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1.
Pickup ions, created by ionization of slow moving atoms and molecules well inside the heliosphere, provide us with a new tool
to probe remote regions in and beyond the heliosphere and to study injection and acceleration processes in the solar wind.
Comprehensive and continuous measurements of H, He, C, N, O, Ne and other pickup ions, especially with the Solar Wind Ion
Composition Spectrometer (SWICS) on both Ulysses and ACE, have given us a wealth of data that have been used to infer chemical and physical properties of the local interstellar
cloud. With SWICS on Ulysses we discovered a new population of pickup ions, produced from atomic and molecular sources deep inside the heliosphere. The
velocity distributions and composition of these “inner source” pickup ions are distinctly different from those of interstellar
pickup ions, showing effects of strong adiabatic cooling, and a composition resembling that of the solar wind. Strong cooling
indicates that the source of these pickup ions lies close to the Sun. The similarity of composition of inner source heavy
ions to that of the solar wind implies that the dominant production mechanism for these pickup ions involves the absorption
and re-emission of solar wind from interplanetary dust grains. While interstellar pickup ions are the seed population of the
main Anomalous Cosmic Rays (ACRs), inner source pickup ions may be an important source of the rarer ACRs such as C, Mg, Si,
S, and Fe. We present new results and review previous work with an emphasis on characteristics of the local interstellar cloud
and properties of the inner source.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
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.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
3.
G. Gloeckler H. Balsiger A. Bürgi P. Bochsler L. A. Fisk A. B. Galvin J. Geiss F. Gliem D. C. Hamilton T. E. Holzer D. Hovestadt F. M. Ipavich E. Kirsch R. A. Lundgren K. W. Ogilvie R. B. Sheldon B. Wilken 《Space Science Reviews》1995,71(1-4):79-124
The Solar Wind and Suprathermal Ion Composition Experiment (SMS) on WIND is designed to determine uniquely the elemental, isotopic, and ionic-charge composition of the solar wind, the temperatures and mean speeds of all major solar-wind ions, from H through Fe, at solar wind speeds ranging from 175 kms–1 (protons) to 1280 kms–1 (Fe+8), and the composition, charge states as well as the 3-dimensional distribution functions of suprathermal ions, including interstellar pick-up He+, of energies up to 230 keV/e. The experiment consists of three instruments with a common Data Processing Unit. Each of the three instruments uses electrostatic analysis followed by a time-of-flight and, as required, an energy measurement. The observations made by SMS will make valuable contributions to the ISTP objectives by providing information regarding the composition and energy distribution of matter entering the magnetosphere. In addition SMS results will have an impact on many areas of solar and heliospheric physics, in particular providing important and unique information on: (i) conditions and processes in the region of the corona where the solar wind is accelerated; (ii) the location of the source regions of the solar wind in the corona; (iii) coronal heating processes; (iv) the extent and causes of variations in the composition of the solar atmosphere; (v) plasma processes in the solar wind; (vi) the acceleration of particles in the solar wind; and (vii) the physics of the pick-up process of interstellar He as well as lunar particles in the solar wind, and the isotopic composition of interstellar helium. 相似文献
4.
Johannes Geiss is a world leader and foremost expert on measurements and interpretation of the composition of matter that
reveals the history, present state, and future of astronomical objects. With his Swiss team he was first to measure the composition
of the noble gases in the solar wind when in the late 1960s he flew the brilliant solar wind collecting foil experiments on
the five Apollo missions to the moon. Always at the forefront of the art of composition measurements, he with his colleagues
determined the isotopic and elemental composition of the solar wind using instruments characterized by innovative design that
have provided the most comprehensive record of the solar wind composition under all solar wind conditions at all helio-latitudes.
He discovered heavy interstellar pickup ions, from which the composition of the neutral gas of the Local Interstellar Cloud
is determined, and the “Inner Source” of pickup ions. Johannes Geiss played a key role both in the in-situ measurements and
modeling of molecular ions in comets, and the interpretation of these data. He and co-workers measured the composition of
plasmas in the magnetospheres of Earth and Jupiter. Here we highlight Johannes Geiss’ many discoveries and seminal contributions
to our knowledge of the composition of matter of the Sun, solar wind, interstellar gas, early universe, comets and magnetospheres. 相似文献
5.
