Том 62, № 2 (2019)

We present the results of studying the influence of solar and magnetic activity in September 2017 on the HF signal characteristics on subauroral and midlatitude paths. A connection between the ionospheric effects caused by the magnetic storm and the magnetic disturbance intensity is established. It is shown that the formation of a strong sporadic E_s layer in the auroral ionosphere during a magnetic storm makes it possible to use the propagation mode with reflection from E_s in the interests of HF communication to neutralize the effects of the negative phase of the storm and absorption growth when unfavorable conditions for the F-mode propagation with reflection from the upper ionosphere occur.

We solve the problem of determining the power of the received scattered optical radiation from external laser beams, which propagate in the Earth’s atmosphere, by passive lidar in a weakly turbid transparent atmosphere and also determine the lidar operation radius. Under the night conditions without solar illumination, the lidar operation radius can exceed 2300 km when detecting the beams with powers is about 100 kW. In the presence of solar illumination, the operation radius decreases by an order of magnitude. For a small power of the external beam, the experimental and theoretical data are in good agreement, which makes it possible to extrapolate the obtained theoretical results to larger powers of the external beams with allowance for the radiation loss because of the secondary Rayleigh scattering.

In our previous paper [1] it was shown, using the theory of antennas in plasmas, that the effective length l_eff of a receiving dipole antenna can be much larger than its geometric length in case quasielectrostatic chorus emissions propagating close to the resonance cone are received. In order to simplify calculations of l_eff, it was proposed to use a model (“effective”) source of such emissions because taking into account all of the real source properties (that are determined by the nonlinear processes of interaction between waves and charged particles in a wide region of space) would lead to unreasonably cumbersome calculations. The present paper analyzes how the effective length of the spacecraft-borne receiving antenna depends on the parameters of the space charge distribution in the model source of quasi-electrostatic chorus emissions. It is found that the length l_eff decreases as a power function (with exponent −1/2) with increasing distance (along the group velocity resonance cone) between the model source and the receiving antenna. This relationship is correct up to the distance at which the effective length becomes of the order of the geometric length. At longer distances, the radiation field loses its resonance nature because of the excitation of an electromagnetic (quasi-longitudinal) wave. It is shown that under conditions of the Earth’s magnetosphere, the approximation we used can remain valid up to distances of the order of the geomagnetic field line length, which confirms the importance of the discussed effect for correct interpretation of the electric wave measurement data in the whistler-mode frequency range. It is also shown that the length l_eff changes by less than 10% when the characteristic scale of spectrum of the charge distribution along the model source varies as Δ ∼ (0.1–1.0) k_obs, where the wave number k_obs corresponds to the observed spectral maximum of radiation at a given frequency.

We detect the second discharge mode in the process of experimental studies of a one-sided multipactor discharge in crossed fields (microwave electric field and magnetostatic field) in the three-centimeter wavelength band in a rectangular waveguide and a cylindrical resonator cavity. In accordance with the theory, the intensity of the discharge at the second mode was slightly lower than that at the fundamental mode. However, it is still sufficient for initiation of microwave breakdowns, absorption of a significant fraction of the radiation power, and modification of the resonance frequency of the cavity.