Aurora

While there is virtually no water vapour, and hence convective clouds or thunderstorms, there are huge geomagnetic storms which are manifested in the visible aurora. Centred on the northern and southern polar regions, auroral substorms may deposit up to a million Megawatts of power producing large currents and stirring up the upper atmosphere.

The source of auroral energy is the solar wind, a persistent stream of charged particles emitted by the sun, which is highly variable in strength. The charged particles are then guided and accelerated by the magnetic field of the earth, in much the same way as the picture tube in your TV guides and accelerates electrons onto your TV screen.

Displays vary greatly, from faint quiet arcs reaching from horizon to horizon, to active displays of colour and movement, seen dancing and cartwheeling across the skies.

Aurora virtually fill the night skies as seen here with romantic tent lights on one of Gina's dog sled trips in the White Mountains, north of Fairbanks, Alaska.

Known as the Aurora Borealis in the northern hemisphere and Aurora Australis in the southern hemisphere, mirror images of the aurora produce crowns of light encircling both poles simultaneously. In our studies of the polar upper atmosphere, auroral activity must be monitored and considered.