Abstract. Ultralow frequency pulsations of electric field in the surface atmospheric layer were investigated under fair weather conditions. A new method of structuraltemporal analysis has been applied to the study of spatiotemporal structures of the

[1] Short-term ( f ' 10 À3 -1 Hz) electric field pulsations in the surface atmospheric layer have been measured during 1999 -2001 under the fair-weather and fog conditions. At the frequencies of 10 À2 -1 Hz these pulsations have a power-law spectrum with the spectral index varying in the range from À1.23 to À3.36 while the most probable values of the index fall into the range from À2.25 to À3.0, unlike the temperature fluctuation spectra which obey in the inertial subrange the Kolmogorov power law with the spectral index close to À5/3. Under the fog conditions the intensity of electric-field pulsations increases by about an order of magnitude compared to the fair-weather conditions. The relation of spectral characteristics to the formation of aeroelectric structures (AESs) is evident; the spectral index distribution during AES flyby has two maxima. Analysis of the mechanisms explains the relationship between electricfield spectra and the neutral-gas turbulence and AES formation.

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As a result of electric field measurements in remote points of the surface layer and analysis of obtained statistical characteristics (structural function, temporal spectra) two typical scales of electric field pulsations are found. The lowest one L0 ≃ 20–60 m coincides with an external scale of neutral gas turbulence under fair weather conditions. The highest scale L1 ≳ 60 m testifies to the existence of long‐time electric field perturbations which lead to the anomalous growth of the structural function DE(r) at a distance r > L1. The relation between the scales L0 and L1 depends on the particular experimental conditions. The theoretical model for the function DE(r) has been developed, taking into account the turbulent mixing of charged particles and thermal convection in the surface layer. It is shown that the expression for DE consists of two parts. The first part describes fluctuations caused by the charge separation due to neutral gas turbulent mixing; the second part gives a contribution of large‐scale convective cells, which can transfer a volume charge along the Earth's surface.

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