veen, H. A.

2017-07-01

Cometary dust provides a unique window on dust growth mechanisms during the onset of planet formation. Measurements by the Rosetta spacecraft show that the dust in the coma of comet 67P/Churyumov-Gerasimenko has a granular structure at size scales from sub-μmup to several hundreds of μm, indicating hierarchical growth took place across these size scales. However, these dust particles may have been modified during their collection by the spacecraft instruments. Here, we present the results of laboratory experiments that simulate the impact of dust on the collection surfaces of the COSIMA (Cometary Secondary Ion Mass Anaylzer) and MIDAS (Micro-Imaging Dust Analysis System) instruments onboard the Rosetta spacecraft. We map the size and structure of the footprints left by the dust particles as a function of their initial size (up to several hundred μm) and velocity (up to 6 m s-1). We find that in most collisions, only part of the dust particle is left on the target; velocity is the main driver of the appearance of these deposits. A boundary between sticking/bouncing and fragmentation as an outcome of the particle-target collision is found at v ˜ 2 m s-1. For velocities below this value, particles either stick or leave a single deposit on the target plate, or bounce, leaving a shallow footprint of monomers. At velocities >2 m s-1and sizes >80 μm, particles fragment upon collision, transferring up to 50 per cent of their mass in a rubble-pile-like deposit on the target plate. The amount of mass transferred increases with the impact velocity. The morphologies of the deposits are qualitatively similar to those found by the COSIMA instrument.

47 CFR 74.1290 - FM translator and booster station information available on the Internet.

Code of Federal Regulations, 2010 CFR

2010-10-01

... Transmissions, Permissible (Low Power Auxiliaries) 74.831 Transmitter power (Remote Pickup) 74.461 Transmitters... equipment— Aural Auxiliary 74.550 Remote Pickup 74.451 TV Auxiliaries 74.655 Lw Power Auxiliaries 74.851... stations 74.537 Remote Pickup 74.433 TV Auxiliaries 74.633 Low Power Auxiliaries 74.833 Authorized emission...

17 CFR 240.17Ad-1 - Definitions.

Code of Federal Regulations, 2011 CFR

2011-04-01

... or mails the item to, or the item is awaiting pick-up by, the presentor or a person designated by the... transfer agent dispatches or mails the item to, or the item is awaiting pick-up by, the outside registrar... registrar dispatches or mails the item to, or the item is awaiting pick-up by, the presenting transfer agent...

17 CFR 240.17Ad-1 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-04-01

... or mails the item to, or the item is awaiting pick-up by, the presentor or a person designated by the... transfer agent dispatches or mails the item to, or the item is awaiting pick-up by, the outside registrar... registrar dispatches or mails the item to, or the item is awaiting pick-up by, the presenting transfer agent...

Pluto's interaction with the solar wind

NASA Technical Reports Server (NTRS)

Bagenal, Fran; Mcnutt, Ralph L., Jr.

1989-01-01

If Pluto's atmospheric escape rate is significantly greater than 1.5 x 10 to the 27th molecules/s then the interaction with the tenuous solar wind at 30 A.U. will be like that of a comet. There will be extensive ion pick-up upstream and the size of the interaction region will vary directly with variations in the solar wind flux. If the escape flux is much less, then one expects that the solar wind will be deflected around Pluto's ionosphere in a Venus-like interaction. In either case, the weak interplanetary magnetic field at 30 A.U. results in very large gyroradii for the picked-up ions and a thick bow shock, necessitating a kinetic treatment of the interaction. Strong variations in the size of the interaction region are expected on time scales of days due to changes in the solar wind.

Gasdynamic simulations of the solar wind interaction with Venus - Boundary layer formation

NASA Astrophysics Data System (ADS)

McGary, J. E.

1993-05-01

A 2D gasdynamic simulation of the mass-loaded solar wind flow around the dayside of Venus is presented. For average ionopause conditions near 300 km, the simulations show that mass loading from the pickup of oxygen ions produces a boundary layer of finite thickness along the ionopause. Within this layer and toward the ionopause, the temperature decreases and the total mass density increases significantly. Furthermore, there is a shear in the bulk flow velocity across the boundary layer, such that the tangential flow decreases in speed as the ionopause is approached and remains low along the ionopause which is consistent with Pioneer Venus observations. Numerical simulations are carried out for various mass addition rates and demonstrate that the boundary layer develops when oxygen ion production exceeds approximately 2 x 10 exp 5/cu m per s.

Protostellar and cometary detections of organohalogens

NASA Astrophysics Data System (ADS)

Fayolle, Edith C.; Öberg, Karin I.; Jørgensen, Jes K.; Altwegg, Kathrin; Calcutt, Hannah; Müller, Holger S. P.; Rubin, Martin; van der Wiel, Matthijs H. D.; Bjerkeli, Per; Bourke, Tyler L.; Coutens, Audrey; van Dishoeck, Ewine F.; Drozdovskaya, Maria N.; Garrod, Robin T.; Ligterink, Niels F. W.; Persson, Magnus V.; Wampfler, Susanne F.; Rosina Team

2017-10-01

Organohalogens, a class of molecules that contain at least one halogen atom bonded to carbon, are abundant on the Earth where they are mainly produced through industrial and biological processes1. Consequently, they have been proposed as biomarkers in the search for life on exoplanets2. Simple halogen hydrides have been detected in interstellar sources and in comets, but the presence and possible incorporation of more complex halogen-containing molecules such as organohalogens into planet-forming regions is uncertain3,4. Here we report the interstellar detection of two isotopologues of the organohalogen CH3Cl and put some constraints on CH3F in the gas surrounding the low-mass protostar IRAS 16293-2422, using the Atacama Large Millimeter/submillimeter Array (ALMA). We also find CH3Cl in the coma of comet 67P/Churyumov-Gerasimenko (67P/C-G) by using the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) instrument. The detections reveal an efficient pre-planetary formation pathway of organohalogens. Cometary impacts may deliver these species to young planets and should thus be included as a potential abiotical production source when interpreting future organohalogen detections in atmospheres of rocky planets.

The impact of comet Shoemaker-Levy 9 on the Jovian magnetosphere

NASA Technical Reports Server (NTRS)

Herbert, Floyd

1994-01-01

By the time of the impact of comet P/Shoemaker-Levy 9 with Jupiter, the freshly-broken surfaces of the accompanying rubble will have been outgassing for about two years, and will have produced an expanding and co-moving cloud of gas hundreds of R(sub J) across. Much of this gas, escaping from the cometary fragments at low (equal to or less than 1 km/s) speed, will arrive in the Jovian magnetopshere contemporaneously with the comet and drift through the magnetosphere. This gas, as it is photoionized, will be picked up primarily in the outer magnetosphere and the resulting high-energy ions should intensify magnetospheric processes, such as Io plasma torus and auroral emissions, that are thought to be powered by outer magnetospheric mass loading. If the composition of the comet is similar to that of P/Halley, the power available from mass loading should be comparable to that driving the aurora (10(exp 14) W) and at least an order of magnitude larger than that exciting the plasma torus for several weeks or months. Measurement of these emissions during and after the cometary encounter may constrain the mechanisms for energization of magnetospheric charged particle populations and magnetospheric transport processes.

Vega-Giotto flyby missions and cometary cosmogony

NASA Technical Reports Server (NTRS)

Lang, Bruno

1989-01-01

The most important implication of the Vega/Giotto flyby missions to Halley's Comet for cometary cosmogony is the opportunity to absorb the results of the in-situ measurements as made onboard the spacecrafts. Unfortunately the exploration of ejecta form the nucleus was unable to provide an unambiguous definition of the chemical-mineralogical nature of the nucleus: it failed to provide information comparable to that which was expected from a sample return mission. However, the obtained results are significant enough to affect and redirect cosmogonical thinking. Accordingly, the understanding of the cometary-matter dichotomy is modified as deduced from the distiction of water-dominated volitiles and silicate-based non-volitiles. Organic carbon compounds emerge as a major constituent of cometary nuclei. Presently, it is likely that the revision of Whipple's classic concept of the icy conglomerate cannot be avoided. Affected by the Vega/Giotto flyby missions to Hally's Comet, cometary cosmogony seems to enter a new conceptual period. The results of the in-situ measurements (mass spectrometric, UV spectroscopic, and IR spectroscopic) appear to be of basic importance. A chemical explanation is employed to explain the occurrence inside the nuclei of the variety of species, as inferred from the mass spectrometric data, to predict the results of the processes possibly involved. A cosmochemical factor is postulated to operate behind the observed cometary phenomena. The chemistry of the interstellar medium, covering the circumstellar and interstellar dust, advances cometary cosmogony.

Formation of ions and radicals from icy grains in comets

NASA Technical Reports Server (NTRS)

Jackson, William M.; Gerth, Christopher; Hendricks, Charles

1991-01-01

Ion and radical formation in comets are thought to occur primarily by photodissociation of gas phase molecules. Experimental evidence and theoretical calculations are presented that show that some of the radical and ions can come directly from ice grains. The experimental evidence suggest that if the frozen molecules on the surface of grains undergo direct dissociation then they may be able to release radicals directly in the gas phase. If the molecules undergo predissociation it is unlikely that they will release radicals in the gas phase since they should be quenched. Calculations of this direct photodissociation mechanism further indicate that even if the parent molecule undergoes direct dissociation, the yield will not be high enough to explain the rays structure in comets unless the radicals are stored in the grains and then released when the grain evaporates. Calculations were also performed to determine the maximum number of ions that can be stored in an icy grain's radius. This number is compared with the ratio of the ion to neutral molecular density. The comparison suggests that some of the ions observed near the nucleus of the comet could have originally been present in the cometary nucleus. It is also pointed out that the presence of these ions in icy grains could lead to radical formation via electron recombination. Finally, an avalanche process was evaluated as another means of producing ions in comets.

Laboratory Study on Disconnection Events in Comets

NASA Astrophysics Data System (ADS)

Li, Yan-Fei; Li, Yu-Tong; Wang, Wei-Min; Yuan, Da-Wei; et al.

2018-01-01

When comets interacting with solar wind, straight and narrow plasma tails will be often formed. The most remarkable phenomenon of the plasma tails is the disconnection event, in which a plasma tail is uprooted from the comet's head and moves away from the comet. In this paper, the interaction process between a comet and solar wind is simulated by using a laser-driven plasma cloud to hit a cylinder obstacle. A disconnected plasma tail is observed behind the obstacle by optical shadowgraphy and interferometry. Our particle-in-cell simulations show that the diference in thermal velocity between ions and electrons induces an electrostatic field behind the obstacle. This field can lead to the convergence of ions to the central region, resulting in a disconnected plasma tail. This electrostatic field-induced model may be a possible explanation for the disconnection events of cometary tails.

Ion Acceleration by Multiple Reflections at Martian Bow Shock

NASA Astrophysics Data System (ADS)

Yamauchi, M.; Futaana, Y.; Fedorov, A.; Frahm, R. A.; Dubinin, E.; Lundin, R.; Sauvaud, J.-A.; Winningham, J. D.; Barabash, S.; Holmström, H.

2012-04-01

The ion mass analyzer (IMA) on board Mars Express revealed bundled structures of ions in the energy domain within a distance of a proton gyroradius from the Martian bow shock. Seven prominent traversals during 2005 were examined when the energy-bunched structure was observed together with pick-up ions of exospheric origin, the latter of which is used to determine the local magnetic field orientation from its circular trajectory in velocity space. These seven traversals include different bow shock configurations: (a) quasi-perpendicular shock with its specular direction of the solar wind more perpendicular to the magnetic field (QT), (b) quasi-perpendicular shock with its specular reflection direction of the solar wind more along the magnetic field (FS), and (c) quasi-parallel (QL) shock. In all seven cases, the velocity components of the energy-bunched structure are consistent with multiple specular reflections of the solar wind at the bow shock up to at least two reflections. The accelerated solar wind ions after two specular reflections have large parallel components with respect to the magnetic field for the QL shock whereas the field-aligned speed is much smaller than the perpendicular speed for the QT shock. The reflected ions escape into the solar wind when and only when the reflection is in the field-aligned direction.

Shapes of cometary isophotes with Maxwellian distribution of initial velocities for neutral molecules

NASA Astrophysics Data System (ADS)

Žáček, P.; Wolf, M.

2017-10-01

This paper contains necessary modification of Bessel's equations for the axial cometary syndyne. This correction provides the accurate values of molecular acceleration in a cometary tail and precise values of decay constants for radiating molecules and their lifetimes. In consequence the hypothesis of the predissociation of molecules seems to be useless.

Oxygen Ion Energization at Mars: Comparison of MAVEN and Mars Express Observations to Global Hybrid Simulation

NASA Astrophysics Data System (ADS)

Jarvinen, R.; Brain, D. A.; Modolo, R.; Fedorov, A.; Holmström, M.

2018-02-01

We study oxygen ion energization in the Mars-solar wind interaction by comparing particle and magnetic field observations on the Mars Atmosphere and Volatile EvolutioN (MAVEN) and Mars Express missions to a global hybrid simulation. We find that large-scale structures of the Martian-induced magnetosphere and plasma environment as well as the Mars heavy ion plume as seen by multispacecraft observations are reproduced by the model. Using the simulation, we estimate the dynamics of escaping oxygen ions by analyzing their distance and time of flight as a function of the gained kinetic energy along spacecraft trajectories. In the upstream region the heavy ion energization resembles single-particle solar wind ion pickup acceleration as expected, while within the induced magnetosphere the energization displays other features including the heavy ion plume from the ionosphere. Oxygen ions take up to 80 s and travel the distance of 20,000 km after their emission from the ionosphere to the induced magnetosphere or photoionization from the neutral exosphere before they have reached energies of 10 keV in the plume along the analyzed spacecraft orbits. Lower oxygen ion energies of 100 eV are reached faster in 10-20 s over the distance of 100-200 km in the plume. Our finding suggests that oxygen ions are typically observed within the first half of their gyrophase if the spacecraft periapsis is on the hemisphere where the solar wind convection electric field points away from Mars.

Simulations as a tool for higher mass resolution spectrometer: Lessons from existing observations

NASA Astrophysics Data System (ADS)

Nicolaou, Georgios; Yamauchi, Masatoshi; Nilsson, Hans; Wieser, Martin; Fedorov, Andrei

2017-04-01

Scientific requirements of each mission are crucial for the instrument's design. Ion tracing simulations of instruments can be helpful to characterize their performance, identify their limitations and improving the design for future missions. However, simulations provide the best performance in ideal case, and the actual response is determined by many other factors. Therefore, simulations should be compared with observations when possible. Characterizing the actual response of a running instrument gives valuable lessons for the future design of test instruments with the same detection principle before spending resources to build and calibrate them. In this study we use an ion tracing simulation of the Ion Composition Analyser (ICA) on board ROSETTA, in order to characterize its response and to compare it with the observations. It turned out that, due to the complicated unexpected response of the running instrument, the heavy cometary ions and molecules are sometimes difficult to be resolved. However, preliminary simulation of a slightly modified design predicts much higher mass resolution. Even after considering the complicated unexpected response, we safely expect that the modified design can resolve most abundant heavy atomic ions (e.g., O^+) and molecular ions (e.g., N_2+ and O_2^+). We show the simulation results for both designs and ICA data.

Deuterated Water in Comet C/1996 B2 (Hyakutake) and its Implications for the Origin of Comets

NASA Technical Reports Server (NTRS)

Bockelee-Morvan, D.; Gautier, D.; Lis, D. C.; Young, K.; Keene, J.; Phillips, T. G.; Owen, T.; Crovisier, J.; Goldsmith, P. F.; Bergin, E. A.;

Insights into the nature of cometary organic matter from terrestrial analogues

NASA Astrophysics Data System (ADS)

Court, Richard W.; Sephton, Mark A.

2012-04-01

The nature of cometary organic matter is of great interest to investigations involving the formation and distribution of organic matter relevant to the origin of life. We have used pyrolysis-Fourier transform infrared (FTIR) spectroscopy to investigate the chemical effects of the irradiation of naturally occurring bitumens, and to relate their products of pyrolysis to their parent assemblages. The information acquired has then been applied to the complex organic matter present in cometary nuclei and comae. Amalgamating the FTIR data presented here with data from published studies enables the inference of other comprehensive trends within hydrocarbon mixtures as they are progressively irradiated in a cometary environment, namely the polymerization of lower molecular weight compounds; an increased abundance of polycyclic aromatic hydrocarbon structures; enrichment in 13C; reduction in atomic H/C ratio; elevation of atomic O/C ratio and increase in the temperature required for thermal degradation. The dark carbonaceous surface of a cometary nucleus will display extreme levels of these features, relative to the nucleus interior, while material in the coma will reflect the degree of irradiation experienced by its source location in the nucleus. Cometary comae with high methane/water ratios indicate a nucleus enriched in methane, favouring the formation of complex organic matter via radiation-induced polymerization of simple precursors. In contrast, production of complex organic matter is hindered in a nucleus possessing a low methane/water ration, with the complex organic matter that does form possessing more oxygen-containing species, such as alcohol, carbonyl and carboxylic acid functional groups, resulting from reactions with hydroxyl radicals formed by the radiolysis of the more abundant water. These insights into the properties of complex cometary organic matter should be of particular interest to both remote observation and space missions involving in situ analyses and sample return of cometary materials.

Comparison of teen driver fatality rates by vehicle type in the United States.

PubMed

Trowbridge, Matthew J; McKay, Mary Pat; Maio, Ronald F

2007-10-01

To compare national fatality rates for teen drivers by vehicle type. Fatality rates were calculated for 16- to 19-year-old drivers by vehicle type using data from the Fatal Analysis Reporting System (1999-2003) and estimates of miles driven from the National Household Transportation Survey (2001). Relative fatality risks for teen drivers of sports utility vehicles (SUVs) and pickups were calculated using passenger cars as a reference. Per vehicle mile driven, the fatality risk for both male and female teens driving SUVs was decreased relative to passenger car drivers (male teens: relative risk [RR], 0.33 [95% confidence interval [CI] = 0.29 to 0.37]; female teens: RR, 0.45 [95% CI = 0.34 to 0.59]). Fatality rates for male teens driving pickups were also lower per mile driven compared with male passenger car drivers (RR, 0.55 [95% CI = 0.51 to 0.60]). Fatality rates for female teens driving pickups and passenger cars were not statistically different but appear potentially higher for pickups (RR, 1.19 [95% CI = 0.98 to 1.44]). Both SUVs and pickups demonstrated significantly higher rates of fatal rollovers than passenger cars. Female adolescent drivers of SUVs and pickups were at particularly high risk for fatal rollovers per vehicle mile driven compared with passenger cars (SUV: RR, 1.88 [95% CI = 1.19 to 2.96]; pickup: RR, 3.42 [95% CI = 2.29 to 5.10]). Fatality rates for teen drivers vary significantly by vehicle type. From 1999 to 2003 in the United States, fatal rollovers were significantly more likely per mile driven for teen drivers of both SUVs and pickups compared with passenger cars. However, overall fatality rates (i.e., all crash types) for teen drivers of SUVs and male drivers of pickups were lower per mile driven than for teen drivers of passenger cars. The results of this ecological analysis cannot predict the individual-level fatality risk for teens driving different vehicle types. However, the significant variability in fatality rates among SUVs, pickups, and passenger cars seen at a population level suggests that vehicle choice should be further explored as a potentially modifiable risk factor in interventions to address teen driver safety.

