摘要:

In earlier work, the development of large‐scale atmospheric disturbances has been shown to depend in an explicit manner on horizontal density gradient, static stability, latitude, and dimensions of the disturbance. This theoretical analysis is generalized by eliminating the dimensions of the disturbance. The result is verified by comparing theory with tropospheric observations; then, on a reasonable postulate, the theory is applied to determination of the instability of small disturbances in the region between heights of 20 and 80 km, the mesosphere. The results indicate that in the statically stable mesoincline large‐amplitude disturbances are limited to the polar regions and must develop slowly. In the statically less‐stable mesodecline, disturbances also are limited to the middle and high latitudes, but they may grow much more rapidly. The marked selectivity which the troposphere exhibits for disturbances three to five thousand kilometers in length occurs in the mesodecline in winter, but in summer there is only very weak preference for a wave number of two at about 65° latitude. It is inferred that summer disturbances in the mesodecline probably develop more rapidly than do disturbances in the troposphere, but that they undergo rapid change in form and size, so that they may quickly lose their id

ISSN:0148-0227    

DOI:10.1029/JZ063i001p00137

年代:1958

数据来源: WILEY

摘要:

Measurements of the ionization due to beta radiation from the air, employing two thin‐walled ionization chambers in a differential arrangement, are described. Corrections for geometry, absorption of beta and gamma radiation in the shield, formation of secondary betas in the shield, and back‐scattering of betas within the chamber are discussed.The results of 73 measurements, taken throughout the summers of 1955 and 1956, are reported. Two‐thirds of all the measurements fall within a range extending over one order of magnitude. The weighted mean of all the measurements is 0.67I. This is roughly ten times the expected value, computed from random and thoron concentrations measured at this locality. Wide (and rapid) fluctuations in ionization current were also noted.All the mechanisms coming to mind which might account for the excess ionization observed over that expected are discussed, and rejected on various grounds. By process of elimination, the possibility of the existence of a “very soft” cosmic‐ray component i

ISSN:0148-0227    

DOI:10.1029/JZ063i001p00147

年代:1958

数据来源: WILEY

摘要:

The variations of the virtual heights of theF1 andElayers of the ionosphere are studied and it is found that, in general, theElayer remains unchanged, while theF1 layer rises during geomagnetic storms. This is applied to Parker's theory for magnetic storms and it is concluded that the absorption of the storm‐associated solar energy takes place at a height between 100 and 200 k

ISSN:0148-0227    

DOI:10.1029/JZ063i001p00157

年代:1958

数据来源: WILEY

摘要:

The simultaneous measurement of both polar conductivities from a P4Y airplane using two Gerdien‐type condensers is described. An altitude distribution of conductivity representative of clear arctic air is presented. From this distribution, a columnar resistance of 6.0×1016ohm‐m2is obtained by integration from the earth's surface to 6 km. The average ratio of negative to positive conductivity was found to be 1.1.The charge on the aircraft was found to have negligible effect on the conductivity measurement for fair weather conditions. Triboelectric charging of the conductivity chamber central electrodes by aerosols was observed on most fair weather flights. Concurrent observations at the earth's surface occasionally exhibited the same effect. Even in its presence, techniques were used which permitted valid measurements of conductivity to be made. It is suggested that this effect may have been responsible for unusually high positive‐to‐negative conductivity ratios reported b

ISSN:0148-0227    

DOI:10.1029/JZ063i001p00161

年代:1958

数据来源: WILEY

摘要:

Continuous simultaneous measurements of the positive and negative light‐ion conductivities have been made to altitudes of more than 26 km. Balloons carried aloft two nearly‐identical self‐ventilated Gerdien tubes, 60 cm in diameter and 120 cm long, each connected to utilize new circuits which modulated a standard radiosonde transmitter. The operating signals for the positive and negative units are arranged to provide two different characteristic pulses. Critical tests showed that saturation effects in the measurement have been eliminated. A number of successful flights have provided more than a thousand simultaneous measurements. It is found that the negative conductivity normally exceeds the positive conductivity at levels between 5 and 18 km. The altitude of the level of equal conductivity depends critically upon the cleanliness of the air and is commonly observed between 3 and 7 km. Below this level, the positive conductivity is normally in excess. It is found that the conductivity is represented by an expression of the form λ =Aexp [βZ‐ φZ2+ ΩZ3] where the constants are different for the positive and negative con

