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<front>
<journal-meta>
<journal-id journal-id-type="publisher">ANGEO</journal-id>
<journal-title-group>
<journal-title>Annales Geophysicae</journal-title>
<abbrev-journal-title abbrev-type="publisher">ANGEO</abbrev-journal-title>
<abbrev-journal-title abbrev-type="nlm-ta">Ann. Geophys.</abbrev-journal-title>
</journal-title-group>
<issn pub-type="epub">1432-0576</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/angeo-29-1005-2011</article-id>
<title-group>
<article-title>The correlation between solar and geomagnetic activity – Part 3: An integral response model</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Du</surname>
<given-names>Z. L.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China</addr-line>
</aff>
<pub-date pub-type="epub">
<day>15</day>
<month>06</month>
<year>2011</year>
</pub-date>
<volume>29</volume>
<issue>6</issue>
<fpage>1005</fpage>
<lpage>1018</lpage>
<permissions>
<copyright-statement>Copyright: &#x000a9; 2011 Z. L. Du</copyright-statement>
<copyright-year>2011</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://angeo.copernicus.org/articles/29/1005/2011/angeo-29-1005-2011.html">This article is available from https://angeo.copernicus.org/articles/29/1005/2011/angeo-29-1005-2011.html</self-uri>
<self-uri xlink:href="https://angeo.copernicus.org/articles/29/1005/2011/angeo-29-1005-2011.pdf">The full text article is available as a PDF file from https://angeo.copernicus.org/articles/29/1005/2011/angeo-29-1005-2011.pdf</self-uri>
<abstract>
<p>An integral response model is proposed to describe the
relationship between geomagnetic activity (&lt;I&gt;aa&lt;/I&gt; index) and solar
activity (represented by sunspot number &lt;I&gt;R&lt;/I&gt;&lt;sub&gt;z&lt;/sub&gt;): The &lt;I&gt;aa&lt;/I&gt;
at a given time &lt;I&gt;t&lt;/I&gt; is the integral of &lt;I&gt;R&lt;/I&gt;&lt;sub&gt;z&lt;/sub&gt; at past
times (&lt;I&gt;t&lt;/I&gt;&apos;&amp;leq;&lt;I&gt;t&lt;/I&gt;) multiplied by an exponential decay factor of the
time differences (&lt;I&gt;e&lt;sup&gt;&amp;minus;(t&amp;minus;t&apos;)/&amp;tau;&lt;/sup&gt;&lt;/I&gt;), where τ  is the decay
time scale (~40 months). The correlation coefficient of &lt;I&gt;aa&lt;/I&gt;
with the reconstructed series based on this model
(&lt;I&gt;r&lt;/I&gt;&lt;sub&gt;f&lt;/sub&gt;=0.85) is much higher than that of &lt;I&gt;aa&lt;/I&gt; with
&lt;I&gt;R&lt;/I&gt;&lt;sub&gt;z&lt;/sub&gt; (&lt;I&gt;r&lt;/I&gt;&lt;sub&gt;0&lt;/sub&gt;=0.61). If this model is applied to each
solar cycle, the correlation coefficient will be higher
(&lt;I&gt;r&lt;/I&gt;&lt;sub&gt;f&lt;/sub&gt;=0.95). This model can naturally explain some
phenomena related to &lt;I&gt;aa&lt;/I&gt; and &lt;I&gt;R&lt;/I&gt;&lt;sub&gt;z&lt;/sub&gt;, such as (i) the
significant increase in the &lt;I&gt;aa&lt;/I&gt; index (and its baseline) over the
twentieth century; (ii) the longer lag times of &lt;I&gt;aa&lt;/I&gt; to
&lt;I&gt;R&lt;/I&gt;&lt;sub&gt;z&lt;/sub&gt; at solar cycle maxima than at minima; and (iii) the
variations in the correlations related to solar and Hale cycles.
These results demonstrate that &lt;I&gt;aa&lt;/I&gt; depends not only on the
present &lt;I&gt;R&lt;/I&gt;&lt;sub&gt;z&lt;/sub&gt; but also on past values. The profile of
&lt;I&gt;aa&lt;/I&gt; can be better predicted from &lt;I&gt;R&lt;/I&gt;&lt;sub&gt;z&lt;/sub&gt; by this model
than by point-point correspondence.</p>
</abstract>
<counts><page-count count="14"/></counts>
</article-meta>
</front>
<body/>
<back>
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