Indexing messages schema question

We use Elasticsearch to index messages in a lot of email groups. For each message, we index the subject and the body (amongst other things), and we use the simple and snowball analyzers on each field. We need to add the author name for each message, and I'm not sure what the best way to do that is. We could just add an author field, and treat it like the subject and body fields. But how would we deal with the scenario where the author changes their name on the site? We'd have to update all the messages by that author with the new name. This doesn't happen often, but it does happen. Is there another way to index authors that would avoid that kind of churn?