WordPress at a glance
action is not described

login_enqueue_scripts action-hook . WP 3.1.0

Enqueue scripts and styles for the login page.

Usage

add_action( 'login_enqueue_scripts', 'action_function_name_5915' );
function action_function_name_5915(){
	// action...
}

Where the hook is called

login_header()
login_enqueue_scripts
wp-login.php 107
do_action( 'login_enqueue_scripts' );

Where the hook is used (in WP core)

Does not used.