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1.
  • Adriani, O., et al. (författare)
  • A statistical procedure for the identification of positrons in the PAMELA experiment
  • 2010
  • Ingår i: Astroparticle physics. - : Elsevier BV. - 0927-6505 .- 1873-2852. ; 34:1, s. 1-11
  • Tidskriftsartikel (refereegranskat)abstract
    • The PAMELA satellite experiment has measured the cosmic-ray positron fraction between 1.5 GeV and 100 GeV. The need to reliably discriminate between the positron signal and proton background has required the development of an ad hoc analysis procedure. In this paper, a method for positron identification is described and its stability and capability to yield a correct background estimate is shown. The analysis includes new experimental data, the application of three different fitting techniques for the background sample and an estimate of systematic uncertainties due to possible inaccuracies in the background selection. The new experimental results confirm both solar modulation effects on cosmic-rays with low rigidities and an anomalous positron abundance above 10 GeV. (c) 2010 Elsevier B.V. All rights reserved.
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2.
  • Adriani, O., et al. (författare)
  • Latest results from the Pamela experiment
  • 2009
  • Ingår i: Proceedings of Science. ; , s. 1-6
  • Konferensbidrag (refereegranskat)abstract
    • In this paper we present the latest results of the Pamela satellite experiment, focusing in particular on the p̄/p and the e +/(e+ +e-) ratios.
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3.
  • Adriani, O., et al. (författare)
  • Measurement of the flux of primary cosmic ray antiprotons with energies of 60 MeV to 350 GeV in the PAMELA experiment
  • 2013
  • Ingår i: JETP Letters. - 0021-3640 .- 1090-6487. ; 96:10, s. 621-627
  • Tidskriftsartikel (refereegranskat)abstract
    • It is interesting to measure the antiproton galactic component in cosmic rays in order to study the mechanisms by which particles and antiparticles are generated and propagate in the Galaxy and to search for new sources of, e.g., annihilation or decay of dark matter hypothetical particles. The antiproton spectrum and the ratio of the fluxes of primary cosmic ray antiprotons to protons with energies of 60 MeV to 350 GeV found from the data obtained from June 2006 to January 2010 in the PAMELA experiment are presented. The usage of the advanced data processing method based on the data classification mathematical model made it possible to increase statistics and analyze the region of higher energies than in the earlier works.
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4.
  • Bongi, M, et al. (författare)
  • PAMELA : A satellite experiment for antiparticles measurement in cosmic rays
  • 2004
  • Ingår i: IEEE Transactions on Nuclear Science. - 0018-9499 .- 1558-1578. ; 51:3, s. 854-859
  • Tidskriftsartikel (refereegranskat)abstract
    • PAMELA is a satellite-borne experiment that will study the antiproton and positron fluxes in cosmic rays in a wide range of energy (from 80 MeV up to 190 GeV for antiprotons and from 50 MeV up to 270 GeV for positrons) and with high statistics, and that will measure the antihelium/helium ratio with a sensitivity of the order of 10(-8). The detector will fly on-board a polar orbiting Resurs DK1 satellite, which will be launched into space by a Soyuz rocket in 2004 from Baikonur cosmodrome in Kazakhstan, for a 3-year-long mission. Particle identification and energy measurements are performed in the PAMELA apparatus using the following subdetectors: a magnetic spectrometer made up of a permanent magnet equipped with double-sided microstrip silicon detectors, an electromagnetic imaging calorimeter composed of layers of tungsten absorber and silicon detectors planes, a transition radiation detector made of straw tubes interleaved with carbon fiber radiators, a plastic scintillator time-of-flight and trigger system, a set of anticounter plastic scintillator detectors, and a neutron detector. The features of the detectors and the main results obtained in beam test sessions are presented.
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5.
  • Casolino, M., et al. (författare)
  • Cosmic-ray observations of the heliosphere with the PAMELA experiment
  • 2006
  • Ingår i: Astrophysics. - : Elsevier BV. ; , s. 1848-1852
  • Konferensbidrag (refereegranskat)abstract
    • The PAMELA experiment is a multi-purpose apparatus built around a permanent magnet spectrometer, with the main goal of studying in detail the antiparticle component of cosmic rays. The apparatus will be carried in space by means of a Russian satellite, due to launch in 2005, for a three year-long mission. The characteristics of the detectors composing the instrument, alongside the long lifetime of the mission and the orbital characteristics of the satellite, will allow to address several items of cosmic-ray physics. In this paper, we will focus on the solar and heliospheric observation capabilities of PAMELA.
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6.
  • Mocchiutti, E., et al. (författare)
  • PAMELA and electrons
  • 2011
  • Konferensbidrag (refereegranskat)abstract
    • The 15th of June 2006, the PAMELA satellite-borne experiment was launched from the Baikonur cosmodrome and it has been collecting data since July 2006. The apparatus comprises a time-of-flight system, a silicon-microstrip magnetic spectrometer, a silicon-tungsten electromagnetic calorimeter, an anticoincidence system, a shower tail counter scintillator and a neutron detector. The combination of these devices allows precision studies of the charged cosmic radiation to be conducted over a wide energy range (100 MeV-100's GeV) with high statistics. The measurement of the positron to electron fraction and of the electron energy spectrum in order to search for exotic sources, such as dark matter particle annihilations, are within the PAMELA primary scientific goal.
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7.
  • Mocchiutti, E., et al. (författare)
  • The PAMELA space experiment
  • 2009
  • Ingår i: Proceedings of the 44th Rencontres de Moriond - 2009 Electroweak Interactions and Unified Theories, EW 2009. - : Gioi Publishers. ; , s. 317-324
  • Konferensbidrag (refereegranskat)abstract
    • The 15th of June 2006, the PAMELA satellite-borne experiment was launched from the Baikonur cosmodrome and it has been collecting data since July 2006. The apparatus comprises a time-of-flight system, a silicon-microstrip magnetic spectrometer, a silicon-tungsten electromagnetic calorimeter, an anticoincidence system, a shower tail counter scintillator and a neutron detector. The combination of these devices allows precision studies of the charged cosmic radiation to be conducted over a wide energy range (100 MeV - 100's GeV) with high statistics. The primary scientific goal is the measurement of the antiproton and positron energy spectrum in order to search for exotic sources, such as dark matter particle annihilations. PAMELA is also searching for primordial antinuclei (anti-helium) and testing cosmic-ray propagation models through precise measurements of the anti-particle energy spectrum and precision studies of light nuclei and their isotopes. Moreover, PAMELA is investigating phenomena connected with solar and earth physics.
