Although the Sun is a benevolent provider of warmth and comfort, it also has a very angry side. Solar outbursts cause inclement space weather that sometimes wrecks havoc on technological systems on which our society is progressively more dependent. In a plenary talk at the Royal Astronomical Society National Astronomy Meeting in Preston, Dr James Klimchuk of the Naval Research Laboratory in the USA presented the latest results from the STEREO and Hinode spacecraft, two missions that have been studying the Sun for the last few months.
STEREO is a NASA-led mission with substantial participation by scientists from the UK and other European countries. It consists of two spacecraft watching the Sun from different vantage points, that will eventually allow astronomers look at the whole of the region between the Sun and the Earth for the first time and eventually allow them to construct 3D images of the Sun. Hinode is a Japanese mission with collaboration from scientists in the US and UK. It orbits the Earth in a path that gives the probe a continuous view of the Sun.
One of the key objectives of the two missions is to study solar outbursts. These involve the sudden release of energy stored in the magnetic fields of the corona, the hot material that makes up the outer atmosphere of the Sun. The smallest events or nanoflares heat the corona to a temperature of millions of degrees and cause the emission of X-ray and ultra-violet radiation that changes the upper atmosphere of the Earth. The largest Coronal Mass Ejections (CMEs) are spectacular and can cause storms in the Earth's magnetic field.
Together, STEREO and Hinode give astronomers the ability to watch CMEs all the way from the Sun to the Earth. Scientists can watch their evolution as they interact with the outflow of particles from the Sun (the solar wind) en-route to our planet. CMEs are the most dramatic 'space weather' events and can cause damage to technological systems such as power grids and communication and navigation networks. The severity of the impact of a CME depends on how it changes as it makes the journey across the inner Solar system and the new missions allow astronomers to better understand how these outbursts evolve.
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