Cosmic Rays In Atmosphere Research Articles

Cosmic ray induced ionization model CRAC:CRII: An extension to the upper atmosphere

A new version of the CRAC:CRII model computing ionization induced by cosmic rays in the atmosphere is presented, which is extended to the upper atmosphere and can be now applied to the entire atmosphere. The model is able to compute the ionization rate in the atmosphere at any given location and time provided the energy spectrum of incoming cosmic rays is known. It is discussed that the use of earlier models, either analytical or Monte Carlo, with the limited upper energy of 500 MeV, is well validated for the upper atmosphere (above a few g/cm2 atmospheric depth, which corresponds to the altitude about 40 km) to study the effect of solar energetic particles but may lead to a significant underestimate of the background ionization due to galactic cosmic rays. The use of a full model accounting for the atmospheric cascade and full energy range of incoming cosmic rays, rather than earlier simplified models, is recommended to study the ionization effects of galactic cosmic rays in the upper atmosphere. On the other hand, transient strong effects of solar energetic particle events can be studied using truncated models.

Calibration and characterization of the IceCube photomultiplier tube

Over 5000 PMTs are being deployed at the South Pole to compose the IceCube neutrino observatory. Many are placed deep in the ice to detect Cherenkov light emitted by the products of high-energy neutrino interactions, and others are frozen into tanks on the surface to detect particles from atmospheric cosmic ray showers. IceCube is using the 10-in. diameter R7081-02 made by Hamamatsu Photonics. This paper describes the laboratory characterization and calibration of these PMTs before deployment. PMTs were illuminated with pulses ranging from single photons to saturation level. Parameterizations are given for the single photoelectron charge spectrum and the saturation behavior. Time resolution, late pulses and afterpulses are characterized. Because the PMTs are relatively large, the cathode sensitivity uniformity was measured. The absolute photon detection efficiency was calibrated using Rayleigh-scattered photons from a nitrogen laser. Measured characteristics are discussed in the context of their relevance to IceCube event reconstruction and simulation efforts.

A new 3D numerical model of cosmogenic nuclide 10Be production in the atmosphere

A new quantitative model of production of the cosmogenic isotope 10Be by cosmic rays in the Earth's atmosphere is presented. The CRAC:10Be (Cosmic Ray induced Atmospheric Cascade for 10Be) model is based on a full numerical Monte-Carlo simulation of the nucleonic–electromagnetic–muon cascade induced by cosmic rays in the atmosphere and is able to compute the isotope's production rate at any given 3D location (geographical and altitude) and time, for all possible parameters including solar energetic particle events. The model was tested against the results of direct measurements of the 10Be production in a number of dedicated experiments to confirm its quantitative correctness. A set of tabulated values for the yield function is provided along with a detailed numerical recipe forming a “do-it-yourself” kit, which allows anyone interested to apply the model for any given conditions. This provides a useful tool for applying the cosmogenic isotope method in direct integration with other models, e.g., dynamical atmospheric transport.

GEANT4 Simulation of a Cosmic Ray Muon Tomography System With Micro-Pattern Gas Detectors for the Detection of High-${\rm Z}$ Materials

Muon tomography (MT) based on the measurement of multiple scattering of atmospheric cosmic ray muons traversing shipping containers is a promising candidate for identifying threatening high-Z materials. Since position-sensitive detectors with high spatial resolution should be particularly suited for tracking muons in a MT application, we propose to use compact micro-pattern gas detectors, such as gas electron multipliers (GEMs), for muon tomography. We present a detailed GEANT4 simulation of a GEM-based MT station for various scenarios of threat material detection. Cosmic ray muon tracks crossing the material are reconstructed with a point-of-closest-approach algorithm to form 3-D tomographic images of the target material. We investigate acceptance, Z-discrimination capability, effects of placement of high-Z material and shielding materials inside the cargo, and detector resolution effects for such a MT station.

