A patch file for changing Solr's core name in the configuration.

Sitecore.ContentSearch.Solr.CoreNames.config

<?xml version="1.0" encoding="utf-8" ?>
<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/" xmlns:role="http://www.sitecore.net/xmlconfig/role/" xmlns:search="http://www.sitecore.net/xmlconfig/search/">
  <sitecore role:require="Standalone or ContentManagement or ContentDelivery" search:require="Solr">
    <!-- Set your prefix of Solr's core. -->
    <sc.variable name="SolrCorePrefix" value="prefix.of.core" />
    <contentSearch>
      <configuration>
        <indexes>
          <index id="sitecore_core_index">
            <param desc="core">$(SolrCorePrefix)_core_index</param>
          </index>
          <index id="sitecore_fxm_master_index">
            <param desc="core">$(SolrCorePrefix)_fxm_master_index</param>
          </index>
          <index id="sitecore_fxm_web_index">
            <param desc="core">$(SolrCorePrefix)_fxm_web_index</param>
          </index>
          <index id="sitecore_marketing_asset_index_master">
            <param desc="core">$(SolrCorePrefix)_marketing_asset_index_master</param>
          </index>
          <index id="sitecore_marketing_asset_index_web">
            <param desc="core">$(SolrCorePrefix)_marketing_asset_index_web</param>
          </index>
          <index id="sitecore_marketingdefinitions_master">
            <param desc="core">$(SolrCorePrefix)_marketingdefinitions_master</param>
          </index>
          <index id="sitecore_marketingdefinitions_web">
            <param desc="core">$(SolrCorePrefix)_marketingdefinitions_web</param>
          </index>
          <index id="sitecore_master_index">
            <param desc="core">$(SolrCorePrefix)_master_index</param>
          </index>
          <index id="sitecore_suggested_test_index">
            <param desc="core">$(SolrCorePrefix)_suggested_test_index</param>
          </index>
          <index id="sitecore_testing_index">
            <param desc="core">$(SolrCorePrefix)_testing_index</param>
          </index>
          <index id="sitecore_web_index">
            <param desc="core">$(SolrCorePrefix)_web_index</param>
          </index>
          <!-- Enable here if SXA is installed -->
          <!--
          <index id="sitecore_sxa_master_index">
            <param desc="core">$(SolrCorePrefix)_sxa_master_index</param>
          </index>
          <index id="sitecore_sxa_web_index">
            <param desc="core">$(SolrCorePrefix)_sxa_web_index</param>
          </index>
          -->
        </indexes>
      </configuration>
    </contentSearch>
  </sitecore>
</configuration>