A global empirical model of effects of large-scale internal gravity waves in the night-time ionosphere

Deminova, G. F.; Shashun'kina, V. M.; Goncharova, E. E.

doi:10.1016/s1364-6826(97)00050-3

Cited by 23 publications

(26 citation statements)

References 14 publications

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“…leading to the increase or decrease in NmF2, respectively (Rees, 1995;Hocke and Schlegel, 1996). The analysis of fof2 measurements shows that night-time fof2 decreases due to gravity wave propagation are not so significant as by day (Deminova et al, 1998). As a result, we conclude that the identifiable greater probability of the NmF2 weak negative disturbances by day than at night, shown in the top panels of Figs.…”

Section: Nmf2 Weak Negative Disturbance Occurrence Probabilitiesmentioning

confidence: 62%

Solar zenith angle dependencies of F1-layer, <i>Nm</i>F2 negative disturbance, and G-condition occurrence probabilities

Lobzin

Павлов

2002

Ann. Geophys.

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Abstract. Experimental data acquired by the Ionospheric Digital Database of the National Geophysical Data Center, Boulder, Colorado, from 1957, are used to study the dependence of the G condition, F1-layer, and NmF2 negative disturbance occurrence probabilities on the solar zenith angle during summer, winter, spring, and autumn months in latitude range 1 (between −10 • and +10 • of the geomagnetic latitude, ), in latitude range 2 (10, and in latitude range 5 (60 • < | | ≤ 90 • ), where ϕ is the geographic latitude. Our calculations show that the G condition is more likely to occur during the first half of a day than during the second half of a day, at all latitudes during all seasons for the same value of the solar zenith angle. The F1-layer occurrence probability is larger in the first half of a day in comparison with that in the second half of a day for the same value of the solar zenith angle in latitude range 1 for all seasons, while the F1-layer occurrence probability is approximately the same for the same solar zenith angle before and after noon in latitude ranges 4 and 5. The F1-layer and G condition are more commonly formed near midday than close to post sunrise or pre-sunset. The chance that the daytime F1-layer and G condition will be formed is greater in summer than in winter at the given solar zenith angle in latitude ranges 2-5, while the F1-layer occurrence probability is greater in winter than in summer for any solar zenith angle in latitude range 1. The calculated occurrence probability of the NmF2 weak negative disturbances reaches its maximum and minimum values during daytime and night-time conditions, respectively, and the average night-time value of this probability is less than that by day for all seasons in all studied latitude regions. It is shown that the NmF2 normal, strong, and very strong negative disturbances are more frequent on average at night than by day in latitude ranges 1 and 2 for all seasons, reaching their maximum and minimum occurrence probability values at night and by day, respecCorrespondence to: A. V. Pavlov (pavlov@izmiran.rssi.ru) tively. This conclusion is also correct for all other studied latitude regions during winter months, except for the NmF2 normal and strong negative disturbances in latitude range 5. A difference in the dependence of the strong and very strong NmF2 negative disturbance percentage occurrences on the solar zenith angle is found between latitude ranges 1 and 2. Our results provide evidence that the daytime dependence of the G condition occurrence probability on the solar zenith angle is determined mainly by the dependence of the F1-layer occurrence probability on the solar zenith angle in the studied latitude regions for winter months, in latitude range 2 for all seasons, and in latitude ranges 4 and 5 for spring, summer, and autumn months. The solar zenith angle trend in the probability of the G condition occurrence in latitude range 3 arises in the main from the solar zenith angle trend in the F1-layer occurrence probability. The solar zenith ...

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Section: Nmf2 Weak Negative Disturbance Occurrence Probabilitiesmentioning

confidence: 62%

Solar zenith angle dependencies of F1-layer, <i>Nm</i>F2 negative disturbance, and G-condition occurrence probabilities

Lobzin

Павлов

2002

Ann. Geophys.

