Transport Modeling of Interplanetary Electrons in the 2002 October 20 Solar Particle Event

We analyze electrons in the energy range 1-180 keV, observed by the Wind spacecraft following an impulsive solar flare on 2002 October 20. The event is characterized by weak, but measurable pitch-angle scattering, which allows a characterization of the pitch-angle scattering coefficient , as well as...

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Bibliographic Details
Published in:The Astrophysical journal 2018-12, Vol.869 (2), p.168
Main Authors: Dröge, W., Kartavykh, Y. Y., Wang, L., Telloni, D., Bruno, R.
Format: Article
Language:English
Subjects:
Astrophysics
Electron density
Electron flux
Fluctuations
Particle physics
Pitch (inclination)
Resonant interactions
Scattering coefficient
Solar flares
Solar storms
Spacecraft
Sun: heliosphere
Sun: particle emission
Transport equations
Turbulence
Wavelet transforms
Wind spacecraft
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Summary:We analyze electrons in the energy range 1-180 keV, observed by the Wind spacecraft following an impulsive solar flare on 2002 October 20. The event is characterized by weak, but measurable pitch-angle scattering, which allows a characterization of the pitch-angle scattering coefficient , as well as by particle reflection at an outer boundary. Based on numerical solutions of the focused transport equation we present fits to the observed electron fluxes, with emphasis on a detailed modeling of the particles' angular distributions. By means of the wavelet transform method we estimate the slab component of the fluctuation, which is frequently assumed to dominate the particle scattering. We find that the values of obtained from the modeling for several energy ranges disagree strongly with the ones calculated from the estimated slab component for this event and standard quasi-linear theory, in the pitch-angle dependence of the scattering coefficient and also in its magnitude. These results indicate that in this event the scattering of electrons at low energies is much weaker than predicted by the above models, and that at large wavenumbers the slab component makes up only a few per cent of the fluctuations. We discuss whether in weak-scattering events the concept of pitch-angle diffusion due to a resonant interaction of the particles with the turbulence would have to be reconsidered, and whether additional effects such magnetic mirroring of the electrons and intermittency of the fluctuations would have to be taken into account.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/aaec6c