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8.
  • Adriani, O., et al. (författare)
  • An anomalous positron abundance in cosmic rays with energies 1.5-100 GeV
  • 2009
  • Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 458:7238, s. 607-609
  • Tidskriftsartikel (refereegranskat)abstract
    • Antiparticles account for a small fraction of cosmic rays and are known to be produced in interactions between cosmic-ray nuclei and atoms in the interstellar medium(1), which is referred to as a 'secondary source'. Positrons might also originate in objects such as pulsars(2) and microquasars(3) or through dark matter annihilation(4), which would be 'primary sources'. Previous statistically limited measurements(5-7) of the ratio of positron and electron fluxes have been interpreted as evidence for a primary source for the positrons, as has an increase in the total electron+positron flux at energies between 300 and 600 GeV (ref. 8). Here we report a measurement of the positron fraction in the energy range 1.5-100 GeV. We find that the positron fraction increases sharply overmuch of that range, in a way that appears to be completely inconsistent with secondary sources. We therefore conclude that a primary source, be it an astrophysical object or dark matter annihilation, is necessary.
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9.
  • Adriani, O., et al. (författare)
  • Antiprotons in primary cosmic radiation with PAMELA experiment
  • 2013
  • Ingår i: Proceedings of the 33rd International Cosmic Rays Conference, ICRC 2013. - : Sociedade Brasileira de Fisica. - 9788589064293
  • Konferensbidrag (refereegranskat)abstract
    • The latest measurements of antiprotons spectrum and antiproton-to-proton ratio in primary cosmic rays with PAMELA experiment are presented. They are in good agreement with model of secondary production of antiprotons in Galaxy, but they do not completely rule other sources at the high-energies. 
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10.
  • Adriani, O., et al. (författare)
  • Cosmic-Ray Electron Flux Measured by the PAMELA Experiment between 1 and 625 GeV
  • 2011
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 106:20, s. 201101-
  • Tidskriftsartikel (refereegranskat)abstract
    • Precision measurements of the electron component in the cosmic radiation provide important information about the origin and propagation of cosmic rays in the Galaxy. Here we present new results regarding negatively charged electrons between 1 and 625 GeV performed by the satellite-borne experiment PAMELA. This is the first time that cosmic-ray e(-) have been identified above 50 GeV. The electron spectrum can be described with a single power-law energy dependence with spectral index -3.18 +/- 0.05 above the energy region influenced by the solar wind (> 30 GeV). No significant spectral features are observed and the data can be interpreted in terms of conventional diffusive propagation models. However, the data are also consistent with models including new cosmic-ray sources that could explain the rise in the positron fraction.
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11.
  • Adriani, O., et al. (författare)
  • Cosmic-Ray Positron Energy Spectrum Measured by PAMELA
  • 2013
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 111:8, s. 081102-
  • Tidskriftsartikel (refereegranskat)abstract
    • Precision measurements of the positron component in the cosmic radiation provide important information about the propagation of cosmic rays and the nature of particle sources in our Galaxy. The satellite-borne experiment PAMELA has been used to make a new measurement of the cosmic-ray positron flux and fraction that extends previously published measurements up to 300 GeV in kinetic energy. The combined measurements of the cosmic-ray positron energy spectrum and fraction provide a unique tool to constrain interpretation models. During the recent solar minimum activity period from July 2006 to December 2009, approximately 24 500 positrons were observed. The results cannot be easily reconciled with purely secondary production, and additional sources of either astrophysical or exotic origin may be required.
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12.
  • Adriani, O., et al. (författare)
  • Measurement of Boron and Carbon Fluxes in Cosmic Rays with the Pamela Experiment
  • 2014
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 791:2, s. 93-
  • Tidskriftsartikel (refereegranskat)abstract
    • The propagation of cosmic rays inside our galaxy plays a fundamental role in shaping their injection spectra into those observed at Earth. One of the best tools to investigate this issue is the ratio of fluxes for secondary and primary species. The boron-to-carbon (B/C) ratio, in particular, is a sensitive probe to investigate propagation mechanisms. This paper presents new measurements of the absolute fluxes of boron and carbon nuclei as well as the B/C ratio from the PAMELA space experiment. The results span the range 0.44-129 GeV/n in kinetic energy for data taken in the period 2006 July to 2008 March.
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13.
  • Adriani, O., et al. (författare)
  • Measurement of the isotopic composition of hydrogen and helium nuclei in cosmic rays with the PAMELA experiment
  • 2013
  • Ingår i: Astrophysical Journal. - : IOP Publishing. - 0004-637X .- 1538-4357. ; 770:1, s. 2-
  • Tidskriftsartikel (refereegranskat)abstract
    • The satellite-borne experiment PAMELA has been used to make new measurements of cosmic ray H and He isotopes. The isotopic composition was measured between 100 and 600 MeV /n for hydrogen and between 100 and 900 MeV /n for helium isotopes over the 23rd solar minimum from 2006 July to 2007 December. The energy spectrum of these components carries fundamental information regarding the propagation of cosmic rays in the galaxy which are competitive with those obtained from other secondary to primary measurements such as B/C.
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14.
  • Adriani, O., et al. (författare)
  • MEASUREMENTS OF COSMIC-RAY HYDROGEN AND HELIUM ISOTOPES WITH THE PAMELA EXPERIMENT
  • 2016
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 818:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The cosmic-ray hydrogen and helium (H-1, H-2, He-3, He-4) isotopic composition has been measured with the satellite-borne experiment PAMELA, which was launched into low-Earth orbit on board the Resurs-DK1 satellite on 2006 June 15. The rare isotopes H-2 and He-3 in cosmic rays are believed to originate mainly from the interaction of high-energy protons and helium with the galactic interstellar medium. The isotopic composition was measured between 100 and 1100 MeV/n for hydrogen and between 100 and 1400 MeV/n for helium isotopes using two different detector systems over the 23rd solar minimum from 2006 July to 2007 December.
