Higher-Order Statistics and Nonlinear Processes in Space Plasmas

Statistics of order 2 (varlance, auto and cross-correlation runctions, auto and cross-power spectra) and 3 (skewness, auto and cross-bicorrelation functlons, auto and cross-bispectra) are used t0 analyzethe wave-partlcle interaction ln space plasmas. The signals consldered here are medium scaIe electron densityirreguIarities and ELF/ULF electrostatlc turbulence. Nonlinearities are mainly observed in the ELF range.They are independently p0lnted out ln time serles assoclated with rluctuations in electronic density and in timeseries associated with the measurement if one electric field component. Peaks in cross-bicorrelation functionand in mutual ln formation clearly show that, ln well dellmlted rrequency bauds, the wave-particle interactions are nonlinear above a certain Ievel of fluctuatlons. The way the energy is transrerred within the frequencies of denslty rluctuations is indlcated by a bl-spectra analysls.