摘要:

The azimuthal propagation of solar protons with kinetic energies in the range ∼10 to ∼30 Mev is investigated by using observations made in the period December 1967 through August 1968 with University of Chicago instruments on board the earth satellite Imp 4 and the deep‐space probes Pioneer 6 and Pioneer 7, which were very widely separated from the earth during this period. In the period studied, nine solar‐proton events were observed simultaneously at all three spacecraft. In 6 of the 9 events discussed, the proton fluxes approached uniformity around the sun at the orbit of earth, and in 5 of these 6, the decay was divisible into 2 phases. During phase 1 azimuthal gradients were strong and the decay of the flux was fast, with exponential time‐decay constants in the range ∼10 to 20 hours. During phase 2, azimuthal gradients were weak or nonexistent and decay was slow, with time constants generally in excess of 40 hours. The times required for rise to maximum intensity and approach to uniformity, if interpreted in terms of the 1967 model of L. F. Burlaga, are found consistent with the existence of diffusion coefficients κ∥>4.3 × 1020cm²/sec and κ⊥∼ 1020to 1021cm²/sec at the orbit of earth. From observations of the energy spectra of the protons in these events, it is concluded that the azimuthal propagation process did not depend strongly on particle energy and that consequently there was no simple general dependence of the spectral form on azimuthal separation from the flare site. Though detailed interpretation and discussion of the theoretical implications of these results are deferred to a later paper, alternative models for the understanding of the observations

ISSN:0148-0227    

DOI:10.1029/JA077i022p03957

年代:1972

数据来源: WILEY

摘要:

The differential energy spectrum of solar protons in the range 0.3‐25 Mev obtained with the Injun 5 polar‐orbiting satellite is examined for several solar‐particle events. Of these, the events of February 25, 1969, April 26, 1969, and March 6, 1970, are discussed in detail. Except for the spectra observed early in the event, which are consistent with diffusive velocity dispersion effects, it is found that the majority of the events exhibit undistorted monotonically decreasing (∼E−γ) spectra within the energy range measured. The solar‐particle events of April 26, 1969, and March 6, 1970, produced spectra late in the event, implying energy degradation of the very‐low‐energy solar protons. By using one of the degraded spectra (March 8, 1970) it was found that the energy degradation could be explained by (1) postulating a temporary storage region ≳3–7RSabove the photosphere or (2) requiring continuous acceleration and emission of particles at the sun in the manner discussed by Parker (1965). Present theoretical and observational evidence indicates that the magnetic trapping is effective only to an altitude of about 1RSabove the photosphere, whereas our data suggest higher coronal trapping regions for the low‐energy protons. If it is assumed that closed‐field structures are necessary for particle confinement, one must conclude that alternative 2 is more plausible in explaining the observations. The effects of curvature and gradient drifts on the stored particles are computed by assuming a dipolelike trapping region extending to 1RSabove the photosphere. It is found that these drifts are ineffective in depleting the trapping region of low‐energy protons (1–10 Mev) and that for typical confinement times of ∼105sec most of this low‐energy component of flare‐generated particles should be lost to the phot

ISSN:0148-0227    

DOI:10.1029/JA077i022p03985

年代:1972

数据来源: WILEY

摘要:

The vertical geomagnetic cutoffs for cosmic‐ray protons are presented for seven different energy intervals between 1.2 and 39 Mev. These data, representing approximately 160 passes through the cutoff, were taken during 1967 and 1968, between 408‐ and 912‐km altitude, during times ofKp<1+. These passes provide nearly an order of magnitude more data during geomagnetically quiet times than have been previously reported at even one of these energies. In addition, the energy resolution of the instrument was significantly better than that of previous instruments. With these data, we find that the measured invariant latitudes for the cutoffs are 3° to 5° below previous calculations. We were unable to find any correlation of these observations with any physical phenomenon, including DST or the sun‐earth‐dipole angle. However, these data do indicate that even during ‘quiet’ times there are temporal changes in the geomagnetic field that cause the cutoff to fluctu

ISSN:0148-0227    

DOI:10.1029/JA077i022p03999

年代:1972

数据来源: WILEY

摘要:

The coordinate system generally used to describe the structure of solar‐particle profiles over the polar caps is based on invariant latitude and magnetic local time. By using trajectory integrations in a model geomagnetic field a new coordinate system is developed that is not based on internal geomagnetic‐field components alone but also takes into account the currents flowing in the magnetopause and the neutral sheet. It is shown that the new coordinate system is more relevant for the interpretation of high‐latitude energetic‐particle data than the old system and that its use makes it possible to calculate reconnection rates and scattering mean free paths in the tail. In a companion paper the results of the calculations performed here are applied to observations first to decide which magnetosphere model (open or diffusive) is appropriate and second to use the solar‐particle data for making measurements of important magnetospheric p

ISSN:0148-0227    

DOI:10.1029/JA077i022p04010

年代:1972

数据来源: WILEY

摘要:

It is shown that particle intensity structures bounded by magnetic discontinuities and convected past the earth with the solar wind favor an open‐tail interpretation. By using polar‐cap measurements of these discontinuities expressed in a new coordinate system described by Morfill (1972) the average reconnection rate between the interplanetary and magnetospheric field lines is calculated. Furthermore, the cross‐tail electric field, the mean free path in the tail, and the transverse component of power in the fluctuations of the tail magnetic field at the particle gyrofrequency are de

ISSN:0148-0227    

DOI:10.1029/JA077i022p04021

年代:1972

数据来源: WILEY

摘要:

The influence of the direction of the interplanetary magnetic field on the geomagnetic field at high latitudes is used to study the long‐term behavior of the sector structure during nearly four solar cycles. It is found that the rotation period of the sector structure varies from about 28.5 days in the beginning of a solar cycle to 27.0 days in the end. Also it is shown that short‐lived sectors rotate more slowly than long‐lived

ISSN:0148-0227    

DOI:10.1029/JA077i022p04027

年代:1972

数据来源: WILEY

摘要:

Kinetic and hydrodynamic descriptions of a collisionless solar wind proton gas are compared. Heat conduction and viscosity are neglected in the hydrodynamic formulation but are automatically included in the kinetic formulation. The fact that the results of the two models are very nearly the same indicates that heat conduction and viscosity are not important in the solar wind proton gas beyond approximately 0.1 AU. It is concluded that the hydrodynamic 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.

ISSN:0148-0227    

DOI:10.1029/JA077i022p04035

年代:1972

数据来源: WILEY

摘要:

The spiraling magnetic field of the sun reduces the electron conductivity κ by the factor cos²θ, where θ is the spiral field angle. For a variety of values of the density and temperature at the base of the corona, we compute one‐fluid solar‐wind models for thermal conductivities equal to κ and κ cos²θ. For both cases, the values of the computed solar‐wind parameters at the earth are compared with observ

ISSN:0148-0227    

DOI:10.1029/JA077i022p04042

年代:1972

数据来源: WILEY

摘要:

An analysis of the O I 1304‐ and 1356‐A data from Mariner 6 and 7 is presented, and the atomic oxygen concentration of the Martian atmosphere is estimated. Derived values of the parameters describing the sources of excitation differ considerably from previous estimates. A detailed statistical treatment is used in the analysis. At an exospheric temperature of 350°K the atomic oxygen concentration at 135 km is estimated to be between 0.5 and 1%. The likely source of the 1304‐A intensity is resonance scattering of solar 1304‐A photons. For the 1356‐A emission, the likely source is photodissociation of CO2. There is an indication of a diurnal variation of the Martian upper

ISSN:0148-0227    

DOI:10.1029/JA077i022p04052

年代:1972

数据来源: WILEY

摘要:

Backscattering of 0.86‐cm circularly polarized radiation by 29 regions on the moon has been measured with better signal‐to‐noise ratio than was available heretofore. Both circular polarizations were received. At a given angle of incidence, power received in the ‘expected’ polarization was greater for the highland regions than for the seas, by roughly 1 db. For moderately large angles of incidence ϕ, this return diminishes more rapidly than cos ϕ, though perhaps not as rapidly as it does at longer wavelengths. The cross section of the whole moon is 5% ± 2% of the geometric cross section; about 80% of the cross section is ascribable to diffuse scattering. The polarization ratio for the echoes varies smoothly with the angle of incidence, from 0.7 at the subradar point to 0.4 at 70°. The depolarization is the same for marial and highland regions, and at large angles of incidence it is the same as has been found at 23 cm and 68 cm by

ISSN:0148-0227    

DOI:10.1029/JA077i022p04069

年代:1972

数据来源: WILEY