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15.
  • Adriani, O., et al. (författare)
  • Measurements of quasi-trapped electron and positron fluxes with PAMELA
  • 2009
  • Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 114, s. A12218-
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper presents precise measurements of the differential energy spectra of quasi-trapped secondary electrons and positrons and their ratio between 80 MeV and 10 GeV in the near-equatorial region (altitudes between 350 km and 600 km). Latitudinal dependences of the spectra are analyzed in detail. The results were obtained from July until November 2006 onboard the Resurs-DK satellite by the PAMELA spectrometer, a general purpose cosmic ray detector system built around a permanent magnet spectrometer and a silicon-tungsten calorimeter.
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16.
  • Adriani, O., et al. (författare)
  • OBSERVATIONS OF THE 2006 DECEMBER 13 AND 14 SOLAR PARTICLE EVENTS IN THE 80 MeV n(-1)-3 GeV n(-1) RANGE FROM SPACE WITH THE PAMELA DETECTOR
  • 2011
  • Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 742:2, s. 102-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the space spectrometer PAMELA observations of proton and helium fluxes during the 2006 December 13 and 14 solar particle events. This is the first direct measurement of the solar energetic particles in space with a single instrument in the energy range from similar to 80 MeV n(-1) up to similar to 3 GeV n(-1). For the December 13 event, measured energy spectra of solar protons and helium are compared with results obtained by neutron monitors and other detectors. Our measurements show a spectral behavior different from those derived from the neutron monitor network. No satisfactory analytical fitting was found for the energy spectra. During the first hours of the December 13 event, solar energetic particles spectra were close to the exponential form, demonstrating rather significant temporal evolution. Solar He with energy up to 1 GeV n(-1) was recorded on December 13. For the December 14 event, energy of solar protons reached 600 MeV, whereas the maximum energy of He was below 100 MeV n(-1). The spectra were slightly bent in the lower energy range and preserved their form during the second event. Differences in the particle flux appearance and temporal evolution of these two events may argue for special conditions leading to the acceleration of solar particles up to relativistic energies.
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17.
  • Adriani, O., et al. (författare)
  • PAMELA Measurements of Cosmic-Ray Proton and Helium Spectra
  • 2011
  • Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 332:6025, s. 69-72
  • Tidskriftsartikel (refereegranskat)abstract
    • Protons and helium nuclei are the most abundant components of the cosmic radiation. Precise measurements of their fluxes are needed to understand the acceleration and subsequent propagation of cosmic rays in our Galaxy. We report precision measurements of the proton and helium spectra in the rigidity range 1 gigavolt to 1.2 teravolts performed by the satellite-borne experiment PAMELA (payload for antimatter matter exploration and light-nuclei astrophysics). We find that the spectral shapes of these two species are different and cannot be described well by a single power law. These data challenge the current paradigm of cosmic-ray acceleration in supernova remnants followed by diffusive propagation in the Galaxy. More complex processes of acceleration and propagation of cosmic rays are required to explain the spectral structures observed in our data.
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18.
  • Adriani, O., et al. (författare)
  • PAMELA Results on the Cosmic-Ray Antiproton Flux from 60 MeV to 180 GeV in Kinetic Energy
  • 2010
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 105:12, s. 121101-
  • Tidskriftsartikel (refereegranskat)abstract
    • The satellite-borne experiment PAMELA has been used to make a new measurement of the cosmic-ray antiproton flux and the antiproton-to-proton flux ratio which extends previously published measurements down to 60 MeV and up to 180 GeV in kinetic energy. During 850 days of data acquisition approximately 1500 antiprotons were observed. The measurements are consistent with purely secondary production of antiprotons in the Galaxy. More precise secondary production models are required for a complete interpretation of the results.
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19.
  • Adriani, O., et al. (författare)
  • Pamela's measurements of magnetospheric effects on high-energy solar particles
  • 2015
  • Ingår i: Astrophysical Journal Letters. - 2041-8205 .- 2041-8213. ; 801:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The nature of particle acceleration at the Sun, whether through flare reconnection processes or through shocks driven by coronal mass ejections, is still under scrutiny despite decades of research. The measured properties of solar energetic particles (SEPs) have long been modeled in different particle-acceleration scenarios. The challenge has been to disentangle the effects of transport from those of acceleration. The Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) instrument enables unique observations of SEPs including the composition and angular distribution of the particles about the magnetic field, i.e., pitch angle distribution, over a broad energy range (>80 MeV)-bridging a critical gap between space-based and ground-based measurements. We present high-energy SEP data from PAMELA acquired during the 2012 May 17 SEP event. These data exhibit differential anisotropies and thus transport features over the instrument rigidity range. SEP protons exhibit two distinct pitch angle distributions: a low-energy population that extends to 90 degrees and a population that is beamed at high energies (>1 GeV), consistent with neutron monitor measurements. To explain a low-energy SEP population that exhibits significant scattering or redistribution accompanied by a high-energy population that reaches the Earth relatively unaffected by dispersive transport effects, we postulate that the scattering or redistribution takes place locally. We believe that these are the first comprehensive measurements of the effects of solar energetic particle transport in the Earth's magnetosheath.
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20.
  • Adriani, O., et al. (författare)
  • Positrons and electrons in primary cosmic rays as measured in the PAMELA experiment
  • 2009
  • Ingår i: Bulletin of the Russian Academy of Sciences: Physics. - 1062-8738. ; 73:5, s. 568-570
  • Tidskriftsartikel (refereegranskat)abstract
    • The PAMELA experiment is being carried out on board the Russian satellite Resurs DK1 placed in the near-earth near-polar orbit on June 15, 2006. The apparatus comprising a silicon-strip magnetic spectrometer and an electromagnetic calorimeter allows measurement of electron and positron fluxes in cosmic rays in a wide energy interval from ∼100 MeV to hundreds of GeV. The high-energy electron and positron separation technique is discussed and the data on positron-to-electron ratio in primary cosmic rays up to E ≃ 10 GeV from the 2006 - 2007 measurements are reported in this work.
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21.
