摘要:

Differential energy spectra for protons and helium covering the energy range 100–260 Mev/nucleon were obtained from balloon flights made each summer (1965–1969) at Churchill, Manitoba, with the aid of a Geiger‐tube hodoscope operated in conjunction with two scintillation elements used to measure (dE/dx) andE. Supplementary data from balloon flights at Minneapolis, Minnesota, and Sioux Falls, South Dakota, and from calibration exposures to protons and electrons were used to define backgrounds and to verify the predicted detector response. The observed proton spectra are characterized over a wide range of energy (30–300 Mev) by a simple relationship between cosmic‐ray intensityJand kinetic energyT:J = AT. The helium spectra also follow this law at solar maximum but rise less steeply near solar minimum. This characteristic behavior can be interpreted in terms of a simple model in which convection is balanced by adiabatic dec

ISSN:0148-0227    

DOI:10.1029/JA076i031p07445

年代:1971

数据来源: WILEY

摘要:

The cosmic‐ray neutron leakage flux and energy spectrum in the range 1–10 Mev were measured by a neutron detector on the Ogo 6 satellite from June 7 to September 30, 1969. The same detector simultaneously measured the total leakage flux, having 75% of its response to the leakage flux in the interval 1 kev to 1 Mev. For a neutron energy spectrum of the form AE−γin the range 1–10 Mev, the upper limit to γ for polar regions (Pc⪕0.3 Gv) was found to be 1.0 and for the equatorial regions (Pc⪖12 Gv) was 1.2. For the polar regions, the lower limit to γ was found to be 0.8. This energy spectrum at 1–10 Mev is slightly flatter than L. L. Newkirk predicted. The neutron fluxes at 1–10 Mev were 0.28±0.03 and 0.035±0.003 cm−2sec−1forPc⪕0.3 andPc⪖12 Gv, respectively. The ratios of the neutron flux at 1–10 Mev to the total neutron flux were 0.54±0.07 forPc

ISSN:0148-0227    

DOI:10.1029/JA076i031p07470

年代:1971

数据来源: WILEY

摘要:

A new kinetic model of the quiet solar wind is presented and compared with earlier exospheric, semikinetic, and hydrodynamical models. To have equal mean free paths for the protons and electrons at the baropause, the ratio of the proton temperature to the electron temperature is supposed to beTp(ho)/Te(ho) = 0.645. With the assumption that the trapped electrons are in thermal equilibrium with those emerging from the barosphere, the electric‐field distribution is calculated to cancel the electric current and space charge in the exospheric plasma. The bulk velocity, the density, the average electron and proton temperatures, and the energy flux, which are observed at 1 AU for quiet solar‐wind conditions, are well represented by such a kinetic model. The average electron temperature is nearly independent of the bulk velocity, whereas a positive correlation between the average proton temperature and the bulk velocity is found. Consequently it is suggested that in the interplanetary medium (r>6RS) no external heating mechanism is needed to explain the observed quiet solar‐wind properties. Finally, the electric‐field calculations in this kinetic model are found to be in reasonable agreement with the empirical electric‐field values deduced from observed coronal‐density d

ISSN:0148-0227    

DOI:10.1029/JA076i031p07479

年代:1971

数据来源: WILEY

摘要:

We consider a two‐component ‘model’ for the solar wind, in which the protons become collisionless beyondr0≥10RS, where they are already highly supersonic. The proton temperatures are found from the double adiabatic equation of state. The electrons are highly subsonic, and their temperature profile is prescribed ad hoc. Solar rotation is considered in a semi‐self‐consistent fashion. The momentum equations for the electrons and protons are solved subject to the conditions of quasi neutrality and zero charge efflux from the sun. The principal results are the following. (1) The proton thermal anisotropy is substantially reduced when solar rotation is considered. We findTp∥/Tp⊥<3 ifr0= 40RS, whileTp∥/Tp⊥10RSreduces the solar‐wind speed at the earth by 10–15%, thus worsening the disagreement between observations and the two‐fluid model. (5) The electron temperature profile in the supersonic region is the primary parameter determining flow acceleration there; we urge that the details of the electron energy balance, and the possibility of electro

ISSN:0148-0227    

DOI:10.1029/JA076i031p07491

年代:1971

数据来源: WILEY

摘要:

For a collisionless, heat‐conducting plasma, the distribution functionfis cylindrically symmetric about the direction of the magnetic field. If one assumesf= [1 +c∥h(c)]f0wheref0is the bi‐Maxwellian distribution function,c∥is the parallel component of the intrinsic velocityc, andhis an even function ofc, then the fourth moments offcan be expressed as simple functions of lower moments. Thus no higher moment terms appear in the third moment equations. The two third moment equations, which are obtained in a simple form, join other lower moment equations to form a closed set of moment equations. The new equations can be used to study the thermal anisotropy and the heat flux of the solar‐wind proton. A special case of the cylindrically symmetric distribution functionf= [1 +c∥h(c)]f0is found to resemble the proton distribution function reconstructed from solar‐wind data, and this resemblance justifies the assumption needed for decoupling the mom