Hydrogen pickup mechanism of zirconium alloys

NASA Astrophysics Data System (ADS)

Couet, Adrien

Although the optimization of zirconium based alloys has led to significant improvements in hydrogen pickup and corrosion resistance, the mechanisms by which such alloy improvements occur are still not well understood. In an effort to understand such mechanisms, a systematic study of the alloy effect on hydrogen pickup is conducted, using advanced characterization techniques to rationalize precise measurements of hydrogen pickup. The hydrogen pick-up fraction is accurately measured for a specially designed set of commercial and model alloys to investigate the effects of alloying elements, microstructure and corrosion kinetics on hydrogen uptake. Two different techniques to measure hydrogen concentrations were used: a destructive technique, Vacuum Hot Extraction, and a non-destructive one, Cold Neutron Prompt Gamma Activation Analysis. The results indicate that hydrogen pickup varies not only from alloy to alloy but also during the corrosion process for a given alloy. For instance Zircaloy type alloys show high hydrogen pickup fraction and sub-parabolic oxidation kinetics whereas ZrNb alloys show lower hydrogen pickup fraction and close to parabolic oxidation kinetics. Hypothesis is made that hydrogen pickup result from the need to balance charge during the corrosion reaction, such that the pickup of hydrogen is directly related to (and indivisible of) the corrosion mechanism and decreases when the rate of electron transport or oxide electronic conductivity sigmao xe through the protective oxide increases. According to this hypothesis, alloying elements (either in solid solution or in precipitates) embedded in the oxide as well as space charge variations in the oxide would impact the hydrogen pick-up fraction by modifying sigmaox e, which drives oxidation and hydriding kinetics. Dedicated experiments and modelling were performed to assess and validate these hypotheses. In-situ electrochemical impedance spectroscopy (EIS) experiments were performed on Zircaloy-4 tubes to directly measure the evolution of sigma oxe as function of exposure time. The results show that sigmao xe decreases as function of exposure time and that its variations are directly correlated to the instantaneous hydrogen pickup fraction variations. The electron transport through the oxide layer is thus altered as the oxide grows, reasons for which are yet to be exactly determined. Preliminary results also show that sigma oxe of ZrNb alloys would be much higher compared with Zircaloy-4. Thus, it is confirmed that sigmaox e is a key parameter in the hydrogen and oxidation mechanism. Because the mechanism whereby alloying elements are incorporated into the oxide layer is critical to changing sigmao xe, the evolution of the oxidation state of two common alloying elements, Fe and Nb, when incorporated into the growing oxide layers is investigated using X-Ray Absorption Near-Edge Spectroscopy (XANES) using micro-beam synchrotron radiation on cross sectional oxide samples. The results show that the oxidation of both Fe and Nb is delayed in the oxide layer compared to that of Zr, and that this oxidation delay is related to the variations of the instantaneous hydrogen pick-up fraction with exposure time. The evolution of Nb oxidation as function of oxide depth is also compatible with space charge compensation in the oxide and with an increase in sigmaox e of ZrNb alloys compared to Zircaloys. Finally, various successively complex models from the well-known Wagner oxidation theory to the more complex effect of space charge on oxidation kinetics have been developed. The general purpose of the modeling effort is to provide a rationale for the sub-parabolic oxidation kinetics and demonstrate the correlation with hydrogen pickup fraction. It is directly demonstrated that parabolic oxidation kinetics is associated with high sigmao xe and low space charges in the oxide whereas sub-parabolic oxidation kinetics is associated with lower sigmaox e and higher space charge in the oxide. All these observations helped us to propose a general corrosion mechanism of zirconium alloys involving both oxidation and hydrogen pickup mechanism to better understand and predict the effect of alloying additions on the behavior of zirconium alloys.

Vector sensor for scanning SQUID microscopy

NASA Astrophysics Data System (ADS)

Dang, Vu The; Toji, Masaki; Thanh Huy, Ho; Miyajima, Shigeyuki; Shishido, Hiroaki; Hidaka, Mutsuo; Hayashi, Masahiko; Ishida, Takekazu

2017-07-01

We plan to build a novel 3-dimensional (3D) scanning SQUID microscope with high sensitivity and high spatial resolution. In the system, a vector sensor consists of three SQUID sensors and three pick-up coils realized on a single chip. Three pick-up coils are configured in orthogonal with each other to measure the magnetic field vector of X, Y, Z components. We fabricated some SQUID chips with one uniaxial pick-up coil or three vector pick-up coils and carried out fundamental measurements to reveal the basic characteristics. Josephson junctions (JJs) of sensors are designed to have the critical current density J c of 320 A/cm2, and the critical current I c becomes 12.5 μA for the 2.2μm × 2.2μm JJ. We carefully positioned the three pickup coils so as to keep them at the same height at the centers of all three X, Y and Z coils. This can be done by arranging them along single line parallel to a sample surface. With the aid of multilayer technology of Nb-based fabrication, we attempted to reduce an inner diameter of the pickup coils to enhance both sensitivity and spatial resolution. The method for improving a spatial resolution of a local magnetic field image is to employ an XYZ piezo-driven scanner for controlling the positions of the pick-up coils. The fundamental characteristics of our SQUID sensors confirmed the proper operation of our SQUID sensors and found a good agreement with our design parameters.

Abstracts for the International Conference on Asteroids, Comets, Meteors 1991

NASA Technical Reports Server (NTRS)

1991-01-01

Topics addressed include: chemical abundances; asteroidal belt evolution; sources of meteors and meteorites; cometary spectroscopy; gas diffusion; mathematical models; cometary nuclei; cratering records; imaging techniques; cometary composition; asteroid classification; radio telescopes and spectroscopy; magnetic fields; cosmogony; IUE observations; orbital distribution of asteroids, comets, and meteors; solar wind effects; computerized simulation; infrared remote sensing; optical properties; and orbital evolution.

Review of investigations performed in the USSR on close approaches of comets to Jupiter and the evolution of cometary orbits

NASA Technical Reports Server (NTRS)

Kazimirchak-Polonskaya, E. I.

1976-01-01

Methods are reviewed for calculating the evolution of cometary orbits with emphasis on the orbital changes that take place when comets pass within the spheres of action of giant planets. Topics discussed include: differences and difficulties in methods used for the calculation of large perturbations by Jupiter; the construction of numerical theories of motion covering the whole period of observations of each comet, allowing for planetary perturbations and the effects of nongravitational forces; and investigations of the evolution of cometary orbits over the 400 year interval 1660-2060. The classical theory of cometary capture is briefly discussed.

The Size Distribution of Jupiter-Family Cometary Nuclei

NASA Technical Reports Server (NTRS)

Weissman, Paul R.; Lowry, Stephen C.

2003-01-01

Introduction: We are continuing our program to determine the size distribution of cometary nuclei. We have compiled a catalog of 105 measurements of 57 cometary nuclei, drawn from the general literature, from our own program of CCD photometry of distant cometary nuclei (Lowry and Weissman), and from unpublished observations by colleagues. We model the cumulative size distribution of the nuclei as a power law. Previous determinations of the size distribution slope do not agree. Fernandez et al. found a slope of alpha = 2.65+/-0.25 whereas Lowry et al. and Weissman and Lowry each found a slope of alpha = 1.60+/-0.10.

Infrared molecular emissions from comets

NASA Technical Reports Server (NTRS)

Weaver, H. A.; Mumma, M. J.

1983-01-01

The possibility of detecting IR molecular line emission from cometary parent molecules is explored. Due to the non-LTE conditions in the inner coma and the large amount of near IR solar flux, IR fluorescence will be a significant source of cometary emission and, in fact, will dominate the grain radiation in a sufficiently high resolution instrument. The detection of this line emission will be difficult due to absorption in the terrestrial atmosphere, but it appears possible to measure cometary H2O emission from airplane altitudes. As IR molecular line emission represents one of the few promising methods of detecting cometary parent molecules directly, further research on this problem should be vigorously pursued.

P/2006 HR30 (Siding Spring): A Low-activity Comet in Near-Earth Space

NASA Technical Reports Server (NTRS)

Hicks, Michael D.; Bauer, James M.

2007-01-01

The low cometary activity of P/2006 HR30 (Siding Spring) allowed a unique opportunity to study the nucleus of a periodic comet while near perihelion. P/2006 HR30 was originally targeted as a potential extinct comet, and we measured spectral reflectance and dust production using long-slit CCD spectroscopy and wide-field imaging obtained at the Palomar Mountain 200 inch telescope on 2006 August 3 and 4. The dust production Afp = 19.7 +/- 0.4 cm and mass-loss rate Q(dust) 4.1 +/- 0.1 kg/sec of the comet were approximately 2 orders of magnitude dust less than 1P/Halley at similar heliocentric distance. The VRI colors derived from the spectral reflectance were compared to Kuiper Belt objects, Centaurs, and other cometary nuclei. We found that the spectrum of P/2006 HR30 was consistent with other comets. However, the outer solar system bodies have a color distribution statistically distinct from cometary nuclei. It is our conjecture that cometary activity, most likely the reaccretion of ejected cometary dust, tends to moderate and mute the visible colors of the surface of cometary nuclei.

Cometary coma chemical composition (C4) mission. [Abstract only

NASA Technical Reports Server (NTRS)

Carle, G. C.; Clark, B. C.; Niemann, H. B.; Alexander, M.; Knocke, P. C.; O'Hara, B. J.

1994-01-01

Cometary missions are of enormous fundamental importance for many different space science disciplines, including exobiology. Comets are presumed relics of the earliest, most primitive material in the solar nebula and are related to the planetesimals. They undoubtedly provided a general enrichment of volatiles to the inner solar system (contributing to atmospheres and oceans) and may have been key to the origin of life. A Discovery class, comet rendezvous mission, the Cometary Coma Chemical Composition (C4) Mission, was selected for further study by NASA earlier this year. The C4 Mission is a highly focused and usefully-limited subset of the Cometary Rendezvous Asteroid Flyby (CRAF) Mission, concentrating exclusively on measurements which will lead to an understanding of the chemical composition and make-up of the cometary nucleus. The scientific goals of the Cometary Coma Chemical Composition (C4) Mission are to rendezvous with a short-period comet and (1) to determine the elemental, chemical, and isotopic composition of the nucleus and (2) to characterize the chemical and isotopic nature of its atmosphere. Further, it is a goal to obtain preliminary data on the development of the coma (dust and gas composition) as a function of time and orbital position.

A Substantial Plume of Escaping Planetary Ions in the MSE Northern Hemisphere Observed by MAVEN

NASA Astrophysics Data System (ADS)

Dong, Y.; Fang, X.; Brain, D. A.; McFadden, J. P.; Halekas, J. S.; Connerney, J. E. P.; Curry, S.; Harada, Y.; Luhmann, J. G.; Jakosky, B. M.

2015-12-01

The Mars-solar wind interaction accelerates and transports planetary ions away from Mars through a number of processes, including pick-up by the electromagnetic fields. The Mars Atmospheric and Volatile EvolutioN (MAVEN) spacecraft has frequently detected strong escaping planetary ion fluxes in both tailward and upstream solar wind motional electric field directions since the beginning of its science phase in November 2014. Our statistical study using three-month MAVEN data from November 2014 through February 2015 illustrates a substantial plume-like escaping planetary ion population organized by the upstream electric field with strong fluxes widely distributed in the northern hemisphere of the Mars-Sun-Electric-field (MSE) coordinate system, which is generally consistent with model predictions. The plume constitutes an important planetary ion escape channel from the Martian atmosphere in addition to the tailward escape. The >25eV O+ escape rate through the plume is estimated to be ~35% of the tailward escape and ~25% of the total escape. We will compare the dynamics of the plume and tailward escaping ions based on their velocity-space distributions with respect to the electromagnetic fields. We will also discuss the variations of the plume characteristics between different ion species (O+, O2+, and CO2+) and from the effect of different solar wind and interplanetary magnetic field (IMF) conditions.

Skills and offensive tactics used in pick-up basketball games.

PubMed

Wang, Jianyu; Liu, Wenhao; Moffit, Jeffrey

2009-10-01

The purpose of this study was to describe skills and offensive tactics frequently used in pick-up basketball games. 65 participants were recruited from public basketball courts. An observational instrument was developed to analyze the performances of pick-up games. Participants' performances were videotaped and coded. Results indicated that the passing skills most frequently observed in the games were chest pass, overhead pass, and bounce pass. For dribbling, crossover dribble and change-of-pace dribble were frequently observed. Jump shot, set shot, and layup were also frequently used. The offensive tactics frequently used included drive, cut, and set screen. The study may be beneficial for helping young people prepare to play pick-up basketball games.

Solar wind interaction with dusty plasmas produces instabilities and solitary structures

NASA Astrophysics Data System (ADS)

Saleem, H.; Ali, S.

2017-12-01

It is pointed out that the solar wind interaction with dusty magnetospheres of the planets can give rise to purely growing instabilities as well as nonlinear electric field structures. Linear dispersion relation of the low frequency electrostatic ion-acoustic wave (IAW) is modified in the presence of stationary dust and its frequency becomes larger than its frequency in usual electron ion plasma even if ion temperature is equal to the electron temperature. This dust-ion-acoustic wave (DIAW) either becomes a purely growing electrostatic instability or turns out to be the modified dust-ion-acoustic wave (mDIAW) depending upon the magnitude of shear flow scale length and its direction. Growth rate of shear flow-driven electrostatic instability in a plasma having negatively charged stationary dust is larger than the usual D'Angelo instability of electron-ion plasma. It is shown that shear modified dust ion acoustic wave (mDIAW) produces electrostatic solitons in the nonlinear regime. The fluid theory predicts the existence of electrostatic solitons in the dusty plasmas in those regions where the inhomogeneous solar wind flow is parallel to the planetary or cometary magnetic field lines. The amplitude and width of the solitary structure depends upon dust density and magnitude of shear in the flow. This is a general theoretical model which is applied to dusty plasma of Saturn's F-ring for illustration.

Charge-exchange coupling between pickup ions across the heliopause and its effect on energetic neutral hydrogen flux

DOE PAGES

Zirnstein, Eric J.; Heerikhuisen, J.; Zank, G. P.; ...

2014-02-24

Pickup ions (PUIs) appear to play an integral role in the multi-component nature of the plasma in the interaction between the solar wind (SW) and local interstellar medium (LISM). Three-dimensional (3D) MHD simulations with a kinetic treatment for neutrals and PUIs are currently still not viable. In light of recent energetic neutral atom (ENA) observations by the Interstellar Boundary EXplorer, the purpose of this paper is to illustrate the complex coupling between PUIs across the heliopause (HP) as facilitated by ENAs using estimates of PUI properties extracted from a 3D MHD simulation of the SW-LISM interaction with kinetic neutrals. First,more » we improve upon the multi-component treatment of the inner heliosheath (IHS) plasma from Zank et al. by including the extinction of PUIs through charge-exchange. We find a significant amount of energy is transferred away from hot, termination shock-processed PUIs into a colder, "freshly injected" PUI population. Second, we extend the multi-component approach to estimate ENA flux from the outer heliosheath (OHS), formed from charge-exchange between interstellar hydrogen atoms and energetic PUIs. These PUIs are formed from ENAs in the IHS that crossed the HP and experienced charge-exchange. Lastly, our estimates, based on plasma-neutral simulations of the SW-LISM interaction and a post-processing analysis of ENAs and PUIs, suggest the majority of flux visible at 1 AU from the front of the heliosphere, between ~0.02 and 10 keV, originates from OHS PUIs, indicating strong coupling between the IHS and OHS plasmas through charge-exchange.« less

THE IBEX RIBBON AND THE PICKUP ION RING STABILITY IN THE OUTER HELIOSHEATH. I. THEORY AND HYBRID SIMULATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Florinski, V.; Heerikhuisen, J.; Niemiec, J.

2016-08-01

The nearly circular band of energetic neutral atom emission dominating the field of view of the Interplanetary Boundary Explorer ( IBEX ) satellite, is most commonly attributed to the effect of charge exchange of secondary pickup ions (PUIs) gyrating about the magnetic field in the outer heliosheath and the interstellar space beyond. Several models for the PUI dynamics of this mechanism have been proposed, each requiring either strong or weak scattering of the initial pitch angle. Conventional wisdom states that ring distributions tend to generate waves and scatter onto a shell on timescales too short for charge exchange to occur.more » We performed a careful study of ring and thin shell proton distribution stability using theoretical tools and hybrid plasma simulations. We show that the kinetic behavior of a freshly injected proton ring is a far more complicated process than previously thought. In the presence of a warm Maxwellian core, narrower rings could be more stable than broader toroidal distributions. The scattered rings possess a fine structure that can only be revealed using very large numbers of macroparticles in a simulation. It is demonstrated that a “stability gap” in ring temperature exists where the protons could retain large gyrating anisotropies for years, and the wave activity could remain below the level of the ambient magnetic fluctuations in interstellar space. In the directions away from the ribbon, however, a partial shell distribution is more likely to be unstable, leading to significant scattering into one hemisphere in velocity space. The process is accompanied by turbulence production, which is puzzling given the very low level of magnetic fluctuations measured in the outer heliosheath by Voyager 1 .« less

The Role of Pickup Ion Dynamics Outside of the Heliopause in the Limit of Weak Pitch Angle Scattering: Implications for the Source of the IBEX Ribbon.

PubMed

Zirnstein, E J; Heerikhuisen, J; Dayeh, M A

2018-01-01

We present a new model of the Interstellar Boundary Explorer ( IBEX ) ribbon based on the secondary energetic neutral atom (ENA) mechanism, under the assumption that there is negligible pitch angle scattering of pickup ions (PUIs) outside the heliopause. Using the results of an MHD-plasma/kinetic-neutral simulation of the heliosphere, we generate PUIs in the outer heliosheath, solve their transport using guiding center theory, and compute ribbon ENA fluxes at 1 AU. We implement several aspects of the PUI dynamics, including (1) parallel motion along the local interstellar magnetic field (ISMF), (2) advective transport with the interstellar plasma, (3) the mirror force acting on PUIs propagating along the ISMF, and (4) betatron acceleration of PUIs as they are advected within an increasing magnetic field towards the heliopause. We find that ENA fluxes at 1 AU are reduced when PUIs are allowed to move along the ISMF, and ENA fluxes are reduced even more by the inclusion of the mirror force, which pushes particles away from IBEX lines-of-sight. Inclusion of advection and betatron acceleration do not result in any significant change in the ribbon. Interestingly, the mirror force reduces the ENA fluxes from the inner edge of the ribbon more than its outer edge, effectively reducing the ribbon's width by ∼6° and increasing its radius projected on the sky. This is caused by the asymmetric draping of the ISMF around the heliopause, such that ENAs from the ribbon's inner edge originate closer to the heliopause, where the mirror force is strongest.

The Role of Pickup Ion Dynamics Outside of the Heliopause in the Limit of Weak Pitch Angle Scattering: Implications for the Source of the IBEX Ribbon

NASA Astrophysics Data System (ADS)

Zirnstein, E. J.; Heerikhuisen, J.; Dayeh, M. A.

2018-03-01

We present a new model of the Interstellar Boundary Explorer (IBEX) ribbon based on the secondary energetic neutral atom (ENA) mechanism, under the assumption that there is negligible pitch angle scattering of pickup ions (PUIs) outside the heliopause. Using the results of an MHD-plasma/kinetic-neutral simulation of the heliosphere, we generate PUIs in the outer heliosheath, solve their transport using guiding center theory, and compute ribbon ENA fluxes at 1 au. We implement several aspects of the PUI dynamics, including (1) parallel motion along the local interstellar magnetic field (ISMF), (2) advective transport with the interstellar plasma, (3) the mirror force acting on PUIs propagating along the ISMF, and (4) betatron acceleration of PUIs as they are advected within an increasing magnetic field toward the heliopause. We find that ENA fluxes at 1 au are reduced when PUIs are allowed to move along the ISMF, and ENA fluxes are reduced even more by the inclusion of the mirror force, which pushes particles away from IBEX lines of sight. Inclusion of advection and betatron acceleration do not result in any significant change in the ribbon. Interestingly, the mirror force reduces the ENA fluxes from the inner edge of the ribbon more than those from its outer edge, effectively reducing the ribbon’s width by ∼6° and increasing its radius projected on the sky. This is caused by the asymmetric draping of the ISMF around the heliopause, such that ENAs from the ribbon’s inner edge originate closer to the heliopause, where the mirror force is strongest.

Investigating Systematic Errors of the Interstellar Flow Longitude Derived from the Pickup Ion Cutoff

NASA Astrophysics Data System (ADS)

Taut, A.; Berger, L.; Drews, C.; Bower, J.; Keilbach, D.; Lee, M. A.; Moebius, E.; Wimmer-Schweingruber, R. F.

