Northern lights is a common name for the aurora borealis, a natural light display in the sky of the Earth's Arctic regions, caused by the collision of energetic charged particles with atoms in the Earth's thermosphere.
During her career as a hypnotist, The Contessa discovered a a way to control people through the use of light-waves. Arpeggio learned of this ability when she joined the Klaww Gang, and thought it would be a suitable way of hypnotizing the citizens of Paris (once they had consumed Illegal Spice) to create enough hatred to spark his immortality. The only problem Arpeggio faced, however, was finding an source for the light-waves.
Arpeggio eventually found the northern lights to be a plentiful source of light-waves and tasked Jean Bison with gathering energy from the lights. Bison used the lighthouse located at his lumber camp as an attractor of the northern lights' energy. The collected energy was stored in giant batteries and shipped to Arpeggio.
A few days before Arpeggio was due to collect the final batch of northern light energy from Bison, the Cooper Gang arrived at the lumber camp, drained the battery storing the energy, and prevented it from being refilled by destroying the attractor. With the battery empty, they would be able to stow away inside it and get onto Arpeggio's Blimp. Arpeggio soon came and picked up the battery, but unbeknownst to him, it was devoid of northern light energy, and instead carried the Cooper Gang.
In spite of not getting the energy, it was apparently not needed, as Arpeggio's hypnosis light show was set to commence anyway.