Ionospheric influence on the seismo-telluric current related to electromagnetic signals observed before the Wenchuan &amp;lt;i&amp;gt;M&amp;lt;/i&amp;gt;&amp;lt;sub&amp;gt;&amp;lt;i&amp;gt;S&amp;lt;/i&amp;gt;&amp;lt;/sub&amp;gt; 8.0 earthquake
Solid earth