Aurora at St Andrews
A spectacular display of the ‘Northern Lights’ was captured in St Andrews last night (Thursday 20th November 2003) by Thomas Robitaille, an undergraduate student of Astrophysics at the University.
Professor Keith Horne, Head of Astronomy at the University’s School of Physics and Astronomy made the following observations:
“The Sun is a star, a gigantic nuclear furnace that generates energy at its centre by fusing hydrogen into helium. That energy takes a million years to percolate up to the Sun’s surface. The hot surface radiates light that takes 8 minutes to reach Earth, where it heats and illuminates our world.
“Not all of the energy emerges as light, however. Some of it is stored in bubbles of magnetic field that remain attached to the Sun’s surface. Eventually, the magnetic fields snap, releasing the stored energy, and flinging a burst of charged particles out into space. Such events are called solar flares.
“When we see a large solar flare, we can expect a strong Aurora to occur a few days later, when the burst of charged particles reaches the Earth. The Earth’s magnetic field captures some of the charged particles, guiding them down magnetic field lines onto the north and south polar regions.
“When the streams of charged particles moving down the Earth’s magnetic field lines hit the atmosphere, about 60 kilometres up, they collide with air molecules, mainly nitrogen and oxygen, exciting them and causing them to emit the eerie red and green lights that we see as an Aurora.
“The streaks of light you see in the sky during an Aurora reveal the otherwise invisible magnetic field lines down which the particles are streaming. These are the same field lines that pull on the magnetic needle of a compass to make it point North.”
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