摘要:

Calculation of the gyro‐frequency in theE‐layer at arctic stations from measurements of critical radio‐frequency differences gives a lower magnetic field than that obtained by extrapolation of the terrestrial field measured at ground‐level, and, at one station, a large semi‐diurnal variation with maxima at 06hand 18hlocal time.Ray‐path deflections which can explain similar effects previously reported for theF‐layer cannot be responsible in theE‐layer because of the opposite sense of this deviation and because of the small layer‐thickness. Moreover, no semi‐diurnal variation was found in theF‐layer.It is shown that these newE‐layer phenomena may be due to a variable concentration of heavy ions rising to over 4,000 times the de

ISSN:0148-0227    

DOI:10.1029/JZ056i001p00001

年代:1951

数据来源: WILEY

摘要:

TheEsregion as recorded on routineh'frecords taken at Brisbane (latitude 27°.5 south, longitude 153°.0 east) between June 1943 and December 1949 has been studied. At all seasons the critical frequency is lowest at dawn. In summer months, the critical frequency reaches a maximum at about 10hand then declines gradually, remaining high until after midnight. In winter, the rise is slower and the maximum critical frequency occurs around 14h, dropping markedly by sunset. In general, a highEscritical frequency is accompanied by blanketing ofFechoes up to a comparatively high frequency; but, whereas the occurrence of high critical frequencies shows a summer maximum and a winter sub‐maximum, the occurrence of high blanketing frequencies is least frequent in winter. The observations suggest that there are two distinct types ofEscommon at Brisbane—one formed at greater heights and descending to its final position, the other formedin situ. The first, the predominant type in summer, blankets strongly and has probably a uniform ionization density; but the second, the winter type, blankets little and probably has pronounced lateral irregularities. No evidence of correlation could be found with sunspot numbers, ionospheric storms, or meteor occurrence frequency, and the conclusion is reached that the BrisbaneEsis not predominantly of meteor origin. There is some slight evidence of correlation between the constant‐height type ofEsandFregion diff

ISSN:0148-0227    

DOI:10.1029/JZ056i001p00017

年代:1951

数据来源: WILEY

摘要:

A method is described for the measurement of the approximate mean height,H, of the thundercloud charges taking part in a flash to ground. The results obtained from 10 flashes give an over‐all mean of 5.2 km, in agreement with those obtained previously by other method

ISSN:0148-0227    

DOI:10.1029/JZ056i001p00033

年代:1951

数据来源: WILEY

摘要:

Electromagnetic‐wave theory is applied to various cylindrically symmetric distributions of electron density to ascertain the dependence of reflected radio signals upon the system parameters. Results are expressed in terms of the average effective dielectric constant, the circumference/wave‐length ratio of the cylinder, and the incident wave polarization. Two models have been mainly considered—a linear radial variation of electron density, and a constant density distribution. The general properties and dependences of the echoes are summarized for each major region of trail parameters, and the transitional characteristics are indicated.A qualitative comparison of these results with published observational data leads to a new picture of the trail decay p

ISSN:0148-0227    

DOI:10.1029/JZ056i001p00037

年代:1951

数据来源: WILEY

摘要:

Pulse soundings of the ionosphere at vertical incidence taken at 100 and 325 kc show pronounced splitting of the echoes received at night. The ranges of most of the echo components are found to lie between about 90 and 130 km. Four possible explanations of splitting are suggested, as follows: (1) Off‐vertical reflections, (2) magneto‐ionic splitting, (3) partial reflection in a layer of monotonically increasing ionization‐density, and (4) division of the region into a series of partially‐reflecting partially‐transmitting strata. Experimental data in the form of records of virtual height as a function of time indicate that the first three explanations are not acceptable. The fourth explanation, however, is consistent with all available data, including the characteristics of multiple reflections and certain systematic differences in the polarizations of echoes at different heights. It is concluded, therefore, that the lower ionosphere contains at night a system of reflecting strata at discrete heights, capable of both reflecting and transmitting incident electromagnetic energy. A new mechanism of ionospheric layer formation may be required to explain thes

ISSN:0148-0227    

DOI:10.1029/JZ056i001p00053

年代:1951

数据来源: WILEY

摘要:

Two methods for finding the energy velocity in electromagnetic propagation are in common use, the one employing wave packets and the other involving the Poynting vector. However, there appear to have been few attempts to correlate the results, especially for propagation through media of complex natures. The present paper, which is the first of a series, deals only with non‐dissipative media, in which the effective permittivity matrix, ∈pq, is Hermitian, that is,. For such media, it is shown that the directions given by the two methods are the same, and hence either may be used for the direction of energy f

ISSN:0148-0227    

DOI:10.1029/JZ056i001p00063

年代:1951

数据来源: WILEY

摘要:

The direction and intensity of magnetic polarization of Tertiary sediments and volcanic rocks in various localities in Japan were measured. Samples were collected from Upper Miocene to the recent beds in Kanto, Toyama, and Kinki districts. A series of samples of sedimentary strata in Kanto, ranging from the lowest bed of Upper Miocene to the uppermost layer of Pleistocene, were examined especially in detail. The declination of magnetic polarization of the whole section, more than 4,000 meters in thickness, is nearly the same as that of the present earth's magnetic field, while the inclination gradually decreases from the mean value of 25° in Miocene to 50° in Pleistocene beds.The reverse polarization was found only in the cases of pyroclastic (volcanic) sediments in the upper part of Upper Neogene and volcanic lavas of the same geological age in Kinki distric

ISSN:0148-0227    

DOI:10.1029/JZ056i001p00073

年代:1951

数据来源: WILEY

摘要:

Under a working agreement with the United States Navy Hydrographic Office, a 1950.0 edition of the isogonic chart of the world has been compiled by the United States Coast and Geodetic Survey. Data were collected from all available sources throughout the world. These data were punched into cards, reduced to epoch 1950.0, sorted and averaged by one‐degree quadrangles, using machine processes. The average values so derived were entered on base maps and used to control the drawing of isogonic lines. The method has resulted in a saving of many man‐years of hand work. The results have been published on one mercator and two polar charts by the Hydrographic Off

ISSN:0148-0227    

DOI:10.1029/JZ056i001p00081

年代:1951

数据来源: WILEY

摘要:

Results are presented for the first 11 years of a study of the frequency of overhead auroras in North America as a function of latitude in a region south of the auroral zone. The data have been averaged in various ways so that monthly and annual variations are demonstrated. It appears that there is a relatively constant level of auroral activity throughout the year in the region 58° to 60° geomagnetic latitude, while auroras appearing overhead south of these latitudes are more frequent during equinoctial periods. Auroras have been seen as far south as 52° during this period every month of the year. Correlation of auroral frequency with sunspot number is not high on a month‐by‐month or three‐month running‐

ISSN:0148-0227    

DOI:10.1029/JZ056i001p00085

年代:1951

数据来源: WILEY

摘要:

Anomalous propagation observed by radio amateurs at frequencies of 28 to 148 Mc during displays of aurora polaris is described. This phenomenon, first correlated with aurora in 1939, is characterized by the following features:(1) A very high fading rate, such that voice modulation is rendered unintelligible(2) Directional antennas give best results when pointed north (toward the aurora)(3) Lack of skip effect(4) Little change in polarizationComparison of reports of the radio phenomenon with visual observations of aurora indicates this effect is most common with auroral displays extending below 56° geomagnetic latitude, although the lack of amateur stations at high latitudes may influence these data. Until more precise fading data are available, development of a suitable theory is deferred

ISSN:0148-0227    

DOI:10.1029/JZ056i001p00097

年代:1951

数据来源: WILEY