2017-12-01

Complementary to the direct neutral particle measurements performed by e.g. IBEX, the measurement of PickUp Ions (PUIs) constitutes a diagnostic tool to investigate the local interstellar medium. PUIs are former neutral particles that have been ionized in the inner heliosphere. Subsequently, they are picked up by the solar wind and its frozen-in magnetic field. Due to this process, a characteristic Velocity Distribution Function (VDF) with a sharp cutoff evolves, which carries information about the PUI's injection speed and thus the former neutral particle velocity. The symmetry of the injection speed about the interstellar flow vector is used to derive the interstellar flow longitude from PUI measurements. Using He PUI data obtained by the PLASTIC sensor on STEREO A, we investigate how this concept may be affected by systematic errors. The PUI VDF strongly depends on the orientation of the local interplanetary magnetic field. Recently injected PUIs with speeds just below the cutoff speed typically form a highly anisotropic torus distribution in velocity space, which leads to a longitudinal transport for certain magnetic field orientation. Therefore, we investigate how the selection of magnetic field configurations in the data affects the result for the interstellar flow longitude that we derive from the PUI cutoff. Indeed, we find that the results follow a systematic trend with the filtered magnetic field angles that can lead to a shift of the result up to 5°. In turn, this means that every value for the interstellar flow longitude derived from the PUI cutoff is affected by a systematic error depending on the utilized magnetic field orientations. Here, we present our observations, discuss possible reasons for the systematic trend we discovered, and indicate selections that may minimize the systematic errors.

Beam current sensor

DOEpatents

Kuchnir, M.; Mills, F.E.

1984-09-28

A current sensor for measuring the dc component of a beam of charged particles employs a superconducting pick-up loop probe, with twisted superconducting leads in combination with a Superconducting Quantum Interference Device (SQUID) detector. The pick-up probe is in the form of a single-turn loop, or a cylindrical toroid, through which the beam is directed and within which a first magnetic flux is excluded by the Meisner effect. The SQUID detector acts as a flux-to-voltage converter in providing a current to the pick-up loop so as to establish a second magnetic flux within the electrode which nulls out the first magnetic flux. A feedback voltage within the SQUID detector represents the beam current of the particles which transit the pick-up loop. Meisner effect currents prevent changes in the magnetic field within the toroidal pick-up loop and produce a current signal independent of the beam's cross-section and its position within the toroid, while the combination of superconducting elements provides current measurement sensitivities in the nano-ampere range.

Radially Focused Eddy Current Sensor for Detection of Longitudinal Flaws in Metallic Tubes

NASA Technical Reports Server (NTRS)

Wincheski, Russell A. (Inventor); Simpson, John W. (Inventor); Fulton, James P. (Inventor); Nath, Shridhar C. (Inventor); Todhunter, Ronald G. (Inventor); Namkung, Min (Inventor)

1999-01-01

A radially focused eddy current sensor detects longitudinal flaws in a metal tube. A drive coil induces eddy currents within the wall of the metal tube. A pick-up cod is spaced apart from the drive coil along the length of the metal tube. The pick@up coil is positioned with one end thereof lying adjacent the wall of the metal tube such that the pick-up coil's longitudinal axis is perpendicular to the wall of the metal tube. To isolate the pick-up coil from the magnetic flux of the drive coil and the flux from the induced eddy currents. except the eddy currents diverted by a longitudinal flaw. an electrically conducting material high in magnetic permeability surrounds all of the pick-up coil except its one end that is adjacent the walls of the metal tube. The electrically conducting material can extend into and through the drive coil in a coaxial relationship therewith.

Beam current sensor

DOEpatents

Kuchnir, Moyses; Mills, Frederick E.

1987-01-01

A current sensor for measuring the DC component of a beam of charged particles employs a superconducting pick-up loop probe, with twisted superconducting leads in combination with a Superconducting Quantum Interference Device (SQUID) detector. The pick-up probe is in the form of a single-turn loop, or a cylindrical toroid, through which the beam is directed and within which a first magnetic flux is excluded by the Meisner effect. The SQUID detector acts as a flux-to-voltage converter in providing a current to the pick-up loop so as to establish a second magnetic flux within the electrode which nulls out the first magnetic flux. A feedback voltage within the SQUID detector represents the beam current of the particles which transit the pick-up loop. Meisner effect currents prevent changes in the magnetic field within the toroidal pick-up loop and produce a current signal independent of the beam's cross-section and its position within the toroid, while the combination of superconducting elements provides current measurement sensitivites in the nano-ampere range.

A Comparative View of X-rays from the Solar System

NASA Technical Reports Server (NTRS)

Bhardwaj, Anil; Elsner, Ron; Gladstone, Randy; Cravens, Tom; Waite, Hunter; Branduardi-Raymont, Graziella; Ostgaard, Nikolai; Dennerl, Konrad; Lisse, Carey; Kharchenko, Vasili

2005-01-01

With the advent of sophisticated X-ray observatories, viz., Chandra and XMM-Newton, the field of planetary X-ray astronomy is advancing at a faster pace. Several new solar system objects are now know to shine in X-rays at energies generally below 2 keV. Jupiter, Saturn, and Earth, all three magnetized planets, have been observed by Chandra and XMM-Newton. At Jupiter, both auroral and non-auroral disk X-ray emissions have been observed. The first soft X-ray observation of Earth's aurora by Chandra shows that it is highly variable. X-rays have been detected from Saturn's disk, but no convincing evidence of X-ray aurora has been seen. Several comets have been observed in X-rays by Chandra and XMM-Newton. Cometary X-rays are produced due to change exchange of solar wind ions with cold cometary neutrals. Soft X-rays have also been observed from Venus, Mars, Moon, Io, Europa, Io plasma torus, and heliosphere. The non-auroral X-ray emissions from Jupiter, Saturn, and Earth, and those from sunlit disk of Mars, Venus, and Moon are produced due to scattering of solar X-rays. The spectral characteristics of X-ray emission from comets, heliosphere, darkside of Moon, and Martian halo are quite similar, but they appear to be quite different from those of Jovian auroral X-rays. The X- ray aurora on Earth is generated by electron bremsstrahlung and on Jupiter by precipitation of highly-ionized energetic heavy ions. In this paper we will present a comparative overview of X-ray emission from different solar system objects and make an attempt to synthesize a coherent picture.

Capacitively coupled pickup in MCP-based photodetectors using a conductive metallic anode

NASA Astrophysics Data System (ADS)

Angelico, E.; Seiss, T.; Adams, B.; Elagin, A.; Frisch, H.; Spieglan, E.

2017-02-01

We have designed and tested a robust 20×20 cm2 thin metal film internal anode capacitively coupled to an external array of signal pads or micro-strips for use in fast microchannel plate photodetectors. The internal anode, in this case a 10 nm-thick NiCr film deposited on a 96% pure Al2O3 3 mm-thick ceramic plate and connected to HV ground, provides the return path for the electron cascade charge. The multi-channel pickup array consists of a printed-circuit card or glass plate with metal signal pickups on one side and the signal ground plane on the other. The pickup can be put in close proximity to the bottom outer surface of the sealed photodetector, with no electrical connections through the photodetector hermetic vacuum package other than a single ground connection to the internal anode. Two pickup patterns were tested using a small commercial MCP-PMT as the signal source: 1) parallel 50 Ω 25-cm-long micro-strips with an analog bandwidth of 1.5 GHz, and 2) a 20×20 cm2 array of 2-dimensional square 'pads' with sides of 1.27 cm or 2.54 cm. The rise-time of the fast input pulse is maintained for both pickup patterns. For the pad pattern, we observe 80% of the directly coupled amplitude. For the strip pattern we measure 34% of the directly coupled amplitude on the central strip of a broadened signal. The physical decoupling of the photodetector from the pickup pattern allows easy customization for different applications while maintaining high analog bandwidth.

Uptake of methanol on mixed HNO3/H2O clusters: An absolute pickup cross section

NASA Astrophysics Data System (ADS)

Pysanenko, A.; Lengyel, J.; Fárník, M.

2018-04-01

The uptake of atmospheric oxidized organics on acid clusters is relevant for atmospheric new particle formation. We investigate the pickup of methanol (CH3OH) on mixed nitric acid-water clusters (HNO3)M(H2O)N by a combination of mass spectrometry and cluster velocity measurements in a molecular beam. The mass spectra of the mixed clusters exhibit (HNO3)m(H2O)nH+ series with m = 0-3 and n = 0-12. In addition, CH3OH.(HNO3)m(H2O)nH+ series with very similar patterns appear in the spectra after the methanol pickup. The velocity measurements prove that the undoped (HNO3)m(H2O)nH+ mass peaks in the pickup spectra originate from the neutral (HNO3)M(H2O)N clusters which have not picked up any CH3OH molecule, i.e., methanol has not evaporated upon the ionization. Thus the fraction of the doped clusters can be determined and the mean pickup cross section can be estimated, yielding σs ¯ ≈ 20 Å2. This is compared to the lower estimate of the mean geometrical cross section σg ¯ ≈ 60 Å2 obtained from the theoretical cluster geometries. Thus the "size" of the cluster corresponding to the methanol pickup is at least 3-times smaller than its geometrical size. We have introduced a method which can yield the absolute pickup cross sections relevant to the generation and growth of atmospheric aerosols, as illustrated in the example of methanol and nitric acid clusters.

Recent researches into solid bodies and magnetic fields in the solar system; Proceedings of the Topical Meeting and Symposium, Ottawa, Canada, May 16-June 2, 1982

NASA Technical Reports Server (NTRS)

Vette, J. I. (Editor); Runcorn, S. K. (Editor); Gruen, E. (Editor); Mcdonnell, J. A. M.

1982-01-01

Topics discussed include the magnetic history of the early solar system, impact processes in solid bodies (e.g., meteoroids and asteroids), and topics related to cometary missions. The section devoted to cometary missions lays particular stress on missions to Comet Halley; attention is given to such aspects of these missions as the investigation of hypervelocity impact on the Giotto Halley mission dust shield, the detection of energetic cometary and solar particles by the EPONA instrument on the Giotto mission, the dust hazard near Comet Halley in regard to the Vega project, and cometary ephemerides for spacecraft flyby missions.

Infrared molecular emissions from comets

NASA Technical Reports Server (NTRS)

Weaver, H. A.; Mumma, M. J.

1984-01-01

The possibility of detecting IR molecular line emission from cometary parent molecules is explored. Due to the non-LTE conditions in the inner coma and the large amount of near IR solar flux, IR fluorescence will be a significant source of cometary emission and, in fact, will dominate the grain radiation in a sufficiently high resolution instrument. The detection of this line emission will be difficult due to absorption in the terrestrial atmosphere, but it appears possible to measure cometary H2O emission from airplane altitudes. As IR molecular line emission represents one of the few promising methods of detecting cometary parent molecules directly, further research on this problem should be vigorously pursued. Previously announced in STAR as N83-30344

Cometary Amino Acids from the STARDUST Mission

NASA Technical Reports Server (NTRS)

Cook, Jamie Elsila

2009-01-01

NASA's Stardust spacecraft returned samples from comet 81 P/WiId 2 to Earth in January 2006. Examinations of the organic compounds in cometary samples can reveal information about the prebiotic organic inventory present on the early Earth and within the early Solar System, which may have contributed to the origin of life. Preliminary studies of Stardust material revealed the presence of a suite of organic compounds including several amines and amino acids, but the origin of these compounds (cometary vs. terrestrial contamination) could not be identified. We have recently measured the carbon isotopic ratios of these amino acids to determine their origin, leading to the first detection of a cometary amino acid.

Hand and Grasp Selection in a Preferential Reaching Task: The Effects of Object Location, Orientation, and Task Intention.

PubMed

Scharoun, Sara M; Scanlan, Kelly A; Bryden, Pamela J

2016-01-01

As numerous movement options are available in reaching and grasping, of particular interest are what factors influence an individual's choice of action. In the current study a preferential reaching task was used to assess the propensity for right handers to select their preferred hand and grasp a coffee mug by the handle in both independent and joint action object manipulation contexts. Mug location (right-space, midline, and left-space) and handle orientation (toward, away, to left, and to right of the participant) varied in four tasks that differed as a function of intention: (1) pick-up (unimanual, independent); (2) pick-up and pour (bimanual, independent); (3) pick-up and pass (unimanual, joint action); and (4) pick-up, pour and pass (bimanual, joint action). In line with previous reports, a right-hand preference for unimanual tasks was observed. Furthermore, extending existing literature to a preferential reaching task, role differentiation between the hands in bimanual tasks (i.e., preferred hand mobilizing, non-preferred hand stabilizing) was displayed. Finally, right-hand selection was greatest in right space, albeit lower in bimanual tasks compared to what is typically reported in unimanual tasks. Findings are attributed to the desire to maximize biomechanical efficiency in reaching. Grasp postures were also observed to reflect consideration of efficiency. More specifically, within independent object manipulation (pick-up; pick-up and pour) participants only grasped the mug by the handle when it afforded a comfortable posture. Furthermore, in joint action (pick-up and pass; pick-up, pour and pass), the confederate was only offered the handle if the intended action of the confederate was similar or required less effort than that of the participant. Together, findings from the current study add to our knowledge of hand and grasp selection in unimanual and bimanual object manipulation, within the context of both independent and joint action tasks.

Multi-species hybrid modeling of plasma interactions at Io and Europa

NASA Astrophysics Data System (ADS)

Sebek, O.; Travnicek, P. M.; Walker, R. J.; Hellinger, P.

2017-12-01

We study the plasma interactions of Galilean satellites, Io and Europa, by means of multi-species global hybrid simulations. For both satellites we consider multi-species background plasma composed of oxygen and sulphur ions and multi-component neutral atmospheres. We consider ionization processes of the neutral atmosphere which is then a source of dense population of pick-up ions. We apply variable background plasma conditions (density, temperature, magnetic field magnitude and orientation) in order to cover the variability in conditions experienced by the satellites when located in different regions of the Jovian plasma torus. We examine global structure of the interactions, formation of Alfvén wings, development of temperature anisotropies and corresponding instabilities, and the fine phenomena caused by the multi-specie nature of the plasma. The results are in good agreement with in situ measurements of magnetic field and plasma density made by the Galileo spacecraft.

Desorption electrospray ionization mass spectrometry of DNA nucleobases: implications for a liquid film model.

PubMed

Qiu, Bo; Luo, Hai

2009-05-01

Desorption electrospray ionization (DESI) mass spectrometry has been implemented on a commercial ion-trap mass spectrometer and used to optimize mass spectrometric conditions for DNA nucleobases: adenine, cytosine, thymine, and guanine. Experimental parameters including spray voltage, distance between mass spectrometer inlet and the sampled spot, and nebulizing gas inlet pressure were optimized. Cluster ions including some magic number clusters of nucleobases were observed for the first time using DESI mass spectrometry. The formation of the cluster species was found to vary with the nucleobases, acidification of the spray solvent, and the deposited sample amount. All the experimental results can be explained well using a liquid film model based on the two-step droplet pick-up mechanism. It is further suggested that solubility of the analytes in the spray solvent is an important factor to consider for their studies by using DESI. 2009 John Wiley & Sons, Ltd.

Laboratory Studies of Cometary Materials - Continuity Between Asteroid and Comet

NASA Technical Reports Server (NTRS)

Messenger, Scott; Walker, Robert M.

2015-01-01

Laboratory analysis of cometary samples have been enabled by collection of cometary dust in the stratosphere by high altitude aircraft and by the direct sampling of the comet Wild-2 coma by the NASA Stardust spacecraft. Cometary materials are composed of a complex assemblage of highly primitive, unprocessed interstellar and primordial solar system materials as well as a variety of high temperature phases that must have condensed in the inner regions of the protoplanetary disk. These findings support and contradict conclusions of comet properties based solely on astronomical observations. These sample return missions have instead shown that there is a continuity of properties between comets and asteroids, where both types of materials show evidence for primitive and processed materials. Furthermore, these findings underscore the importance and value of direct sample return. There will be great value in comparing the findings of the Stardust cometary coma sample return mission with those of future asteroid surface sample returns OSIRIS-REx and Hayabusa II as well as future comet nucleus sample returns.

Plasma observations at venus with galileo.

PubMed

Frank, L A; Paterson, W R; Ackerson, K L; Coroniti, F V; Vasyliunas, V M

1991-09-27

Plasma measurements were obtained with the Galileo spacecraft during an approximately 3.5-hour interval in the vicinity of Venus on 10 February 1990. Several crossings of the bow shock in the local dawn sector were recorded before the spacecraft passed into the solar wind upstream from this planet. Although observations of ions of the solar wind and the postshock magnetosheath plasmas were not possible owing to the presence of a sunshade for thermal protection of the instrument, solar wind densities and bulk speeds were determined from the electron velocity distributions. A magnetic field-aligned distribution of hotter electrons or ;;strahl'' was also found in the solar wind. Ions streaming into the solar wind from the bow shock were detected. Electron heating at the bow shock,

In-situ observations of a bi-modal ion distribution in the outer coma of comet P/Halley

NASA Technical Reports Server (NTRS)

Thomsen, M. F.; Feldman, W. C.; Wilken, B.; Jockers, K.; Stuedemann, W.

1987-01-01

Observations obtained by the Johnstone Plasma Analyzer on the Giotto fly-by of comet Halley showed a fairly sudden decrease in the count rate of energetic (about 30 KeV) water-group ions inside about 500,000 km from the nucleus. This decrease was accompanied by the appearance of a new water-group ion population at slightly lower energies (less than 10 KeV). Close inspection reveals that this lower-energy peak was also present somewhat earlier in the postshock flow but only became prominent near the sudden transition just described. It is shown that the observed bimodal ion distribution is well explained in terms of the velocity history of the accreting solar wind flow in the outer coma. The decline in count rate of the energetic pick-up distribution is due to a relatively sudden slowing of the bulk flow there and not to a loss of particles. Hence, charge-exchange cooling of the flow is probably not important at these distances from the nucleus. The observations suggest that pitch-angle scattering is fairly efficient at least after the bow shock, but that energy diffusion is probably not very efficient.

Cometary Dust: The Diversity of Primitive Matter

NASA Technical Reports Server (NTRS)

Wooden, D. H.; Ishiiii, H. A.; Zolensky, M. E.

2017-01-01

The connections between comet dust and primitive chondrites from asteroids has strengthened considerably over the past decade. Understanding the importance of the connections between Stardust samples and chondrites requires geochemistry lingo as well as a perspective of other cometary dust samples besides Stardust. We present the principal findings of an extensive review prepared for by us for the June 2016 "Cometary Science After Rosetta" meeting at The Royal Society, London.

On the dayside mantle region around those nonmagnetic solar system bodies which have ionosphere

NASA Astrophysics Data System (ADS)

Szego, K.; Sagdeev, R. Z.; Shapiro, V. D.; Shevchenko, V. I.

1992-08-01

The properties of the plasma environments close to the dayside obstacle boundary of nonmagnetic planets with ionospheres are compared to study the effects of turbulent wave-particle processes. Data are examined from Pioneer-Venus, Phobos-2, and Giotto/Vega data regarding Venus, Mars, and Comet P/Halley, respectively. The equivalent of the MHD obstacle boundary on the dayside is investigated with attention given to the wave-particle processes. A magnetic cavity is found to exist in observations and theory within the magnetosphere where the solar-wind magnetic field does not penetrate. The ionosphere penetrates the boundary, and a region is defined where the solar wind and the planetary/cometary plasma overlap. The region is called a mantle region in which: (1) the solar wind decelerates and the magnetic field piles up; (2) two counterstreaming ion populations exist; and (3) solar wind and body ions interact via wave-particle interaction.

Four-fluid MHD Simulations of the Plasma and Neutral Gas Environment of Comet Churyumov-Gerasimenko Near Perihelion

NASA Astrophysics Data System (ADS)

Huang, Z.; Toth, G.; Gombosi, T.; Jia, X.; Rubin, M.; Fougere, N.; Tenishev, V.; Combi, M.; Bieler, A.; Hansen, K.; Shou, Y.; Altwegg, K.

2015-10-01

We develop a 3-D four fluid model to study the plasma environment of comet Churyumov- Gerasimenko (CG), which is the target of the Rosetta mission. Our model is based on BATS-R-US within the SWMF (Space Weather Modeling Framework) that solves the governing multifluid MHD equations and and the Euler equations for the neutral gas fluid. These equations describe the behavior and interactions of the cometary heavy ions, the solar wind protons, the electrons, and the neutrals. This model incorporates mass loading processes, including photo and electron impact ionization, furthermore taken into account are charge exchange, dissociative ion-electron recombination, as well as collisional interactions between different fluids. We simulate the near nucleus plasma and neutral gas environment with a realistic shape model of CG near perihelion and compare our simulation results with Rosetta observations.

