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Peter Bochsler - One of the best experts on this subject based on the ideXlab platform.
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he Pickup Ions in the inner heliosphere diagnostics of the local interstellar gas and of interplanetary conditIons
9th Annual International Astrophysics Conference on Pickup Ions Throughout the Heliosphere and Beyond: Dedicated to the Memory of Sir W. Ian Axford Ja, 2010Co-Authors: Eberhard Möbius, George Gloeckler, Peter Bochsler, Harald Kucharek, A. B. Galvin, B Klecker, K D C Simunac, L Ellis, C J Farrugia, L M KistlerAbstract:The relative motion of the Sun through the Local Interstellar Cloud (LIC) leads to a neutral wind through the heliosphere. Because of its high ionization potential, He remains neutral to well within 1 AU, where it is deflected by the Sun’s gravity and forms a focusing cone on the downwind side. This flow pattern has been studied with UV backscattering, through Pickup Ions (PUI), and atom imaging. A consolidated set of the physical parameters of He in the LIC has been derived combining all three methods. However, it is still poorly understood why PUI fluxes and velocity distributIons vary substantially on temporal scales from hours to many days, which leads among other phenomena to apparent changes in the appearance of the focusing cone, even after averaging over several days. With the combination of PLASTIC on STEREO A and B as well as SWICS on ACE, simultaneous PUI observatIons over an increasing range of heliospheric longitudes have become possible, for which we have initiated a cross‐calibration effort...
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ENERGETIC NEUTRAL ATOMS: AN ADDITIONAL SOURCE FOR HELIOSPHERIC Pickup Ions
The Astrophysical Journal, 2010Co-Authors: Peter Bochsler, Eberhard MöbiusAbstract:Recently, Schwadron & McComas discussed the possibility of inner source Pickup particles originating from the ionization of energetic neutral atoms (ENAs), based on new data from the IBEX mission. This proposition has some interesting features, namely, it might be able to explain why inner source Pickup Ions (PUIs) have a composition resembling solar abundances and show no indication of overabundance of refractory elements, although this should be expected, if the conventional explanation of solar wind-dust interaction for the origin of this heliospheric component were correct. In this Letter, we explore further consequences for ENA-related PUIs and investigate their velocity distributIons. We conclude that this model will not reproduce the observed velocity distributIons of inner source PUIs and point out a substantial deviation in their composition. However, it seems likely that the ionization of ENAs as observed with IBEX could contribute a significant amount of heliospheric suprathermal tail Ions. Some possible consequences of our investigation for heliospheric particle populatIons are briefly discussed.
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On the Origin of Inner Source Pickup Ions
2010Co-Authors: Peter Bochsler, Eberhard Möbius, Harald Kucharek, Robert F. Wimmer-schweingruberAbstract:Inner source Pickup Ions are thought to originate from the interaction of solar wind Ions with interplanetary dust grains in the inner heliosphere. Processes which produce inner source Pickup Ions, and which have been considered so far are implantation of solar wind on grains and subsequent desorption, charge exchange of solar wind Ions during transit through submicron dust grains, sputtering and backscattering of Ions. A large fraction if not all of the dust crossing the sphere of the Earth’s orbit must end up as Pickup Ions as is evidenced from the comparable order of magnitude of dust flux inward and Pickup ion flux outward at 1 AU. This suggests that the ultimate fate for a large fraction of small interplanetary dust particles after evaporation or sputtering is conversion into Pickup Ions. Sputtering becomes particularly efficient when dust particles—after fragmentation by collisIons with each other—have diminished to sizes comparable to the range of solar wind Ions in dust material. The sputter produ...
