Vol 62, No 5 (2019)

A significant difference was found in the amplitude and polarization spectra of ULF magnetic noise at stations with a base of 120 km during periods of absence of regional thunderstorm activity. A simultaneous analysis of low-frequency data and ionosonde data allowed us to conclude that the difference in the main parameters of the polarization spectrum at two stations is due to the appearance of sporadic E_s layers having a nonuniform horizontal intensity distribution with characteristic scales of the order of the base between stations. A difference in the depth of variations in the polarization parameter ε was also found during the ionosphere recovery after magnetic storms. It could be related with Es layers, which had not only a nonuniform intensity distribution, but were also located at different altitudes. A difference was found in the frequency scales of the spectral resonance structure during recording of time variations of its fundamental frequencies. Numerical calculations of the parameter ε with specifying model E_s layers and electron-density profiles corrected at the altitudes of the ionospheric F layer adequately explained the observed difference in the magnetic noise spectra and allowed us to determine the altitudes at which the horizontal ionospheric irregularity existed. The studies were carried out on the basis of records of horizontal magnetic components at Radiophysical Research Institute midlatitude observatories Novaya Zhizn (56° N, 45.74° E) and Staraya Pustyn (55.66° N, 43.63° E, 120 km east of the first reception point).

We study theoretically the possibilities of double-stage energy recuperation in a double-beam terahertz gyrotron. Numerical modeling, which was performed for a gyrotron producing radiation with a frequency of 0.78 THz and operating at the second cyclotron-frequency harmonic at the TE_8.5 mode, demonstrates the possibility of spatial and energy separation of electron beams. This makes it possible to implement a double-stage recuperation scheme. The found energy spectra of electrons suggest an increase in the gyrotron efficiency by 3.5–4 times.

We determine the upper limit on the correct measurement disambiguation probability in multiscale phase-measuring systems in which all scales are ambiguous. The measured value is estimated by the maximum likelihood method from the total of measured phase differences supplemented by an algorithm for rejecting (erasing) measurement results with anomalously large errors. Errors that exceed one-half of the main lobe of the likelihood function are considered anormalously large. The results are obtained by the methods of linear algebra with a geometric interpretation of the measurement disambiguation process in the space of total phase differences. The method was applied to phase direction finders, but can easily be adapted to other types of multiscale phase radio systems.