WordPress at a glance
filter is not described

the_author_(field) filter-hook . WP 2.8.0

The value of the requested user metadata.

The filter name is dynamic and depends on the $field parameter of the function.

Usage

add_filter( 'the_author_(field)', 'filter_function_name_3223', 10, 2 );
function filter_function_name_3223( $author_meta, $user_id ){
	// filter...

	return $author_meta;
}
$author_meta(string)
The value of the metadata.
$user_id(int)
The user ID.

Where the hook is called

the_author_meta()
wp-includes/author-template.php 208
echo apply_filters( "the_author_{$field}", $author_meta, $user_id );

Where the hook is used (in WP core)

Does not used.