A Hilbert-Huang transform approach to space plasma turbulence at kinetic scales

G Consolini,E Yordanova,T Alberti,M F Marcucci,M Echim

doi:10.1088/1742-6596/900/1/012003

Abstract

Heliospheric space plasmas are highly turbulent media and display multiscale fluctuations over a wide range of scales from the magnetohydrodynamic domain down to the kinetic one. The study of turbulence features is traditionally based on spectral and canonical structure function analysis. Here, we present an novel approach to the analysis of the multiscale nature of plasma turbulent fluctuations by means of Hilbert-Huang Transform (HHT). In particular we present a preliminary application of this technique to magnetic field fluctuations at kinetic scales in a fast solar wind stream as observed by Cluster mission. The HHT-energy spectrum reveals the intermittent and multiscale nature of fluctuation frequency at kinetic scales indicating that there are no-persistent and long standing frequencies.

Highlights

Several space plasma environments display complex dynamics characterized by multiscale processes, such as fluid and magnetoydrodynamic (MHD) turbulence
We get 18 and 19 Intrinsic Mode Functions (IMFs) for the magnetic field components and intensity, respectively. Each of this IMF is characterized by a mean characteristic time scale Tj that can be computed by measuring the average time interval between two successive zero-crossings of each IMFs
An interesting feature of Empirical Mode Decomposition (EMD) of the magnetic field components is that the components time series are decomposed into a set of IMFs characterized by the same periodicities

Summary

Introduction

Several space plasma environments display complex dynamics characterized by multiscale processes, such as fluid and magnetoydrodynamic (MHD) turbulence. In the framework of heliospheric plasmas, turbulence is a phenomenon widely occurring in several different regions: solar wind and interplanetary medium, Earth’s magnetosheath and tail central plasma sheet, etc. Among these regions the solar wind and the interplanetary medium are surely those where the turbulence has been extensively investigated since the early era of space missions [1]. The understanding and characterization of space plasma turbulence are fundamental to the modeling of plasma phenomena, such as plasma heating and acceleration, plasma transport across boundary regions, solar wind-magnetosphere coupling, etc. It has been clearly understood that the understanding of such phenomena requires a detailed study of turbulent fluctuations of magnetic field and plasma parameters on different timescales from MHD down to kinetic domain

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Conclusion