Mechanisms for the formation of electric-field pulsation spectra in the near-surface atmosphere

We present the results of detailed measurements of the spectrum of short-term (f ≃0.001–1 Hz) pulsations of the electric field of the near-surface atmosphere under fair-weather and fog conditions. It is shown that the electric-field pulsations at frequencies 10−2 –10−1 Hz have a power-law spectrum under both fair-weather and fog conditions. The spectral index varies in a range of from −1.23 to −3.36 depending on the experimental conditions, but the most probable values of the index fall in a range of from −2.25 to −3.0. The spectra corresponding to long time intervals of about a few hours are more steep. The relation of the spectral characteristics to the formation of aeroelectric structures (AESs) is studied. The distribution obtained for the structured spectra is bimodal, i.e., it exhibits two maxima in the ranges of spectral indices from −2.75 to −3.0 and from −2.25 to −2.5. The nonstructured-spectrum distribution is asymmetric and has a pronounced maximum corresponding to hard spectra with indices from −2.5 to −3.3. The intensity of the electric-field pulsations under fog conditions increases by about an order of magnitude compared to the case of fair-weather conditions. The mechanisms of spectrum formation of electric-field pulsations and their relations to the pulsation spectra of the electric-charge density with allowance for the neutral-gas turbulence and the presence of AESs are analyzed. We point out the key role of the nonlocal relation between the electric-field intensity and the space-charge density under conditions of spatially inhomogeneous turbulence. Model problems of the spectrum of electric-field fluctuations generated by a homogeneous and “structured” turbulence in the presence of charge-density fluctuations, considered as a passive tracer, are solved. © 2001 Plenum Publishing Corporation.