摘要:

An air‐filled ionization chamber has been constructed with a volume of 552 liters and a wall consisting of 12.7 mg/cm² of aluminized plastic wrapped over a rigid, lightweight aluminum frame. A calibration in absolute units, independent of previous Caltech ion‐chamber calibrations, was applied to a sealed Neher electrometer for use in this chamber. With this chamber and an older, argon‐filled balloon chamber in a C‐135 aircraft, we measured the ionization in the atmosphere from 1000 to 40,000 feet altitude. Other measurements off the southern California coast, primarily with the balloon chamber, resulted in a value of 2.60±0.03 ion pairs/cm³ sec atm for the cosmic ray ionization at sea level. The calibration of the 552‐liter ion chamber agrees with the old Caltech calibration to within 1%, and the airplane data were consistent with previous balloon measurements in the upper part of our altitude range. We present data on the fluctuations of ionization due to radon and its daughters in the atmosphere. Our new ionization values are lower than previous Caltech values but higher than more recently rep

ISSN:0148-0227    

DOI:10.1029/JA075i019p03693

年代:1970

数据来源: WILEY

摘要:

The structure of the upper ionosphere of Venus as observed by Mariner 5 is analyzed from the standpoint of ionization sources and sinks, of ambipolar diffusion, and of model atmospheres proposed by other investigators. It is concluded that the profiles of molecular hydrogen and atomic oxygen that have been proposed to account for the observations of scattered solar Lyman‐α radiation cannot be used to explain the upper ionosphere. Although the observed profiles of atomic hydrogen and deuterium may be adequate for explaining the topside ionosphere, the situation is doubtful. A better explanation is that the upper atmosphere contains a significant amount of helium (∼3 to 5×107cm−3) at an altitude o

ISSN:0148-0227    

DOI:10.1029/JA075i019p03707

年代:1970

数据来源: WILEY

摘要:

The observed apparent angular broadening of radio sources as they pass close to the sun is discussed in terms of statistical ray theory. Unlike earlier works in which the turbulent interplanetary plasma is assumed to possess a spectrum of Gaussian form, we here treat power spectra for fluctuations in electron density, which are assumed to be of the same form as have been obtained for magnetic field and velocity fluctuations by in situ measurements. Such spectra are distinctly non‐Gaussian. We find that the data suggest that the solar wind turbulence is strong between 10 and 100 solar radii distance from the sun. This result disagrees with earlier analyses, which suggest that the fluctuations are of the order of only a few per cent of the mean, but it agrees with the large fluctuations in electron density indicated by direct satellite measurement near the orbit of the earth. The data usually imply that the solar wind electron density varies asr−2, and that the correlation length and inner scale (that wavelength below which there is little power) of the turbulence are constant with distance from the sun. At times, however, the data imply that the electron density varies asr−2.5, and the two length scales are constant; or that the density varies asr−2, and the two length scales increase linearly with distance from

ISSN:0148-0227    

DOI:10.1029/JA075i019p03715

年代:1970

数据来源: WILEY

摘要:

Three sets of satellite measurements are used to compare solar proton fluxes in the magnetotail, in the outer magnetosphere, at synchronous altitude, and in interplanetary space. Comparisons of the interplanetary and magnetosphere proton fluxes show that outer magnetosphere disturbances play a strong role in the initial access of near‐90° pitch angle protons to synchronous altitude. One comparison of the magnetotail and synchronous altitude fluxes suggests that the synchronous altitude fluxes may not always result from a scattering of the protons in from the tail. The interplanetary magnetotail proton comparisons further confirm the results of Montgomery and Singer (1969), who found that delays in the proton access to the magnetotail were always prese

ISSN:0148-0227    

DOI:10.1029/JA075i019p03729

年代:1970

数据来源: WILEY

摘要:

On April 5, 1968, a flare‐associated sudden commencement was detected as OGO 5 was outbound through the bow shock region. Several hours later exceptionally high densities (Ne>70/cm³) were encountered, and, when the flux decreased by a moderate factor, large‐amplitude 70‐kHz noise bursts were sporadically detected on the VLF electric and magnetic sensors. We interpret the oscillations with correlatedEandBcomponents as electromagnetic waves that haven²≃1 ‐ ωp²/ω²<1, and direct comparison with the plasma probe density estimate gives an absolute calibration for that instrument. The measured wave amplitudes are also used to evaluate the local density from the relationn=cB/E, thus leading to an absolute calibration for the electric dipole within the streaming plasma. We find that all measured or deduced densities are in agreement and are compatible with the interpretation that the correlated noise bursts represent electromagnetic waves with ω near the local plasma resonance frequency. These observations are related to previous measurements of 20‐ to 30‐kHz electric fields in the solar wind (Zond 3, Venus 2, Pioneer 8 and 9, and Luna 11 and 12), and the problem of distinguishing between electromagnetic waves of this type and electrostatic plasma oscill

