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1.
The MSX infrared dark cloud G79.2+0.38 has been observed over a 11′×′ region simultaneously in the J=1-0 rotational transition lines of the 12CO and its isotopic molecules 13CO and 18CO. The dense molecular cores defined by the C18O line are found to be associated with the two high-extinction patches shown in the MSX A-band image. The two dense cores have the column density N (H2) (5 – 12) × 1022 cm−2 and the mean number density n (3 ± 1) × 104 cm−3. Their sizes are 1.7 and 1.2 pc in 13CO(1-0) line, 1.2 and 0.6 pc in C18O(1-0) line, respectively. The masses of these cloud cores are estimated to be in the range from 2 × 102 to 2 × 103 M. The profile of radial mean density of the cloud core can be described by the exponential function ¯n(p) p−0.34±0.02. Compared with the cases of typical optical dark clouds, the abundances of the CO isotopic molecules 13CO and C18O in this MSX infrared dark cloud appear to be depleted by a factor of 4–11, but at present there is no evidence for any obvious variation of the relative abundance ratio X13/18 between 13CO and C18O with the column density.  相似文献   

2.
An interpretation of Akeno giant air shower array (AGASA) data by comparing the experimental results with the simulated ones by cosmic ray simulation for KASCADE (CORSIKA) has been made. General features of the electromagnetic component and low energy muons observed by AGASA can be well reproduced by CORSIKA. The form of the lateral distribution of charged particles agrees well with the experimental one between a few hundred metres and 2000 m from the core, irrespective of the hadronic interaction model studied and the primary composition (proton or iron). It does not depend on the primary energy between 1017.5 and 1020 eV as the experiment shows. If we evaluate the particle density measured by scintillators of 5 cm thickness at 600 m from the core S0(600), suffix 0 denotes the vertically incident shower) by taking into account the similar conditions as in the experiment, the conversion relation from S0(600) to the primary energy is expressed as E (eV)=2.15×1017S0(600)1.015 within 10% uncertainty among the models and composition used, which suggests the present AGASA conversion factor is the lower limit. Although the form of the muon lateral distribution fits well to the experiment within 1000 m from the core, the absolute values change with hadronic interaction model and primary composition. The slope of the ρμ(600) (muon density above 1 GeV at 600 m from the core) vs. S0(600) relation in experiment is flatter than that in simulation of any hadronic model and primary composition. As the experimental slope is constant from 1015 to 1019 eV, we need to study this relation in a wide primary energy range to infer the rate of change of chemical composition with energy.  相似文献   

3.
The evolution of the cosmic ray primary composition in the energy range 106–107 GeV (i.e. the “knee” region) is studied by means of the e.m. and muon data of the Extensive Air Shower EAS-TOP array (Campo Imperatore, National Gran Sasso Laboratories). The measurement is performed through: (a) the correlated muon number (Nμ) and shower size (Ne) spectra, and (b) the evolution of the average muon numbers and their distributions as a function of the shower size. From analysis (a) the dominance of helium primaries at the knee, and therefore the possibility that the knee itself is due to a break in their energy spectrum (at EkHe=(3.5±0.3)×106 GeV) are deduced. Concerning analysis (b), the measurement accuracies allow the classification in terms of three mass groups: light (p,He), intermediate (CNO), and heavy (Fe). At primary energies E0≈106 GeV the results are consistent with the extrapolations of the data from direct experiments. In the knee region the obtained evolution of the energy spectra leads to: (i) an average steep spectrum of the light mass group (γp,He>3.1), (ii) a spectrum of the intermediate mass group harder than the one of the light component (γCNO2.75, possibly bending at EkCNO≈(6–7)×106 GeV), (iii) a constant slope for the spectrum of the heavy primaries (γFe2.3–2.7) consistent with the direct measurements. In the investigated energy range, the average primary mass increases from lnA=1.6–1.9 at E01.5×106 GeV to lnA=2.8–3.1 at E01.5×107 GeV. The result supports the standard acceleration and propagation models of galactic cosmic rays that predict rigidity dependent cut-offs for the primary spectra of the different nuclei. The uncertainties connected to the hadronic interaction model (QGSJET in CORSIKA) used for the interpretation are discussed.  相似文献   

