About every 11 to 13 years the sun’s magnetic poles swap places and the sun shows high levels of activity. Large sunspots form, and there is an increase in coronal mass ejections (CMEs) — the gusts of energy that react with Earth’s magnetic field to cause auroras. The period during which the sun reaches its peak in activity is known as solar maximum. This is set to occur in 2013.

Earth’s magnetic poles move around. The southern magnetic pole is currently tilted towards Australia, making Tasmania one of the best places in the southern hemisphere to view auroras.

The best time of year to view auroras is during the winter months, because longer nights mean there is a better chance of a CME reaching Earth during hours of darkness. However, winter months also bring the problem of clouds, which can obscure displays.

Aurora displays are generally best viewed on moonless nights, away from light pollution. When photographing an aurora, however, a full moon can sometimes be a blessing in disguise, as with this photo, in which a scene shrouded in darkness has been illuminated by the full moon.

The long exposure technique used to capture these star trails and the aurora over Betsy Island in south-eastern Tasmania also causes the aurora’s normal green colour to take on a yellow hue in the resulting photograph. Although digital cameras have made photographing displays much easier, capturing true colour is still a challenge.

Aurora displays have two main colours visible to the human eye – green and red. As electrons enter the Earth’s atmosphere they collide with gas particles, which glow different colours when stimulated by the collision.

Rare blue aurora displays can occur at altitudes below 100km, when electrons from very powerful solar storms interact with nitrogen molecules.

The curls in this aurora seen over Howden, in southern Tasmania, show the interaction between currents in the upper atmosphere and the Earth’s magnetic field.

Weak auroras can’t always be seen by the naked eye, however a camera detects low levels of aurora activity which can alert watchers that an aurora may be building.

Generally the best views of aurora activity are to the south. This photo was taken from a popular surfing, fishing and aurora-watching spot near Hobart.

Each aurora display is different. Often all that is visible is a hazy glow towards the southern horizon, but more spectacular displays may include fast-moving curtains, beams, shimmering and strobes.

Auroral displays vary in intensity according to the power of the CME that causes them. Some CMEs are strong enough to disrupt power grids and interfere with radio communications.

After the peak of the solar cycle, solar activity will gradually decrease until solar minimum. This occurs when solar activity is at its lowest, and large auroras are rare during this time. After solar minimum, solar activity will start to increase again and the sun will build towards the next solar maximum in 11 to 13 years time.