Lifetime estimate for plasma turbulence

A method is proposed to experimentally determine the intrinsic timescale or a decay rate of turbulent fluctuations. The method is based on the assumption that the Breit–Wigner spectrum model with a non-Gaussian frequency broadening is valid in the data analysis. The decay rate estimate is applied to the multispacecraft magnetic field data in interplanetary space, yielding the decay rate on spatial scales of about 1000 km (about 10 times larger than the ion inertial length), which is higher than the theoretical predictions from the random sweeping timescale of the eddy turnover time. The faster decay of fluctuation components in interplanetary space is interpreted as a realization of plasma physical (and not fluid mechanical) processes.

Lifetime estimate for plasma turbulence

A method is proposed to experimentally determine the intrinsic time scale or a decay rate of turbulent fluctuations. The method is based on the assumption that the Breit-Wigner spectrum model with a non-Gaussian frequency broadening is valid in the data analysis. The decay rate estimate is applied to the multi-spacecraft magnetic field data in interplanetary space, yielding that the result that the decay rate on spatial scales of about 1000 km (about 10 times larger than the ion inertial length) is higher than the theoretical predictions from the random sweeping time scale of the eddy turnover time. The faster decay of fluctuation components in interplanetary space is interpreted as a realization of plasma physical (and not fluid mechanical) process.

Time–frequency analysis of the sea state with the Andrea freak wave

The nonlinear and nonstationary properties of a special field wave record are analysed with the Wigner spectrum with the Choi–Williams kernel. The wave time series, which was recorded at the Ekofisk complex in the central North Sea at 00:40 UTC (universal time coordinated) on 9 November 2007, contains an abnormally high wave known as the "Andrea" wave. The ability of the Wigner spectrum to reveal the wave energy distribution in frequency and time is demonstrated. The results are compared with previous investigations for different sea states and also the state with Draupner's abnormal "New Year" wave.

Time-frequency analysis of the sea state with the "Andrea" freak wave

The non-linear and non-stationary properties of a special field wave record are analyzed with the Wigner spectrum with the Choi–Williams kernel. The wave time series, which was recorded at the Ekofisk complex in the Central North Sea at 00:40 UTC on 9 November 2007, contains an abnormally high wave known as "Andrea" wave. The ability of the Wigner spectrum to reveal the wave energy distribution in frequency and time is demonstrated. The results are compared with previous investigations for different sea states and also the state with the abnormal Draupner's New Year wave.