| Autor: |
J. A. Le Roux, G. M. Webb, O. V. Khabarova, L.-L. Zhao, L. Adhikari |
| Předmět: |
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| Zdroj: |
Astrophysical Journal; 12/10/2019, Vol. 887 Issue 1, p1-1, 1p |
| Abstrakt: |
New analytical steady-state and time-dependent solutions for the acceleration of energetic particles by contracting and reconnecting small-scale flux ropes (SMFRs) in the solar wind are presented. For this purpose, a telegrapher-type Parker transport equation was derived from the existing underlying focused transport equation. The solutions unify all SMFR acceleration mechanisms present in the transport equation, showing that SMFR acceleration by the reconnection electric field in the mixed-derivative transport term is constrained by and requires the presence of second-order Fermi SMFR acceleration. We explore the potential of these solutions in reproducing energetic proton flux enhancements and spectral evolution between ∼50 keV and 5 MeV in dynamic SMFR regions near large-scale reconnecting current sheets in the solar wind at Earth orbit. It is shown that second-order Fermi SMFR acceleration involving the variance in SMFR compression and incompressible parallel shear flow and confirmed that first-order SMFR Fermi acceleration, due to mean SMFR compression (successfully used before in data fits), are both workable options in reproducing observed flux amplification factors when using reasonable SMFR parameters. However, the predicted substantial quantitative differences in the spatial evolution of the accelerated spectra through the SMFR region might provide a way to distinguish between first- and second-order Fermi SMFR acceleration in observations. It is concluded that more detailed data analysis of SMFR parameters in SMFR acceleration events is needed before the relative role of first- and second-order SMFR acceleration mechanisms can be determined. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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