Solar energetic particle anisotropies and insights into particle transport

Journal Article · Fri Mar 25 00:00:00 EDT 2016 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.4943841· OSTI ID:22590919

Cummings, A. C.; Cohen, C. M. S.; Mewaldt, R. A.; Labrador, A. W.; Stone, E. C. ^[1]; Wiedenbeck, M. E. ^[2]; Christian, E. R.; Rosenvinge, T. T. von ^[3]

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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)

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.

• OSTI ID: 22590919
• Journal Information: AIP Conference Proceedings, Vol. 1720, 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); ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

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