Four-fluid MHD Simulations of the Plasma and Neutral Gas Environment of Comet Churyumov-Gerasimenko Near Perihelio

NASA Astrophysics Data System (ADS)

Huang, Z.; Toth, G.; Gombosi, T. I.; Jia, X.; Rubin, M.; Hansen, K. C.; Fougere, N.; Bieler, A. M.; Shou, Y.; Altwegg, K.; Combi, M. R.; Tenishev, V.

2015-12-01

The neutral and plasma environment is critical in understanding the interaction of comet Churyumov-Gerasimenko (CG), the target of the Rosetta mission, and the solar wind. To serve this need and support the Rosetta mission, we develop a 3-D four fluid model, which is based on BATS-R-US within the SWMF (Space Weather Modeling Framework) that solves the governing multi-fluid MHD equations and the Euler equations for the neutral gas fluid. These equations describe the behavior and interactions of the cometary heavy ions, the solar wind protons, the electrons, and the neutrals. This model incorporates different mass loading processes, including photo and electron impact ionization, charge exchange, dissociative ion-electron recombination, and collisional interactions between different fluids. We simulate the near nucleus plasma and neutral gas environment near perihelion with a realistic shape model of CG and compare our simulation results with Rosetta observations.

Formation of methyl formate in comets by irradiation of methanol-bearing ices

NASA Astrophysics Data System (ADS)

Modica, P.; Palumbo, M. E.; Strazzulla, G.

2012-12-01

Methyl formate is a complex organic molecule considered potentially relevant as precursor of biologically active molecules. It has been observed in several astrophysical environments, such as hot cores, hot corinos, and comets. The processes that drive the formation of molecules in cometary ices are poorly understood. In particular it is not yet clear if molecules are directly accreted from the pre-solar nebula to form comets or are formed after accretion. The present work analyzes the possible role of cosmic ion irradiation and radioactive decay in methyl formate formation in methanol-bearing ices. The results indicate that cosmic ion irradiation can account for about 12% of the methyl formate observed in comet Hale-Bopp, while radioactive decay can account for about 6% of this amount. The need of new data coming from earth based and space observational projects as well as from laboratory experiments is outlined.

Chemical composition of the semi-volatile grains of comet 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Wurz, Peter; Altwegg, Kathrin; Balsiger, Hans; Berthelier, Jean-Jacques; Bieler, André; Calmonte, Ursina; De Keyser, Johan; Fiethe, Björn; Fuselier, Stefan; Gasc, Sébastien; Gombosi, Tamas; Jäckel, Annette; Korth, Axel; Le Roy, Lena; Mall, Urs; Rème, Henri; Rubin, Martin; Tzou, Chia-Yu

2017-04-01

The European Space Agency's Rosetta spacecraft (Glassmeier et al., 2007) has been in orbit of the comet 67P/Churyumov-Gerasimenko (67P/C-G) since August 2014. On board is the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) instrument suite (Balsiger et al., 2007). ROSINA consists of two mass spectrometers, the Double Focusing Mass Spectrometer (DFMS) and the Reflectron-type Time-Of-Flight (RTOF) (Scherer et al., 2006), as well as the COmet Pressure Sensor (COPS). ROSINA is designed to detect and monitor the neutral gas and thermal plasma environment in the comet's coma by in situ investigation. The two mass spectrometers have high dynamic ranges and complement each other with high mass resolution (DFMS) and high time resolution and large mass range (RTOF). Especially the unprecedented sensitivity and mass resolution of DFMS together with the large mass range of RTOF allow determining precisely light species (e.g. isotopologues) as well as detecting heavy organic species. The pressure sensor COPS measures total gas densities, bulk velocities, and gas temperatures. ROSINA has been collecting data on the composition of the coma and activity of the comet from 3.5 AU to pericentre and out again to 3.5 AU. The Rosetta mission presents a unique opportunity to directly sample the parent species in the thin cometary atmosphere of a Kuiper-belt object at distances in excess of 2.5 AU from the Sun all the way to the pericentre of the cometary orbit at 1.24 AU. The ROSINA experiment continuously measured the chemical composition of the gases in the cometary coma. Occasionally, a dust grain of cometary origin enters the ion source of a ROSINA instrument where the volatile part evaporates since these ion sources are hot. We will report on the first measurements of the volatile inventory of such dust grains. Volatile release from cometary dust grains was observed with all three ROSINA instruments on several occasions. Because the volatile content of such a dust grain is completely evaporated in such an ion source after a few 100 seconds, the RTOF instrument is best suited for the investigation of its chemical composition since several complete mass spectra are recorded during this time. The rate of dust grains recorded in RTOF is small, and we report on the collection and analysis of 9 dust grains during the October 2014 to July 2016 time period. It is estimated that these grains contain about 1E-15 g of volatiles, which would correspond to a grain of the order of 100 nm in size if made up of volatiles alone. We fitted the recorded mass spectra of RTOF with a set of 61 molecules, and their molecular fragments resulting from the ionisation. The major groups of chemical species are hydrocarbons, oxygenated hydrocarbons, nitrogen-bearing molecules, sulphur-bearing molecules, halogenated molecules and others (including water and CO2). About 70% of these grains are depleted in water compared to the comet coma, thus, can be considered as semi-volatile dust grains, and the other about 30% are water grains. The mineral phase of these grains, if there is any, cannot be investigated in these measurements. However, in an earlier investigation the bulk composition of mineral grains on the surface of the comet was inferred from solar wind sputtering of these grains (Wurz et al., 2015). H. Balsiger, K. Altwegg, P. Bochsler, P. Eberhardt, J. Fischer, S. Graf, A. Jäckel, E. Kopp, U. Langer, M. Mildner, J. Müller, T. Riesen, M. Rubin, S. Scherer, P. Wurz, S. Wüthrich, E. Arijs, S. Delanoye, J. De Keyser, E. Neefs, D. Nevejans, H. Rème, C. Aoustin, C. Mazelle, J.-L. Médale, J.A. Sauvaud, J.-J. Berthelier, J.-L. Ber-taux, L. Duvet, J.-M. Illiano, S.A. Fuselier, A.G. Ghielmetti, T. Magoncelli, E.G. Shelley, A. Korth, K. Heerlein, H. Lauche, S. Livi, A. Loose, U. Mall, B. Wilken, F. Gliem, B. Fiethe, T.I. Gombosi, B. Block, G.R. Carignan, L.A. Fisk, J.H. Waite, D.T. Young, and H. Wollnik, ROSINA - Rosetta Orbiter Spectrometer for Ion and Neutral Analysis, Space Science Review 128 (2007), 745-801. K.-H Glassmeier, H. Boehnhardt, D. Koschny, E. Kührt, and I. Richter, The Rosetta Mission: Flying To-wards the Origin of the Solar System, Space Science Reviews 128 (2007), 1-21. S. Scherer, K. Altwegg, H. Balsiger, J. Fischer, A. Jäckel, A. Korth, M. Mildner, D. Piazza, H. Rème, and P. Wurz, A novel principle for an ion mirror design in time-of-flight mass spectrometry, Int. Jou. Mass Spectr. 251 (2006) 73-81. P. Wurz, M. Rubin, K. Altwegg, H. Balsiger, S. Gasc, A. Galli, A. Jäckel, L. Le Roy, U. Calmonte, C. Tzou, U.A. Mall, B. Fiethe, J. De Keyser, J.J. Berthelier, H. Rème, A. Bieler, V. Tenishev, T.I. Gombosi, and S.A. Fuselier, Solar Wind Sputtering of Dust on the Surface of 67P/Churyumov-Gerasimenko, Astron. Astrophys. 583, A22 (2015) 1-9, DOI: 10.1051/0004-6361/201525980.

Survey for Ortho-to-Para Abundance Ratios (OPRs) of NH2 in Comets: Revisit to the Meaning of OPRs of Cometary Volatiles

NASA Astrophysics Data System (ADS)

Kawakita, Hideyo; Shinnaka, Yoshiharu; Jehin, Emmanuel; Decock, Alice; Hutsemekers, Damien; Manfroid, Jean

2016-10-01

Since molecules having identical protons can be classified into nuclear-spin isomers (e.g., ortho-H2O and para-H2O for water) and their inter-conversions by radiative and non-destructive collisional processes are believed to be very slow, the ortho-to-para abundance ratios (OPRs) of cometary volatiles such as H2O, NH3 and CH4 in coma have been considered as primordial characters of cometary molecules [1]. Those ratios are usually interpreted as nuclear-spin temperatures although the real meaning of OPRs is in strong debate. Recent progress in laboratory studies about nuclear-spin conversion in gas- and solid-phases [2,3] revealed short-time nuclear-spin conversions for water, and we have to reconsider the interpretation for observed OPRs of cometary volatiles. We have already performed the survey for OPRs of NH2 in more than 20 comets by large aperture telescopes with high-resolution spectrographs (UVES/VLT, HDS/Subaru, etc.) in the optical wavelength region [4]. The observed OPRs of ammonia estimated from OPRs of NH2, cluster around ~1.1 (cf. 1.0 as a high-temperature limit), indicative of ~30 K as nuclear-spin temperatures. We present our latest results for OPRs of cometary NH2 and discuss about the real meaning of OPRs of cometary ammonia, in relation to OPRs of water in cometary coma. Chemical processes in the inner coma may play an important role to achieve un-equilibrated OPRs of cometary volatiles in coma.This work was financially supported by MEXT Supported Program for the Strategic Research Foundation at Private Universities, 2014-2018 (No. S1411028) (HK) and by Graint-in-Aid for JSPS Fellows, 15J10864 (YS).References:[1] Mumma & Charnley, 2011, Annu. Rev. Astro. Astrophys. 49, 471.[2] Hama & Watanabe, 2013, Chem. Rev. 113, 8783.[3] Hama et al., 2008, Science 351, 6268.[4] Shinnaka et al., 2011, ApJ 729, 81.

Apparatus for sequentially transporting containers

NASA Technical Reports Server (NTRS)

Hudgins, J. L. (Inventor)

1982-01-01

Apparatus for transferring and manipulating a plurality of containers in a sequence is disclosed including a mechanical manipulator arm having a gripping device which automatically picks up a container at a fixed pickup position P and transfers it to a processing station. At a processing station X, the container is loaded with silicon wafers and thereafter returned by the arm to the fixed position P at the pickup and return station Y. A plurality of the containers may be processed in sequence from the fixed pickup position by providing a movable carriage upon which container pedestal platforms are supported, at least one of which is an elevator platform. The platforms include abutments for properly positioning the containers for accurate pickup by the manipulator arm.

Properties of planetward ion flows in Venus' magnetotail

NASA Astrophysics Data System (ADS)

Kollmann, P.; Brandt, P. C.; Collinson, G.; Rong, Z. J.; Futaana, Y.; Zhang, T. L.

2016-08-01

Venus is gradually losing some of its atmosphere in the form of ions through its induced magnetotail. Some of these ions have been reported previously to flow back to the planet. Proposed drivers are magnetic reconnection and deflection of pickup ions in the magnetic field. We analyze protons and oxygen ions with eV to keV energies acquired by the ASPERA-4/IMA instrument throughout the entire Venus Express mission. We find that venusward flowing ions are important in the sense that their density and deposition rate into the atmosphere is of the same order of magnitude as the density and escape rate of downtail flowing ions. Our analysis shows that during strong EUV irradiance, which occurs during solar maximum, the flux of venusward flowing protons is weaker and of oxygen ions is stronger than during weak irradiance. Since such a behavior was observed when tracing oxygen ions through a MHD model, the ultimate driver of the venusward flowing ions may simply be the magnetic field configuration around Venus. Although the pure downtail oxygen flux stays mostly unchanged for all observed EUV conditions, the increase in venusward oxygen flux for high irradiance results in a lower net atmospheric escape rate. Venusward bulk flows are mostly found in locations where the magnetic field is weak relative to the interplanetary conditions. Although a weak field is generally an indicator of proximity to the magnetotail current sheet, these flows do not cluster around current sheet crossings, as one may expect if they would be driven by magnetic reconnection.

Fabrication of Metallic Magnetic Calorimeter for Radionuclide Analysis

NASA Astrophysics Data System (ADS)

Yoon, W. S.; Kim, G. B.; Lee, H. J.; Lee, J. Y.; Lee, J. H.; Jang, Y. S.; Lee, S. J.; Lee, M. K.; Kim, Y. H.

2014-09-01

We present a detailed report on the fabrication process of a metallic magnetic calorimeter (MMC). The MMC is configured in a planar geometry with a meander-shaped pickup coil covered with a Au:Er temperature sensor layer. The meander coil is used to apply a magnetic field to magnetize the erbium ions and to measure the magnetization change of the spin system. The MMC is designed to have a large area (1 mm) and 3 m thickness Au:Er layer, which is suited for large metal absorbers with a few nJ/K heat capacity in radionuclide analysis applications. The completed devices are used in alpha and Q spectrometries.

Transport of Solar Wind Fluctuations: A Two-Component Model

NASA Technical Reports Server (NTRS)

Oughton, S.; Matthaeus, W. H.; Smith, C. W.; Breech, B.; Isenberg, P. A.

2011-01-01

We present a new model for the transport of solar wind fluctuations which treats them as two interacting incompressible components: quasi-two-dimensional turbulence and a wave-like piece. Quantities solved for include the energy, cross helicity, and characteristic transverse length scale of each component, plus the proton temperature. The development of the model is outlined and numerical solutions are compared with spacecraft observations. Compared to previous single-component models, this new model incorporates a more physically realistic treatment of fluctuations induced by pickup ions and yields improved agreement with observed values of the correlation length, while maintaining good observational accord with the energy, cross helicity, and temperature.

Wave excitation by nonlinear coupling among shear Alfvén waves in a mirror-confined plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ikezoe, R., E-mail: ikezoe@prc.tsukuba.ac.jp; Ichimura, M.; Okada, T.

2015-09-15

A shear Alfvén wave at slightly below the ion-cyclotron frequency overcomes the ion-cyclotron damping and grows because of the strong anisotropy of the ion temperature in the magnetic mirror configuration, and is called the Alfvén ion-cyclotron (AIC) wave. Density fluctuations caused by the AIC waves and the ion-cyclotron range of frequencies (ICRF) waves used for ion heating have been detected using a reflectometer in a wide radial region of the GAMMA 10 tandem mirror plasma. Various wave-wave couplings are clearly observed in the density fluctuations in the interior of the plasma, but these couplings are not so clear in themore » magnetic fluctuations at the plasma edge when measured using a pick-up coil. A radial dependence of the nonlinearity is found, particularly in waves with the difference frequencies of the AIC waves; bispectral analysis shows that such wave-wave coupling is significant near the core, but is not so evident at the periphery. In contrast, nonlinear coupling with the low-frequency background turbulence is quite distinct at the periphery. Nonlinear coupling associated with the AIC waves may play a significant role in the beta- and anisotropy-limits of a mirror-confined plasma through decay of the ICRF heating power and degradation of the plasma confinement by nonlinearly generated waves.« less

Evaluation of impression accuracy for a four-implant mandibular model--a digital approach.

PubMed

Stimmelmayr, Michael; Erdelt, Kurt; Güth, Jan-Frederik; Happe, Arndt; Beuer, Florian

2012-08-01

Implant-supported prosthodontics requires precise impressions to achieve a passive fit. Since the early 1990s, in vitro studies comparing different implant impression techniques were performed, capturing the data mostly mechanically. The purpose of this study was to evaluate the accuracy of three different impression techniques digitally. Dental implants were inserted bilaterally in ten polymer lower-arch models at the positions of the first molars and canines. From each original model, three different impressions (A, transfer; B, pick-up; and C, splinted pick-up) were taken. Scan-bodies were mounted on the implants of the polymer and on the lab analogues of the stone models and digitized. The scan-body in position 36 (FDI) of the digitized original and master casts were each superimposed, and the deviations of the remaining three scan-bodies were measured three-dimensionally. The systematic error of digitizing the models was 13 μm for the polymer and 5 μm for the stone model. The mean discrepancies of the original model to the stone casts were 124 μm (±34) μm for the transfer technique, 116 (±46) μm for the pick-up technique, and 80 (±25) μm for the splinted pick-up technique. There were statistically significant discrepancies between the evaluated impression techniques (p ≤ 0.025; ANOVA test). The splinted pick-up impression showed the least deviation between original and stone model; transfer and pick-up techniques showed similar results. For better accuracy of implant-supported prosthodontics, the splinted pick-up technique should be used for impressions of four implants evenly spread in edentulous jaws.

Interstellar Mapping and Acceleration Probe (IMAP)

NASA Astrophysics Data System (ADS)

Schwadron, Nathan

2016-04-01

Our piece of cosmic real-estate, the heliosphere, is the domain of all human existence - an astrophysical case-history of the successful evolution of life in a habitable system. By exploring our global heliosphere and its myriad interactions, we develop key physical knowledge of the interstellar interactions that influence exoplanetary habitability as well as the distant history and destiny of our solar system and world. IBEX was the first mission to explore the global heliosphere and in concert with Voyager 1 and Voyager 2 is discovering a fundamentally new and uncharted physical domain of the outer heliosphere. In parallel, Cassini/INCA maps the global heliosphere at energies (~5-55 KeV) above those measured by IBEX. The enigmatic IBEX ribbon and the INCA belt were unanticipated discoveries demonstrating that much of what we know or think we understand about the outer heliosphere needs to be revised. The next quantum leap enabled by IMAP will open new windows on the frontier of Heliophysics at a time when the space environment is rapidly evolving. IMAP with 100 times the combined resolution and sensitivity of IBEX and INCA will discover the substructure of the IBEX ribbon and will reveal in unprecedented resolution global maps of our heliosphere. The remarkable synergy between IMAP, Voyager 1 and Voyager 2 will remain for at least the next decade as Voyager 1 pushes further into the interstellar domain and Voyager 2 moves through the heliosheath. The "A" in IMAP refers to acceleration of energetic particles. With its combination of highly sensitive pickup and suprathermal ion sensors, IMAP will provide the species and spectral coverage as well as unprecedented temporal resolution to associate emerging suprathermal tails with interplanetary structures and discover underlying physical acceleration processes. These key measurements will provide what has been a critical missing piece of suprathermal seed particles in our understanding of particle acceleration to high energies in the solar-heliospheric system and by extension to other planetary and astrophysical paradigms. IMAP, like ACE before it, will be a keystone of the Heliophysics System Observatory by providing comprehensive cosmic ray, energetic particle, pickup ion, suprathermal ion, neutral atom, solar wind, solar wind heavy ion, and magnetic field observations to diagnose the changing space environment and understand the fundamental origins of particle acceleration.

Electronically transmitted prescriptions not picked up at pharmacies in Sweden.

PubMed

Ax, Fredrik; Ekedahl, Anders

2010-03-01

Electronically transmitted prescriptions (ETPs) became common after 1995 in Sweden; however, it is accompanied by a substantial increase in the number of prescriptions not picked up at pharmacies. To investigate the "no pick-up" rates of ETPs at pharmacies across type of drug and patient age and gender and the reasons patients' report for no pick-up. A cross-sectional study examining no pick-up of ETPs transmitted during 3 months in 2002, and a mail survey of patients to determine the reasons for failure to pick-up in the county of Sörmland, Sweden, with a population of 261,000, and 21 pharmacies. Chi-square tests were used for calculations of frequency differences among groups. The overall no pick-up rate of ETPs was 2.5%; men had consistently higher rates than women. The highest rates were seen for adolescents and young adults. Rates were higher than average for antibiotics. About 60% of the answers indicated that prescriptions not picked up were duplicate prescriptions or not needed. "Unintentional nonadherence" was reported by one-fifth of patients. No pick-up rate in general was low (2.5%), but there were differences across patient age and gender, the rates being higher among adolescents and young adults. Duplicate prescriptions may explain a significant share of the abandoned prescriptions. Copyright 2010 Elsevier Inc. All rights reserved.

