Quasi-adiabatic dynamics of ions in a bifurcated current sheetстатья
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Дата последнего поиска статьи во внешних источниках: 31 декабря 2013 г.
Аннотация:The study is devoted to ion dynamics in bifurcated current sheets with a twopeak currentdensity distribution observed in the Earth’s magnetotail and solar wind. The ion motion is described by a Hamiltonian system with two degrees of freedom. The presence of a small parameter κ characterizing the ratio between the amplitudes of the normal and tangential magnetic field components allows one to separate variables into fast and slow ones and introduce the quasiadiabatic invariant of motion Iz. Conservation of this invariant makes it possible to analytically describe the dynamics of charged particles. Deviations of the particle dynamics from the quasiadiabatic one, which are caused by the nonconservation of the quasiadiabatic invariant, are investigated. The jump of the invariant ΔIz is shown to depend on the small parameter according to the powerlaw ΔIz ~ κh, where the exponent h varies between unity and 3/4, depending on the level of current sheet bifurcation. The obtained dependence of ΔIz on κ coincides with analytic expressions in the limiting cases of nonbifurcated and completely bifurcated current sheets.