Equatorial spread F.

Calvert, W.

doi:10.6028/nbs.tn.145

Cited by 15 publications

(15 citation statements)

References 12 publications

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“…Later, a marked striated structure appears in which the striae slope downward from left to right. This phenomenon has been discussed by Calvert et al [1963]. A rough proportionality exists between the increase in phase path length near sunset (given in fig.…”

Section: Equatorial Fluttermentioning

confidence: 85%

On Frequency Variations of lonospherically Propagated HF Radio Signals

Davies¹,

Baker²

1966

Radio Science

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A technique for measuring the frequency variations of ionospherically propagated radio waves by spectrum analysis of the received signal is described, together with some theory needed to interpret such measurements. Examples of the types of variations observed with both vertical and oblique propagation are presented. On "quiet" days in middle latitudes, frequency variations of the order of ± 0.2 c/s occur, having periods of the order of 10 min. During disturbed periods the variations may be as much as 2 to 3 c/s on 5 Mc/s with vertical propagation. The frequency stability is generally greater for oblique propagation than for vertical propagation; however, the received spectrum is broader for oblique propagation. The frequency stability of E echoes is, in general, much greater than that of F2 echoes. At night and during some geomagnetic storms, the discrete (line) spectra give way to diffuse spectra. During periods of flutter fading at low latitudes, the discrete spectra are transformed into continua with frequency spreads of up to± 5 c/s about the mean value. Distinctive frequency deviations are caused by solar flares, geomagnetic disturbances, and traveling ionospheric disturbances. Of these, the solar flare‐induced frequency variations are the most striking. Deviations of up to 50 c/s have been observed on WWV‐10 Mc/s received at Boulder during flares. However, frequency deviations associated with solar flares have a most probable duration of about 4 min, and the majority of them have magnitudes less than 1 c/s.

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Section: Equatorial Fluttermentioning

confidence: 85%

On Frequency Variations of lonospherically Propagated HF Radio Signals

Davies¹,

Baker²

1966

Radio Science

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“…A radio link was set up from Tripoli, Lybia (32.5°N, 13.1°E) to Accra, Ghana (5.3°N, 0.2°W) (Calvert et al 1963); later, another link was set up from Monrovia, Liberia (6.2°N, 10.5°W) to Accra (Davies and Chang 1968). In both experiments, a CW signal was transmitted from one location, and Doppler properties of the received signal were monitored at the other.…”

Section: Radio Propagation: Cw-doppler Resultsmentioning

confidence: 99%

“…Clearly, if this kind of relationship can be shown to exist, a unified and more comprehensive description of ESF would emerge. Patches have been detected in the bottomside F layer, over several decades, with ground-based instruments such as (1) ionosondes (Calvert and Cohen 1961;Cohen and Bowles 1961), (2) radio experiments (Calvert et al 1963;Davies and Chang 1968;Röttger 1973), and (3) radars (Clemesha 1964;Kelleher and Skinner 1971). Impressions are that the patches, observed by these different methods, are produced by related plasma structures (e.g., Kelleher and Röttger 1973;Aarons et al 1978).…”

Section: Introductionmentioning

confidence: 99%

Upwelling: a unit of disturbance in equatorial spread F

Tsunoda

2015

Prog. in Earth and Planet. Sci.

120

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Plasma structure in the nighttime equatorial F layer, often referred to as equatorial spread F (ESF), is not uniformly distributed, either in time or in space. Observations indicate that ESF in the bottomside F layer takes the form of patches; plasma structure within the F layer takes the form of localized plasma depletions, called equatorial plasma bubbles (EPBs), which tend to occur in clusters. Another observed feature is an upwelling, which has been described as a localized, upward modulation of isodensity contours in the bottomside F layer. Interestingly, zonal widths of ESF patches, EPB clusters, and upwellings are similar. Moreover, all display an east-west asymmetry. The objective of this paper is to show, for the first time, that an ESF patch is the bottomside counterpart of an EPB cluster, and that both are products of the electrodynamical process that takes place within an upwelling. The process can be described as having three phases: (1) amplification of upwelling amplitude during the post-sunset rise of the F layer, (2) launching of the first EPB of the evening, from crest of the upwelling, and (3) structuring of plasma within the upwelling. Hence, an upwelling, whose presence is responsible for the formation of ESF patches and EPB clusters, can be envisioned as a unit of disturbance that occurs in the nighttime equatorial ionosphere.

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“…Many researchers have shown that proteins, especially soy can successfully be extruded and injection molded into various plastic products2–13 and several aspects of the technology behind protein processing are presented in recent reviews 1, 14…”

Section: Introductionmentioning

confidence: 99%

Mechanical Properties and Water Absorption of Thermoplastic Bloodmeal

Verbeek¹,

Berg

2011

Macro Materials & Eng

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Bloodmeal mixtures containing SS, water, SDS and urea were extruded and injection‐molded. Increased chain mobility with sufficient plasticization during processing increased the amount of available amino acids for strong water/protein interactions. Materials containing low water and increased SS had reduced tensile strength and elongation, compared to higher water at the same SS content. Materials containing three parts SS per hundred parts bloodmeal (pphbm), 60 pphbm water and 20 pphbm urea, were the only ductile materials after conditioning. Changing any one of these factors to a lower level will result in a brittle material. This mixture in combination with 3 pphbm SDS resulted in optimal mechanical properties (tensile strength of 9.6 MPa and Young's modulus of 534.9 MPa). magnified image

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Equatorial spread F.

Cited by 15 publications

References 12 publications

On Frequency Variations of lonospherically Propagated HF Radio Signals

On Frequency Variations of lonospherically Propagated HF Radio Signals

Upwelling: a unit of disturbance in equatorial spread F

Mechanical Properties and Water Absorption of Thermoplastic Bloodmeal

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