A review of some recent work on mid-latitude spread-F occurrence as detected by ionosondes.

Bowman, G. G.

doi:10.5636/jgg.42.109

Cited by 154 publications

(169 citation statements)

References 87 publications

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“…It is known that the main source of spread-F echoes is the modulation of the F layer by medium-scale gravity waves (Fejer and Kelley, 1980;Bowman, 1990). The initiation of mid-latitude F-region instability by gravity waves was studied theoretically by Huang et al (1994), who extended the instability mechanism ®rst proposed by Perkins (1973).…”

Section: Discussion and Concluding Remarksmentioning

confidence: 99%

Decameter mid-latitude sporadic-E irregularities in relation with gravity waves

Bourdillon¹,

Lefur²,

Haldoupis

et al. 1997

Ann Geophysicae

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Abstract. HF radar observations of mid-latitude sporadic-E irregularities carried out with the Valensole radar in South France are compared with simultaneous ionosonde measurements underneath the irregularity zones. In a previous study of Valensole radar data, it has been shown that HF backscatter from the night-time mid-latitude E region is usually associated with largescale wave-like modulations. To obtain more information on the geophysical conditions prevailing during backscatter events, a new experiment was performed which also included a vertical ionosonde beneath the scattering region. The data to be presented here are from two periods when radar scattering appeared simultaneously with large variations in the virtual height and the Doppler velocity of F-layer re¯ected echoes measured with the vertical ionosonde, indicating very clearly the passage of atmospheric gravity waves (AGWs). The e ect of the atmospheric waves on the sporadic-E layer is not always as marked as it is in the F region. In the ®rst event, the passage of the AGWs is accompanied by an upward followed by a downward movement of the Es-layer. The apparent descending movement of the Es-layer from 135 to 110 km in less than 10 min corresponded to a positive (downward) Doppler velocity of 35 m/s measured by the vertical ionosonde, and was accompanied by a range variation in the radar scattering region with a negative rate of about 90±110 m/s. In the second event, the Es-layer is not as strongly disturbed as in the previous one, but, nevertheless, the range variations of the scattering region can still be associated with height¯uctuations of the Es-layer.

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Section: Discussion and Concluding Remarksmentioning

confidence: 99%

Decameter mid-latitude sporadic-E irregularities in relation with gravity waves

Bourdillon¹,

Lefur²,

Haldoupis

et al. 1997

Ann Geophysicae

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“…Until the 1960s, most observers believed that plasma instabilities were responsible for spread F, but since then the focus of research has shifted toward disturbances produced by attoospheric gravity waves (see Bowman [1990] for a recent review). Nevertheless, sporadic experiments continued to produce evidence of disturbances that, while appearing related to gravity waves, were difficult to explain without invoking electrodynamic forces [Behnke, a series of theoretical and experimental exercises designed to explore the electrodynamics of midlatitude spread F. The three papers presented here are the first result of those efforts.…”

Section: Introductionmentioning

confidence: 99%

Electrodynamics of midlatitude spread F: 1. Observations of unstable, gravity wave‐induced ionospheric electric fields at tropical latitudes

Miller

Swartz²,

Kelley³

et al. 1997

J. Geophys. Res.

128

109

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“…This present paper will illustrate and discuss qualitatively some of these factors with the help of limited-range ionograms. In particular there will be discussion on the dynamic changes (over periods of seconds) which appear to apply to F-layer stratifications associated with spread-F and which were foreshadowed in a recent paper (BOWMAN, 1990) following some preliminary results. These preliminary results suggested night-time dynamic changes related to quasi-horizontal-trace (QHT) segments similar to those found for daytime events (see Fig.…”

Section: Introductionmentioning

confidence: 99%

“…It now seems likely (see BOWMAN, 1988BOWMAN, , 1990 that the most important mechanism operating to produce this spread is specular reflection from tilted surfaces (separated by some tens of kilometres) created during the passage of travelling ionospheric disturbances (TIDs), which in turn result from the presence of atmospheric gravity waves (AGWs) in the neutral atmosphere. However there are other factors operating which produce (or tend to produce) spread traces which appear diffuse.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Ionospheric Features Associated with the Fine Structure Recorded on Some Mid-Latitude Spread-F Ionograms.

Bowman

1991

J. geomagn. geoelec

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The main aim of this paper is to discuss and illustrate why the occurrence of diffuse mid-latitude spread-F ionograms suggests scattering from small-scale ionospheric structures as the primary cause of the spread, contrary to present ideas involving duplicate traces as the basic trace structures on sonograms. A number of factors which modify duplicate traces and tend to produce diffuseness are described. Sometimes these factors, which mainly involve interference effects due to overlapping traces, are so dominant that the diffuseness obscures any trace of the duplicate traces. In addition an important factor is the periodic replacement (sometimes recorded) of the quasi-horizontal-trace (QHT) segments of the duplicate traces (reported earlier for daytime events). These effects which are detected on fixedfrequency ionograms suggest that dynamic changes are occurring to ionospheric structures over and above those normally expected during the passage of a travelling ionospheric disturbance.

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A review of some recent work on mid-latitude spread-F occurrence as detected by ionosondes.

Cited by 154 publications

References 87 publications

Decameter mid-latitude sporadic-E irregularities in relation with gravity waves

Decameter mid-latitude sporadic-E irregularities in relation with gravity waves

Electrodynamics of midlatitude spread F: 1. Observations of unstable, gravity wave‐induced ionospheric electric fields at tropical latitudes

Ionospheric Features Associated with the Fine Structure Recorded on Some Mid-Latitude Spread-F Ionograms.

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