National Aeronautics and Space Administration

Living With A Star

Targeted Research and Technology

Dynamics of Radiation Belt Electrons Associated with Solar Wind Variations

ROSES ID: NRA-02-OSS-01      Selection Year: 2003      

Program Element: Independent Investigation: LWS

Principal Investigator: Xinlin Li

Affiliation(s): University of Colorado at Boulder

Project Member(s):
Nelson, Laurence D Authorizing Official University of Colorado, Boulder
Temerin, Michael Alexey Collaborator Space Sciences Laboratory


The objective of the proposed work is to enhance our understanding of the physical mechanisms governing the variation of relativistic electrons in the inner magnetosphere. Outer radiation belt electrons vary on solar cycle, semiannual, and solar rotation time scales, and with geomagnetic storms. The basis of this proposal is the recent achievement of exciting new results in predicting the MeV electron flux at geosynchronous orbit 1-2 days in advance [Li et al., 2001a] based on measured solar wind parameters. This work provides a resolution to several long-standing mysteries of the variations of the MeV electron fluxes around geosynchronous orbit. The results have also raised new questions. For example, while the variation of MeV electrons at geosynchronous orbit can be attributed mostly to the variation of solar wind velocity itself, the variation of MeV electrons deeper inside the magnetosphere (L<5) is highly correlated with the Dst index, a measure of magnetic activity and storms [Li et al., 2001b], which itself is mostly dependent on the Bz magnetic component of the interplanetary magnetic field (IMF). What is the physical basis behind the different behaviors of MeV electrons in different regions? In particular, can our MeV electron prediction model (after modification) also make quantitative prediction of MeV electron flux inside geosynchronous orbit, even down to the International Space Station orbit? These are some of the questions to be addressed in the proposal. We propose to first make a better prediction of the electrons throughout the outer radiation belt based on trial-and-error, then to interpret it in terms of physical understanding. This method has been proved to be successful at the outer edge of the outer radiation belt and shall lead to a better understanding of the physical mechanisms governing the variations of relativistic electrons in the inner magnetosphere. [Li et al., 2001a] Li, X., M. Temerin, D. N. Baker, G. D. Reeves, and D. Larson, Quantitative Prediction of Radiation Belt Electrons at Geostationary Orbit Based on Solar Wind Measurements, Geophys. Res. Lett., vol. 28, 1887, 2001a. Li et al., 2001b] Li, X., D. N. Baker, S. G. Kanekal, M. Looper, and M. Temerin, Long Term Measurements of Radiation Belts by SAMPEX and Their Variations, Geophys. Res. Lett., vol. 28, 3827, 2001b.


Performance YearReferenceInvestigation TypeActions
1Li, Xinlin U CO - Dynamics of Radiation Belt Electrons Assoc...
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Performance YearReferenceActions
1Li, X.; Temerin, M.; (2004), The Predictability of the Ma...
1Li, X.; Temerin, M.; Oh, K.; (2006), Solar Wind and Geo...
1Tu, W.; Li, X.; Chen, Y.; Reeves, G.; Temerin, M.; ...

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