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Title: Solar energetic particle anisotropies and insights into particle transport

Abstract

As solar energetic particles (SEPs) travel through interplanetary space, their pitch-angle distributions are shaped by the competing effects of magnetic focusing and scattering. Measurements of SEP anisotropies can therefore reveal information about interplanetary conditions such as magnetic field strength, topology, and turbulence levels at remote locations from the observer. Onboard each of the two STEREO spacecraft, the Low Energy Telescope (LET) measures pitch-angle distributions for protons and heavier ions up to iron at energies of about 2-12 MeV/nucleon. Anisotropies observed using LET include bidirectional flows within interplanetary coronal mass ejections, sunward-flowing particles when STEREO was magnetically connected to the back side of a shock, and loss-cone distributions in which particles with large pitch angles underwent magnetic mirroring at an interplanetary field enhancement that was too weak to reflect particles with the smallest pitch angles. Unusual oscillations in the width of a beamed distribution at the onset of the 23 July 2012 SEP event were also observed and remain puzzling. We report LET anisotropy observations at both STEREO spacecraft and discuss their implications for SEP transport, focusing exclusively on the extreme event of 23 July 2012 in which a large variety of anisotropies were present at various times during the event.

Authors:
; ; ; ;  [1];  [2]; ;  [3]
  1. California Institute of Technology, Pasadena, CA 91125 (United States)
  2. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)
  3. NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
Publication Date:
OSTI Identifier:
22590919
Resource Type:
Journal Article
Journal Name:
AIP Conference Proceedings
Additional Journal Information:
Journal Volume: 1720; Journal Issue: 1; Conference: SOLAR WIND 14: 14. international solar wind conference, Weihai (China), 22-26 Jun 2015; Other Information: (c) 2016 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0094-243X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ANISOTROPY; ASTROPHYSICS; HEAVY IONS; INCLINATION; INTERPLANETARY MAGNETIC FIELDS; INTERPLANETARY SPACE; IRON IONS; LOSS CONE; MAGNETIC MIRRORS; MEV RANGE; MULTICHARGED IONS; OSCILLATIONS; SCATTERING; SOLAR CORONA; SOLAR PROTONS; SPACE VEHICLES; TELESCOPE COUNTERS; TURBULENCE

Citation Formats

Leske, R. A., E-mail: ral@srl.caltech.edu, Cummings, A. C., Cohen, C. M. S., Mewaldt, R. A., Labrador, A. W., Stone, E. C., Wiedenbeck, M. E., Christian, E. R., and Rosenvinge, T. T. von. Solar energetic particle anisotropies and insights into particle transport. United States: N. p., 2016. Web. doi:10.1063/1.4943841.
Leske, R. A., E-mail: ral@srl.caltech.edu, Cummings, A. C., Cohen, C. M. S., Mewaldt, R. A., Labrador, A. W., Stone, E. C., Wiedenbeck, M. E., Christian, E. R., & Rosenvinge, T. T. von. Solar energetic particle anisotropies and insights into particle transport. United States. https://doi.org/10.1063/1.4943841
Leske, R. A., E-mail: ral@srl.caltech.edu, Cummings, A. C., Cohen, C. M. S., Mewaldt, R. A., Labrador, A. W., Stone, E. C., Wiedenbeck, M. E., Christian, E. R., and Rosenvinge, T. T. von. 2016. "Solar energetic particle anisotropies and insights into particle transport". United States. https://doi.org/10.1063/1.4943841.
@article{osti_22590919,
title = {Solar energetic particle anisotropies and insights into particle transport},
author = {Leske, R. A., E-mail: ral@srl.caltech.edu 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 Rosenvinge, T. T. von},
abstractNote = {As solar energetic particles (SEPs) travel through interplanetary space, their pitch-angle distributions are shaped by the competing effects of magnetic focusing and scattering. Measurements of SEP anisotropies can therefore reveal information about interplanetary conditions such as magnetic field strength, topology, and turbulence levels at remote locations from the observer. Onboard each of the two STEREO spacecraft, the Low Energy Telescope (LET) measures pitch-angle distributions for protons and heavier ions up to iron at energies of about 2-12 MeV/nucleon. Anisotropies observed using LET include bidirectional flows within interplanetary coronal mass ejections, sunward-flowing particles when STEREO was magnetically connected to the back side of a shock, and loss-cone distributions in which particles with large pitch angles underwent magnetic mirroring at an interplanetary field enhancement that was too weak to reflect particles with the smallest pitch angles. Unusual oscillations in the width of a beamed distribution at the onset of the 23 July 2012 SEP event were also observed and remain puzzling. We report LET anisotropy observations at both STEREO spacecraft and discuss their implications for SEP transport, focusing exclusively on the extreme event of 23 July 2012 in which a large variety of anisotropies were present at various times during the event.},
doi = {10.1063/1.4943841},
url = {https://www.osti.gov/biblio/22590919}, journal = {AIP Conference Proceedings},
issn = {0094-243X},
number = 1,
volume = 1720,
place = {United States},
year = {Fri Mar 25 00:00:00 EDT 2016},
month = {Fri Mar 25 00:00:00 EDT 2016}
}