WordPress at a glance
action is not described

auth_redirect action-hook . WP 2.8.0

Fires before the authentication redirect.

Usage

add_action( 'auth_redirect', 'action_function_name_9834' );
function action_function_name_9834( $user_id ){
	// action...
}
$user_id(int)
User ID.

Where the hook is called

auth_redirect()
auth_redirect
wp-includes/pluggable.php 1043
do_action( 'auth_redirect', $user_id );

Where the hook is used (in WP core)

Does not used.