ISSN:0148-0227    

DOI:10.1029/JZ063i001p00171

年代:1958

数据来源: WILEY

摘要:

The formation about the path of a meteor of regions of ionized and neutral atoms of meteoric material is investigated from the viewpoint of kinetic theory. It is found that the high initial velocity of the diffusing particles causes the trail to quickly reach an “initial radius” from which normal diffusion then proceeds. It is shown that the reflected signal may for most purposes be computed on the assumption that the trail reaches this initial radius instantaneously. The value of the initial radius is approximately 14 mean‐free‐paths; it is thus greater for the neutral than for the ionized trail. It is shown that at very high frequencies the initial radius may reduce the amplitude of the returned signal from under‐dense trails by as much as 50 db. If heating is neglected, it is shown that the effect of initial radius on over‐dense trails is marked at the same heights and frequencies as for under

ISSN:0148-0227    

DOI:10.1029/JZ063i001p00181

年代:1958

数据来源: WILEY

摘要:

Electron densities in the ionosphere above White Sands, New Mexico, were measured continuously from theEregion up to the lowerF2region with Aerobee‐Hi NRL‐50, a rocket instrumented by the U.S. Naval Research Laboratory. The results confirm the general structure of the daytime ionosphere above White Sands as deduced from previous NRL flights, namely, that the ionosphere remains dense between theEandF2regions, with only minor valleys in the electron‐density profiles. The electron‐density distribution is shown to be consistent with theP′‐ƒ records obtained during the rocket flight. The sporadic‐Econdition, seen on these ionograms, was found to be associated with a sharp spike in the electron‐density profile at an altitude of 101 km and approximately 1 km thick. This sporadic condition extended over a horizontal distance o

ISSN:0148-0227    

DOI:10.1029/JZ063i001p00197

年代:1958

数据来源: WILEY

摘要:

A method of measuring electron densities in theDregion, making use of the Faraday effect is given. At noon on a day of high absorption, 2,000 el/cc were measured at White Sands Proving Ground, New Mexico, at an altitude of 76 km. The technique also makes possible the determination of the differential absorption, by measuring simultaneously the sum and difference of the amplitudes of the two magneto‐ionic components at 7.754 Mc as the rocket rolls. None was found over the range 60 to 88 km. A slow increase then occurred up to 94 km, whereupon it increased very rapidly to a value of ½ per km at 96 km. Experimental difficulties prevented higher altitude measuremen

ISSN:0148-0227    

DOI:10.1029/JZ063i001p00209

年代:1958

数据来源: WILEY

摘要:

An introduction to the role of ionospheric‐layer tilts in long‐range HF and VHF radio propagation is given. Tilts in the reflecting layers can have a first‐order effect on radio propagation as a consequence of the curvilinear geometry of the earth. Low‐angle rays reflected from a properly oriented, sufficiently tiltedFlayer will propagate beyond the bulge of the earth without striking the ground and illuminate the ionosphere again. When sufficient ion density exists at the second illuminated region, the rays will propagate on around the earth. A ray may be reflected several times before striking a properly oriented tilt so that the surface of the earth is illuminated. These modes are callednFmodes, wherenis the number of layer reflections.Ray trajectories for a simple ionospheric model have been derived as an example of “tilted reflection.” Anticipated fading, MUF, and field‐strength characteristics ofnFmodes are discussed. The build‐up ofnFbackscatter echoes is not linked to the characteristics of thicklayer reflection and is explained in terms of “geometrical” time‐delay focusing.Many differentnFand combinations of conventional andnFmodes have been observed on radio frequencies between 12 Mc and 30 Mc. The characteristic ranges on the different frequencies are, to first order, the same.nFbackscatter echoes are often of high amplitude relative to conventional two‐hopF‐layer‐propagated backscatter. At times, a complete absence of intervening ground backscatter between ground‐zero and2F,3F,4F, or5Fechoes is observed. The times of occurrence ofnFmodes, length of each individual occurrence, direction of occurrence, and combinations of different modes are fundamentally related to the structure of theFlayer and the r

ISSN:0148-0227    

DOI:10.1029/JZ063i001p00217

年代:1958

数据来源: WILEY

ISSN:0148-0227    

DOI:10.1029/JZ063i001p00243

年代:1958

数据来源: WILEY