摘要:

The role played by the ionosphere's mean electron density for scatter propagation is considered. An electron plasma at the scattering point (1) increases the effective wavelength and (2) decreases the scattering angle. These effects combine to modify the basic propagation variableby a factor which depends only on the instantaneous maximum usable frequency for the path. Associated signal‐level variations are found to be insignificant for conventional VHF scatter links. Such an analysis does provide an explanation for recent observations ofF‐layer scattered signals and their correlation with ƒMUF/ƒ. Apparent scattering‐height changes caused by variable refractive pulse delay times are also

ISSN:0148-0227    

DOI:10.1029/JZ062i003p00343

年代:1957

数据来源: WILEY

摘要:

This report describes a method for obtaining the so‐called “molecular weight” of air at high altitudes of the earth's atmosphere above the transition region for the dissociation of molecular into atomic oxygen. A reasonable working model, based upon the ratio of absolute temperature to molecular weightT/M, which is proportional to the slope of the logepressure υsaltitude curve, is presented. The region considered is from 90 to 600 km, assuming that the composition of the atmosphere is constant up to 90 km.The calculations are based upon experimental data reported by Byram, Chubb, and Friedman from Aerobee 16, 1 December 1953. Since the 1956 Model Atmosphere of the Air Research and Development Command employs a variable scale height gradient with altitude, the diffusive equilibrium and mixing formulas of Nicolet and Mange were modified to obtain the vertical distributions of the various atmospheric constituents. The mass densities are found by multiplying the number densities by the respective molecular mass of the individual components of the atmosphere.The molecular weights at the various altitudes were calculated from the formulaKnowing the composition of the atmosphere at any altitude, it is possible to determine the temperature through the relationship of the scale height to temperature,H

ISSN:0148-0227    

DOI:10.1029/JZ062i003p00351

年代:1957

数据来源: WILEY

摘要:

The experimental evidence offered in support of Booker and Cohen's theory is examined point‐by‐point. It is concluded that the theory does not accurately represent the properties of meteoric ech

ISSN:0148-0227    

DOI:10.1029/JZ062i003p00367

年代:1957

数据来源: WILEY

摘要:

A method is presented for obtaining the amplitude of an obliquely reflected one‐hop sky‐wave from recordings of a continuous transmission of a low‐frequency radio signal. The reflection coefficient is obtained from the ratio of the one‐hop sky‐wave to the calculated unabsorbed one‐hop sky‐wave. The method is applied to a 135.6‐kc/s signal recorded in the Alaskan area. The‖R‖component of the reflection coef

ISSN:0148-0227    

DOI:10.1029/JZ062i003p00373

年代:1957

数据来源: WILEY

摘要:

A comparison is made between published VHF forward‐scatter data and results of vertical‐incidence investigations of the lower ionosphere, mainly at a frequency of 1.75 Mc/s. The received waves in each type of transmission are shown to have many similar characteristics, such as temporal variations, and to originate in the same height regions. It is concluded that the two types of transmission have a common ori

ISSN:0148-0227    

DOI:10.1029/JZ062i003p00383

年代:1957

数据来源: WILEY

摘要:

A rocket instrumented to measure Lyman alpha and X‐rays was fired while a small flare was in progress on June 20, 1956. The rocket reached peak altitude about ten minutes after the flare was first seen visually. An unusually high X‐ray flux was observed extending to a short wavelength limit of 3A. Although the flare was still visible in Hα, Lyman alpha was not appreciably different from no

ISSN:0148-0227    

DOI:10.1029/JZ062i003p00389

年代:1957

数据来源: WILEY

摘要:

Echoes of exceptionally long delay detected by a HF radar located in the West Indies are interpreted as ground backscatter propagated by two or more successive reflections from theF‐region of the ionosphere, without intermediate ground reflection. Propagation of this sort is associated with tilts in the reflecting layers. Pronounced tilts are encountered regularly in equatorial regions; one occurs almost daily at approximately 1900 local time over the geomagnetic equator; another occurs around noon in the vicinity of the subsolar point. It is shown that tilt‐supported propagation can take place at frequencies considerably in excess of the MUF predicted in the usual way. It is believed that these results may explain the reports by radio amateurs of anomalous propagation between North and South Amer

ISSN:0148-0227    

DOI:10.1029/JZ062i003p00399

年代:1957

数据来源: WILEY

摘要:

The drag exerted on the satellite in its orbit arises partly from collisions with neutral air particles and partly from losses associated with the passage of a charged sphere through an ionized medium. It is found that the charged and neutral effects are comparable under the atmospheric conditions expected at an orbital altitude of 300 miles.

ISSN:0148-0227    

DOI:10.1029/JZ062i003p00413

年代:1957

数据来源: WILEY

摘要:

Minimum virtual height and critical frequency of the ionosphericF2‐layer are analyzed by means of the superposed epoch method. Results of this analysis, on the basis of their statistical significance, suggest a relationship between frontal passage in the troposphere andF2‐layer characteristics. The observed effects are interpreted qualitatively in the light of a hypothesis suggested by Martyn, and seem to be consistent with the concept of dynamic coupling between lower and upper atmosphere. The results of this analysis are also found to agree with previously reported troposphere‐ionosphere correla

ISSN:0148-0227    

DOI:10.1029/JZ062i003p00425

年代:1957

数据来源: WILEY

摘要:

Observations at the time of the great solar flare of 23 February 1956 of oblique‐incidence signal intensities and simultaneous observations of the background cosmic noise were made at VHF for a number of high‐latitude communication links employing the ionospheric‐scatter mode of propagation. During the flare and for some hours afterward, all paths lay in the dark hemisphere. Virtually synchronously with the arrival of solar cosmic rays, a sharp signal‐intensity enhancement was observed, which is tentatively explainable if it is supposed that the first‐arriving solar cosmic rays were predominantly of positive charge. The unusually stable night‐time absorption which developed in one to three hours after the flare and the much greater following daytime absorption are explained in some detail as consequences of the deposition in theDregion of moderately heavy solar atomic ions, such as calcium, having ionization potentials low compared with the normal atmospheric constituents. The absorption effects, which were limited to fairly high geomagnetic latitudes, gradually died away over a period of several days. The absence of significant magnetic disturbance and unusual auroral activity for nearly 48 hours after the flare is shown to be in accord with the suggested explanation of the absorption effects. Asymmetry about local noon was observed in the absorption effects on signal intensity, for which an explanation i

ISSN:0148-0227    

DOI:10.1029/JZ062i003p00431

年代:1957

数据来源: WILEY