Measurements of the atmospheric radiation environment from CREAM and comparisons with models for quiet time and solar particle events

Flight data on neutron fluxes and dose rates obtained over a wide range of latitudes and altitudes are compared with several models of atmospheric radiation for both quiet-time and solar particle events. For quiet-time, general agreement between the models and measurements is within about 25%. Geomagnetic disturbances can increase atmospheric cosmic ray fluxes by up to 10% due to suppression of cut-off rigidities. Solar particle events are more difficult to model but for this solar maximum reasonable agreement has been obtained with a measurement during the event of 15 April 2001. On 20 January 2005 the second largest ground level event in recorded history could have raised atmospheric fluxes at flight altitudes by several hundredfold at high southern latitudes.

The Search for Supernova Signatures in an Ice Core

It has been suggested that ice cores may preserve detectable enhancements of some terrestrially rare radioisotopes, 10Be, 26Al, 36Cl, resulting from a near-Earth core-collapse supernova(SN) [J. Ellis, B.D. Fields and D.N. Schramm, Astrophys. J. 470 (1996) 1227]. Both 10Be and 36Cl are also produced by atmospheric cosmic ray spallation and hence are influenced by processes that modulate the Earth's cosmic ray flux. Previous studies [G.M. Raisbeck, F. Yiou, D. Bourles, C. Lorius, J. Jouzel and N. I. Barkov, Nature 326 (1987) 273], [L.G. Thompson, T. Yao, M.E. Davis, K.A. Henderson, E. Mosley-Thompson, P.-N. Lin, J. Beer, H.-A. Synal, J. Cole-Dai and J.F. Bolzan, Science 276 (1997) 1821] have suggested that enhancements occurred in the 10Be and 36Cl fluxes at ∼35 ky and at ∼60 ky for 10Be. Thus we have searched for potential SN condensates with 26Al amongst grains filtered from the 308.6m Guliya ice core recovered from the Qinghai-Tibetan plateau in China [L.G. Thompson, T. Yao, M.E. Davis, K.A. Henderson, E. Mosley-Thompson, P.-N. Lin, J. Beer, H.-A. Synal, J. Cole-Dai and J.F. Bolzan, Science 276 (1997) 1821]. We searched for potential core-collapse SN condensate grains corundum (Al2O3), hibonite (CaAl12O19) and spinel (MgAl2O4) (see [D.S. Ebel and L. Grossman, Geochim. Cosmochim. Acta 65 (2001) 469]) in Guliya grain samples from the following time periods: ∼2−10 ky, ∼25−27 ky, ∼34−36 ky, ∼53−57 ky, ∼59−62 ky and ∼68−72 ky. These minerals are rare among terrestrial rocks and fine-grained atmospheric dust of terrestrial origin. Furthermore, they are insoluble in the acids employed in the sample preparation process and therefore separable from other minerals, such as silicates, that have high terrestrial abundances. Candidate SN condensate grains were identified among their terrestrial diluents employing a procedure developed at the University of Chicago for detecting presolar grains in meteoritic samples [S. Amari, R.S. Lewis and E. Anders, Geochim. Cosmochim. Acta 58 (1994) 459]. A set of 37 grains from the ∼34−36 ky, ∼53−57 ky and ∼59−62 ky samples were analyzed with the NanoSIMS at Washington University to measure their oxygen isotopic ratios. The preliminary results indicate that the analyzed grains, representing < 15% of those identified, do not possess the extreme O isotopic ratios expected to characterize a SN source [S. Amari and E. Zinner, Nucl. Phys. A 621 (1997) 99c], [T. Rauscher, A. Heger, R.D. Hoffman and S.E. Woosley, Astrophys. J. 576 (2002) 323].

