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1.
Bertsch  D. L.  Biswas  S.  Reames  D. V. 《Solar physics》1974,39(2):479-491
Observations of the proton, helium, (C, N, O) and Fe-group nuclei fluxes made during the large 4 August 1972 solar particle event are presented. The results show a small, but significant variation of the composition of multiply-charged nuclei as a function of energy in the energy region above 10 MeV nucleon–1. In particular, the He/(C, N, O) abundance ratio varies by a factor 2 between 10 and 50 MeV nucleon–1 and the Fe-group/(C, N, O) ratio suggests a similar variation. Abundance ratios from the 4 August 1972 event are compared as a function of energy with ratios measured in other solar events to show that several of the earlier results are consistent with an energy variation like that observed in August 1972, while certain other events must have had a substantially different dependence of composition on energy. At energies 50 MeV nucleon–1, the He/(C, N, O) abundance ratio for August 1972 is consistent with all earlier measurements made above that energy which suggests that variations may vanish at high energies.NASA/NAS Senior Resident Research Associate, on leave from TATA Institute of Fundamental Research, Bombay.  相似文献   

2.
An experimental investigation of the isotopic composition of cosmic-ray nitrogen and oxygen is reported. The detector is a stack of nuclear emulsions exposed at about 3 g cm–2 atmospheric depth. The mass determinations are based on photometric track width measurements on stopping nuclei. The standard deviation of the mass measurements is 0.46 AMU for nitrogen and 0.50 AMU for oxygen. The energy of the measured nuclei falls in the interval 220–450 MeV nucleon–1 at the top of the atmosphere.The measured isotopic quotients have been extrapolated to near interstellar space with standard methods. The extrapolated quotients are15N/N=0.34±0.10,17O/O=0.02±0.03,18O/O=0.07±0.03. The nitrogen quotient extrapolated to the cosmic-ray source shows that the nitrogenoxygen abundance ratio is approximately the same in the source as in the solar system. The result has been compared with different hypotheses about the source composition and is found to be in best agreement with a hypothesis which states that source matter has approximately the composition of the solar system and that a selection mechanism, which depends on the atomic properties of the elements, is working in the source.  相似文献   

3.
The results of numerical simulation of stochastic acceleration of the heavy ions (3He, 4He, 16O, and 56Fe) are presented for the impulsive solar event of October 5, 2002. The energy spectra of the aforementioned particles have peculiarities (depressions) in the low-energy region (≤1 MeV nucleon−1). Coulomb losses in the flare plasma and adiabatic losses during interplanetary propagation are considered in the study as possible causes of such peculiarities.  相似文献   

4.
The stochastic acceleration of heavy ions by Alfvén turbulence is considered with allowance for Coulomb losses. The pattern of energy dependence of these losses gives rise to characteristic features in the energy spectra of the accelerated particles at energies of the order of several MeV nucleon?1. The manifestation of these features in the spectra is sensitive to the temperature and density of the medium, which can serve as a basis for plasma diagnostics in the flare region. Some impulsive solar energetic particle events during which features in the spectra of 3He and 4He were observed are considered as an example.  相似文献   

5.
The differential flux and energy spectra of solar cosmic ray heavy ions of He, C, O, Ne, Mg, Si, and Fe were determined in the energy interval E = 3–30 MeV amu-1 for two large solar events of January 24, 1971 and September 1, 1971 in rocket flights made from Ft. Churchill. From these data the relative abundances and the abundance enhancement factors, ξ, relative to photospheric abundances were obtained for these elements. Similar results were obtained for a third event on August 4, 1972 from the available published data. Characteristic features of ξ vs nuclear charge dependences were deduced for five energy intervals. The energy dependence of ξ for He shows a moderate change by a factor of about 3, whereas for Fe, ξ shows a very dramatic decrease by a factor of 10–20 with increasing energy. It is inferred that these abundance enhancements of solar cosmic ray heavy ions at low energies seem to be related to their ionization states (Z *) and hence studies of Z * can give information on the important parameters such as temperature and density in the accelerating region in the Sun.  相似文献   