  • Adriani, O., et al. (författare)
  • Reentrant albedo proton fluxes measured by the PAMELA experiment
  • 2015
  • Ingår i: Journal of Geophysical Research - Space Physics. - 2169-9380 .- 2169-9402. ; 120:5, s. 3728-3738
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a precise measurement of downward going albedo proton fluxes for kinetic energy above similar to 70 MeV performed by the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) experiment at an altitude between 350 and 610 km. On the basis of a trajectory tracing simulation, the analyzed protons were classified into quasi-trapped, concentrating in the magnetic equatorial region, and untrapped spreading over all latitudes, including both short-lived (precipitating) and long-lived (pseudotrapped) components. In addition, features of the penumbra region around the geomagnetic cutoff were investigated in detail. PAMELA results significantly improve the characterization of the high-energy albedo proton populations at low-Earth orbits.
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22.
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23.
  • Adriani, O., et al. (författare)
  • Secondary electron and positron fluxes in the near-Earth space observed in the ARINA and PAMELA experiments
  • 2009
  • Ingår i: Bulletin of the Russian Academy of Sciences: Physics. - 1062-8738. ; 73:3, s. 364-366
  • Tidskriftsartikel (refereegranskat)abstract
    • Secondary electron and positron fluxes in the energy range from 3 MeV to 7 GeV were measured with the ARINA and PAMELA spectrometers onboard the Resurs-DK satellite launched on June 15, 2006 into an elliptical orbit with an inclination of 70.4° and an altitude of 350-600 km. It is shown that positrons dominate over electrons by a factor of up to 4-5 in the geomagnetic equator region (L < 1.2 and B > 0.25).
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24.
  • Adriani, O., et al. (författare)
  • Ten years of PAMELA in space
  • 2017
  • Ingår i: La Rivista del nuovo cimento della Società italiana di fisica. - : Società Italiana di Fisica. - 0393-697X .- 1826-9850. ; 40:10, s. 473-522
  • Tidskriftsartikel (refereegranskat)abstract
    • The PAMELA cosmic-ray detector was launched on June 15th 2006 on board the Russian Resurs-DK1 satellite, and during ten years of nearly continuous data-taking it has observed new interesting features in cosmic rays (CRs). In a decade of operation it has provided plenty of scientific data, covering different issues related to cosmic-ray physics. Its discoveries might change our basic vision of the mechanisms of production, acceleration and propagation of cosmic rays in the Galaxy. The antimatter measurements, focus of the experiment, have set strong constraints to the nature of Dark Matter. Search for signatures of more exotic processes (such as the ones involving Strange Quark Matter) was also pursued. Furthermore, the long-term operation of the instrument had allowed a constant monitoring of the solar activity during its maximum and a detailed and prolonged study of the solar modulation, improving the comprehension of the heliosphere mechanisms. PAMELA had also measured the radiation environment around the Earth, and it detected for the first time the presence of an antiproton radiation belt surrounding our planet. The operation of Resurs-DK1 was terminated in 2016. In this article we will review the main features of the PAMELA instrument and its constructing phases. The main part of the article will be dedicated to the summary of the most relevant PAMELA results over a decade of observation.
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25.
  • Adriani, O., et al. (författare)
  • The PAMELA Mission : Heralding a new era in precision cosmic ray physics
  • 2014
  • Ingår i: Physics reports. - : Elsevier BV. - 0370-1573 .- 1873-6270. ; 544:4, s. 323-370
  • Forskningsöversikt (refereegranskat)abstract
    • On the 15th of June 2006, the PAMELA (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) satellite-borne experiment was launched onboard the Russian Resurs-DK1 satellite by a Soyuz rocket from the Baikonur space centre. The satellite was placed in a quasi-polar 70 degrees inclination orbit at an altitude varying between 350 km and 600 km. New results on the antiparticle component of the cosmic radiation were obtained. The positron energy spectrum and positron fraction were measured from 400 MeV up to 200 GeV revealing a positron excess over the predictions of commonly used propagation models. This can be interpreted either as evidence that the propagation models should be revised or in terms of dark matter annihilation or a pulsar contribution. The antiproton spectrum was measured over the energy range from 60 MeV to 350 GeV. The antiproton spectrum is consistent with secondary production and significantly constrains dark matter models. The energy spectra of protons and helium nuclei were measured up to 1.2 TV. The spectral shapes of these two species are different and cannot be described well by a single power law. For the First time the electron spectrum was measured up to 600 GeV complementing the information obtained from the positron data. Nuclear and isotopic composition was obtained with unprecedented precision. The variation of the low energy proton, electron and positron energy spectra was measured from July 2006 until December 2009 accurately sampling the unusual conditions of the most recent solar minimum activity period (2006-2009). Low energy particle spectra were accurately measured also for various solar events that occurred during the PAMELA mission. The Earth's magnetosphere was studied measuring the particle radiation in different regions of the magnetosphere. Energy spectra and composition of sub-cutoff and trapped particles were obtained. For the first time a belt of trapped antiprotons was detected in the South Atlantic Anomaly region. The flux was found to exceed that for galactic cosmic-ray antiprotons by three order of magnitude.
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26.
  • Adriani, O., et al. (författare)
  • The PAMELA space mission
  • 2008
  • Ingår i: Astroparticle, Part. Space Phys., Detect. Med. Phys. Appl. - Proc. Conf.. - : WORLD SCIENTIFIC. - 9812819088 - 9789812819086 ; , s. 858-864
  • Konferensbidrag (refereegranskat)abstract
    • The PAMELA (a Payload for Antimatter-Matter Exploration and Light-nuclei Astrophysics) experiment, is a satellite-borne particle spectrometer. It was launched on 15th June 2006 from the Baikonur cosmodrome in Kazakhstan, is installed into the Russian Resurs-DK1 satellite. PAMELA is composed of a time-of-flight system, a magnetic spectrometer, a silicon-tungsten electromagnetic calorimeter, an anticoincidence system, a shower tail catcher scintillator and a neutron detector. Among the PAMELA major objectives are the study of charged particles in the cosmic radiation, the investigation of the nature of dark matter, by mean of the measure of the cosmic-ray antiproton and positron spectra over the largest energy range ever achieved. PAMELA has been in a nearly continuous data taking mode since llth July 2006. The status of the apparatus and performances will be presented.
