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<b>Small-action Particles in a Tokamak in the Presence of an <I>n</I> = 1 Mode</b>
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<p><b>Authors:</b> Ya.I. Kolesnichenko, V.V. Lutsenko, R.B. White, and Yu. V. Yakovenko</p>

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<b>Date of PPPL Report:</b> November 1999
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<b>Published in:</b> Phys. Rev. Lett. <b>84</b> (March 2000) 2152-2155.</p>

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It is found that an <i>m</i> = <i>n</i> = 1 mode with the amplitude exceeding a certain threshold can lead to stochastic motion of energetic ions in tokamaks, the large orbit width particles (potatoes) being most easily affected. An <i>n</i> = 1 mode can redistribute particles also in the absence of stochasticity but only when the perturbation is quickly switched on/off, e.g., due to sawtooth crash. In the latter case, the perturbation results in regular motion of particles around a certain helical orbit, at which a resonance driven by the mode but having no amplitude threshold takes place.
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