摘要:

Venera‐9 magnetic field measurements in the Venus wake provide additional support for the hypothesis that Venus has an intrinsic planetary field. The observed field is in the direction expected for a northward moment, and is similar to that observed in equivalent locations in the terrestrial magnetosphere, both in its temporal and spatial behavior. In particular, Venera‐9 appears to have observed a plasma sheet expansion, field‐aligned currents, and tail‐field dipolar

ISSN:0094-8276    

DOI:10.1029/GL003i008p00413

年代:1976

数据来源: WILEY

摘要:

Wind friction threshold speeds (V*t) for particle movement were determined in a low pressure boundary layer wind tunnel at an atmospheric pressure of 5.3 mb. The results imply that for comparable pressures on Mars, the minimum V*t is about 2.5 m/sec, which would require free‐stream winds of 50 to 135 m/sec, depending on the character of the surface and the atmospheric conditions. The corresponding wind speeds at the height of the Viking lander meteorology instrument would be about a factor of two less than the free stream wind speed. The particle size most easily moved by winds on Mars is about 160 µm; particles both larger and smaller than this (at least down to about 5 µm) require stronger winds to initiate movement. The results presented here are in general agreement with previously reported values of V*t for particles 12 µm to 300 µm derived from one atmosphere tests, but are inconsistent with values for particles larger than about 3

ISSN:0094-8276    

DOI:10.1029/GL003i008p00417

年代:1976

数据来源: WILEY

摘要:

The positive correlation between Al/Si X‐ray fluorescence intensity ratios determined during the Apollo 15 lunar mission and a broad‐spectrum visible albedo of the moon is quantitatively established. Linear regression analysis performed on 246 1° geographic cells of X‐ray fluorescence intensity and visible albedo data points produced a statistically significant correlation coefficient of .78. Three distinct distributions of data were identified as 1) within one standard deviation of the regression line, 2) greater than one standard deviation below the line, and 3) greater than one standard deviation above above the line. The latter two distributions of data were found to occupy distinct geographic areas in the Palus Somni region. It is proposed that dark material deposited southwest of Palus Somni probably caused the anomalous distribution of data greater than one standard deviation below the regression line, and that bright material recently deposited northeast of Palus Somni probably caused the distribution of data greater than one standard deviation above the regressio

ISSN:0094-8276    

DOI:10.1029/GL003i008p00421

年代:1976

数据来源: WILEY

摘要:

The galactic cosmic ray intensity at Pioneer 10 has been compared to that at Pioneer 11 over the respective ranges of heliocentric radial distances 3.9

ISSN:0094-8276    

DOI:10.1029/GL003i008p00425

年代:1976

数据来源: WILEY

摘要:

Although Mercury and Mars appear to have magnetospheres of comparable size, Mercury's magnetosphere accelerates charged particles, whereas Mars' magnetosphere apparently does not. We propose that this difference results from the fact that rapid steady‐state convection, and the associated particle acceleration, cannot occur in a Martian magnetosphere because of its connection to a highly conducting ionosphere. Mercury, which has no conducting ionosphere and probably an insufficiently conducting surface, can exhibit rapid solar‐wind‐induced convection and hence particle acceleration in its magnetospheric

ISSN:0094-8276    

DOI:10.1029/GL003i008p00429

年代:1976

数据来源: WILEY

摘要:

We study the quasi‐neutral sheet model of Alfven [1968] as modified by Hill [1974]. If the particle motion is adiabatic the model implies a trapped particle population. In the opposite limit of Speiser [1970] and Eastwod [1972]we compute the current distribution and the magnetic field reversal compatible with a new invariant of the particle motio

ISSN:0094-8276    

DOI:10.1029/GL003i008p00433

年代:1976

数据来源: WILEY

摘要:

During a magnetic substorm on October 16, 1973 a number of magnetospheric bursts of energetic particles were observed simultaneously by IMP‐6 and IMP‐7 in the magnetotail (at XSM≃ −32 Re, YSM≃ 1.2 Reand ZSM≃ −4.7 Re) while the two spacecraft were separated by only ∼ 1 Realong the XSMaxis (ΔXSM≃ 1 Re, ΔYSM= ΔZSM≃ 0 Re). Detailed anisotropy measurements of 210 and 290 keV protons by the JHU/APL instruments on both spacecraft provide for the first time an indication of the location of the "source" of the energetic magnetospheric particles as well as evidence for its movement with speeds from ∼ 30 to more than 80 km/sec in association with the intensification of the westward auroral electrojet during a magnetic bay at the station closest to the local time of the spacecraft (also local midnight). The size of the source was estimated to be ΔX ≃ 500 km. The observations indicate that in this case energetic particles are accelerated to>1.85 MeV in a moving and localized r

ISSN:0094-8276    

DOI:10.1029/GL003i008p00437

年代:1976

数据来源: WILEY

摘要:

A rocket measurement of the atmospheric band altitude distribution in the nightglow has been made under high latitude winter conditions. An integrated intensity of 1.4kR was observed with a peak volume emission rate of 750 photons cm‐3sec‐1at 91 km. An atomic oxygen altitude distribution with a number density of 1.7 × 1011cm‐3at 100 km is d

ISSN:0094-8276    

DOI:10.1029/GL003i008p00441

年代:1976

数据来源: WILEY

摘要:

The nature of electrostatic field driving the equatorial electrojet was studied using a coherent backscatter radar at Thumba. The doppler spectra of radar echoes from ionization irregularities in the E‐region, during periods close to the morning and the evening electrojet reversals, show that the electric field, in general, is stronger during the pre‐reversal periods than during the post‐reversal periods. Similar results for the evening hours were reported earlier from the radar studies conducted at Jicamarca. This indicates that this effect is likely to be present at all the equatorial sta

ISSN:0094-8276    

DOI:10.1029/GL003i008p00445

年代:1976

数据来源: WILEY

摘要:

Recent rocket probe, barium cloud and radar measurements conducted during equatorial spread F conditions are interpreted in terms of a Rayleigh‐Taylor gravitational instability operating on the bottomside of the F peak. The persistent theoretical problems associated with strong radar echoes typically observed in patch‐like structures at high altitudes are explained in terms of regions of depleted plasma density which bouyantly rise against the gravitational fi

ISSN:0094-8276    

DOI:10.1029/GL003i008p00448

年代:1976

数据来源: WILEY