July 2, 2013
ESA Researchers Discover Solid Proof Of Plasmapheric Winds
[WATCH VIDEO: Plasma Outflow From Plasmasphere To Magnetosphere]
Lee Rannals for redOrbit.com - Your Universe Online
A study published in the journal Annales Geophysicae provides the first conclusive proof of the existence of plasmaspheric wind. Researchers detected this plasmaspheric wind while analyzing data from the European Space Agency's (ESA) Cluster spacecraft.
"After long scrutiny of the data, there it was, a slow but steady wind, releasing about [2.2 lbs] of plasma every second into the outer magnetosphere: this corresponds to almost [100 tons] every day. It was definitely one of the nicest surprises I've ever had!" said Iannis Dandouras of the Research Institute in Astrophysics and Planetology in Toulouse, France.
The plasmasphere is an area filled with charged particles that takes up the inner part of the Earth's magnetosphere. In order to detect the wind, the team analyzed the properties of these charged particles.
Dandouras had to develop a filtering technique to eliminate noise sources and to look for plasma motion along the radial direction, either directed at the Earth or outer space. The data showed a steady and persistent wind carrying a couple pounds of the plasmasphere's material outwards each second at a speed of over 3,100 miles per hour. This motion was present at all times, even when the Earth's magnetic field was not being distributed by energetic particles coming from the Sun.
The team predicted a space wind with these properties nearly 20 years ago, but direct detection has been eluded until now.
"The plasmaspheric wind is a weak phenomenon, requiring for its detection sensitive instrumentation and detailed measurements of the particles in the plasmasphere and the way they move," explains Dandouras, who is also the vice-president of the EGU Planetary and Solar System Sciences Division.
This wind contributes to the loss of material from the Earth's top atmospheric layer, and is a source of plasma for the outer magnetosphere above it.
"The plasmaspheric wind is an important element in the mass budget of the plasmasphere, and has implications on how long it takes to refill this region after it is eroded following a disturbance of the planet's magnetic field," Dandouras said. "Due to the plasmaspheric wind, supplying plasma -- from the upper atmosphere below it -- to refill the plasmasphere is like pouring matter into a leaky container."
The plasmasphere plays a crucial role in governing the dynamics of the Earth's radiation belts. These present a radiation hazard to satellites and to astronauts traveling through them.
"Understanding the various source and loss mechanisms of plasmaspheric material, and their dependence on the geomagnetic activity conditions, is thus essential for understanding the dynamics of the magnetosphere, and also for understanding the underlying physical mechanisms of some space weather phenomena," says Dandouras.