July 29, 2015 to August 6, 2015
World Forum
Europe/Amsterdam timezone

Insights Into Particle Transport Obtained from Solar Energetic Particle Anisotropies

Aug 3, 2015, 11:45 AM
15m
Mississippi (World Forum)

Mississippi

World Forum

Churchillplein 10 2517 JW Den Haag The Netherlands
Oral contribution SH-EX Parallel SH 04 STEREO

Speaker

Richard Leske (California Institute of Technology)

Description

Solar energetic particle (SEP) pitch angle distributions are shaped by the competing effects of magnetic focusing and scattering as the particles travel through interplanetary space. Therefore, measurements of SEP anisotropies provide insight into particle transport and can probe interplanetary conditions at remote locations from the observer. The Low Energy Telescopes (LETs) onboard the twin STEREO spacecraft measure pitch angle distributions for protons and heavier ions at energies of about 2-12 MeV/nucleon. Using these instruments, we have observed a wide variety of SEP anisotropies, such as bidirectional flows within interplanetary coronal mass ejections, sunward-flowing particles when the spacecraft was magnetically connected to the back side of a distant shock, and loss cone distributions in which particles with large pitch angles magnetically mirror at an interplanetary field enhancement that is too weak to reflect particles with the smallest pitch angles. One of the more puzzling observations is unusual oscillations on a timescale of several minutes in the width of a beamed distribution at the onset of the very large 23 July 2012 SEP event. We present STEREO/LET anisotropy observations and discuss their implications for SEP transport. In particular, we note that the shapes of the pitch angle distributions often depend on energy and particle species, which may allow an empirical determination of the rigidity dependence of the pitch angle diffusion coefficient.
Registration number following "ICRC2015-I/" 360
Collaboration -- not specified --

Primary author

Richard Leske (California Institute of Technology)

Co-authors

Alan Cummings (California Institute of Technology) Allan Labrador (California Institute of Technology) Christina Cohen (California Institute of Technology) Edward Stone (California Institute of Technology) Eric Christian (NASA/Goddard Space Flight Center) Mark Wiedenbeck (Jet Propulsion Laboratory/Caltech) Richard Mewaldt (California Institute of Technology) Tycho von Rosenvinge (NASA/Goddard Space Flight Center)

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