The geomorphology of spread<i>F</i>

Singleton, D. G.

doi:10.1029/jz065i011p03615

Cited by 50 publications

(19 citation statements)

References 9 publications

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“…An extensive study of the morphology of ionospheric irregularities has been carried out by the study of spread-F [Shimazaki, 1959 ;Singleton, 1960 and and by t.he study of radio star scintillation [Booker, 1958]. The diurnal variations given by fig ures 9 and 10 generally agree with other observations, especially with regard to the maximum at night.…”

Section: Rela Tion To !Irregularities Observed By O Ther Radio Tech Nsupporting

confidence: 72%

F-region irregularities studied by scintillation of signals from satellites

Yeh¹,

Swenson²

1964

J. RES. NATL. BUR. STAN. SECT. D. RAD. SCI.

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Scintillation of radio signals from earth satellites has b een studied for fiv e years during the d ecli ning phase of the sunspot cycle. It is found that the character of the scintillation, and thus, pr obably, of the ionospheric irregularities that cause them, var y systematically with geo magnetic latitud e, season of t he year, time of day, and phase of the s unspot cycle. Night time scintillation occurs in the F-l'eg ion, mainly at heights of about 350 km. This type of scintillation in most cases res ults from firs t-order scattering from weak, fi eld-alin ed irregularities in electron d ensity. In the Northern H em isphere such scintillations are observed north of a certain parallel of geo magnet ic latitud e, the so uthern limit varying weakly with magnetic activity. Simi lar effects arc a lso observed in the Sout h ern H emisphere. Daytim e sc intillations also sholV stro ng seasonal and s un spot-cycle depe nd ence but very little latit ud e d ep end ence.The scintillation observations of the present investigation have been compared with observation s of other manifestations of ionospheric irregularities, p articularly spread-F and radio "star" sci ntillation. It has been observed that s trong scintillation occurs simultan eously ,,-ith the occurrence of red auroral ar cs. Scintillat ion , b eing more common than red arcs, may be a more sensitive indicator of ionospher ic disturban ces.

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Section: Rela Tion To !Irregularities Observed By O Ther Radio Tech Nsupporting

confidence: 72%

F-region irregularities studied by scintillation of signals from satellites

Yeh¹,

Swenson²

1964

J. RES. NATL. BUR. STAN. SECT. D. RAD. SCI.

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“…SOURCE OF DATA As pointed out in an earlier paper (Singleton 1960) the f-plots (Wright, Knecht, and Davies 1957) prepared by the ionosonde observatories during the I.G.Y. provided an accurate and convenient source of frequency-spreading data.…”

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confidence: 99%

“…THE DIURNAL AND SEASONAL VARIATIONS Typical stations in the three main zones of spread-F activity, the equatorial, middle latitude, and auroral zones (Singleton 1960) namely Huancayo, Ft. Monmouth, and Thule, have been chosen for detailed consideration as far as diurnal and seasonal distributions are concerned. In Figure 2 the diurnal -variation of the monthly mean value of 111 is presented for each of these stations and for the months of July and September 1957 and January 1958.…”

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confidence: 99%

Spread?F and the Perturbations of the Maximum Electron Density of the F Layer

Singleton¹

1962

Aust. J. Phys.

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SummaryAn analysis has been made of spread-F data obtained from LG.Y. f-plots for several ionosonde stations grouped about longitude 75° W. to establish whether there is any connection between the severity of frequency-spreading (ilJ) and the time of day, season of the year, magnetic activity, height of the F layer, critical frequency of the F layer, and the latitude of the ionosonde station. The diurnal variations of the severity of frequency spreading are found to vary considerably with latitude and season and no clear pattern emerges. Magnetic activity affects the value of ilf but again in a complex way which varies with latitude. The magnitude of ilf seems to be greatest when the layer is high and descending at low and middle latitudes but not at high latitudes. At all latitudes the magnitude of ilf is greatest when the critical frequency is lowest. This is considered to be the dominant effect having a profound influence on the diurnal and seasonal distributions of ilf. These results are discussed in terms of the hypothesis that frequency spreading is due to the availability of a range of values of N IDJ1x . at the maximum of the F2 layer. This range of values is thought to correspond to a system of irregularities each involving an enhancement or a deficiency of electron density relative to the background ionization. The extra ionization involved in the irregularities is estimated to be of the order of 10' electrons/c.c. and is found to vary little with season, magnetic activity, and latitude.

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“…It has long been recognied (Shimazaki, 1959;Singleton, 1960;Piddington, 1964) that different irregularity production mechanisms are very likely operative at different latitudes. This is supported by our results which show that irregularities in the region of the auroral oval often are of a different size and amplitude to those at mid-latitudes.…”

Section: Discussionmentioning

confidence: 99%

“…In particular much has been learned about the world-wide occurrence characteristics of spread F irregularities from ground-based data (e.g. Reber, 1956;Shimazaki, 1959Shimazaki, , 1962Singleton, 1960Singleton, , 1968) and more recently from topside sounder data (Calvert and Schmid, 1964;Hice and Frank, 1966;Dyson, 1968). Irregularities in the F-region may be conveniently divided into two classes.…”

Section: Introductionmentioning

confidence: 99%

Direct measurements of the size and amplitude of irregularities in the topside ionosphere

Dyson

1969

J. Geophys. Res.

109

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Data obtained from the Alouette 2 Langmuir probe experiment during a 3‐month period in the fall of 1966 have been examined for effects due to electron concentration irregularities (fine structure). Irregularities occur in patches hundreds of kilometers in horizontal extent, and individual irregularities have amplitudes between 5% (limit of resolution) and 70% and dimensions of less than 2 km along the satellite path. These irregularities appear more often at night than during the day, and they occur in a region that contains the auroral oval and extends to both higher and lower latitudes. Comparison of the probe data with Alouette 2 ionograms obtained simultaneously shows that spread F occurred at the height of the satellite whenever fine structure was observed. However, particularly at mid latitudes, spread F often occurs at the satellite even when the probe does not detect irregularities. When spread F occurs, but the probe does not observe fine structure, the irregularities are less than 5% in amplitude (i.e., below the probe’s resolution). Calculations using an irregularity model indicate that spread F is often caused by irregularities less than 0.5 km thick. Several irregularity production mechanisms that could account for the results are discussed.

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The geomorphology of spreadF

Cited by 50 publications

References 9 publications

F-region irregularities studied by scintillation of signals from satellites

F-region irregularities studied by scintillation of signals from satellites

Spread?F and the Perturbations of the Maximum Electron Density of the F Layer

Direct measurements of the size and amplitude of irregularities in the topside ionosphere

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