ISSN:0148-0227    

DOI:10.1029/JA076i031p07503

年代:1971

数据来源: WILEY

摘要:

The temperature profile of the solar wind can be calculated from the energy equation by assuming that the velocity profile is known. When the logarithmic expansion rate of the solar wind is small, the heat‐flow equation can be integrated analytically. If the coronal temperature is sufficiently high, the energy equation has a critical solution in which the temperature vanishes at infinity. A quiet‐time temperature profile is calculated by using the observed data at the orbit of the ea

ISSN:0148-0227    

DOI:10.1029/JA076i031p07508

年代:1971

数据来源: WILEY

摘要:

Probable reverse and forward slow shocks were found in plasma and magnetic‐field data from Pioneer 8. The shocks were oblique and weak (Mach∼1.2). Numerous nonshocklike discontinuities were found withB1≠B2andn1≠n2. It was observed that discontinuities withB1≠B2,n1=n2seldom if e

ISSN:0148-0227    

DOI:10.1029/JA076i031p07516

年代:1971

数据来源: WILEY

摘要:

Theoretical constraints on the character of microscale fluctuations in the solar wind are examined. The microfluctuations could be either ‘discontinuities’ or more smoothly varying structures. If the fluctuations are waves, they are probably mostly Alfvén waves (or rotational discontinuities), and if they are stationary structures, they are tangential pressure balances (or tangential discontinuities). It is formally proved that a true analog of the small‐amplitude MHD ‘entropy wave’ (or contact discontinuity) does not exist for collisionle

ISSN:0148-0227    

DOI:10.1029/JA076i031p07522

年代:1971

数据来源: WILEY

摘要:

We calculate, by a perturbation analysis, the energy and momentum changes both of a single particle and of a distribution of particles moving in a transverse electromagnetic wave propagating parallel to the direction of the average magnetic field. It is shown that energy and momentum conservation of the particles and of the electromagnetic field leads to the same dispersion relation as has been obtained by Stix (1962) from solution of the Vlasov equation. More importantly, we are able to discuss the transfer of energy and momentum between particles and fields, in the context of stability or instability of the plasma. We emphasize that it is generally not sufficient to attempt to deduce the stability properties of a plasma from considerations of the energy gained or lost by the resonant particles alone. In general, one must also consider the additional constraint of momentum conservation and the effects of the nonresonant particles; this conclusion persists even in the limit of zero growth rate, when the resonant particles would be expected to play the dominant role. Two illustrations are provided. The real part of the frequency of the fire‐hose instability is shown to be determined by momentum conservation, whereas the growth rate follows from energy conservation. For the new proton‐resonant modes (Hollweg and Völk, 1970b), on the other hand, we find that the growth rate follows from momentum conservation, whereas energy conservation yields the real part of the frequency. We show that the earlier classification of the proton‐resonant modes in accord with the sign of (Ap±ωr/Ωp) is, in fact, a classification assigned in accord with the gain or loss of energy by the protons. The small‐wavelength extension of the fire hose leads to absorption of energy by the protons, and this mode could simultaneously cool the electrons and heat the protons in the solar wind near 1 AU; the other two proton‐resonant modes lead to loss of energy by the protons and would aggravate the discrepancy between the two‐fluid solar‐wind model and observation. Finally, it is shown that the small‐wavelength extension of the fire hose tends to reduce solar‐wind proton thermal anisotropies to the observed values only for frequencies less than about 4Ωp, whereas the other proton‐resonant instabilities lead in all instances to red

ISSN:0148-0227    

DOI:10.1029/JA076i031p07527

年代:1971

数据来源: WILEY

摘要:

Two static mathematical models of the open or Dungey model of the magnetosphere are constructed. The process of construction is similar to that for early closed magnetosphere models, such as the Taylor‐Hones model. The first model in fact is simply an addition of an interplanetary field in arbitrary direction to a Taylor‐Hones image dipole model. In order to preserve the shape of the magnetosphere at high latitudes, and to partially exclude the exterior field, another model is constructed with the magnetopause approximated by a diamagnetic sphere. We find that there are some interplanetary field lines connected to the earth for all orientations of the interplanetary field other than strictly northward, and that the maximum number of connected field lines occurs with a due southward field. For an average spiral hose angle of the interplanetary field, the dayside neutral point occurs on the magnetopause at about 10 o'clock local time. Dayside auroras, convection patterns, and other phenomena may exhibit symmetry about this local time. For a positive (negative) interplanetary field sector, energetic, anisotropic particle fluxes should have direct access to the northern (southern) polar caps, as is supported by many recent observati

ISSN:0148-0227    

DOI:10.1029/JA076i031p07542

年代:1971

数据来源: WILEY