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1.
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   

2.
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   

3.
We have done extensive Monte Carlo simulations using the new simulation codes of CORSIKA and COSMOS to compare with the gamma-family data obtained at Mts. Fuji (3750 m above sea level) and Kanbala (5500 m above sea level). Then, we estimated the primary proton and helium spectra around the knee energy region using a multiple-layered feed-forward neural network as a classifier of primary particle kind. The selection efficiency of proton-induced family events is estimated to be 82%. The flux value of protons at 2×1015 eV is (5.5±1.5)×10−14 (m−2 s−1 sr−1 GeV−1). The result suggests heavy-enriched primary composition around the knee region.  相似文献   

4.
《Astroparticle Physics》2005,22(5-6):339-353
Data taken during 1997 with the AMANDA-B10 detector are searched for a diffuse flux of neutrinos of all flavors with energies above 1016 eV. At these energies the Earth is opaque to neutrinos, and thus neutrino induced events are concentrated at the horizon. The background are large muon bundles from down-going atmospheric air shower events. No excess events above the background expectation are observed and a neutrino flux following E−2, with an equal mix of all flavors, is limited to E2Φ(1015 eV < E < 3 × 1018 eV)  0.99 × 10−6 GeV cm−2 s−1 sr−1 at 90% confidence level. This is the most restrictive experimental bound placed by any neutrino detector at these energies. Bounds to specific extraterrestrial neutrino flux predictions are also presented.  相似文献   

5.
O+(4S) + H2O charge-transfer cross-section and product-ion time-of-flight measurements are presented over a center-of-mass collision energy range of 0.2–15 eV. The results are obtained with a newly constructed guided-ion beam experiment. The measured energy dependence of the charge-transfer crosssection agrees well with previous measurements and ADO model predictions of Bates [Chem. Phys. Lett. 82, 396 (1981) Proc. R. Soc. Lond. A384, 289 (1982) Chem. Phys. Lett. 111, 428 (1984)] at low collision energies, but exhibits significant differences at collision energies above 2 eV. The product kinetic energy analysis shows that most of the product ions are produced with near-thermal kinetic energies. At low collision energies, a significant backscattered channel is observed that is associated with complex formation. This channel exhibits a cross-section of approximately 1.4 Å2at a collision energy of 2.65 eV, corresponding to a laboratory ion energy of 5 eV.  相似文献   

6.
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   

7.
If neutrinos have mass, we give reasons for a possible pattern of three (squaed) mass eigenvalues: m12 (2.8−5.8) (eV)2, m22 0.01 (eV)2, m32 (1.5−1) × 10−4 (eV)2. The flavor states νμ and νe are mixtures of the eigenstates with m2 and m3 with a significant mixing, corresponding to an effective mixing angle of about 0.45. The ντ is nearly the state with m1; the other two effective mixing angles are about an order of magnitude smaller than 0.45. There is a marked similarity to mixing in the quark sector.  相似文献   

8.
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   

9.
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   

10.
《Astroparticle Physics》2001,14(4):245-260
Measurements of electron, muon and hadron lateral distributions of extensive air showers as recorded in the Karlsruhe shower core and array detector experiment are presented. The data cover the energy range from 5×1014 eV up to almost 1017 eV and extend from the inner core region to distances of 200 m. The electron and muon distributions are corrected for mutual contaminations by taking into account the detector properties in the experiment. All distributions are well described by NKG functions. The scale radii describing the electron and hadron data best are 30 and 10 m, respectively. We discuss the correlation between the scale radii and the ‘age' parameter as well as their dependence on shower size, zenith angle, and particle energy threshold.  相似文献   

11.
Characteristics of the supersonic auroral arcs within the 0905 UT 2 April 1973 substorm were determined using data from (1) all-sky cameras; (2), surface magnetometers, (3) multispectral scanning photometers, (4) 30MHz riometers, (5) Chatanika incoherent-scatter radar, (6) Homer auroral radar, and (7) infrasonic microphone arrays at College and Stevens Village in Alaska. These data were analyzed to determine the properties of an auroral electrojet arc that generates auroral infrasonic waves (AIW).