OSCILLATION INVESTIGATIONS IN SOUDAN 2: ATMOSPHERIC νμ → ντ AND ${\rm n} \to \bar{n}$ IN IRON

The 5.90 fiducial kiloton-year exposure of the Soudan-2 iron tracking calorimeter is analyzed for effects of neutrino oscillations. Using fully contained single track, single shower and multiprong events, we determine the atmospheric νμ/νe ratio-of-ratios in the sub-GeV Eν regime to be R=0.68±0.12±0.06. Assuming this anomalously low R-value to be the result of νμ flavor disappearance via νμ → ντ oscillation, we distribute fully contained and partially contained events into bins of log (L/Eν) and fit to oscillation hypotheses using extended maximum likelihood. The region in the ( sin 22θ, Δm2) plane allowed at 90% CL is obtained using the Feldman-Cousins procedure: 0.52&lt; sin 2 2θ≤1.0 and 3×10-4&lt;Δm2&lt;2×10-2 eV 2. A different oscillation process which could occur in our contained event samples is baryon instability in the form of neutron-antineutron oscillations. Our search requires candidate [Formula: see text] occurrences to have ≥ 4 prongs (tracks and showers) and to have kinematics compatible with [Formula: see text] annihilation within a nucleus. We observe five candidate events, with estimated atmospheric neutrino plus cosmic ray backgrounds totalling 4.5 ± 1.2 events. Previous experiments with smaller exposures observed no candidates, with estimated background rates similar to this experiment. We set a lifetime lower limit at 90% CL for the [Formula: see text] oscillation time in iron: TA(Fe)&gt;7.2×1031 years. The corresponding lower limit for oscillation of free neutrons is [Formula: see text] seconds.

The atmospheric cosmic- and solar energetic particle radiation environment at aircraft altitudes

Galactic cosmic rays interact with the solar wind, the earth's magnetic field and its atmosphere to produce hadron, lepton and photon fields at aircraft altitudes. In addition to cosmic rays, energetic particles generated by solar activity bombard the earth from time to time. These particles, while less energetic than cosmic rays, also produce radiation fields at aircraft altitudes which have qualitatively the same properties as atmospheric cosmic rays. We have used a code based on transport theory to calculate atmospheric cosmic-ray quantities and compared them with experimental data. Agreement with these data is seen to be good. We have then used this code to calculate equivalent doses to aircraft crews. We have also used the code to calculate radiation doses from several large solar energetic particle events which took place in 1989, including the very large event that occurred on September 29 th and 30 th of that year. The spectra incident on the atmosphere were determined assuming diffusive shock theory.

Atmospheric cosmic rays and solar energetic particles at aircraft altitudes

Galactic cosmic rays, which are thought to be produced and accelerated by a variety of mechanisms in the Milky Way galaxy, interact with the solar wind, the earth's magnetic field, and its atmosphere to produce hadron, lepton, and photon fields at aircraft altitudes that are quite unlike anything produced in the laboratory. The energy spectra of these secondary particles extend from the lowest possible energy to energies over an EeV. In addition to cosmic rays, energetic particles, generated on the sun by solar flares or coronal mass ejections, bombard the earth from time to time. These particles, while less energetic than cosmic rays, also produce radiation fields at aircraft altitudes which have qualitatively the same properties as cosmic rays. The authors have calculated atmospheric cosmic-ray angular fluxes, spectra, scalar fluxes, and ionization, and compared them with experimental data. Agreement with these data is seen to be good. These data have been used to calculate equivalent doses in a simplified human phantom at aircraft altitudes and the estimated health risks to aircraft crews. The authors have also calculated the radiation doses from several large solar energetic particle events (known as GLEs, or Ground Level Events), which took place in 1989, including the very large event known as GLE 42, which took place on September 29th and 30th of that year. The spectra incident on the atmosphere were determined assuming diffusive shock theory. Unfortunately, there are essentially no experimental data with which to compare these calculations.

Atmospheric cosmic rays at aircraft altitudes

Galactic cosmic rays produced by some as yet unknown mechanism in the Milky Way galaxy interact with the solar wind, the earth's magnetic field, and its atmosphere to produce hadron, lepton, and photon fields at aircraft altitudes that are quite unlike anything produced in the laboratory. The energy spectra of these secondary particles extend from the lowest possible energy to energies over an EeV. The authors have calculated atmospheric cosmic-ray angular fluxes, spectra, scalar fluxes, and ionization and have compared them with experimental data. Agreement with these data was seen to be good. The authors also calculated doses equivalent in a simplified human phantom at aircraft altitudes and estimated health risks to aircraft crews.

