Noise characteristics and instabilities of long Josephson junctions

The noise characteristics and chaotic behavior of long Josephson junctions in a magnetic field are investigated. In a magnetic field, current-biased junctions exhibit the dynamics of fluxon motion affected by fluctuations. These consist of telegraph noise at voltage steps and instabilities due to chaotic behavior. Results on long junctions with McCumber number ranging from 10 to 100 show such behavior. The telegraph noise is driven by thermal fluctuations. Modeling of the junctions using a perturbed sine-Gordon equation shows chaotic and periodic regions. Some of the chaotic regions are between Fiske steps, while others are at the edge of the Fiske steps. These observations are confirmed by numerical calculations.<
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