Study of fine spatial structures of the daytime sporadic E layer and its temporal evolution by using an ultra-dense GNSS receiver network

Abstract The sporadic E (Es) layer is an ionospheric layer of very high density in the E region. Prediction of the Es layer generation is not yet possible. To understand the generation mechanisms, the structures of the Es layer and their evolution were studied. Data a ultra-dense global navigation satellite system (GNSS) network over Japan operated by SoftBank, rate-of-total electron content (ROTI) maps with $$0.05^\circ \times 0.05^\circ$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>0</mml:mn> <mml:mo>.</mml:mo> <mml:msup> <mml:mn>05</mml:mn> <mml:mo>∘</mml:mo> </mml:msup> <mml:mo>×</mml:mo> <mml:mn>0</mml:mn> <mml:mo>.</mml:mo> <mml:msup> <mml:mn>05</mml:mn> <mml:mo>∘</mml:mo> </mml:msup> </mml:mrow> </mml:math> resolutions in the latitude and longitudes (approximately 5 $$\times$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mo>×</mml:mo> </mml:math> 5 km at the E region altitudes) were derived. Complex fine horizontal structures of the sporadic E (Es) layer which occurred over Japan in the daytime on 17 May 2024 were imaged. Fine-scale structures of the Es layer and their temporal evolution from generation to decay were elucidated. The complex structures, chain of small patches, vortices, and ripples were observed. The scale size and lifetime were similar to those predicted by high spatial resolution numerical simulations. Future studies include the statistics of occurrences of different complex shapes, scale sizes of them, area of the Es layer, and lifetime. Graphical Abstract