Titan Ice and Dust Experiment (TIDE): Detection and Analysis of Compounds of Interest to Astrobiology in the Lower Atmosphere and Surface of Titan

NASA Technical Reports Server (NTRS)

Kojiro, Daniel R.; Holland Paul M.; Stimac, Robert M.; Kaye, William J.; Takeruchi, Noreshige

2004-01-01

The Titan Orbiter Aerorover Mission (TOAM) is a proposed concept for the Solar System Exploration Visions Mission, Titan Explorer, a follow-on to the Cassini-Huygens mission. TOAM would use a Titan polar orbiter and a lighter-than-air aerorover to investigate the surface and atmosphere of Titan. Astrobiology issues will be addressed though TOAM investigations including, for example: Distribution and composition of organics (atmospheric, aerosol, surface); Organic chemical processes, their chemical context and energy sources; and Seasonal variations and interactions of the atmosphere and surface. The TIDE instrument will perform in-situ analyses to obtain comprehensive and sensitive molecular and elemental assays of volatile organics in the atmosphere, oceans and surface. TIDE chemical analyses are conducted by a Gas Chromatograph-Ion Mobility Spectrometer (GC-IMS). This TIDE GC-IMS was a component of the mini-Cometary Ice and Dust Experiment (mini-CIDEX) developed for the chemical analysis of a cometary environment. Both the GC and helium IMS of mini-CIDEX have been further developed to better meet the analytical and operational requirements of the TOAM. application. A Micro-ElectroMechanical System (MEMS) GC and Mini-Cell helium IMS are under development to replace their respective mini-CIDEX components, providing similar or advanced analytical capabilities.

Development of a planar-type high sensitivity metallic contaminant detector

NASA Astrophysics Data System (ADS)

Okabe, Shunsuke; Sasada, Ichiro

2017-05-01

Metallic contaminant detectors based on the balanced coil system are widely used in the food industry. In the balanced coil system, an excitation coil and two identical pickup coils are used in a way that the magnetic coupling of pickup coils to the excitation coil is cancelled with each other when no metallic contaminants present. In a conventional system, the excitation coil and the pickup coil are planar and are parallel, therefore the magnetic coupling is strong even if there is no metallic contaminant. Such strong magnetic coupling makes balancing procedure tedious. In this paper, we introduce a new coil system in which pickup coils are set orthogonal to the excitation coil, making the magnetic coupling much small compared to conventional counterpart. Pickup coils are equipped with thin magnetic cores and placed inside the excitation coil being parallel to the excitation coil plane. The balancing method consists of two steps; the one is geometrical and the other is digital processing including down conversion. Experiments are carried out to show the detection capability of ferromagnetic contaminants and non-magnetic contaminants.

Precise measurement of a magnetic field generated by the electromagnetic flux compression technique.

PubMed

Nakamura, D; Sawabe, H; Matsuda, Y H; Takeyama, S

2013-04-01

The precision of the values of a magnetic field generated by electromagnetic flux compression was investigated in ultra-high magnetic fields of up to 700 T. In an attempt to calibrate the magnetic field measured by pickup coils, precise Faraday rotation (FR) measurements were conducted on optical (quartz and crown) glasses. A discernible "turn-around" phenomenon was observed in the FR signal as well as the pickup coils before the end of a liner implosion. We found that the magnetic field measured by pickup coils should be corrected by taking into account the high-frequency response of the signal transmission line. Near the peak magnetic field, however, the pickup coils failed to provide reliable values, leaving the FR measurement as the only method to precisely measure extremely high magnetic fields.

Exact solutions for the collaborative pickup and delivery problem.

PubMed

Gansterer, Margaretha; Hartl, Richard F; Salzmann, Philipp E H

2018-01-01

In this study we investigate the decision problem of a central authority in pickup and delivery carrier collaborations. Customer requests are to be redistributed among participants, such that the total cost is minimized. We formulate the problem as multi-depot traveling salesman problem with pickups and deliveries. We apply three well-established exact solution approaches and compare their performance in terms of computational time. To avoid unrealistic solutions with unevenly distributed workload, we extend the problem by introducing minimum workload constraints. Our computational results show that, while for the original problem Benders decomposition is the method of choice, for the newly formulated problem this method is clearly dominated by the proposed column generation approach. The obtained results can be used as benchmarks for decentralized mechanisms in collaborative pickup and delivery problems.

Accurate simulations of helium pick-up experiments using a rejection-free Monte Carlo method

NASA Astrophysics Data System (ADS)

Dutra, Matthew; Hinde, Robert

2018-04-01

In this paper, we present Monte Carlo simulations of helium droplet pick-up experiments with the intention of developing a robust and accurate theoretical approach for interpreting experimental helium droplet calorimetry data. Our approach is capable of capturing the evaporative behavior of helium droplets following dopant acquisition, allowing for a more realistic description of the pick-up process. Furthermore, we circumvent the traditional assumption of bulk helium behavior by utilizing density functional calculations of the size-dependent helium droplet chemical potential. The results of this new Monte Carlo technique are compared to commonly used Poisson pick-up statistics for simulations that reflect a broad range of experimental parameters. We conclude by offering an assessment of both of these theoretical approaches in the context of our observed results.

Carbonaceous Components in the Comet Halley Dust

NASA Technical Reports Server (NTRS)

Fomenkova, M. N.; Chang, S.; Mukhin, L. M.

1994-01-01

Cometary grains containing large amounts of carbon and/or organic matter (CHON) were discovered by in situ measurements of comet Halley dust composition during VEGA and GIOTTO flyby missions. In this paper, we report the classification of these cometary, grains by means of cluster analysis, discuss the resulting compositional groups, and compare them with substances observed or hypothesized in meteorites, interplanetary dust particles, and the interstellar medium. Grains dominated by carbon and/or organic matter (CHON grains) represent approx. 22% of the total population of measured cometary dust particles. They, usually contain a minor abundance of rock-forming elements as well. Grains having organic material are relatively more abundant in the vicinity of the nucleus than in the outer regions of the coma, which suggests decomposition of the organics in the coma environment. The majority of comet Halley organic particles are multicomponent mixtures of carbon phases and organic compounds. Possibly, the cometary CHON grains may be related to kerogen material of an interstellar origin in carbonaceous meteorites. Pure carbon grains, hydrocarbons and polymers of cyanopolyynes, and multi-carbon monoxides are present in cometary dust as compositionally simple and distinctive components among a variety of others. There is no clear evidence of significant presence of pure formaldehyde or HCN polymers in Halley dust particles. The diversity of types of cometary organic compounds is consistent with the inter-stellar dust model of comets and probably reflects differences in composition of precursor dust. Preservation of this heterogeneity among submicron particles suggest the gentle formation of cometary, nucleus by aggregation of interstellar dust in the protosolar nebula without complete mixing or chemical homogenization at the submicron level.

Ground truth of (sub-)micrometre cometary dust - Results of MIDAS onboard Rosetta

NASA Astrophysics Data System (ADS)

Mannel, Thurid; Bentley, Mark; Schmied, Roland; Torkar, Klaus; Jeszenszky, Harald; Romsted, Jens; Levasseur-Regourd, A.; Weber, Iris; Jessberger, Elmar K.; Ehrenfreund, Pascale; Köberl, Christian; Havnes, Ove

2016-10-01

The investigation of comet 67P by Rosetta has allowed the comprehensive characterisation of pristine cometary dust particles ejected from the nucleus. Flying alongside the comet at distances as small as a few kilometres, and with a relative velocity of only centimetres per second, the Rosetta payload sampled almost unaltered dust. A key instrument to study this dust was MIDAS (the Micro-Imaging Dust Analysis System), a dedicated atomic force microscope that scanned the surfaces of hundreds of (sub-)micrometre sized particles in 3D with resolutions down to nanometres. This offers the unique opportunity to explore the morphology of smallest cometary dust and expand our current knowledge about cometary material.Here we give an overview of dust collected and analysed by MIDAS and highlight its most important features. These include the ubiquitous agglomerate nature of the dust, which is found at all size scales from the largest (>10 µm) through to the smallest (<1 µm) dust particles. The sub-units show characteristic sizes and shapes that are compared with model predictions for interstellar dust.Our findings constrain key parameters of the evolution of the early Solar System. We will discuss which dust growth model is favoured by the observed morphology and how the results restrict cometary formation. Finally, dust particles detected by MIDAS resemble primitive interplanetary dust which is a strong argument for a common cometary origin.

Wave-Particle Interactions and Particle Acceleration in Turbulent Plasmas: Hybrid Simulations

NASA Astrophysics Data System (ADS)

Kucharek, Harald; Pogorelov, Nikolai; Mueller, Hans; Gamayunov, Konstantin; Farrugia, Charles

2015-04-01

Wave-particle interactions and acceleration processes are present in all key regions inside and outside of the heliosphere. Spacecraft observations measure ion distributions and accelerated ion populations, which are the result of one or several processes. For instance STEREO measures energetic particles associated with interplanetary discontinuities and in the solar wind. Voyager and IBEX provide unique data of energetic particles from the termination shock and the inner and outer heliopause. The range of plasma conditions covered by observations is enormous. However, the physical processes causing particle acceleration and wave-particle interaction and determining the particle distributions are still unknown. Currently two mechanisms, the so-called pumping mechanism (Fisk and Gloeckler, 2010) and merging/contracting island (Fermo, Drake & Swisdak, 2010) are discussed as promising models. In order to determine these individual processes, numerical models or theoretical considerations are needed. Hybrid simulations, which include all kinetic processes self-consistently on the ion level, are a very proven, powerful tool to investigate wave-particle interaction, turbulence, and phase-space evolution of pickup and solar wind ions. In the framework of this study we performed 3D multi-species hybrid simulations for an ion/ion beam instability to study the temporal evolution of ion distributions, their stability, and the influence of self-generated waves. We investigated the energization of ions downstream of interplanetary discontinuities and shocks and downstream of the termination shock, the turbulence, and growth rate of instabilities and compared the results with theoretical predictions. The simulations show that ions can be accelerated downstream of collisionless shocks by trapping of charged particles in coherent wave fronts.

47 CFR 74.12 - Notification of filing of applications.

Code of Federal Regulations, 2010 CFR

2010-10-01

....1030 “Notification concerning interference to Radio Astronomy, Research, and Receiving Installations... remote pickup stations (subpart D). (b) TV pickup stations (subpart F). (c) Low power auxiliary stations...

Formation environment of cometary nuclei in the primordial solar nebula

NASA Astrophysics Data System (ADS)

Yamamoto, T.

1985-01-01

The formation environment of comets in the primordial solar nebula is investigated from the point of view of the chemical composition of the ices of cometary nuclei. A sublimation sequence for various species of possible constituents of the nuclear ice, which would have condensed on the grain surface in the parent interstellar cloud was obtained by calculating the temperature of grains in the solar nebula. On this basis, an allowed range of the nebular temperature in the formation region of cometary nuclei is obtained from a condition for retention of the ices of the nuclear composition. Combining this result with models of the solar nebula, the region for the formation of cometary nuclei in the solar nebula is discussed. It is shown that cometary nuclei formed at least beyond the region between the formation regions of Saturn and Uranus. Finally, an upper limit is estimated for the grain temperature in the region of comet formation at an earlier stage of the solar nebula. The grain temperature is shown to be less than 60 K at this stage.

Dust in Cometary Comae: Present Understanding of the Structure and Composition of Dust Particles

NASA Technical Reports Server (NTRS)

Levasseur-Regourd, A. C.; Zolensky, M.; Lasue, J.

2007-01-01

In situ probing of a very few cometary comae has shown that dust particles present a low albedo and a low density, and that they consist of both rocky material and refractory organics. Remote observations of solar light scattered by cometary dust provide information on the properties of dust particles in the coma of a larger set of comets. The observations of the linear polarization in the coma indicate that the dust particles are irregular, with a size greater (on the average) than about one micron. Besides, they suggest, through numerical and experimental simulations, that both compact grains and fluffy aggregates (with a power law of the size distribution in the -2.6 to -3 range), and both rather transparent silicates and absorbing organics are present in the coma. Recent analysis of the cometary dust samples collected by the Stardust mission provide a unique ground truth and confirm, for comet 81P/Wild 2, the results from remote sensing observations. Future space missions to comets should, in the next decade, lead to a more precise characterization of the structure and composition of cometary dust particles.

VizieR Online Data Catalog: 18-cm OH lines in comets (Crovisier+, 2002)

NASA Astrophysics Data System (ADS)

Crovisier, J.; Colom, P.; Gerard, E.; Bockelee-Morvan, D.; Bourgois, G.

2002-10-01

Since the apparition of comet Kohoutek 1973 XII, the 18-cm lines of the OH radical have been systematically observed in a number of comets with the Nancay radio telescope. Between 1973 and 1999, 52 comets have been successfully detected. This allowed an evaluation of the cometary water production rates and their evolution with time, as well as a study of several physical processes such as the excitation mechanisms of the OH radio lines, the expansion of cometary atmospheres, their anisotropy in relation to non-gravitational forces, and the Zeeman effect in relation to the cometary magnetic field. Part of these observations and their analysis have already been published. The bulk of the results are now organized in a data base. The present paper is a general presentation of the Nancay cometary data base and a more specific description of the observations of 53 cometary apparitions between 1982 and 1999. Comets observed before 1982 are only partly incorporated in the data base. Observations of comets since 2000 have benefited from a major upgrade of the telescope; they will be presented in forthcoming publications. (5 data files).

Collaborative Research: A Model of Partially Ionized Plasma Flows with Kinetic Treatment of Neutral Atoms and Nonthermal Ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pogorelov, Nikolai; Zhang, Ming; Borovikov, Sergey

Interactions of flows of partially ionized, magnetized plasma are frequently accompanied by the presence of both thermal and non-thermal (pickup) ion components. Such interactions cannot be modeled using traditional MHD equations and require more advanced approaches to treat them. If a nonthermal component of ions is formed due to charge exchange and collisions between the thermal (core) ions and neutrals, it experiences the action of magnetic field, its distribution function is isotropized, and it soon acquires the velocity of the ambient plasma without being thermodynamically equilibrated. This situation, e. g., takes place in the outer heliosphere - the part ofmore » interstellar space beyond the solar system whose properties are determined by the solar wind interaction with the local interstellar medium. This is also possible in laboratory, at million degrees and above, when plasma is conducting electricity far too well, which makes Ohmic heating ineffective. To attain the target temperatures one needs additional heating eventually playing a dominant role. Among such sources is a so-called neutral particle beam heating. This is a wide-spread technique (Joint European Torus and International Thermonuclear Experimental Reactor experiments) based on the injection of powerful beams of neutral atoms into ohmically preheated plasma. In this project we have investigated the energy and density separation between the thermal and nonthermal components in the solar wind and interstellar plasmas. A new model has been developed in which we solve the ideal MHD equations for mixture of all ions and the kinetic Boltzmann equation to describe the transport of neutral atoms. As a separate capability, we can treat the flow of neutral atoms in a multi-component fashion, where neutral atoms born in each thermodynamically distinct regions are governed by the Euler gas dynamic equations. We also describe the behavior of pickup ions either kinetically, using the Fokker–Planck equation, or as a separate fluid. Our numerical simulations have demonstrated that pickup ions play a major role in the interaction of the solar wind and (partially ionized) interstellar medium plasmas. Our teams have investigated the stability of the surface (the heliopause) that separates the solar wind from the local interstellar medium, the transport of galactic cosmic rays, the properties of the heliotail flow, and modifications to the bow wave in front of the heliopause due to charge exchange between the neutral H atoms born in the solar wind and interstellar ions. Modeling results have been validated against observational data, such as obtained by the Interstellar Boundary Explorer (IBEX), and made it possible to shed light on the structure of energetic neutral atom maps created by this spacecraft.. We have also demonstrated that charge-exchange modulated heliosphere is a source of anisotropy of the multi-TeV cosmic ray flux observed in a number of Earth-bound air shower experiments. Newly developed codes are implemented within a Multi-Scale Fluid-Kinetic Simulation Suite (MS-FLUKSS), a publicly available code being developed by our team for over 12 years. MS-FLUKSS scales well up to 160,000 computing cores and has been ported on major supercomputers in the country. Efficient parallelization and data choreography in the continuum simulation modules are provided by Chombo, an adaptive mesh refinement framework managed by Phillip Colella’s team at LBNL. We have implemented in-house, hybrid (MPI+OpenMP) parallelization of the kinetic modules that solve the Boltzmann equation with a Monte Carlo method. Currently, the kinetic modules are being rewritten to take advantage of the modern CPU-GPU supercomputer architecture. The scope of the project allowed us to enhance plasma research and education in such broad, multidis- ciplinary field as physics of partially ionized plasma and its application to space physics and fusion science. Besides the impact on the modeling of complex physical systems, our approach to computational resource management for complex codes utilizing multiple algorithm technologies appears to be a major advance on current approaches. The development of sophisticated resource management will be essential for all future modeling efforts that incorporate a diversity of scales and physical processes. Our effort provided leadership in promoting computational science and plasma physics within the UAH and FIT campuses and, through the training of a broad spectrum of scientists and engineers, foster new technologies across the country.« less

Collaborative Research: A Model of Partially Ionized Plasma Flows with Kinetic Treatment of Neutral Atoms and Nonthermal Ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pogorelov, Nikolai; Zhang, Ming

Interactions of flows of partially ionized, magnetized plasma are frequently accompanied by the presence of both thermal and non-thermal (pickup) ion components. Such interactions cannot be modeled using traditional MHD equations and require more advanced approaches to treat them. If a nonthermal component of ions is formed due to charge exchange and collisions between the thermal (core) ions and neutrals, it experiences the action of magnetic field, its distribution function is isotropized, and it soon acquires the velocity of the ambient plasma without being thermodynamically equilibrated. This situation, e. g., takes place in the outer heliosphere –- the part ofmore » interstellar space beyond the solar system whose properties are determined by the solar wind interaction with the local interstellar medium. This is also possible in laboratory, at million degrees and above, when plasma is conducting electricity far too well, which makes Ohmic heating ineffective. To attain the target temperatures one needs additional heating eventually playing a dominant role. Among such sources is a so-called neutral particle beam heating. This is a wide-spread technique (Joint European Torus and International Thermonuclear Experimental Reactor experiments) based on the injection of powerful beams of neutral atoms into ohmically preheated plasma. In this project we have investigated the energy and density separation between the thermal and nonthermal components in the solar wind and interstellar plasmas. A new model has been developed in which we solve the ideal MHD equations for mixture of all ions and the kinetic Boltzmann equation to describe the transport of neutral atoms. As a separate capability, we can treat the flow of neutral atoms in a multi-component fashion, where neutral atoms born in each thermodynamically distinct region are governed by the Euler gas dynamic equations. We also describe the behavior of pickup ions either kinetically, using the Fokker--Planck equation, or as a separate fluid. Our numerical simulations have demonstrated that pickup ions play a major role in the interaction of the solar wind and (partially ionized) interstellar medium plasmas. Our teams have investigated the stability of the surface (the heliopause) that separates the solar wind from the local interstellar medium, the transport of galactic cosmic rays, the properties of the heliotail flow, and modifications to the bow wave in front of the heliopause due to charge exchange between the neutral H atoms born in the solar wind and interstellar ions. Modeling results have been validated against observational data, such as obtained by the Interstellar Boundary Explorer (IBEX), and made it possible to shed light on the structure of energetic neutral atom maps created by this spacecraft.. We have also demonstrated that charge-exchange modulated heliosphere is a source of anisotropy of the multi-TeV cosmic ray flux observed in a number of Earth-bound air shower experiments. Newly developed codes are implemented within a Multi-Scale Fluid-Kinetic Simulation Suite (MS-FLUKSS), a publicly available code being developed by our team for over 12 years. MS-FLUKSS scales well up to 160,000 computing cores and has been ported on major supercomputers in the country. Efficient parallelization and data choreography in the continuum simulation modules are provided by Chombo, an adaptive mesh refinement framework managed by Phillip Colella's team at LBNL. We have implemented in-house, hybrid (MPI+OpenMP) parallelization of the kinetic modules that solve the Boltzmann equation with a Monte Carlo method. Currently, the kinetic modules are being rewritten to take advantage of the modern CPU-GPU supercomputer architecture. The scope of the project allowed us to enhance plasma research and education in such broad, multidisciplinary field as physics of partially ionized plasma and its application to space physics and fusion science. Besides the impact on the modeling of complex physical systems, our approach to computational resource management for complex codes utilizing multiple algorithm technologies appears to be a major advance on current approaches. The development of sophisticated resource management will be essential for all future modeling efforts that incorporate a diversity of scales and physical processes. Our effort provided leadership in promoting computational science and plasma physics within the UAH and FIT campuses and, through the training of a broad spectrum of scientists and engineers, fostering new technologies across the country.« less

Distribution of water-group ion cyclotron waves in Saturn's magnetosphere

NASA Astrophysics Data System (ADS)

Chou, Marty; Cheng, Chio Zong

2017-09-01

The water-group ion cyclotron waves (ICWs) in Saturn's magnetosphere were studied using the magnetic field data provided by the MAG magnetometer on board the Cassini satellite. The period from January 2005 to December 2009, when the Cassini radial distance is smaller than 8 R S , was used. ICWs were identified by their left-hand circularly polarized magnetic perturbations and wave frequencies near the water-group ion gyrofrequencies. We obtained the spatial distribution of ICW amplitude and found that the source region of ICWs is mostly located in the low-latitude region, near the equator and inside the 6 R S radial distance. However, it can extend beyond 7 R S in the midnight region. In general, the wave amplitude is peaked slightly away from the equator, for all local time sectors in both the Northern and Southern Hemispheres. By assuming that the water-group ions are composed of pickup ions and background thermal ions, we obtained the local instability condition of the ICWs and estimated their growth rate along the field lines. If the wave amplitude is correlated with the growth rate, the observed latitudinal dependence of the wave amplitude can be well explained by the local stability analysis. Also, latitudinal location of the peak amplitude is found to depend on the local time. This implies a local time dependence for the water-group ion parallel temperature T|, as determined from the theoretical calculations. [Figure not available: see fulltext.

