The stability of charged-particle motion in sheared magnetic reversals

Abstract

Abstract. We consider the motion of charged particles in a static magnetic reversal with a shear component, which has application for the stability of current sheets, such as in the Earth's geotail and in solar flares. We examine how the topology of the phase space changes as a function of the shear component b y . At zero b y , the phase space may be characterized by regions of stochastic and regular orbits (KAM surfaces). Numerically, we find that as we vary b y , the position of the periodic orbit at the centre of the KAM surfaces changes. We use multiple-timescale perturbation theory to predict this variation analytically. We also find that for some values of b y , all the KAM surfaces are destroyed owing to a resonance effect between two timescales, making the phase space globally chaotic. By investigating the stability of the solutions in the vicinity of the fixed point, we are able to predict for what values of b y this happens and when the KAM surfaces reappear.

Quasiadiabatic description of nonlinear particle dynamics in typical magnetotail configurations

“…A range of parameters for which the structure obtained for stationary field configurations survive in the presence of the electromagnetic waves was obtained analytically in Vainchtein et al (2004). The role of the cross-tail component of the magnetic field in the MFR region was first discussed in Karimabadi et al (1990) and later studied, both analytically and numerically, in many papers, including Büchner and Zelenyi (1991); Zhu and Parks (1993);Chapman and Rowlands (1998);Ynnerman et al (2000); Tsalas et al (2001). It was shown that for a certain range of the ratios of the typical values of the components of the magnetic field the structures obtained for two-dimensional model stay qualitatively the same even in the presence of the third component.…”