摘要:

The publishedL= 5 equatorial magnetosphere particle and field data from the April 18, 1965, geomagnetic storm are reanalyzed in the context of the drift mirror instability theory developed by Hasegawa. These data, together with previously unpublished electron pitch‐angle data, are shown to satisfy the requirements and consequences of the instability. Additional particle data observed during a 1967 substorm by an experiment on ATS 1 are also presented to show that the observation of the April 18 instability was not an isolated occurrence in the magnetosphere. The data also contain evidence for electron heating during the time of the instabilit

ISSN:0148-0227    

DOI:10.1029/JA074i024p05565

年代:1969

数据来源: WILEY

摘要:

A method is presented for solving the problem of confining solar flare particles to definite sectors of the solar magnetic field by the use of Laplace transform coordinates. An analysis of solar events dating back to 1956 indicates that the radial diffusion coefficientDr=Mrrβis applicable in all cases for a value of β ≃ 1. A lateral diffusion coefficientDθ=Mθrais postulated for the interplanetary medium with α = 1, 2. It is shown that the ratio ofMθ/Mrmust be of the order of 0.01 or less for both power laws in order to confine the particles to an initial ejection angle θ0. The concept of a solar flare, initially confined to a small ejection angle, developing into a large‐scale flare later in the event is found to be untenable. The theoretical equations predict that large‐scale flares must originate with large ejection angles. The maximum value of the ejection angle is estimated to be about 90°. The theoretical equations predict that the graph of log (nt3/(2‐β)) versus 1/tyields a straight line similar to the simple isotropic model, and this is confirmed by the experimental evidence. The theory further predicts the existence of sharp flare boundaries that have been experimentally detected for very low energy flares. It is shown that failure to adopt a suitable boundary condition at the sun in the mathematical solution leads to e

ISSN:0148-0227    

DOI:10.1029/JA074i024p05579

年代:1969

数据来源: WILEY

摘要:

New data from underground mu‐meson telescopes, at depths of 40 MWE, in the northern and southern hemispheres are presented. Analysis in sidereal time of three years of data from the northern hemisphere telescopes and two years of data from the southern hemisphere telescopes confirm that a maximum intensity is observed near 18 hours sidereal time for telescopes pointing into the northern hemisphere and near 06 hours sidereal time for telescopes pointing into the southern hemisphere, in agreement with previous observations by others. A model is proposed in which just such a ‘sidereal’ variation can be produced in the vicinity of the earth as a result of the radial cosmic‐ray density gradient and the interplanetary magnetic field; the model is tested by dividing the cosmic‐ray data according to the direction of the interplanetary field and performing the same sidereal time analysis on these data. The results confirm the principal features of the model and demonstrate that the ‘sidereal’ variation can be produced in the inner solar system, correctly predicting the observed times of maximum in the northern and southern hemispheres, without recourse to assumptions about anisotropies of the particle flux in g

ISSN:0148-0227    

DOI:10.1029/JA074i024p05591

年代:1969

数据来源: WILEY

摘要:

A Forbush decrease of about 4% was recorded on January 26 by the Mt. Washington cosmic‐ray neutron monitor after a sc magnetic storm. Since measurements outside the magnetosphere of both the magnetic field (Explorer 33) and the cosmic‐ray flux for protons withE>14 Mev (Pioneer 8) are available, geomagnetic perturbations of the local cosmic‐ray flux are separated from changes of the flux in space. The main phase of the Forbush decrease at 2100 UT on January 26 followed a disturbance in the magnitude and direction of the interplanetary magnetic field at about 1430 UT. The observed ratio of the amplitude for the cosmic‐ray decrease in space to that recorded at Mt. Washington was 1.7. An east‐west anisotropy of ∼4% persisted in the cosmic‐ray flux for 16 hours, the intensity being depressed west of the earth‐sun line. For about six hours around 1800 UT there was a north‐south anisotropy of 4%, the net flux directed southward. The anisotropy measured by the Pioneer detector (E>60 Mev) after the Forbush decrease is greater in magnitude and persists longer than indicated by neutron monitors. These features are related to the quasi‐stationary cosmi

ISSN:0148-0227    

DOI:10.1029/JA074i024p05599

年代:1969

数据来源: WILEY

摘要:

The measurements of the interplanetary magnetic field taken with the Mariners 2, 4, and 5, and OGO 5 cover several parts of the interval from September 1962 to the present and several paths through the region between 0.7 and 1.5 AU and between ±7.3° in solar equatorial latitude. From an analysis of these measurements we find evidence for a distinct dominant polarity effect in the magnetic field. Specifically, the dominant polarity of the field was inward (toward the sun) at heliographic latitudes above the solar equatorial plane and outward (away from the sun) at latitudes below this plane. Magnetographs of the polar regions of the sun indicate that the dipolar component of the sun's field has been inward over the northern hemisphere and outward over the southern hemisphere since the last maximum in solar activity, which occurred in 1958. Our results suggest that over most of a solar cycle, thedominantpolarity of the interplanetary field in either the northern or southern hemisphere of interplanetary space is just that of the dipolar component of the sun's field in the same hemispher