6.
Differential energy spectra of low abundant elements between silicon and iron of energetic solar particles (SEP) in the August 4, 1972 event were measured in the energy region of 10 to 40 MeV amu–1 using rocket-borne Lexan detectors. The relative abundances of elements were determined and abundance enhancements, i.e., SEP/photospheric ratios, and their energy dependence were derived in 10–40 MeV amu–1 interval. It is found that there are four types of abundance enhancements as a function of energy as follows: (a) silicon, iron, and calcium show fairly strong energy dependence which decreases with increasing energy and at 20–40 MeV amu–1 reaches photospheric values; (b) in case of sulphur enhancement factors are independent of energy and the values are close to unity; (c) argon shows energy independent enhancements of about 3 to 4 in 10–40 MeV amu–1; (d) titanium and chromium show weakly energy-dependent, but very high abundance enhancement factor of about 10 to 40. These features are to be understood in terms of the atomic properties of these elements and on the physical conditions in the accelerating region. These are important not only for solar phenomena but also to gain insight into the abundance enhancements of cosmic-ray heavy nuclei.on leave from Tata Institute of Fundamental Research, Bombay, India.  相似文献   

7.
More than a thousand interactions of primary heavy nuclei of the cosmic radiation with charge ≥10 and energy >1 GeV nucleon?1 in nuclear emulsion have been studied with emphasis on how the primary nucleus fragments. It has been determined that the cases of multiple successive fragmentations that have been observed do not occur more frequently than expected. The fragmentation ofZ>20 nuclei does depend on the target nucleus to some extent so it is important to try to separate the interactions in emulsion by theirN h (number of evaporation prongs). The fragmentation of 8 16 O at 2.1 GeV nucleon?1 measured at the Bevalac shows a similar dependence on target nucleus. By using data from these new interactions combined with published data we have simulated on a computer nuclear cascades in both emulsion and air. Results on these cascades are given for both primary silicon and primary iron nuclei. These results are used to discuss the fluctuations expected in extensive air showers produced by heavy primary nuclei.  相似文献   

8.
On the basis of solar flare forecasts, balloon flights were made from Hyderabad, India (vertical geomagnetic threshold rigidity of 16.9 GV), to detect the possible emission of high energy neutrons during solar flares. The detector comprised of a central plastic scintillator, completely surrounded by an anticoincidence plastic scintillator shield. The instrument responds to neutrons of about 15–150 MeV and gamma rays of about 5–30 MeV with about the same efficiency. The detector was flown to an atmospheric depth of 25 g cm-2 on February 26, 1969; while the balloon was at ceiling a flare of importance 2B and one of 1N occurred. No perceptible flare associated increase in the counting rate was observed. Using the observed counting rates, an upper limit of 1.2 × 10-2 neutrons cm-2 sec-1 is obtained for the first time for a flare of importance 2B for neutrons of energy 15–150 MeV. The corresponding upper limit for gamma rays of energy 5–30 MeV is found to be 10-2 photons cm-2 sec-1. The neutron flux limits are compared with the recent calculations of Lingenfelter.  相似文献   

9.
The intensity and energy spectra of multiply charged cosmic ray nuclei, in the energy interval 250–1500 MeV/n, were studied at three different levels of solar activity, viz. in 1963, 1964 and 1967. The same detectors, nuclear emulsion stacks flown from Fort Churchill, Canada, were used to determine simultaneouslty the energy spectra of helium, C, N, O as well as H (Z=10–28) nuclei. An analysis of the measured spectra indicates that these can be interpreted in terms of: (a) the source spectrum as a Fermi spectrum with a spectral index of 2.65; (b) the interstellar propagation as in a Gaussian distribution of path lengths with a mean path length of 4 g cm–2 and (c) the interplanetary propagation as given by the numerical solution of the Fokker-Planck equation incorporating diffusion, convection and adiabatic deceleration. On comparing the measured ratios of He to H-nuclei (mean Z14) with the theoretically calculated values for the three levels of solar activity, it is found that within experimental uncertainties, the solar modulation is essentially the same for nuclei of same mass to charge ratio and is not dependent on the charge of the nuclei.On leave from Tata Institute of Fundamental Research, Bombay.  相似文献   

10.
The study of nuclear line spectra from solar flares holds a rich promise for elucidating the properties of both the accelerated particles and the interaction or target region. We review the observations and the analysis of the large nuclear line rich flare which occurred near the west limb starting at 08:03 UT on 27 April, 1981. The observed spectrum from this flare contains three intense and isolated gamma-ray lines which can be analyzed in a model independent way. The measured energies are 1.628 ± 0.008, 4.430 ± 0.011, and 6.147 ± 0.022 MeV, identifying them as the de-excitation lines of 20Ne (1.634 MeV), 12C (4.438 MeV), and 16O (6.129 MeV). Elemental abundances of the ambient gas at the site of gamma-ray line production in the solar atmosphere are deduced using these gamma-ray line observations. The resultant abundances are different from local galactic abundances which are thought to be similar to photospheric abundances.Resident Research Associate at NRL under the NRC Associateship Program.  相似文献   