4.
The energy spectrum of cosmic rays with primary energies between 1014 eV and 1016 eV has been studied with the CASA-MIA air shower array. The measured differential energy spectrum is a power law (dj/dE ∝ E−y) with spectral indices γ of 2.66±0.02 below approximately 1015 eV and 3.00±0.05 above. A new method is used for measuring primary energy derived from ground-based data in a compositionally insensitive way. In contrast with some previous reports, the “knee” of the energy spectrum does not appear sharp, but rather a smooth transition over energies from 1015 eV to 3.0 × 1015 eV.  相似文献   

5.
Rocket results are presented on the OI 6300 Å line and on the N2+ 3914 Å band in the dayglow. An altitude range of 78–335 km is covered. Theoretical interpretations are given, using results of simultaneous measurements of electron density and electron temperature. The apparent brightness of the 6300 Å line at the base of the emitting region is found to be 13 kR, of which 5.5 kR are ascribed to excitation through the Schumann-Runge dissociation of O2 by the solar UV radiations, 0.55 kR to the dissociative recombination of O2+ and NO+ ions, and 0.03 kR to the excitation of O by thermal electrons. An additional source of excitation above 280 km is suggested. The deactivation of O(1D) by O2(X3Σg−) is found to be appreciable below 200 km, and its rate coefficient is estimated to be 2 × 10−10 cm3/sec. The apparent brightness of the 3914 Å band at the base of the emitting region is found to be 6.5 kR, decreasing to 3.2 kR at 330 km. Assuming that fluorescent scattering of solar radiation is the mechanism involved the distribution of N2+ ions is calculated. The rate coefficients for the loss of these ions are hence calculated.  相似文献   

6.
The limb event 1982 Jan 22 with Type III + V and Type II bursts and Ha mass ejection is described. The bursts in short dm and cm waves are discussed in terms of the flux rate — time curve. For one main ejection, we find a magnetic field of ~12 G, a mass of ~1038 electrons or ~1014g and an energy of 8 × 1029 erg. We estimate the total energy of this event to be 1030 erg.  相似文献   

7.
We further discussed the Modified Mean Field Theory proposed in [1,2]. We found that this model has a new solution ml = 2; adding -meson, we calculated the symmetric energy of nuclear matter a4; with the new parameters we calculated the equations of state with and without the addition of -meson; we compared the two; we also compared with the results for ml = 4.3; we made a preliminary theoretical investigation of the form of the vector meson mean field using the two-body correlation function; lastly, using the structural equation of neutron star we calculated the maximum mass for the various equations of state. The results are:
MMFT-2 (ml = 2): Mmax = 2.22M (without -meson) Mmax = 2.27M (with -meson)
MMFT-1 (ml = 4.3): Mmax = 1.69M (without -meson) Mmax = 1.89M (with -meson)
  相似文献   

8.
《Astroparticle Physics》2003,19(6):715-728
The KASCADE experiment measures a high number of EAS observables with a large degree of sampling of the electron–photon, muon, and hadron components. It provides accurate data for an event-by-event analysis of the primary cosmic ray flux in the energy range around the knee. The possibility of selecting samples of enriched proton and iron induced extensive air showers by applying the statistical techniques of multivariate analyses is scrutinized using detailed Monte Carlo simulations of three different primaries. The purity and efficiency of the proton and iron classification probability is investigated. After obtaining enriched samples from the measured data by application of the procedures the reconstructed number of hadrons, hadronic energy and other parameters are investigated in the primary energy range 1015–1016 eV. By comparing these shower parameters for purified proton and iron events, respectively, with simulated distributions an attempt is made to check the validity of strong interaction models at high energies.  相似文献   

9.
Absolute values of the emission cross sections for five vibrational bands in the Meinel system of N2+,A2πu to X2Σg+, excited by electron impact are presented. From these, a value was obtained for the total excitation cross section of the A2πu state at 100 eV of 26·5 × 10−18 cm2. The results are compared with those of other workers and with theory. Collisional transfer of the excitation energy from the levels of the A2πu state was also observed with a transfer cross section of approximately 10−14 cm2.  相似文献   

