Image courtesy NASA Published July 15, 2010 The space weather
report for Mercury: stormy, with a chance of power surges. New
data from the third and final flyby of the MESSENGER (MErcury
Surface, Space ENvironment, GEochemistry, and Ranging)
spacecraft have revealed surprisingly intense electromagnetic
storms in Mercury's magnetic "tail," part of the planet's
magnetic field. Such tails form when the solar wind—charged
particles streaming from the sun—pushes on a planet's magnetic
field. The deformed field flows around the planet in a windsock
shape, like river water flowing around a rock. All eight planets
in the solar system except Mars and Venus have magnetic fields
and tails, although Mercury's field is the smallest and weakest.
But during a September 29, 2009, flyby of the tiny planet,
MESSENGER watched as Mercury's magnetic tail collected enormous
amounts of energy from the solar wind. In just 90 seconds, the
tail increased magnetic field power by 200 percent during an
event known as a magnetic substorm.