Weatherwatch: Taming the aurora

Conspiracy theorists have long claimed that the High-Frequency Active Auroral Research Program (HAARP) is used to manipulate the weather. Starting this year, they are right. The US Defence Advanced Research Project Agency's plans for the coming year include "Test active control of ionospheric geomagnetic substorm evolution process."

These substorms are not the sort that involve wind and rain, but are closely related to the northern lights, far above what we usually think of as weather.

The main instrument at HAARP is an array of a hundred and eighty antennae spread over thirty-three hectares near Gakona, Alaska like a gigantic art installation. They can project radio energy into the ionosphere, 80 to 600 kilometres above us. This will tweak disturbances called substorms which occur several times a day in the upper atmosphere. The project goes by the appetising name of Basic Research on Ionospheric Characteristics and Effects, or BRIOCHE.

Substorms make the aurora borealis dance with sudden brightenings and rapid movement; without them the aurora would be a lifeless, static display. Researchers believe substorms occur when Earth's magnetic field lines snap back after being stretched into space.

Manipulating substorms is not just about cosmic light shows. Radio emissions from auroras interfere with some radar and radio systems, including those used for communicating with submarines. HAARP may be able to reduce this interference, or modulate it, turning the ionosphere into a giant radio transmitter sending signals across vast distances.