11.
Hadronic cosmic rays of energies below about 100 MeV nucleon–1 are thought to be an important component of the Galactic ecosystem. However, since these particles cannot be detected near Earth due to the solar modulation effect, their composition and flux in the interstellar medium are very uncertain. Atomic interactions of low‐energy cosmic rays with interstellar gas can produce a characteristic nonthermal X‐ray emission comprising very broad lines from de‐excitations in fast ions following charge exchange. We suggest that broad lines at ∼0.57 and ∼0.65 keV could be detected from a dark molecular cloud in the local interstellar medium. These lines would be produced by fast oxygen ions of kinetic energies around 1 MeV nucleon–1 (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

12.
Relative abundances of energetic nuclei in the 4 July 1974 solar event are presented. The results show a marked enhancement of abundances that systematically increase with nuclear charge numbers in the range of the observation, 6 Z 26 for energies above 15 MeV nucl.–1 While such enhancements are commonly seen below 10 MeV nucl–1, most observations at higher energies are found to be consistent with solar system abundances. The energy spectrum of oxygen is observed to be significantly steeper than most other solar events studied in this energy region. It is proposed that these observations are characteristic of particle populations at energies 1 MeV nucl–1, and that the anomalous features observed here may be the result of the high energy extension of such a population that is commonly masked by other processes or populations that might occur in larger solar events.  相似文献   

13.
The results of simultaneous measurements of variations of UV radiation (in a band near the hydrogen Lα line, 121.6 nm) and hard X-ray and gamma-ray radiation (50 keV-200 MeV) performed by the VUSS-L and SONG instruments, respectively, onboard the CORONAS-F spacecraft are presented for periods of solar flares. Variations in the Lα ultraviolet radiation during the impulsive phase of a flare are shown to be synchronous with those of hard X-ray radiation. Temporal variations of UV and X-ray fluxes correspond to the progressive heating of higher and higher regions of the solar atmosphere and the energy transfer from the lower layers of the solar atmosphere to the coronal areas of flare regions. The energy of electrons in beams arising during the impulsive phase of flares can be as high as 500 keV. The velocity of the energy propagation from the regions of its release to the upper layers of the solar atmosphere can reach several tens of kilometers per second.  相似文献   

14.
Most of the energy in a solar flare, and presumably a stellar flare as well, takes the form of a power law of energetic particles. The energetic electrons produce a bremsstrahlung continuum, while the most energetic nuclei produce gamma‐rays. Nuclei around 1 MeV/AMU can produce X‐rays during and after charge transfer with neutrals. This paper predicts the fluxes for some prominent X‐ray lines and compares them to existing spectra (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

15.
A statistical analysis of the contemporary (1954-1975) solar flare particle events has been made for the parametersF (integrated, proton fluence in cm-2 in an event with kinetic energy above 10 MeV) andR 0 (the characteristic rigidity). These data are compared with the long-term averaged values determined from stable- and radio-nuclide measurements of lunar samples. The analysis shows that the ancient solar flare proton spectrum was harder (higher R0 values) compared to that observed in contemporary flares. A similar analysis can not be made for the mean long-term averaged flux (ˉJ, cm-2 S-1), since the contemporary averages suffer from an uncertainty due to the statistics of a single event. However, the average flux estimates for time durations 〈T〉 exceeding 103 yr, are free from such uncertainties. The long-term averaged ˉJ values obtained over different time scales (104 - 106 yr) suggest a possible periodic variation in solar flare activity, with enhanced flux level during the last 105 yr. The available data rule out the occurrence of giant flares, with proton fluence exceeding 1015 cm-2 during the last million years.  相似文献   

