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Energetic Particle Anisotropies at the Heliospheric Boundary. II. Transient Features and Rigidity Dependence

Florinski, V. and Stone, E. C. and Cummings, A. C. and Le Roux, J. A. (2015) Energetic Particle Anisotropies at the Heliospheric Boundary. II. Transient Features and Rigidity Dependence. Astrophysical Journal, 803 (1). Art. No. 47. ISSN 0004-637X. doi:10.1088/0004-637X/803/1/47.

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In the preceding paper, we showed that large second-order anisotropies of heliospheric ions measured by the Voyager 1 space probe during the August 2012 boundary crossing event could be explained by a magnetic shear across the heliopause preventing particles streaming along the magnetic field from escaping the inner heliosheath. According to Stone et al., the penetration distance of heliospheric ions into the outer heliosheath had a strong dependence on the particle's Larmor radius. By comparing hydrogen, helium, and oxygen ions with the same energy per nucleon, these authors argued that this effect must be attributed to larger cyclotron radii of heavier species rather than differences in velocity. We propose that gradient drift in a nonuniform magnetic field was the cause of both the large second-order anisotropies and the spatial differentiation based on the ion's rigidity. A latitudinal gradient of magnetic field strength of about 10% per AU between 2012.7 and 2012.9 could have provided drift motion sufficient to match both LECP and CRS Voyager 1 observations. We explain the transient intensity dropout observed prior to the heliocliff using flux tube structures embedded in the heliosheath and magnetically connected to interstellar space. Finally, this paper reports a new indirect measurement of the plasma radial velocity at the heliopause on the basis of the time difference between two cosmic-ray telescopes measuring the same intensity dropout.

Item Type:Article
Related URLs:
URLURL TypeDescription
Florinski, V.0000-0001-5485-2872
Stone, E. C.0000-0002-2010-5462
Cummings, A. C.0000-0002-3840-7696
Additional Information:© 2015 American Astronomical Society. Received 2014 October 29; accepted 2015 February 12; published 2015 April 13. This work was supported, in part, by NASA grants NNX10AE46G, NNX11AO64G, NNX12AH44G, NNX13AF99G, and NNX14AF43G, by NSF grant AGS-0955700, and a cooperative agreement with NASA Marshall Space Flight Center NNM11AA01A. V.F. thanks Ed Roelof for a helpful discussion.
Group:Space Radiation Laboratory
Funding AgencyGrant Number
Subject Keywords:cosmic rays; ISM: magnetic fields; Sun: heliosphere; turbulence
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Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory2015-03
Issue or Number:1
Record Number:CaltechAUTHORS:20150518-085218576
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Official Citation:Energetic Particle Anisotropies at the Heliospheric Boundary. II. Transient Features and Rigidity Dependence V. Florinski et al. 2015 ApJ 803 47
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:57583
Deposited On:18 May 2015 19:52
Last Modified:10 Nov 2021 21:52

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