ACR Proton Acceleration Associated with Reconnection Processes beyond the Heliospheric Termination Shock
Abstract
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.
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.Attached Files
Published - Zhao_2019_ApJ_886_144.pdf
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Additional details
- Eprint ID
- 100153
- Resolver ID
- CaltechAUTHORS:20191202-155700225
- NSF
- OIA-1655280
- NSF
- PHY-1707247
- NASA
- 80NSSC18K0237
- NSF
- AGS-1650854
- NASA
- 80NSSC19K0276
- NASA
- NNX15AI65G
- NASA
- NNN12AA01C
- NASA
- 80GSFC19C0012
- Created
-
2019-12-03Created from EPrint's datestamp field
- Updated
-
2021-11-16Created from EPrint's last_modified field
- Caltech groups
- Space Radiation Laboratory