Разностное уравнение возбуждения периодических волноводов нестационарным продольным током
We report the systematic analysis of zebra-like fine spectral structures in decametric frequency range of Jovian radio emission. Observations were performed by the large ground-based radio telescope URAN-2 during three observation campaigns between, Sep., 2012, and May, 2015. In total, 51 zebra pattern (ZP) events were detected. These rare fine radio features are observed in frequency range from 12.5 to 29.7 MHz as quasi-harmonically related bands of enhanced brightness. ZPs are strongly polarized radio emission with a duration from 20 s to 290 s and flux densities 105106 Jy (normalized to 1 AU), that is, 1–2 orders lower than for Iodecametric radio emission (DAM). Occurrence of the events does not depend on the position of Io satellite but is strongly controlled by the Jovian central meridian longitude (CML). ZPs are mainly detected in two active sectors of Jovian CMLs: 100 to 160 for Northern sources (right-handed polarized) and 300 and 60 (via 360) for the Southern sources (left-handed). The frequency interval between neighboring stripes is from 0:26 to 1:5 MHz and in most cases this interval increases with frequency. We discussed the double plasma resonance with electrons or ions as a possible source of the ZPs. The performed analysis of the observations allows us to conclude that the observed ZPs are a new type of narrow band spectral structures in the Jovian DAM.
A linear theory of the discrete interaction of electron beams and electromagnetic waves in slow-wave structures (SWS) is developed. The theory is based on the finite_difference equations of SWS excitation.The local coupling impedance entering these equations characterizes the field intensity excited by the electron beam in interaction gaps and has a finite value at SWS cutoff frequencies. The theory uniformly describes the electron–wave interaction in SWS passbands and stopbands without using equivalent circuits, a circumstance that allows considering the processes in the vicinity of cutoff frequencies and switching from the Cerenkov mechanism of interaction in a traveling wave tube to the klystron mechanism when passing to SWS stopbands. The features of the equations of the discrete electron–wave interaction in pseudoperiodic SWSs are analyzed.
With the help of the difference theory of excitation of periodic waveguides obtained by the characteristic equation of the electron waves formed by the interaction of an electron beam with the forward and backward electromagnetic waves periodic waveguides. The resulting characteristic equation describes the electron-wave interaction in the passband and stopband of periodic waveguides and includes as special cases of well-known equation for the «smooth» slow-wave systems and resonator slowwave systems near the cutoff frequency. Found a number of analytical solutions of the characteristic equation, which allowed to compare the properties of the amplification and propagation of electron waves inside and on the border of passband and stopband of periodic waveguides.