Normally, the Earth's magnetosphere acts as a shield from these harmful particles and protects the environment.
MSN: Solar storms sparked by giant 'magnetic rope,' study finds
Sometimes these plasma clouds are directed at Earth, and can deposit a large amount of energy into the planet's magnetosphere.
MSN: Solar storms sparked by giant 'magnetic rope,' study finds
For the plasma to leak into the magnetosphere is quite an accomplishment.
Understanding exactly what the Geotail does (something to do with measuring the solar wind's interaction with the Earth's magnetosphere) may require a background in heliophysics.
The Geomagnetic pole is the north end of the axis of the geomagnetic field which surrounds the Earth and extends into space as the magnetosphere.
More baffling, at least to physicists, is that sometimes a bit of the plasma manages to break through the magnetic barrier and get inside the magnetosphere.
In 1996 (it took several years to analyse the data) Polar saw some plasma sneak inside the magnetosphere, and Geotail saw the rogue plasma being bounced back toward earth itself.
The same thing happens with the magnetic field lines, which suddenly reconnect, resulting in a hole a few kilometres wide in the armour of the magnetosphere, through which plasma can spill.
After a few fast turns caused by turbulence in the magnetosphere, one piece of plasma finds itself close to another piece that is dragging along a magnetic field with the opposite orientation.
For example, changes in the Sun's activity can send huge amounts of energy towards the Earth which buffet and reconfigure the magnetosphere, causing disruption to communications, power-line failures and even the destruction of satellites.
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There seems to be no way that particles streaming past the earth along magnetic field lines can make a turn, move at right angles to those lines for a bit and end up inside the magnetosphere.
Other activities for Cassini scientists during the extended mission will include monitoring seasons on Titan and Saturn, observing unique ring events - such as the 2009 equinox when the Sun will be in the plane of the rings - and exploring new places within Saturn's magnetic "envelope" - or magnetosphere.
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