NEARLY INCOMPRESSIBLE MAGNETOHYDRODYNAMICS, PSEUDOSOUND, AND SOLAR-WIND FLUCTUATIONS

被引:107
作者
MATTHAEUS, WH
KLEIN, LW
GHOSH, S
BROWN, MR
机构
[1] APPL RES CORP, LANDOVER, MD 20895 USA
[2] NASA, GODDARD SPACE FLIGHT CTR, USRA, GREENBELT, MD 20771 USA
[3] CALTECH, DEPT PHYS, PASADENA, CA 91125 USA
关键词
D O I
10.1029/90JA02609
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
Recent theoretical studies have led to an improvement of our understanding of the behavior of a compressible magnetofluid with an adiabatic equation of state, in the limit of low plasma frame Mach number. Under certain assumptions the lowest-order behavior is that of incompressible magnetohydrodynamics (MHD), associated with small nonpropagating "pseudosound" density fluctuations. Departures from incompressibility include magnetoacoustic fluctuations, appearing at the same order as the pseudosound. In the present paper the simplest nearly incompressible MHD theory, with a polytropic equation of state, is reviewed, with an emphasis on observable consequences, particularly for solar wind turbulence. A central feature of the theory is the development of a relationship between the spectra of density fluctuations and of magnetic and velocity fluctuations. Here this relationship is extended to include uniform magnetic field effects, the possibility of anisotropic turbulence, and the influences of magnetic and cross helicities. Consequences of the theory, including Mach number scalings of density fluctuations and their wave number dependence, the anticorrelation of mechanical and magnetic pressure, and the reduction of density fluctuations in Alfvenic periods, are discussed in terms of Voyager solar wind observations. Finally, we present results of a simulation using a two-dimensional compressible MHD code that illustrate the appearance of similar anticorrelations.
引用
收藏
页码:5421 / 5435
页数:15
相关论文
共 40 条
[1]   DENSITY POWER SPECTRUM IN THE LOCAL INTER-STELLAR MEDIUM [J].
ARMSTRONG, JW ;
CORDES, JM ;
RICKETT, BJ .
NATURE, 1981, 291 (5816) :561-564
[2]  
Barnes A., 1979, SOLAR SYSTEM PLASMA, V1, P249
[3]  
Batchelor G. K., 1953, THEORY HOMOGENEOUS T
[4]   PRESSURE FLUCTUATIONS IN ISOTROPIC TURBULENCE [J].
BATCHELOR, GK .
PROCEEDINGS OF THE CAMBRIDGE PHILOSOPHICAL SOCIETY, 1951, 47 (02) :359-374
[5]  
Burlaga L.F., 1968, SOL PHYS, V4, P67, DOI [10.1007/BF00146999, DOI 10.1007/BF00146999]
[6]   PRESSURE-BALANCED STRUCTURES BETWEEN 1-AU AND 24-AU AND THEIR IMPLICATIONS FOR SOLAR-WIND ELECTRONS AND INTERSTELLAR PICKUP IONS [J].
BURLAGA, LF ;
SCUDDER, JD ;
KLEIN, LW ;
ISENBERG, PA .
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, 1990, 95 (A3) :2229-2239
[7]   MAGNETIC AND THERMAL PRESSURES IN SOLAR WIND [J].
BURLAGA, LF ;
OGILVIE, KW .
SOLAR PHYSICS, 1970, 15 (01) :61-&
[8]  
CHANDRASEKHAR S, 1967, INTRO STUDY STELLAR, pCH2
[9]   GROWTH OF CORRELATION IN COMPRESSIBLE TWO-DIMENSIONAL MAGNETOFLUID TURBULENCE [J].
DAHLBURG, RB ;
PICONE, JM ;
KARPEN, JT .
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, 1988, 93 (A4) :2527-2532
[10]   PRESSURE SPECTRA IN TURBULENT FREE SHEAR FLOWS [J].
GEORGE, WK ;
BEUTHER, PD ;
ARNDT, REA .
JOURNAL OF FLUID MECHANICS, 1984, 148 (NOV) :155-191