L.G. Kurakin, I.V. Ostrovskaya. On the stability of Thomson vortex N–gon and vortex tripole/quadrupole in geostrophic models of Bessel vortices and in two-layer rotating fluid: a review. Russian Journal of Nonlinear Dynamics, 2019, v. 15, №4, pp. 533–542.

In this paper the two-layer geostrophic model of the rotating fluid and the model of Bessel vortices are considered. Kirchhoff’s model of vortices in a homogeneous fluid is the limiting case of both of these models. Part of the study is performed for an arbitrary Hamiltonian depending on the distances between point vortices. The review of the stability problem of stationary rotation of regular Thomson’s vortex N-gon of identical vortices is given for N > 2. The stability problem of the vortex tripole/quadrupole is also considered. This axisymmetric vortex structure consists of a central vortex of an arbitrary intensity and two/three identical peripheral vortices. In the model of a two-layer fluid, peripheral vortices belong to one of the layers and the central vortex can belong to either another layer or the same. The stability of the stationary rotation is interpreted as orbital stability (the stability of a one-parameter orbit of a stationary rotation of a vortex system). The instability of the stationary rotation is instability of equilibrium of the reduced system. The quadratic part of the Hamiltonian and eigenvalues of the linearization matrix are studied.