ISSN:0148-0227    

DOI:10.1029/JA075i019p03735

年代:1970

数据来源: WILEY

摘要:

We present magnetic field, VLF electric field, and directed positive ion flux measurements made during passage of OGO 5 through many bow shock structures both inbound and outbound on March 12, 1968. These shocks were chosen because the period March 11–13, 1968, was one of a reasonably quiet solar wind. The data are correlated on time scales ≥144 msec and show that electrostatic wave turbulence is generated in the shock front by diamagnetic currents flowing on scale lengths ∼c/ωp−, the electron inertial length. This electrostatic turbulence builds to high levels near or in the regions of large jumps in |B| and then decays rapidly downstream. A jump in |B| and the scattering or randomization of protons are observed to occur onlyaftera strong level of electrostatic turbulence is achieved; this leads to the conclusion that the electrostatic turbulence is a major contributor to the shock dissipative process. This turbulence is best explained as the ion acoustic or Buneman mode due to two‐stream instability. One very thick shock structure is displayed which contains many very large amplitude and nearly reversible magnetic field

ISSN:0148-0227    

DOI:10.1029/JA075i019p03751

年代:1970

数据来源: WILEY

摘要:

The Lyman α emission originating from hydrogen atoms in the outer atmosphere of the earth has been measured between geocentric distances of 13,000 and 102,000 km. Since the radiative transfer effects are negligible, the observed emission rates are directly proportional to atomic hydrogen column densities. The observations are consistent with simple evaporative exospheric models, but there is a suggestion that some mechanism may be reducing the density of the satellite particles at distances greater than 50,000 km

ISSN:0148-0227    

DOI:10.1029/JA075i019p03769

年代:1970

数据来源: WILEY

摘要:

Study of four magnetic storms in 1965, using Explorer 26 and ground observatory magnetic data, shows that both small and large magnetic storms develop through initial asymmetric inflation of the evening magnetosphere. Development times vary from 6 to 36 hours, and the development is sometimes interrupted. The inflating particles are injected as deep asL= 3 during the development phase in large storms but only toL= 4 in smaller storms. In the slow recovery phase there is a clear relation between the magnitude of the inflation and the location of the inflation belt. The April storm belt with 100‐γ inflation at the beginning of slow recovery was atL= 3.7, whereas the February storm with 30‐γ inflation was atL= 4.8. An unusual distortion of field direction on June 16 is interpreted as evidence for current flow along field lines at the onset of a sub

ISSN:0148-0227    

DOI:10.1029/JA075i019p03778

年代:1970

数据来源: WILEY

摘要:

The stability of the ring current belt against low‐frequency electrostatic perturbations is analyzed, including the effect of the finite electric field along the magnetic lines of force. We derive the conditions for two purely growing instabilities, the interchange and the drift mode. For an isothermal plasma in a dipole field, the critical density gradients for the interchange and the drift mode aredlnn/dlnr= −7.5 and −1.5, respectively. Due to the parallel electric field associated with the instabilities, their main consequence is to precipitate charged particles into the ionosphere, thereby relaxing the pressure gradient of the ring cu

ISSN:0148-0227    

DOI:10.1029/JA075i019p03789

年代:1970

数据来源: WILEY

摘要:

The first part of this paper presents the experimental results of a particle correlation experiment conducted between the magnetosphere and the auroral zone. The precipitation time profiles and increases of outer zone energetic electron fluxes are extremely well correlated. The enhancement of electron fluxes observed at synchronous altitudes is predominantly in the 50‐ to 150‐kev energies. The increases are non‐adiabatic, because they are not correlated with δB/δt. The variations observed in higher energy electron fluxes are generally correlated with variations in the local magnetic field and hence can be accounted for by adiabatic theories. Energy spectrums of the equatorial and auroral zone electrons are similar, with typicalefolding energies of about 20 kev for both regions. Lifetimes of the non‐adiabatic electrons are typically 10³ sec but may be as short as ∼200 sec. The equatorial electron pitch angle distribution is anisotropic and peaked toward 90°. The anisotropy in the pitch angle distribution changes with time and shows dependence on the electron flux. Finally, the energy spectrum in the equatorial plane is pitch angle dependent, with a steeper spectrum for smaller pitch angle particles. The second part of this paper presents theoretical interpretations of the experimental results, which can be consistently interpreted in terms of local acceleration by using the strong pitch angle di

ISSN:0148-0227    

DOI:10.1029/JA075i019p03802

年代:1970

数据来源: WILEY