Atmospheric cosmic rays in the South Atlantic anomaly region

To study the production and propagation of fast secondaries particles in the atmosphere, data collected during eleven quiet-time balloon flights are analysed. Comparisons of these data with those obtained in different geomagnetic rigidity regions permit to estimate the contributions of the proton and electron components in the measured intensities. Derivations of this last component in the «upward» and «downward» moving electrons fluxes indicate that in the anomaly region a fraction of these particles, produced by the primary protons, are leaving the atmosphere and will not return to the Earth.

Observation of SN1987A by neutrino light

On the 54th day of 1987 an event occurred on Earth which gave reality to the fifty-five year old dreams of Baade, Zwicky, and Landauan event which confirmed thoughts of Chandrasekhar and Bethe. Also confirmed were the computer-based calculations of Colgate, Arnett, Burrows, Lattimer, Weaver, Woosley, Wilson and many others. The event was the arrival of a neutrino pulse that had been rushing towards the Earth for 170 000 yr. Had it arrived a few years earlier it would have gone unrecorded. Had its source in the Large Magellanic Cloud been much further away, it would have been too feeble to see. ~1016 neutrinos passed through the IMB detector (in the United States) in a few seconds. Only eight made recorded interactions. Simultaneously the Kamiokande detector (in Japan) recorded eleven. These numbers are in remarkable accord with the expectations of the above thinkers. It is a masterful triumph of the human intellect. Such pulses may pass our way every 10-100 years. *~ The chance that any more will be recorded may not be high since it requires the maintenance of large, complex detectors over these very long time periods. The detectors which recorded these events consisted of large masses of water viewed by many photomultiplier tubes located deep underground. **~ The events seen in the detectors are, individually, not very spectacular. In the IMB detector, for example, they have energies of only 20-40 MeV, close to that detector's threshold of visibility. An electron of 20 MeV will only light up approximately two dozen of the detector's 2048 phototubes. Such a signal must be picked out from a background due to radioactivity, electronic noise, and neutrino interactions from the atmospheric cosmic ray background. By appropriate filtering one can reduce the data to the cosmic ray neutrino rate, which is about two events per week in the 20-50 MeV energy band. A pulse of eight such events in six seconds is, therefore, truly extraordinary. This is what was recorded by IMB and similarly by a sequence of pulses in Kamiokande on February 23, many powers of ten above that expected from statistical fluctuations in the neutrino background.

Interstellar shock waves and 10Be from ice cores

The anomalously high concentrations of 10Be in Antarctic ice cores1,2, uncorrelated with δ18O, are consistent with an increase in the atmospheric cosmic ray (CR) flux from CR acceleration in propagating interstellar shock waves, which envelop the heliosphere and whose source may be ancient supernovas. This mechanism is an alternative to the model where decreases in geomagnetic field intensity, associated with geomagnetic reversals, periodically enhance the CR flux at the top of the atmosphere. That CR variations attributable to interstellar events such as supernova shock waves have so far not been observed in the CR record is a long-standing issue3–5. If our interpretation of the 10Be spikes is correct, it marks the first such observation. The possibility that 'direct' observation of the interstellar medium can be made using the 10Be record would be an important adjunct to the study of cosmic rays in the interstellar medium.

Primary cosmic-ray composition in the energy range of 1014 eV to 1016 eV and high-energy atmospheric cosmic rays observed with emulsion chambers at Mt. Kanbala

We report on the results of the measurements of energy spectra of atmospheric cosmic rays in the energy around 10 TeV measured with emulsion chambers at Mt. Kanbala (5500 m above sea-level, atmospheric depth 520 g/cm2). The power indices of the integral spectra take the values of 2.00±0.08 for gamma-rays and 1.90±0.10 for hadrons, in the energy range from 5 TeV to 20 TeV. Their intensities are compatible with those expected from the primary cosmic rays containing fewer protons than in the lower energy region. The energy spectrum of family events is also discussed with reference to the composition of primary cosmic rays. It is concluded that the portion of protons in the primary cosmic rays gradually decreases in the energy range from 1013 eV to 1015 eV.

