Dhrubaditya Mitra, Axel Brandenburg, Brahmananda Dasgupta, Eyvind Niklasson, Abhay Ram
We solve for the motion of charged particles in a helical time-periodic ABC (Arnold-Beltrami-Childress) magnetic field. The magnetic field lines of a stationary ABC field with $A=B=C=1$ are chaotic, and we show that the motion of a charged particle in such a field is also chaotic at late time with positive Lyapunov exponent. We further show that in time-periodic (frequency $\omega$) ABC fields the kinetic energy of a charged particle can increase indefinitely with time. At late times the mean kinetic energy grows as a power law in time with exponent $\xi$ that approaches unity. For an initial distribution of particles, whose kinetic energy is uniformly distributed within some interval, the PDF of kinetic energy is, at late time, close to a Gaussian but with steeper tails.
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http://arxiv.org/abs/1306.0151
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