Cometary Astrometry

NASA Technical Reports Server (NTRS)

Yeomans, D. K. (Editor); West, R. M. (Editor); Harrington, R. S. (Editor); Marsden, B. G. (Editor)

1984-01-01

Modern techniques for making cometary astrometric observations, reducing these observations, using accurate reference star catalogs, and computing precise orbits and ephemerides are discussed in detail and recommendations and suggestions are given in each area.

Collecting cometary soil samples? Development of the ROSETTA sample acquisition system

NASA Technical Reports Server (NTRS)

Coste, P. A.; Fenzi, M.; Eiden, Michael

1993-01-01

In the reference scenario of the ROSETTA CNRS mission, the Sample Acquisition System is mounted on the Comet Lander. Its tasks are to acquire three kinds of cometary samples and to transfer them to the Earth Return Capsule. Operations are to be performed in vacuum and microgravity, on a probably rough and dusty surface, in a largely unknown material, at temperatures in the order of 100 K. The concept and operation of the Sample Acquisition System are presented. The design of the prototype corer and surface sampling tool, and of the equipment for testing them at cryogenic temperatures in ambient conditions and in vacuum in various materials representing cometary soil, are described. Results of recent preliminary tests performed in low temperature thermal vacuum in a cometary analog ice-dust mixture are provided.

Electron impact ionization in the vicinity of comets

NASA Astrophysics Data System (ADS)

Cravens, T. E.; Kozyra, J. U.; Nagy, A. F.; Gombosi, T. I.; Kurtz, M.

1987-07-01

The solar wind interacts very strongly with the extensive cometary coma, and the various interaction processes are initiated by the ionization of cometary neutrals. The main ionization mechanism far outside the cometary bow shock is photoionization by solar extreme ultraviolet radiation.Electron distributions measured in the vicinity of comets Halley and Giacobini-Zinner by instruments on the VEGA and ICE spacecraft, respectively, are used to calculate electron impact ionization frequencies. Ionization by electrons is of comparable importance to photoionization in the magnetosheaths of Comets Halley and Giacobini-Zinner. The ionization frequency in the inner part of the cometary plasma region of comet Halley is several times greater than the photoionization value. Tables of ionization frequencies as functions of electron temperature are presented for H2O, CO2, CO, O, N2, and H.

Thermal Ion Transport on the Moon and the Formation of the Lunar Swirls

NASA Technical Reports Server (NTRS)

Keller, John W.; Killen, R. M.; Stubbs, T. J.; Farrell, W. M.; Halekas, J. S.

2011-01-01

The bright "swirl" features observed on the lunar surface are generally associated with crustal magnetic anomalies. Prominent explanations that invoke these fields include: magnetic shielding in the form of a mini-magnetosphere, which impedes space weathering by the solar wind; magnetically controlled dust transport; and cometary or asteroidal impacts, that could result in shock magnetization with concomitant formation of the swirls. Here we consider another possibility in which the ambient magnetic and electric fields can transport and channel secondary ions produced by micrometeorite or solar wind ion impacts. We use a simplified model of the fields, which incorporates a two-dipole magnetic field model for Reiner Gamma, and typical solar wind conditions. We will present preliminarily results suggesting that ions created over significant regions of the lunar surface can be transported under the influence of local and interplanetary electromagnetic fields to narrow areas ncar arcas of high crustal magnetic field strength. The flux of these focused ions may be of sufficient intensity to chemically process (or otherwise bleach) the surface leading to the formation of the high albedo component of the lunar swirls. The theory is appealing since through a lensing effect, it is possible that this flux is sufficient to overcome other space weathering processes which would otherwise tend to erase the features. Also, with relatively low energy ions, and consistent with the observed focusing, the ion gyro radii in the local magnetic fields is small enough to resolve the swirls.

Cometary Evolution: Clues on Physical Properties from Chondritic Interplanetary Dust Particles

NASA Technical Reports Server (NTRS)

Rietmeijer, Frans J. M.; Mackinnon, Ian D. R.

1989-01-01

The degree of diversity or similarity detected in comets depends primarily on the lifetimes of the individual cometary nuclei at the time of analysis. It is inherent in our understanding of cometary orbital dynamics and the seminal model of comet origins by Oort that cometary evolution is the natural order of events in our Solar System. Thus, predictions of cometary behaviour in terms of bulk physical, mineralogical or chemical parameters should contain an appreciation of temporal variation(s). Previously, Rietmeijer and Mackinnon developed mineralogical bases for the chemical evolution of cometary nuclei primarily with regard to the predominantly silicate fraction of comet nuclei. We suggested that alteration of solids in cometary nuclei should be expected and that indications of likely reactants and products can be derived from judicious comparison with terrestrial diagenetic environments which include hydrocryogenic and low-temperature aqueous alterations. In a further development of this concept, Rietmeijer provides indirect evidence for the formation of sulfides and oxides in comet nuclei. Furthermore, Rietmeijer noted that timescales for hydrocryogenic and low-temperature reactions involving liquid water are probably adequate for relatively mature comets, e.g. P/comet Halley. In this paper, we will address the evolution of comet nuclei physical parameters such as solid particle grain size, porosity and density. In natural environments, chemical evolution (e.g. mineral reactions) is often accompanied by changes in physical properties. These concurrent changes are well-documented in the terrestrial geological literature, especially in studies of sediment diagenesis and we suggest that similar basic principles apply within the upper few meters of active comet nuclei. The database for prediction of comet nuclei physical parameters is, in principle, the same as used for the proposition of chemical evolution. We use detailed mineralogical studies of chondritic interplanetary dust particles (IDPS) as a guide to the likely constitution of mature comets traversing the inner Solar System. While there is, as yet, no direct proof that a specific sub-group or type of chondritic IDP is derived from a specific comet, it is clear that these particles are extraterrestrial in origin and that a certain portion of the interplanetary flux received by the Earth is cometary in origin. Two chondritic porous (CP) MPs, sample numbers W7010A2 and W7029Cl, from the Johnson Space Center Cosmic Dust Collection have been selected for this study of putative cometary physical parameters. This particular type of particle is considered a likely candidate for a cometary origin on the basis of mineralogy, bulk composition and morphology. While many IDPs have been subjected to intensive study over the past decade, we can develop a physical parameter model on only these two CP IDPs because few others have been studied in sufficient detail.

Cometary Evolution: Clues on Physical Properties from Chondritic Interplanetary Dust Particles

NASA Technical Reports Server (NTRS)

Reitmeijer, Frans J. M.; Mackinnon, Ian D. R.

1997-01-01

The degree of diversity or similarity detected in comets depends primarily on the lifetimes of the individual cometary nuclei at the time of analysis. It is inherent in our understanding of cometary orbital dynamics and the seminal model of comet origins that cometary evolution is the natural order of events in our Solar System. Thus, predictions of cometary behaviour in terms of bulk physical, mineralogical or chemical parameters should contain an appreciation of temporal variation(s). Previously, Rietmeijer and Mackinnon [1987] developed mineralogical bases for the chemical evolution of cometary nuclei primarily with regard to the predominantly silicate fraction of comet nuclei. We suggested that alteration of solids in cometary nuclei should be expected and that indications of likely reactants and products can be derived from judicious comparison with terrestrial diagenetic environments which include hydrocryogenic and low-temperature aqueous alterations. In a further development of this concept, Rietmeijer [1988] provides indirect evidence for the formation of sulfides and oxides in comet nuclei. Furthermore, Rietmeijer [1988] noted that timescales for hydrocryogenic and low-temperature reactions involving liquid water are probably adequate for relatively mature comets, e.g. P/comet Halley. In this paper, we will address the evolution of comet nuclei physical parameters such as solid particle grain size, porosity and density. In natural environments, chemical evolution (e.g. mineral reactions) is often accompanied by changes in physical properties. These concurrent changes are well-documented in the terrestrial geological literature, especially in studies of sediment diagenesis and we suggest that similar basic principles apply within the upper few meters of active comet nuclei. The database for prediction of comet nuclei physical parameters is, in principle, the same as used for the proposition of chemical evolution. We use detailed mineralogical studies of chondritic interplanetary dust particles (IDPS) as a guide to the likely constitution of mature comets traversing the inner Solar System. While there is, as yet, no direct proof that a specific sub-group or type of chondritic IDP is derived from a specific comet, it is clear that these particles are extraterrestrial in origin and that a certain portion of the interplanetary flux received by the Earth is cometary in origin. Two chondritic porous (CP) IDPS, sample numbers W701OA2 and W7029CI, from the Johnson Space Center Cosmic Dust Collection have been selected for this study of putative cometary physical parameters. This particular type of particle is considered a likely candidate for a cometary origin on the basis of mineralogy, bulk composition and morphology. While many IDPs have been subjected to intensive study over the past decade, we can develop a physical parameter model on only these two CP IDPs because few others have been studied in sufficient detail.

Chemical Composition of the Semi-Volatile Grains of Comet 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Wurz, P.; Altwegg, K.; Balsiger, H. R.; Berthelier, J. J.; De Keyser, J.; Fiethe, B.; Fuselier, S. A.; Gasc, S.; Gombosi, T. I.; Korth, A.; Mall, U.; Reme, H.; Rubin, M.; Tzou, C. Y.

2017-12-01

Rosetta was in orbit of comet 67P/Churyumov-Gerasimenko from August 2014 to September 2016. On board is the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) experiment that has been continuously collecting data on the chemical composition and activity of the coma from 3.5 AU to pericentre at 1.24 AU and out again to 3.5 AU. ROSINA consists of two mass spectrometers, the Double Focusing Mass Spectrometer (DFMS) and the Reflectron-type Time-Of-Flight (RTOF), as well as the COmet Pressure Sensor (COPS). ROSINA recorded the neutral gas and thermal plasma in the comet's coma. The two mass spectrometers have high dynamic ranges and complement each other with high mass resolution, and high time resolution and large mass range. COPS measures total gas densities, bulk velocities, and gas temperatures. Occasionally, a dust grain of cometary origin enters the ion source of a ROSINA instrument where the volatile part evaporates since these ion sources are hot. The release of volatiles from cometary dust grains was observed with all three ROSINA instruments on several occasions. Because the volatile content of such a dust grain is completely evaporated after a few seconds, the RTOF instrument is best suited for the investigation of its chemical composition since complete mass spectra are recorded during this time. During the mission 9 dust grains were observed with RTOF during the October 2014 to July 2016 time period. It is estimated that these grains contain about 10-15 g of volatiles. The mass spectra were interpreted with a set of 75 molecules, with the major groups of chemical species being hydrocarbons, oxygenated hydrocarbons, nitrogen-bearing molecules, sulphur-bearing molecules, halogenated molecules and others. About 70% of these grains are depleted in water compared to the comet coma, thus, can be considered as semi-volatile dust grains, and the other about 30% are water grains. The chemical composition varies considerably from grain to grain, indicating large chemical heterogeneity at these scales. In contrast, the elemental abundances vary much less.

Monitoring transients in low inductance circuits

DOEpatents

Guilford, Richard P.; Rosborough, John R.

1987-01-01

A pair of flat cable transmission lines are monitored for transient current spikes by using a probe connected to a current transformer by a pickup loop and monitoring the output of the current transformer. The approach utilizes a U-shaped pickup probe wherein the pair of flat cable transmission lines are received between the legs of the U-shaped probe. The U-shaped probe is preferably formed of a flat coil conductor adhered to one side of a flexible substrate. On the other side of the flexible substrate there is a copper foil shield. The copper foil shield is connected to one end of the flat conductor coil and connected to one leg of the pickup loop which passes through the current transformer. The other end of the flat conductor coil is connected to the other leg of the pickup loop.

Study of optical design of Blu-ray pickup head system with a liquid crystal element.

PubMed

Fang, Yi-Chin; Yen, Chih-Ta; Hsu, Jui-Hsin

2014-10-10

This paper proposes a newly developed optical design and an active compensation method for a Blu-ray pickup head system with a liquid crystal (LC) element. Different from traditional pickup lens design, this new optical design delivers performance as good as the conventional one but has more room for tolerance control, which plays a role in antishaking devices, such as portable Blu-ray players. A hole-pattern electrode and LC optics with external voltage input were employed to generate a symmetric nonuniform electrical field in the LC layer that directs LC molecules into the appropriate gradient refractive index distribution, resulting in the convergence or divergence of specific light beams. LC optics deliver fast and, most importantly, active compensation through optical design when errors occur. Simulations and tolerance analysis were conducted using Code V software, including various tolerance analyses, such as defocus, tilt, and decenter, and their related compensations. Two distinct Blu-ray pickup head system designs were examined in this study. In traditional Blu-ray pickup head system designs, the aperture stop is always set on objective lenses. In the study, the aperture stop is on the LC lens as a newly developed lens. The results revealed that an optical design with aperture stop set on the LC lens as an active compensation device successfully eliminated up to 57% of coma aberration compared with traditional optical designs so that this pickup head lens design will have more space for tolerance control.

Impact of a cometary outburst on its ionosphere. Rosetta Plasma Consortium observations of the outburst exhibited by comet 67P/Churyumov-Gerasimenko on 19 February 2016

NASA Astrophysics Data System (ADS)

Hajra, R.; Henri, P.; Vallières, X.; Galand, M.; Héritier, K.; Eriksson, A. I.; Odelstad, E.; Edberg, N. J. T.; Burch, J. L.; Broiles, T.; Goldstein, R.; Glassmeier, K. H.; Richter, I.; Goetz, C.; Tsurutani, B. T.; Nilsson, H.; Altwegg, K.; Rubin, M.

2017-11-01

We present a detailed study of the cometary ionospheric response to a cometary brightness outburst using in situ measurements for the first time. The comet 67P/Churyumov-Gerasimenko (67P) at a heliocentric distance of 2.4 AU from the Sun, exhibited an outburst at 1000 UT on 19 February 2016, characterized by an increase in the coma surface brightness of two orders of magnitude. The Rosetta spacecraft monitored the plasma environment of 67P from a distance of 30 km, orbiting with a relative speed of 0.2 m s-1. The onset of the outburst was preceded by pre-outburst decreases in neutral gas density at Rosetta, in local plasma density, and in negative spacecraft potential at 0950 UT. In response to the outburst, the neutral density increased by a factor of 1.8 and the local plasma density increased by a factor of 3, driving the spacecraft potential more negative. The energetic electrons (tens of eV) exhibited decreases in the flux of factors of 2 to 9, depending on the energy of the electrons. The local magnetic field exhibited a slight increase in amplitude ( 5 nT) and an abrupt rotation ( 36.4°) in response to the outburst. A weakening of 10-100 mHz magnetic field fluctuations was also noted during the outburst, suggesting alteration of the origin of the wave activity by the outburst. The plasma and magnetic field effects lasted for about 4 h, from 1000 UT to 1400 UT. The plasma densities are compared with an ionospheric model. This shows that while photoionization is the main source of electrons, electron-impact ionization and a reduction in the ion outflow velocity need to be accounted for in order to explain the plasma density enhancement near the outburst peak.

Analytical model of tilted driver–pickup coils for eddy current nondestructive evaluation

NASA Astrophysics Data System (ADS)

Cao, Bing-Hua; Li, Chao; Fan, Meng-Bao; Ye, Bo; Tian, Gui-Yun

2018-03-01

A driver-pickup probe possesses better sensitivity and flexibility due to individual optimization of a coil. It is frequently observed in an eddy current (EC) array probe. In this work, a tilted non-coaxial driver-pickup probe above a multilayered conducting plate is analytically modeled with spatial transformation for eddy current nondestructive evaluation. Basically, the core of the formulation is to obtain the projection of magnetic vector potential (MVP) from the driver coil onto the vector along the tilted pickup coil, which is divided into two key steps. The first step is to make a projection of MVP along the pickup coil onto a horizontal plane, and the second one is to build the relationship between the projected MVP and the MVP along the driver coil. Afterwards, an analytical model for the case of a layered plate is established with the reflection and transmission theory of electromagnetic fields. The calculated values from the resulting model indicate good agreement with those from the finite element model (FEM) and experiments, which validates the developed analytical model. Project supported by the National Natural Science Foundation of China (Grant Nos. 61701500, 51677187, and 51465024).

The role of charge-exchange cross-section for pickup protons and neutrals in the inner heliosheath

NASA Astrophysics Data System (ADS)

Chalov, S. V.

2018-06-01

The process of deceleration of the solar wind downstream of the termination shock is studied on the basis of a one-dimensional multi-component model. It is assumed that the solar wind consists of thermal protons, electrons and interstellar pickup protons. The protons interact with interstellar hydrogen atoms by charge-exchange. Two cases are considered. In the first one, the charge-exchange cross-section for thermal protons and hydrogen atoms is the same as for pickup protons and atoms. Under this condition, there is a strong dependence of the solar wind velocity on the downstream temperature of pickup protons. When the proton temperature is close to 10 keV, the change in the velocity with the distance from the termination shock is similar to that measured on the Voyager 1 spacecraft: linear velocity decrease is accompanied by an extended transition region with near-zero velocity. However, with a more careful approach to the choice of the charge-exchange cross-section, the situation changes dramatically. The strong dependence of the solar wind speed on the pickup proton temperature disappears and the transition region in the heliosheath disappears as well, at least at reasonable distances from the TS.

The influence of Mars' magnetic topology on atmospheric escape

NASA Astrophysics Data System (ADS)

Curry, S.; Luhmann, J. G.; DiBraccio, G. A.; Dong, C.; Xu, S.; Mitchell, D.; Gruesbeck, J.; Espley, J. R.; Connerney, J. E. P.; McFadden, J. P.; Ma, Y. J.; Brain, D.

2017-12-01

At weakly magnetized planets such as Mars and Venus, the solar wind directly interacts with the upper atmosphere where ions can be picked up and swept away by the background convection electric field. These pick-up ions have a gyroradius on the planetary scale that is largely dominated by the interplanetary magnetic field (IMF). But at Mars, their trajectory is also influenced by the existence of remanent crustal magnetic fields, which are thought to create a shielding effect for escaping planetary ions when they are on the dayside. Consequently, the magnetic topology changes at Mars as magnetic reconnection occurs between the draped (IMF) and the crustal magnetic fields (closed). The resulting topology includes open field lines in the solar wind with one footprint attached to the planet. Using magnetohydrodynamic (MHD) and test particle simulations, we will explore the influence of the magnetic topology on ion escape. We will present escape rates for planetary ions for different crustal field positions during different IMF configurations, with +/-BY and +/-BZ components in the Mars Sun Orbit (MSO) coordinate system. We will also compare global maps of ion outflow and escape with open / closed magnetic field line maps and compare our results with ion fluxes and magnetic field data from the Mars Atmospheric and Volatile EvolutioN (MAVEN) mission. Our results relating the dynamic magnetic field topology at Mars and planetary ion escape are an important aspect of magnetospheric physics and planetary evolution, both of which have applications to our own solar system and the increasing number of exoplanets discovered every year.

