Browsing Research Output by Subject "cosmic rays"

Now showing items 1-10 of 13

    • Cosmic ray modulation beyond the heliopause: a hybrid modeling approach 

      Strauss, R.D.; Potgieter, M.S.; Ferreira, S.E.S.; Fichtner, H.; Scherer, K. (IOP Publishing, 2013)
      Results from a newly developed hybrid cosmic ray (CR) modulation model are presented. In this approach, the transport of CRs is computed by incorporating the plasma flow from a magnetohydrodynamic model for the heliospheric ...

    • Cosmic rays in astrospheres 

      Scherer, K.; Van der Schyff, A.; Ferreira, S.E.S.; Strauss, R.D.; Bomans, D.J. (EDP Sciences, 2015)
      Context: Cosmic rays passing through large astrospheres can be efficiently cooled inside these “cavities” in the interstellar medium. Moreover, the energy spectra of these energetic particles are already modulated in front ...

    • A cosmic-ray positron anisotropy due to two middle-aged, nearby pulsars? 

      Büsching, I.; De Jager, O.C.; Potgieter, M.S.; Venter, C. (IOP Publishing, 2008)
      Geminga and B0656+14 are the closest pulsars with characteristic ages in the range of 100 kyr to 1 Myr. They both have spin-down powers of the order 3 × 1034 ergs s–1 at present. The winds of these pulsars had most probably ...

    • H.E.S.S. reveals a lack of TeV emission from the supernova remnant Puppis A 

      Abramowski, A.; Böttcher, M.; Davids, I.D.; Ivascenko, A.; Krüger, P.P.; Pekeur, N.W.; Spanier, F.; Sushch, I.; Venter, C.; Vorster, M.; H.E.S.S. Collaboration (EDP Sciences, 2015)
      Context: Puppis A is an interesting ~4 kyr-old supernova remnant (SNR) that shows strong evidence of interaction between the forward shock and a molecular cloud. It has been studied in detail from radio frequencies to ...

    • HESS very-high-energy gamma-ray sources without identified counterparts 

      Büsching, I.; De Jager, O.C.; Holleran, M.; Raubenheimer, B.C.; Venter, C.; H.E.S.S. Collaboration (EDP sciences, 2008)
      Context.The detection of gamma rays in the very-high-energy (VHE) energy range (100 GeV–100 TeV) provides a direct view of the parent population of ultra-relativistic particles found in astrophysical sources. For this ...

    • A local interstellar spectrum for galactic electrons 

      Potgieter, M.S.; Nndanganeni, R.R. (Elsevier, 2013)
      A heliopause spectrum at 122 AU from the Sun is presented for galactic electrons over an energy range from 1 MeV to 50 GeV that can be considered the lowest possible local interstellar spectrum (LIS). The focus of this ...

    • Modulation of galactic electrons in the heliosphere during the unusual solar minimum of 2006-2009: a modeling approach 

      Potgieter, M.S.; Vos, E.E.; Munini, R.; Boezio, M.; Di Felice, V. (IOP Publishing, 2015)
      The last solar minimum activity period, and the consequent minimum modulation conditions for cosmic rays, was unusual. The highest levels of Galactic protons were recorded at Earth in late 2009 in contrast to expectations. ...

    • New modeling of galactic proton modulation during the minimum of solar cycle 23/24 

      Vos, Etienne E.; Potgieter, Marius S. (IOP Publishing, 2015)
      During the recent prolonged solar minimum of cycle 23/24, the PAMELA detector measured 27-day averaged Galactic proton energy spectra over the energy range that is important for solar modulation. By comparing these spectra ...

    • A numerical simulation of cosmic-ray modulation near the heliopause 

      Luo, Xi; Potgieter, Marius; Zhang, Ming; Feng, Xueshang; Pogorelov, N.V. (IOP Publishing, 2015)
      Based on a hybrid galactic cosmic-ray transport model, which incorporated MHD global heliospheric data into Parker’s cosmic-ray transport equation, we studied the behavior of the transport of galactic cosmic rays and ...

    • Probing the gamma-ray emission from HESS J1834-087 using H.E.S.S. and Fermi LAT observations 

      Abramowski, A.; Böttcher, M.; Casanova, S.; Davids, I.D.; Krüger, P.P.; Pekeur, N.W.; Sushch, I.; Venter, C.; Vorster, M.; H.E.S.S. Collaboration (EDP Sciences, 2015)
      Aims: Previous observations with the High Energy Stereoscopic System (H.E.S.S.) have revealed an extended very-high-energy (VHE; E> 100 GeV) γ-ray source, HESS J1834−087, coincident with the supernova remnant (SNR) W41. ...