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Observations of Loss-Cone Pitch Angle Distributions of Solar Energetic Particles

Leske, R. A. and Cummings, A. C. and Cohen, C. M. S. and Mewaldt, R. A. and Labrador, A. W. and Stone, E. C. and Wiedenbeck, M. E. and Christian, E. R. and von Rosenvinge, T. T. (2014) Observations of Loss-Cone Pitch Angle Distributions of Solar Energetic Particles. In: Outstanding Problems in Heliophysics: From Coronal Heating to the Edge of the Atmosphere. Astronomical Society of the Pacific Conference Series. Vol.484. Astronomical Society of the Pacific , San Francisco, CA, pp. 117-122. ISBN 978-1-58381-852-7.

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Pitch angle distributions of solar energetic particles (SEPs) in interplanetary space sometimes exhibit a loss cone in which an incident beam of particles is partially mirrored; particles with large pitch angles are reflected while those with smaller pitch angles are not. Mirroring requires a magnetic field enhancement, but if the field strength is not large enough to turn around particles with the smallest pitch angles or if these particles scatter before reaching their more distant mirror points, a loss cone forms. Such distributions therefore provide information on the interplanetary environment far from the spacecraft. The Low Energy Telescopes onboard the twin STEREO spacecraft have detected loss-cone distributions in several SEP events. We present some of these and other interesting anisotropy observations, and discuss their implications for SEP transport. In particular, we find that the shapes of the pitch angle distributions generally vary with energy and species, with lower energy particles usually more anisotropic than higher energy particles. Comparison with theory may be used to determine the energy and rigidity dependences of the pitch angle diffusion coefficient.

Item Type:Book Section
Related URLs:
URLURL TypeDescription
Leske, R. A.0000-0002-0156-2414
Cummings, A. C.0000-0002-3840-7696
Cohen, C. M. S.0000-0002-0978-8127
Mewaldt, R. A.0000-0003-2178-9111
Labrador, A. W.0000-0001-9178-5349
Stone, E. C.0000-0002-2010-5462
Wiedenbeck, M. E.0000-0002-2825-3128
Christian, E. R.0000-0003-2134-3937
Additional Information:© 2014 Astronomical Society of the Pacific. This work was supported by the National Aeronautics and Space Administration (NASA) at Caltech and JPL under sub-contract SA2715-26309 from the University of California at Berkeley under NASA contract NAS5-03131, and by NASA award NNX08AK87G. We thank the PLASTIC (NASA contract NAS5- 00132), MAG, and SWEA investigators on STEREO for making their data publicly available, and the organizers of the 12th Annual International
Group:Space Radiation Laboratory
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Space Radiation Laboratory2014-13
Series Name:Astronomical Society of the Pacific Conference Series
Record Number:CaltechAUTHORS:20160624-085036638
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:68650
Deposited By: Deborah Miles
Deposited On:29 Jun 2016 19:03
Last Modified:09 Mar 2020 13:19

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