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ASTRA Proceedings An open-access journal for refereed proceedings in extraterrestrial research
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Volume 2
ASTRA Proc., 2, 63-65, 2016
https://doi.org/10.5194/ap-2-63-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
ASTRA Proc., 2, 63-65, 2016
https://doi.org/10.5194/ap-2-63-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

  15 Jan 2016

15 Jan 2016

Cross-field transport and pitch-angle anisotropy of solar energetic particles in MHD turbulence

F. Fraschetti F. Fraschetti
  • Departments of Planetary Sciences and Astronomy, University of Arizona, Arizona, USA

Abstract. Recent modelling of solar energetic particles (SEPs) propagation through the heliospheric turbulence, also discussed in this workshop, has investigated the role of the pitch-angle scattering and the perpendicular transport in spreading particles in heliolongitude, as shown by multi-spacecraft measurements (STEREO A/B, ACE, SOHO, etc.) at 1 AU in various energy ranges. In some events the first-order pitch-angle anisotropy of the particles distribution is not-negligible. We calculate the average perpendicular displacement due to the gradient/curvature drift in an inhomogeneous turbulence accounting for pitch-angle dependence for two MHD turbulence models: (a) 3-D isotropic, (b) anisotropic as conjectured by Goldreich-Sridhar. We find in both cases that the drift scales as (1 − μ2)2 with the cosine of pitch-angle μ, in contrast with previous models for transport of SEPs. This result can impact the models of propagation of SEPs through the heliosphere.

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Recent measurements of solar energetic particles (SEPs) by multi-spacecraft fleet at 1 AU in various energy ranges are compatible with a not-vanishing first-order anisotropy in pitch-angle of the particles phase-space distribution. By using an analytic model for the time-dependent perpendicular transport, we calculate the effect of an inhomogeneous magnetic turbulence on pitch-angle anisotropy. We find that the transport coefficient scales differently from previous transport models.
Recent measurements of solar energetic particles (SEPs) by multi-spacecraft fleet at 1 AU in...
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