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ACR Proton Acceleration Associated with Reconnection Processes beyond the Heliospheric Termination Shock

Zhao, L.-L. and Zank, G. P. and Hu, Q. and Chen, Y. and Adhikari, L. and leRoux, J. A. and Cummings, A. and Stone, E. and Burlaga, L. F. (2019) ACR Proton Acceleration Associated with Reconnection Processes beyond the Heliospheric Termination Shock. Astrophysical Journal, 886 (2). Art. No. 144. ISSN 1538-4357. doi:10.3847/1538-4357/ab4db4.

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One of the curious observations from the Voyagers is that the intensity of anomalous cosmic rays (ACRs) did not peak at the heliospheric termination shock (HTS) but instead a short distance (within ~1 au) downstream of the HTS. One possible explanation is that the interaction of the wavy heliospheric current sheet with the HTS enhances magnetic reconnection and generates numerous small-scale magnetic flux ropes in the heliosheath immediately downstream of the HTS. Charged particles are accelerated in this region due to Fermi acceleration and the reconnection electric field. In this work, we provide observational evidence of the presence of magnetic flux ropes in the heliosheath region just downstream of the HTS using a wavelet analysis of the reduced magnetic helicity and Grad–Shafranov reconstruction techniques. The Zank et al. kinetic transport theory for particles propagating through the magnetic islands region is employed to fit the observed energetic proton intensities in the post-HTS region. Our modeling results agree reasonably well with the observations, which suggests that stochastic acceleration via reconnection processes can explain the ACR proton peak beyond the HTS.

Item Type:Article
Related URLs:
URLURL TypeDescription
Zhao, L.-L.0000-0002-4299-0490
Zank, G. P.0000-0002-4642-6192
Hu, Q.0000-0002-7570-2301
Chen, Y.0000-0002-0065-7622
Adhikari, L.0000-0003-1549-5256
leRoux, J. A.0000-0001-9199-2890
Cummings, A.0000-0002-3840-7696
Stone, E.0000-0002-2010-5462
Burlaga, L. F.0000-0002-5569-1553
Additional Information:© 2019 The American Astronomical Society. Received 2019 August 26; revised 2019 October 10; accepted 2019 October 13; published 2019 December 2. We acknowledge the partial support of the NSF EPSCoR RII-Track-1 Cooperative Agreement OIA-1655280, and partial support from an NSF/DOE Partnership in Basic Plasma Science and Engineering via NSF grant PHY-1707247, a NASA IBEX grant Sub0000167/80NSSC18K0237, NSF grant AGS 1650854 and NASA HGI-80NSSC19K0276, and a NASA grant NNX15AI65G. A.C. and E.S. are supported by NASA grant NNN12AA01C. L.F.B. acknowledges partial support from NASA/GSFC Contract 80GSFC19C0012.
Group:Space Radiation Laboratory
Funding AgencyGrant Number
Subject Keywords:Interplanetary particle acceleration; Solar magnetic reconnection; Termination shock; Solar wind
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Interplanetary particle acceleration (826); Solar magnetic reconnection (1504); Termination shock (1690); Solar wind (1534)
Record Number:CaltechAUTHORS:20191202-155700225
Persistent URL:
Official Citation:L.-L. Zhao et al 2019 ApJ 886 144
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:100153
Deposited By: Tony Diaz
Deposited On:03 Dec 2019 19:32
Last Modified:16 Nov 2021 17:51

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