共查询到20条相似文献,搜索用时 31 毫秒
1.
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
2.
Observations and measurements in the solar wind, the Jovian atmosphere and the gases trapped in lunar surface material provide
the main evidence from which the isotopic composition of H, He and Ne in the Protosolar Cloud (PSC) is derived. These measurements
and observations are reviewed and the corrections are discussed that are needed for obtaining from them the PSC isotopic ratios.
The D/H, 3He/4He (D+3He)/H, 20Ne/22Ne and 21Ne/22Ne ratios adopted for the PSC are presented. Protosolar abundances provide the basis for the interpretation of isotopic ratios
measured in the various solar system objects. In this article we discuss constraints derived from the PSC abundances on solar
mixing, the origin of atmospheric neon, and the nature of the “SEP” component of neon trapped at the lunar surface. We also
discuss constraints on the galactic evolution provided by the isotopic abundances of H and He in the PSC.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
3.
R. Karrer P. Bochsler C. Giammanco F. M. Ipavich J. A. Paquette P. Wurz 《Space Science Reviews》2007,130(1-4):317-321
Using the Mass Time-of-Flight Spectrometer (MTOF)—part of the Charge, Elements, Isotope Analysis System (CELIAS)—onboard the
Solar Heliospheric Observatory (SOHO) spacecraft, we derive the nickel isotopic composition for the isotopes with mass 58,
60 and 62 in the solar wind. In addition we measure the elemental abundance ratio of nickel to iron. We use data accumulated
during ten years of SOHO operation to get sufficiently high counting statistics and compare periods of different solar wind
velocities. We compare our values with the meteoritic ratios, which are believed to be a reliable reference for the solar
system and also for the solar outer convective zone, since neither element is volatile and no isotopic fractionation is expected
in meteorites. Meteoritic isotopic abundances agree with the terrestrial values and can thus be considered to be a reliable
reference for the solar isotopic composition. The measurements show that the solar wind elemental Ni/Fe-ratio and the isotopic
composition of solar wind nickel are consistent with the meteoritic values. This supports the concept that low-FIP elements
are fed without relative fractionation into the solar wind. Our result also confirms the absence of substantial isotopic fractionation
processes for medium and heavy ions acting in the solar wind. 相似文献
4.
The Advanced Composition Explorer 总被引:2,自引:0,他引:2
Stone E.C. Frandsen A.M. Mewaldt R.A. Christian E.R. Margolies D. Ormes J.F. Snow F. 《Space Science Reviews》1998,86(1-4):1-22
The Advanced Composition Explorer was launched August 25, 1997 carrying six high-resolution spectrometers that measure the
elemental, isotopic, and ionic charge-state composition of nuclei from H to Ni (1≤Z≤28) from solar wind energies (∼1 keV nucl−1)
to galactic cosmic-ray energies (∼500 MeV nucl−1). Data from these instruments is being used to measure and compare the elemental
and isotopic composition of the solar corona, the nearby interstellar medium, and the Galaxy, and to study particle acceleration
processes that occur in a wide range of environments. ACE also carries three instruments that provide the heliospheric context
for ion composition studies by monitoring the state of the interplanetary medium. From its orbit about the Sun-Earth libration
point ∼1.5 million km sunward of Earth, ACE also provides real-time solar wind measurements to NOAA for use in forecasting
space weather. This paper provides an introduction to the ACE mission, including overviews of the scientific goals and objectives,
the instrument payload, and the spacecraft and ground systems.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
5.
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
6.
Present natural data bases for abundances of the isotopic compositions of noble gases, carbon and nitrogen inventories can
be found in the Sun, the solar wind, meteorites and the planetary atmospheres and crustal reservoirs. Mass distributions in
the various volatile reservoirs provide boundary conditions which must be satisfied in modelling the history of the present
atmospheres. Such boundary conditions are constraints posed by comparison of isotopic ratios in primordial volatile sources
with the isotopic pattern which was found on the planets and their satellites. Observations from space missions and Earth-based
spectroscopic telescope observations of Venus, Mars and Saturn's major satellite Titan show that the atmospheric evolution
of these planetary bodies to their present states was affected by processes capable of fractionating their elements and isotopes.
