In particular, the researchers want to know how some atoms from the Earth's atmosphere manage to escape into space.

The interaction of the solar wind and other particles from space with the Earth's magnetic field produces beautiful auroras but can also cause major electrical problems for orbiting satellites and even on Earth. In 1989, a major solar storm caused electricity blackouts across Canada and north-eastern USA.

Critical timing

The rocket is transported to the launch pad in the Arctic winter gloom

New instruments will be launched in an arcing flight path, peaking 1400km (840 miles) above the Earth's surface. The timing of the launch is critical as aurora can come and go rapidly. On Tuesday, the first countdown was abandoned due to "poor scientific conditions"

"Aurora are very difficult targets to shoot," comments Professor Philip Williams, a physicist at the University of Wales Aberystwyth, talking to BBC News Online. "But rockets can take in-situ measurements, complementing radar and other remote techniques."

A spacecraft called Polar is keeping watch for ideal auroral conditions and the next attempt will be on Wednesday between 0400 and 0900 GMT. A Black Brant XII sounding rocket will be used at the Andøya Rocket Range in northern Norway, a facility of the Norwegian Space Centre.

Secure magnetic barrier

Caper (Cleft Accelerated Plasma Experimental Rocket) will take sophisticated instruments into the region above the magnetic pole where the Earth's atmosphere is exposed to the influence of space particles. Elsewhere, the Earth's magnetic field provides a secure barrier.

"It's the only place where solar wind particles can directly enter the Earth's atmosphere," said Dr Victoria Coffey of Nasa's Marshall Space Flight Centre, who is responsible for some of Caper's instruments.

Ions from the atmosphere can be lost to space

One puzzling aspect of aurora is how ions from the atmosphere can accelerate to speeds of one kilometre per second upwards and escape the Earth. "How do these particles defy gravity?" asks Dr Coffey.

"The whole problem with aurora is how charged particles are accelerated," agrees Professor Williams, who has a colleague assisting at Caper's launch. "If Caper can measure both the magnetic field and the ions and electrons present at the same time, that would give very useful information."

Most ions are lost after coronal mass ejections. These are huge eruptions of plasma from the sun which can have dire consequences for electrical equipment around the Earth.

Important research

Professor Williams thinks the research is important for two reasons. Firstly, particle acceleration occurs in many astronomical situations, quasars for example, but aurora allow them to be studied near to Earth.

Secondly, "the storm which caused a lot of damage to satellites at the start of 1998 cost more than all the money ever spent on research in this field. But the costs mean that space weather will have to become a serious subject.