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Possible Noise Nature of Elsasser Variable z(-) in Highly Alfvenic Solar Wind Fluctuations
Wang, X.; Tu, C. -Y.; He, J. -S.; Wang, L. -H.; Yao, S.; Zhang, L.; Tu, CY (reprint author), Peking Univ, Sch Earth & Space Sci, Beijing, Peoples R China.
Department空间科学部
Source PublicationJOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
2018
Volume123Issue:1Pages:57-67
ISSN2169-9380
Language英语
AbstractIt has been a long-standing debate on the nature of Elsasser variable z(-) observed in the solar wind fluctuations. It is widely believed that z(-) represents inward propagating Alfven waves and interacts nonlinearly with z(+) (outward propagating Alfven waves) to generate energy cascade. However, z(-) variations sometimes show a feature of convective structures. Here we present a new data analysis on autocorrelation functions of z(-) in order to get some definite information on its nature. We find that there is usually a large drop on the z(-) autocorrelation function when the solar wind fluctuations are highly Alfvenic. The large drop observed by Helios 2 spacecraft near 0.3AU appears at the first nonzero time lag r = 81s, where the value of the autocorrelation coefficient drops to 25%-65% of that at r = 0s. Beyond the first nonzero time lag, the autocorrelation coefficient decreases gradually to zero. The drop of z(-) correlation function also appears in the Wind observations near 1AU. These features of the z(-) correlation function may suggest that z(-) fluctuations consist of two components: high-frequency white noise and low-frequency pseudo structures, which correspond to flat and steep parts of z(-) power spectrum, respectively. This explanation is confirmed by doing a simple test on an artificial time series, which is obtained from the superposition of a random data series on its smoothed sequence. Our results suggest that in highly Alfvenic fluctuations, z(-) may not contribute importantly to the interactions with z(+) to produce energy cascade.
Indexed BySCI
Document Type期刊论文
Identifierhttp://ir.nssc.ac.cn/handle/122/6204
Collection空间科学部
Corresponding AuthorTu, CY (reprint author), Peking Univ, Sch Earth & Space Sci, Beijing, Peoples R China.
Recommended Citation
GB/T 7714
Wang, X.,Tu, C. -Y.,He, J. -S.,et al. Possible Noise Nature of Elsasser Variable z(-) in Highly Alfvenic Solar Wind Fluctuations[J]. JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS,2018,123(1):57-67.
APA Wang, X..,Tu, C. -Y..,He, J. -S..,Wang, L. -H..,Yao, S..,...&Tu, CY .(2018).Possible Noise Nature of Elsasser Variable z(-) in Highly Alfvenic Solar Wind Fluctuations.JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS,123(1),57-67.
MLA Wang, X.,et al."Possible Noise Nature of Elsasser Variable z(-) in Highly Alfvenic Solar Wind Fluctuations".JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS 123.1(2018):57-67.
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