An arc that was show to be the source of an AIW was found to have the following characteristics: (1) a velocity of 500 m/sec traveling from an azimuth of 350°; (2) an intensity in 4278 A of 26 Kr, (3) a maximum electron density of 2.8 × 106 el/cm6 at 100km height, (4) an equivalent westward line current of 2.8 × 106 A, (5) orientation of ΔH parallel to the AIW direction of travel and perpendicular to the arc's long axis, (6) a characteristic energy of the primary auroral electron spectrum of 3.0keV, and (7) an energy deposition rate for the auroral pdarticles of 100 erg/cm2 sec.  相似文献   


12.
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   

13.
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   

14.
Using the 13.7 m millimeter-wave telescope at the Qinghai Station of Purple Mountain Observatory, we have made observations of 13CO, C18O, HCO+ and N2H+ molecular lines towards IRAS 02232+6138. As the excitation density of the probe molecule increases from 13CO to HCO+, the size of the cloud core associated with IRAS 02232+6138 decreases from 2.40 pc to 0.54 pc, and the virial mass of the cloud core decreases from 2.2 × 103M to 5.1 × 102M. A bipolar molecular outflow is found towards IRAS 02232+6138. Using the power function n(r) ∝ r− to fit the spatial density structure of the cloud core, we obtain the power-law index  = 2.3 − 1.2; and we find that, as the probed density increases, the power function becomes more flat. The abundance ratio of 13CO to C18O is 12.4 ± 6.9, comparable with the values 11.8 ± 5.9 for dark clouds and the values 9.0–15.6 for massive cores. The abundance of N2H+ molecules is 3.5 ± 2.5 × 10−10, consistent with the value 1.0 − 5.0 × 10−10 for dark cloud cores and the value 1.2 − 12.8 × 10−10 for massive cores. The abundance of HCO+ molecules is 0.9 ± 0.5 × 10−9, close to the value 1.6 − 2.4 × 10−9 for massive cores. An increase of HCO+ abundance in the outflow region was not found. Combining with the IRAS data, the luminosity-mass ratio of the cloud core is obtained in the range 37–163(L/M). Based on the IRAS luminosity, it is estimated that a main-sequence O7.5 star is probably embedded in the IRAS 02232+6138 cloud core.  相似文献   

15.
Data taken with ten Cosmic Ray Tracking (CRT) detectors and the HEGRA air-shower array on La Palma, Canary Islands, have been analysed to investigate changes of the cosmic ay mass composition at the ‘knee’ of the cosmic-ray flux spectrum near 1015 eV energy. The analysis is based on the angular distributions of particles in air showers. HEGRA data provided the shower size, direction, and core position and CRT data the particle track information. It is shown that the angular distribution of muons in air showers is sensitive to the composition over a wide range of shower sizes and, thus, primary cosmic-ray energies with little systematic uncertainties. Results can be easily expressed in terms of ln A of primary cosmic rays. In the lower part of the energy range covered, we have considerable overlap with direct composition measurements by the JACEE collaboration and find compatible results in the observed rise of ln A. Above about 1015 eV energy we find no or at most a slow further rise of ln A. Simple cosmic-ray composition models are presented which are fully consistent with our results as well as the JACEE flux and composition measurements and the flux measurements of the Tibet ASγ collaboration. Minimal three-parameter composition models defined by the same power-law slope of all elements below the knee and a common change in slope at a fixed rigidity are inconsistent with these data.  相似文献   

16.
Recent rocket observations of the N2 V-K (Vegard-Kaplan) system in the aurora have been reinterpreted using an atmospheric model based on mass spectrometer measurements in an aurora of similar intensity at the same time of year. In contrast to the original interpretation, we find that population by cascade from the C3Πu and B3Πg states in the A3Σu+v=0,1 levels, as calculated using recently measured electron excitation cross sections, accurately accounts for the observed relative emission rates (IV-K/12PG0.0). In addition there is no need to change the production rate of A 3 Σ u+ molecules relative to that of C3Πuv=0 as a function of altitude in order to fit the profile of the deactivation probability to the atmospheric model. Quenching of A 3 Σ u+ molecules at high altitudes is dominated by atomic oxygen. The rate constants for the v=0 and v=1 levels are 8 × 10−11 cm3 sec−1 and 1.7 × 10−10 cm3 sec−1 respectively, as determined using the model atmosphere mentioned above. Recent observations with a helium cooled mass spectrometer suggest that conventional mass spectrometer measurements tend to underestimate the atomic oxygen relative concentration. The rate coefficients may therefore be too large by as much as a factor of 3. Below 130 Km we find that it is possible to account for the deactivation in bright auroras by invoking large nitric oxide concentrations, similar to those recently observed mass spectrometrically and using a rate constant of 8 × 10−11 cm3 sec−1 for both the v=1 levels. This rate constant is very nearly the same as that measured in the laboratory (7 × 10−11 cm3 sec−1). Molecular oxygen appears not to play a significant role in deactivating the lower A 3 Σ u+ levels.  相似文献   

