The default solution for sorting results in Squirro is currently sorting by relevance.
Sorting by Relevance
The results of a given query are sorted by relevance score. Relevance score is computed based on some factors like term frequency, document frequency, where the querying terms matched in the document (body, title, summary...). The downside of sorting purely by relevance can be ignores the important of up-to-date content such as news articles. See Combined Time and Relevance Sorting for more details