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Inner‐Source Pickup Ions as Sensitive Probes to the Inner‐Heliospheric Micro‐State
2010Co-Authors: Robert F. Wimmer-schweingruber, Peter BochslerAbstract:Inner‐source Pickup Ions have been investigated by several workers who all assumed an initial velocity distribution function which is dominated by high velocities in the solar wind velocity frame. This non‐thermal velocity distribution is supposed to be due to the Lorentz force which acts on the freshly ionized particles. However, the location where inner‐source Pickup Ions are ionized lies close to the Sun (probably between 5 and 25 r⊙). The magnetic field and solar wind velocity are near radial there and the Lorentz force acting on freshly created Ions is small. Particles sputtered or ejected with small relative velocities (E
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on pitch angle scattering rates of interstellar Pickup Ions as determined by in situ measurement of velocity distributIons
The Astrophysical Journal, 2007Co-Authors: Philip A. Isenberg, Eberhard Möbius, Lukas Saul, Peter BochslerAbstract:Newly ionized interstellar atoms are acted upon by electromagnetic forces in the solar wind. Measurements of these Pickup Ions enable study of the transport processes controlling the evolution of charged particle populatIons in solar wind plasma. Data from the CELIAS instruments on board the SOHO spacecraft allow measurement of the velocity distribution of singly charged helium Ions. These observatIons are compared to the predictIons of a hemispheric model of pitch-angle diffusion. To justify the use of the hemispheric model we show here that a "resonance gap," which hinders cross-hemispheric scattering of protons by Alfven waves, can exist for the case of Pickup helium scattered by outward-propagating waves. We find that the observed shape of helium Pickup ion velocity distributIons is consistent with the hemispheric model prediction. The parallel mean free path is found to vary with wave power from values of 0.1 to over 1 AU, here presented as a first measurement of the parallel mean free path as a function of magnetic wave power. Magnetic field data from the Wind spacecraft enable comparison to the coincident magnetic field wave power. The cross-hemispheric scattering rate is found to be monotonic and exponentially dependent on wave power over the dynamic range considered.
R F Wimmerschweingruber - One of the best experts on this subject based on the ideXlab platform.
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composition of inner source heavy Pickup Ions at 1 au soho celias ctof observatIons implicatIons for the production mechanisms
Astronomy and Astrophysics, 2015Co-Authors: Adrian Tăut, Clemens Drews, L Berger, R F WimmerschweingruberAbstract: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 su ered 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-TimeOf-Flight sensor on-board the Solar and Heliospheric Observatory. It o ers 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 + , Mg 2+ , 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.
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on the velocity distributIons of dust related inner source Pickup Ions
Geophysical Research Letters, 2006Co-Authors: Eberhard Möbius, Peter Bochsler, R F WimmerschweingruberAbstract:[1] We simulate velocity distributIons for inner-source Pickup Ions in two scenarios for their origin. One scenario creates inner-source Pickup Ions by charge exchange and energy loss in very small (typically submicron-sized) dust grains (Wimmer-Schweingruber and Bochsler 2003), while the other liberates solar wind Ions previously implanted in larger (typically 1 μm) dust grains (Geiss et al. 1995; and Gloeckler and Geiss 1998). The two scenarios differ by the initial velocity with which the Pickup Ions are created; the fine-dust model produces a wide initial velocity distribution, while the coarse-dust model releases them essentially at rest. We investigate the differences in the distributIons once these Ions have been transported out to an observer at 1 AU or beyond.
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on the origin of inner source Pickup Ions
Geophysical Research Letters, 2003Co-Authors: R F Wimmerschweingruber, Peter BochslerAbstract:[1] In situ measurements of Pickup Ions (PUI) exhibit a component that has nearly thermalized with the solar wind. This implies an origin close to the Sun and is generally ascribed to interaction of the solar wind with interplanetary dust particles (IDPs). We propose a scenario for the origin of inner-source PUIs in which a population of very small IDPs serves as the neutralizing agent for solar wind Ions. The size of these IDPs is less than or comparable to the penetration range, of solar wind Ions in IDP material. The interaction of the solar wind with such particles results in a net charge exchange in which solar wind Ions exit the IDPs as predominantly neutral or singly-charged Ions. When the neutralized solar wind is reionized, it is picked up and can then be measured as a PUI.
George Gloeckler - One of the best experts on this subject based on the ideXlab platform.
