Displaying categories alphabetically

I’m developing a wordpress site (blog.thirstforfiction.com), and one of the essential things is that I can display the subcategories of a category alphabetically. Currently, I can display the subcategories using this code:

<?php if (is_category()) {
  $this_category = get_category($cat);
  if (get_category_children($this_category->cat_ID) != "") {
    echo "<h2>Subcategories</h2>";
    echo "<ul>";
    wp_list_categories('orderby=id&show_count=0&title_li=
&use_desc_for_title=1&child_of='.$this_category->cat_ID);
    echo "</ul>";
  }
}
?>

But I don’t know how to display the results alphabetically. I’ve tried various tutorials, but my PHP knowledge is incredibly shallow.

Anyone know how to edit the above code to display results alphabetically?

PS: It’s specifically https://blog.thirstforfiction.com/authors that I want this for.

Thanks.