摘要:

Satellite measurements of suprathermal electrons made at the time of conjugate sunrise indicate that they represent photoelectrons escaping from the production level of about 300 km and moving along the geomagnetic field lines into the conjugate ionosphere. The daytime maximum value of the flux is about 2.5 × 108electrons cm−2sec−1. The spectral distribution of the flux shows a maximum around 5

ISSN:0148-0227    

DOI:10.1029/JA074i007p01715

年代:1969

数据来源: WILEY

摘要:

Interpretations of the Lyman‐α data from Mariner 5 are critically discussed, in view of the finding by the experimenters that a normal exosphere of atomic hydrogen does not fit. A two‐component exosphere appears to be required, but the second component cannot be H2, or H at a different temperature. Deuterium is a much better possibility, but the D/H ratio at the base of the exosphere must be about 10. It is shown that the ratio can be reconciled with all available observations or upper limits. Transport through the thermosphere can increase the D/H ratio as much as a factor of 100: the ratio in the lower atmosphere could then be 0.1. This transport problem is solved in detail, with the eddy diffusion coefficient as a parameter. Isotopic fractionation by thermal escape is discussed, and Venus is shown to be an especially favorable case for this process. The required initial supply of H2O is less than 0.1% of the terrestrial value. This amount can be postulated ad hoc, or the remainder plausibly can be dissipated in an initial phase, an atmosphere dominated by water vapor, in which escape of H should have been very fast. It is concluded that a high D/H ratio on Venus is a serious possibi

ISSN:0148-0227    

DOI:10.1029/JA074i007p01720

年代:1969

数据来源: WILEY

摘要:

Anisotropic fluxes of energetic particles (electrons,E≳ 50 kev; protons,E≳ 830 kev) encountered by the satellite Explorer 33 in, and immediately adjacent to, the distant trapping region have been studied. Attention has been given to their location in the frame of reference provided by measurements of the local field. On the day side the flux is peaked at right angles to the field, whereas on the night side it is peaked along the field. Two exceptions to this rule were found, and fluxes of ‘streaming’ particles were found in the magnetosheath, immediately adjacent to the magnetopause. The observations are compared with previous ones and are discussed in the light of current

ISSN:0148-0227    

DOI:10.1029/JA074i007p01740

年代:1969

数据来源: WILEY

摘要:

A study of outer radiation zone electron intensities at times of magnetic storms is reported. The purpose of the study is to determine how well the intensity at one local time tracks the intensity at the same invariant latitude but at a different local time. Any difference in the intensity time profiles might be expected to yield information about the mechanisms responsible for acceleration of outer‐zone electrons, particularly the locations of these mechanisms. The measurements refer to selected periods of several days each and have been obtained at altitudes below 3500 km, invariant latitudes in the range 50° to 72°, and at several pairs of local times. At times of magnetic storms the tracking at the two local times is often quite poor at latitudes as low as 55°. For short periods around local midnight and on the morning side of the earth the intensities observed are appreciably higher than those on the afternoon side. It is concluded from these observations that most of the storm‐time acceleration of electrons to energies about 35 kev takes place on the night and morning sides of the earth. The measurements are used to place an upper limit on stably trapped fluxes in the outer radiation zone that agrees reasonably well with the whistler mode limiting flux calculated byKennel and Petschek

ISSN:0148-0227    

DOI:10.1029/JA074i007p01749

年代:1969

数据来源: WILEY

摘要:

An east‐west asymmetry may exist in the solar wind velocity due to the action of a well‐known mechanism, namely, the influence of the solar rotation on the interaction between fast and slow streams. The mechanism predicts that fast streams tend to come from the west and slow ones from the east with respect to the average solar wind direction. It is noted that if there is a correlation between density and velocity, a measurement of the average azimuthal wind component is not sufficient to determine the angular momentum flux. Experimental evidence from Pioneer 6 indicates that about 50% of the east‐west variations in flow direction with periods around 4 days (the largest period studied) may be due to the fast stream‐slow stream interaction. The percentage decreases for shorter

ISSN:0148-0227    

DOI:10.1029/JA074i007p01759

年代:1969

数据来源: WILEY

摘要:

After entering the magnetosphere, electromagnetic waves excited in the magnetosheath are absorbed by the magnetospheric plasma either through cyclotron damping at harmonics of the proton and electron gyrofrequencies or through an encounter with the upper hybrid resonance. This absorption of wave energy causes the plasma to be heated. Since the magnetosphere is an inhomogeneous medium for the propagation of ordinary and extraordinary waves, absorption takes place at a spatial location that depends on the wave frequency. An analysis of the passband of extraordinary waves shows that protons are heated rather uniformly throughout the magnetosphere because of cyclotron damping, whereas electrons are most efficiently heated at the plasmapause by wave absorption at the upper hybrid resonance. Results of recent observations of low‐frequency electric fields indicate that 100‐kev protons can be produced by this mechan

ISSN:0148-0227    

DOI:10.1029/JA074i007p01763

年代:1969

数据来源: WILEY

摘要:

An analysis has been made of the occurrence of satellite scintillations using observations of the Beacon Explorer satellites at a number of sites throughout Australasia. Time versus latitude contour diagrams of occurrence and mean index for the geomagnetic latitude range 20° to 55° are described. These are compared with similar contour diagrams of the occurrence of the frequency‐spreading component of bottomside spreadF, sporadic‐Eionization, and the ducting and scattering components of topside spreadF. Similarities are noted in the occurrence patterns of scintillations and topside scattering on one hand and bottomside frequency spreading and topside ducting on the other. However, these two patterns are complementary in that the occurrence of scintillation and of topside scattering are minimal in the latitude range 30° to 40°, while the occurrence of frequency spreading and topside ducting maximizes in this latitude range. It is inferred that of theF‐layer irregularities, those that produce topside scattering are more able to cause scintillation than are those that result in topside ducting and bottomside spreadF. It is further postulated that there exists, in theFlayer, a continuous spectrum of irregularity sizes, the peak of which shifts from a dimension (normal to the earth's magnetic field) of less than 1 km at high latitudes to greater than 1 km between latitudes 30° and 40° and back to less than 1 km at the lowe

ISSN:0148-0227    

DOI:10.1029/JA074i007p01772

年代:1969

数据来源: WILEY

摘要:

Full wave calculations have been performed within the frequency range of gravity waves (10−3≤ ω ≤ 10−2sec−1) for a thermospheric model between 150 and 500 km altitude. In this altitude range gravity waves are coupled with heat conduction waves. Reflection, transmission, conversion, and coupling from one wave type into the other one is described by the elements of the scattering matrix. The dependence of these elements on height and angle of incidence is discussed. The transmission coefficients of gravity waves calculated by full wave theory are compared with simple ray calculations and show that ray treatment is a sufficient approximation for obliquely upward propagating gravity waves and that gravity waves predominate throughout the thermosphere. The thermosphere reacts like a selective filter with respect to upward propagating gravity waves with optimal transmission atkx∼ ω/C(ω = angular frequency;C= velocity of sound;kx= horizonta

ISSN:0148-0227    

DOI:10.1029/JA074i007p01786

年代:1969

数据来源: WILEY

摘要:

The response of the upper atmosphere to various forms of time‐dependent heating is calculated by use of approximate analytic solutions of the heat conduction equation. Time lags of maximum temperature and density behind peak heating are distinctly different and, for short‐duration heating events, are strongly altitude dependent. The time and space characteristics of a one‐dimensional heat source that produces a density change consistent with the observed drag on satellites during a geomagnetic disturbance are identified. The desired model for polar substorm heating maximizes in the 140‐ to 160‐km altitude region with an average duration of 4 to 5 hours. The relationship between the amount of heat injected per unit column during a disturbance of maximum geomagnetic indexapisq∝ (ap)1/2. This simple relationship suggests a common heating mechanism that is present at all levels

ISSN:0148-0227    

DOI:10.1029/JA074i007p01796

年代:1969

数据来源: WILEY

摘要:

The morphology of auroral infrasonic waves at College, Alaska, is related to the temporal and spatial distributions of supersonic auroral motions that develop within the auroral oval during polar magnetic substorms. The break‐up phase of the auroral substorm results in the rapid auroral motions that generate the observed infrasonic waves. Direct observations of infrasonic wave packets from overhead supersonic auroral forms, as well as the comparison of the morphologies of infrasonic waves and auroral motions are used to verify a shock wave model for the generation of auroral infrasonic waves. Electrodynamic drift and joule heating associated with the auroral electrojets in auroras that produce infrasonic shock waves are accepted as the basic processes that generate the initial acoustic pulse within a moving auroral for

ISSN:0148-0227    

DOI:10.1029/JA074i007p01812

年代:1969

数据来源: WILEY