Interpretation of increased energetic particle flux measurements by SEPT aboard the STEREO spacecraft and contamination
| Autor: | Reinhold Müller-Mellin, Nina Dresing, Stephan Böttcher, Bernd Heber, Raúl Gómez-Herrero, S. Wraase, Radoslav Bučík, Andreas Klassen |
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| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: |
010504 meteorology & atmospheric sciences
Proton Astrophysics::High Energy Astrophysical Phenomena FOS: Physical sciences chemistry.chemical_element Astrophysics Electron 01 natural sciences Ion Nuclear physics Physics - Space Physics 0103 physical sciences 010303 astronomy & astrophysics Solar and Stellar Astrophysics (astro-ph.SR) Helium 0105 earth and related environmental sciences Physics Range (particle radiation) Astronomy and Astrophysics Space Physics (physics.space-ph) Charged particle Solar wind chemistry Astrophysics - Solar and Stellar Astrophysics 13. Climate action Space and Planetary Science Physics::Space Physics Heliosphere |
| Popis: | Context. Interplanetary (IP) shocks are known to be accelerators of energetic charged particles observed in-situ in the heliosphere. However, the acceleration of near-relativistic electrons by shocks in the interplanetary medium is often questioned. On 9 August 2011 a corotating interaction region (CIR) passed STEREO B (STB), which resulted in a flux increase in the electron and ion channels of the Solar Electron and Proton Telescope (SEPT). Because electron measurements in the few keV to several 100 keV range rely on the so-called magnet foil technique, which is utilized by SEPT, ions can contribute to the electron channels. Aim. We aim to investigate whether the flux increase in the electron channels of SEPT during the CIR event on 9 August 2011 is caused by ion contamination only. Methods. We compute the SEPT response functions for protons and helium utilizing an updated GEANT4 model of SEPT. The CIR energetic particle ion spectra for protons and helium are assumed to follow a Band function in energy per nucleon with a constant helium to proton ratio. Results. Our analysis leads to a helium to proton ratio of 16.9% and a proton flux following a Band function with the parameters I0 = 1.24 × 104 (cm2 s sr MeV nuc−1)−1, Ec = 79 keV nuc−1, and spectral indices of γ1 = −0.94 and γ2 = −3.80, which are in good agreement with measurements by the Suprathermal Ion Telescope (SIT) aboard STB. Conclusions. Since our results explain the SEPT measurements, we conclude that no significant amount of electrons were accelerated between 55 and 425 keV by the CIR. |
| Databáze: | OpenAIRE |
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