10.
Linsley used the Volcano Ranch array to collect data on the lateral distribution of showers produced by cosmic rays at energies above 1017 eV. Very precise measurements of the steepness of the lateral distribution function were made on 366 events. The current availability of sophisticated hadronic interaction models has prompted an interpretation of the measurements. In this analysis we use the Monte Carlo code to generate showers, together with to simulate the detector response to ground particles. The results show that, with the assumption of a bi-modal proton and iron mix, iron is the dominant component of cosmic rays near 1018 eV, assuming that hadronic interactions are well-described by at this energy range. The Volcano Ranch data set, as available to us, does not allow a straightforward assignment of energy for each event. It is thus not possible to give the energy dependence of the mass composition.  相似文献   

11.
Based on the theory of the radio evolution of supernova remnants and the theory of x-ray emission, we have derived an expression for the energy of supernova eruption directly in terms of the observed radio flux density and x-ray luminosity. This method is used to estimate the energy of the supernova explosions in LMC and SMC. Our calculated values fall in the range 1049 – 1051 ergs, with the values for Type I supernovae systematically smaller than those for Type II, at about 1049 ergs. We point out that the most likely cause for the discrepancy between the statistical and theoretical N-D relations is incompletness of data. We also point out, in the two clouds, the vast majority of large sources are still in the phase of adiabatic expansion.  相似文献   

12.
An analysis has been made of the fraction of ultra high energy cosmic rays (above 1018 eV) which could be due to processes involved in two possible ‘Models’. The first is the Giant Magnetic Halo Model and the second is the Dark Matter Halo Model. We find that the former, in which heavy nuclei are trapped in a giant halo, fails for energies above about 3 × 1019 eV. For the Dark Matter Halo Model, in which relic particles follow the “conventional” dark matter and whose decays give ultra high energy cosmic rays, the predicted anisotropies are much higher than those observed. The lack of observation of a finite flux from the Andromeda Galaxy means that the conclusion is insensitive to the spatial scale size of the assumed halo distribution. It is concluded that less than 10% of the ultra high energy cosmic rays come from relic particles in the Galactic halo.  相似文献   

13.
Venera 9, 10 measurements of the nightside ionospheric profile and the night airglow were used for investigating ionosphere formation processes. The upper ionospheric layer may be formed by HeI 584 Å radiation; the lower layer by meteorite ionization. Upper limits on the electron energy flux, <4 × 108eV cm−2 s−1, the helium ion flux <107 cm−2 s−1, the nitric oxide mixing ratio, <1.5 × 10−4 and the atomic sulphur mixing ratio, <10−6, are deduced for ionospheric altitudes.  相似文献   

14.
A detailed simulation of the electromagnetic component of extensive air showers generated by 1011–1015 eV photons has been carried out by means of the EPAS code. We present and discuss the results concerning the longitudinal, lateral and temporal distributions of electrons and photons down to 1 MeV energy threshold.  相似文献   

15.
From the little we know of the physical conditions in γ-ray bursters, it seems that they are potentially effective in the acceleration of high-energy cosmic rays (CRs), especially if the bursters are at cosmological distances. We find that, with the observed statistics and fluxes of γ-ray bursts, cosmological bursters may be an important source of cosmic rays in two regions of the observed spectrum: (1) At the very-high-energy end (E > 1019 eV), where CRs must be of extragalactic origin. (2) Around and above the spectral feature that has been described as a bump and/or a knee, which occurs around 1015 eV. The occasional bursters that occur inside the Galaxy — about once in a few hundred thousand years if burst emission is isotropic; more often, if it is beamed — could maintain the density of galactic cosmic rays at the observed level in this range. These two energy ranges might correspond to two typical CR energy scales characteristic of bursters: one pertinent to CR acceleration due to interaction of a magnetized-fireball front with an ambient medium; the other to acceleration in the fireball itself (e.g. shock acceleration).  相似文献   

