| 1. |
- De Simone, N., et al.
(författare)
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Latitudinal and radial gradients of galactic cosmic ray protons in the inner heliosphere - PAMELA and Ulysses observations
- 2011
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Ingår i: Astrophysics and Space Sciences Transactions (ASTRA). - : Copernicus GmbH. - 1810-6528 .- 1810-6536. ; 7:3, s. 425-434
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Tidskriftsartikel (refereegranskat)abstract
- Ulysses, launched on 6 October 1990, was placed in an elliptical, high inclined (80.2°) orbit around the Sun, and was switched off in June 2009. It has been the only spacecraft exploring high-latitude regions of the inner heliosphere. The Kiel Electron Telescope (KET) aboard Ulysses measures electrons from 3 MeV to a few GeV and protons and helium in the energy range from 6 MeV/nucleon to above 2 GeV/nucleon. The PAMELA (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) space borne experiment was launched on 15 June 2006 and is continuously collecting data since then. The apparatus measures electrons, positrons, protons, anti-protons and heavier nuclei from about 100 MeV to several hundreds of GeV. Thus the combination of Ulysses and PAMELA measurements is ideally suited to determine the spatial gradients during the extended minimum of solar cycle 23. For protons in the rigidity interval 1.6-1.8 GV we find a radial gradient of 2.7%/AU and a latitudinal gradient of -0.024%/degree. Although the latitudinal gradient is as expected negative, its value is much smaller than predicted by current particle propagation models. This result is of relevance for the study of propagation parameters in the inner heliosphere.
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| 2. |
- Ota, S., et al.
(författare)
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Improvement of charge resolution for trans-iron nuclei (Z≥30) in CR-39 plastic nuclear track detectors using trajectory tracing technique
- 2011
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Ingår i: Astrophysics and Space Sciences Transactions. - : Copernicus GmbH. - 1810-6528 .- 1810-6536. ; 7:4, s. 495-500
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Tidskriftsartikel (refereegranskat)abstract
- Charge identification of trans-iron nuclei (nuclear charge: Z≥ 30) using CR-39 plastic nuclear track detector (PNTD) is essential as a part of an effort to our future measurements of the projectile charge changing cross sections for galactic cosmic ray nuclei, but extremely hard. Therefore, an improvement method of the charge resolution (δZ) for 350 MeV/n Ge in CR-39 PNTD using the trajectory tracing technique with averaging the signals of nuclear tracks for each ion was studied. Eight sheets of CR-39 PNTDs were aligned and exposed to Ge beam behind a graphite target to produce projectile fragments. Average of the nuclear track data was taken over 16 detector surfaces for each ion, then the δZ of Ge was successfully improved from 0.31 charge unit on single surface to 0.15 charge unit in rms, which is good enough for making the precise cross section measurements and no other experiments using CR-39 PNTDs or the other passive detectors have achieved such a good δZ for the trans-iron nuclei with ≥Z 50 (β: relativistic velocity). This method will be very important for our future cross section measurements toward the study of galactic cosmic ray origin. © 2011 Author(s).
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| 3. |
- Thoudam, Satyendra, et al.
(författare)
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An air shower array for LOFAR : LORA
- 2011
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Ingår i: Astrophysics and Space Sciences Transactions (ASTRA). - : Copernicus GmbH. - 1810-6528 .- 1810-6536. ; 7, s. 195-199
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Tidskriftsartikel (refereegranskat)abstract
- LOFAR is a new form of radio telescope which can detect radio emission from air showers induced by very high-energy cosmic rays. It can also look for radio emission from particle cascades on the Moon induced by ultra high-energy cosmic rays or neutrinos. To complement the radio detection, we are setting up a small particle detector array LORA (LOfar Radboud Air shower array) within an area of ~300 m diameter in the LOFAR core. It will help in triggering and confirming the radio detection of air showers with the LOFAR antennas. In this paper, we present a short overview about LORA and discuss its current status.
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| 4. |
- Wu, Juan
(författare)
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Measurements of cosmic-ray antiprotons with PAMELA
- 2011
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Ingår i: Astrophysics and Space Sciences Transactions (ASTRA). - : Copernicus Publications. - 1810-6528 .- 1810-6536. ; 7:2, s. 225-228
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Tidskriftsartikel (refereegranskat)abstract
- The PAMELA experiment is a satellite-borne apparatus designed to study charged particles, and especially antiparticles, in the cosmic radiation. The apparatus is mounted on the Resurs DK1 satellite which was launched on 15 June 2006. PAMELA has been traveling around the earth along an elliptical and semi-polar orbit for almost five years. It mainly consists of a permanent magnetic spectrometer, a time of flight system and an electromagnetic imaging calorimeter, which allows antiprotons to be identified from a dominating cosmic-ray background. New measurements of the cosmic-ray antiproton flux and the antiproton-to-proton flux ratio between 60 MeV and 180 GeV are presented, employing data collected between June 2006 and December 2008. Compared to previous experiments, PAMELA extends the energy range of antiproton measurements and provides significantly higher statistics. The derived antiproton flux and antiproton-to-proton flux ratio indicates that the main source of cosmic-ray antiprotons is considered to be secondary production and no primary contribution has to be invoked.
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| 5. |
- Muscheler, R., et al.
(författare)
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Constraints on long-term changes in solar activity from the range of variability of cosmogenic radionuclide records
- 2011
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Ingår i: Astrophys. Space Sci. Trans.. - : Copernicus GmbH. - 1810-6536. ; 7:3, s. 355-364
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Tidskriftsartikel (refereegranskat)abstract
- There is a variety of different cosmogenicradionuclide-based reconstructions of solar activity varia-tions for the past. Especially the longer-term changes andthe absolute levels of past solar activity are uncertain as it isillustrated by the differences between these reconstructions.On the one hand there are differences between10Be and14Crecords that are commonly used as proxies for the varying so-lar modulation of galactic cosmic rays. On the other hand es-timates of past changes in the geomagnetic shielding also in-clude relatively large uncertainties. Here, we concentrate onvariations in cosmogenic radionuclide records on time scalesof 50 to 500 yr. We show that these are to a large extentindependent of the geomagnetic field intensity. The rangeof variability of cosmogenic radionuclide records allows usto set constraints about long-term changes in solar activity.These records indicate that present solar activity levels werereached or exceeded regularly in the past
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