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Dynamical age of solar wind turbulence in the outer heliosphere

Authors :
William H. Matthaeus
Sean Oughton
Charles W. Smith
Source :
Journal of Geophysical Research: Space Physics. 103:6495-6502
Publication Year :
1998
Publisher :
American Geophysical Union (AGU), 1998.

Abstract

In an evolving turbulent medium, a natural timescale can be defined in terms of the energy decay time. The time evolution may be complicated by other effects such as energy supply due to driving, and spatial inhomogeneity. In the solar wind the turbulence appears not to be simply engaging in free decay, but rather the energy level observed at a particular position in the hellosphere is affected by expansion, "mixing," and driving by stream shear. Here we discuss a new approach for estimating the "age" of solar wind turbulence as a function of heliocentric distance, using the local turbulent decay rate as the natural dock, but taking into account expansion and driving effects. The simplified formalism presented here is appropriate to low cross hellcity (non-Alfvnic) turbulence in the outer hellosphere especially at low hello-latitudes. We employ Voyager data to illustrate our method, which improves upon the familiar estimates in terms of local eddy turnover times.

Details

ISSN :
01480227
Volume :
103
Database :
OpenAIRE
Journal :
Journal of Geophysical Research: Space Physics
Accession number :
edsair.doi...........8eaa30c5ec9b710737e853d804da26d3
Full Text :
https://doi.org/10.1029/97ja03729