16.
《Astroparticle Physics》2003,19(6):703-714
The attenuation of the electron shower size beyond the shower maximum is studied with the KASCADE extensive air shower (EAS) experiment in the primary energy range of about 1014–1016 eV. Attenuation and absorption lengths are determined by applying different approaches, including the method of constant intensity, the decrease of the flux of EASs with increasing zenith angle, and its variation with ground pressure. We observe a significant dependence of the results on the applied method. The determined values of the attenuation length ranges from 175 to 196 g/cm2 and of the absorption length from 100 to 120 g/cm2. The origin of these differences is discussed emphasizing the influence of intrinsic shower fluctuations.  相似文献   

17.
Vertical fluxes of ionization in the F2 region have been measured by the incoherent scatter technique over Millstone Hill in 1969. The results obtained near midnight for the region above hmaxF2 have been examined to determine whether there is a significant flux of ionization from the magnetosphere to the ionosphere that serves to maintain the F-layer. It is found that H+ ions are a minor constituent over the altitude range in which useful measurements can be made, so that any conclusion must rest upon properly interpreting the observed O+ fluxes. By selecting periods when the layer did not appear to be decaying rapidly it was hoped to find cases where the O+ flux did not vary with altitude in the range 500 h 800 km (i.e. where losses are unimportant), since this would imply that the flux is of magnetospheric origin.

While three cases exhibited this behaviour, the majority exhibited a decrease in the O+ flux with height, indicating that the layer was descending. Attempts to correct for this were made, and the average flux from the magnetosphere was estimated as 3 × 107 el/cm2/sec. This is in fair agreement with other recent estimates, and implies that at this latitude the ionosphere is not maintained solely by the magnetospheric flux. Moreover, large increases in flux that could give rise to nocturnal increases in the total content of the layer do not appear to have been seen.  相似文献   


18.
We investigate the problem of transition from galactic cosmic rays to extragalactic ultra-high energy cosmic rays. Using the model for extragalactic ultra-high energy cosmic rays and observed all-particle cosmic ray spectrum, we calculate the galactic spectrum of iron nuclei in the energy range 108–109 GeV. The flux and spectrum predicted at lower energies agree well with the KASCADE data. The transition from galactic to extragalactic cosmic rays is distinctly seen in spectra of protons and iron nuclei, when they are measured separately. The shape of the predicted iron spectrum agrees with the Hall diffusion.  相似文献   

19.
We discuss the possibility of using pure CF4 to fill a 2000 m3 Time Projection Chamber in order to detect the solar neutrinos through the elastic scattering vee− → vee−, with the threshold of 100 keV on the kinetic energy of the recoiling electron. In a volume of 2000 m3 of CF4 at normal pressure and room temperature, which corresponds to a mass of 7.4 ton, we expect ~ 3300 of such events per year. The detector can give the spectrum of the low energy neutrinos from the Sun and it can identify solar neutrinos of different origin: pp, 7Be, and, eventually, 8B. We find that 14C is a possible severe source of background: it is necessary to have a ratio 14C/12C lower than 10−19 in order to be able to identify the pp neutrinos.  相似文献   

20.
We compare the tau neutrino flux arising from the galaxy and the earth atmosphere for 103E/GeV1011. The intrinsic and oscillated tau neutrino fluxes from both sources are calculated. The intrinsic galactic ντ flux (E103 GeV) is calculated by considering the interactions of high-energy cosmic-rays with the matter present in our galaxy, whereas the oscillated galactic ντ flux is coming from the oscillation of the galactic νμ flux. For the intrinsic atmospheric ντ flux, we extend the validity of a previous calculation from E106 GeV up to E1011 GeV. The oscillated atmospheric ντ flux is, on the other hand, rather suppressed. We find that, for 103E/GeV5×107, the oscillated ντ flux along the galactic plane dominates over the maximal intrinsic atmospheric ντ flux, i.e., the flux along the horizontal direction. We also briefly mention the presently envisaged prospects for observing these high-energy tau neutrinos.  相似文献   

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