A physical mechanism for the generation of slow and fast electromagnetic-type planetary waves due to standing factorlatitude variation of geomagnetic ΓΏeld-in the dissipative E-region of the ionosphere is suggested. It has been shown that slow waves are generated due to the dynamo-ΓΏeld in the ionosphere, and fast waves by the vortical electric ΓΏeld. The slow electromagnetic wave is analog to the Rossby planetary wave; the fast electromagnetic wave is a new mode of natural oscillations of the E-region of the ionosphere. Linear waves propagate along the parallel west and east directions in the dynamo-region of the ionosphere against a background of the mean zonal ow. Phase velocity of the fast waves is a few km s -1 , oscillation frequencies are in the frequency band of 10 -2 -10 -4 s -1 and the wavelength is of the order of 10 3 km and higher. Phase velocities of the slow waves and local winds are at the same order of magnitude, the frequency band is 10 -4 -10 -5 s -1 and wavelength is of 10 3 km and higher order. Fast waves generate intense magnetic ΓΏelds in order of a few hundred nanotesla (nT); slow waves-a few tens of nT.
In this paper the nonlinear theory of both fast and slow planetary electromagnetic waves in the E-region of the ionosphere is investigated for the ΓΏrst time. It was established that these perturbations are self-localized as nonlinear solitary vortical structures in the dynamo-region of the ionosphere move to the west (fast) and to the east (slow) against a background of the mean zonal ow. The nonlinear structure consists of cyclone-anticyclone-type mutual counter-clockwise-rotating vortices, which capture medium particles. Energy and enstrophy of these large-scale vortices are weakly attenuated and are long-lived. Vortical structures generate magnetic ΓΏelds, which are an order of magnitude larger than those generated by the corresponding linear waves. Features and parameters of electromagnetic wavy structures are theoretically investigated and are in good agreement with the experimental data of large-scale ULF wavy perturbations observable in the ionosphere.