Friday, April 17, 2015

Living With a Star - a vast range of scales

Life on Earth would be extremely difficult, if not impossible, if our planet were not positioned very precisely in the habitable zone in our solar system, colloquially known as the “Goldilocks zone”. However, even positioned at this optimum distance from the Sun, the behaviour of our star has profound consequences for our lives. ‘Living with a Star’ is a challenge for a civilisation that has deployed technologies such as satellites and power grid systems that are vulnerable to particle energy emitted by our Sun. In recent decades, solar-terrestrial physics, the study of the interaction of the Sun with Earth, has been addressing the need to provide Space Weather forecasting to protect such technologies. This endeavour occupies a vast range of scales. The solar system is the largest complex system that mankind can study with in-situ observation. It involves dimensions ranging from the astronomical unit (1 AU = 150,000,000 km, the distance from the Earth to the Sun) to the radius of charged particle motions spiralling around magnetic fields which can be only a few centimetres. On the temporal scale, activity on the Sun varies on the “sunspot cycle” of 11 and 22 years whilst phenomena such as explosive energy events on the Sun and in near-Earth space require study on time scales of seconds.

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