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Title: PAMELA’S MEASUREMENTS OF MAGNETOSPHERIC EFFECTS ON HIGH-ENERGY SOLAR PARTICLES

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° 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 ormore » 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.« less
Authors:
;  [1] ;  [2] ;  [3] ; ;  [4] ; ; ;  [5] ;  [6] ;  [7] ;  [8] ;  [9] ;  [10] ;  [11] ; ;  [12] ;  [13] ; ;  [14] more »; « less
  1. Department of Physics and Astronomy, University of Florence, I-50019 Sesto Fiorentino, Florence (Italy)
  2. Department of Physics, University of Naples “Federico II,” I-80126 Naples (Italy)
  3. Lebedev Physical Institute, RU-119991 Moscow (Russian Federation)
  4. University of Bari, I-70126 Bari (Italy)
  5. INFN, Sezione di Trieste, I-34149 Trieste (Italy)
  6. Ioffe Physical Technical Institute, RU-194021 St. Petersburg (Russian Federation)
  7. INFN, Sezione di Florence, I-50019 Sesto Fiorentino, Florence (Italy)
  8. Space Science Center, University of New Hampshire, Durham, NH (United States)
  9. INFN, Sezione di Bari, I-70126 Bari (Italy)
  10. INFN, Sezione di Naples, I-80126 Naples (Italy)
  11. KTH, Department of Physics, and the Oskar Klein Centre for Cosmoparticle Physics, AlbaNova University Centre, SE-10691 Stockholm (Sweden)
  12. INFN, Sezione di Rome “Tor Vergata,” I-00133 Rome (Italy)
  13. IFAC, I-50019 Sesto Fiorentino, Florence (Italy)
  14. Heliophysics Division, NASA Goddard Space Flight Center, Greenbelt, MD (United States)
Publication Date:
OSTI Identifier:
22518809
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 801; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCELERATION; ANGULAR DISTRIBUTION; ANISOTROPY; ANTIMATTER; ASTROPHYSICS; GEV RANGE; HELIOSPHERE; INCLINATION; LIGHT NUCLEI; MAGNETIC FIELDS; MAGNETOSHEATH; MASS; MEV RANGE; SCATTERING; SOLAR PARTICLES; SUN