ISSN:0048-6604    

DOI:10.1029/RS007i003p00345

年代:1972

数据来源: WILEY

摘要:

More than twenty European vertical‐sounding stations participated in an intensive period of observation ofESon June 15, 16, and 17, 1971. Results show that, using values of ƒ0ESfrom this network, useful information can be obtained about the structure and movement ofESclou

ISSN:0048-6604    

DOI:10.1029/RS007i003p00347

年代:1972

数据来源: WILEY

摘要:

Using amateur signals in the 50‐MHz band to indicate the presence of oblique‐incidenceE8paths, the diurnal, seasonal, and magnetic relationships of the phenomena for the years 1964–1970 were examined. Summer double diurnal peaks were found along with ‘off‐season’ meteor shower

ISSN:0048-6604    

DOI:10.1029/RS007i003p00351

年代:1972

数据来源: WILEY

摘要:

An ionosonde has been used to measure the ordinary and extraordinary critical and blanketing frequencies separately. While the results support the idea that transparent sporadic‐Ereflections occur from small volumes within theEregion, it is likely that the plasma density even in these volumes is often less than that required to cause total reflection. The structure of sporadicEis probably as follows: The peak plasma frequency varies by roughly equal amounts above and below a mean value often by a megahertz or so, within a few kilometers. Some intense blobs cause total reflection; other small volumes of increased plasma frequency strongly scatter radio waves of somewhat greater frequenc

ISSN:0048-6604    

DOI:10.1029/RS007i003p00355

年代:1972

数据来源: WILEY

摘要:

A comparison is made between observation and theory of simultaneously observed wind shear and electron density in the lower ionosphere. The observation was done by K‐8–16 rocket flown from Kagoshima Space Center, Japan. The method of characteristics for time‐dependent solution of the equation of continuity, which is a partial differential equation of the first order, was used. The calculation shows a remarkable consistency between the observation and the theory even in details. The result strongly supports the wind‐shear theory for sporadic‐Eformation. The solution suggests that the effective recombination rate is 10−8cm3sec−1as found from other ionospheric

ISSN:0048-6604    

DOI:10.1029/RS007i003p00359

年代:1972

数据来源: WILEY

摘要:

Principal qualitative and semiquantitative expectations of the wind‐shear theory of sporadic‐Eare stated, with special emphasis on the significance of observed time variations in deciding whether the theory is operative and whether the vertical‐shear mechanism is dominant. Nine wind profiles and twenty‐two sporadic‐Eobservations made in Hawaii are examined in the light of these expectations and are judged to behave consistently with the wind‐s

ISSN:0048-6604    

DOI:10.1029/RS007i003p00363

年代:1972

数据来源: WILEY

摘要:

The characteristics of midlatitude sporadic‐Elayers are observed using rocket payloads incorporating a probe and a propagation experiment.Layers below 120 km show evidence of preferred altitudes. The slopes of layers are within 1° of horizontal. The horizontal dimensions are deduced to be several hundred kilometers. Individual profiles of daytime layers show a range of shapes ranging from triangular to rectangular. The plasma frequency derived from the peak electron density in the layer is found to agree with the blanketing frequency given by the local ionosphere sound

ISSN:0048-6604    

DOI:10.1029/RS007i003p00367

年代:1972

数据来源: WILEY

摘要:

Analysis of frequency distribution of vertical shear of horizontal winds is reported for 2000 samples obtained between 90 and 136 km. The distribution is independent of altitude when shears are normalized by dividing by limiting shears of .075 sec−1below 110 km, decreasing to .035 sec−1at 128 km. Associated vertical wavelengths are also altitude independent when normalized, with shortest wavelengths increasing from 3 km at 90 km to 10 km at 136 km. The Richardson number, as a criterion of turbulence, shows that 7% of space/time samples below 110 km will permit turbulence to initiate, while no samples above 115 km will permit onset of turbulence. Viscosities (computed by Hines equation relating viscosity and limiting wavelength) are 30‐fold greater than molecular at 90 km, approaching molecular above 115 km. The rate of deposition through viscous shear is 2000–4000 erg g−1sec−1, but 10% of the samples have a five‐fold higher rate, which will significantly affect temperature profiles. The shears found are capable of increasing molecular ion and electron density to about 4×103cm−3from background ionization levels below 103cm−3, and to 2×104cm−3from backgrounds of 104cm−3. They cannot significantly enh

ISSN:0048-6604    

DOI:10.1029/RS007i003p00377

年代:1972

数据来源: WILEY

摘要:

Recent developments in wind‐shear theory and other midlatitudeEStheory, with a discussion of relevant experimental work, is given. The role of metallic ions and especially their production and loss is not understood. The gradient instability is specifically excluded from this discussion though it is likely to be importan

ISSN:0048-6604    

DOI:10.1029/RS007i003p00381

年代:1972

数据来源: WILEY

摘要:

A discussion of the observed properties of midlatitude sporadicEleads to the conclusion that vertical redistribution of neutral ionization is the only mechanism by which long‐lived metal ions can be concentrated into thin sheets extending over horizontal distances of several hundred kilometers. However, vertical ion transport occasioned by observed wind shears with vertical scales of a few kilometers fails to account for the vertical structure ofE8layers and their diurnal and seasonal variations. Experimental evidence indicates that, below 120 km, narrow layers of enhanced ionization coincide with abrupt changes in the magnitude and direction of the wind shear. These changes, marked by corners in the horizontal‐wind hodograph, occur over vertical intervals of 100 meters or less. Two alternative physical interpretations of these quasi‐discontinuities are discussed (I now regard my earlier suggestion that they represent gravity shocks as unlikely): stable contact discontinuities, across which the temperature and density (but not the vertical component of velocity and not the pressure) change abruptly; very narrow (Δz≃ 10 meters) sheets of very high shear (dV/dz≃ 0.1 sec−1). It is shown that in either case the layer could function as an effective ion trap. Strong and variable electric polarization fields, however, would interfere with the action of such a trap. Considerations related to the variable component of the polarization field provide a simple and straightforward qualitative explanation for the double‐peaked diurnal variation of intense summertime sporadicE, its seasonal variation, and its negative correlation with mag

ISSN:0048-6604    

DOI:10.1029/RS007i003p00385

年代:1972

数据来源: WILEY