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<front>
<journal-meta>
<journal-id journal-id-type="publisher">NPG</journal-id>
<journal-title-group>
<journal-title>Nonlinear Processes in Geophysics</journal-title>
<abbrev-journal-title abbrev-type="publisher">NPG</abbrev-journal-title>
<abbrev-journal-title abbrev-type="nlm-ta">Nonlin. Processes Geophys.</abbrev-journal-title>
</journal-title-group>
<issn pub-type="epub">1607-7946</issn>
<publisher><publisher-name>Copernicus Publications</publisher-name>
<publisher-loc>Göttingen, Germany</publisher-loc>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.5194/npg-19-657-2012</article-id>
<title-group>
<article-title>Multifractal analysis of solar flare indices and their horizontal visibility graphs</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Yu</surname>
<given-names>Z. G.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Anh</surname>
<given-names>V.</given-names>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Eastes</surname>
<given-names>R.</given-names>
</name>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Wang</surname>
<given-names>D.-L.</given-names>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>Hunan Key Laboratory for Computation &amp; Simulation in  Science &amp; Engineering, Xiangtan University,   Hunan 411105, China</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>School of Mathematical Sciences, Queensland University  of Technology, GPO Box 2434, Brisbane, Q4001, Australia</addr-line>
</aff>
<aff id="aff3">
<label>3</label>
<addr-line>Florida Space Institute, University of Central Florida,  Orlando, Florida 32816-2370, USA</addr-line>
</aff>
<pub-date pub-type="epub">
<day>29</day>
<month>11</month>
<year>2012</year>
</pub-date>
<volume>19</volume>
<issue>6</issue>
<fpage>657</fpage>
<lpage>665</lpage>
<permissions>
<copyright-statement>Copyright: &#x000a9; 2012 Z. G. Yu et al.</copyright-statement>
<copyright-year>2012</copyright-year>
<license license-type="open-access">
<license-p>This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit <ext-link ext-link-type="uri"  xlink:href="https://creativecommons.org/licenses/by/3.0/">https://creativecommons.org/licenses/by/3.0/</ext-link></license-p>
</license>
</permissions>
<self-uri xlink:href="https://npg.copernicus.org/articles/19/657/2012/npg-19-657-2012.html">This article is available from https://npg.copernicus.org/articles/19/657/2012/npg-19-657-2012.html</self-uri>
<self-uri xlink:href="https://npg.copernicus.org/articles/19/657/2012/npg-19-657-2012.pdf">The full text article is available as a PDF file from https://npg.copernicus.org/articles/19/657/2012/npg-19-657-2012.pdf</self-uri>
<abstract>
<p>The multifractal properties of the daily solar X-ray brightness,
X&lt;sub&gt;&lt;i&gt;l&lt;/i&gt;&lt;/sub&gt; and X&lt;sub&gt;&lt;i&gt;s&lt;/i&gt;&lt;/sub&gt;, during the period from 1 January 1986 to 31
December 2007 which includes two solar cycles are examined using
the universal multifractal approach and multifractal detrended
fluctuation analysis. Then we convert these time series into
networks using the horizontal visibility graph technique.
Multifractal analysis of the resulting networks is performed using
an algorithm proposed by us. The results from the multifractal
analysis show that multifractality exists in both raw daily time
series of X-ray brightness and their horizontal visibility graphs.
It is also found that the empirical &lt;i&gt;K&lt;/i&gt;(&lt;i&gt;q&lt;/i&gt;) curves of raw time
series can be fitted by the universal multifractal model. The
numerical results on the raw data show that the Solar Cycle 23
 is weaker than the Solar Cycle 22 in multifractality. The values
of &lt;i&gt;h&lt;/i&gt;(2) from multifractal detrended fluctuation analysis for
these time series indicate that they are stationary and
persistent, and the correlations in the time series of Solar Cycle
23 are stronger than those for Solar Cycle 22. Furthermore, the
multifractal scaling for the networks of the time series can
reflect some properties which cannot be picked up by using the
same analysis on the original time series. This suggests a
potentially useful method to explore geophysical data.</p>
</abstract>
<counts><page-count count="9"/></counts>
</article-meta>
</front>
<body/>
<back>
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