Intrinsic Variability of the Vela Pulsar: Lognormal Statistics and Theoretical Implications

Individual pulses from pulsars have intensity-phase profiles that differ widely from pulse to pulse, from the average profile, and from phase to phase within a pulse. Widely accepted explanations for pulsar radio emission and its time variability do not exist. Here, by analysing data near the peak of the Vela pulsar’s average profile, we show that Vela’s variability corresponds to lognormal field statistics, consistent with the prediction of stochastic growth theory (SGT) for a purely linear system close to marginal stability. Vela’s variability is therefore a direct manifestation of an SGT state and the field statistics constrain the emission mechanism to be linear (either direct or indirect), ruling out nonlinear mechanisms like wave collapse. Field statistics are thus a powerful, potentially widely applicable tool for understanding variability and constraining mechanisms and source characteristics of coherent astrophysical and space emissions. Subject headings: methods: statistical — plasmas — pulsars: general — pulsars: individual (Vela) — radiation processes: non-thermal — waves