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27.
  • Adriani, O., et al. (författare)
  • The PAMELA space mission
  • 2009
  • Konferensbidrag (refereegranskat)abstract
    • The PAMELA (a Payload for Antimatter-Matter Exploration and Light-nuclei Astrophysics) space mission has been launched on-board the Resurs-DK1 satellite on June 15(th) 2006 from the Baikonur cosmodrome, in Kazakhstan. PAMELA is a particle spectrometer designed to study charged particles in the cosmic radiation with special focus on the investigation of the nature of dark matter, by mean of the measure of the cosmic-ray antiproton and positron spectra over the largest energy range ever achieved.
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28.
  • Adriani, O., et al. (författare)
  • The PAMELA Space Mission for Antimatter and Dark Matter Searches in Cosmic Rays
  • 2010
  • Ingår i: SCIENCE WITH THE NEW GENERATION OF HIGH-ENERGY GAMMA-RAY EXPERIMENTS. - : AIP. - 9780735407671 ; , s. 33-42
  • Konferensbidrag (refereegranskat)abstract
    • On the 15(th) of June 2006, the PAMELA satellite-borne experiment was launched from the Baikonur cosmodrome and it has been collecting data since July 2006. The instrument allows precision studies of the charged cosmic radiation to be conducted over a wide energy range (100 MeV - 100's GeV) with high statistics. The primary scientific goal is the measurement of the antiproton and positron energy spectrum in order to search for exotic sources, such as dark matter particle annihilations. PAMELA is also searching for primordial antinuclei (anti-helium), and testing cosmic-ray propagation models through precise measurements of the antiparticle energy spectrum and precision studies of light nuclei and their isotopes. Moreover, PAMELA is investigating phenomena connected with solar and earth physics. Results of the antiproton and positron data will be presented.
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29.
  • Adriani, O., et al. (författare)
  • Time Dependence of the Electron and Positron Components of the Cosmic Radiation Measured by the PAMELA Experiment between July 2006 and December 2015
  • 2016
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 116:24
  • Tidskriftsartikel (refereegranskat)abstract
    • Cosmic-ray electrons and positrons are a unique probe of the propagation of cosmic rays as well as of the nature and distribution of particle sources in our Galaxy. Recent measurements of these particles are challenging our basic understanding of the mechanisms of production, acceleration, and propagation of cosmic rays. Particularly striking are the differences between the low energy results collected by the space-borne PAMELA and AMS-02 experiments and older measurements pointing to sign-charge dependence of the solar modulation of cosmic-ray spectra. The PAMELA experiment has been measuring the time variation of the positron and electron intensity at Earth from July 2006 to December 2015 covering the period for the minimum of solar cycle 23 (2006-2009) until the middle of the maximum of solar cycle 24, through the polarity reversal of the heliospheric magnetic field which took place between 2013 and 2014. The positron to electron ratio measured in this time period clearly shows a sign-charge dependence of the solar modulation introduced by particle drifts. These results provide the first clear and continuous observation of how drift effects on solar modulation have unfolded with time from solar minimum to solar maximum and their dependence on the particle rigidity and the cyclic polarity of the solar magnetic field.
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30.
  • Adriani, O., et al. (författare)
  • Time Dependence Of The Proton Flux Measured By Pamela During The 2006 July-2009 December Solar Minimum
  • 2013
  • Ingår i: Astrophysical Journal. - : IOP Publishing. - 0004-637X .- 1538-4357. ; 765:2, s. 91-
  • Tidskriftsartikel (refereegranskat)abstract
    • The energy spectra of galactic cosmic rays carry fundamental information regarding their origin and propagation. These spectra, when measured near Earth, are significantly affected by the solar magnetic field. A comprehensive description of the cosmic radiation must therefore include the transport and modulation of cosmic rays inside the heliosphere. During the end of the last decade, the Sun underwent a peculiarly long quiet phase well suited to study modulation processes. In this paper we present proton spectra measured from 2006 July to 2009 December by PAMELA. The large collected statistics of protons allowed the time variation to be followed on a nearly monthly basis down to 400 MV. Data are compared with a state-of-the-art three-dimensional model of solar modulation.
  •  
31.
  • Adriani, O., et al. (författare)
  • Unexpected Cyclic Behavior in Cosmic-Ray Protons Observed by PAMELA at 1 au
  • 2018
  • Ingår i: Astrophysical Journal Letters. - : IOP PUBLISHING LTD. - 2041-8205 .- 2041-8213. ; 852:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Protons detected by the PAMELA experiment in the period 2006-2014 have been analyzed in the energy range between 0.40 and 50 GV to explore possible periodicities besides the well known solar undecennial modulation. An unexpected clear and regular feature has been found at rigidities below 15 GV, with a quasi-periodicity of similar to 450 days. A possible Jovian origin of this periodicity has been investigated in different ways. The results seem to favor a small but not negligible contribution to cosmic rays from the Jovian magnetosphere, even if other explanations cannot be excluded.
  •  
32.
  • Bazilevskaya, G. A., et al. (författare)
  • Solar energetic particle events in 2006-2012 in the PAMELA experiment data
  • 2013
  • Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 409:1
  • Tidskriftsartikel (refereegranskat)abstract
    • The PAMELA magnetic spectrometer launched in June 2006 has observed the last strong energetic solar particle event of the 23rd solar cycle in December 2006. Subsequent long minimum of solar activity and weak development of the 24th solar cycle led to a deficit in the solar energetic particle events on the Earth orbit. As a result, only few events with protons accelerated above 100 MeV occurred in 2010-2012. The paper gives the preliminary results on energetic solar particles in the beginning of the 24th solar circle as measured with the PAMELA instrument.
  •  
33.
  • Bazilevskaya, G. A., et al. (författare)
  • Solar proton events at the end of the 23rd and start of the 24th solar cycle recorded in the PAMELA experiment
  • 2013
  • Ingår i: Bulletin of the Russian Academy of Sciences: Physics. - 1062-8738. ; 77:5, s. 493-496
  • Tidskriftsartikel (refereegranskat)abstract
    • The PAMELA magnetic spectrometer was launched into a near-Earth orbit on board the Resurs-DK1 satellite in June 2006; in December 2006, it recorded the last strong solar high-energy particle event of the 23rd solar cycle. A deficit was thereafter observed in solar energetic particle events because of the lengthy solar activity minimum and the weak evolution of the next (24th) solar cycle. As a result, only a few solar events involving protons with energies of more than 100 MeV were recorded between 2010 and 1012. This work presents the preliminary results from measurements of charged particle fluxes in these events, recorded by the Pamela spectrometer.
