Magnetic Powerhouse

17 Jul 2010

At ... a flyby of Mercury revealed a huge power surge that 'we clearly do not understand' according to the story. The electromagnetic storms took place in Mercury's magnetic tail, and this forms when the solar wind pushes against a planet's magnetic field and the deformed field takes on a windsock shape. It says Mars and Venus do NOT have magnetic fields or tails - is this true? Besides that query, which requires a response by somebody, we learn that the Messenger spacecraft flew past Mercury in September 2009, and the paper comes after its images had been studied in the period between then and now. The magnetic tail was seen to collect enormous amounts of energy from the solar wind - and after a short time the tail snapped back to normal, dissipating the sudden burst of energy. On earth, tail loading, as it has been dubbed, takes an hour and results in an increase in the magnetic field of around 10 per cent. Messenger is due to settle into a stable orbit around Mercury in 2011 - but we may note that tail loading on earth is responsible for aurorae.

Meanwhile, at July 16th there is a story on the ESA Cluster mission, which involves four satellites that have been studying the sun-earth relationship for the last 10 years, particularly how the solar wind (charged particles or plasma) reacts with earth's magnetic bubble, the magnetosphere. Cluster has confirmed that black aurorae seem to be 'anti-aurora' that suck electrons out of the ionosphere. One of the big puzzles found by Cluster is 'reconnection' - which takes place when magnetic fields collide, release energy, and allow separated plasma, or electrified gas, to mix. At the centre of this is a null point - and at the point of 'reconnection' the magnetic field is twisted into a 500 km wide tube. Understanding reconnection is a major quest of physics as it is associated with solar flaring.