Measurements and modelling of intermediate, descending, and sporadic layers in the lower ionosphere: Results and implications for global‐scale ionospheric‐thermospheric studies

Wilkinson, Phil; Szuszczewicz, E. P.; Roble, R. G.

doi:10.1029/91gl02774

Cited by 71 publications

(51 citation statements)

References 20 publications

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“…Wilkinson et al (1992) have proposed that a conventional ionosonde could provide long-term observations of the intermediate layers. Similarly, the digisonde can offer information on the intermediate layers for comparison during the daytime, like an incoherent radar.…”

Section: Discussionmentioning

confidence: 99%

“…− 10 10 el/m 3 form in the daytime and nighttime, respectively (Wilkinson et al, 1992;Mathews et al, 1993;Szuszczewicz et al, 1995;Earle et al, 2000).…”

Section: Thin (∼5 Kmmentioning

confidence: 99%

“…According to Wilkinson et al (1992) and Szuszczewicz et al (1995), the H and C type Es are attributed to the intermediate layers. Therefore, this statistical analysis implements only the H and C type Es to study the intermediate layers.…”

Section: Seasonal and Diurnal Variationsmentioning

confidence: 99%

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The intermediate layers and associated tidal motions observed by a digisonde in the equatorial anomaly region

et al. 2003

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Abstract. This investigation presents an initial attempt toanalyze a full year of daily ionosonde observations relevant to the determination of plasma densities, tidal structures, and ion transports in the equatorial anomaly region of the lower ionosphere. Particular focus is on the intermediate layers, their seasonal and diurnal variations, and cause-effect relationships. The ionogram database was recorded using a digisonde portable sounder (DPS) at National Central University (NCU, 24 • 58 N, 121 • 11 E) during 1996. Statistical results indicate that the intermediate layers appear primarily during the daytime of the spring/winter months. The monthly median height characteristics reveal that the layers descend from high to low altitudes and different tidal motions control the layers in different months. Generally, the semi-diurnal and quarter-diurnal tides, which cause ionization convergence, are mainly in the spring/winter and summer/autumn months, respectively. Variations in the electron densities of the layers also indicate that the density increases could result from a great number of molecular and metallic ions. Furthermore, a novel approach to ionogram presentation is introduced to investigate the intermediate layers. This approach allows the DPS to characterize the detailed daily information of the intermediate layers.

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Section: Discussionmentioning

confidence: 99%

“…− 10 10 el/m 3 form in the daytime and nighttime, respectively (Wilkinson et al, 1992;Mathews et al, 1993;Szuszczewicz et al, 1995;Earle et al, 2000).…”

Section: Thin (∼5 Kmmentioning

confidence: 99%

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The intermediate layers and associated tidal motions observed by a digisonde in the equatorial anomaly region

et al. 2003

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“…The latter, thanks to a combined action of the ion-neutral collisional coupling and the geomagnetic Lorentz force, trigger the long-lived metallic ions produced by the continuous meteoric shower activity to move vertically into the convergence node of the neutral horizontal wind vertical profile, thus forming dense and narrow ionization layers. More specifically, it has been found that the appearance and intensity of mid-latitude Es layers is influenced by vertical wind shears related to tidal waves, gravity waves and planetary waves, that compel the metallic and molecular ions into thin layers at altitudes from 95 to 120 km (Chimonas 1971;MacDougall 1974;Wilkinson et al 1992;Szuszczewicz et al 1995;Tsunoda et al 1998;Haldoupis & Pancheva 2002;Haldoupis et al 2004;Pignalberi et al 2014Pignalberi et al , 2015.…”

Section: Introductionmentioning

confidence: 99%

On the influence of solar activity on the mid-latitude sporadic E layer

Pezzopane

Pignalberi

Pietrella

2015

J. Space Weather Space Clim.

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To investigate the influence of solar cycle variability on the sporadic E layer (Es), hourly measurements of the critical frequency of the Es ordinary mode of propagation, foEs, and of the blanketing frequency of the Es layer, fbEs, recorded from January 1976 to December 2009 at the Rome (Italy) ionospheric station (41.8°N, 12.5°E), were examined. The results are: (1) a high positive correlation between the F10.7 solar index and foEs as well as between F10.7 and fbEs, both for the whole data set and for each solar cycle separately, the correlation between F10.7 and fbEs being much higher than the one between F10.7 and foEs; (2) a decreasing long-term trend of the F10.7, foEs and fbEs time series, with foEs decreasing more rapidly than F10.7 and fbEs; (3) clear and statistically significant peaks at 11 years in the foEs and fbEs time series, inferred from Lomb-Scargle periodograms.

