摘要:

The energy spectrum of electrons in the energy range from 5 to 160 kev is investigated near the equator, atLshells between 2 and 10, by using scintillator measurements on Explorer 14. We find: (1) peak values of 8×108electrons/cm2/sec with an average energy of ∼50 kev atL∼5; (2) peak values of 1.6×109electrons/cm2/sec with an average energy of ∼10 kev atL≳8; (3) time variations of intensity by factors of 10 or less aboveL∼4 during the 15 days of data under study; and (4) a discontinuity of the energy spectrum atL∼7, with a general tendency for the spectrum to become softer at higherL. The 10‐kev electrons measured atL∼8 are trapped in the earth's magnetic field and appear not to be a tail of the outer belt electrons. These electrons are unable, without an accompanying replenishing mechanism, to supply th

ISSN:0148-0227    

DOI:10.1029/JZ071i023p05495

年代:1966

数据来源: WILEY

摘要:

Properties of the variations in the interplanetary magnetic field observed between August 27 and November 15, 1962, are described. A heliocentric spherical polar coordinate system is employed. The polar axis is the sun's axis of rotation. The field is described in terms of the vector components,Br,Bθ, andBϕ, in this system. It is shown that the amplitude distributions of the magnitudes of the vector components of the field, taken over periods of a single field polarity, are roughly Gaussian. The widths of the distributions yield variances of 5.8, 10.0, and 10.0 γ2forBr,Bθ, andBϕ, respectively. Note that the variance in the direction radial from the sun is significantly smaller than the variances in either of the two transverse directions. Estimates of the power spectra for each of the three vector components are given over the frequency range 1.16–1160 cycles per day (cpd). Comparison of the spectra shows that variations in the radial direction are weaker than those in the θ and ϕ directions over the entire frequency range. The various ratios of the power densities ofBr,Bθ, andBϕare shown to be roughly independent of frequency. The power densities in the spectra are steeply decreasing functions of the frequency with a dependence between ƒ−1and ƒ−2between 100 and 500 cycles per day. Beyond 500 cpd the power densities are usually below 9.1 γ2/cps, the system noise level. Estimates of the cross spectra of the various pairs of field variables are given over the same frequency range, 1.16–1160 cpd. Significant coherences are established, and the phase relationships are described. Estimates of the cross spectra ofBr,Bθ, andBϕwith the plasma velocity are given over the frequency range 1.16–116 cpd. Significant coherences are established for these pairs of variables as well, and the phase relations

ISSN:0148-0227    

DOI:10.1029/JZ071i023p05509

年代:1966

数据来源: WILEY

摘要:

Energy is expended and stored when a vacuum magnetic field is confined to a limited volume of space. In the present paper this energy is analytically determined under conditions where the confinement is made quasi‐statically by a perfectly diamagnetic medium. Special attention is given to a vacuum dipole field in the applications, but the established theorems apply to arbitrary superpositions of multipole fields as well. The energies required to confine the dipole field by a diamagnetic plane, sphere, hot plasma, and spheroid are explicitly calculated from the derived theorem. Of fundamental significance is the demonstration of how equilibrium boundaries can be predicted from a free surface variational principle based upon the proven energy theore

ISSN:0148-0227    

DOI:10.1029/JZ071i023p05533

年代:1966

数据来源: WILEY

摘要:

The observed microwave emission from Venus has been widely attributed to a high surface temperature for the planet. A lack of realistic models to account for such a high temperature has led to a search for alternative interpretations for the emission. The paper describes experiments in which anomalous signals have been observed in theX‐band region from glow discharges through CO2and SO2. Although this type of emission may not necessarily be the source of the microwave emission from Venus, the fact that it occurs points out the need for caution in basing conclusions about the surface temperature on microwave observation

ISSN:0148-0227    

DOI:10.1029/JZ071i023p05541

年代:1966

数据来源: WILEY

摘要:

Counting rates from a solid‐state detector in the experiment of Fan, Gloeckler, and Simpson on the IMP 1 satellite have been analyzed to investigate the spatial distribution of electrons with energies>30 kev in the geomagnetic tail and in the magnetosheath region surrounding the tail out to ∼30 earth radii. The counting rates range from the background cosmic‐ray level (∼ 3 sec−1) up to 103sec−1and have a positive correlation with theKpgeomagnetic field disturbance index. A multiple correlation analysis was made to investigate the spatial distribution of the electrons, which leads to the following results. Within the tail (1) the particle flux is a decreasing function ofZn, the distance from the neutral sheet as determined by magnetic field observations on the same satellite by Ness, Scearce, and Seek.Znis found to be a better parameter for describing the electron distribution than the distance from either the ecliptic plane or the geomagnetic equatorial plane. (2) The radial dependence of the electron flux reported earlier by Anderson is shown to be due mostly to the spurious correlation between the radial distance andZn. (3) For a given constantZn, the flux is higher near the dawnside magnetospheric boundary than near the center of the tail. In the magnetosheath beyond the boundary of the tail, the electron flux decreases only gradually with increasing distance from the solar magnetospheric equatorial plane. The implications of these observations are discussed mainly in connection with the origin of the energetic electrons

