An inviscid model of the solar wind

Whang, Y. C.; Chang, Chiung-Hsin

doi:10.1029/jz070i017p04175

Cited by 92 publications

(26 citation statements)

References 11 publications

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“…(Ogilvie and Scudder, 1978), Vela (Montgomery et al, 1968), and Voyager 2 (1.25-2.3 AU) (Sittler at al., 1978) of a = 0.3 : 0.08, 0.21 < a < 0.4, and a = 0.34 ± 0.16, respectively. This asymptotic radial exponent of electron temperature variation is greater than, but very nearly Parker 2/7 as suggested by the fluid solution of Noble andScarf (1963), (1964) and less than the Whang and Chang (1965) for the thermal electrons which provide the majority of the shielding neutralizing charge density for the ions. In this sense this steady state condition is nearly the requirement that a system of sufficient scale given sufficient time (steady state (t --)) will adjust itself so that the free charge is minimal.…”

Section: Observational Support Of Theoretically Expected Correlationsmentioning

confidence: 85%

A theory of local and global processes which affect solar wind electrons 2. Experimental support

Scudder¹,

Olbert²

1979

J. Geophys. Res.

158

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We have extended the theoretical considerations of Scudder and Olbert (1979) (hereafter paper I) to show from the microscopic characteristics of the Coulomb cross section that there are three natural subpopulations for plasma electrons: the subthermals with local kinetic energy E < kTc; the transthermals with kT < E < 7 kT and the extrathermals E > 7 kT c . We present experimental support from three experimental groups on three different spacecraft in the interplanetary medium over a radial range for the five interrelations projected in paper I between solar wind electron properties and changes in the interplanetary medium: 1) subthermals respond primarily to local changes (compressions and rarefactions) in stream dynamics; 2) the extrathermal fraction of the ambient electron density should be anti-correlated with the asymptotic bulk speed; 3) the extrathermal "temperature" should be anti-correlated with the local wind speed at 1 AU; 4) the heat flux carried by electrons should be anti-correlated with the local bulk speed; and 5) the extrathermal differ ential "temperature" should be nearly independent of radius within 1 AU.From first principles and the spatial inhomogeneity of the plasma we show that the velocity dependence of Coulomb collisions in the solar wind plasma produces a bifurcation in the solar wind electron distribution function at a transition energy, E*. This energy is theoretically shown to scale with the local thermal (tp core) temperature as E*(r) A 7 kT c(r).This scaling is observationally supported over the radial range from 0.45 to 0.9 AU by Mariner 10 data and IMP data acquired at 1 AU. The extra thermals, defined on the basis of Coulomb collisions, is synonymous with 3 the subpopulation previously labeled in the literature as the "halo" or shot" component. If the transition energy should be required to equal the polarization potential energy, e(r), for all radii beyond the observer, (as motivated by Mariner 10 data) the thermal electrons should obey a polytrope law with index Y = 7/6. In this circumstance the polarization potential is equal to the specific enthalpy: e4(r) = [y/(y-1)] kTc(r).This relation probably does not obtain in the corona, inside r < 10-20 RQ (of. Paper I). In the asymptotic spherically symmetric solar wind the inverse power law index for radial variation required for the thermal electrons should be a = 1/3 which is consistent with the recent in situ determinations between 0.45 and 03 AU. We thus provide the first self-consistent argument for associating E*(r) with e0(r). This theoretical asymptotic (r -) thermal electron temperature variation is between the conduction dominated (2Z7) and the inviscid solution (2/5). In the proximity of the ecliptic the ratio of the thermal electron Coulomb mean free path to scale length is shown to decrease with increasing radial distance. By contrast, over the solar poles the same asymptotic tempera ture and density variations iiply that the, Coulomb thermal mean free path will increase with increasing radial distance.A strai...

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Section: Observational Support Of Theoretically Expected Correlationsmentioning

confidence: 85%

A theory of local and global processes which affect solar wind electrons 2. Experimental support

Scudder¹,

Olbert²

1979

J. Geophys. Res.

158

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“…Parker's hydrodynamic description was subsequently extended by several authors to include an energy equation in place of the polytropic temperature law (Chamberlain, 1961(Chamberlain, , 1965Noble and Scarf, 1963;Scarf and Noble, 1965;Whang and Chang, 1965;Whang et al , 1966;Parker, 1964Parker, , 1965Schmidt, 1966, 1968;Konyukov, Hartle (1966;Hartle and Sturrock, 1968) and later extended by Hartle and Barnes (1970) to include the effects of proton heating. A two-fluid model including proton heating, as well as a proton thermal anisotropy, has recently been developed by Leer and Axford (1971), while Whang (1971a) has given an elegant description of the proton thermal anisotropy and the proton heat flux by adding a fourth moment equation to the standard hydrodynamic equations.…”

Section: Introductionmentioning

confidence: 99%

Collisionless solar wind protons: A comparison of kinetic and hydrodynamic descriptions

Leer

Holzer²

1972

J. Geophys. Res.

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Kinetic and hydrodynamic descriptions of a collisionless solar wind proton gas are compared. Heat conduction and viscosity are neglected in the hydr odynamic formulation but automatically included in the kinetic formulation.The results of the two models are very nearly the same, indicating that heat conduction and viscosity are not important in the solar wind proton gas beyond about 0. 1 AU. It is concluded that the hydr odynamic equations provide a valid description of the collisionless solar wind protons, and hence that future models of the quiet solar wind should be based on a hydrodynamic formulation.2.

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“…Later PARKER , 1964), NOBLE and SCARF (1963) and WHANG and CHANG (1965 solved both the momentum equation and the energy equation by assuming that heat transport is solely conductive. More recently STURROCK and HARTLE (1966) pointed out that energy partition times between electrons and protons under coronal conditions are large enough as to give substantial temperature differences between these two components.…”

mentioning

confidence: 99%