  •  
34.
  • Boezio, M., et al. (författare)
  • Nine years of cosmic rays investigation by the PAMELA experiment
  • 2015
  • Ingår i: Proceedings of Science. - : Proceedings of Science (PoS).
  • Konferensbidrag (refereegranskat)abstract
    • The PAMELA cosmic ray detector was launched on June 15th of 2006 on board the Russian Resurs-DK1 satellite and during nine years of continuous data-taking it has ob- served very interesting features in cosmic rays, namely in the fluxes of protons, helium and electrons. Its discoveries might change our basic vision of the mechanisms of pro- duction, acceleration and propagation of cosmic rays in the Galaxy. Moreover, PAMELA measurements of cosmic antiproton and positron fluxes and positron-to-all-electron ratio have been setting strong constraints to the nature of Dark Matter. Measurements of boron, carbon, lithium and beryllium (together with the isotopic fraction) will also shed new light on the elemental composition of the cosmic radiation. Search for signatures of more exotic processes (such as the ones involving Strange Quark Matter) is also pursued. Furthermore, the instrument is still functional allowing a constant monitoring of the solar activity during its maximum and a detailed and prolonged study of the solar modulation, improving the comprehension of the heliosphere mechanisms. PAMELA is also measur- ing the radiation environment around the Earth, and it detected for the first time the presence of an antiproton radiation belt surrounding our planet. In this highlight paper PAMELA main results will be reviewed.
  •  
35.
  • Boezio, M., et al. (författare)
  • PAMELA and indirect dark matter searches
  • 2009
  • Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 11, s. 105023-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a review of the experimental results obtained by PAMELA in measuring the (p, (p) over bar ) and e(+/-) abundance in cosmic rays. In this context, we discuss the interpretation of the observed anomalous positron excess in terms of the annihilation of dark matter particles as well as in terms of standard astrophysical sources. Moreover we show the constraints on dark matter models from (p) over bar data.
  •  
36.
  • Boezio, M., et al. (författare)
  • The first year in orbit of the pamela experiment
  • 2007
  • Ingår i: Proceedings of the 30th International Cosmic Ray Conference, ICRC 2007. - : Universidad Nacional Autonoma de Mexico. ; , s. 99-102
  • Konferensbidrag (refereegranskat)abstract
    • On the 15th of June 2006, the PAMELA experiment mounted on the Resurs DK1 satellite, was launched from the Baikonur cosmodrome and it has been collecting data since July 2006. PAMELA is a satellite-borne apparatus designed to study charged particles in the cosmic radiation, to investigate the nature of dark matter, measuring the cosmic-ray antiproton and positron spectra over the largest energy range ever achieved, and to search for antinuclei with unprecedented sensitivity. The PAMELA apparatus comprises a time-of-flight system, a magnetic spectrometer, a silicon-tungsten electromagnetic calorimeter, an anticoincidence system, a shower tail catcher scintillator and a neutron detector. We will present the status of the apparatus after one year in orbit. Furthermore, we will discuss the PAMELA in-flight performances.
  •  
37.
  • Boezio, M., et al. (författare)
  • The PAMELA experiment : A cosmic ray experiment deep inside the heliosphere
  • 2017
  • Ingår i: Proceedings of Science. - : Sissa Medialab Srl.
  • Konferensbidrag (refereegranskat)abstract
    • It was the 15th of June of 2006 when the PAMELA satellite-borne experiment was launched from the Baikonur cosmodrome in Kazakstan. Then, for nearly ten years, PAMELA has been making high-precision measurements of the charged component of the cosmic radiation opening a new era of precision studies in cosmic rays and challenging our basic vision of the mechanisms of production, acceleration and propagation of cosmic rays in the galaxy and in the heliosphere. The study of the time dependence of the various components of the cosmic radiation from the unusual 23rd solar minimum through the maximum of solar cycle 24 clearly shows solar modulation effects as well as charge sign dependence. PAMELA measurement of the energy spectra during solar energetic particle events fills the existing energy gap between the highest energy particles measured in space and the ground-based domain. Finally, by sampling the particle radiation in different regions of the magnetosphere, PAMELA data provide a detailed study of the Earth s magnetosphere. In this highlight paper, PAMELA main results as well as recent progress about solar and heliospheric physics with PAMELA will be presented. 
  •  
38.
  • Boezio, M., et al. (författare)
  • The PAMELA experiment and antimatter in the universe
  • 2014
  • Ingår i: Hyperfine Interactions. - : Springer Science and Business Media LLC. - 0304-3843 .- 1572-9540. ; 228:1-3, s. 101-109
  • Tidskriftsartikel (refereegranskat)abstract
    • On the 15th of June 2006, the PAMELA satellite-borne experiment was launched from the Baikonur cosmodrome and it has been collecting data since July 2006. The primary scientific goal is the measurement of the antiproton and positron energy spectra. Antiparticles are a natural component of the cosmic radiation being produced in the interaction between cosmic rays and the interstellar matter. They have been shown to be extremely interesting for understanding the propagation mechanisms of cosmic rays. Furthermore, novel sources of primary cosmic-ray antiparticles of either astrophysical or exotic origin (e.g. annihilation of dark matter particles) can also be probed. In this paper we review the PAMELA antiparticle results and their significance for the field of astroparticle physics.
  •  
39.
