Vertical structure of the midlatitude winter F region of the ionosphere during postmidnight enhancements in NmF2

Yakovets, A. F.; Vodyannikov, V. V.; Gordienko, G. I.; Litvinov, Yu. G.

doi:10.1134/s0016793209040094

Cited by 8 publications

(12 citation statements)

References 7 publications

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“…As exhibited in Figure 1, the enhancements in Qujing NmF2 at daytime and sunset are characterized by a simultaneous descent in hmF2. It is different from the feature at middle latitudes (Chen et al, 2016;He et al, 2009;Luan et al, 2008;Yakovets et al, 2009). One may possibly argue about that the enhancement in NmF2 is the consequence of the lift in hmF2 before its descent, not the effect of simultaneous changes in hmF2.…”

Section: Nmf2 and Hmf2mentioning

confidence: 83%

New Features of the Enhancements in Electron Density at Low Latitudes

Liu

Zhang²,

et al. 2020

JGR Space Physics

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In this study, we present some new features of the enhancements of electron density in the ionospheric F region at low latitudes. The peak parameters of the ionosphere were recorded by Sanya (109.6°E, 18.3°N) ionosonde and electron density profiles analyzed were measured by the Qujing (103.8°E, 25.6°N) incoherent scatter radar. The peak electron density of the F2 layer (NmF2) is found to be enhanced in the afternoon and sunset hours. Common features in the cases demonstrate that the NmF2 increases at low latitudes are characterized by a descent of the peak height (hmF2). Meanwhile, the electron density at Qujing shows an increase at the bottom of the ionosphere and a depression at topside altitudes. It is consistent with those of the ionosonde measurements at Sanya, for both the daytime and nighttime enhancements. Cross correlation analyses reveal a lag of NmF2 to hmF2 in the cases. After taking time shifts some events of the enhancements in NmF2 are still associated with a downwelling hmF2, confirming the processes which drive a lower hmF2 and a convergence of plasma flux may possibly bring about a rise in NmF2.

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Section: Nmf2 and Hmf2mentioning

confidence: 83%

New Features of the Enhancements in Electron Density at Low Latitudes

Liu

Zhang²,

et al. 2020

JGR Space Physics

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“…Different physical mechanisms were proposed to explain the formation of INE, such as the combined effect of the ionospheric uplifting caused by equatorward neutral winds and the long-lasting photoionization in the ionosphere after sunset (e.g., Chen et al, 2012;Horvath, 2006), the downward diffusion from the topside ionosphere or the plasmasphere (e.g., Burns et al, 2008;Evans, 1965;Li et al, 2018), and the plasma transport between the conjugated hemispheres (e.g., Bailey et al, 1991;Förster & Jakowski, 1988). Changes of the F2-layer height usually play important roles in ionospheric variations (e.g., Liu et al, 2013;Yakovets et al, 2009), because recombination loss significantly depends on the F2-layer height. The F2-layer height strongly depends on vertical plasma transport processes; it can be indicated by the ionospheric parameter hmF2 (the peak height of the ionospheric F2 layer).…”

Section: Introductionmentioning

confidence: 99%

A Statistical Study on the Winter Ionospheric Nighttime Enhancement at Middle Latitudes in the Northern Hemisphere

Chen

Liu

et al. 2020

JGR Space Physics

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The ionospheric electron density generally decreases after sunset under the effect of recombination, but sometimes, it increases, which forms an ionospheric nighttime enhancement (INE). In this research, the observations from two ionosondes in Mohe and Beijing and NASA's Jet Propulsion Laboratory‐Global Ionosphere Maps during the 24th solar cycle were used to explore the feature and mechanism of INE at midlatitudes. It shows that hmF2 always increases when INE occurs in summer, while it either rises or falls in winter. The increase of hmF2 has a significant contribution to INE in summer. For winter INE, however, the hmF2‐rising and the hmF2‐declining type INEs present no significant differences in durations and amplitudes, except that the former occurs slightly earlier than the latter. This suggests that the uplift of the ionosphere induced by equatorward thermospheric wind may not be a dominant factor for controlling the formation of winter INE at midlatitudes. We found that the electron density difference between the summer hemisphere and the winter hemisphere trends increases when the INE occurs in the winter hemisphere. This increased electron density difference between the two hemispheres is beneficial to the summer‐to‐winter interhemispheric plasma transport and the formation of INE in winter. Meanwhile, it is likely that the ionospheric equivalent slab thickness decreases during the winter INE due to downward transport from the topside. These indicate that downward plasma influxes from the topside ionosphere and the conjugate summer hemisphere play dominant roles for the formation of winter INE at middle latitudes.

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“…[3] Lots of investigations have been conducted extensively to study the nighttime enhancements either in total electron content [e.g., Arendt and Soicher, 1964;Titheridge, 1968;Young et al, 1970;Davies et al, 1979;Rao, 1984, 1987;Balan et al, 1994;Horvath, 2006;Unnikrishnan et al, 2002;Chen et al, 2008;Jain et al, 2011;Trivedi et al, 2013] or in critical frequency (foF2) or peak electron density (NmF2) of the F2 layer [Farelo et al, 2002;Tsagouri and Belehaki, 2002;Mikhailov et al, 2000;Pavlov and Pavlova, 2007;Yakovets et al, 2009;Pezzopane et al, 2011;Pirog et al, 2011] or in both of them [Essex and Klobuchar, 1980;Jakowski et al, 1991;Gordienko et al, 2001]. Moreover, observations from incoherent scatter radars [Pavlov and Pavlova, 2005], tomographic images [Dabas and Kersley, 2003], and radio occultations [Luan et al, 2008;He et al, 2009] have also been analyzed to reveal features and physical processes involved in the enhancement phenomena.…”

Section: Introductionmentioning

confidence: 99%

A case study of postmidnight enhancement in F‐layer electron density over Sanya of China

et al. 2013

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[1] The electron density in the ionospheric F region occasionally stops its decay and rises pronouncedly during night hours, which are termed ionospheric nighttime enhancements. In this case study, we analyzed the manually scaled ionogram records measured by a Lowell DPS-4D ionosonde operated at Sanya (18.3°N, 109.6°E), China, to explore postmidnight enhancement events occurred in 2012, a year of moderate solar activities. Common features in these cases illustrate that, accompanying nighttime rises in peak electron density of F2 layer (NmF2), the height of F2 layer is depressed significantly, and the ionogram-derived electron density height profiles become thinner. There are time shifts in the development of electron density enhancements in the F layer; that is, enhancement develops earlier and reaches peaks earlier at higher altitudes than at lower altitudes. Meanwhile, plasma drift is detected downward under such events, revealing the essential role of the westward electric field in forming the postmidnight enhancements in electron density of ionospheric F layer at such low latitudes.

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Vertical structure of the midlatitude winter F region of the ionosphere during postmidnight enhancements in NmF2

Cited by 8 publications

References 7 publications

New Features of the Enhancements in Electron Density at Low Latitudes

New Features of the Enhancements in Electron Density at Low Latitudes

A Statistical Study on the Winter Ionospheric Nighttime Enhancement at Middle Latitudes in the Northern Hemisphere

A case study of postmidnight enhancement in F‐layer electron density over Sanya of China

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