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Article

The Role of Wind Velocity, Wind Shear, and Electric Fields in the Formation of Sporadic E (Es)

by
Goderdzi G. Didebulidze
1,*,
Giorgi Dalakishvili
1 and
Maya Todua
1,2
1
Center of Space Research, Ilia State University, G. Tsereteli Str 3a, 0162 Tbilisi, Georgia
2
E. Kharadze Georgian National Astrophysical Observatory, M. Kostava Str, 47/57, 0108 Tbilisi, Georgia
*
Author to whom correspondence should be addressed.
Atmosphere 2025, 16(9), 1002; https://doi.org/10.3390/atmos16091002
Submission received: 6 June 2025 / Revised: 9 August 2025 / Accepted: 15 August 2025 / Published: 24 August 2025
(This article belongs to the Special Issue Ionospheric Irregularity (2nd Edition))

Abstract

The important role of neutral wind, its vertical shear, and external electric fields in the formation and localization of sporadic E (Es) are demonstrated analytically and numerically in equatorial and mid-latitude regions. The ion/electron density behavior, obtained analytically, indicates that their initial layer moves vertically at ion drift velocity. When the maximal total ion vertical convergence rate (MTotIVCR) (the minimal negative value of the ion drift velocity divergence), determined according to the wind velocity, wind shear, and electric field, exceeds ion/electron loss due to recombination and diffusive displacement, the initial layer peak density increases, and ion accumulation into narrow, high-density Es-type layers becomes possible. In this case, the Es layers formed localize either in the region surrounding ion drift velocity nodes or where they are frequently observed (around 100–105 km), where drift velocity disappears. Analysis and numerical simulations also show that an increase in the downward drift velocity and the total ion vertical convergence rate (TotIVCR), including the effects of westward or/and downward electric fields and westward or/and northward neutral wind, can also result in additional increases in the Es layer density as it descends to its localization region. The important contributions of the directions and magnitudes of meridional and zonal winds (using HWM14 data), wind shear, and electric field (using four different polarizations) to the vertical drift velocity of ions and, accordingly, the MTotIVCR (about 10−3–10−4 s−1), are evident during the formation of Es layers in typical equatorial regions (with magnetic inclination I = 0 and 0.5° N; 195° E) and between equatorial and mid-latitude (BEML) (I = 30°; 16° N; 195° E) and mid-latitudes (I = 60°; 45° N, 195° E) regions. For the zonal wind data and zonal and vertical components of the electric field considered, the importance of the electric field in the increase in the TotIVCR and the corresponding formation and localization of Es layers in the equatorial region is shown. If an electric field is present at mid-latitudes, it also can affect the increase or decrease in the TotIVCR and the localization of Es layers. It also has the ability to destroy these layers, which are formed under the combined effect of meridional and zonal wind velocities and vertical shear. In this case, the electric field also affects increases in the meridional wind factor with latitude in the formation and localization of high-density Es layers. This study shows that in addition to considering the vertical shear of neutral wind, it is necessary to take into account its magnitude and direction and the presence of electric fields to predict the possibility of sporadic E (Es) formation and localization.
Keywords: sporadic E; the role of wind velocity, wind shear and electric field in formation of Es layers. sporadic E; the role of wind velocity, wind shear and electric field in formation of Es layers.

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MDPI and ACS Style

Didebulidze, G.G.; Dalakishvili, G.; Todua, M. The Role of Wind Velocity, Wind Shear, and Electric Fields in the Formation of Sporadic E (Es). Atmosphere 2025, 16, 1002. https://doi.org/10.3390/atmos16091002

AMA Style

Didebulidze GG, Dalakishvili G, Todua M. The Role of Wind Velocity, Wind Shear, and Electric Fields in the Formation of Sporadic E (Es). Atmosphere. 2025; 16(9):1002. https://doi.org/10.3390/atmos16091002

Chicago/Turabian Style

Didebulidze, Goderdzi G., Giorgi Dalakishvili, and Maya Todua. 2025. "The Role of Wind Velocity, Wind Shear, and Electric Fields in the Formation of Sporadic E (Es)" Atmosphere 16, no. 9: 1002. https://doi.org/10.3390/atmos16091002

APA Style

Didebulidze, G. G., Dalakishvili, G., & Todua, M. (2025). The Role of Wind Velocity, Wind Shear, and Electric Fields in the Formation of Sporadic E (Es). Atmosphere, 16(9), 1002. https://doi.org/10.3390/atmos16091002

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