The isotope ratios of D/H in the atmospheres of Venus and Mars indicate evidence for their planetary water inventories. Venus'
H2O content may have been at least 0.3% of a terrestrial ocean. Analysis of the D/H ratio on Mars imply that a global H2O ocean with a depth of ≤ 30 m was lost since the end of hydrodynamic escape. Calculations of the time evolution of the 15N/14N isotope anomalies in the atmospheres of Mars and Titan show that the Martian atmosphere was at least ≥ 20 times denser than
at present and that the mass of Titan's early atmosphere was about 30 times greater than its present value. A detailed study
of gravitational fractionation of isotopes in planetary atmospheres furthermore indicates a much higher solar wind mass flux
of the early Sun during the first half billion years.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
7.
Although coronal mass ejections have traditionally been thought to contribute only a minor fraction to the total solar particle
flux, and although such events mainly occur in lower heliographic latitudes, the impressive spectacle of eruptions - observed
with SOHO/LASCO even at times of solar minimum - indicates that an important part of the low-latitude solar corona is fed
with matter and magnetic fields in a highly transient manner. Elemental and isotopic abundances determined with the new generation
of particle instruments with high sensitivity and strongly enhanced time resolution indicate that, apart from FIP/FIT-fractionation,
mass-dependent fractionation can also influence the replenishment of the thermal ion population of the corona. Furthermore,
selective enrichment of the thermal coronal plasma with rare species such as 3He can occur. Such compositional features have until recently only been found in energetic particles from impulsive flare
events. This review will concentrate on this and other aspects of the present solar maximum and conclude with some outlook
on future investigations of near-terrestrial space climate (the generalized counterpart of ‘space weather’).
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
8.
R. Kallenbach F.M. Ipavich H. Kucharek P. Bochsler A.B. Galvin J. Geiss F. Gliem G. Gloeckler H. Grünwaldt S. Hefti M. Hilchenbach D. Hovestadt 《Space Science Reviews》1998,85(1-2):357-370
Using the high-resolution mass spectrometer CELIAS/MTOF on board SOHO we have measured the solar wind isotope abundance ratios
of Si, Ne, and Mg and their variations in different solar wind regimes with bulk velocities ranging from 330 km/s to 650 km/s.
Data indicate a small systematic depletion of the heavier isotopes in the slow solar wind on the order of (1.4±1.3)% per amu
(2σ-error) compared to their abundances in the fast solar wind from coronal holes. These variations in the solar wind isotopic
composition represent a pure mass-dependent effect because the different isotopes of an element pass the inner corona with
the same charge state distribution. The influence of particle mass on the acceleration of minor solar wind ions is discussed
in the context of theoretical models and recent optical observations with other SOHO instruments.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
9.
The ionic charge of solar energetic particles (SEP) as observed in interplanetary space is an important parameter for the
diagnostic of the plasma conditions at the source region and provides fundamental information about the acceleration and propagation
processes at the Sun and in interplanetary space. In this paper we review the new measurements of ionic charge states with
advanced instrumentation onboard the SAMPEX, SOHO, and ACE spacecraft that provide for the first time ionic charge measurements
over the wide energy range of ∼0.01 to 70 MeV/nuc (for Fe), and for many individual SEP events. These new measurements show
a strong energy dependence of the mean ionic charge of heavy ions, most pronounced for iron, indicating that the previous
interpretation of the mean ionic charge being solely related to the ambient plasma temperature was too simplistic. This energy
dependence, in combination with models on acceleration, charge stripping, and solar and interplanetary propagation, provides
constraints for the temperature, density, and acceleration time scales in the acceleration region. The comparison of the measurements
with model calculations shows that for impulsive events with a large increase of Q
Fe(E) at energies ≤1 MeV/nuc the acceleration occurs low in the corona, typically at altitudes ≤0.2 R
S
. 相似文献
10.
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
11.
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
12.