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he Pickup Ions in the inner heliosphere diagnostics of the local interstellar gas and of interplanetary conditIons
9th Annual International Astrophysics Conference on Pickup Ions Throughout the Heliosphere and Beyond: Dedicated to the Memory of Sir W. Ian Axford Ja, 2010Co-Authors: Eberhard Möbius, George Gloeckler, Peter Bochsler, Harald Kucharek, A. B. Galvin, B Klecker, K D C Simunac, L Ellis, C J Farrugia, L M KistlerAbstract:The relative motion of the Sun through the Local Interstellar Cloud (LIC) leads to a neutral wind through the heliosphere. Because of its high ionization potential, He remains neutral to well within 1 AU, where it is deflected by the Sun’s gravity and forms a focusing cone on the downwind side. This flow pattern has been studied with UV backscattering, through Pickup Ions (PUI), and atom imaging. A consolidated set of the physical parameters of He in the LIC has been derived combining all three methods. However, it is still poorly understood why PUI fluxes and velocity distributIons vary substantially on temporal scales from hours to many days, which leads among other phenomena to apparent changes in the appearance of the focusing cone, even after averaging over several days. With the combination of PLASTIC on STEREO A and B as well as SWICS on ACE, simultaneous PUI observatIons over an increasing range of heliospheric longitudes have become possible, for which we have initiated a cross‐calibration effort...
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The inner source for Pickup Ions
AIP Conference Proceedings, 2008Co-Authors: Nathan A. Schwadron, Johanna Geiß, Lee Ann Fisk, George Gloeckler, Thomas H. ZurbuchenAbstract:Pickup Ions are observed by the Solar Wind Ion Composition Spectrometer on Ulysses which appear to have been picked up close to the Sun. A transport theory for the propagation of these Ions is used to constrain the spatial profiles of the ion sources. The composition is like that of the solar wind which suggests that the inner source Pickup Ions result from solar wind particles that are embedded in dust grains and then released. Through comparison between modeled and observed distributIons, it is possible to constrain the radial and latitudinal profiles of the inner source. Inner source protons are also observed and may constitute an energetically important population in the solar wind.
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acceleration of Pickup Ions at quasi stationary shocks
TURBULENCE AND NONLINEAR PROCESSES IN ASTROPHYSICAL PLASMAS: 6th Annual International Astrophysics Conference, 2007Co-Authors: George Gloeckler, Lee Ann FiskAbstract:ObservatIons of omnipresent suprathermal power law tails, with the unique spectral index of −5, on the velocity distributIons of solar wind and Pickup Ions raise important questIons and have far reaching consequences. The obvious question of how these tails are formed during quiet times, when no shocks are present, was previously addressed and is briefly reviewed here. One of the consequences of the existence of ubiquitous quiet time tails is that sufficiently energetic particles are always readily available for further acceleration by shocks. It is this aspect that is examined in this paper. We present observatIons showing that downstream of two quasi‐stationary shocks the −5 spectral power law spectra are preserved and that the increase in tail pressure jump can be obtained by applying thermodynamic constraints on non‐adiabatic heating of upstream particles by the shock.