17.
Radio noise observations at frequencies of 0·700 Mc and 2·200 Mc were made at altitudes between 3000 and 11,000 km from a Blue Scout Jr. high-altitude rocket probe on 30 July 1963. A steady background flux of (7·5−3+6) × 10−19 W m−2)(c/s)−1 at 0·700 Mc and (1·8+1.0−0.5 × 10−19 W m−2 (c/s)−1 at 2·200 Mc was observed. Assuming a galactic origin of the observed fluxes at both frequencies, the averaged sky brightnesses are b(0·700 Mc) = (6−3+5) × 10−20 W m−2 (c/s)−1 sr−1b(2·200 Mc) = (1.4+1.0−0.5 × 10−20 W m−2 (c/s)−1 sr−1 The observed brightness at 2·200 Mc is in reasonable agreement with the results of other observers. The apparent brightness at 0·700 Mc is, however, greater than was expected from previous observations. An alternative source of the 0·700 Mc flux in the terrestrial exosphere, as well as characteristics of several noise bursts observed during the flight, is briefly discussed.  相似文献   

18.
The properties of energetic (65–95 keV) cometary water-group ions in the extended solar wind pick-up region surrounding comet Giacobini-Zinner are examined using data from the EPAS instrument on the ICE spacecraft. In the outer part of this region, extending from cometocentric distances of several hundred thousand to a few million kilometres (the limit of pick-up ion detectability), it is found that large modulations of the ion flux occur (with JMAX/JMIN 102-103) which are related to the direction of the magnetic field. It is also found that the ions stream in a direction which is intermediate between the directions of the solar wind flow and the E × B drift, and that ions are present at energies somewhat above the local pick-up energy. These properties indicate that the waves which are excited by the unstable “ring-beam” pick-up ion velocity distributions do result in significant scattering of the ions in this region, both in pitch angle and in energy, but that they have insufficient amplitude to scatter the ions into near isotropy in the solar wind frame. Closer to the comet (but still upstream from the bow shock), the ion flux modulations are considerably reduced in amplitude and the ions respond less to the E × B drift, indicating that the ions are scattered nearer to isotropy in this region. Inbound, this transition takes place relatively abruptly at a distance of 4 × 105 km in association with an increase in the solar wind speed, after which the ion flux increases, and ceases to be modulated by the field direction, while the streaming direction is continuously antisolar and unmodulated by the direction of the E × B drift. Outbound, weak vestiges of the ring-beam ion anisotropy are present in the region immediately upstream from the bow shock (at −1 × 105 km), but these become more marked at distances in excess of t4 × 105 km, increasing gradually with increasing distance from the comet. It is shown that the evolution of the ion properties is qualitatively consistent with expectations based on quasi-linear diffusion of the ions by the magnetosonic waves observed during the encounter.  相似文献   

19.
We present results from the initial flight of our Balloon Air CHerenkov (BACH) payload. BACH detects air Cherenkov radiation from cosmic ray nuclei as coincident flashes in two optical modules. The flight (dubbed PDQ–BACH) took place on April 22, 1998 from Ft. Sumner, New Mexico. During an exposure of 2.75 h, with a typical threshold energy for iron nuclei of 2.2×1013 eV, we observed several events cleanly identifiable as iron group nuclei. Analysis of the data yields a new flux measurement that is fully consistent with that reported by other investigations.  相似文献   

20.
On 14 July 1974 the Atmosphere Explorer-C satellite flew through an aurora at F-region altitudes just after local midnight. The effects of the particle influx are clearly evident in the ion densities, the 6300 Å airglow, and the electron and ion temperatures. This event provided an opportunity to study the agreement between the observed ion densities and those calculated from photochemical theory using in situ measurements of such atmospheric parameters as the neutral densities and the differential electron energy spectra obtained along the satellite track. Good agreement is obtained for the ions O2+, NO+ and N2+ using photochemical theory and measured rate constants and electron impact cross sections. Atomic nitrogen densities are calculated from the observed [NO+]/[O2+] ratio. In the region of most intense electron fluxes (20 erg cm−2 sec−1) at 280 km, the N density is found to be between 2 and 7 × 107 cm−3. The resulting N densities are found to account for approx. 60% of the production of N+ through electron impact on N and the resonant charge exchange of O+(2P) with N(4S). This reaction also provides a significant source of O(1S) in the aurora at F-region altitudes. In the region of intense fast electron influx, the reaction with atomic nitrogen is found to be the main loss of O+(2P).  相似文献   

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