Evidence for Nonlinear Development of MHD scale Intermittency in the Inner Heliosphere

GRECO, A.; MATTHAEUS, W. H.; D'AMICIS, R.; DMITRUK, P.; SERVIDIO, S.

Conferencia; American Geophysical Union, Fall Meeting 2011; 2011

The development of coherent structures in turbulence is a signature of a developing cascade and therefore might be observable by analysis of inner heliospheric solar wind turbulence. To test this idea, data from the Helios 2 mission, for six streams of solar wind, is subject to statistical analysis using the Partial Variance of Increments (PVI) approach. We see a clear increase of PVI distribution function vs solar wind age for higher PVI cutoff, indicating development of nonGaussian coherent structures. To confirm plausibility of this interpretation, similar development is described min three dimensional magnetohydrodynamic simulation data at corresponding dimensionless nonlinear time scales. This result suggests that the solar wind is evolving towards a more fully developed state in the inner heliosphere, developing intermittency as it progresses. Implications for the Solar Probe mission are discussed.