Influence of the Interplanetary Convective Electric Field on the Distribution of Heavy Pickup Ions Around Mars

NASA Astrophysics Data System (ADS)

Johnson, B. C.; Liemohn, M. W.; Fränz, M.; Ramstad, R.; Stenberg Wieser, G.; Nilsson, H.

2018-01-01

This study obtains a statistical representation of 2-15 keV heavy ions outside of the Martian-induced magnetosphere and depicts their organization by the solar wind convective electric field (ESW). The overlap in the lifetime of Mars Global Surveyor (MGS) and Mars Express (MEX) provides a period of nearly three years during which magnetometer data from MGS can be used to estimate the direction of ESW in order to better interpret MEX ion data. In this paper we use MGS estimates of ESW to express MEX ion measurements in Mars-Sun-Electric field (MSE) coordinates. A new methodological technique used in this study is the limitation of the analysis to a particular instrument mode for which the overlap between proton contamination and plume observations is rare. This allows for confident energetic heavy ion identification outside the induced magnetosphere boundary. On the dayside, we observe high count rates of 2-15 keV heavy ions more frequently in the +ESW hemisphere (+ZMSE) than in the -ESW hemisphere, but on the nightside the reverse asymmetry was found. The results are consistent with planetary origin ions being picked up by the solar wind convective electric field. Though a field of view hole hinders quantification of plume fluxes and velocity space, this new energetic heavy ion identification technique means that Mars Express should prove useful in expanding the time period available to assess general plume loss variation with drivers.

Evolution of carbonaceous chondrite parent bodies: Insights into cometary nuclei

NASA Technical Reports Server (NTRS)

Mcsween, Harry Y., Jr.

1989-01-01

It is thought that cometary samples will comprise the most primitive materials that are able to be sampled. Although parent body alteration of such samples would not necessarily detract from scientists' interest in them, the possibility exists that modification processes may have affected cometary nuclei. Inferences about the kinds of modifications that might be encountered can be drawn from data on the evolution of carbonaceous chondrite parent bodies. Observations suggest that, of all the classes of chondrites, these meteorites are most applicable to the study of comets. If the proportion of possible internal heat sources such as Al-26 in cometary materials are similar to those in chondrites, and if the time scale of comet accretion was fast enough to permit incorporation of live radionuclides, comets might have had early thermal histories somewhat like those of carbonaceous chondrite parent bodies.

Cometary and meteorite swarm impact on planetary surfaces

NASA Technical Reports Server (NTRS)

Okeefe, J. D.; Ahrens, T. J.

1982-01-01

The impact-induced deformation from hypothetical cometary objects having initial densities in the 0.01 to 1 g/cu cm range and heats of vaporization in the approximately 2 kJ/g (corresponding to water) to approximately 10 to the 7th J/g range is examined for impacts in the 5 to 45 km/s range. Even though the direct effect of an atmosphere is neglected, the atmosphere may in fact cause a cometary object to break up into a shower or equivalent very porous impactor. Besides examining the partitioning of impact energy into internal energy of the impacted planet and impacting cometary material, calculations are made of the relative efficiency of shock-induced melting and vaporization by comets on planetary surface materials and the mass loss from a given planet for various escape velocities.

Hummingbird Comet Nucleus Analysis Mission

NASA Technical Reports Server (NTRS)

Kojiro, Daniel; Carle, Glenn C.; Lasher, Larry E.

2000-01-01

Hummingbird is a highly focused scientific mission, proposed to NASA s Discovery Program, designed to address the highest priority questions in cometary science-that of the chemical composition of the cometary nucleus. After rendezvous with the comet, Hummingbird would first methodically image and map the comet, then collect and analyze dust, ice and gases from the cometary atmosphere to enrich characterization of the comet and support landing site selection. Then, like its namesake, Hummingbird would carefully descend to a pre-selected surface site obtaining a high-resolution image, gather a surface material sample, acquire surface temperature and then immediately return to orbit for detailed chemical and elemental analyses followed by a high resolution post-sampling image of the site. Hummingbird s analytical laboratory contains instrumentation for a comprehensive molecular and elemental analysis of the cometary nucleus as well as an innovative surface sample acquisition device.

Triple F - A Comet Nucleus Sample Return Mission

NASA Technical Reports Server (NTRS)

Kueppers, Michael; Keller, Horst Uwe; Kuhrt, Ekkehard; A'Hearn, Michael; Altwegg, Kathrin; Betrand, Regis; Busemann, Henner; Capria, Maria Teresa; Colangeli, Luigi

2008-01-01

The Triple F (Fresh From the Fridge) mission, a Comet Nucleus Sample Return, has been proposed to ESA s Cosmic Vision program. A sample return from a comet enables us to reach the ultimate goal of cometary research. Since comets are the least processed bodies in the solar system, the proposal goes far beyond cometary science topics (like the explanation of cometary activity) and delivers invaluable information about the formation of the solar system and the interstellar molecular cloud from which it formed. The proposed mission would extract three samples of the upper 50 cm from three locations on a cometary nucleus and return them cooled to Earth for analysis in the laboratory. The simple mission concept with a touch-and-go sampling by a single spacecraft was proposed as an M-class mission in collaboration with the Russian space agency ROSCOSMOS.

Triple F - A Comet Nucleus Sample Return Mission

NASA Technical Reports Server (NTRS)

Kueppers, Michael; Keller, H. U.; Kuehrt, E.; A'Hearn, M. F.; Altwegg, K.; Bertrand, R.; Busemann, H.; Capria, M. T.; Colangeli, L.; Davidsson, B.;

Verification test of the Battronic Truck Volta Electric Pickup. Report for Jul 80-Jan 81

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dowgiallo, E.J. Jr; Snellings, I.R.; Chapman, R.D.

1982-04-01

The Volta Pickup is an electric 1/2-ton truck manufactured by the Battronic Truck Co. It was tested by MERADCOM at Fort Belvoir, Virginia as part of a Department of Energy project to verify conformity to performance standards of electric vehicles. The verification test results are presented in this report. The Volta Pickup is powered by 24 6-V lead-acid batteries, has a 38 hp series wound d.c. motor, SCR chopper controller, regenerative braking, and a 2-speed Helical gear transmission.

The cryogenic storage ring CSR

NASA Astrophysics Data System (ADS)

von Hahn, R.; Becker, A.; Berg, F.; Blaum, K.; Breitenfeldt, C.; Fadil, H.; Fellenberger, F.; Froese, M.; George, S.; Göck, J.; Grieser, M.; Grussie, F.; Guerin, E. A.; Heber, O.; Herwig, P.; Karthein, J.; Krantz, C.; Kreckel, H.; Lange, M.; Laux, F.; Lohmann, S.; Menk, S.; Meyer, C.; Mishra, P. M.; Novotný, O.; O'Connor, A. P.; Orlov, D. A.; Rappaport, M. L.; Repnow, R.; Saurabh, S.; Schippers, S.; Schröter, C. D.; Schwalm, D.; Schweikhard, L.; Sieber, T.; Shornikov, A.; Spruck, K.; Sunil Kumar, S.; Ullrich, J.; Urbain, X.; Vogel, S.; Wilhelm, P.; Wolf, A.; Zajfman, D.

2016-06-01

An electrostatic cryogenic storage ring, CSR, for beams of anions and cations with up to 300 keV kinetic energy per unit charge has been designed, constructed, and put into operation. With a circumference of 35 m, the ion-beam vacuum chambers and all beam optics are in a cryostat and cooled by a closed-cycle liquid helium system. At temperatures as low as (5.5 ± 1) K inside the ring, storage time constants of several minutes up to almost an hour were observed for atomic and molecular, anion and cation beams at an energy of 60 keV. The ion-beam intensity, energy-dependent closed-orbit shifts (dispersion), and the focusing properties of the machine were studied by a system of capacitive pickups. The Schottky-noise spectrum of the stored ions revealed a broadening of the momentum distribution on a time scale of 1000 s. Photodetachment of stored anions was used in the beam lifetime measurements. The detachment rate by anion collisions with residual-gas molecules was found to be extremely low. A residual-gas density below 140 cm-3 is derived, equivalent to a room-temperature pressure below 10-14 mbar. Fast atomic, molecular, and cluster ion beams stored for long periods of time in a cryogenic environment will allow experiments on collision- and radiation-induced fragmentation processes of ions in known internal quantum states with merged and crossed photon and particle beams.

The cryogenic storage ring CSR.

PubMed

von Hahn, R; Becker, A; Berg, F; Blaum, K; Breitenfeldt, C; Fadil, H; Fellenberger, F; Froese, M; George, S; Göck, J; Grieser, M; Grussie, F; Guerin, E A; Heber, O; Herwig, P; Karthein, J; Krantz, C; Kreckel, H; Lange, M; Laux, F; Lohmann, S; Menk, S; Meyer, C; Mishra, P M; Novotný, O; O'Connor, A P; Orlov, D A; Rappaport, M L; Repnow, R; Saurabh, S; Schippers, S; Schröter, C D; Schwalm, D; Schweikhard, L; Sieber, T; Shornikov, A; Spruck, K; Sunil Kumar, S; Ullrich, J; Urbain, X; Vogel, S; Wilhelm, P; Wolf, A; Zajfman, D

2016-06-01

An electrostatic cryogenic storage ring, CSR, for beams of anions and cations with up to 300 keV kinetic energy per unit charge has been designed, constructed, and put into operation. With a circumference of 35 m, the ion-beam vacuum chambers and all beam optics are in a cryostat and cooled by a closed-cycle liquid helium system. At temperatures as low as (5.5 ± 1) K inside the ring, storage time constants of several minutes up to almost an hour were observed for atomic and molecular, anion and cation beams at an energy of 60 keV. The ion-beam intensity, energy-dependent closed-orbit shifts (dispersion), and the focusing properties of the machine were studied by a system of capacitive pickups. The Schottky-noise spectrum of the stored ions revealed a broadening of the momentum distribution on a time scale of 1000 s. Photodetachment of stored anions was used in the beam lifetime measurements. The detachment rate by anion collisions with residual-gas molecules was found to be extremely low. A residual-gas density below 140 cm(-3) is derived, equivalent to a room-temperature pressure below 10(-14) mbar. Fast atomic, molecular, and cluster ion beams stored for long periods of time in a cryogenic environment will allow experiments on collision- and radiation-induced fragmentation processes of ions in known internal quantum states with merged and crossed photon and particle beams.

The prescription pickup lag, an automatic prescription refill program, and community pharmacy operations.

PubMed

Lester, Corey A; Chui, Michelle A

2016-01-01

To determine the effect of an automatic prescription refill program on the prescription pickup lag in community pharmacy. A post-only quasi-experimental design comparing automatic and manual refill prescription cohorts for each of the 3 Centers for Medicare and Medicaid medication adherence metrics. A 29-store community pharmacy chain in the Midwest. Community-dwelling patients over the age of 65 years receiving prescription medications included in the statin, renin-angiotensin-aldosterone system antagonist, or non-insulin diabetes adherence metrics. An automatic prescription refill program that initiated prescription refills on a standardized, recurrent basis, eliminating the need for patients to phone in or drop off prescription refills. The prescription pickup lag, defined as the number of days between a prescription being adjudicated in the pharmacy and the prescription being picked up by the patient. A total of 37,207 prescription fills were examined. There were 20.5%, 22.4%, and 23.3% of patients enrolled in the automatic prescription refill program for the statin, renin-angiotensin-aldosterone system antagonist, and diabetes adherence metrics, respectively. Prescriptions in the automatic prescription refill cohorts experienced a median pickup lag of 7 days compared with 1 day for the manual refill prescriptions. 35.2% of all manual refill prescriptions had a pickup lag of 0 days compared with 13% for automatic refills. However, 15.4% of automatic prescription refills had a pickup lag of greater than 14 days, compared with 4.8% of manual refills. Prescriptions in the automatic prescription refill programs were associated with a significantly longer amount of time in the pharmacy before being picked up by the patient. This increased pickup lag may contribute positively by smoothing out workload demands of pharmacy staff, but may contribute negatively owing to an increased amount of rework and greater inventory requirements. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Developing a model law restricting the transporting of passengers in the cargo areas of pickup trucks.

PubMed

Christoffel, T; Agran, P; Winn, D; Anderson, C; Del Valle, C

2000-01-01

Pickup trucks have become increasingly popular in the United States, accounting for about one in five vehicles involved in fatal motor-vehicle crashes. A critical factor in these deaths is the practice of carrying passengers in truck cargo areas, which are not designed for this purpose. Each year approximately 200 deaths occur to occupants riding in the back of pickup trucks. Over half the states have laws dealing with preventable injury problem, but these laws vary widely and most are too limited to be effective. We have reviewed existing laws, as well as crash injury data, and we have developed and recommend a model bill. The bill focuses on intended use, restricting passengers to only those portions of a vehicle designed for human transport. We have also conducted and report on a survey of legislative sponsors of pickup truck legislation.

NEUTRAL ATOM PROPERTIES IN THE DIRECTION OF THE IBEX RIBBON

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heerikhuisen, Jacob; Pogorelov, Nikolai V.; Gamayunov, Konstantin V.

2016-11-10

In this paper, we present results from our three-dimensional (3D) simulations of the interaction between the solar wind and local interstellar medium with an emphasis on the phase-space properties of energetic neutral atoms (ENAs) along a sight line that intersects the ribbon of enhanced ENA flux seen by NASA’s Interstellar Boundary EXplorer spacecraft. The majority of these ENAs have velocities directed away from the heliosphere, but it is believed that interactions between heliospheric ENAs and ions outside the heliosphere may result in a population of secondary ENAs that return to the heliosphere and generate the ribbon. While we do notmore » consider the ion dynamics that result in secondary ENAs, our analysis is of key importance to the process since the heliospheric ENAs we consider form the source population for those ions. We present the moments of the hydrogen distribution, along with moments parallel and perpendicular to the local magnetic field for the pick-up ions (PUIs) that these neutrals generate. Finally, we present gyro-averaged velocity distributions relative to the local magnetic field for the PUIs created from our simulated H-atoms, along with analytic fits to these distributions in the secondary ENA source region just beyond the heliopause.« less

Variability of the composition of Io's exosphere deduced from the spectrum of ion cyclotron waves

NASA Astrophysics Data System (ADS)

Wang, Y. L.; Russell, C. T.; Raeder, J.; Kivelson, M. G.

2000-10-01

The spectrum of ion cyclotron waves seen during the Io flybys, I0, I24, I25 and I27 is quite varied. On I0 the cyclotron waves had a single strong peak near the gyrofrequency of SO2+. On I24 there were two peaks, one at the SO+ gyrofrequency and one at the SO2+ gyrofrequency, with the former stronger. On I25, the spectrum was similar but the relative strength of the peaks reversed. On I27 the spectrum was similar to I24 with the addition of a broad band centered on the H2S+ gyrofrequency. These varying strength emissions centered at the gyrofrequency of discrete ion gyrofrequencies imply that the chemical composition of the upper atmosphere is quite variable. The strength of the waves also appears to vary from one pass to the next, with the weakest signals occurring furthest from noon solar phase angle. This latter effect may be a geometrical in origin, associated with the varying dayside atmosphere relative to the corotating plasma. A simple model of the ion pickup process and transport of fast neutrals across field lines can explain the observed local time effect, and some of the radial variation of the torus properties.

Plasma Waves Associated with Mass-Loaded Comets

NASA Technical Reports Server (NTRS)

Tsurutani, Bruce; Glassmeier, Karl-Heinz

2015-01-01

Plasma waves and instabilities are integrally involved with the plasma "pickup" process and the mass loading of the solar wind (thus the formation of ion tails and the magnetic tails). Anisotropic plasmas generated by solar wind-comet interactions (the bow shock, magnetic field pileup) cause the generation of plasma waves which in turn "smooth out" these discontinuities. The plasma waves evolve and form plasma turbulence. Comets are perhaps the best "laboratories" to study waves and turbulence because over time (and distance) one can identify the waves and their evolution. We will argue that comets in some ways are better laboratories than magnetospheres, interplanetary space and fusion devices to study nonlinear waves and their evolution.

Observations of solar wind ion charge exchange in the comet Halley coma

NASA Technical Reports Server (NTRS)

Fuselier, S. A.; Shelley, E. G.; Goldstein, B. E.; Goldstein, R.; Neugebauer, M.; Ip, W.-H.; Balsiger, H.; Reme, H.

1991-01-01

Giotto Ion Mass Spectrometer/High Energy Range Spectrometer (IMS/HERS) observations of solar wind ions show charge exchange effects and solar wind compositional changes in the coma of comet Halley. As the comet was approached, the He(++) to proton density ratio increased until about 1 hour before closest approach after which time it decreased. Abrupt increases in this ratio were also observed in the beginning and near the end of the so-called Mystery Region (8.6 - 5.5(10)(exp 5) km from the comet along the spacecraft trajectory). These abrupt increases in the density ratio were well correlated with enhanced fluxes of keV electrons as measured by the Giotto plasma electron spectrometer. The general increase and then decrease of the He(++) to proton density ratio is quantitatively consistent with a combination of the addition of protons of cometary origin to the plasma and loss of plasma through charge exchange of protons and He(++). In general agreement with the solar wind proton and He(++) observations, solar wind oxygen and carbon ions were observed to charge exchange from higher to lower charge states with decreasing distance to the comet. The more abrupt increases in the He(++) to proton and the He(++) to O(6+) density ratios in the mystery region require a change in the solar wind ion composition in this region while the correlation with energetic electrons indicates processes associated with the comet.

Comment on the Pioneer Venus Orbiter event of February 11, 1982 - Of cometary or solar origin?

NASA Technical Reports Server (NTRS)

Intriligator, D. S.

1986-01-01

The evidence presented by Russell et al. (1985) for the cometary origin of the Pioneer Venus Orbiter event of Febr. 11, 1982, is examined critically. It is argued that the field fluctuations and He enhancements seen at Venus and near earth, the sequence of the events, and a number of related observations all indicate that the event is of solar origin. These objections are discussed individually in a reply by Russell et al., and the claim of cometary origin is defended.

Carbon monoxide poisoning in children riding in the back of pickup trucks.

PubMed

Hampson, N B; Norkool, D M

OBJECTIVE - To describe the case characteristics of a series of children poisoned with carbon monoxide while traveling in the back of pickup trucks. DESIGN - Pediatric cases referred for treatment of carbon monoxide poisoning with hyperbaric oxygen between 1986 and 1991 were reviewed. Those cases that occurred during travel in the back of pickup trucks were selected. Clinical follow-up by telephone interview ranged from 2 to 55 months. SETTING - A private, urban, tertiary care center in Seattle, Wash. PATIENTS - Twenty children ranging from 4 to 16 years of age. INTERVENTION - All patients were treated with hyperbaric oxygen. MAIN OUTCOME MEASURES - Characteristics of the poisoning incident and clinical patient outcome. RESULTS - Of 68 pediatric patients treated for accidental carbon monoxide poisoning, 20 cases occurred as children rode in the back of pickup trucks. In 17 of these, the children were riding under a rigid closed canopy on the rear of the truck, while three episodes occurred as children rode beneath a tarpaulin. Average carboxyhemoglobin level on emergency department presentation was 18.2% +/- 2.4% (mean +/- SEM; range, 1.6% to 37.0%). Loss of consciousness occurred in 15 of the 20 children. One child died of cerebral edema, one had permanent neurologic deficits, and 18 had no recognizable sequelae related to the episode. In all cases, the truck exhaust system had a previously known leak or a tail pipe that exited at the rear rather than at the side of the pickup truck. CONCLUSIONS - Carbon monoxide poisoning is a significant hazard for children who ride in the back of pickup trucks. If possible, this practice should be avoided.

Far ultraviolet excitation processes in comets

NASA Technical Reports Server (NTRS)

Feldman, P. D.; Opal, C. B.; Meier, R. R.; Nicolas, K. R.