  • Boezio, M., et al. (författare)
  • The PAMELA space experiment : First year of operation
  • 2008
  • Ingår i: Journal of Physics, Conference Series. - : Institute of Physics Publishing (IOPP). - 1742-6588 .- 1742-6596. ; 110:6
  • Tidskriftsartikel (refereegranskat)abstract
    • On the 15th of June 2006 the PAMELA experiment, mounted on the Resurs DK1 satellite, was launched from the Baikonur cosmodrome and it has been collecting data since July 2006. PAMELA is a satellite-borne apparatus designed to study charged particles in the cosmic radiation, to investigate the nature of dark matter, measuring the cosmic-ray antiproton and positron spectra over the largest energy range ever achieved, and to search for antinuclei with unprecedented sensitivity. The apparatus comprises a time-of-flight system, a silicon-microstrip magnetic spectrometer, a silicon-tungsten electromagnetic calorimeter, an anticoincidence system, a shower tail catcher scintillator and a neutron detector. The combination of these devices allows charged particle identification over a wide energy range. © 2008 IOP Publishing Ltd.
  •  
40.
  • Boezio, M., et al. (författare)
  • The PAMELA space mission for antimatter and dark matter searches in space
  • 2012
  • Ingår i: Hyperfine Interactions. - : Springer Science and Business Media LLC. - 0304-3843 .- 1572-9540. ; 213:1-3, s. 147-158
  • Tidskriftsartikel (refereegranskat)abstract
    • The PAMELA satellite-borne experiment has presented new results on cosmic-ray antiparticles that can be interpreted in terms of DM annihilation or pulsar contribution. The instrument was launched from the Baikonur cosmodrome and it has been collecting data since July 2006. The combination of a permanent magnet silicon strip spectrometer and a silicon-tungsten imaging calorimeter allows precision studies of the charged cosmic radiation to be conducted over a wide energy range with high statistics. The primary scientific goal is the measurement of the antiproton and positron energy spectrum in order to search for exotic sources. PAMELA is also searching for primordial antinuclei (anti-helium), and testing cosmic-ray propagation models through precise measurements of the antiparticle energy spectrum and precision studies of light nuclei and their isotopes. This talk illustrates the most recent scientific results obtained by the PAMELA experiment.
  •  
41.
  • Bogomolov, E. A., et al. (författare)
  • Spectra of solar neutrons with energies of ~10–1000 MeV in the PAMELA experiment in the flare events of 2006–2015
  • 2017
  • Ingår i: Bulletin of the Russian Academy of Sciences: Physics. - : Allerton Press Incorporation. - 1062-8738. ; 81:2, s. 132-135
  • Tidskriftsartikel (refereegranskat)abstract
    • The first results from measuring the spectra of solar neutrons with energies of ~10–1000 MeV in the solar flares of 2006–2015 observed by the PAMELA international space experiment are presented. The PAMELA neutron detector with 3He counters and a moderator with an area of 0.18 m2 allows us to estimate the flux of solar neutrons during solar flares. Solar neutrons with energies of ~10–1000 MeV likely occurred in 21 out of the 24 analyzed flares of 2006–2015.
  •  
42.
  • Bonvicini, V., et al. (författare)
  • Performance of the PAMELA Si-W imaging calorimeter in space
  • 2009
  • Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 160, s. 012039-
  • Tidskriftsartikel (refereegranskat)abstract
    • The Payload for Antimatter-Matter Exploration and Light Nuclei Astrophysics (PAMELA), primarily designed to directly measure antiparticles (antiprotons and positrons) in the cosmic radiation, was launched successfully on June 15th, 2006, and, since then, it is in continuous data taking. The calorimeter of the PAMELA apparatus has been designed to identify antiprotons from an electron background and positrons from a background of protons with high efficiency and rejection power. It is a sampling silicon-tungsten imaging calorimeter, which comprises 44 single-sided silicon sensor planes (380 μm thick) interleaved with 22 plates of tungsten absorber (0.74 X0 each). It is the first silicon-tungsten calorimeter to be launched in space. In this work we present the in-orbit performance of the calorimeter, including the measured identification capabilities. The calorimeter provides a proton rejection factor of ∼105 while keeping a high efficiency in selecting electrons and positrons, thus fulfilling the identification power needed to reach the primary scientific objectives of PAMELA. We show also that, after almost two years of operation in space, the calorimeter is still performing nominally.
  •  
43.
  • Bruno, A., et al. (författare)
  • First detection of geomagnetically trapped antiprotons by the PAMELA experiment
  • 2011
  • Ingår i: Proceedings of the 32nd International Cosmic Ray Conference, ICRC 2011. - : Institute of High Energy Physics. ; , s. 86-89
  • Konferensbidrag (refereegranskat)abstract
    • We present the measurement of geomagnetically trapped antiprotons in the South Atlantic Anomaly performed by the PAMELA satellite-bourne experiment. The existence of an antiproton radiation belt, predicted by several models as the product of cosmic ray interactions with the residual terrestrial atmosphere, is evidenced for the first time. PAMELA measured the antiproton spectrum in the kinetic energy range between 60 and 750 MeV, reporting a trapped antiproton flux which exceeds by about 3 orders of magnitude the interplanetary cosmic ray antiproton flux. An estimation of the mean under-cutoff antiproton flux outside radiation belts has been also provided.
  •  
44.
  • Bruno, A., et al. (författare)
  • Geomagnetically trapped, albedo and solar energetic particles : Trajectory analysis and flux reconstruction with PAMELA
  • 2017
  • Ingår i: Advances in Space Research. - : Elsevier. - 0273-1177 .- 1879-1948. ; 60:4, s. 788-795
  • Tidskriftsartikel (refereegranskat)abstract
    • The PAMELA satellite experiment is providing comprehensive observations of the interplanetary and magnetospheric radiation in the near-Earth environment. Thanks to its identification capabilities and the semi-polar orbit, PAMELA is able to precisely measure the energetic spectra and the angular distributions of the different cosmic-ray populations over a wide latitude region, including geomagnetically trapped and albedo particles. Its observations comprise the solar energetic particle events between solar cycles 23 and 24, and the geomagnetic cutoff variations during magnetospheric storms. PAMELA's measurements are supported by an accurate analysis of particle trajectories in the Earth's magnetosphere based on a realistic geomagnetic field modeling, which allows the classification of particle populations of different origin and the investigation of the asymptotic directions of arrival.
  •  
45.
  • Bruno, A., et al. (författare)
  • PAMELA's measurements of geomagnetic cutoff variations during solar energetic particle events
  • 2015
  • Ingår i: Proceedings of Science. - : Proceedings of Science (PoS).
