Vol 59, No 7 (2016)

We obtain average global distributions of the variances of the mesoscale variations in the atmospheric radio-refraction index (refractive index) at altitudes of 5–35 km from the data of the radio-occultation experiments performed during operation of the low-orbit GPS CHAMP satellite in the period 2001–2009. The filtering of the vertical profiles of the radio-refraction index allows one to determine the variances of the variations with vertical scales below 8 km. The latitudinal-temporal distributions of the zonal-mean variances of the index demonstrate significant interannual variations at various altitudes. Seasonal variations in the variances of radio refraction are studied. Quasi-biennial oscillations at low latitudes are revealed. Acoustic-gravity waves and turbulent and convective motions in the atmosphere can cause a spread of the radio-refraction index.

We examine the features of the electromagnetic emission of a compact intracloud discharge (CID) within the framework of the fractal approach [1] described in the first part of the article. Compact intracloud discharge is considered as the result of electric interaction of two bipolar streamer-type structures previously developed in the regions of a strong electric field inside the thundercloud. To estimate the electromagnetic emission of the discharge, the complex tree-like structure of the electric currents at the preliminary and main stages of CID was represented as the sum of a relatively slowly varying large-scale linear mean component and fast small-scale constituents corresponding to the initial formation of elementary conductive channels of the discharge tree. Mean linear current of the discharge is considered as an effective source of the VLF/LF emission at both the preliminary and main stages of a CID. Electrostatic, induction, and radiation components of the electric field at different distances from the mean current are calculated taking into account specific features of both stages of the discharge within the framework of the transmission-line model. It is shown that at the preliminary stage only the electrostatic component can mainly be detected, whereas at the main stage all the above components of the electric field can be reliably measured. Dependence of the radiation electric field at the main stage on the length of the discharge channel and propagation velocity of the current front is analyzed. It is found that due to the bi-directional expansion of the current at the main stage of a CID the radiation field pulse remains narrow in a wide range of discharge parameters. The small-scale currents corresponding to the initial breakdown between the neighboring cells of the discharge domain are considered as the sources of HF/VHF radiation. It is shown that HF/VHF emission at the preliminary stage is negligible as compared to emission at the main stage. It is also established that at the main stage, first, the HF/VHF emission burst correlates well with the initial peak of the VLF/LF electric field pulse and, second, its spectrum corresponds to the power law with an exponent between −2 and −1.

We consider the properties of thin-walled, strongly magnetized electron beams in closed evacuated transportation channels with arbitrary cross sections of the channel and the electron beam. Explicit precise formulas are obtained for the limiting and Fedosov’s currents of such electron beams. The found relationships allow one to explain many observed phenomena and can serve as a basis for verification of the results of more complicated calculations.