[ExI] warm plasma cloak

Damien Broderick thespike at satx.rr.com
Mon Dec 15 07:13:04 UTC 2008


Newswise ­ A detailed analysis of the 
measurements of five different satellites has 
revealed the existence of the warm plasma cloak, 
a new region of the magnetosphere, which is the 
invisible shield of magnetic fields and 
electrically charged particles that surround and 
protect Earth from the onslaught of the solar wind.

The study was conducted by a team of scientists 
headed by Charles “Rick” Chappell, research 
professor of physics and director of the Dyer 
Observatory at Vanderbilt University and 
published this fall in the space physics section 
of the Journal of Geophysical Research.

The northern and southern polar lights – aurora 
borealis and aurora australis – are the only 
parts of the magnetosphere that are visible, but 
it is a critical part of Earth’s space environment.

“Although it is invisible, the magnetosphere has 
an impact on our everyday lives,” Chappell said. 
“For example, solar storms agitate the 
magnetosphere in ways that can induce power 
surges in the electrical grid that trigger black 
outs, interfere with radio transmissions and mess 
up GPS signals. Charged particles in the 
magnetosphere can also damage the electronics in 
satellites and affect the temperature and motion of the upper atmosphere.”

The other regions of the magnetosphere have been 
known for some time. Chappell and his colleagues 
pieced together a “natural cycle of energization” 
that accelerates the low-energy ions that 
originate from Earth’s atmosphere up to the 
higher energy levels characteristic of the 
different regions in the magnetosphere. This 
brought the existence of the new region into focus.

The warm plasma cloak is a tenuous region that 
starts on the night side of the planet and wraps 
around the dayside but then gradually fades away 
on the afternoon side. As a result, it only 
reaches about three-quarters of the way around 
the planet. It is fed by low-energy charged 
particles that are lifted into space over Earth’s 
poles, carried behind the Earth in its magnetic 
tail but then jerked around 180 degrees by a kink 
in the magnetic fields that boosts the particles 
back toward Earth in a region called the plasma sheet.

Chappell and his colleagues – Mathew M. 
Huddleston from Trevecca University, Tom Moore 
and Barbara Giles from the National Aeronautics 
and Space Administration, and Dominique Delcourt 
from the Centre d’etude des Environments 
Terrestre et Planetaires, Observatoire de 
Saint-Maur in France – used satellite 
observations to measure the properties of the 
ions in different locations in the magnetosphere.

An important part of their analysis was a 
computer program developed by Delcourt that can 
predict how ions move in the earth’s magnetic 
field. “These motions are very complicated. Ions 
spiral around in the magnetic field. They bounce 
and drift. A lot of things can happen, but 
Dominic developed a mathematical code that can 
predict where they go,” said Chappell.

When the researchers applied this computer code 
to the satellite observations some patterns 
became clear for the first time. One was the 
prediction of how ions could move upward from the 
ionosphere to form the warm plasma cloak.

“We have recognized all the other regions for a 
long time, but the plasma cloak was a fuzzy thing 
in the background which we didn’t have enough 
information about to make it stand out. When we 
got enough pieces, there it was!” said Chappell.

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