摘要:

An experiment has been performed to test the spatial constancy of cosmic radiation within the solar system by measuring a short‐lived and long‐lived cosmic‐ray‐induced radioactivity in a recently fallen stone meteorite. The measurement was performed on the Hamlet chondrite that fell in Indiana on October 13, 1959. The ratio of the 35‐day argon 37 to the 325‐year argon 39 was found to be 2.0±0.3. The relative production rates for these isotopes was determined by bombarding the meteorite with 3‐bev protons. The ratio of the argon 37 to argon 39 production rates was found to be 1.5±0.2. Since the ratios were the same within experimental uncertainty, it was concluded that the flux of cosmic radiation is constant in the space between the earth and the asteroidal belt. The argon 39 contents of four other chondrites were measured. The values obtained were as follows: Richardton 7.1±0.6, Murray 9.4±0.5, Forest City 11.9±0.5, Benton 9.0±0.4, and Hamlet

ISSN:0148-0227    

DOI:10.1029/JZ065i010p03025

年代:1960

数据来源: WILEY

摘要:

The radioactive isotopes argon 37, argon 39, and tritium are measured in the Hamlet chondritic meteorite and in the Aroos iron meteorite. The ratio of the radioactivity of argon 37 to that of argon 39 at the time of fall is 2.3±0.2 for the Hamlet meteorite and 1.4±0.3 for the Aroos meteorite. The ratio of the production rate of argon 37 to that of argon 39 in a sample of the Hamlet meteorite irradiated with 2‐bev protons is 1.2±0.3. These measurements indicate a higher flux of cosmic rays at a distance of 1 astronomical unit from the sun than at several astronomical units. The ratio of the radioactivity of tritium to that of argon 39 is 29±6 for the Hamlet meteorite and 2.0±0.5 for the Aroos meteorite. The ratio of the production rates in the Hamlet target sample is 24±6. The ratio of tritium to argon 39 in the Benton chondritic meteorite is 29±4. The data indicate that the cosmic‐ray flux integrated over the same region of space for different times is constant. The tritium is anomalously low in the Aroos iron meteorite. Similar tritium anomalies have been observed previously in iron

ISSN:0148-0227    

DOI:10.1029/JZ065i010p03035

年代:1960

数据来源: WILEY

摘要:

The isotopic composition of thallium from six meteorites was measured, in order to determine whether any radiogenic Tl205from the decay of 24‐m.y. Pb205was present. Although the Pb/Tl ratios of these meteorites differed by factors of 50, isotopic compositions of meteoritic and terrestrial thallium were equal to within 1 per cent. For Canyon Diablo, this implies a solidification time of ≥3.0×108years after nucleogenesis by the ‘sudden synthesis’ model, and ≥1.0×108years after the isolation of the solar system by the ‘continuous synthesis’ model. The bearing of these results on the I129‐ Xe129ages of Reyn

ISSN:0148-0227    

DOI:10.1029/JZ065i010p03043

年代:1960

数据来源: WILEY

摘要:

The effect of a rapidly moving highly conducting solar plasma, or solar wind, on the earth's magnetic field should be to deform it and confine it; it should not be to pull out to infinity magnetic lines of force which otherwise would lie close to the earth. At low latitudes the geomagnetic field is strengthened by the interaction at all distances from the earth out to the confining boundary, beyond which there is solar plasma and no geomagnetic field. At high latitudes, however, the geomagnetic field is weakened by the confining action of the solar wind. The shape that the deformed geomagnetic field should assume is roughly that of a tear drop; the marked lack of symmetry in the deformed field must be an important factor in space investigations such as measurements of trapped radiation or geomagnetic field. The boundary between the geomagnetic field and the solar plasma should be turbulent; there is a possibility that the presence of the hydromagnetic waves generated by the turbulence will open the tail of the tear drop, thus modifying the confinement of the field by the solar wind.

ISSN:0148-0227    

DOI:10.1029/JZ065i010p03049

年代:1960

数据来源: WILEY

摘要:

The instrument is designed to determine the density, direction, and magnitude of the bulk velocity of the protons of the interplanetary plasma. It is essentially a Faraday cup containing four grids which serve (a) to keep the electrons of the plasma from reaching the collector and (b) to suppress the photoelectric current by modulating the incoming protons without modulating the photoelectrons produced when the cup faces the sun. A transistorized electronic system amplifies, compresses, and demodulates the a‐c signal from the collector before transmitting it to the telemetry system of the vehicle. Current densities from 10−12to 10−8amp/cm2, and proton kinetic energies from 10 to 3000 ev, can be mea

ISSN:0148-0227    

DOI:10.1029/JZ065i010p03053

年代:1960

数据来源: WILEY

摘要:

The ‘blue haze’ is an absorbing smoke, dark as soot in reflection, red in transmission. Its currently accepted explanation by pure scattering (omnidirectional or forward) is untenable, as it would either increase the surface brightness or fail to obscure the surface details.The limb darkening of Mars is mainly the result of absorption by the smoke.The opacity of the Martian atmosphere increases from the red toward the violet. The extinction by the Martian atmosphere is greater than that by the terrestrial at all wavelengths, but only about 20 per cent of the Martian extinction is due to scattering.Dollfus' polarimetric estimate, corrected for self‐absorption, corresponds to a Martian atmospheric pressure of 87 mm Hg.The photochemical breakup of carbon dioxide and the escape of oxygen must lead to considerable concentrations of carbon monoxide in the Martian atmos

ISSN:0148-0227    

DOI:10.1029/JZ065i010p03057

年代:1960

数据来源: WILEY

摘要:

Contrary to expectations from the classical theory of an exosphere, we find that even the heaviest gases, for example the noble gases krypton and xenon, cannot be retained by the moon. Because of the ionizing effects of solar ultraviolet radiation, electric forces now become more important than gravitational forces. First we consider thermal escape from a thick atmosphere with a hot top, and then from a thin atmosphere accommodated to the temperature of the surface, but still not an exosphere. We calculate also the rate of escape of photoelectrons and deduce the escape rate of ions. The lifetime of an atmosphere containing all the krypton and xenon believed to have evolved since the origin of the moon is of the order of 800 and 50 years respectively. After the atmosphere has thinned to less than a mean‐free path (i.e., an exosphere), yet another mechanism of escape of heavy gases exists. It seems likely that the moon as a whole is positively charged to a potential of about +20 volts, owing to the great intensity of solar ultraviolet radiation. Hence, in the vicinity of the moon there will exist a strong electrostatic field. Whenever a krypton or xenon atom is ionized while it is in flight within the screening length near the moon, the ion will be expelled by the electrostatic field. The lifetime turns out to be ∼1000 years and is somewhat increased by the effect of solar corpuscular streams. Hence we conclude that there is not much likelihood that light or heavy gases evolving from the moon will be retained by the moon. The only gas in the vicinity of the Moon can come from interplanetary space its

ISSN:0148-0227    

DOI:10.1029/JZ065i010p03065

年代:1960

数据来源: WILEY

摘要:

Radar echoes from the moon have been observed at 400 Mc/s for the purpose of determining the scattering properties of the moon. The results go beyond the investigations of other authors who claim that the moon is a quasi‐smooth reflector having a range depth of less than 600 μsec. Results described in this report indicate that, although the moon behaves as a quasi‐smooth reflector in the 0‐ to 600‐μsec range depth, beyond this range the moon behaves as a uniformly rough scatterer, giving echoes out to 1 lunar radius or the limit of visibility of the moon's surface from the earth. An empirical fit to the integrated range versus time display provides an angular scattering law for each infinitesimal area of the surface given by:P(ϕ) ∝ [(sin  θ)/θ]20±6+1/10A procedure for mapping the details of the moon's surface by radar, using range and Doppler shift coordinates, is suggested. This technique does not req

ISSN:0148-0227    

DOI:10.1029/JZ065i010p03071

年代:1960

数据来源: WILEY

摘要:

The ionized medium between the earth and the moon is being studied at Stanford by means of lunar radar echoes. Of prime interest is the electron density beyond the earth's ionosphere, in regions (at distances of several to 60 earth radii) where the interplanetary gas may be dominant. Six related techniques for measuring the total integrated electron density are discussed. In practice the ionospheric part could be determined separately and subtracted from the total. These same techniques could be used to measure by radar the electron density between the earth and various planets, and to measure by one‐way propagation the integrated electron density between a space probe and the earth. The moon's radar range exceeds the true range, especially at low frequencies, because of group retardation, which is a measure of integrated electron density. Density measurements based on absolute measures of radar range would require very high peak power (for pulse ranging) or very high equipment stability (for CW ranging); futhermore, the true lunar range is not known accurately. In two of the methods described here, the full average power capability of the transmitter can be used without need for high stability or precise knowledge of the lunar range. In effect, a reference is sent with the measuring quantities and only relative radar range is measured. Doppler frequency shifts and the earth's magnetic field cause only slight difficulties. However, path splitting, electron ‘blobs’ and lunar surface irregularities possibly could affect the waves more than the electrons do. The measurements might then yield information about the lunar surface or about the temporal and spatial variations of the cislunar m

ISSN:0148-0227    

DOI:10.1029/JZ065i010p03079

年代:1960

数据来源: WILEY

摘要:

The lunar radar echo is divided into specular and Lambert scatter components, the specular component being derived from a statistical model of the lunar surface. The theoretical impulse response is compared with experimental data from Trexler, and the theoretical frequency response is compared with some preliminary Goldstone moonbounce experimental data. The theory indicates that the Lambert component will be visible at high power levels and would probably become apparent about 1000 μsec after the leading edge of the echo. A value for reflectivity of 0.01 found from the level of the scatter component is used to derive an estimate of some of the average properties of the lunar surface

ISSN:0148-0227    

DOI:10.1029/JZ065i010p03087

年代:1960

数据来源: WILEY