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“…The 1 and f types (hereafter referred to as l/f type) occur during the day and night respectively. 'Ihe h-type develops around 150 km and descending in sequential ionograms (MacDougall, 1974;Wilkinson et al, 1992) becomes c-type E,. We therefore refer them as c/h type.…”

Section: Introduc'itonmentioning

confidence: 99%

Permanent changes in sporadic E layers over Fortaleza, Brazil

Abdu

Batista

MacDougall

et al. 1997

Advances in Space Research

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Data available on sporadic E layers in ionograms, from 1975 to 1995 over Fortaleza (38" W, 4' S) in Brazil are analysed as an extension of a previous study to examine permanent changes in the occurrence characteristics of the different types of E, layers. The so called q type E, produced by plasma instability (type II) process of the equatorial electrojet and the other types of E, produced by wind/wind shear mechanism are studied separately. The results show that while the occurrence of the former variety steadily decreased during the period of analysis, the latter type showed marked increases. These characteristics are shown to be associated mainly with the steady drifi of the magnetic equator to northward of Fortaleza at a rate of -0.2 degree per year. The long term trends are, however, modulated by solar activity cycle in F,, 7 flux. Also there is a suggestion of a possible effect from the June 1991 Pinatubo volcanic eruption. The competing roles of the neutral winds and electric fields in the formation of the low latitude sporadic E layer is demonstrated. INTRODUC'ITON'Ihere is an increasing interest in the scientific community to understand the permanent or long term changes that take place in the upper layers of the earth's atmosphere. It has been found that the ionosphere-thermosphere-mesosphere system presents better sensitivity to certain aspects of the long term changes than does the lower atmosphere (Rishbeth, 1996, this issue). Such changes could occur from natural such as solar-geophysical processes, secular changes in the earth's interior source of the geomagnetic field, volcanic eruptions, etc., or by anthropogenic sources. Reliable long term observational data base is necessary for investigating such changes. Further the task of identifying an observed change as arising from, say, anthropogenic activities requires detailed assessment of all other possible contributions from natural sources of such changes, and vice versa. In this paper we have focussed attention on aspects of long term changes arising from natural sources. We have examined the long term trend in the sporadic E-layer phenomenon over an equatorial station, Fortaleza, in Brazil using a 21-year (1975-1995) data base. This work which is an extension of a recent study published by Abdu et al. (1996), #at covered only the period [1975][1976][1977][1978][1979][1980][1981][1982][1983][1984][1985][1986][1987][1988][1989][1990], shows that significant changes of permanent nature have taken place for the sporadic E layer development conditions over Fortaleza. Such changes arise mainly from natural processes as will be explained in this paper. SPORADIC E-LAYER DATA SET Different types of E, layers occur in the equatorial electrojet and its low latitude vicinity regions. The q-type layer observed at 105-110 km in the day time equatorial ionograms is a manifestation of the type II irregularities of the equatorial electrojet (EEJ) produced by the well-known gradient E x B instability mechanism (Reid, 1960) that is primarily driven by...

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Measurements and modelling of intermediate, descending, and sporadic layers in the lower ionosphere: Results and implications for global‐scale ionospheric‐thermospheric studies

Cited by 71 publications

References 20 publications

The intermediate layers and associated tidal motions observed by a digisonde in the equatorial anomaly region

The intermediate layers and associated tidal motions observed by a digisonde in the equatorial anomaly region

On the influence of solar activity on the mid-latitude sporadic E layer

Permanent changes in sporadic E layers over Fortaleza, Brazil

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