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<article language="en">
	<journal>
		<journal_title>Nonlinear Processes  in Geophysics</journal_title>
		<journal_url>www.nonlin-processes-geophys.net</journal_url>
		<issn>1023-5809</issn>
		<eissn>1607-7946</eissn>
		<volume_number>16</volume_number>
		<issue_number>1</issue_number>
		<publication_year>2009</publication_year>
	</journal>
	<doi>10.5194/npg-16-99-2009</doi>
	<article_url>http://www.nonlin-processes-geophys.net/16/99/2009/</article_url>
	<abstract_html>http://www.nonlin-processes-geophys.net/16/99/2009/npg-16-99-2009.html</abstract_html>
	<fulltext_pdf>http://www.nonlin-processes-geophys.net/16/99/2009/npg-16-99-2009.pdf</fulltext_pdf>
	<start_page>99</start_page>
	<end_page>110</end_page>
	<publication_date>2009-02-17</publication_date>
	<article_title content_type="html">Accurate estimation of third-order moments from turbulence measurements</article_title>
	<authors>
		<author numeration="1" affiliations="1">
			<name>J. J. Podesta</name>
			<email>jpodesta@solar.stanford.edu</email>
		</author>
		<author numeration="2" affiliations="2">
			<name>M. A. Forman</name>
		</author>
		<author numeration="3" affiliations="1">
			<name>C. W. Smith</name>
		</author>
		<author numeration="4" affiliations="3">
			<name>D. C. Elton</name>
		</author>
		<author numeration="5" affiliations="4">
			<name>Y. Malécot</name>
		</author>
		<author numeration="6" affiliations="5">
			<name>Y. Gagne</name>
		</author>
	</authors>
	<affiliations>
		<affiliation numeration="1" content_type="html">Space Science Center, University of New Hampshire, Durham, New Hampshire, 03824, USA</affiliation>
		<affiliation numeration="2" content_type="html">Department of Physics and Astronomy, State University of New York, Stony Brook, New York, 11794, USA</affiliation>
		<affiliation numeration="3" content_type="html">Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, Troy, New York, 12180, USA</affiliation>
		<affiliation numeration="4" content_type="html">University Joseph Fourier – Grenoble I, BP 53, 38041 Grenoble Cedex 9, France</affiliation>
		<affiliation numeration="5" content_type="html">Laboratoire des  Ecoulements Géophysiques et Industriels, CNRS/UJF/INPG UMR 5519 BP53, 38041 Grenoble, France</affiliation>
	</affiliations>
	<abstract content_type="html">Politano and Pouquet&apos;s law, a generalization of Kolmogorov&apos;s four-fifths law
to incompressible MHD, makes it possible to measure the energy cascade rate in
incompressible MHD turbulence by means of third-order moments.  In hydrodynamics,
accurate measurement of third-order moments requires large amounts of data because
the probability distributions of velocity-differences are nearly symmetric and the
third-order moments are relatively small.  Measurements of the energy cascade
rate in solar wind turbulence have recently been performed for the first time, but without
careful consideration of the accuracy or statistical uncertainty of the required
third-order moments.  This paper investigates the statistical convergence
of third-order moments as a function of the sample size &lt;i&gt;N&lt;/i&gt;.
It is shown that the accuracy of the third-moment &amp;lt;(&amp;delta; v&lt;sub&gt;||&lt;/sub&gt;)&lt;sup&gt;3&lt;/sup&gt;&amp;gt;
depends on the number of correlation lengths spanned by the data set and a method of
estimating the statistical uncertainty  of the third-moment is developed.
The technique is illustrated using  both wind tunnel data and solar wind data.</abstract>
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</article>

