The night-walkers of Uganda

Key words
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Find the information
2
Look in the text and find this information as quickly as possible.
1. How many spacecraft are NASA sending into space?
2. How high is the magnetic field above the Earth?
3. How many ground stations will track the satellites?
4. What colour is nitrogen in the magnetic field?
5. What is the other name for the northern lights?
6. Where can you see the northern lights? 
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Into the aurora: NASA craft probe 
mysteries of the northern lights
Project will help predict damaging space storms.
Satellites will line up in orbit to measure effect. 
Alok Jha, science correspondent
February 15, 2007
Above the Arctic Circle a bright pink light often 
appears in the night sky. This is called the northern 
lights (or aurora borealis). Sometimes it seems 
that the sun is rising in the wrong place. Colours of 
pink, red, green and violet fill the sky. Where does 
this strange light come from? Magnetic storms in 
space send out energy particles. These particles hit 
the Earth’s atmosphere and produce the coloured 
light. For scientists the lights are one of the oldest 
mysteries in space physics: how and where in 
space do these light shows begin? And how can 
scientists predict when and where they will happen? 
Now the North American Space Agency (NASA) 
is sending five spacecraft into space to try to 
answer these questions. This project, known as 
the Themis project, will measure how the magnetic 
field around the Earth changes in real time. This will 
allow scientists to make better forecasts about the 
weather in space. This information is important for 
the safety of communications satellites as they orbit 
the Earth and will also be very important for human 
space travellers. 
The northern lights are the result of changes in 
the Earth’s magnetic field. The sun continually 
sends energy towards our planet. The Earth’s 
magnetic field stores some of this energy at a 
height of 10,000 km above the surface of the 
Earth. The magnetic field protects us from much 
of the deadly radiation that comes from the 
sun. However, sometimes energy escapes from 
the field and showers of electrons rise into the 
upper atmosphere. When these electrons come 
into contact with air, they create the energy that 
produces the light of the northern lights.
The different colours are the result of the different 
gases in the atmosphere at 10,000km above the 
Earth. Green and red are oxygen and violet is 
nitrogen. Most of the time, the northern lights are a 
wide band of light from east to west but every few 
hours the energy causes a storm. 
“It is interesting when a storm starts – the light 
gets brighter and then, within 30 seconds, it starts 
moving quickly towards the north. It covers the 
whole sky and then breaks up into little pieces,” said 
Vassilis Angelopoulos, a scientist working on the 
Themis project. “It’s wonderful to watch.” No-one 
knows exactly why and where the storms begin. 
“The problem so far is that using just one satellite 
we cannot be sure where the storms begin,” said 
Professor Angelopoulos. 
The five satellites will orbit the Earth in a line and 
record the energy passing from the sun to the 
Earth. They will be in different places in the Earth’s 
magnetic field and will record when and where an 
energy storm begins between two of the satellites. 
More than 20 ground stations across the US will 
track the Themis satellites, and will record exactly 
where the magnetic storms happen. 
“In the same way that meteorologists study 
tornadoes in order to understand the large 
thunderstorms, we study magnetic storms to 
understand large space storms,” said Professor 
Angelopoulos. If scientists can forecast when these 
large storms will happen, spacecraft and astronauts 
will be able to operate safely, because the storms 
can damage electronic systems on spacecraft. 
At the moment the forecasting of space storms is 
not reliable. “It’s like what weather forecasting was 
a hundred years ago. In the last 50 years, weather 
forecasting has improved a lot because they 
understand exactly what happens. We are doing 
the same kind of thing. We are trying to give people 
better forecasts of space storms,” says UK space 
expert Mike Hapgood.
The Themis satellites will take their first 
measurements next year. They will operate for 
two years. Dr Hapgood says that understanding 
the Earth’s magnetic field will also give scientists 
information about other planets in the solar 
system that have magnetic fields: “These things 
also happen in other parts of the universe. 
Understanding how magnetic fields work is a 
universal question.”