Helios observational constraints on solar wind expansion
Helios observational constraints on solar wind expansion
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DOI：
10.1029/ja089ia08p06599
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发表时间：
1984-08
影响因子：
--
通讯作者：
E. Marsch;A. Richter
中科院分区：
文献类型：
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作者：
E. Marsch;A. Richter
Helios 粒子和 0.3 至 1 AU 之间的磁场观测用于确定表征太阳风的整体和内部能量状态的等离子体参数。实际上发现，在黄道平面上具有局部球对称性的时间平稳流中预期守恒的量在测量不确定性范围内是不变的。这些是由电子、质子和阿尔法合成的各向异性太阳风等离子体的总质量、能量和角动量通量。尽管个别物质具有非热速度分布，但总等离子体压力几乎是各向同性的（p/sub 垂直//p/sub 平行/ = 0.9）。总热通量除以质量通量 O/sub r//rhou/sub r/ 明显小于热速度平方 v/sub 平行.垂直//sup 2/ = rho/sub 平行.垂直//rho。由于这个原因，发现适当定义的多变指数..gamma..几乎为5/3，并且对日心距离和流速相当不敏感。该指数..gamma..不包括由于波湍流或外部热源而产生的项，而是仅基于总粒子热通量。这些观测结果表明，超过 0.3 AU 的热通量在观测上太小，不足以导致强烈偏离绝热性。太阳风膨胀可以用“单个粒子”在束缚引力势和加速热势（焓和热通量）和磁旋转（轴动能和坡印廷通量）势中移动的术语来构想。这些电势的径向分布来自观察。« less
Helios particle and magnetic field observations between 0.3 and 1 AU are used to determine plasma parameters that characterize the bulk and internal energy state of the solar-wind. Quantities expected to be conserved in a time-satationary flow with local spherical symmetry in the ecliptic plane are actually found to be invariant within measurement uncertainties. These are the total mass, energy, and angular momentum fluxes for the anisotropic solar wind plasma composited by electrons, protons, and alphas. Although individual species have nonthermal velocity distributions, the total plasma pressure is almost isotropic (p/sub perpendicular//p/sub parallel/ = 0.9). The total heat flux divided by the mass flux O/sub r//rhou/sub r/ is markedly smaller than thermal speeds squared v/sub parallel.perpendicular//sup 2/ = rho/sub parallel.perpendicular//rho. By this reason an appropriately defined polytropic index ..gamma.. is found to be almost 5/3 and rather insensitive to heliocentric distance and flow speed. This index ..gamma.. does not include terms due to wave turbulence or external heat sources but is solely based on the total particle heat flux. These observational findings indicate that the heat flux beyond 0.3 AU is observationally too small to cause a strong departure from adiabaticity. The solar wind expansion may be conceived in termsmore » of a ''single particle'' moving in the binding gravitational potential and in the accelerating thermal (enthalpy and heat fluxes) and magnetorotational (aximuthal kinetic energy and Poynting flux) potentials. The radial profiles of these potentials are derived from observations.« less