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Results for “COSMIC RAYS”

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PubMed1994

Radiation environment due to galactic and solar cosmic rays during manned mission to Mars in the periods between maximum and minimum solar activity cycles.

A possibility of a manned mission to Mars without exceeding the current radiation standards is very doubtful during the periods of minimum solar activity since the dose equivalent due to galactic cosmic rays exceeds currently recommended standards even inside a radiation shelter with an equivalent of 30 g cm-2 aluminum. The radiation situation at the time of maximum solar activity is determined by the occurrence of major solar proton events which are exceedingly difficult to forecast. This paper discusses the radiation environment during a manned mission to Mars in the years between minimum and maximum solar activity when the galactic cosmic ray intensity is considerably reduced, but the solar flare activity has not yet maximized.

Cosmic Radiation↗
PubMed2005

High-density QCD and cosmic-ray air showers.

We discuss particle production in the high-energy, small-x limit of QCD where the gluon density of hadrons is expected to become nonperturbatively large. Strong modifications of the phase-space distribution of produced particles as compared to leading-twist models are predicted, which reflect in the properties of cosmic-ray induced air showers in the atmosphere. Assuming hadronic primaries, our results suggest a light composition near Greisen-Zatsepin-Kuzmin cutoff energies. We also show that cosmic-ray data are sensitive to various QCD evolution scenarios for the rate of increase of the gluon density at small x, such as fixed-coupling and running-coupling Balitsky-Fadin-Kuraev-Lipatov evolution. There are clear indications for a slower growth of the gluon density as compared to RHIC and HERA, due, e.g., to running-coupling effects.

Journal Article↗
PubMed2000

Low-Energy Anomalous Cosmic Rays in the Ecliptic Plane: 1-5 AU.

Anomalous cosmic-ray (ACR) oxygen (O) fluxes in the energy range 0.5-5.0 MeV nucleon-1 were measured in the ecliptic plane at 1 and 5 AU in 1997 and 1998. Using measurements from essentially identical instruments on the Advanced Composition Explorer (ACE) and Ulysses spacecraft, we were able to monitor the decrease with time of the ACR O fluxes in the inner heliosphere during the onset of solar cycle 23. The data obtained from three time intervals that are relatively undisturbed by solar activity during this period show that the e-folding time is approximately 140+/-40 days for the disappearance of 2-5 MeV nucleon-1 ACR oxygen from the ecliptic plane at 5 AU.

Journal Article↗
PubMed2003

Strangelets as cosmic rays beyond the Greisen-Zatsepin-Kuzmin cutoff.

Strangelets (stable lumps of quark matter) can have masses and charges much higher than those of nuclei, but have very low charge-to-mass ratios. This is confirmed in a relativistic Thomas-Fermi model. The high charge allows astrophysical strangelet acceleration to energies orders of magnitude higher than for protons. In addition, strangelets are much less susceptible to the interactions with the cosmic microwave background that suppress the flux of cosmic ray protons and nuclei above energies of 10(19)-10(20) eV (the Greisen-Zatsepin-Kuzmin cutoff). This makes strangelets an interesting possibility for explaining ultrahigh energy cosmic rays.

Journal Article↗
PubMed2004

Detectors/Dosemeters of galactic and solar cosmic rays.

Different passive multidetector stacks have been developed at the Italian National Agency for Environmental Protection (ANPA-stack), which makes it possible to measure directly ionising radiations, low-energy and high-energy neutrons, and high-energy charged (HZE) particles. The stack consists of several types of passive devices, namely recoil-track and fission-track detectors, bubble detectors, thermoluminescence dosemeters and an electronic personal dosemeter. Most of these detectors have been used on earth for the assessment of the occupational exposure, or in outer space for cosmic ray physics and/or for the assessment of the dose received by astronauts. A great deal of efforts and new developments have been required to make these detectors useful for in-flight measurements. As outcome of these extensive efforts, different new detectors have been developed, which exploit some of the most successful principles of radiation detection, such as the use of avalanche processes to facilitate the registration of nuclear tracks and the use of coincidence-counting to increase the signal-to-noise ratio. On the basis of these new detectors, different systems (generally referred to as ANPA-stack) have been obtained, which have been successfully applied for a variety of different measurements of cosmic ray radiation fields and doses.

Cosmic Radiation↗
PubMed1978

Cosmic ray effects on the eyes of rats flown on Cosmos No. 782, experimental K-007.

The eyes from six rats were fixed at the recovery site in Russia after they had circled the earth for 19.5 d in a 62.8 degree orbit. The eyes of six more flight rats were fixed 25 d later. These two preparations and eyes exposed to 1000 rad of neon and argon were compared to obtain data on possible radiation effects on the retina. Most of the flight eye tissue was normal; however, necrotic nuclei were found in the outer nuclear layer and channels were located in the outer segment area. Macrophages were seen between the pigment layer and outer segments. Comparison of the Day zero znd 25-d postflight eyes suggested some possible recovery. Light flashes seen by space travelers and damage from cosmic rays appear to arise from two different sites of interaction. The flashes are created by cosmic ray transversal of the outer segments while pathologic change, when it occurs, is quite possibly from interaction with some part of the nucleus. Nevertheless, direct interaction with other cellular components could also occur. Other factors, such as secondaries from spacecraft shielding, may play an important role.

Animals↗
PubMed2005

Chromosome aberration and environmental physical activity: Down syndrome and solar and cosmic ray activity, Israel, 1990-2000.

