摘要:

The spatial and temporal conjugacy of auroras at high latitudes has been investigated by flying two NC‐135 jet aircraft, equipped with all‐sky and narrow‐field cameras, along magnetically conjugate paths crossing the northern and southern auroral zones along the dipole 256° meridian. The flights were centered about magnetic midnight on March 12, 14, and 16, 1967. Magnetic activity was very low throughout this period; nevertheless, auroras were observed between dp latitudes 66° and 71° during each flight. A visual examination of all the data and a quantitative analysis of selected film frames indicate that, within the limits of error in the measurements and aircraft navigation, all the observed auroras were conjugate according to the GSFC 12/66 model of themaingeomagnetic field. In most cases when the relative positions of aircraft and aurora were the same in both hemispheres, the conjugate auroras exhibited remarkably detailed similarity (point conjugacy) in their shape, intensity, and in their spatial and temporal variations. There is a tendency for the southern auroras to be located slightly eastward of the northern conjugate auroras. Such a displacement appears to be consistent with a slight asymmetric distortion of the main geomagnetic field due to solar wind pressure and earth dipole‐sun geometry at the date and time of the measurements. These results suggest that, during magnetically very quiet times, auroras located at dp latitudes up to 71° are caused by a symmetrical injection of electrons and protons near the equatorial plane and onto magnetic field lines that are closed, stable, and relatively undistorted by external magnetic fields. Preliminary results from similar conjugate flights conducted during March 1968, a magnetically disturbed period, are briefly described. A visual inspection of these data has revealed substantial deviations in auroral conjugacy and a considerably more complex behavior of particle precipitation than that occurring during magnetically qu

ISSN:0148-0227    

DOI:10.1029/JA074i001p00001

年代:1969

数据来源: WILEY

摘要:

Models of the Venus atmosphere are presented and compared with observations obtained from Mariner 5. Best agreement is found if it is assumed that the Venus atmosphere, at all heights, consists of pure CO2. The modeling procedures are used to obtain upper limits to the abundance of N2and O. It is concluded that the N2mixing ratio should not exceed 10%. Atomic oxygen should be a minor constituent, at least for altitudes less than about 200 km. Possible variations of the upper Venus atmosphere with solar activity are discussed briefly. It is shown from the theoretical discussion that the exospheric temperature may vary from a solar minimum value of about 600°K to a solar maximum value of about 1000°K. Attention is directed to apparent similarities between the upper atmospheres of Venus and Mars. The modeling procedures, which satisfactorily account for the Venus observations, are applied to Mars. A simple photochemical theory gives results in poor agreement with the Martian ionosphere as observed by Mariner 4. Possible reasons for the discrepancy are discusse

ISSN:0148-0227    

DOI:10.1029/JA074i001p00029

年代:1969

数据来源: WILEY

摘要:

Direct inspection of the usual expressions for describing solar modulation as a function of particle parameters shows that changes in the form of the modulating function will result in a rigidity‐dependent phase lag or ‘hysteresis’ near solar minimum. As a means of investigating any such changes in modulation, regression analysis is performed among three groups of cosmic‐ray particles: (a) 50–100 Mev/nucleon protons and helium nuclei, (b) the integral intensity of protons with kinetic energies>450 Mev, and (c) particles contributing to the neutron intensity at Climax. The analysis is for the period from mid‐1963 to mid‐1966. These analyses reveal no evidence for any hysteresis before and after solar minimum and set an upper limit of ±0.09 for the fractional deviation of the flux of 50–100 Mev protons from a single valued relation with respect to the Climax neutron intensity and ±0.02 for that of protons>450 Mev. Since the absolute fluxes of these protons vary over a range of more than 36% and 16%, respectively, in this time interval this implies that any changes in the modulating function at low rigidities (<3 Gv) with respect to high rigidities (∼8 Gv) are less than 20% near solar minimum. This conclusion is discussed with respect to other recent observations of

ISSN:0148-0227    

DOI:10.1029/JA074i001p00043

年代:1969

数据来源: WILEY

摘要:

The flux and energy spectrum of cosmic‐ray electrons were investigated at 5.3 g/cm² and 2.7 g/cm² by use of balloons launched from Palestine, Texas, in October 1967. An 18‐gap glass‐metal spark chamber was used to distinguish the electron showers from the nuclear interactions. A counter telescope utilizing a gas Cerenkov counter triggered the system for particles withE/mc² ≳ 11. The system was calibrated with electrons of 1–6 bev, and the results of this calibration were used to determine the energy of the electrons seen on the flights. The flux below 3 bev appears to be dependent on altitude, while the flux above 3 bev appears independent of altitude. The fluxes in the energy range of 1–2 bev (2.05 ± 0.76 and 0.90 ± 0.56 electrons/m² sec ster bev) agree with Verma's calculated flux of secondary electrons produced in the atmosphere. Our results, which yield an integral flux of 2.72 ± 0.68 electrons/m² sec ster above 4 bev, agree best with the results of Rubtsov and Zatsepin, indicating that the exponent in the equationdN/dE=AE−βelectrons/m² sec ster bev has a value that is closer to 3.0 than to 2.6. The proton flux was monitored periodically throughout the flights. It remained constant to within the statistical uncertainty and was equal to 603 ± 60 protons/m² sec ster, thus furnishing a check that the system functioned properly at altitude, and that there was no eff

ISSN:0148-0227    

DOI:10.1029/JA074i001p00053

年代:1969

数据来源: WILEY

摘要:

The behavior of the solar wind flux and direction measured on Explorer 35 in the near lunar wake is presented. The flux near the leading edge of the wake tends to be greater than the free stream value and decreases below detectability near the wake axis. There is probably a small (≲3°) deflection of the wind away from the moon near the leading edge and a deflection toward the wake axis in the region of reduced flux. These features correlate well with variations in the magnetic field. An interpretation of the observed structure is offered that utilizes the theory of two‐dimensional steady simple waves in magnetohydrodynamics. A novel feature of the interpretation is the inference of a deflection of the solar wind from the region of the lunar limb to account for the structure near the leading edge of the

ISSN:0148-0227    

DOI:10.1029/JA074i001p00059

年代:1969

数据来源: WILEY

摘要:

During the period November 10–22, 1967, the earth‐moon system was bathed in an isotropic, homogeneous beam of solar electrons and protons whose intensities were slowly varying functions of time. Detailed angular distribution and intensity observations of these particles and vector magnetometer observations made simultaneously by the lunar orbiting satellite Explorer 35 are combined to examine particle shadowing effects by the moon. During the observing period, the moon and Explorer 35 passed from interplanetary space through the magnetotail. Simultaneous observations were made by the earth orbiting satellite Explorer 33, which was sunward of the earth's shock front and at large radial distance from the earth during most of the observing period. The angular distributions of the intensity of both electrons and protons were accurately isotropic within the magnetotail as well as in interplanetary space. Study of 33 cases of clearelectronshadowing and two cases of less clear shadowing suggests the following principal conclusions: (a) Magnetic lines of force from external sources thread through the moon in a rectilinear manner as though it did not exist. The accuracy of this statement is measured by the maximum departure from rectilinear projection that is permitted by the electron shadowing observations. This is approximately 0.1RM(lunar radius) in 2RMor 3°. (b) Electron shadowing data provide nodirectinformation on the region of access of interplanetary electrons into the magnetotail but do provide an upper limit on the trans‐B diffusion velocity υ⊥of electrons due to all causes. In the central portion of the magnetotail during magnetically quiet conditions and for radial distances ≲ 64 RE(earth radius), υ⊥≲ 100 km sec−1for 50 kev electrons. This upper limit requires, among other possibilities, that the transverse electric field Lunar shadowing of protons (Ep≳ 322 kev) is also described and discussed but is of mu

ISSN:0148-0227    

DOI:10.1029/JA074i001p00071

年代:1969

数据来源: WILEY

摘要:

Energetic electron fluxes associated with the earth's bow shock are found to be present about as often on the dawn side of the sun‐earth line as on the dusk side. The peak fluxes attained by these spikes also show no dawn‐dusk asymmetry. Upstream electron events, on the other hand, are predominantly found to the dawn side of the sun‐earth line. Both phenomena have the same temporal character with characteristic times of 30 to 150 seconds. Both have characteristic energies of bout 15 kev, but the upstream electron fluxes are much weaker. The upstream events are interpreted to be of secondary origin with the bow shock spikes representing the primary acceleration event. This local acceleration process evidently is of no consequence to the problem of the Van Allen belts and auroral proc

ISSN:0148-0227    

DOI:10.1029/JA074i001p00095

年代:1969

数据来源: WILEY

摘要:

A rocket‐borne high‐resolution echelle spectrograph was used to measure the profile of the solar hydrogen‐Lyman‐alpha line. The profile was normalized to an integrated flux of 5.2 ergs/cm² sec, the value of which was measured with a nitric oxide ion chamber carried on the same flight. The flux available for scattering by hydrogen in the geocorona was 2.8 × 1011photons/cm² sec. The optical depth at the center of the telluric absorption line was about 5.6 in the slant path at a 60° zenith distance. The general features of the profile are in agreement with earlier m

ISSN:0148-0227    

DOI:10.1029/JA074i001p00107

年代:1969

数据来源: WILEY

摘要:

A detailed analysis is presented of the Lyman‐α observations of Venus made from Mariner 5. In the analysis, we assume that the observed emission is the result of resonance scattering of the solar Lyman‐α flux by hydrogen or hydrogen and deuterium atoms in the atmosphere. The variation of the atomic densities with altitude is taken from the exospheric models of Chamberlain and McAfee. Radiative transfer effects are included but are not of crucial importance to the analysis. We find that an exospheric model consisting only of atomic hydrogen fails to give an adequate representation of the data. Instead, two constituents with mass ratios in the range 2 to 3 are required. A reasonable fit to the data is made with the hydrogen‐deuterium model after large asymmetries are introduced in the densities at the base of the exosphere. This model indicates that in the subsolar region the exospheric temperature is about 640°K and the hydrogen and deuterium densities are about 6 × 10³ and 105at 6500 km from the center of the planet. The degree of asymmetry is uncertain, but a reduction in the deuterium density by a factor of 10 and in the hydrogen density by a factor of 2 in the antisolar region at 6500 km is suggested by the night‐side

ISSN:0148-0227    

DOI:10.1029/JA074i001p00115

年代:1969

数据来源: WILEY

摘要:

In early 1963, Explorer 14 (apogee about 16 earth radii) made magnetic field measurements at the earthward end of the geomagnetic tail. On several occasions the field was observed to reverse direction in times of the order of a minute, corresponding to passages through the so‐called neutral sheet. Two of these passages, on February 10 during a moderately severe storm, are analyzed in detail. The orientation of the sheet is discussed, and it is shown how field lines may be computed from the measurements. It is found that on both occasions the field lines were connected through the sheet, with normal components of several gammas. No evidence is found of the two standing shock waves proposed by Axford, Petschek, and Siscoe. Immediately after one encounter with the sheet, the field had a southward component of up to 30 γ for over a minute. At about the same time, ground stations recorded the onset of a magnetic bay. It is suggested that this observation by the satellite was made on the far side of a region in which field line reconnection was taking pla

ISSN:0148-0227    

DOI:10.1029/JA074i001p00133

年代:1969

数据来源: WILEY