摘要:

On January 24, 1969, an experiment on the Esro 1/Aurorae satellite recorded a flux over the central north pole that at times was a factor of 7 greater than that seen over the south pole. This asymmetry is discussed in relation to the interplanetary‐field direction measured at the same time by the Heos spacecraft, and comparison is made with the opposite asymmetrical configuration observed by Evans and Stone (1969) on November 2, 1967. From the evidence of two events it would appear that a southward interplanetary field plays a significant role in permitting direct access, while the magnitude and polarity of the asymmetry are determined by, respectively, interplanetary‐particle anisotropy and the ‘toward’ or ‘away’ nature o

ISSN:0148-0227    

DOI:10.1029/JA076i034p08159

年代:1971

数据来源: WILEY

摘要:

This paper describes studies of electrons between 10 ev and 9.9 kev in the solar wind. The transport of energy in the rest frame of the plasma is evaluated and shown to be parallel to the interplanetary magnetic field. The presence of electrons from solar events causes this energy‐flux densityE∥to exceed the heat flowH∥due to thermal electrons. In one such event, the observations are shown to be consistent with the solar‐electron observations made at higher energies. When observations are made at a point connected to the earth's bow shock by an interplanetary‐field line, a comparatively large energy flux along the field toward the sun is observed, butH∥remains outwardly directed during this time interval. In either situationH∥is found to be consistent with measurements made on Vela satellites by a different method. These values, less than 1×10−2ergs/cm2/sec, are sufficiently low to require modifications to the Spitzer‐Harm conductivity formula for use in s

ISSN:0148-0227    

DOI:10.1029/JA076i034p08165

年代:1971

数据来源: WILEY

摘要:

The vacuum transient response of the moon to a time‐varying spatially uniform magnetic field is determined for a lunar electrical conductivity model that was based on the harmonic analysis of Apollo 12 and Explorer 35 dayside magnetometer data. The transient response of the model is found to provide a plausible explanation of the behavior of the local vertical‐surface magnetic field for an Apollo 12 magnetometer darkside transient event. A model containing a conducting core and a highly conducting thin subsurface layer is presented, and its transient behavior is discus

ISSN:0148-0227    

DOI:10.1029/JA076i034p08174

年代:1971

数据来源: WILEY

摘要:

The ratio of specific heats in the solar‐wind plasma flow can be significantly different in the upstream and downstream regions of the earth's bow shock. On the basis of one‐fluid theory, the conservation equations of a normal magnetic shock are solved for compressional ratios of fluid parameters. It is found that jump ratios of fluid parameters are sensitively dependent on the ratio of the specific heats only in the downstream region. The appropriate ratio of specific heats of a thermodynamic analog to the reducible problems in the magnetohydrodynamic flow is investigated. This ratio will permit theoretical calculations to include the magnetic field for techniques such as hypersonic analog or inverse method in solving the blunt body probl

ISSN:0148-0227    

DOI:10.1029/JA076i034p08181

年代:1971

数据来源: WILEY

摘要:

We describe a physical model of the magnetic‐field structure that exists in the inner magnetosheath, near the earth‐sun line, and during highly disturbed periods. Magnetometer data are presented in a new format that uses the ordinary inclination‐declination coordinate system. Measurements of the inclination angle show how much the field lines are distorted from being tangent to the magnetopause. Distortions in the inclination angle sometimes exceed 45° in the low‐field regions that are believed to be associated with plasma condensations or clouds. The magnetic field is usually within 15° of being tangent to the magnetopause in high‐field regions, but some larger distortions have also been seen here. The clouds usually appear to be extended along the average magnetic‐field direction. A characteristic dimension for the observed structures is between several hundred and several thousand kilometers. Some large changes in the declination angle are not directly associated with clouds. These distortions imply that the field structure can rotate and still remain roughly tangent to the magnetopause. The large rotations are probably produced by changes in the solar wind and in the interplanetary magnetic field. Other declination angle changes are associated with clouds and provide evidence that field‐aligned currents can be present in the magnetosheath. Several sets of measurements were made very near the earth‐sun line. Some changes in the wave amplitude and frequency are noted in this region, but these changes can simply be the result of a reduction in the plasma‐flow speed. No unexpected effects that require new types of waves or instabilities have been found near

ISSN:0148-0227    

DOI:10.1029/JA076i034p08189

年代:1971

数据来源: WILEY

摘要:

Authors defining the daily variation range of the geomagnetic‐fieldHcomponent simply as ΔH=Hmax‐Hminhave recently reported several characteristics of the daily range and its correlation with interplanetary parameters. It is shown that for disturbed periods this definition is inappropriate and gives faulty estimates of the range owing toDstpollution. After proper correction forDsteffects, the genuineSqandSdwere evaluated for several stations in the longitude belt 60°–80°E for 1964 and particularly for the Imp 1 period (November 27, 1963, to February 15, 1964). The following conclusions were reached. (a) The quiet‐day daily variationSqis a predominantly daytime phenomenon. The day‐to‐day variability is caused by fluctuations inHmaxrather than inHmin. For equatorial locations, the variation is correlated withEregion apparent drift velocities and theBzcomponent (southward) of the interplanetary field. For midlatitudes, it is related toBxandBy. A very rough estimate indicates about 70% ionospheric and 30% magnetospheric contribution. (b) The disturbance daily variation can be conveniently divided into positive and negative components ΔSd+and ΔSd−. The ΔSd+is a morningtime increase from about midnight to 1000 LT and is similar to normalSqbut with flatter latitude dependence. Equatorial ΔSd+is related negatively to solar‐wind velocity, while midlatitude ΔSd+is related positively to plasma number density. The ΔSd−component has an almost latitude‐independent magnitude, develops between 1000 and 1400 LT at the equator and 1000 and 1800 LT at other latitudes, and is slightly negatively correlated with the standard deviation σBzof theBzcomponent. This component seems to be mostly magnetospheric, probably owing to a partial ring current centere

