摘要:

The Pioneer 7 deep space probe passed through the geomagnetic tail in 1966 and crossed the magnetic neutral sheet at ∼19 and 38 earth radii. Electrons with kinetic energies>400 kev were found to be concentrated in a narrow region centered in the neutral sheet, confirming the detection of neutral sheet electrons by Murayama and Simpson with the IMP 1 satellite in 1964. The electron fluxes>400 kev do not extend outside the neutral sheet. At ∼38 earth radii the anisotropy of the electron distribution was measured by using the spin of the spacecraft and was shown to be less than 20%, consistent with the absence of any electron anisotropy within the sheet. There was no evidence for low pitch angle streaming of electrons. Most of the experimental evidence points to electron acceleration within the sheet, although this question is not settled. It appears that neutral sheet electron confinement and propagation is determined mainly by the bifurcation of the magnetic field and by the electrons drifting in the electric fields of the sheet. This phenomenon is the only example of its type so far identified in nature. The magnetic neutral sheet crossings probably detected by Ness and collaborators with the Pioneer 7 spacecraft at ∼1000 earth radii were also examined for neutral sheet electrons. It is shown that the fluxes present at ∼20–40 earth radii (50 times cosmic ray background) could not have been observed at 1000 earth radii. In the geomagnetic tailoutsidethe neutral sheet the directional distribution of>400‐kev electrons was measured in the flux ‘islands,’ which occasionally appear above the cosmic ray background level. The electron distributions are isotropic to within 25%. The origin of these ‘isla

ISSN:0148-0227    

DOI:10.1029/JA074i009p02149

年代:1969

数据来源: WILEY

摘要:

Solar proton fluxes in two energy intervals (5–21 Mev and 21–70 Mev) were measured with detectors aboard the geostationary ATS 1 satellite during the solar proton event that began on January 28, 1967. Comparison with data obtained by satellites outside the magnetosphere shows that (a) protons with energies greater than 21 Mev have essentially free access to synchronous altitude; (b) protons in the 5–21 Mev energy interval show a diurnal variation with the flux approaching the interplanetary flux level near local midnight. The transmission efficiency of the magnetosphere is not well organized by either the local (synchronous) magnetic field or theKp

ISSN:0148-0227    

DOI:10.1029/JA074i009p02161

年代:1969

数据来源: WILEY

摘要:

We explore here the possible importance of time‐dependent convection electric fields as an agent for diffusing trapped magnetospheric radiation inward toward the earth. By using a formalism (Birmingham, Northrop, and Fälthammar, 1967) based on first principles, and by adopting a simple model for the magnetosphere and its electric field, we succeed in deriving a one‐dimensional diffusion equation to describe statistically the loss‐free motion of mirroring particles with arbitrary but conserved values of the first two adiabatic invariantsMandJ. Solution of this equation bears out the fact that reasonable electric field strengths, correlated in time for no longer than the azimuthal drift period of an average particle, move particles toward the earth at a rate at least an order of magnitude faster than electric fields whose source is a fluctuating current on the magnet

ISSN:0148-0227    

DOI:10.1029/JA074i009p02169

年代:1969

数据来源: WILEY

摘要:

Expansions and contractions of the permanently compressed magnetosphere lead to the diffusion of equatorially trapped particles across drift shells. A general technique for obtaining the electric fields induced by these expansions and contractions is described and applied to the Mead geomagnetic field model. The resulting electric drifts are calculated and are superimposed upon the gradient drift executed by a particle that conserves its first (μ) and second (J= 0) adiabatic invariants. The noon‐midnight asymmetry of the unperturbed drift trajectory (resulting from gradient drift alone) is approximated by means of a simple model. In this model the angular drift frequency is found to be the geometric mean of a particle's angular drift velocities at noon and midnight. The radial diffusion coefficientD= (½) (ΔL)²/time is calculated as a function of the McIlwain parameterLand in terms of the spectral density of fluctuations in the stand‐off distance of the magnetosphere boundary. Because the unperturbed drift trajectories are asymmetric, drift‐resonant diffusion of particles is produced by spectral components at all harmonics of the drift frequency, although the first (fundamental) harmonic is the major co

ISSN:0148-0227    

DOI:10.1029/JA074i009p02182

年代:1969

数据来源: WILEY

摘要:

A study based on Alouette 1 data of electron concentration enhancement at a height of 1000 km at polar latitudes during 1962–1964 is presented. The major features are (1) Enhancement occurs in three apparently independent concentric zones, zones 1, 2, and 3. Zone 1 includes the area with invariant latitudes higher than about 80°. The upper boundaries of zones 2 and 3 are, respectively, at approximately 80° and 73° at magnetic noon and at somewhat lower latitudes at magnetic midnight. The extent or width of each zone varies with season and magnetic activity, and within each zone enhancement occurs sporadically in space and time. (2) Enhancement occurs with maximum frequency at different magnetic local times in each zone. Occurrence frequencies and amplitudes are subject to magnetic local time, seasonal and magnetic activity effects. The latter two effects on occurrence frequency are especially notable in zones 1 and 3. It is suggested that the enhancement is caused by particle ionization due to precipitation of low‐energy electrons (E<

ISSN:0148-0227    

DOI:10.1029/JA074i009p02193

年代:1969

数据来源: WILEY

摘要:

Storm‐time (Kp>4) variations of electron concentration in the polar topside ionosphere are studied. Variation profiles at invariant latitudes higher than 60° were derived for 24 Alouette 1 satellite passes directly over or near the north geomagnetic pole. The results show that storm‐time variations depend on magnetic local time, invariant latitude, and altitude. The cause of the variations is discu

ISSN:0148-0227    

DOI:10.1029/JA074i009p02208

年代:1969

数据来源: WILEY

摘要:

Laboratory studies of the ions produced by the addition of water vapor into flowing streams of O2+(or NO+) ions have led to a vapor phase reaction scheme starting with O2+that seems likely to be responsible for the formation of the observed water cluster ions H3O+, H5O2+, H7O3+, etc. in theDregion of the earth's ionosphere. Experimental difficulties have precluded quantitative rate constant measurements so far, and in addition theD‐region water vapor concentration is uncertain so that only a qualitative scheme is possible at this time. The O2(¹Δg) photoionization source recently proposed by Hunten and McElroy is presumed to be the necessary precursor O2+source. The reaction scheme involves O4+and O2+·H2O as intermediate ions; these ions are possibly present in observable concentrations in theDregion. Nitrous acid (HNO2) production is proposed to be an end result of successive hydrations of atmospheric NO+. The hydration of the atmospheric NO+and O2+ions and the formation of O4+are expected to increase somewhat the effective electron recombination coefficient in the ionosp

ISSN:0148-0227    

DOI:10.1029/JA074i009p02217

年代:1969

数据来源: WILEY

摘要:

The average rate at which a single aerosol particle captures and annihilates ion pairs in the lower ionosphere is found by analysis of the steady‐state distribution of charge in an ensemble of identical particles. With knowledge of the distribution of sizes of particles it is possible to determine the time constant for ion pair annihilation due to an aerosol. A measured particle size distribution in a noctilucent cloud is shown to imply an annihilation time constant of about 2 minutes, indicating that the cloud in question should have noticeably modified the distribution of ionization in its vicinit

ISSN:0148-0227    

DOI:10.1029/JA074i009p02223

年代:1969

数据来源: WILEY

摘要:

A Javelin rocket with a payload of ionospheric instruments was launched from Wallops Island in conjunction with an overpass of the Alouette 2 and Explorer 31 satellites. The rocket‐measured values of ion and electron temperatures, which had large positive gradients with height, were found to be consistent with the measured electron concentration profile, though this same profile was also consistent with an isothermal plasma. A downward heat flux from the magnetosphere of 1.9 × 1010ev cm−2sec−1was deduced, which could be supplied by an upward flux of photoelectrons from theFlayer of approximately 1.5 × 109cm

ISSN:0148-0227    

DOI:10.1029/JA074i009p02229

年代:1969

数据来源: WILEY

摘要:

A study based on satellite observations shows that sporadic‐Eclouds have an average length of 170 km;x‐mode blanketing lengths are found to be longer than those foromode signals. Some double‐layer data are also given. Separation distances betweenEsclouds are shown to increase as a function of height. Horizontal variations ofEsstructure are presented, and a convexEsstructure is offered as the most probable explanation ofWe

ISSN:0148-0227    

DOI:10.1029/JA074i009p02240

年代:1969

数据来源: WILEY