DOI: 10.1002/2017JA025014
Scopus记录号: 2-s2.0-85047515748
论文题名: Rarefaction of the Very Slow (<350 km/s) Solar Wind in Cycle 24 Compared With Cycle 23
作者: Tokumaru M. ; Shimoyama T. ; Fujiki K. ; Hakamada K.
刊名: Journal of Geophysical Research: Space Physics
ISSN: 21699380
出版年: 2018
卷: 123, 期: 4 起始页码: 2520
结束页码: 2534
语种: 英语
英文关键词: interplanetary scintillation
; solar cycle variation
; solar wind
英文摘要: We investigate long-term variation of the very slow solar wind (VSSW), whose speed is less than 350 km/s, during the period between 1997 and 2015, that is, Cycles 23 and 24, using interplanetary scintillation measurements, which enable determination of the global distribution of the flow speed and the electron density fluctuation level ΔNe. We find that the occurrence rate of VSSW increases in the maximum phase of the solar cycle, and it was mostly associated with high ΔNe in Cycle 23. However, the VSSW is found to be more associated with low ΔNe in Cycle 24. This fact is consistent with an increased occurrence of the low-density VSSW observed in situ in Cycle 24. These facts, which are considered to be a manifestation of weak solar activity in this cycle, suggest that the VSSW has become significantly rarefied in recent years. We identify the source region of the VSSW on the photosphere using a potential field analysis and examine the magnetic field properties of the VSSW source. We find that the low-ΔNe VSSW is associated with a smaller expansion factor and possibly a slightly weaker photospheric field strength than the high-ΔNe VSSW. The results obtained here may suggest that more open magnetic field areas producing the VSSW in Cycle 24 are formed in the quiet Sun region, which is associated with a lower mass flux supply into the corona, than those in Cycle 23. ©2018. American Geophysical Union. All Rights Reserved. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/114147
Appears in Collections: 气候减缓与适应
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作者单位: Institute for Space-Earth Environmental Research, Nagoya University, Nagoya, Japan; Department of Natural Science and Mathematics, Chubu University, Kasugai, Japan
Recommended Citation:
Tokumaru M.,Shimoyama T.,Fujiki K.,et al. Rarefaction of the Very Slow (<350 km/s) Solar Wind in Cycle 24 Compared With Cycle 23[J]. Journal of Geophysical Research: Space Physics,2018-01-01,123(4)