 Subjects -> ASTRONOMY (Total: 94 journals)
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- In-field calibration of the Navigation Dosimetry System (NAVIDOS) during
solar minimum conditions
Abstract: In-field calibration of the Navigation Dosimetry System (NAVIDOS) during solar minimum conditions
T. Möller, O. Burda, S. Burmeister, B. Heber, F. Langner, and F. Wissmann
Astrophys. Space Sci. Trans., 8, 45-49, doi:10.5194/astra-8-45-2012, 2012
The NAVIgation DOsimetry System (NAVIDOS) comprises a complete readout systemfor a radiation detector, an air pressure sensor and a GPS receiver. Thedetector system DOSTEL uses silicon detectors which make NAVIDOS lightweighted and compact in size. Therefore, NAVIDOS is well suited to beinstalled on board aircraft. The calibration of NAVIDOS in terms of ambientdose equivalent is done by an in-field comparison with the PTB referenceinstrument πDOS. We also show that the dependence of these results on thevertical cut-off rigidity can be explained by the low response of the silicondetectors for neutrons. Therefore, in-flight measurements have been performedtogether with the PTB reference instrument πDOS. The dose rates,calculated using the PTB code FDOScalc, were verified with these πDOSmeasurements. The calibration of NAVIDOS was done with FDOScalc and resultsin calibration factors between 3.4 in the polar and 2.4 in the equatorregion.
PubDate: 2013-06-24T19:24:22+02:00
DOI: 10.5194/astra-8-45-2012
- Temperature effect of muon component and practical questions of how to
take into account in real time
Abstract: Temperature effect of muon component and practical questions of how to take into account in real time
M. Berkova, A. Belov, E. Eroshenko, and V. Yanke
Astrophys. Space Sci. Trans., 8, 41-44, doi:10.5194/astra-8-41-2012, 2012
A method has been developed to correct in real-time the cosmic ray (CR) muon component, observed by the muon telescopesof different geometry, for temperature effect.
PubDate: 2012-12-21T19:24:22+01:00
DOI: 10.5194/astra-8-41-2012
- Fitting Analytical forms of spatial and temporal correlation functions to
spacecraft data
Abstract: Fitting Analytical forms of spatial and temporal correlation functions to spacecraft data
A. Shalchi
Astrophys. Space Sci. Trans., 8, 35-40, doi:10.5194/astra-8-35-2012, 2012
Spacecraft missions such as Wind and ACE can be used to determine magnetic correlation functions in the solar wind.From such data sets one can obtain spatial and temporal correlations of magnetic fields. Such correlations are fundamentalin the theory of magnetic turbulence and are important to describe the statistics of magnetic field lines and thepropagation of energetic particles such as cosmic rays. In the present article we compare analytical forms of correlationfunctions with measurements performed in the solar system. We obtain new values for the correlations length scales andwe test our understanding of the turbulence dynamics.
PubDate: 2012-10-05T19:24:22+02:00
DOI: 10.5194/astra-8-35-2012
- Constraints on ultra-high-energy neutrino flux from radio observations of
the Moon
Abstract: Constraints on ultra-high-energy neutrino flux from radio observations of the Moon
S. Buitink, H. Falcke, C. James, M. Mevius, O. Scholten, K. Singh, B. Stappers, and S. ter Veen
Astrophys. Space Sci. Trans., 8, 29-33, doi:10.5194/astra-8-29-2012, 2012
The NuMoon project aims to study ultra-high-energy neutrinos and cosmic rays by using radio telescopes tosearch for short pulses from the Moon.These pulses are created when a neutrino or cosmic ray impinges on the Moon and interacts below thelunar surface. Part of the energy isconverted into a hadronic shower, which emits radio emission in a process known as the Askaryan effect. Inthe first phase of the NuMoon project, 46 hrs of data were collected with the Westerbork Synthesis RadioTelescope in a low frequency band: 40–80 MHz. This resulted in an upper limit on the neutrino flux above1022 eV which is an order of magnitude lower than previous limits. Additionally, an upper limit hasbeen set on the ultra-high-energy cosmic-ray flux. The second phase of NuMoon will consist of observationswith LOFAR.
PubDate: 2012-08-22T19:24:22+02:00
DOI: 10.5194/astra-8-29-2012
- Academician S. N. Vernov and cosmic ray variations research in the former
USSR
Abstract: Academician S. N. Vernov and cosmic ray variations research in the former USSR
L. Dorman
Astrophys. Space Sci. Trans., 8, 25-28, doi:10.5194/astra-8-25-2012, 2012
During my long scientific career of about 60 years (from 1951), I was happy to meet and cooperate with Academician S. N. Vernov. During the first step (1950–1952), S. N. Vernov together with N. V. Pushkov organized the first Soviet network of cosmic ray (CR) stations equipped by large automatically operating ionization chambers of A. Compton type shielded by 10 cm of Pb. This was the beginning of the CR variations research in the former USSR. In the present paper I consider step by step the development of experimental and theoretical basis of CR variations research in the former USSR and the great role of S. N. Vernov in this process.
