Error in installing ionic on Ubuntu 15.10

Hello, I am a new in ionic need your help. I have a problem with the installation.
here is the command sudo apt-get install -g ionic
here is :
npm ERR! 404 Not Found
npm ERR! 404
npm ERR! 404 ‘ionic/app-generators’ is not in the npm registry.
npm ERR! 404 You should bug the author to publish it
npm ERR! 404 It was specified as a dependency of 'ionic’
npm ERR! 404
npm ERR! 404 Note that you can also install from a
npm ERR! 404 tarball, folder, or http url, or git url.

npm ERR! System Linux 4.2.0-16-generic
npm ERR! command “/usr/bin/nodejs” “/usr/bin/npm” “install” “-g” "ionic"
npm ERR! cwd /usr/share/npm/bin
npm ERR! node -v v0.10.25
npm ERR! npm -v 1.4.21
npm ERR! code E404
npm ERR!
npm ERR! Additional logging details can be found in:
npm ERR! /usr/share/npm/bin/npm-debug.log
npm ERR! not ok code 0

thank.