1976-01-01

Recent observations of atomic oxygen and carbon in the far ultraviolet spectrum of comet Kohoutek have demonstrated the existence of these atomic species in the cometary coma. However, in order to identify the source of their origin, it is necessary to relate the observed ultraviolet flux to the atomic production rate. Analyses of observed OI wavelength 1304 and CI wavelength 1657 A multiplets have been carried out using high resolution solar spectra. Also examined is the possibility of observing ultraviolet fluorescence from molecules such as CO and H2, as well as resonance scattering either from atomic ions for which there are strong corresponding solar lines (CII) or from atoms for which there is an accidental wavelength coincidence (SI).

The Extreme-ultraviolet Emission from Sun-grazing Comets

NASA Technical Reports Server (NTRS)

Bryans, Paul; Pesnell, William D.

2012-01-01

The Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory has observed two Sun-grazing comets as they passed through the solar atmosphere. Both passages resulted in a measurable enhancement of extreme-ultraviolet (EUV) radiance in several of the AIA bandpasses.We explain this EUV emission by considering the evolution of the cometary atmosphere as it interacts with the ambient solar atmosphere. Molecules in the comet rapidly sublimate as it approaches the Sun. They are then photodissociated by the solar radiation field to create atomic species. Subsequent ionization of these atoms produces a higher abundance of ions than normally present in the corona and results in EUV emission in the wavelength ranges of the AIA telescope passbands.

Infrared Observations of Cometary Dust and Nuclei

NASA Technical Reports Server (NTRS)

Lisse, Carey

2004-01-01

This bibliography lists citations for publications published under the grant. Subjects of the publications include cometary dust, instellar and interplanetary dust, comet nuclei and comae, Comet Hale-Bopp, infrared observations of comets, mass loss, and comet break-up.

MIRO Computational Model

NASA Technical Reports Server (NTRS)

Broderick, Daniel

2010-01-01

A computational model calculates the excitation of water rotational levels and emission-line spectra in a cometary coma with applications for the Micro-wave Instrument for Rosetta Orbiter (MIRO). MIRO is a millimeter-submillimeter spectrometer that will be used to study the nature of cometary nuclei, the physical processes of outgassing, and the formation of the head region of a comet (coma). The computational model is a means to interpret the data measured by MIRO. The model is based on the accelerated Monte Carlo method, which performs a random angular, spatial, and frequency sampling of the radiation field to calculate the local average intensity of the field. With the model, the water rotational level populations in the cometary coma and the line profiles for the emission from the water molecules as a function of cometary parameters (such as outgassing rate, gas temperature, and gas and electron density) and observation parameters (such as distance to the comet and beam width) are calculated.

Cometary material and the origins of life on earth

NASA Technical Reports Server (NTRS)

Lazcano-Araujo, A.; Oro, J.

1981-01-01

The role of cometary material in determining the environmental conditions of the prebiotic earth is reviewed. The organic synthesis pathways that occur in dense interstellar clouds and in comets are examined, and complex organic molecules believed to exist (amino acids, carboxylic acids, purines, pyrimidines and hydrocarbons) based on spectral detections of degradation products are noted. Estimates of the amount of terrestrial volatiles of cometary origin that may have been acquired in collisions during the early history of the earth are considered, and shown to dominate any estimated contributions to terrestrial carbon from other extraterrestrial sources. Current evidence that the origin and early evolution of life began about four billion years ago is discussed in relation to the cometary bombardment processes occurring at the time and the resultant shock waves, reducing atmospheres and reactive chemical species. It is thus concluded that comets contributed significantly to the processes of chemical evolution necessary for the emergence of life on earth.

Cometary globules in the southeast quadrant of the Rosette nebula

NASA Technical Reports Server (NTRS)

Patel, Nimesh A.; Xie, Taoling; Goldsmith, Paul F.

1993-01-01

We present a study of newly identified cometary globules in the southeast quadrant of the Rosette nebula using the J = 1-0 transition of carbon monoxide. The globules are found to be blueshifted by about 6 km/s with respect to the adjacent Rosette molecular cloud. The masses of the globules vary from 50 to 300 solar masses, and their sizes are between 1 and 3 pc. Two of the globules have cometary morphology and show velocity gradients of about 1.5 km/s/pc along their symmetry axes. These globules are associated with the IRAS sources 06314+0421, X0632+043, 06322+0427, and 06327+0423 which coincide with local maxima in the (C-13)O emission. The derived physical parameters of the globules are found to be consistent with those predicted by recent theoretical models of photoevaporating cometary clouds. We suggest that star formation induced by radiation driven implosion has occurred.

Gas Dynamics and Kinetics in the Cometary Coma: Theory and Observations

NASA Technical Reports Server (NTRS)

Combi, Michael R.; Harris, Walter M.; Smyth, William H.

2005-01-01

Our ability to describe the physical state of the expanding coma affects fundamental areas of cometary study both directly and indirectly. In order to convert measured abundances of gas species in the coma to gas production rates, models for the distribution and kinematics of gas species in the coma are required. Conversely, many different types of observations, together with laboratory data and theory, are still required to determine coma model attributes and parameters. Accurate relative and absolute gas production rates and their variations with time and from comet to comet are crucial to our basic understanding of the composition and structure of cometary nuclei and their place in the solar system. We review the gas dynamics and kinetics of cometary comae from both theoretical and observational perspectives, which are important for understanding the wide variety of physical conditions that are encountered.

The volatile composition of comets

NASA Technical Reports Server (NTRS)

Weaver, H. A.

1988-01-01

Comets may be our best probes of the physical and chemical conditions in the outer regions of the solar nebula during that crucial period when the planets formed. The volatile composition of cometary nuclei can be used to decide whether comets are the product of a condensation sequence similar to that invoked to explain the compositions of the planets and asteroids, or if comets are simply agglomerations of interstellar grains which have been insignificantly modified by the events that shaped the other bodies in the solar system. Although cometary nuclei are not generally accessible to observation, observations of cometary comae can illuminate at least some of the mysteries of the nuclei provided one has a detailed knowledge of the excitation conditions in the coma and also has access to basic atomic and molecular data on the many species present in comets. Examined here is the status of our knowledge of the volatile composition of cometary nuclei and how these data are obtained.

First results from the Giotto magnetometer experiment at comet Halley

NASA Technical Reports Server (NTRS)

Neubauer, F. M.; Glassmeier, K. H.; Pohl, M.; Raeder, J.; Acuna, M. H.; Burlaga, L. F.; Ness, N. F.

1986-01-01

The Giotto magnetometer experiment at comet Halley has for the first time provided magnetic field measurements in all the important spatial regions characterizing the front-side interaction between the solar-wind magnetoplasma and a cometary atmosphere. Upstream waves of cometary origin have been observed at distances greater than two million km from the comet, both inbound and outbound. A cometary bow shock has been identified at 1.15 million inbound on the dawn side and a thick quasi-parallel cometary bow shock outbound. A turbulent magnetosheath has been observed further inside. A magnetic pile-up region has been identified inside 135,000 km, inbound, and 263,000 km, outbound, with fields up to 57 and 65 nT, respectively. A cavity region with essentially zero magnetic field has been discovered, with a width of 8500 km along the trajectory around closest approach.

Comet Shoemaker-Levy-9 impact with Jupiter: Aeronomical predictions

NASA Technical Reports Server (NTRS)

Cravens, T. E.

1994-01-01

The fragments of comet Shoemaker-Levy-9 will enter the atmosphere of Jupiter during July 20-26, 1994. Significant amounts of water vapor will be injected into the upper atmosphere of Jupiter either from the comet itself or from the lower atmosphere of Jupiter. The photochemistry of both the neutral gas and the ionosphere will be greatly altered by the influx of this water vapor or the atomic oxygen generated by the dissociation of the water. Enhanced abundances of H2O (or other species such as NH3) in the atmosphere above the homopause should persist for at least a year and should be globally distributed. The odd oxygen (i.e., O or H2O or OH) associated with the cometary water influx alters the ion chemistry by removing H(+) ions, which also has the effect of reducing the ionospheric electron density because H(+) is ordinarily the main ion species in the Jovian ionosphere. The density of H3(+), both in the auroral and non-auroral ionosphere, will also be reduced due to presence of water. This ion species has been detected spectroscopically at Jupiter, and a drop in its abundance should be detectable. The major ion species will become H3O(+) which could reach a peak density as high as 10(exp 4)/cu cm in the non-auroral ionosphere and 10(exp 5)/cu cm in the auroral ionosphere. It should be possible to detect this ion species spectroscopically from Earth-based observatories.

Hybrid Simulations for the Turbulence and the Wave-Particle Interaction in the Inner and the Outer Heliopause.

NASA Astrophysics Data System (ADS)

Kucharek, H.; Pogorelov, N. V.; Mueller, H. R.; Gamayunov, K. V.

2014-12-01

IBEX and the Voyager spacecraft provide unique data sets that enable us to study plasma conditions in the key regions of the heliosphere: the termination shock (TS), at the heliospause and beyond. Whereas Voyager provides in-situ plasma data IBEX uses neutral atoms to remote sense the plasma conditions in interstellar space, the heliopause, and the termination shock. The IBEX data sets revealed a ribbon feature which was unexpected and which formation mechanism is still unknown. Even the location of the source is not known considering the fact that IBEX measures neutral along a line of sight. Aside from the ribbon feature the distributed ENA flux shows temporal variations that are unexplained, in particular at solar wind energies. Furthermore, Voyager observations questioned the role of the termination shock being the main accelerator for high-energetic ions. All of these outstanding science questions are associated with wave-particle interaction and turbulence in most likely different key regions of the heliosphere. Hybrid simulations, which included all kinetic processes self-consistently on the ion level, are a proven to be a very powerful tool to investigate wave-particle interaction, turbulence, and phase-space evolution of pickup and solar wind ions. We performed 3D multi-species hybrid simulations for an ion/ion beam instability to study the temporal evolution of ion distributions, their stability, and the associated ENA generation under the influence of self-generated waves in the heliosheath. We investigated the energetization of ions downstream of the TS, the turbulence, and growth rate of instabilities in the heliosheath. The simulations show that ions can be accelerated downstream of the TS by trapping ions in coherent wave fronts.

Modeling Solar Wind Flow with the Multi-Scale Fluid-Kinetic Simulation Suite

DOE PAGES

Pogorelov, N.V.; Borovikov, S. N.; Bedford, M. C.; ...

2013-04-01

Multi-Scale Fluid-Kinetic Simulation Suite (MS-FLUKSS) is a package of numerical codes capable of performing adaptive mesh refinement simulations of complex plasma flows in the presence of discontinuities and charge exchange between ions and neutral atoms. The flow of the ionized component is described with the ideal MHD equations, while the transport of atoms is governed either by the Boltzmann equation or multiple Euler gas dynamics equations. We have enhanced the code with additional physical treatments for the transport of turbulence and acceleration of pickup ions in the interplanetary space and at the termination shock. In this article, we present themore » results of our numerical simulation of the solar wind (SW) interaction with the local interstellar medium (LISM) in different time-dependent and stationary formulations. Numerical results are compared with the Ulysses, Voyager, and OMNI observations. Finally, the SW boundary conditions are derived from in-situ spacecraft measurements and remote observations.« less

Titan's Variable Plasma Interaction

NASA Astrophysics Data System (ADS)

Ledvina, S. A.; Brecht, S. H.

2015-12-01

Cassini observations have found that the plasma and magnetic field conditions upstream of Titan are far more complex than they were thought to be after the Voyager encounter. Rymer et al., (2009) used the Cassini Plasma Spectrometer (CAPS) electron observations to classify the plasma conditions along Titan's orbit into 5 types (Plasma Sheet, Lobe, Mixed, Magnetosheath and Misc.). Nemeth et al., (2011) found that the CAPS ion observations could also be separated into the same plasma regions as defined by Rymer et al. Additionally the T-96 encounter found Titan in the solar wind adding a sixth classification. Understanding the effects of the variable upstream plasma conditions on Titan's plasma interaction and the evolution of Titan's ionosphere/atmosphere is one of the main objectives of the Cassini mission. To compliment the mission we perform hybrid simulations of Titan's plasma interaction to examine the effects of the incident plasma distribution function and the flow velocity. We closely examine the results on Titan's induced magnetosphere and the resulting pickup ion properties.

Microelectromechanical power generator and vibration sensor

DOEpatents

Roesler, Alexander W [Tijeras, NM; Christenson, Todd R [Albuquerque, NM

2006-11-28

A microelectromechanical (MEM) apparatus is disclosed which can be used to generate electrical power in response to an external source of vibrations, or to sense the vibrations and generate an electrical output voltage in response thereto. The MEM apparatus utilizes a meandering electrical pickup located near a shuttle which holds a plurality of permanent magnets. Upon movement of the shuttle in response to vibrations coupled thereto, the permanent magnets move in a direction substantially parallel to the meandering electrical pickup, and this generates a voltage across the meandering electrical pickup. The MEM apparatus can be fabricated by LIGA or micromachining.

Charge exchange in slow collisions of Si3+ with H

NASA Astrophysics Data System (ADS)

Joseph, D. C.; Saha, B. C.

2010-10-01

Low energy electron capture from atomic hydrogen by multi-charged ions continues to be of interest and has wide applications including both magnetically confined^ fusion and astrophysical plasmas. The charge exchange process reported here, Si^3+ + H -- Si^2+ + H^+ is an important destruction mechanism of Si^3+ in photo-ionized gas. The soft X-ray emission from comets has been explained by charge transfer of solar wind ions, among them Si^3+, with neutrals in the cometary gas vapor. The state selective cross sections are evaluated using the semi-classical molecular orbital close coupling (MOCC) [1] methods. Adiabatic potentials and wave functions for a number of low-lying singlet and triplet states are calculated using the MRD-CI package [2]. Details will be presented at the conference. [1] M. Kimura and N. F. Lane, At. Mol. Opt. Phys 26, 79 (1990). [3] R. J. Buenker, ``Current Aspects of Quantum Chemistry'' 1981, Vol 21, edited by R. Carbo (Elsevier, Amsterdam) p 17.

International Halley Watch: Discipline specialists for near-nucleus studies

NASA Technical Reports Server (NTRS)

Larson, S.; Sekanina, Z.; Rahe, J.

1986-01-01

The purpose of the Near-Nucleus Studies Net is to study the processes taking place in the near-nucleus environment as they relate to the nature of nucleus. This is accomplisghed by measuring the spatial and temporal distribution of dust, gases and ions in the coma on high resolution images taken from many observatories around the world. By modeling the motions of discrete dust features in Comet Halley, it is often possible to determine the locations of the emission sources on the surface and learn about the nucleus structure. In addition to the general goals shared by all IHW nets, the scientific goals of the net has been to determine (1)the gross surface structure of the nucleus, (2)the nucleus spin vector, (3)the distribution and evolution of jet sources and (4)the interrelationships between the gas, dust and ion components of the coma. An additional Comet Giacobini-Zinner watch was carried out by the NNSN in support of the NASA International Cometary Explorer flyby.

Strong CO+ and {{\\rm{N}}}_{2}^{+} Emission in Comet C/2016 R2 (Pan-STARRS)

NASA Astrophysics Data System (ADS)

Cochran, Anita L.; McKay, Adam J.

2018-02-01

We report on imaging and spectroscopic observations of comet C/2016 R2 (Pan-STARRS) obtained with the 0.8 m and 2.7 m telescopes of McDonald Observatory in 2017 November and December, respectively. The comet was at a heliocentric distance greater than 3 au during both sets of observations. The images showed a well-developed tail with properties that suggested it was an ion tail. The spectra confirmed that we were observing well-developed bands of CO+ and {{{N}}}2+. The {{{N}}}2+ detection was unequivocally cometary and was one of the strongest bands of {{{N}}}2+ detected in a comet spectrum. We derived the ratio of these two ions and from that we were able to derive that N2/CO = 0.15. This is the highest such ratio reported for a comet. This Letter includes data taken at The McDonald Observatory of The University of Texas at Austin.

Electron plasma environment at comet Grigg-Skjellerup: General observations and comparison with the environment at comet Halley

NASA Technical Reports Server (NTRS)

Reme, H.; Mazelle, C.; Sauvaud, J. A.; D'Uston, C.; Froment, F.; Lin, R. P.; Anderson, K. A.; Carlson, C. W.; Larson, D. E.; Korth, A.

1993-01-01

The three-dimensional electron spectrometer of the Reme plasma analyzer-complete positive ion, electron and ram negative ion measurements near comet Halley (RPA-COPERNIC) experiment aboard the Giotto spacecraft, although damaged during the comet Halley encounter in March 1986, has provided very new results during the encounter on July 10, 1992, with the weakly active comet Grigg-Skjellerup (G-S). The main characteristic features of the highly structured interaction region extending from approximately 26,500 km inbound to approximately 37,200 km outbound are presented. These results are compared to the results obtained by the same instrument during the Giotto comet Halley fly-by. Despite the large difference in the size of the interaction regions (approximately 60,000 km for G-S, approximately 2000,000 km for Halley) due to 2 orders of magnitude difference in cometary neutral gas production rate, there are striking similarities in the solar wind interactions with the two comets.

The Hummingbird GC-IMS: In Situ Analysis of a Cometary Nucleus

NASA Technical Reports Server (NTRS)

Kojiro, Daniel R.; Carle, Glenn C.; Cohen, Martin J.; Wernlund, Roger F.; Stimac, Robert M.; Takeuchi, Norishige; DeVincenzi, Donald L. (Technical Monitor)

2000-01-01

Comets are of enormous scientific interest for many reasons. They are primitive bodies that date back to the earliest stages of solar system formation and, because of their small size and because they have been stored in the outer reaches of the solar system, their pristine nature has been preserved better than for any other class of body. They are extremely rich in highly volatile elements, many in the form of ices, and are richer in organic matter than any other known solar system body. It is strongly suspected that in addition to their content of primordial solar nebular material, they also incorporate unprocessed matter from the interstellar medium. Impacts by comets occur onto all the planets and satellites, often with major consequences (e.g., the dinosaur extinction event at the KIT boundary), or sometimes just providing a spectacular cosmic event (e.g., the collision of comet Shoemaker-Levy 9 with Jupiter). A mission to analyze a cometary nucleus must be capable of detecting and identifying over 30 molecular species among several different chemical groups. The Hummingbird Mission will rendezvous with, orbit, characterize, and make multiple descents to the nucleus of a comet. Hummingbird will employ a Gas Chromatograph - Ion Mobility Spectrometer (GC-IMS) as part-of a suite of sophisticated instruments for a comprehensive in situ elemental, molecular, and isotopic analysis of the comet.

Insight into the molecular composition of laboratory organic residues produced from interstellar/pre-cometary ice analogues using very high resolution mass spectrometry

NASA Astrophysics Data System (ADS)

Danger, G.; Fresneau, A.; Abou Mrad, N.; de Marcellus, P.; Orthous-Daunay, F.-R.; Duvernay, F.; Vuitton, V.; Le Sergeant d'Hendecourt, L.; Thissen, R.; Chiavassa, T.

2016-09-01

Experimental simulations in the laboratory may provide important information about the chemical evolution occurring in various astrophysical objects such as extraterrestrial ices. Interstellar or (pre)cometary ice analogues made of H2O, CH3OH, and NH3 at 77 K, when subjected to an energetic process (VUV photons, electrons or ions) and then warmed-up to room temperature, lead, in the laboratory, to the formation of an organic residue. In this paper we expand our previous analysis of the residues in order to obtain a better insight into their molecular content. Data analyses show that three different chemical groups are present in the residue in the negative electrospray ionization (ESI) mode: CHN, CHO and CHNOsbnd whereas only two groups are detected in the positive ESI mode: CHN and CHNO. In both cases, the CHNO group is the most abundant. The application of specific data treatment shows that residue mainly contains aliphatic linear molecules or cyclic structures connected to unsaturated chemical functions such as esters, carboxylic acids, amides or aldehydes. In lower abundances, some molecules do present aromatic structures. The comparison of our residue with organic compounds detected in the Murchison meteorite gives an interesting match, which suggests that laboratory simulation of interstellar ice chemistry is relevant to understand astrophysical organic matter evolution.