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“…The weak foF2 fluctuations can be also caused by the large-scale AGWs with the horizontal wavelengths larger than 1000 km generated in the auroral zone and propagating to the equator (Hocke and Schlegel, 1996;Fujiwara and Miyoshi, 2006). In the periods of insulated substorms the ionospheric effects of large-scale AGWs in the night hours are characterized by a marked increase of hmF2 and a slight decrease in foF2 (Deminova et al, 1998). This property of the ionosphere is likely to be also true for the short-period AGWs.…”

Section: Discussionmentioning

confidence: 95%

“…The extreme night enhancement in foF2 was accompanied by lowering of F2 layer. It is not typical for ionospheric effects of large-scale atmospheric gravity waves (AGWs) generated during the substorms, as AGWs usually cause the rise of the F2-layer (Hocke and Schlegel, 1996;Deminova et al, 1998). Thus the SA and the large-scale AGWs could not cause such enhancement in foF2.…”

Section: Anomalous Case Of Nwimentioning

confidence: 99%

Peculiarities of the nighttime winter foF2 increase over Irkutsk

Pirog

Dëminov

Deminova

et al. 2011

Advances in Space Research

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“…The suggested mechanisms for both the negative and positive responses involving neutral-particle densities and large scale travelling ionospheric disturbances (LS-TIDs) respectively have been dealt with in some detail in earlier papers (Bowman, 1995b and1998) and so will not be discussed further here. However it seems worth noting that recent results (Deminova et al, 1998;Hajkowicz, 1999) have found that height rises and electron-density depletions associated with LS-TIDs can be tracked from auroral-zone regions all the way to the equator. Thus they may be responsible for at least some of the pre-sunrise ESF.…”

Section: Discussionmentioning

confidence: 99%

Quantitative estimates of relationships between geomagnetic activity and equatorial spread-F as determined by TID occurrence levels

Bowman

Mortimer

2014

Earth Planet Sp

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Using a world-wide set of stations for 15 years, quantitative estimates of changes to equatorial spread-F (ESF) occurrence rates obtained from ionogram scalings, have been determined for a range of geomagnetic activity (GA) levels, as well as for four different levels of solar activity. Average occurrence rates were used as a reference. The percentage changes vary significantly depending on these subdivisions. For example for very high GA the inverse association is recorded by a change of −33% for R z ≥ 150, and −10% for R z < 50. Using data for 9 years for the equatorial station, Huancayo, these measurements of ESF, which indicate the presence of TIDs, have also been investigated by somewhat similar analyses. Additional parameters were used which involved the local times of GA, with the ESF being examined separately for occurrence pre-midnight (PM) and after-midnight (AM). Again the negative changes were most pronounced for high GA in R z -max years (−21%). This result is for PM ESF for GA at a local time of 1700. There were increased ESF levels (+31%) for AM ESF in R z -min years for high GA around 2300 LT. This additional knowledge of the influence of GA on ESF occurrence involving not only percentage changes, but these values for a range of parameter levels, may be useful if ever short-term forecasts are needed. There is some discussion on comparisons which can be made between ESF results obtained by coherent scatter from incoherent-scatter equipment and those obtained by ionosondes.

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A global empirical model of effects of large-scale internal gravity waves in the night-time ionosphere

Cited by 23 publications

References 14 publications

Solar zenith angle dependencies of F1-layer, <i>Nm</i>F2 negative disturbance, and G-condition occurrence probabilities

Solar zenith angle dependencies of F1-layer, <i>Nm</i>F2 negative disturbance, and G-condition occurrence probabilities

Peculiarities of the nighttime winter foF2 increase over Irkutsk

Quantitative estimates of relationships between geomagnetic activity and equatorial spread-F as determined by TID occurrence levels

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A global empirical model of effects of large-scale internal gravity waves in the night-time ionosphere

Cited by 23 publications

References 14 publications

Solar zenith angle dependencies of F1-layer, &lt;i&gt;Nm&lt;/i&gt;F2 negative disturbance, and G-condition occurrence probabilities

Solar zenith angle dependencies of F1-layer, &lt;i&gt;Nm&lt;/i&gt;F2 negative disturbance, and G-condition occurrence probabilities

Peculiarities of the nighttime winter foF2 increase over Irkutsk

Quantitative estimates of relationships between geomagnetic activity and equatorial spread-F as determined by TID occurrence levels

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Product

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Solar zenith angle dependencies of F1-layer, <i>Nm</i>F2 negative disturbance, and G-condition occurrence probabilities

Solar zenith angle dependencies of F1-layer, <i>Nm</i>F2 negative disturbance, and G-condition occurrence probabilities