Energy spectra of atmospheric cosmic rays observed with emulsion chambers

The energy spectra of gamma-rays, hadrons and muons in the atmosphere are summarized on the basis of the emulsion chamber experiments at Mt. Fuji and underground. The power indices of the spectra are 1.95±0.05 for gamma-rays and 1.80±0.07 for hadrons at Mt. Fuji in the energy range from 2 TeV to 50 TeV. The underground measurements have confirmed the muon spectrum at sea-level with the index of 2.70±0.10 in the range from 1 TeV to 10 TeV. These spectra of atmospheric cosmic rays are not explained simultaneously on the basis of the concept of scaling so long as the primary spectrum with the normal composition holds up to 1015eV.

Development of Atmospheric Cosmicray Showers

Development of Atmospheric Cosmicray Showers

Beryllium-7 production from oxygen by atmospheric cosmic rays

The production rates of 7Be from 16O by cosmic rays were measured at three locations of different latitudes and altitudes. From the altitude dependence of the production rates, the attenuation length of L =165 ± 30g/cm2 was obtained. This value falls in the range of the reported values obtained by physical methods for the atmospheric neutrons. The experimental value at the sea level of the geomagnetic latitude, X = 25°N, was in good agreement with the value calculated from the generally accepted atmospheric neutron spectrum and the best estimated excitation function. The latitude effect on the production rate is also discussed.

Cosmic-ray propagation in the atmosphere

An essentially analytical theory of atmospheric cosmic-ray propagation is developed on the basis of a phenomenological model of hadron-nucleus collisions. This model correctly predicts the sea-level cosmic-ray nucleon, pion and muon spectra, the cosmic-ray ionization profile in the atmosphere, and neutron flux and density profiles in the atmosphere. It is concluded that the large-scale properties of atmospheric cosmic rays can be accurately predicted on the basis of a purely nucleonic cascade as a result of which all secondaries are mediated by pion production. Implications for energy independence of cross-sections, the recent 70 GeV results from Serpukhov, and nucleonic relaxation rates in the atmosphere are discussed.

Phosphorus-32 induced by atmospheric cosmic rays in laboratory chemicals

The production rates of 32P in rhombic sulfur were measured at various altitudes from sea level up to the top of Mt. Fuji. The production rate decreases exponentially with increasing atmospheric depth and the dependence indicates that neutron reaction is predominant in the 32P production. From an underground experiment, the contribution of muons to the production of 32P was estimated and the result was compared with relevant data.

The Hard Component of Cosmic Rays in the Upper Atmosphere

An experiment has been performed in the upper atmosphere to study charged cosmic-ray particles that penetrate 20 cm of lead. These particles were divided into two groups depending on whether or not they interacted on traversing the lead. The experimental equipment, which consisted of the lead absorber, G---M tubes in coincidence, and radio telemetering devices, was carried to high altitudes by an array of 36 balloons. The rate of occurrence of particles in the two groups was determined as a function of atmospheric depth from 16 g-${\mathrm{cm}}^{\ensuremath{-}2}$ to 400 g-${\mathrm{cm}}^{\ensuremath{-}2}$. The experimental results can be interpreted in terms of high energy protons and $\ensuremath{\mu}$-mesons, with corrections for low energy protons and primary alpha-particles. The results are consistent with a primary proton intensity equal to 0.19 ${\mathrm{cm}}^{\ensuremath{-}2}$ ${\mathrm{sec}}^{\ensuremath{-}1}$ ${\mathrm{sterad}}^{\ensuremath{-}1}$, an absorption length in air of 110 g-${\mathrm{cm}}^{\ensuremath{-}2}$ for high energy protons, and the $\ensuremath{\mu}$-meson production spectrum given by Sands.