The possibility that environmental effects are associated with chromosome aberrations and various congenital pathologies has been discussed previously. Recent advances in the collection and computerization of data make studying these potential associations more feasible. The aim of this study was to investigate a possible link between the number of Down syndrome (DS) cases detected prenatally or at birth yearly in Israel over a 10-year period compared with the levels of solar and cosmic ray activity 1 year before the detection or birth of each affected child. Information about 1,108,449 births was collected for the years 1990-2000, excluding 1991, when data were unavailable. A total of 1,310 cases of DS were detected prenatally or at birth--138 in the non-Jewish community and 1,172 in the Jewish population. Solar activity indices--sunspot number and solar radio flux 2,800 MHz at 10.7 cm wavelength for 1989-1999--were compared with the number of DS cases detected. Pearson correlation coefficients (r) and their probabilities (P) were established for the percentage of DS cases in the whole population. There was a significant inverse correlation between the indices of solar activity and the number of cases of DS detected--r=-0.78, P=0.008 for sunspot number and r=-0.76, P=0.01 for solar flux. The possibility that cosmophysical factors inversely related to solar activity play a role in the pathogenesis of chromosome aberrations should be considered. We have confirmed a strong trend towards an association between the cosmic ray activity level and the incidence of DS.

Chromosome Aberrations↗
PubMed1986

Some methodological aspects of estimating cosmic ray exposures in orbital flights.

Computations of the transmission functions of cosmic rays penetrating the geomagnetic field are discussed. Results of LET spectra calculations both inside and outside the spacecraft COSMOS-1129 are presented. Comparison of calculations and measured results shows (in interval 10-5 x 10(3) MeV/cm) a difference of less than 30%. The need for further systematic low altitude particle measurements for the purpose of developing dynamic models of particle populations is stressed.

Cosmic Radiation↗
PubMed1992

Galactic cosmic ray transport methods and radiation quality issues.

An overview of galactic cosmic ray (GCR) interaction and transport methods, as implemented in the Langley Research Center GCR transport code, is presented. Representative results for solar minimum, exo-magnetospheric GCR dose equivalents in water are presented on a component by component basis for various thicknesses of aluminum shielding. The impact of proposed changes to the currently used quality factors on exposure estimates and shielding requirements are quantified. Using the cellular track model of Katz, estimates of relative biological effectiveness (RBE) for the mixed GCR radiation fields are also made.

Animals↗
PubMed1994

A model of galactic cosmic rays for use in calculating linear energy transfer spectra.

The galactic cosmic rays (GCR) contain fully stripped nuclei, from Hydrogen to beyond the Iron group, accelerated to high energies and are a major component of the background radiation encountered by satellites and interplanetary spacecraft. This paper presents a GCR model which is based upon our current understanding of the astrophysics of GCR transport through interstellar and interplanetary space. The model can be used to predict the energy spectra for all stable and long-lived radioactive species from H to Ni over an energy range from 50 to 50,000 MeV/nucleon as a function of a single parameter, the solar modulation level phi. The details of this model are summarized, phi is derived for the period 1974 to present, and results from this model during the 1990/1991 CRRES mission are presented.

Cosmic Radiation↗
PubMed2002

Neutrino cross sections and future observations of ultrahigh-energy cosmic rays.

We show that future detectors of ultrahigh-energy cosmic-ray neutrinos will be able to measure neutrino-nucleon cross section, sigma(nu N), at energies as high as 10(11) GeV or higher. We find that the flux of upgoing charged leptons per unit surface area produced by neutrino interactions below the surface is inversely proportional to sigma(nu N). This contrasts with the rate of horizontal air showers (HAS) due to neutrino interactions in the atmosphere, which is proportional to sigma(nu N). Thus, by comparing the HAS and upgoing air shower rates, the neutrino-nucleon cross section can be inferred. Taken together, upgoing and horizontal rates ensure a healthy total event rate, regardless of the value of sigma(nu N).

Journal Article↗
PubMed1999

Contribution of cosmic ray heavy ions to the radiation hazard in manned space flights.

Primary cosmic radiation arriving near the Earth may be classified into two general categories: the gamma component and the hadronic component. The hadronic component contains mainly protons, a small amount of alpha particles and a smaller amount of heavier charged nuclei (ions). Although the fluxes of these heavier ions are very small in comparison to those of protons, they are able to originate a huge linear energy transfer (LET). This work studies the contribution of heavy ions from cosmic rays to the radiation hazard to which the crew of a manned long duration space flight might be exposed. The geometry of the energy deposition by a heavy ion is studied, and it is found that energies of the order of up to 10(23) J kg-1 are deposited.

Cosmic Radiation↗
PubMed2003

Multiscaling of galactic cosmic ray flux.

Multiscaling analysis of the differential flux dissipation rate of galactic cosmic rays (carbon nuclei) is performed in the energy ranges 56.3-73.4 MeV/nucleon and 183.1-198.7 MeV/nucleon, using the data collected by the ACE/CRIS spacecraft instrument for the year 2000. The analysis reveals strong (turbulencelike) intermittency of the flux dissipation rate for short-term intervals: 1-30 h. It is also found that the type of intermittency can be different in different energy ranges.

Anisotropy↗
PubMed2000

Statistics of clustering of ultrahigh energy cosmic rays and the number of their sources.

Observation of clustering of ultrahigh energy cosmic rays (UHECR) suggests that they are emitted by compact sources. Assuming small ( <3 degrees ) deflection of UHECR during the propagation, the statistical analysis of clustering allows an estimate of the spatial density of the sources h(*), including those not yet observed. When applied to astrophysical models involving extragalactic sources, the estimate based on 14 events with energy E>10(20) eV gives h(*) approximately 6x10(-3) Mpc(-3). With increasing statistics, this estimate may lead to exclusion of some models.

Astronomical Phenomena↗