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Pickup Ions and Cosmic Rays from Dust in the Heliosphere
Space Science Reviews, 2007Co-Authors: Nathan A. Schwadron, George GloecklerAbstract:The combination of recent observational and theoretical work has completed the catalog of the sources of heliospheric Pickup Ions (PUIs). These PUIs are the seed population for Anomalous Cosmic Rays (ACRs), which are accelerated to high energies at or beyond the Termination Shock (TS). For elements with high First Ionization Potentials (high-FIP atoms: e.g., H, He, Ne, etc.), the dominant source of PUIs and ACRs is from neutral atoms that drift into the heliosphere from the Local Interstellar Medium (LISM) and, prior to ionization, are influenced primarily by solar gravitation and radiation pressure (for H). After ionization, these interstellar Ions are Pickup up by the solar wind, swept out, and are either accelerated near the TS or beyond it. Elements with low first ionization potentials (low-FIP atoms: e.g., C, Si, Mg, Fe, etc.) are also observed as PUIs by Ulysses and as ACRs by Wind and Voyager. But the low-FIP composition of this additional component reveals a very different origin. Low-FIP interstellar atoms are predominantly ionized in the LISM and therefore excluded from the heliosphere by the solar wind. Remarkably, a low-FIP component of PUIs was hypothesized by Banks (J. Geophys. Res. 76, 4341, 1971) over twenty years prior to its direct detection by Ulysses/SWICS (Geiss et al., J. Geophys. Res. 100(23), 373, 1995) The leading concept for the generation of Inner Source PUIs involves an effective recycling of solar wind on grains near the Sun, as originally suggested by Banks. Voyager and Wind also observe low-FIP ACRs, and a grain-related source appears likely and necessary. Two concepts have been proposed to explain these low-FIP ACRs: the first concept involves the acceleration of the Inner Source of PUIs, and the second involves a so-called Outer Source of PUIs generated from solar wind interaction with the large population of grains in the Kuiper Belt. We review here the observational and theoretical work over the last decade that shows how solar wind and heliospheric grains interact to produce Pickup Ions, and, in turn, anomalous cosmic rays. The inner and outer sources of Pickup Ions and anomalous cosmic rays exemplify dusty plasma interactIons that are fundamental throughout the cosmos for the production of energetic particles and the formation of stellar systems.
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acceleration of solar wind and Pickup Ions by shocks
Solar Wind 11 SOHO 16 Connecting Sun and Heliosphere, 2005Co-Authors: George Gloeckler, Lee Ann Fisk, L J LanzerottiAbstract:Distribution functIons of H + , He ++ and He + up- and downstream of shocks are examined to learn about the acceleration of solar wind and Pickup Ions by various types of shocks. We combine data from the SWICS and HISCALE instruments on Ulysses to obtain continuous spectra over the wide energy range from ~0.6 keV to almost 5 MeV for our detailed study of two different types of shock crossings, a reverse shock of a Corotating Interaction Region (CIR) and Jupiter's bow shock. Ion velocity distributIons have suprathermal tails extending to MeV energies upstream of and far removed from shocks. Downstream distributIons have spectral shapes similar to those upstream but higher particle densities in the tails. Injection/acceleration efficiencies show the strongest correlation with the shock compression ratio. Applying observatIons made from ~1.6 to 5.4 AU to the heliospheric termination shock we find that simply heating the upstream Pickup and solar wind distributIons provides excellent fits to the measured ion spectra and is consistent with all other available observatIons by Voyager 1.
Robert F. Wimmer-schweingruber - One of the best experts on this subject based on the ideXlab platform.
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Composition of inner-source heavy Pickup Ions at 1 AU: SOHO/CELIAS/CTOF observatIons ImplicatIons for the production mechanisms
Astronomy and Astrophysics, 2015Co-Authors: Adrian Tăut, Clemens Drews, L Berger, Robert F. Wimmer-schweingruberAbstract: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 su ered 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-TimeOf-Flight sensor on-board the Solar and Heliospheric Observatory. It o ers 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 + , Mg 2+ , 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.
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On the Origin of Inner Source Pickup Ions
2010Co-Authors: Peter Bochsler, Eberhard Möbius, Harald Kucharek, Robert F. Wimmer-schweingruberAbstract:Inner source Pickup Ions are thought to originate from the interaction of solar wind Ions with interplanetary dust grains in the inner heliosphere. Processes which produce inner source Pickup Ions, and which have been considered so far are implantation of solar wind on grains and subsequent desorption, charge exchange of solar wind Ions during transit through submicron dust grains, sputtering and backscattering of Ions. A large fraction if not all of the dust crossing the sphere of the Earth’s orbit must end up as Pickup Ions as is evidenced from the comparable order of magnitude of dust flux inward and Pickup ion flux outward at 1 AU. This suggests that the ultimate fate for a large fraction of small interplanetary dust particles after evaporation or sputtering is conversion into Pickup Ions. Sputtering becomes particularly efficient when dust particles—after fragmentation by collisIons with each other—have diminished to sizes comparable to the range of solar wind Ions in dust material. The sputter produ...
