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Ionization Processes in the Heliosphere - Rates and Methods of their Determination

Ruciński, D. and Cummings, A. C. and Gloeckler, G. and Lazarus, A. J. and Möbius, E. and Witte, M. (1996) Ionization Processes in the Heliosphere - Rates and Methods of their Determination. Space Science Reviews, 78 (1-2). pp. 73-76. ISSN 0038-6308. doi:10.1007/BF00170794.

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The rates of the most important ionization processes acting in interplanetary space on interstellar H, He, C, O, Ne and Ar atoms are critically reviewed in the paper. Their long-term modulations in the period 1974 – 1994 are reexamined using updated information on relevant cross-sections as well as direct or indirect data on variations of the solar wind/solar EUV fluxes based on IMP 8 measurements and monitoring of the solar 10.7 cm radio emission. It is shown that solar cycle related variations are pronounced (factor of ∼ 3 between maximum and minimum) especially for species such as He, Ne, C for which photoionization is the dominant loss process. Species sensitive primarily to the charge-exchange (as H) show only moderate fluctuations ∼ 20% around average. It is also demonstrated that new techniques that make use of simultaneous observations of neutral He atoms on direct and indirect orbits, or simultaneous measurements of He^+ and He^(++) pickup ions and solar wind particles can be useful tools for narrowing the uncertainties of the He photoionization rate caused by insufficient knowledge of the solar EUV flux and its variations.

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Cummings, A. C.0000-0002-3840-7696
Additional Information:© 1996 Springer. Provided by the NASA Astrophysics Data System. The authors are grateful to M. Allen for supplying us with new data on photoionization cross-sections compiled by him. We thank also M. Gruntman for drawing our attention to and support in collecting the most recent data on charge-exchange cross-sections. D.R. was supported by grant No.2 P03C.004.09 from the Committee for Scientific Research (Poland). This work was also supported in part through NASA contract NAS7-918, NSF Grant INT-911637, NASA Grant NAGW- 2579. The SWICS/Ulysses work contributing to the paper was supported by the NASA/ JPL contract 955460 and the Swiss National Science Foundation.
Group:Space Radiation Laboratory
Funding AgencyGrant Number
Committee for Scientific Research (Poland)2 P03C.004.09
Swiss National Science Foundation (SNSF)UNSPECIFIED
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Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory1996-24
Issue or Number:1-2
Record Number:CaltechAUTHORS:20140703-220236671
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:46840
Deposited By: Deborah Miles
Deposited On:23 Jul 2014 17:27
Last Modified:10 Nov 2021 17:29

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