ISSN:0148-0227    

DOI:10.1029/JA076i034p08199

年代:1971

数据来源: WILEY

摘要:

The adiabatic theory is presented for charged particles moving in a region where the main component of the magnetic field reverses its direction. The unperturbed field configuration is one‐dimensional and involves two regions of uniform and opposite magnetic fields separated by a reversal region of small but finite extent. The adiabatic theory is capable of describing particle orbits when gradual spatial and/or temporal field variations are added to this configuration. Several applications are given. These include orbits during a null‐sheet compression, orbits in the sheets studied by Alfvén and Speiser, and orbits in the vicinity of the magnetic null line of the so‐called field‐reconnection

ISSN:0148-0227    

DOI:10.1029/JA076i034p08211

年代:1971

数据来源: WILEY

摘要:

The adequacy of the known source and loss processes to populate the inner radiation belt with protons is examined by calculating the equilibrium trapped‐proton distribution, which would result from decay of albedo neutrons, energy‐loss collisions, and radial diffusion by changes in the third adiabatic invariant. The strength of the neutron source and the rates of atmospheric energy loss are obtained from available theoretical and experimental data, and the radial‐diffusion coefficient is adjusted to give agreement between theory and experiment for equatorially trapped protons with first invariants between 200 and 3000 Mev gauss−1. Since there is strong evidence for additional loss mechanisms aboveL=1.8, this comparison is limited toL<1.7, and in the calculation all processes above that boundary are simulated by setting the fluxes at 1.7 equal to the experimental values. The flux intensities, energy spectrums, and radial distributions obtained by this theory are in good agreement with observations, and the radial‐diffusion coefficient required is consistent with diffusion coefficients derived by a variety of other methods. It is concluded that these processes are adequate to explain the gross characteristics of protons of the inner radiation belt, although off‐equatorial protons have not been considered and the solar‐cycle variations have not

ISSN:0148-0227    

DOI:10.1029/JA076i034p08223

年代:1971

数据来源: WILEY

摘要:

In the magnetotail at the distance of the Vela satellite orbits (r∼17 to 20RE) the plasma sheet becomes thin early in a polar magnetic substorm and then becomes thick again late in the substorm. Also, the thinning process consists not only of a reduction in the thickness of the plasma‐containing region but also of a decrease of the plasma energy density throughout the region, except perhaps very near the neutral sheet. In this paper the process of plasma‐sheet thinning is examined in substorms for which all‐sky photographs as well as ground‐based magnetograms were available. Thus the thinning process could be correlated with features of both the auroral substorm and the polar magnetic substorm. The following phenomena usually begin simultaneously to within the few‐minutes accuracy of the timing of the measurements: (a) plasma‐sheet thinning, (b) development of negative magnetic bays in the nightside auroral oval (independent of whether these develop rapidly or gradually), (c) development of positive magnetic bays at nightside low‐latitude stations, and (d) brightening and poleward motion of auroras in the nightside auroral oval. These results are entirely consistent with, although more detailed and precise, than our earlier reports that plasma‐sheet thinning and negative magnetic‐bay development in the auroral zone proceed together. This study does not help to resolve the presently existing controversy as to whether or not some magnetospheric substorms have a ‘development phase’ preceding the classical substorm ‘onset’ features, because none of the substorms examined seemed clearly to have a ‘development phase.’ After its onset, plasma‐sheet thinning continues, often for half an hour to an hour, as the aurora moves poleward. The poleward motion of the aurora may be indicative of the development of a new ‘hot’ plasma sheet within the old ‘cool

ISSN:0148-0227    

DOI:10.1029/JA076i034p08241

年代:1971

数据来源: WILEY

摘要:

The pitch‐angle distributions, energy spectra, and temporal and spatial variations of auroral electrons with energies from 40 ev to 100 kev were measured with the Twins 2 rocket payloads to an altitude of 800 km. Enhancements of electrons with energies of ∼5 kev, pitch angle α≤10°, and intensities of up to 5×10sparticles cm−2sec−1ster−1were observed occasionally. The enhancements were sometimes by a factor of 10, even while electrons with energies of ∼12 kev at these pitch angles showed no changes (nor did those with energies between ∼40 ev and 100 kev at 30°≤α≤60°). The bursts were thought to be temporal in origin, and they lasted for the minimum resolvable time of ∼0.1 sec up to times of several seconds. The altitude of the source of the bursts of field‐aligned electrons is believed to be less than 1RE, and their occurrence is not clearly related either to the ever‐present auroral continuum nor to the electrons with a few kiloelectron volts that cause auroral luminosity.We examine several existing theories of auroral particle acceleration and/or precipitation and show them each to be inadequate (as presently formulated) to individually explain all the observations. A potpourri model of adaptations of all these theories is shown to be adequate, but its reality is not otherwise established. Field‐line merging and diffusion by wave‐particle interactions are considered

ISSN:0148-0227    

DOI:10.1029/JA076i034p08258

年代:1971

数据来源: WILEY