WordPress at a glance
action is not described

set_current_user action-hook . WP 2.0.1

Fires after the current user is set.

Usage

add_action( 'set_current_user', 'action_function_name_1727' );
function action_function_name_1727(){
	// action...
}

Where the hook is called

wp_set_current_user()
set_current_user
wp-includes/pluggable.php 47
do_action( 'set_current_user' );

Where the hook is used (in WP core)

wp-includes/default-filters.php 475
add_action( 'set_current_user', 'kses_init' );