PubDate: 2012-06-18T19:24:22+02:00
DOI: 10.5194/astra-8-25-2012
- A Shannon entropy approach to the temporal evolution of SEP energy
spectrum
Abstract: A Shannon entropy approach to the temporal evolution of SEP energy spectrum
M. Laurenza, G. Consolini, M. Storini, and A. Damiani
Astrophys. Space Sci. Trans., 8, 19-24, doi:10.5194/astra-8-19-2012, 2012
The kinetic energy spectra of solar energetic particle (SEP) events contain information on the particle acceleration mechanisms. A novel approach is proposed to investigate the time evolution of the spectral shape for the 20 February 2002 SEP event. Proton differential fluxes recorded by the ERNE instrument aboard SOHO, in the energy range 1.67–112 MeV, are analyzed. The solar source is associated with this SEP event by studying solar and interplanetary conditions during the considered time period. The energy spectrum evolution is studied by evaluating the time history of Shannon's differential entropy derived from the SEP fluxes. Our findings suggest that particle acceleration in the considered event is produced by a perpendicular shock in the solar corona. Moreover, dropouts in the particle flux are clearly identified up to energies of at least ~10 MeV.
PubDate: 2012-02-28T19:24:22+01:00
DOI: 10.5194/astra-8-19-2012
- Observation of solar energetic particle (SEP) events associated with
narrow CMEs
Abstract: Observation of solar energetic particle (SEP) events associated with narrow CMEs
A. Al-Sawad, H. Allawi, W. Al-Ramdhan, and E. Valtonen
Astrophys. Space Sci. Trans., 8, 1-5, doi:10.5194/astra-8-1-2012, 2012
We report here on two proton energetic particle events observed by the Energetic and Relativistic Nuclei and Electron (ERNE) instrument on the Solar and Heliospherical Observatory (SOHO). Both events were impulsive (SEP) events with intensities of >10−3 cm−2 sr−1 s−1 MeV−1 at an energy range of tens of MeVs and were associated with CMEs of angular widths 800 kms−1. In one of the events there was no associated solar flare, which indicates that the first injected protons were completely due to the associated CME and in the second event the associated solar flare was an impulsive M1.1 class flare and the calculated first injection time for protons of energies ~36 MeV and propagating along 1.2 AU path length, was close to the liftoff time of the CME. These observations are inconsistent with the view presented in some studies that narrow fast CME are not associated with SEPevents.
PubDate: 2012-01-10T19:24:22+01:00
DOI: 10.5194/astra-8-1-2012
- The effect of cosmic rays on biological systems – an investigation
during GLE events
Abstract: The effect of cosmic rays on biological systems – an investigation during GLE events
N. K. Belisheva, H. Lammer, H. K. Biernat, and E. V. Vashenuyk
Astrophys. Space Sci. Trans., 8, 7-17, doi:10.5194/astra-8-7-2012, 2012
In this study, first direct and circumstantial evidences of the effects of cosmic rays (CR) on biological systems are presented. A direct evidence of biological effects of CR is demonstrated in experiments with three cellular lines growing in culture during three events of Ground Level Enhancement (GLEs) in the neutron count rate detected by ground-based neutron monitor in October 1989. Various phenomena associated with DNA lesion on the cellular level demonstrate coherent dynamics of radiation effects in all cellular lines coincident with the time of arrival of high-energy solar particles to the near-Earth space and with the main peak in GLE. These results were obtained in the course of six separate experiments, with partial overlapping of the time of previous and subsequent experiments, which started and finished in the quiet period of solar activity (SA). A significant difference between the values of multinuclear cells in all cellular lines in the quiet period and during GLE events indicates that the cause of radiation effects in the cell cultures is an exposure of cells to the secondary solar CR near the Earth's surface. The circumstantial evidence was obtained by statistical analysis of cases of congenital malformations (CM) at two sites in the Murmansk region. The number of cases of all classes of CM reveals a significant correlation with the number of GLE events. The number of cases of CM with pronounced chromosomal abnormalities clearly correlates with the GLE events that occurred a year before the birth of a child. We have found a significant correlation between modulations of the water properties and daily background variations of CR intensity. We believe that the effects of CR on biological systems can be also mediated by fluctuations in water properties, considered as one of possible mechanisms controlling the effects of CRs on biological systems.
PubDate: 2012-01-10T19:24:22+01:00
DOI: 10.5194/astra-8-7-2012
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