Scientists get a better understanding of killer electrons in space

A joint research by ESA, Canadian astronomers and US has helped in having a better understanding of killer electrons.

Paris, July 27 : A joint research by ESA, Canadian astronomers and US has helped in having a better understanding of killer electrons.

'Killer' electrons are highly energetic, negatively charged particles found in near-Earth space. They can critically, and even permanently, damage satellites in orbit, including telecommunication satellites, and pose a hazard to astronauts.

In the aftermath of the recovery phase of a large geomagnetic storm on November 25, 2001, the CARISMA (Canadian Array for Realtime Investigations of Magnetic Activity) magnetometer chain observed a type of Ultra Low Frequency (ULF) electromagnetic wave, well-known for creating killer electrons.

ESA's four Cluster satellites which were located at the boundary of Earth's magnetosphere, called the magnetopause, observed undulations, or disturbances of the magnetopause, at the same frequency as that of Pc5 waves observed from inside the magnetosphere.

Taking into account data from all satellites, Earth-based radars and magnetometers, a team led by Jonathan Rae at the University of Alberta, Canada and Qiugang Zong from the University of Massachusetts, Lowell, USA, were able to reveal the mechanism behind the scenario.

They found that during this event, the velocity of solar wind - a continuous stream of solar particles impacting and shaping Earth's magnetosphere - was measured at approximately 750 km/s, nearly twice its average speed.

The impact of this fast flow of solar particles on Earth's magnetosphere induced the undulations observed by Cluster, said the researchers.

In turn, these undulations drove compressional waves, which propagated inward from the magnetopause towards Earth. Close to the location of the Polar satellite, these compressional waves coupled with Earth's magnetic field lines, making the field lines resonate at the frequency of Pc5 waves, which are able to create killer electrons, they said.

Data from Cluster, which focussed on the aftermath of another geomagnetic storm, which occurred on 31 October 2003, also confirmed that Pc5 waves accelerated electrons. The data also enabled the scientists in quantifying - for the first time, in situ - the velocity reached by the accelerated electrons.

"Earth's magnetosphere is a very large, complex and variable system. This makes the understanding of ULF waves, together with the mechanisms for the energy transfer from space to ground, a very difficult matter," said Philippe Escoubet, ESA's Cluster and Double Star Project Scientist.

"These new results on ULF waves and killer electrons once again highlight the need for simultaneous observations from space and ground. Only with constant monitoring with ground-based instruments can we put data obtained in space into a global context," he added.

ANI