ISSN:0148-0227    

DOI:10.1029/JZ071i023p05547

年代:1966

数据来源: WILEY

摘要:

Solutions of the continuity equation for electrons in theF2region of the earth's ionosphere are obtained for the region near the magnetic equator under noon conditions. The physical processes of photo‐ionization, recombination, diffusion, neutral winds, and electromagnetic drift are included explicitly in the equation; the presence of light ions (H+, He+) and the effects of ion drag, however, are specifically ignored. It is shown that upward plasma drift at the equator is very likely the cause of the Appleton anomaly, as originally suggested by Martyn; a drift velocity of about 10 m sec−1is required. Other cases with downward drift or with neutral winds are presented. It is shown that a 15% interhemisphere asymmetry in the electron concentration at the Appleton peaks can be caused by a 60 m sec−1neutral wind blowing from north to south. By using a very small drift velocity the time‐dependent behavior of the electron concentration along particular field lines is investigated for different initial con

ISSN:0148-0227    

DOI:10.1029/JZ071i023p05559

年代:1966

数据来源: WILEY

摘要:

Observed diurnal variations of the ionic composition in the ionosphere over Arecibo are presented in the 225–1400‐km altitude range for a typical winter and summer day under solar minimum geomagnetically undisturbed conditions. He+remains a minor constituent (about 20% or less) for all the times observed. In winter it is found to maximize at about 450–500 km at night and at about twice this altitude in the day; the transition from strongly dominant O+to strongly dominant H+takes place in a corresponding region whose extent is about 300 km at night but more like triple this in the day. In summer the transition region is some what higher and thicker. Sunrise and sunset rates of change of composition are greater in summer than winter, and the minimum altitude of the contours of constant composition is shifted from local sunrise in summer to roughly midnight in winter. These seasonal differences are ascribed to the effect of photoelectrons streaming from the magnetically conjugate ionos

ISSN:0148-0227    

DOI:10.1029/JZ071i023p05573

年代:1966

数据来源: WILEY

摘要:

On the topside sounder records an echo trace is observed that lies between the plasma and upper hybrid frequencies and is not predicted for vertical propagation. It is shown by numerical ray tracing that these arez‐mode echoes by oblique propagation between the satellite and the ordinary (X= 1) reflection leve

ISSN:0148-0227    

DOI:10.1029/JZ071i023p05579

年代:1966

数据来源: WILEY

摘要:

The theory for propagation of small‐amplitude electromagnetic waves in a cold, homogeneous plasma including negative ions and immersed in a uniform, static magnetic field is developed. It is found that for longitudinal propagation each negative ion introduces a resonance at the negative ion cyclotron frequency, a concentration dependent cutoff frequency above the negative ion cyclotron frequency, and possibly a crossover frequency depending on the ion concentrations and charge‐to‐mass ratios. At both the cyclotron frequency and the cutoff frequency the group refractive index becomes infinite. Between these two frequencies there is a ‘nose’ frequency, for which the group refractive index is a minimum. Examples are given for a three‐and five‐component plasma. Application of this negative ion theory is made to propagation of negative ion whistlers in the ionosphere. It is found that for frequencies near the negative ion cyclotron frequencies the WKB approximation is valid above 300 km during the nighttime and 150 km during the daytime. Effects of collisions can be neglected above 150 km. An ideal experiment is proposed for observation of negative ion whistlers (1–1000 cps). Sample whistler, frequency‐time spectrograms like those that would be observed with such an experiment are sketched. From the distinctive frequencies on these sample spectrograms, it is shown that the negative ion specie and concentration can be determined using the developed cold p

ISSN:0148-0227    

DOI:10.1029/JZ071i023p05585

年代:1966

数据来源: WILEY

摘要:

Broad‐band VLF radio noises from about 4 kc/s to above 10 kc/s are frequently observed near the auroral zone with the Injun 3 satellite. These broad‐band VLF radio noises are called VLF hiss. In this study we select VLF hiss events for analysis by requiring that the radio noise intensity from 5.5 to 8.8 kc/s exceed 3×10−10gamma2/cps (about 5 times the receiver noise level). During the 10‐month lifetime of Injun 3 approximately 140 events occur that satisfy this criterion. The frequency spectra of the VLF hiss observed by Injun 3 is typically a flat noise spectrum with a distinct lower frequency cutoff. The lower frequency cutoff is often found to have a nearly symmetric latitude variation centered on a region of intense electron precipitation. The range of invariant latitudes (INV) for which VLF hiss typically occurs is about 7° wide and is centered on 77° INV at 12.0 hours magnetic local time (MLT), decreasing to 72° INV at 23.0 hours MLT. On the high‐latitude side of the 40‐kev trapping boundary, where VLF hiss usually occurs, intense fluxes of soft electrons are often accompanied by VLF hiss. It is found that the correlation between VLF hiss and intense fluxes (j>2.5 × 107(cm2ster see)−1) of electrons (E>10 kev) is dependent on the exponential folding energyE0. The correlation is very good forE0from 3 to 4 kev but poor

ISSN:0148-0227    

DOI:10.1029/JZ071i023p05599

年代:1966

数据来源: WILEY