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| Titel |
Neutralized solar energetic particles in the inner heliosphere: a parameter study |
| VerfasserIn |
Xiao-Dong Wang, Berndt Klecker, Yoshifumi Futaana, Fabrice Cipriani, Stas Barabash, Martin Wieser |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250127514
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| Publikation (Nr.) |
 EGU/EGU2016-7402.pdf |
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| Zusammenfassung |
| The large fluxes of solar energetic particles (SEPs) in Gradual Events, dominated by protons,
are believed to be produced by the acceleration of shocks driven by coronal mass ejections
(CMEs). As SEPs propagate in the lower corona, there is a chance for them to be
neutralized via the charge exchange and/or recombination processes and become
energetic neutral atoms (ENAs). These ENAs retain the velocity of their parent
SEPs and propagate in straight lines without the influence of the interplanetary
magnetic field, and therefore might potentially serve as a new window to observe the
particle acceleration processes in the solar corona. STEREO/Low Energy Telescope
reported the first probable observation of hydrogen ENAs between 1.6 MeV - 5
MeV from the Sun prior to an X-class flare/CME [Mewaldt et al., 2009]. While
such observations were somehow controversial, Wang et al. [2014] simulated the
neutralization of solar energetic protons in the corona lower than 40 RS, and the
result agreed with the STEREO observation. In this work, we further developed a
production model of the ENA near the sun together with a transport model toward
the inner planets, and explore the dependences of the ENA characteristics against
the model parameters. These parameters include the angular width of the CME,
its propagation direction with respect to the Sun-observer line, the propagation
speed, the particle density in the corona, the abundances of O6+ and C4+, and the
reaction rate of electron impact ionization in the loss of ENAs, and the heliospheric
distance of the observer. The calculated ENA flux shows that at lower energy the
expected ENA flux depends most sensitively on the CME apex angle and the CME
propagation direction. At higher energy the dependence on the coronal density is more
prominent.
References
Mewaldt, R. A., R. A. Leske, E. C. Stone, A. F. Barghouty, A. W. Labrador, C. M. S.
Cohen, A. C. Cummings, A. J. Davis, T. T. von Rosenvinge, and M. E. Wiedenbeck (2009),
STEREO Observations of Energetic Neutral Hydrogen Atoms During the 2006 December 5
Solar Flare, Astrophys. J. Lett., 693(1), L11.
Wang, L., G. Li, A. Y. Shih, R. P. Lin, and R. F. Wimmer-Schweingruber (2014),
Simulation of Energetic Neutral Atoms from Solar Energetic Particles, Astrophys. J. Lett.,
793(2), L37. |
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