摘要:

The dependence of the counting rate of a cosmic ray detector on the asymptotic directions of approach of the primary cosmic radiation is discussed. By means of a simulation of the geomagnetic field that uses spherical harmonics up to the sixth degree, and an arbitrary anisotropy in the primary cosmic radiation, a method for calculating the time variations in the counting rate of a cosmic ray detector is developed. Resolving the arbitrary anisotropy as a Fourier series in longitude, the amplitude and phases of the diurnal (24‐hourly) and semidiurnal (12‐hourly) components of the daily variation are calculated for a number of stations. No simple relationship is observed between the phases and the latitudes and longitudes, geographic or geomagnetic. Moreover, the theoretical calculations point out that a difference of more than five hours between the diurnal phases at two different places could arise purely from the known geomagnetic configuration. A study of the time‐averaged diurnal component of the daily variation experimentally observed by 22 neutron monitors during the International Geophysical Year (1957–1958) reveals good agreement with the theoretical calculations and leads to the following conclusions: (1) The results are consistent with an anisotropy that is independent of rigidity in the range 1–200 bv, the exponent of the power law which fits the data being 0.0±0.05. (2) The anisotropy varies as the cosine of the asymptotic latitude and has a maximum in the direction 85° to the east of the earth‐sun line. (3) The maximum amplitude of the average anisotropy is 4×10−3times the average

ISSN:0148-0227    

DOI:10.1029/JZ068i002p00345

年代:1963

数据来源: WILEY

摘要:

Mechanisms that could result in the acceleration of charged particles within the magnetosphere are discussed in terms of the responses expected from experimental instruments as they pass through acceleration regions. A series of experimental tests is outlined that can determine whether acceleration of trapped particles is important. The mechanisms discussed include Fermi acceleration, which can accelerate protons to tens or hundreds of kilovolts and can increase the energy of trapped electrons several hundred‐fold before they are lost in the dense atmosphere. A change in the intensity of the solar wind or of the strength of a ring current can change the energy of trapped particles owing to the betatron mechanism. Electrons can be accelerated to kilovolt energies by the setting up of plasma oscillations or by acceleration within moving clouds or intrusions of solar plasma. Finally, particles can be accelerated to energies of ten kilovolts or more in the vicinity of neutral line

ISSN:0148-0227    

DOI:10.1029/JZ068i002p00371

年代:1963

数据来源: WILEY

摘要:

Using ray theory and assuming longitudinal propagation conditions, we investigated the circumstances in which curvature of the ray is identical with curvature of the magnetic field. In general the two curvatures are only identical if there exists an appropriate transverse gradient of the plasma density. For a given ratio of the wave frequency to the gyrofrequency, and of the plasma frequency to the gyrofrequency, the necessary transverse gradient of plasma density may be calculated as a ratio to the curvature of the magnetic field. Curves have been prepared showing, for a wide range of values of the parameters, the transverse gradient of plasma density required to make the ray curvature identical with the field curvature. Of particular interest are the conditions in which no transverse gradient of plasma density is required to make the ray curvature identical with the field curvature. In these circumstances waves are guided by the magnetic field even in a homogeneous plasma. It is found that at hydromagnetic frequencies (wave frequency less than the ionic gyrofrequency) such guiding never occurs. Indeed, at frequencies small compared with the ionic gyrofrequency the ray curvature is equal to the field curvature in magnitude but opposite in sign. Above about twice the ionic gyrofrequency, field guiding is possible in a homogeneous plasma for the left‐hand wave (O wave) but not for the right‐hand wave (X wave), provided that the homogeneous plasma density is adjusted to an appropriate va

ISSN:0148-0227    

DOI:10.1029/JZ068i002p00387

年代:1963

数据来源: WILEY

摘要:

The observation of a 100‐second periodicity in X‐ray intensity at balloon altitudes during an intense auroral‐zone X‐ray event is described. The peaks in X‐ray intensity are attributed to variations in the flux of electrons incident on the atmosphere rather than to motion effect of the electron precipitation. As such, the variations of the electron flux reflect the dynamics of the mechanism responsible for the precipitation of the electrons into the atmosphere. The relation of this type of periodic electron bombardment to pulsating aurora is c

ISSN:0148-0227    

DOI:10.1029/JZ068i002p00395

年代:1963

数据来源: WILEY

摘要:

The possibility of artificially heating the electrons in theFregion by means of a radio wave is investigated. On the basis of a somewhat oversimplified model of the actual problem, equations are derived for the steady‐state values of the electron density and electron temperature profiles as a function of the transmitter parameters and the initial state of the ionosphere. These equations are then solved numerically for several cases of interest. At a frequency of 50 Mc/s, slight but probably detectable changes in the ionosphere could be produced by means of a large antenna and an average transmitter power of the order of 500 kw or more. At higher frequencies, or for smaller average powers, the effects are negligible. Thus heating is unlikely to complicate incoherent scattering measurements in theFregion. By using frequencies very near theF‐region penetration frequency, however, it is possible to achieve much larger effects because of the resonant absorption. Using only 50–100 kw and a sufficiently large antenna we could change the electron temperature by a few hundred degrees. Using higher powers, much larger changes are possible. Detailed measurements of the heating effects could provide considerable data on transport phenomena in the ionospheric plasma. The experiment would also provide a convenient way of studying a nonequilibrium plasma under fairly controlled condi

ISSN:0148-0227    

DOI:10.1029/JZ068i002p00401

年代:1963

数据来源: WILEY

摘要:

Measurements of the impedance at 7.75 Mc/s of an electrically short antenna in the ionosphere indicate that power is absorbed by some mechanism other than electromagnetic radiation. The importance of the radiation of energy as an electron pressure (electroacoustic) wave generated near the antenna is discussed, and it is shown that the calculated power radiated by this mechanism yields results in good agreement with the observations.

ISSN:0148-0227    

DOI:10.1029/JZ068i002p00415

年代:1963

数据来源: WILEY

摘要:

Experiments are described in which the scattering behavior of the moon has been investigated at wavelengths of 3.6 cm, 68 cm, and 7.84 meters. At 3.6 cm some 14 per cent of the surface appears to be covered by structure of the order of the wavelength in size, whereas at 68 cm only 8 per cent of the surface is this rough. The bulk of the surface appears to be smooth and undulating and describable by means of an exponential law for the lateral correlation of surface height. The mean gradient is found to vary, the wavelength being about 1 in 11 for points spaced by 68 cm and 1 in 7 for points spaced 3.6 cm. Interpreting these results to obtain a value for the reflection coefficient is complicated by the ability of the surface to scatter either more or less favorably than a perfectly smooth spherical surface. The best value that can be obtained from the radar results for the reflection coefficient is 6 per cent at 68 cm, which in turn yields a value for the dielectric constant of 2.8.

ISSN:0148-0227    

DOI:10.1029/JZ068i002p00423

年代:1963

数据来源: WILEY

摘要:

The general theory of radar reflection from planetary surfaces that was described in an earlier publication is extended, and it is shown how the slope of the surface profile can be obtained from the autocorrelation function of the signal envelope. The theory is applied to lunar observations made at 440, 151, and 38.25 Mc/s, and a value of 14° is obtained for the rms slope. The angular power spectrum is found to be wavelength‐dependent except at the short wavelength limit, where it depends only on the surface slo

ISSN:0148-0227    

DOI:10.1029/JZ068i002p00449

年代:1963

数据来源: WILEY

摘要:

Spectrums of oceanographic and meteorological variables are investigated for the frequency range between zero and six cycles per year. It is found that the root mean square amplitudes of the annual and nonperiodic oscillations are of the same order of magnitude. Sea level changes at neighboring islands are coherent and in phase. Changes at distant islands are coherent only at low frequencies, and their phase depends upon whether the islands are affected by the same wind regime. There is a strong and direct relation between changes of sea level and of sea temperature at low frequencies, but there is no relation between changes of sea level and of atmospheric pressure. Air temperature and sea temperature oscillations are directly related to each other, except where rainfall affects the former, in which case there is no relation. In the intratropical convergence zone a significant and inverse relation exists between air temperature and rainfall. Salinity and rainfall fluctuations are related inversely to each other, but the coherence varies considerably from island to island. Sea temperature and wind speed oscillations are related inversely to each other in the NE trade wind region. The statistical results from the island station analysis are in fair agreement with those obtained from largescale hydrographic surveys.

ISSN:0148-0227    

DOI:10.1029/JZ068i002p00455

年代:1963

数据来源: WILEY

摘要:

Baker‐Nunn camera observations of satellite 1959α1over 315 days; of 1959ηover 105 days; and of 1960L2over 294 days were analyzed for 35 spherical harmonic coefficients of the earth's gravitational field and for position shifts of six geodetic datums. Of the three satellites, only 1960L2appeared to have good enough distribution of observations and small enough drag effects to yield significant results. The datum shifts obtained have standard deviations averaging ±25 meters in each coordinate. The gravitational harmonic coefficients obtained appear to be appreciably different from zero for indices (n, m) of (2, 2), (3, 1), (4, 1), and (4, 3). In particular, geophysically significant magnitudes were obtained for22: 2.51×10−6and31: 1.79×10− 6(n

ISSN:0148-0227    

DOI:10.1029/JZ068i002p00473

年代:1963

数据来源: WILEY