Möbius E. Kistler L.M. Popecki M.A. Crocker K.N. Granoff M. Turco S. Anderson A. Demain P. Distelbrink J. Dors I. Dunphy P. Ellis S. Gaidos J. Googins J. Hayes R. Humphrey G. Kästle H. Lavasseur J. Lund E.J. Miller R. Sartori E. Shappirio M. Taylor S. Vachon P. Vosbury M. Ye V. Hovestadt D. Klecker B. Arbinger H. Künneth E. Pfeffermann E. Seidenschwang E. Gliem F. Reiche K.-U. Stöckner K. Wiewesiek W. Harasim A. Schimpfle J. Battell S. Cravens J. Murphy G. 《Space Science Reviews》1998,86(1-4):449-495
The Solar Energetic Particle Ionic Charge Analyzer (SEPICA) is the main instrument on the Advanced Composition Explorer (ACE)
to determine the ionic charge states of solar and interplanetary energetic particles in the energy range from ≈0.2 MeV nucl−1
to ≈5 MeV charge−1. The charge state of energetic ions contains key information to unravel source temperatures, acceleration,
fractionation and transport processes for these particle populations. SEPICA will have the ability to resolve individual charge
states and have a substantially larger geometric factor than its predecessor ULEZEQ on ISEE-1 and -3, on which SEPICA is based.
To achieve these two requirements at the same time, SEPICA is composed of one high-charge resolution sensor section and two
low- charge resolution, but large geometric factor sections. The charge resolution is achieved by the focusing of the incoming
ions, through a multi-slit mechanical collimator, deflection in an electrostatic analyzer with a voltage up to 30 kV, and
measurement of the impact position in the detector system. To determine the nuclear charge (element) and energy of the incoming
ions, the combination of thin-window flow-through proportional counters with isobutane as counter gas and ion-implanted solid
state detectors provide for 3 independent ΔE (energy loss) versus E (residual energy) telescopes. The multi-wire proportional
counter simultaneously determines the energy loss ΔE and the impact position of the ions. Suppression of background from penetrating
cosmic radiation is provided by an anti-coincidence system with a CsI scintillator and Si-photodiodes. The data are compressed
and formatted in a data processing unit (S3DPU) that also handles the commanding and various automatted functions of the instrument.
The S3DPU is shared with the Solar Wind Ion Charge Spectrometer (SWICS) and the Solar Wind Ion Mass Spectrometer (SWIMS) and
thus provides the same services for three of the ACE instruments. It has evolved out of a long family of data processing units
for particle spectrometers.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
6.
The abundance of 3He in the present day local interstellar cloud (LIC) and in the sun has important implications for the study of galactic evolution and for estimating the production of light nuclei in the early universe. Data from the Solar Wind Ion Composition Spectrometer (SWICS) on Ulysses is used to measure the isotopic ratio of helium (3He/4He = ) both in the solar wind and the local interstellar cloud. For the solar wind, the unique high-latitude orbit of Ulysses allows us to study this ratio in the slow and highly dynamic wind in the ecliptic plane as well as the steady high-latitude wind of the polar coronal holes. The 3He+/4He+ ratio in the local cloud is derived from the isotopic ratio of pickup helium measured in the high-speed solar wind. In the LIC the ratio is found to be (2.48
-0.62
+0.68
) × 10-4 with the 1- uncertainty resulting almost entirely from statistical error. In the solar wind, is determined with great statistical accuracy but shows systematic differences between fast and slow solar wind streams. The slow wind ratio is variable. Its weighted average value (4.08 ± 0.25) × 10-4 is, within uncertainties, in agreement with the Apollo SWC results. The high wind ratio is less variable but smaller. The average in the fast wind is (3.3 ± 0.3) × 10-4. 相似文献
7.
