摘要:

Autocorrelation functions are computed for profiles ofD,H, andZobtained by a three‐component airborne magnetometer over Western Canada and over the Atlantic east of Bermuda. The accuracy of magnetic charts is computed as a function of the distance over which interpolation is made. The accuracy is not significantly increased by smoothing. A comparison with the autocorrelation functions of simple models indicates that most anomalies originate in a thin layer 11 km below sea level under the continent and 6.5 km below sea level under the ocean. Intense magnetization of the rocks (0.005 to 0.05 cgs) is indicate

ISSN:0148-0227    

DOI:10.1029/JZ062i001p00001

年代:1957

数据来源: WILEY

摘要:

Modern data seem to support the thesis (van Bemmelen, 1899) that the secular motion of the northern magnetic pole is a nearly linear oscillation. This oscillation is along the axis of a great magnetic anomaly in the arctic. Except for the constraint of the anomaly, the motion would probably be circular or quasi‐circular, as suggested by the historical declination‐dip cur

ISSN:0148-0227    

DOI:10.1029/JZ062i001p00019

年代:1957

数据来源: WILEY

摘要:

Thewestward driftof surface geomagnetic patterns (the rate of which is about 30° of longitude per century) has at least one superimposedrotationof period ∼480 years (Fig. 1), and possibly another of period ∼800 years; these are phenomena of a peculiarly localized nature. The 480‐year rotation is demonstrable not only in the curves of declinationversusdip, but also in the isoporic patterns. A strongpulse‐disturbancewhich occurred in the relative rotation of the terrestrial core, and therefore in the westward drift, is shown to affect the 480‐year rotation in a manner which helps to clarify the rel

ISSN:0148-0227    

DOI:10.1029/JZ062i001p00029

年代:1957

数据来源: WILEY

摘要:

A set of calculated curves are presented for the reflection coefficients at a sharply bounded homogeneous ionized medium with a superimposed magnetic field. The results are plotted parametrically to permit general comparisons with experimental data. Both steady‐state and transient cases are considere

ISSN:0148-0227    

DOI:10.1029/JZ062i001p00043

年代:1957

数据来源: WILEY

摘要:

The density and pressure of the atmosphere from 90 to 220 km above White Sands, New Mexico, were determined from the Viking 7 rocket flight on 7 August 1951 at 11:00 a.m. MST. A Philips ionization gage was used to measure pressure and pressure changes on the side of the nose cone of the rolling rocket. Measured pressure in the 90 to 105 km region were corrected for velocity ram and residual gas, and were approximately one‐fourth of the Rocket Panel values. The derived pressure of 3×10−7mm Hg at 220 km is twice the corresponding Rocket Panel value. Densities were measured from 120 to 185 km and at 220 km. The 220 km density value of 9×10−8gm/m3agrees with the Rocket Panel value. However, the density values at the lower altitudes are one‐fourth to one‐half those of the Rocket Panel. These lower density values in the 100 to 130 km region are in good agreement with values obtained from X‐ray absorption experiments. Scale heights, (RT/Mg), derived from the density data above 140 km, are approximately a factor of two higher than Rocket

ISSN:0148-0227    

DOI:10.1029/JZ062i001p00057

年代:1957

数据来源: WILEY

摘要:

It is proposed that, at ultra‐high frequencies, underdense meteor echoes have an effective scattering lengthL, which is much less than a Fresnel zone. Consequently, UHF meteoric echoes may be analyzed in terms of Fraunhofer diffraction theory, resulting in a relaxation of the requirement that a meteor trail be perpendicular to the radar line‐of‐sight before an echo can be received. Formulas for the back‐scattered power, time duration, and echo rate are

ISSN:0148-0227    

DOI:10.1029/JZ062i001p00079

年代:1957

数据来源: WILEY

摘要:

The weak and fluctuating radio signals observed at distances of 1,500 km on VHF are attributed to scattering fromE‐region turbulence. It is noted that propagation constantsk= 4π/λ sin (θ/2), corresponding to the experimental frequencies (28 to 108 Mc), just straddle the viscosity cutoff wave‐numberks= (2 meters)−1of the region, thereby giving a qualitative explanation for the curious dichotomy found in the experimental data. The two competitive turbulence theories are then developed in detail near the viscosity transition range. It is found that pressure fluctuations of the ionosphere's neutral gases induce a spectrum of dielectric variations which reproduce the frequency and scattering angle dependence of the experimental results quite well. A theory of turbulent mixing of ionization gradients is then developed along the lines of Heisenberg's original treatment of the velocity field. This process predicts a frequency variation of power levels which is also satisfactory. It is concluded that more precise, simultaneous measurements will be required to choose between the two theories on th

ISSN:0148-0227    

DOI:10.1029/JZ062i001p00093

年代:1957

数据来源: WILEY

摘要:

Some recent observations in connection with seismic exploration of the continental shelf off the west coast of India are described. A single ship with a single sono‐buoy was used. Five shots were fired at distances up to six miles from the sono‐buoy. Roughly, the depth of the ocean was about 80 fathoms, and a negative temperature gradient existed. The exact times of shots were calculated from the observed arrival of direct waves. The loose sediments are surmised to be about 2.8 km thick, and seismic velocity in these sediments is found to be 1.2 miles per second. The depth of sediments has been calculated from assigning a broad maximum in the records to reflection from the bottom of the loose sedime

ISSN:0148-0227    

DOI:10.1029/JZ062i001p00113

年代:1957

数据来源: WILEY

摘要:

The work reported on here is an investigation of the radial distribution of electrical conductivity σ in the earth's mantle. Previously this function had been inferred only to about the 800‐km depth from the geomagnetic transient variations of external origin (see Lahiri and Price). Throughout the remaining lower portion of the mantle, we make use here of the longer wave periods which characterize the geomagnetic secular variation. Choosing a power law for σ, the wave attenuation and phase retardation after propagation through the mantle are investigated, using sinusoidal input functions, and an equivalent conductivity is established on the basis of amplitude attenuation. Aperiodic models at the core are solved by the method of Laplace transforms and a time discontinuity inHr. (δ‐function inHr) is treated in detail. The elapsed time for a pulse to reach the earth's surface is expressed in terms of an equivalent conductivity. The latter quantity is then gotten indirectly from a study of the time‐dependent magnetic observatory records. Judged somewhat better than an order of magnitude, in these calculations, σ is shown plotted throughout t

ISSN:0148-0227    

DOI:10.1029/JZ062i001p00117

年代:1957

数据来源: WILEY

摘要:

An attempt to describe some aspects of induction drag is made in this short paper. The quoted expressions for translational and rotational induction drags of a sphere of infinite electrical conductivity moving in an incompressible fluid of finite electrical conductivity in the presence of a magnetic field may be derived following an earlier paper by the author. An analogy with the viscous drag is drawn, and it is shown that, unlike ordinary viscosity, the hydromagnetic or inductive viscosity is anisotropic in nature. A condition for this second viscosity to play an important role is also obtained. The rest of the paper is devoted to a discussion of the limitations of the results obtained. It is shown that the results hold good for small bodies or weak induction currents. When applied to large bodies or strong currents, the appropriate corrections for the electromagnetic and for electrostatic shielding effects must be applied. An order of magnitude calculation shows that, for bodies of cosmical dimensions, the correction is precisely of the same order as the induction effect itself.

ISSN:0148-0227    

DOI:10.1029/JZ062i001p00143

年代:1957

数据来源: WILEY