A CASE-STUDY OF VERY LOW CROSS-HELICITY FLUCTUATIONS IN THE SOLAR-WIND

CORC > 北京大学 > 地球与空间科学学院

	A CASE-STUDY OF VERY LOW CROSS-HELICITY FLUCTUATIONS IN THE SOLAR-WIND
	TU, CY ; MARSCH, E
刊名	annales geophysicae atmospheres hydrospheres and space sciences
	1991
关键词	MHD TURBULENCE INNER HELIOSPHERE MAGNETOHYDRODYNAMIC FLUCTUATIONS STREAM STRUCTURE MAGNETIC-FIELD ALFVEN WAVES DISCONTINUITIES EVOLUTION DEPENDENCE SPECTRUM
英文摘要	Two periods of very low cross-helicity fluctuations observed by Helios 2 near 1 AU in 1976 have been studied in detail. It is shown that in both cases a nearly zero cross-helicity (sigma-c congruent-to 0) occurs together with an extremely low Alfven ratio (r(A) less-than-or-equal-to 0.2) and a -5/3 power-law for the turbulent energy spectra. The simultaneous occurrence of these features is apparently not influenced by compressible fluctuations. This conclusion is drawn from a comparison between different observed spectra calculated by using the instantaneous Elsasser variables, as well as smoothed Elsasser fields evaluated by means of the averaged magnetic field intensity and particle number density. Explaining the nature of the zero cross-helicity fluctuations poses a new theoretical problem, for which no satisfactory solution exists at the present time. However, a possible scenario is suggested in which the observed fluctuations mainly result from convecting static structures, not involving any velocity variations but merely "Magnetic Field Directional Turnings" (MFDTs). The associated evolutions of both the cross-helicity and the Alfven ratio in the inner solar system may qualitatively be explained by including these structures in extended solar wind turbulence models. The difficulties remaining with the scenario of MFDTs have also been pointed out.; Astronomy & Astrophysics; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences; SCI(E); 55; ARTICLE; 5; 319-332; 9
语种	英语
内容类型	期刊论文
源URL	[http://ir.pku.edu.cn/handle/20.500.11897/403436]
专题	地球与空间科学学院
推荐引用方式 GB/T 7714	TU, CY,MARSCH, E. A CASE-STUDY OF VERY LOW CROSS-HELICITY FLUCTUATIONS IN THE SOLAR-WIND[J]. annales geophysicae atmospheres hydrospheres and space sciences,1991.
APA	TU, CY,&MARSCH, E.(1991).A CASE-STUDY OF VERY LOW CROSS-HELICITY FLUCTUATIONS IN THE SOLAR-WIND.annales geophysicae atmospheres hydrospheres and space sciences.
MLA	TU, CY,et al."A CASE-STUDY OF VERY LOW CROSS-HELICITY FLUCTUATIONS IN THE SOLAR-WIND".annales geophysicae atmospheres hydrospheres and space sciences (1991).