Daniel B. Reisenfeld Roger C. Wiens Bruce L. Barraclough John T. Steinberg Marcia Neugebauer Jim Raines Thomas H. Zurbuchen 《Space Science Reviews》2013,175(1-4):125-164
We describe the Genesis mission solar-wind sample collection period and the solar wind conditions at the L1 point during this 2.3-year period. In order to relate the solar wind samples to solar composition, the conditions under which the samples were collected must be understood in the context of the long-term solar wind. We find that the state of the solar wind was typical of conditions over the past four solar cycles. However, Genesis spent a relatively large fraction of the time in coronal-hole flow as compared to what might have been expected for the declining phase of the solar cycle. Data from the Solar Wind Ion Composition Spectrometer (SWICS) on the Advanced Composition Explorer (ACE) are used to determine the effectiveness of the Genesis solar-wind regime selection algorithm. The data collected by SWICS confirm that the Genesis algorithm successfully separated and collected solar wind regimes having distinct solar origins, particularly in the case of the coronal hole sample. The SWICS data also demonstrate that the different regimes are elementally fractionated. When compared with Ulysses composition data from the previous solar cycle, we find a similar degree of fractionation between regimes as well as fractionation relative to the average photospheric composition. The Genesis solar wind samples are under long-term curation at NASA Johnson Space Center so that as sample analysis techniques evolve, pristine solar wind samples will be available to the scientific community in the decades to come. This article and a companion paper (Wiens et al. 2013, this issue) provide post-flight information necessary for the analysis of the Genesis array and foil solar wind samples and the Genesis solar wind ion concentrator samples, and thus serve to complement the Space Science Review volume, The Genesis Mission (v. 105, 2003). 相似文献
8.
The solar wind charge state and elemental compositions have been measured with the Solar Wind Ion Composition Spectrometers
(SWICS) on Ulysses and ACE for a combined period of about 25 years. This most extensive data set includes all varieties of
solar wind flows and extends over more than one solar cycle. With SWICS the abundances of all charge states of He, C, N, O,
Ne, Mg, Si, S, Ar and Fe can be reliably determined (when averaged over sufficiently long time periods) under any solar wind
flow conditions. Here we report on results of our detailed analysis of the elemental composition and ionization states of
the most unbiased solar wind from the polar coronal holes during solar minimum in 1994–1996, which includes new values for
the abundance S, Ca and Ar and a more accurate determination of the 20Ne abundance. We find that in the solar minimum polar coronal hole solar wind the average freezing-in temperature is ∼1.1×106 K, increasing slightly with the mass of the ion. Using an extrapolation method we derive photospheric abundances from solar
wind composition measurements. We suggest that our solar-wind-derived values should be used for the photospheric ratios of
Ne/Fe=1.26±0.28 and Ar/Fe=0.030±0.007. 相似文献
9.
George Gloeckler 《Space Science Reviews》1996,78(1-2):335-346
Pickup ions measured deep inside the heliosphere open a new way to determine the absolute atomic density of a number of elements and isotopes in the local interstellar cloud (LIC). We derive the atomic abundance of hydrogen and the two isotopes of helium from the velocity and spatial distributions of interstellar pickup protons and ionized helium measured with the Solar Wind Ion Composition Spectrometer (SWICS) on the Ulysses spacecraft between 2 and 5 AU. The atomic hydrogen density near the termination shock derived from interstellar pickup ion measurements is 0.115±0.025 cm–3 and the atomic H/He ratio from these observations is found to be 7.7 ± 1.3 in the outer heliosphere. Comparing this value with the standard universal H/He ratio of 10 we conclude that filtration of hydrogen is small and that the ionization fraction of hydrogen in the LIC is low. 相似文献
10.