Nordholt Jane E. Wiens Roger C. Abeyta Rudy A. Baldonado Juan R. Burnett Donald S. Casey Patrick Everett Daniel T. Kroesche Joseph Lockhart Walter L. MacNeal Paul McComas David J. Mietz Donald E. Moses Ronald W. Neugebauer Marcia Poths Jane Reisenfeld Daniel B. Storms Steven A. Urdiales Carlos 《Space Science Reviews》2003,105(3-4):561-599
The primary goal of the Genesis Mission is to collect solar wind ions and, from their analysis, establish key isotopic ratios
that will help constrain models of solar nebula formation and evolution. The ratios of primary interest include 17O/16O and 18O/16O to ±0.1%, 15N/14N to ±1%, and the Li, Be, and B elemental and isotopic abundances. The required accuracies in N and O ratios cannot be achieved
without concentrating the solar wind and implanting it into low-background target materials that are returned to Earth for
analysis. The Genesis Concentrator is designed to concentrate the heavy ion flux from the solar wind by an average factor
of at least 20 and implant it into a target of ultra-pure, well-characterized materials. High-transparency grids held at high
voltages are used near the aperture to reject >90% of the protons, avoiding damage to the target. Another set of grids and
applied voltages are used to accelerate and focus the remaining ions to implant into the target. The design uses an energy-independent
parabolic ion mirror to focus ions onto a 6.2 cm diameter target of materials selected to contain levels of O and other elements
of interest established and documented to be below 10% of the levels expected from the concentrated solar wind. To optimize
the concentration of the ions, voltages are constantly adjusted based on real-time solar wind speed and temperature measurements
from the Genesis ion monitor. Construction of the Concentrator required new developments in ion optics; materials; and instrument
testing and handling.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
13.
The measured D/H ratios in interstellar environments and in the solar system are reviewed. The two extreme D/H ratios in solar
system water - (720±120)×10−6 in clay minerals and (88±11)×10−6 in chondrules, both from LL3 chondritic meteorites - are interpreted as the result of a progressive isotopic exchange in
the solar nebula between deuterium-rich interstellar water and protosolar H2. According to a turbulent model describing the evolution of the nebula (Drouart et al., 1999), water in the solar system cannot be a product of thermal (neutral) reactions occurring in the solar nebula. Taking
720×10−6 as a face value for the isotopic composition of the interstellar water that predates the formation of the solar nebula, numerical
simulations show that the water D/H ratio decreases via an isotopic exchange with H2. During the course of this process, a D/H gradient was established in the nebula. This gradient was smoothed with time and
the isotopic homogenization of the solar nebula was completed in 106 years, reaching a D/H ratio of 88×10−6. In this model, cometary water should have also suffered a partial isotopic re-equilibration with H2. The isotopic heterogeneity observed in chondrites result from the turbulent mixing of grains, condensed at different epochs
and locations in the solar nebula. Recent isotopic determinations of water ice in cold interstellar clouds are in agreement
with these chondritic data and their interpretation (Texeira et al., 1999).
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
14.
M. I. Desai G. M. Mason R. E. Gold S. M. Krimigis C. M. S. Cohen R. A. Mewaldt J. E. Mazur J. R. Dwyer 《Space Science Reviews》2007,130(1-4):243-253
Using high-resolution mass spectrometers on board the Advanced Composition Explorer (ACE), we surveyed the event-averaged
∼0.1–60 MeV/nuc heavy ion elemental composition in 64 large solar energetic particle (LSEP) events of cycle 23. Our results
show the following: (1) The Fe/O ratio decreases with increasing energy up to ∼10 MeV/nuc in ∼92% of the events and up to
∼60 MeV/nuc in ∼64% of the events. (2) The rare isotope 3He is greatly enhanced over the corona or the solar wind values in 46% of the events. (3) The heavy ion abundances are not
systematically organized by the ion’s M/Q ratio when compared with the solar wind values. (4) Heavy ion abundances from C–Fe exhibit systematic M/Q-dependent enhancements that are remarkably similar to those seen in 3He-rich SEP events and CME-driven interplanetary (IP) shock events. Taken together, these results confirm the role of shocks
in energizing particles up to ∼60 MeV/nuc in the majority of large SEP events of cycle 23, but also show that the seed population
is not dominated by ions originating from the ambient corona or the thermal solar wind, as previously believed. Rather, it
appears that the source material for CME-associated large SEP events originates predominantly from a suprathermal population
with a heavy ion enrichment pattern that is organized according to the ion’s mass-per-charge ratio. These new results indicate
that current LSEP models must include the routine production of this dynamic suprathermal seed population as a critical pre-cursor
to the CME shock acceleration process. 相似文献
15.
