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Influence of the Solar Cycle on Turbulence Properties and Cosmic-Ray Diffusion
Zhao, L. -L.; Adhikari, L.; Zank, G. P.; Hu, Q.; Feng, X. S.
Department空间科学部
Source PublicationASTROPHYSICAL JOURNAL
2018
Volume856Issue:2Pages:94
ISSN0004-637X
Language英语
KeywordCosmic Rays Solar Wind Sun: Activity Turbulence
AbstractThe solar cycle dependence of various turbulence quantities and cosmic-ray (CR) diffusion coefficients is investigated by using OMNI 1 minute resolution data over 22 years. We employ Elsasser variables z(+/-) to calculate the magnetic field turbulence energy and correlation lengths for both the inwardly and outwardly directed interplanetary magnetic field (IMF). We present the temporal evolution of both large-scale solar wind (SW) plasma variables and small-scale magnetic fluctuations. Based on these observed quantities, we study the influence of solar activity on CR parallel and perpendicular diffusion using quasi-linear theory and nonlinear guiding center theory, respectively. We also evaluate the radial evolution of the CR diffusion coefficients by using the boundary conditions for different solar activity levels. We find that in the ecliptic plane at 1 au (1), the large-scale SW temperature T, velocity V-sw, Alfven speed V-A, and IMF magnitude B-0 are positively related to solar activity; (2) the fluctuating magnetic energy density < z(+/- 2)>, residual energy E-D, and corresponding correlation functions all have an obvious solar cycle dependence. The residual energy E-D is always negative, which indicates that the energy in magnetic fluctuations is larger than the energy in kinetic fluctuations, especially at solar maximum; (3) the correlation length lambda for magnetic fluctuations does not show significant solar cycle variation; (4) the temporally varying shear source of turbulence, which is most important in the inner heliosphere, depends on the solar cycle; (5) small-scale fluctuations may not depend on the direction of the background magnetic field; and (6) high levels of SW fluctuations will increase CR perpendicular diffusion and decrease CR parallel diffusion, but this trend can be masked if the background IMF changes in concert with turbulence in response to solar activity. These results provide quantitative inputs for both turbulence transport models and CR diffusion models, and also provide valuable insight into the long-term modulation of CRs in the heliosphere.
Indexed BySCI
Document Type期刊论文
Identifierhttp://ir.nssc.ac.cn/handle/122/6241
Collection空间科学部
Corresponding AuthorZhao, L. -L.; Adhikari, L.; Zank, G. P.; Hu, Q.; Feng, X. S.
Recommended Citation
GB/T 7714
Zhao, L. -L.,Adhikari, L.,Zank, G. P.,et al. Influence of the Solar Cycle on Turbulence Properties and Cosmic-Ray Diffusion[J]. ASTROPHYSICAL JOURNAL,2018,856(2):94.
APA Zhao, L. -L.,Adhikari, L.,Zank, G. P.,Hu, Q.,&Feng, X. S..(2018).Influence of the Solar Cycle on Turbulence Properties and Cosmic-Ray Diffusion.ASTROPHYSICAL JOURNAL,856(2),94.
MLA Zhao, L. -L.,et al."Influence of the Solar Cycle on Turbulence Properties and Cosmic-Ray Diffusion".ASTROPHYSICAL JOURNAL 856.2(2018):94.
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