The mass spectrometric determinations of the isotopic composition of helium in the solar wind obtained from (1) the Apollo Solar Wind Composition (SWC) experiment, (2) the Ion Composition Instrument (ICI) on the International Sun Earth Explorer 3 (ISEE-3), and (3) the Solar Wind Composition Spectrometer (SWICS) on Ulysses are reviewed and discussed, including new data given by Gloeckler and Geiss (1998). Averages of the 3He/4He ratio in the slow wind and in fast streams are given. Taking account of separation and fractionation processes in the corona and chromosphere, 3He/4He = (3.8 ± 0.5) × 10-4 is derived as the best estimate for the present-day Outer Convective Zone (OCZ) of the sun. After corrections of this ratio for secular changes caused by diffusion, mixing and 3He production by incomplete H-burning (Vauclair, 1998), we obtain (D + 3He)/H = (3.6±0.5) × 10-5 for the Protosolar Cloud (PSC). Adopting 3He/H = (1.5±0.2) × 10-5 for the PSC, as is indicated from the 3He/4He ratio in the planetary gas component of meteorites and in Jupiter (Mahaffy et al., 1998), we obtain (D/H)protosolar = (2.1 ± 0.5) × 10-5. Galactic evolution studies (Tosi, 1998) show that the measured D and 3He abundances in the Protosolar Cloud and the Local Interstellar Cloud (Linsky, 1998; Gloeckler and Geiss, 1998), lead to (D/H)primordial = (2 - 5) × 10-5. This range corresponds to a universal baryon/photon ratio of (6.0 ± 0.8) × 10-10, and to b = 0.075 ± 0.015. 相似文献
11.
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. 相似文献
12.
V. V. Izmodenov 《Space Science Reviews》2007,130(1-4):377-387
Interstellar atoms penetrate deep into the heliosphere after passing through the heliospheric interface—the region of the
interaction of the solar wind with the interstellar medium. The heliospheric interface serves as a filter for the interstellar
atoms of hydrogen and oxygen, and, to a lesser extent, nitrogen, due to their coupling with interstellar and heliospheric
plasmas by charge exchange and electron impact ionization. The filtration has great importance for the determination of local
interstellar abundances of these elements, which becomes now possible due to measurements of interstellar pickup by Ulysses
and ACE, and anomalous cosmic rays by Voyagers, Ulysses, ACE, SAMPEX and Wind. The filtration of the different elements depends
on the level of their coupling with the plasma in the interaction region. The recent studies of the filtration of the interstellar
atoms in the heliospheric interface region is reviewed in this paper. The dependence of the filtration on the local interstellar
proton and H atom number densities is discussed and the roles of the charge exchange and electron impact ionization on the
filtration are evaluated. The influence of electron temperature in the inner heliosheath on the filtration process is discussed
as well. Using the filtration coefficients obtained from the modeling and SWICS/Ulysses pickup ion measurements, the local
interstellar abundances of the considered elements are determined. 相似文献
13.
A. Grimberg D. S. Burnett P. Bochsler H. Baur R. Wieler 《Space Science Reviews》2007,130(1-4):293-300
We discuss data of light noble gases from the solar wind implanted into a metallic glass target flown on the Genesis mission.
Helium and neon isotopic compositions of the bulk solar wind trapped in this target during 887 days of exposure to the solar
wind do not deviate significantly from the values in foils of the Apollo Solar Wind Composition experiments, which have been
exposed for hours to days. In general, the depth profile of the Ne isotopic composition is similar to those often found in
lunar soils, and essentially very well reproduced by ion-implantation modelling, adopting the measured velocity distribution
of solar particles during the Genesis exposure and assuming a uniform isotopic composition of solar wind neon. The results
confirm that contributions from high-energy particles to the solar wind fluence are negligible, which is consistent with in-situ
observations. This makes the enigmatic “SEP-Ne” component, apparently present in lunar grains at relatively large depth, obsolete.
20Ne/ 22Ne ratios in gas trapped very near the metallic glass surface are up to 10% higher than predicted by ion implantation simulations.
We attribute this superficially trapped gas to very low-speed, current-sheet-related solar wind, which has been fractionated
in the corona due to inefficient Coulomb drag. 相似文献
14.