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Inner‐Source Pickup Ions as Sensitive Probes to the Inner‐Heliospheric Micro‐State
2010Co-Authors: Robert F. Wimmer-schweingruber, Peter BochslerAbstract:Inner‐source Pickup Ions have been investigated by several workers who all assumed an initial velocity distribution function which is dominated by high velocities in the solar wind velocity frame. This non‐thermal velocity distribution is supposed to be due to the Lorentz force which acts on the freshly ionized particles. However, the location where inner‐source Pickup Ions are ionized lies close to the Sun (probably between 5 and 25 r⊙). The magnetic field and solar wind velocity are near radial there and the Lorentz force acting on freshly created Ions is small. Particles sputtered or ejected with small relative velocities (E
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On the velocity distributIons of dust‐related inner‐source Pickup Ions
Geophysical Research Letters, 2006Co-Authors: Peter Bochsler, Eberhard Möbius, Robert F. Wimmer-schweingruberAbstract:[1] We simulate velocity distributIons for inner-source Pickup Ions in two scenarios for their origin. One scenario creates inner-source Pickup Ions by charge exchange and energy loss in very small (typically submicron-sized) dust grains (Wimmer-Schweingruber and Bochsler 2003), while the other liberates solar wind Ions previously implanted in larger (typically 1 μm) dust grains (Geiss et al. 1995; and Gloeckler and Geiss 1998). The two scenarios differ by the initial velocity with which the Pickup Ions are created; the fine-dust model produces a wide initial velocity distribution, while the coarse-dust model releases them essentially at rest. We investigate the differences in the distributIons once these Ions have been transported out to an observer at 1 AU or beyond.
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On the origin of inner‐source Pickup Ions
Geophysical Research Letters, 2003Co-Authors: Robert F. Wimmer-schweingruber, Peter BochslerAbstract:[1] In situ measurements of Pickup Ions (PUI) exhibit a component that has nearly thermalized with the solar wind. This implies an origin close to the Sun and is generally ascribed to interaction of the solar wind with interplanetary dust particles (IDPs). We propose a scenario for the origin of inner-source PUIs in which a population of very small IDPs serves as the neutralizing agent for solar wind Ions. The size of these IDPs is less than or comparable to the penetration range, of solar wind Ions in IDP material. The interaction of the solar wind with such particles results in a net charge exchange in which solar wind Ions exit the IDPs as predominantly neutral or singly-charged Ions. When the neutralized solar wind is reionized, it is picked up and can then be measured as a PUI.
Johanna Geiß - One of the best experts on this subject based on the ideXlab platform.
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The inner source for Pickup Ions
AIP Conference Proceedings, 2008Co-Authors: Nathan A. Schwadron, Johanna Geiß, Lee Ann Fisk, George Gloeckler, Thomas H. ZurbuchenAbstract:Pickup Ions are observed by the Solar Wind Ion Composition Spectrometer on Ulysses which appear to have been picked up close to the Sun. A transport theory for the propagation of these Ions is used to constrain the spatial profiles of the ion sources. The composition is like that of the solar wind which suggests that the inner source Pickup Ions result from solar wind particles that are embedded in dust grains and then released. Through comparison between modeled and observed distributIons, it is possible to constrain the radial and latitudinal profiles of the inner source. Inner source protons are also observed and may constitute an energetically important population in the solar wind.
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stability of the inner source Pickup Ions over the solar cycle
Journal of Geophysical Research, 2005Co-Authors: F Allegrini, David J. Mccomas, Nathan A. Schwadron, George Gloeckler, Johanna GeißAbstract:[1] Inner source Pickup Ions (PUIs) were discovered and are observed by Ulysses. They are thought to be generated by solar wind interaction with dust grains near the Sun. From previous work, four constraints were derived on inner source PUIs from observatIons near solar minimum: (1) the composition resembles the solar wind; (2) the distribution functIons show strong adiabatic cooling, consistent with a source peaked near 10-30 R S ; (3) the production rates of inner source C + and O + are about 2 x 10 6 g/s each; (4) the individual inner source counts are randomly distributed in time. We compare inner source observatIons over three distinct 2-month periods in 1994, 1995, and 2001, when Ulysses was at high latitudes and about 2 AU from the Sun. Our observatIons not only substantiate the four constraints above but, in addition, reveal that the inner source appears stable over at least half a solar cycle and the inner source PUI flux is correlated with solar wind flux. A number of scenarios have been proposed to explain the origin of the inner source PUI. None of the proposed inner sources are consistent with our five observational constraints, suggesting that we do not yet understand the true source of these Pickup Ions.