16.
Thirty active regions were observed on the Sun during the period from October 19 to November 20, 2003. Hard X-ray and gamma-ray radiation was detected from four active regions (10484, 10486, 10488, and 10490): 14 solar flares stronger than M5.0 according to the GOES classification were recorded during this period by detectors onboard the Geostationary Operational Environmental Satellite (GOES), Ramaty High Energy Solar Spectroscopic Imager (RHESSI), and other satellites. Five of these flares (and also the M2.7 flare of October 27, 2003) were also observed by the AVS-F apparatus onboard the CORONAS-F satellite. This paper discusses the time profiles and energy spectra of the solar flares of October 26, 2003 (M7.6), and October 29, 2003 (X10), and of the initial phase of the flare of November 4, 2003 (X18), obtained by the AVS-F instrument during the passage of the satellite over the regions near the geomagnetic equator. The spectra of the M7.6 flare of October 26, 2003, and of the initial phase of the X18 flare of November 4, 2003, in the energy band from 0.1 to 17 MeV contain no lines, whereas the spectrum of the flare of October 29, 2003, exhibits nuclear lines and the 2.2-MeV line during the entire flare gamma-ray emission registration. We also report the time profiles of the flare of October 29, 2003, in the energy bands corresponding to the continuum in the energy band 0.3–0.6 MeV, the nuclear lines of 56Fe, 24Mg, 20Ne, 28Si, 12C, and 16O, and the 2.2-MeV neutron-capture line. The analysis of these temporal profile periodograms shows the presence of a thin structure with characteristic scales from 34 to 158 s at the 99% confidence level. The AVS-F apparatus analyzes temporal profiles of low-energy gamma-ray emission with a temporal resolution of 1 ms within the first 4.096 seconds of solar flares. The analysis of the data reveals no regularities in the time series on time scales ranging from 2 to 100 ms at a confidence level of 99% for these three solar flares.  相似文献   

17.
Measurements of the flux of helium nuclei in the 24 January, 1971, event and of helium and (C, N, O) nuclei in the 1 September, 1971, event are combined with previous measurements to obtain the relative abundances of helium, (C, N, O), and Fe-group nuclei in these events. These data are then summarized together with previously reported results to show that, even when the same detector system using a dE/dx plus range technique is used, differences in the He/(C, N, O) value in the same energy/nucleon interval are observed in solar cosmic ray events. Further, when the He/(C, N, O) value is lower the He/(Fe-group nuclei) value is also systematically lower in these large events. When solar particle acceleration theory is analyzed, it is seen that the results suggest that, for large events, Coulomb energy loss probably does not play a major role in determining solar particle composition at higher energies (> 10 MeV). The variations in multicharged nuclei composition are more likely due to partial ionization during the acceleration phase.NASA/NAS Senior Resident Research Associate, on leave from Tata Institute of Fundamental Research, Bombay.  相似文献   

18.
We briefly describe our recent Monte Carlo calculations of the energy and angular distributions of neutrons escaping from the solar atmosphere. Comparing the calculation results with measurements of the neutron flux from the flares, we determined the angular distribution and energy spectrum of the accelerated ions. We also describe our calculations of the time dependence of the 2.223 MeV line emission, which provide a sensitive measure of the photospheric 3He abundance. We find that the SMM measurements of the time dependence of the 2.2 MeV line emission from the flare of 1982 June 3 imply a 3He/H ratio of (2.3±1.2)×10–5 at the 90% confidence level.  相似文献   

19.
A series of telescopes having approximately a 30° half opening angle and responding to neutrons in the energy range 50 MeV to 350 MeV has been flown to the top of the atmosphere on balloons released from an equatorial launching site at Kampala, Uganda, between 1967 and 1969. The aim of the experiment was to attempt to detect solar neutrons during periods of enhanced solar activity. No neutrons of solar origin were detected, but an upper limit of the order of 30 neutrons m–2 s–1 at the Earth has been placed on the continuous solar neutron flux in the above energy range, and a limit of four photons m–2 s–1 has also been placed on the corresponding -ray flux above 80 MeV. Limits have likewise been placed on the total emission from various flares. For a 1B flare the values were 23 × 104 neutrons m–2 and 6 × 104 photons m–2.  相似文献   

20.
We analyze the observations of solar protons with energies >80 MeV near the Earth and the January 20, 2005, solar flare in various ranges of the electromagnetic spectrum. Within approximately the first 30 min after their escape into interplanetary space, the solar protons with energies above 80 MeV propagated without scattering to the Earth and their time profiles were determined only by the time profile of the source on the Sun and its energy spectrum. The 80–165 MeV proton injection function was nonzero beginning at 06:43:80 UT and can be represented as the product of the temporal part, the ACS (Anticoincidence System) SPI (Spectrometer on INTEGRAL) count rate, and the energy part, a power-law proton spectrum ～E ?4.7±0.1. Protons with energies above 165 MeV and relativistic electrons were injected, respectively, 4 and 9 min later than this time. The close correlation between high-energy solar electromagnetic emission and solar proton fluxes near the Earth is evidence for prolonged and multiple proton acceleration in solar flares. The formation of a posteruptive loop system was most likely accompanied by successive energy releases and acceleration of charged particles with various energies. Our results are in conflict with the ideas of cosmic-ray acceleration in gradual solar particle events at the shock wave driven by a coronal mass ejection.  相似文献   

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