Stone E.C. Cohen C.M.S. Cook W.R. Cummings A.C. Gauld B. Kecman B. Leske R.A. Mewaldt R.A. Thayer M.R. Dougherty B.L. Grumm R.L. Milliken B.D. Radocinski R.G. Wiedenbeck M.E. Christian E.R. Shuman S. von Rosenvinge T.T. 《Space Science Reviews》1998,86(1-4):357-408
The Solar Isotope Spectrometer (SIS), one of nine instruments on the Advanced Composition Explorer (ACE), is designed to provide
high- resolution measurements of the isotopic composition of energetic nuclei from He to Zn (Z=2 to 30) over the energy range
from ∼10 to ∼100 MeV nucl−1. During large solar events SIS will measure the isotopic abundances of solar energetic particles
to determine directly the composition of the solar corona and to study particle acceleration processes. During solar quiet
times SIS will measure the isotopes of low-energy cosmic rays from the Galaxy and isotopes of the anomalous cosmic-ray component,
which originates in the nearby interstellar medium. SIS has two telescopes composed of silicon solid-state detectors that
provide measurements of the nuclear charge, mass, and kinetic energy of incident nuclei. Within each telescope, particle trajectories
are measured with a pair of two-dimensional silicon-strip detectors instrumented with custom, very large-scale integrated
(VLSI) electronics to provide both position and energy-loss measurements. SIS was especially designed to achieve excellent
mass resolution under the extreme, high flux conditions encountered in large solar particle events. It provides a geometry
factor of ∼40 cm2 sr, significantly greater than earlier solar particle isotope spectrometers. A microprocessor controls the
instrument operation, sorts events into prioritized buffers on the basis of their charge, range, angle of incidence, and quality
of trajectory determination, and formats data for readout by the spacecraft. This paper describes the design and operation
of SIS and the scientific objectives that the instrument will address.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
15.
Mason G.M. Gold R.E. Krimigis S.M. Mazur J.E. Andrews G.B. Daley K.A. Dwyer J.R. Heuerman K.F. James T.L. Kennedy M.J. LeFevere T. Malcolm H. Tossman B. Walpole P.H. 《Space Science Reviews》1998,86(1-4):409-448
The Ultra Low Energy Isotope Spectrometer (ULEIS) on the ACE spacecraft is an ultra high resolution mass spectrometer designed
to measure particle composition and energy spectra of elements He-Ni with energies from ∼45 keV nucl−1 to a few MeV nucl−1.
ULEIS will investigate particles accelerated in solar energetic particle events, interplanetary shocks, and at the solar wind
termination shock. By determining energy spectra, mass composition, and their temporal variations in conjunction with other
ACE instruments, ULEIS will greatly improve our knowledge of solar abundances, as well as other reservoirs such as the local
interstellar medium. ULEIS is designed to combine the high sensitivity required to measure low particle fluxes, along with
the capability to operate in the largest solar particle or interplanetary shock events. In addition to detailed information
for individual ions, ULEIS features a wide range of count rates for different ions and energies that will allow accurate determination
of particle fluxes and anisotropies over short (∼few minutes) time scales.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
16.
R. A. Leske R. A. Mewaldt C. M. S. Cohen A. C. Cummings E. C. Stone M. E. Wiedenbeck T. T. von Rosenvinge 《Space Science Reviews》2007,130(1-4):195-205
Solar energetic particles (SEPs) provide a sample of the Sun from which solar composition may be determined. Using high-resolution
measurements from the Solar Isotope Spectrometer (SIS) onboard NASA’s Advanced Composition Explorer (ACE) spacecraft, we have
studied the isotopic composition of SEPs at energies ≥20 MeV/nucleon in large SEP events. We present SEP isotope measurements
of C, O, Ne, Mg, Si, S, Ar, Ca, Fe, and Ni made in 49 large events from late 1997 to the present. The isotopic composition
is highly variable from one SEP event to another due to variations in seed particle composition or due to mass fractionation
that occurs during the acceleration and/or transport of these particles. We show that various isotopic and elemental enhancements
are correlated with each other, discuss the empirical corrections used to account for the compositional variability, and obtain
estimated solar isotopic abundances. We compare the solar values and their uncertainties inferred from SEPs with solar wind
and other solar system abundances and find generally good agreement. 相似文献
17.
