摘要:

The papers in this issue are based upon some of the contributions presented at the Third International Symposium on Equatorial Aeronomy held at the Physical Research Laboratories, Ahmedabad, India, February 3‐10, 1969. Previous meetings of the Symposia had been held in Huaychulo, Peru, in 1962, and in Sao José dos Campos, Brazil, in 1965.The earlier meetings had started cooperative work among workers in equatorial regions, initiating a breakdown of the tendency for the worker in equatorial regions to feel himself an ‘out‐station’ from one of the metropolitan countries. The conferences had also served the purpose of bringing some degree of unification among the areas of research that had tended to be pursued in isolated channels. Aeronomy is taken to include all studies of the earth's atmosphere above 60 km. Equatorial aeronomy restricts the interest to the vicinity of the equator and to effects that originate at the

ISSN:0048-6604    

DOI:10.1029/RS004i009p00735

年代:1969

数据来源: WILEY

摘要:

Under a grenade series of experiments with sounding rockets made at Barreira do Inferno, Natal (5.6°S, 35°W), 19 successful launchings have yielded useful data on the upper stratosphere and the mesosphere during the period August 7, 1966, to March 5, 1968. These experiments covered the height range of about 35‐95 km and were supplemented by radiosonde data from 19 balloons that provided data up to approximately 35 km. Also, data from 29 meteorological rockets with an upper limit of 60 km are available for the period September 14, 1966, to July 24, 1968. Only 2 of these 29 launchings were instrumented for temperature measurements. Data on winds, temperatures, and densities have been obtained and analyzed from the rocket‐grenade and balloon experiments. Some features of the wind and temperature distributions in the upper stratosphere and mesosphere are discussed. Extremely low mesopause temperatures of the order of 130°K were noticed in early summer at about 90 km. The temperature at this height was found to be higher in winter than in summer. A correlation between temperature at 40 km and absorption of cosmic noise at 30 MHz is also presented as a probable evidence of stratosphere‐ionosphere

ISSN:0048-6604    

DOI:10.1029/RS004i009p00741

年代:1969

数据来源: WILEY

摘要:

The variation of nondeviative absorption of radio waves in the ionosphere with solar zenith angle has been studied at different spot frequencies. The experimental results suggest that the theoretical expression for the nondeviative absorption in the morning and evening hours should contain a constant absorption term along with the term dependent on the solar zenith angle. In the present communication it has been shown that the constant absorption term is present throughout the day, but its effect is not apparent toward noon hours, and at these hours the experimentally observed values of absorption at a fixed frequency appear to be a function of solar zenith angle only. The probable origin of the constant absorption term has been discussed.

ISSN:0048-6604    

DOI:10.1029/RS004i009p00751

年代:1969

数据来源: WILEY

摘要:

Results are presented of theoretical investigations of the nature of nondeviative radio‐wave absorption at vertical incidence, in an isothermal ionospheric region where collisional frequency is comparable to the exploring frequency and where the recombination coefficient is not constant but is a function of height. It has been shown that in such cases the variation of nondeviative absorption with solar zenith angle and frequency may be represented by the expression:L ∝ {(cosX)π/(ω±∣ωL∣)C+n}where symbols have their usual meaning. The values ofnandCare such that (2 —C) ≥n≥

ISSN:0048-6604    

DOI:10.1029/RS004i009p00757

年代:1969

数据来源: WILEY

摘要:

A study of the occurrence frequency of equatorial Es(Esq) and daytime blanketing Esat Ibadan (dip 6°S) and Zaria (dip 3°N) in Nigeria is presented. The period of study covers the years 1958 to 1965. Experimental results from the study reveal that Esqand blanketing Esare different phenomena and that a high incidence of Esqis usually accompanied by a low incidence of blanketing Es, and vice versa. In addition, the extent of the Esqbelt in Nigeria is deduced from the relative occurrence of Esqand nonequatorial Esduring the daytime at Ibada

ISSN:0048-6604    

DOI:10.1029/RS004i009p00765

年代:1969

数据来源: WILEY

摘要:

After a brief presentation ofSqandLelectric current systems deduced from geomagnetic data, electric conductivities and wind models in the dynamo region are discussed. It is then shown that the solar negative‐mode thermal diurnal tide and the lunar semidiurnal gravitational tide having a phase shift with altitudes produce the best fitSqandLcurrent systems, respectively. Distributions of electrostatic fields are computed, and electromagnetic drift speeds in the ionosphericFregion are also examined. These calculated values agree well with observed result

ISSN:0048-6604    

DOI:10.1029/RS004i009p00771

年代:1969

数据来源: WILEY

摘要:

The position of the magnetic dip equator at 100 km and the gradient of position with time and altitude are tabulated using the POGO (10/68), GSFC (12/66), and IGRF (10/68) geomagnetic field models. The positions agree within a few tenths of a degree with each other but differ up to 2° from older models and charts. The maximum gradients with time (0.2°/yr) and altitude (−0.3°/100 km) occur to the west of Af

ISSN:0048-6604    

DOI:10.1029/RS004i009p00781

年代:1969

数据来源: WILEY

摘要:

The daytime measurements of the velocities and other fading characteristics of equatorialEsand blanketingEsirregularities in the frequency range 4–6 MHz are presented for Ibadan. The modes of signal returns by the two groups ofEsare discussed. The experimental results suggest that the equatorialEsirregularities observed in the 4‐6 MHz frequency range at Ibadan are of a similar nature to those observed at 50 MHz at Huancayo during a weak electrojet. A tentative inference from the equatorialEsresults is that the magnitudes of equatorialEsvelocities may be independent of the relative strength of electrojet intens

ISSN:0048-6604    

DOI:10.1029/RS004i009p00785

年代:1969

数据来源: WILEY

摘要:

A rocket‐borne Langmuir probe and plasma‐noise probe have been used to study the ionization irregularities of scale sizes 20 meters to 0.4 meter in the lower equatorial ionosphere over Thumba during the evening twilight of February 2, 1968. lonization irregularities were observed mostly in the height range 97–106 km, 142–155 km and around 170 km. The spectral indexnwas calculated for a power law of the typeE(k)=Akn. In the 100‐km region, irregularities with different spectral indices were found to coexist, indicating the superposition of at least two different spectra. The irregularities with spectral index of −3.0 to −3.5 are probably produced through neutral turbulence, whereas irregularities with spectral index of −1.6 to −2.0 are probably produced by electric fields. The irregularities observed near the rocket apogee are produced by the rocket itself and have a spectral index of +3.0. The actual values of these indices are likely to be more (including sign) than given by the present calculations since the detection efficiency of a Langmuir probe for the irregularities may

ISSN:0048-6604    

DOI:10.1029/RS004i009p00791

年代:1969

数据来源: WILEY

摘要:

Comparison of the occurrence of VHF radio propagation over a 6620‐km transequatorial circuit between Korea and northern Australia with the development of the equatorial anomaly in theFlayer shows that the transequatorial propagation mechanism is closely related to changes in the form of the equatorial anomaly. Signal occurrences are most common when the anomaly infoF2exhibits sharp well‐defined crests located fairly symmetrically on either side of the dip equator at dip angles between 20° and 30°. These crests correspond to large horizontal gradients in theFlayer ionization density, which are known to be capable of refracting radio waves at frequencies well above the normal for a horizontally homogeneousFlayer. It is suggested that all transequatorial VHF signal occurrences observed over this circuit can be explained in terms of anF2F2propagation mode, with the ionospheric refractions occurring at the crests of the equatorial an

ISSN:0048-6604    

DOI:10.1029/RS004i009p00797

年代:1969

数据来源: WILEY