On aspects pertaining to the perpendicular diffusion of solar energetic particles
Abstract
The multitude of recent multi-point spacecraft observations of solar energetic particle (SEP) events has made it
possible to study the longitudinal distribution of SEPs in great detail. SEPs, even those accelerated during impulsive
events, show a much wider than expected longitudinal extent, bringing into question the processes responsible for
their transport perpendicular to the local magnetic field. In this paper, we examine some aspects of perpendicular
transport by including perpendicular diffusion in a numerical SEP transport model that simulates the propagation
of impulsively accelerated SEP electrons in the ecliptic plane. We find that (1) the pitch-angle dependence of
the perpendicular diffusion coefficient is an important, and currently mainly overlooked, transport parameter.
(2) SEP intensities are generally asymmetric in longitude, being enhanced toward the west of the optimal magnetic
connection to the acceleration region. (3) The maximum SEP intensity may also be shifted (parameter dependently)
away from the longitude of best magnetic connectivity at 1 AU. We also calculate the maximum intensity, the time
of maximum intensity, the onset time, and the maximum anisotropy as a function of longitude at Earth’s orbit and
compare the results, in a qualitative fashion, to recent spacecraft observations
URI
http://hdl.handle.net/10394/18443https://doi.org/10.1088/0004-637X/801/1/29
http://iopscience.iop.org/article/10.1088/0004-637X/801/1/29