R. Bodmer P. Bochsler J. Geiss R. von Steiger G. Gloeckler 《Space Science Reviews》1995,72(1-2):61-64
This is the first study of the isotopic composition of solar wind helium with the SWICS time-of flight mass spectrometer. Although the design of SWICS is not optimized to measure3He abundances precisely,4He/3He flux ratios can be deduced from the data. The long term ratio is 2290±200, which agrees with the results obtained with the ICI magnetic mass spectrometer on ISEE-3 and with the Apollo SWC foil experiments.The ULYSSES spacecraft follows a trajectory which is ideal for the study of different solar wind types. During one year, from mid-1992 to mid-1993, it was in a range of heliographic latitudes where a recurrent fast stream from the southern polar coronal hole was observed every solar rotation. Solar wind bulk velocities ranged from 350 km/s to 950 km/s which would, in principle allow us to identify velocity-correlated compositional variations. Our investigation of solar wind helium, however, shows an isotopic ratio which does not depend on the solar wind speed. 相似文献
18.
Christopher T. Russell 《Space Science Reviews》1975,17(2-4):435-447
The Third Solar Wind Conference was convened from March 25 to 29,1974 at the Asilomar Conference Grounds, Pacific Grove, California. The conference consisted of nine sessions dealing with solar abundances; the history and evolution of the solar wind; the structure and dynamics of the solar wind; the structure and dynamics of the solar corona; macroscopic and microscopic properties of the solar wind; cosmic rays as a probe of the solar wind; spatial gradients; stellar winds; and interactions with objects in the solar wind. This paper summarizes the invited and contributed talks presented at the conference.Institute of Geophysics and Planetary Physics Publication Number 1354-51. 相似文献
19.
The solar wind evolves as it moves outward due to interactions with both itself and with the circum-heliospheric interstellar medium. The speed is, on average, constant out to 30 AU, then starts a slow decrease due to the pickup of interstellar neutrals. These neutrals reduce the solar wind speed by about 20% before the termination shock (TS). The pickup ions heat the thermal plasma so that the solar wind temperature increases outside 20–30 AU. Solar cycle effects are important; the solar wind pressure changes by a factor of 2 over a solar cycle and the structure of the solar wind is modified by interplanetary coronal mass ejections (ICMEs) near solar maximum. The first direct evidences of the TS were the observations of streaming energetic particles by both Voyagers 1 and 2 beginning about 2 years before their respective TS crossings. The second evidence was a slowdown in solar wind speed commencing 80 days before Voyager 2 crossed the TS. The TS was a weak, quasi-perpendicular shock which transferred the solar wind flow energy mainly to the pickup ions. The heliosheath has large fluctuations in the plasma and magnetic field on time scales of minutes to days. 相似文献
20.
Burnett D.S. Barraclough B.L. Bennett R. Neugebauer M. Oldham L.P. Sasaki C.N. Sevilla D. Smith N. Stansbery E. Sweetnam D. Wiens R.C. 《Space Science Reviews》2003,105(3-4):509-534
The Genesis Discovery mission will return samples of solar matter for analysis of isotopic and elemental compositions in terrestrial
laboratories. This is accomplished by exposing ultra-pure materials to the solar wind at the L1 Lagrangian point and returning
the materials to Earth. Solar wind collection will continue until April 2004 with Earth return in Sept. 2004. The general
science objectives of Genesis are to (1) to obtain solar isotopic abundances to the level of precision required for the interpretation
of planetary science data, (2) to significantly improve knowledge of solar elemental abundances, (3) to measure the composition
of the different solar wind regimes, and (4) to provide a reservoir of solar matter to serve the needs of planetary science
in the 21st century. The Genesis flight system is a sun-pointed spinner, consisting of a spacecraft deck and a sample return
capsule (SRC). The SRC houses a canister which contains the collector materials. The lid of the SRC and a cover to the canister
were opened to begin solar wind collection on November 30, 2001. To obtain samples of O and N ions of higher fluence relative
to background levels in the target materials, an electrostatic mirror (‘concentrator’) is used which focuses the incoming
ions over a diameter of about 20 cm onto a 6 cm diameter set of target materials. Solar wind electron and ion monitors (electrostatic
analyzers) determine the solar wind regime present at the spacecraft and control the deployment of separate arrays of collector
materials to provide the independent regime samples.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献