 To characterize the distribution of the burst durations, we determine the distribution of exit points located on the two-dimensional separatrix \Sigma .
<clarity>  To characterize the distribution of the burst durations, we determine the distribution of exit points located on the two-dimensional separatrix \Sigma .
 To characterize the distribution of the burst durations, depends on the distribution of exit points located on the two-dimensional separatrix \Sigma .