ISSN:0148-0227    

DOI:10.1029/JA074i024p05611

年代:1969

数据来源: WILEY

摘要:

There are two possible heat sources for the sunlit ionosphere of Venus, photoionization of the neutral species, mainly CO2, and influx from the solar wind. It is shown that the electron temperature should be substantially higher (at least ∼500°K) than the temperature of the neutral atmosphere at altitudes above 250 km but that the ion temperature probably does not greatly exceed that of the neutral species. The significance of the solar wind as a heat source is also discuss

ISSN:0148-0227    

DOI:10.1029/JA074i024p05623

年代:1969

数据来源: WILEY

摘要:

Mixing ratios of 2 × 10−4and 1 × 10−4for He4and Ar40, respectively, in a 100% Co2Mariner 5 model of the Cytherean lower atmosphere are derived by assuming that the He4and Ar40are secondary in origin and result entirely from radioactive disintegration with subsequent outgassing from the planet. Production rates on Venus are assumed equal to those for the earth. Thermal escape of He4is shown to be negligible, and other loss mechanisms are assumed unimportant. Concentration of these gases in the upper atmosphere of Venus are calculated from the mixing ratios and a turbopause at 6180 km radius. The He4concentration in the upper atmosphere is a factor of 10 larger than the minimum value estimated byMcElroy and Strobel[1969] to account for the observed nighttime ionosphere and is about a factor of 4 larger than that suggested byWhitten[1969] to explain the observed daytime ionosphere. This degree of agreement among three separate approaches strengthens the possibility that He4is a dominant constituent in the upper atmosphere of Venus and also implies that loss of He4on Venus by plasma expansion is unimportant. He4will be the dominant constituent out to a radius of about 7600 km if H2is present at the upper limit suggested byMcElroy and Hunten[1969] and out to a radius of about 8700 km if H2is negli

ISSN:0148-0227    

DOI:10.1029/JA074i024p05629

年代:1969

数据来源: WILEY

摘要:

In January 1968, Pioneer 8 passed through the extended geomagnetic tail region at 470–580RE. The magnetic field observations suggest detection of the geomagnetic tail; the observations are similar in characteristics to those observed by Pioneer 7 at 1000RE, but they indicate a higher percentage of time was spent in the region of an extended, aberrated tai

ISSN:0148-0227    

DOI:10.1029/JA074i024p05633

年代:1969

数据来源: WILEY

摘要:

A model for the determination of the shape of the magnetopause is developed that permits the inclusion of cases where the solar wind is directed obliquely toward the geomagnetic dipole axis. The solar wind is assumed to have no motions perpendicular to its (constant) velocity vector (zero temperature approximation) and to be free of magnetic fields. The region within the magnetopause is characterized as having only one magnetic source and as being free of plasma. The procedure used here is in many ways similar to the self‐consistent field method developed by Mead and Beard to calculate the shape of the magnetopause when the solar wind flow is perpendicular to the dipole axis. They were able to find the surface shape (for perpendicular incidence) at one point at a time. In the present study, however, it is necessary to determine the position of the surface at several points at a time. The geocentric distance to the subsolar point is found to be largest for perpendicular incidence of the solar wind on the dipole axis. The cross sections of the tail of the magnetopause given by the model are not cylindrical but elongated in the direction perpendicular to the ecliptic plane. Generally, the boundary is very dependent upon the wind‐dipole angle in the region of the neutral points but exhibits very little dependence on this angle in ‘equatorial’

ISSN:0148-0227    

DOI:10.1029/JA074i024p05642

年代:1969

数据来源: WILEY

摘要:

Quasi‐periodic VLF emissions (QP's) observed at Eights, Byrd, and Polar Plateau Stations in Antarctica have been investigated. Periods of most QP's range from about 10 sec to about 2 min. At each of the stations QP's were generally found when the observing station was on the daylight side of the earth. Two general types of QP's can be identified on the basis of spectral structure and associated geomagnetic micropulsation (GP) activity. One type, which is characterized by an emission frequency that increases without interruption during one quasi‐period, lacks association with GP activity. When this type of QP occurs, either there is no concurrent GP activity or the QP period is entirely different from that of the accompanying GP. The VLF emissions may be either diffuse or discrete or a combination of both. The period often varies with the average VLF signal strength, becoming longer for weaker emissions. The second type of QP exhibits an association with GP activity. The upper frequency limit of the emission band often fluctuates in synchronism with changes in the signal strength. This type of QP has a diffuse spectral structure and is referred to here as low‐frequency hiss. Such QP's often occur simultaneously with chorus and/or periodic emissions that may or may not show QP variations. Quasi‐periodic low frequency hiss associated with geomagnetic micropulsations does not generally occur simultaneously at a pair of magneto‐conjugate Stations. QP's of the second type have lower emission frequencies (0.3–1.5 kHz) than the first type

ISSN:0148-0227    

DOI:10.1029/JA074i024p05652

年代:1969

数据来源: WILEY