摘要:

During the geomagnetic storm of March 16–17, 1976, observations were made of precipitating protons, alpha particles, and heavy ions by two counter telescopes aboard the low‐altitude S3‐2 satellite. These observations are presented in this paper and their significance discussed. Briefly, a two‐zone precipitation region is observed on the nightside, atL≈ 2.7 andL≈ 4.0 with an α/pratio ∼8 × 10−3in the low‐latitude region and ∼9 × 10−4at higher latitude at 0.4 MeV/nucleon. The heavier ions, CNO nuclei, are seen in the low‐latitude zone with a CNO/α ratio of ∼

ISSN:0148-0227    

DOI:10.1029/JA084iA01p00079

年代:1979

数据来源: WILEY

摘要:

A mathematical model describing radial diffusion, with violation of the third adiabatic invariant and with local losses, is applied to the Pioneer 10 and 11 observations of omnidirectional integral intensities of electrons with energyE>21 MeV. Local losses outsideL=3 are much stronger than synchrotron losses but weaker than the losses one would expect for strong pitch angle diffusion. If radial diffusion is driven by ionospheric winds, as was suggested by Brice and McDonough (1973), we find that the theoretical solution which best fits the data requires that the radial diffusion coefficientD≈ 3 × 10−9L³ s−1and the lifetime against local losses, τ, is approximately a few million

ISSN:0148-0227    

DOI:10.1029/JA084iA01p00087

年代:1979

数据来源: WILEY

摘要:

The existence of large‐scale motions within the earth's magnetosphere and that of a long magnetotail were predicted in 1960 as results of a hypothetical frictional interaction between the solar wind and the geomagnetic field. The boundary layer model of this interaction involves the flow of magnetosheath plasma in a magnetospheric boundary layer. The flow is across magnetic field lines, and so the layer must be polarized, with a space charge field nearly balancing the induction field . The space charge tends to discharge through the ionosphere, thus providing some magnetic and related activity as well as the Lorentz frictional force. This closed magnetosphere model has been largely neglected in favor of the reconnection model but is now strongly supported by observational results and their interpretation as follows. (1) The evidence for the reconnection model, increasing activity with a southward interplanetary field and invasion of the polar caps by flare particles, is shown to be equally compatible with the closed field model. (2) The magnetotail grows by the motions of closed flux tubes through the dawn and dusk meridians, a process which depends on the nature of the boundary between magnetosphere and magnetosheath plasmas and perhaps also on the solar wind dynamo. Both of these features depend, in turn, on the direction of the interplanetary magnetic field. (3) Closed field lines entering the tail may be stretched to a few tens of earth radii and then contract back to the corotating magnetosphere. Others enter the long tail and are stretched to hundreds of earth radii and so are pervious to fast solar particles. (4) A new model of the magnetospheric substorm involves the entry of closed field lines into the tail and their rapid return to the corotating magnetosphere. The return is due, first, to the release of their trapped plasma as it becomes electrically polarized and, second, to mounting magnetic and plasma stresses in the inflated magnetotai

ISSN:0148-0227    

DOI:10.1029/JA084iA01p00093

年代:1979

数据来源: WILEY

摘要:

Three‐dimensional distributions for 24‐ to 44.5 keV protons (ions) are presented from the Isee 1 medium‐energy particles instrument during a magnetopause traversal at ∼0145:00 hours UT on November 20, 1977. The use of these data and simple particle orbit geometry allows us to infer magnetopause boundary location, orientation, and velocity. The results are consistent with both overall boundary motions toward and away from the earth at velocities of 10–20 km/s and the presence of a surface wave on the boundary. For the case analyzed, the boundary appears stable and well defined, being capable of supporting trapped type distributions (conservation of the first and second adiabatic invariants) within a fraction (≲0.3 ρ) of a gyroradius from the magnetosheath field where no trapping

ISSN:0148-0227    

DOI:10.1029/JA084iA01p00101

年代:1979

数据来源: WILEY

摘要:

Velocity biasing can lead to erroneous interpretation of temperature and density evolution of the solar wind. It is argued that possibly there is no difference in the physics of the slow and fast components (Helios 1). Finally, it is suggested to use T/u², in order to reduce the strong dependence of temperature on velocity

ISSN:0148-0227    

DOI:10.1029/JA084iA01p00105

年代:1979

数据来源: WILEY

ISSN:0148-0227    

DOI:10.1029/JA084iA01p00107

年代:1979

数据来源: WILEY

摘要:

The solar proton event of April 16, 1970 was monitored by Vela satellites, of orbit r=18 RE, in the solar wind and high‐latitude magnetotail (lobe). Intensity structure at ≲1 MeV indicates a delay of 85–102 min in access of protons to near the center of the north lobe, corresponding to entry points at 340–370 REfrom the earth. In three sequential periods, of 16, 181, and 124 min duration, the average intensity in the north lobe was lower, higher, and lower, respectively, than that in interplanetary space by factors which varied from 2 to 5. These reversals were a consequence of reversals in field‐aligned anisotropy in interplanetary space, the interplanetary magnetic field remaining southward. Pitch angle distributions were measured in three dimensions in interplanetary space and in the north lobe. In the lobe the distributions were essentially isotropic at r=18 RE. Comparison is made with theoretical propagation of solar particles along field lines in an open tail model, under the following conditions along a trajectory: (1) adiabatic motion all the way (Liouville theorem)—the ‘adiabatic access model’ or (2) isotropization at the magnetopause followed by adiabatic motion—the ‘nonadiabatic access model.’ Neither mode of access explains the observations adequately. A hybrid mode is proposed, in which a minimal amount of scattering occurs as particles enter the tail, followed by amplification (attenuation) of intensity as the pitch distribution is transformed to near 18 REin the favored (unfavored) lobe. In this mode a large part of the isotropization at Vela orbit is accomplished by the Liouville transformation, since particles entering the tail beyond ≈100 REwill see an increase in magnetic field by a factor of 3 as they propagate along the tail. The amount of scatter at the magnetopause is estimated to be Δµ(rms)=0.3, where µ is cosine of pitch angle. Intensity discrepancies later in the event are interpreted as (1) a brief adjustment in the topology of the magnetotail in which the field line through Vela 6A changed its exit point to ≈530 RE, compared to ≈350 REbefore and ≈420 REafter and (2) interconnection between interplanetary and magnetotail fields determined by the radial component of the interplanetary field, as distinct from the southward component during the main portion of the event (the particle access window, however, remained at t

ISSN:0148-0227    

DOI:10.1029/JA084iA01p00109

年代:1979

数据来源: WILEY

摘要:

The cosmic ray modulation in the rigidity range 0.34

ISSN:0148-0227    

DOI:10.1029/JA084iA01p00120

年代:1979

数据来源: WILEY

摘要:

The day‐to‐day variations of the total vector anisotropy observed by neutron monitors are discussed. A model is developed to explain these variations in terms of counting‐statistics noise, convection in the solar wind, scattering of cosmic rays in the interplanetary magnetic field, and particle drifts. Both the amplitude and the phase variations of the Deep River neutron monitor diurnal anisotropy are shown to agree with the model's predictions. A novel prediction, confirmed by the observations, is the tendency for afternoon hour anisotropies to be larger than evening hour anisotr

ISSN:0148-0227    

DOI:10.1029/JA084iA01p00125

年代:1979

数据来源: WILEY

摘要:

We have studied the correlations between the width of the U‐shaped peak flux density spectra of solar radio bursts and the slope of the associated proton energy spectra observed by satellites. We find the wider radio spectra U's lead to shallow proton energy slopes (harder spectrum), while narrower U's lead to steeper slopes (softer spectrum). Out of the straight line, power law, and exponential forms used to study the correlations, the power law form yields the best correlation (r≈ 0.77). This leads to a practical prediction scheme which can be used in real time for forecasting the spectral character of the protons that can be expected to arrive in the vicinity of the earth on the basis of the continuously monitored radio burst d

ISSN:0148-0227    

DOI:10.1029/JA084iA01p00131

年代:1979

数据来源: WILEY