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The Transition from Singly to Multiply-Charged Anomalous Cosmic Rays: Simulation and Interpretation of SAMPEX Observations

Barghouty, A. F. and Jokipii, J. R. and Mewaldt, R. A. (2000) The Transition from Singly to Multiply-Charged Anomalous Cosmic Rays: Simulation and Interpretation of SAMPEX Observations. In: Acceleration and Transport of Energetic Particles Observed in the Heliosphere. AIP Conference Proceedings. No.528. American Institute of Physics , Melville, N.Y., pp. 337-340. ISBN 1-56396-951-3.

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Multiply-charged anomalous cosmic rays (ACRs) can arise when singly-charged ACR ions are stripped of one or more of their electrons during their acceleration via, e.g., the process of diffusive shock-drift acceleration at the solar-wind termination shock. Recent measurements of the charge states of ACR neon, oxygen, and nitrogen by SAMPEX at 1 AU have shown that above ≈ 25 MeV/nucleon these ions are multiply charged. In addition, SAMPEX observations have also established that the transition from mostly singly-charged to mostly multiply-charged ACRs (defined as the 50% point) occurs at a total kinetic energy of ≈ 350 MeV. Preliminary simulations for ACR oxygen based on a theory of multiply-charged ACRs were able to show a transition energy at ≈ 300 MeV. However, the simulated intensity distribution among the various charge states was inconsistent with observations. This paper reexamines the predictions of the theory in light of new SAMPEX ACR observations and recently developed and refined estimates of hydrogen-impact ionization cross sections. Based on simulations for multi-species ACR ions, we find that the transition energy is only weakly dependent on characteristic transport parameters, and that the new ionization rates distribute the intensity among the charge states in a manner consistent with observations. The calculated transition energy is in excellent agreement with the measured value.

Item Type:Book Section
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Mewaldt, R. A.0000-0003-2178-9111
Additional Information:© 2000 American Institute of Physics. Issue Date: 15 September 2000. Work is supported by NSF grant no. 9810653 and NASA-JOVE NAG8-1208 (A.F.B.) and by NASA grants NAS5-30704 and NAG5-6912 at Caltech.
Group:Space Radiation Laboratory
Funding AgencyGrant Number
Subject Keywords:primary cosmic rays, interstellar matter, positive ions, electric charge, impact ionisation, cosmic ray nuclei, cosmic ray energy spectra
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Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory2000-27
Series Name:AIP Conference Proceedings
Issue or Number:528
Classification Code:PACS: 98.70.Sa
Record Number:CaltechAUTHORS:20111123-075314857
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Official Citation:The transition from singly to multiply-charged anomalous cosmic rays: Simulation and interpretation of SAMPEX observations A. F. Barghouty, J. R. Jokipii, and R. A. Mewaldt, AIP Conf. Proc. 528, 337 (2000), DOI:10.1063/1.1324334
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:27934
Deposited By: Ruth Sustaita
Deposited On:23 Nov 2011 16:15
Last Modified:09 Nov 2021 16:53

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