James J. Connell 《Space Science Reviews》2001,99(1-4):41-50
The cosmic ray isotopic composition measurements from the High Energy Telescope (HET) on the Ulysses spacecraft are reviewed. The source isotopic composition of key elements is found to be surprisingly like the Solar system abundances with the notable exception of 22Ne. The average density of interstellar material cosmic rays traverse is found to be 0.25 atom cm–3, corresponding to a confinement time of 20 Myr. Vanadium isotopic abundances are shown to be consistent with weak cosmic-ray reacceleration. The implications of these measurements are discussed. 相似文献
16.
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
17.
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. Trexel H. von Rosenvinge T.T. Binns W.R. Crary D.J. Dowkontt P. Epstein J. Hink P.L. Klarmann J. Lijowski M. Olevitch M.A. 《Space Science Reviews》1998,86(1-4):285-356
The Cosmic-Ray Isotope Spectrometer is designed to cover the highest decade of the Advanced Composition Explorer's energy
interval, from ∼50 to ∼500 MeV nucl−1, with isotopic resolution for elements from Z≃2 to Z≃30. The nuclei detected in this
energy interval are predominantly cosmic rays originating in our Galaxy. This sample of galactic matter can be used to investigate
the nucleosynthesis of the parent material, as well as fractionation, acceleration, and transport processes that these particles
undergo in the Galaxy and in the interplanetary medium.
Charge and mass identification with CRIS is based on multiple measurements of dE/dx and total energy in stacks of silicon
detectors, and trajectory measurements in a scintillating optical fiber trajectory (SOFT) hodoscope. The instrument has a
geometrical factor of ∼r250 cm2 sr for isotope measurements, and should accumulate ∼5×106 stopping heavy nuclei (Z>2) in two
years of data collection under solar minimum conditions.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
18.
P. Bochsler 《Space Science Reviews》1998,85(1-2):291-302
The composition of the solar wind is largely determined by the composition of the source material, i.e. the present-day composition
of the outer convective zone. It is then modified by the processes which operate in the transition region and in the inner
corona. In situ measurements of the solar wind composition give a unique opportunity to obtain information on the isotopic
and elemental composition of the Sun. However, elemental — and to some degree also isotopic — fractionation can occur in the
flow of matter from the outer convective zone into the interplanetary space. The most important examples of elemental fractionation
are the well-known FIP/FIT effect (First Ionization Potential/Time) and the sometimes dramatic variations of the helium abundance
relative to hydrogen in the solar wind. A thorough investigation of fractionation processes which cause compositional variations
in different solar wind regimes is necessary to make inferences about the solar source composition from solar wind observations.
Our understanding of these processes is presently improving thanks to the detailed diagnostics offered by the optical instrumentation
on SOHO. Correlated observations of particle instruments on Ulysses, WIND, and SOHO, together with optical observations will
help to make inferences for the solar composition. Continuous in situ observations of several isotopic species with the particle
instruments on WIND and SOHO are currently incorporated into an experimental database to infer isotopic fractionation processes
which operate in different solar wind regimes between the solar surface and the interplanetary medium.
Except for the relatively minor effects of secular gravitational sedimentation which works at the boundary between the outer
convective zone and the radiative zone, refractory elements such as Mg can be used as faithful witnesses to monitor the magnitude
of these processes. With theoretical considerations it is possible to make inferences about the importance of isotopic fractionation
in the solar wind from a comparison of optical and in situ observations of elemental fractionation with the corresponding
models.
Theoretical models and preliminary results from particle observations indicate that the combined isotope effects do not exceed
a few percent per mass unit. In the worst case, which concerns the astrophysically important 3He/4He ratio, we expect an overall
effect of at most several percent in the sense of a systematic depletion of the heavier isotope. Continued observations with
WIND, SOHO, and ACE, and, with the revival of the foil technique, with the upcoming Genesis mission will further consolidate
our knowledge about the relation between solar wind dynamics and solar wind composition.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
19.
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
20.
Nuclear processes and particle acceleration in solar flares are reviewed. The theory of gamma-ray and neutron production is discussed and results of calculations are compared to gamma-ray, neutron, and charged-particle observations from solar flares. The implications of these comparisons on particle energy spectra, total numbers, anisotropies, electron-to-proton ratios, as well as on acceleration mechanisms and the interaction site, are presented. The information on elemental and isotopic abundances derived from gamma-ray observations is compared to abundances obtained from escaping accelerated particles and other sources.NAS/NRC Resident Research Associate. 相似文献