Articles | Volume 3, issue 2
Geosci. Instrum. Method. Data Syst., 3, 247–254, 2014
https://doi.org/10.5194/gi-3-247-2014
Geosci. Instrum. Method. Data Syst., 3, 247–254, 2014
https://doi.org/10.5194/gi-3-247-2014

Research article 23 Dec 2014

Research article | 23 Dec 2014

Validation of the k-filtering technique for a signal composed of random-phase plane waves and non-random coherent structures

O. W. Roberts, X. Li, and L. Jeska O. W. Roberts et al.
  • Department of Mathematics and Physics, Aberystwyth University, Aberystwyth, SY23 3BZ, UK

Abstract. Recent observations of astrophysical magnetic fields have shown the presence of fluctuations being wave-like (propagating in the plasma frame) and those described as being structure-like (advected by the plasma bulk velocity). Typically with single-spacecraft missions it is impossible to differentiate between these two fluctuations, due to the inherent spatio-temporal ambiguity associated with a single point measurement. However missions such as Cluster which contain multiple spacecraft have allowed for temporal and spatial changes to be resolved, using techniques such as k filtering. While this technique does not assume Taylor's hypothesis it requires both weak stationarity of the time series and that the fluctuations can be described by a superposition of plane waves with random phases. In this paper we test whether the method can cope with a synthetic signal which is composed of a combination of non-random-phase coherent structures with a mean radius d and a mean separation λ, as well as plane waves with random phase.