  • Konferensbidrag (refereegranskat)abstract
    • Data from the PAMELA satellite experiment were used to measure the geomagnetic cutoff for high-energy ( 80 MeV) protons during the solar particle events on 2006 December 13 and 14. The variations of the cutoff latitude as a function of rigidity were studied on relatively short timescales, corresponding to single spacecraft orbits (about 94 minutes). Estimated cutoff values were cross-checked with those obtained by means of a trajectory tracing approach based on dynamical empirical modeling of the Earth's magnetosphere. We find significant variations in the cutoff latitude, with a maximum suppression of about 6 deg for 80 MeV protons during the main phase of the storm. The observed reduction in the geomagnetic shielding and its temporal evolution were compared with the changes in the magnetosphere configuration, investigating the role of IMF, solar wind and geomagnetic (Kp, Dst and Sym-H indexes) variables and their correlation with PAMELA cutoff results.
  •  
46.
  • Bruno, A., et al. (författare)
  • PAMELA's measurements of geomagnetically trapped and albedo protons
  • 2015
  • Ingår i: Proceedings of Science. - : Proceedings of Science (PoS).
  • Konferensbidrag (refereegranskat)abstract
    • Data from the PAMELA satellite experiment were used to perform a detailed measurement of under-cutoff protons at low Earth orbits. On the basis of a trajectory tracing approach using a realistic description of the magnetosphere, protons were classified into geomagnetically trapped and re-entrant albedo. The former include stably-trapped protons in the South Atlantic Anomaly, which were analyzed in the framework of the adiabatic theory, investigating energy spectra, spatial and angular distributions; results were compared with the predictions of the AP8 and the PSB97 empirical trapped models. The albedo protons were classified into quasi-trapped, concentrating in the magnetic equatorial region, and un-trapped, spreading over all latitudes and including both short-lived (precipitating) and long-lived (pseudo-trapped) components. Features of the penumbra region around the geomagnetic cutoff were investigated as well. PAMELA observations significantly improve the characterization of the high energy proton populations in near Earth orbits. The.
  •  
47.
  • Bruno, A., et al. (författare)
  • Precise cosmic rays measurements with PAMELA
  • 2013
  • Ingår i: Acta Polytechnica. - 1210-2709. ; 53:Suppl.1, s. 712-717
  • Tidskriftsartikel (refereegranskat)abstract
    • The PAMELA experiment was launched on board the Resurs-DK1 satellite on June 15th 2006. The apparatus was designed to conduct precision studies of charged cosmic radiation over a wide energy range, from tens of MeV up to several hundred GeV, with unprecedented statistics. In five years of continuous data taking in space, PAMELA accurately measured the energy spectra of cosmic ray antiprotons and positrons, as well as protons, electrons and light nuclei, sometimes providing data in unexplored energetic regions. These important results have shed new light in several astrophysical fields like: an indirect search for Dark Matter, a search for cosmological antimatter (anti-Helium), and the validation of acceleration, transport and secondary production models of cosmic rays in the Galaxy. Some of the most important items of Solar and Magnetospheric physics were also investigated. Here we present the most recent results obtained by the PAMELA experiment.
  •  
48.
  • Bruno, A., et al. (författare)
  • Solar energetic particle events : Trajectory analysis and flux reconstruction with PAMELA
  • 2015
  • Ingår i: Proceedings of Science. - : Proceedings of science.
  • Konferensbidrag (refereegranskat)abstract
    • The PAMELA satellite experiment is providing first direct measurements of Solar Energetic Particles (SEPs) with energies from about 80 MeV to several GeV in near-Earth space, bridging the low energy data by other space-based instruments and the Ground Level Enhancement (GLE) data by the worldwide network of neutron monitors. Its unique observational capabilities include the possibility of measuring the flux angular distribution and thus investigating possible anisotropies. This work reports the analysis methods developed to estimate the SEP energy spectra as a function of the particle pitch-angle with respect to the Interplanetary Magnetic Field (IMF) direction. The crucial ingredient is provided by an accurate simulation of the asymptotic exposition of the PAMELA apparatus, based on a realistic reconstruction of particle trajectories in the Earth's magnetosphere. As case study, the results for the May 17, 2012 event are presented.
  •  
49.
  • Bruno, A., et al. (författare)
  • Trapped protons in SAA measured by the PAMELA experiment
  • 2011
  • Ingår i: Proceedings of the 32nd International Cosmic Ray Conference, ICRC 2011. - : Institute of High Energy Physics. ; , s. 82-85
  • Konferensbidrag (refereegranskat)abstract
    • An accurate measurement of under cutoff proton fluxes in the energy range 60 MeV ÷ 3 GeV has been performed by the PAMELA satellite-borne experiment. Thanks to the high identification performances and to the semipolar and elliptic satellite orbit, PAMELA is able to provide information about spectra and composition of particles in different regions of the magnetosphere. Here we present the measurement of the geomagnetically trapped protons from the inner radiation belt (SAA). The fluxes as a function of equatorial pitch angle and McIlwain L-shell are reported.
  •  
50.
  • Carbone, R., et al. (författare)
  • Pamela observation of the 2012 may 17 gle event
  • 2013
  • Ingår i: Proceedings of the 33rd International Cosmic Rays Conference, ICRC 2013. - : Sociedade Brasileira de Fisica. - 9788589064293
  • Konferensbidrag (refereegranskat)abstract
    • The PAMELA (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) satellite-borne experiment has been collecting data in orbit since July 2006, providing accurate measurements of the energy spectra and composition of the cosmic radiation from a few hundred MeV/n up to hundred GeV/n. This wide interval of measured energies makes PAMELA a unique instrument for Solar Energetic Particle (SEP) observations. Not only does it span the energy range between the ground-based neutron monitor data and the observations of SEPs from space, but also PAMELA carries out the first direct measurements of the composition for the highest energy SEP events, including those causing Ground Level Enhancements (GLEs). PAMELA has registered many SEP events in solar cycle 24 including the 2012 May 17 GLE event (GLE 71), offering unique opportunities to address the question of high-energy SEP origin. Experimental performances and preliminary results on the 2012 May 17 events will be presented. We will discuss the derived particle injection time and compare with other time scales at the Sun including the flare and CME onset times. 
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