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

Abstract

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 ...

Investigation of Ionospheric Response to Geomagnetic Storms over a Low Latitude Station, Ile-Ife, Nigeria

“…There are several studies on responses of low latitude ionosphere to magnetic storms events (Sobral et al 1997, Pincheira et al 2002, Abdu 2001, Lobzin and Pavlov 2002aPavlov et al 2004, Lynn et al 2004, Lima et al 2004, Dashora et al 2009, de Siqueira et al 2011, D'ujanga et al 2013. A number of studies by Nigerian researchers have also been conducted on low latitudinal ionosphere responses during magnetic storm periods that have contributed to our understanding on this subject (Adeniyi 1986, Olawepo and Adeniyi 2012, Olawepo 2013, Ariyibi et al 2013a.…”

Longitudinal Variations of the Occurrence Probability of the Ionospheric F1 Layer Peak at Middle and High Latitudes

“…However, the electron density of the F 1 layer will not change much with the O/N 2 ratio. As we know, besides O + , the F 1 layer contains molecular ions, such as NO + and O 2 + (Lobzin & Pavlov, , ). This is different from the F 2 layer where the O + ions are dominant.…”

“…The N m F 1 is affected by but not determined by the O/N 2 ratio. As a result, the production and chemical loss processes of the F 1 layer are much more complicated than those in the F 2 layer, and the role of the O/N 2 ratio is more important in the F 2 layer (Lobzin & Pavlov, ). It is observed from COSMIC that the electron density of the F 1 layer peak does not change as significantly with longitude as it does in the altitude above at midlatitudes (Figures , , and ).…”

“…Furthermore, the local time dependence of the F 1 layer peak occurrence probability varies with latitude and season. For the same solar zenith angle (SZA), the F 1 layer peak occurrence probability is almost the same before and after noon for all seasons at middle latitudes, while it is higher in prenoon than in afternoon for all seasons in the equatorial region (Lobzin & Pavlov, ).…”

Ionosphere F2 layer stratification caused by shear excited atmospheric vortical perturbation

“…Here the case when the electron density of the lower peak is greater (see Fig. 3b) than that of the upper peak -the case similar to so called G condition for the mid-latitude ionosphere F region (e.g., see Lobzin and Pavlov, 2002), also occurs for some phase of shear wave. The lifetime of multi-layer structure in the ionosphere F2 region depends on the characteristic time of shear wave existence (t a ¼ 2k y =ak x ), which could be up to 1-3 h (Didebulidze and Pataraya, 1999).…”