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elemental composition of the inner source Pickup Ions
Journal of Geophysical Research, 2000Co-Authors: George Gloeckler, Johanna Geiß, Lee Ann Fisk, Nathan A. Schwadron, Thomas H. ZurbuchenAbstract:ObservatIons of the composition of inner source Pickup Ions in the solar wind, from the Solar Wind Ion Composition Spectrometer on Ulysses, are presented. The composition is similar to that of the solar wind and, in particular, contains volatile elements such as neon. These observatIons suggest strongly, and perhaps conclusively, that inner source Pickup Ions result from solar wind particles that are embedded in dust grains and then released. Our observatIons also suggest that inner source Pickup Ions may be an important source for particles accelerated at shocks surrounding corotating interaction regIons since the resulting composition will resemble that of the solar wind, as is observed. Mechanisms are described whereby inner source Pickup Ions can be preferentially injected into the shock acceleration mechanism.
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Interstellar and Inner Source Pickup Ions Observed with Swics on Ulysses
Space Science Reviews, 1998Co-Authors: George Gloeckler, Johanna GeißAbstract:Many species of Pickup Ions, both of interstellar origin and from an inner, distributed source have been discovered using data from the Solar Wind Ion Composition Spectrometer (SWICS) on Ulysses. Velocity distribution functIons of these Ions were measured for the first time over heliocentric distances between 1.35 and 5.4 AU, both at high and low latitudes, and in the disturbed slow solar wind as well as the steady fast wind of the polar coronal holes. This has given us the first glance at plasma properties of suprathermal Ions in various solar wind flows, and is enabling us to study the chemical and, in the case of He, the isotopic composition of the local interstellar cloud. Among the new findings are (a) the surprisingly weak pitch-angle scattering of low rigidity, suprathermal Ions leading to strongly anisotropic velocity distributIons in radial magnetic fields, (b) the efficient injection and consequent acceleration of Pickup Ions, especially He+ and H+, in the turbulent solar wind, and (c) the discovery of a new extended source releasing carbon, oxygen, nitrogen and possibly other atoms and molecules in the inner solar system. Pickup ion measurements are now used to study the characteristics of the local interstellar cloud (LIC) and, in particular, to determine accurately the abundance of atomic H, He, N, O, and Ne, the isotopes of He and Ne, as well as the ionization fractIons of H and He in the LIC. Pickup ion observatIons allow us to infer the location of the termination shock and, in combination with measurements of anomalous cosmic rays, to investigate termination shock acceleration mechanisms.
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C+ Pickup Ions in the heliosphere and their origin
Journal of Geophysical Research, 1995Co-Authors: Johanna Geiß, Lee Ann Fisk, George Gloeckler, R. Von SteigerAbstract:C + Pickup Ions were discovered with the solar wind ion composition spectrometer flying on Ulysses. Whereas the other nonlocally occurring Pickup Ions are produced from the interstellar gas penetrating deep into the heliosphere, C + comes from an inner source which is located at a solar distance of a few AU and extends over all heliospheric latitudes investigated so far. The total production of C + , N + , and O + by this inner source is of the order of 10 −3 relative to the total production of O + from the interstellar gas in the heliosphere. Thus the inner source does not significantly contribute to oxygen or nitrogen in the anomalous cosmic rays (ACR), but its contribution to ACR carbon may not be negligible. We propose that the inner source material is carbon compounds evaporating from grains. At this time, the evidence points to interstellar grains as the major source, but we do not want to exclude yet a contribution from grains of solar system origin.