Shocking recipe for making killer electrons revealed

PARIS - ESA’s (European Space Agency’s) Cluster mission has revealed the shocking recipe for making killer electrons, by taking a bunch of fast-moving electrons, placing them in orbit and then hitting them with the shock waves from a solar storm.

Killer electrons are highly energetic particles trapped in Earth’s outer radiation belt, which extends from 12 000 km to 64 000 km above the planet’s surface.

During solar storms, their number grows at least ten times and they can be dislodged, posing a threat to satellites.

As the name suggests, killer electrons are energetic enough to penetrate satellite shielding and cause microscopic lightning strikes.

If these electrical discharges take place in vital components, the satellite can be damaged or even rendered inoperable.

On 7 November 2004, the Sun blasted a solar storm in Earth’s direction. It was composed of an interplanetary shock wave followed by a large magnetic cloud.

Shortly afterwards, the shock wave hit Earth’s protective magnetic bubble, known as the magnetosphere.

The impact induced a wave front propagating inside the magnetosphere at more than 1200 km/s at geostationary orbit (36 000 km altitude) around Earth.

The quantity of energetic electrons in the outer radiation belt started to increase too.

Understanding the origin of the killer electrons has been a focus for space weather researchers.

The data collected by ESA’s cluster mission shows that a two-step process causes the substantial rise of killer electrons.

The initial acceleration is due to the strong shock-related magnetic field compression.

Immediately after the impact of the interplanetary shock, Earth’s magnetic field lines began wobbling at ultra low frequencies (ULF).

In turn, these ULF waves were found to effectively accelerate the seed electrons provided by the first step, to become killer electrons.

Although the analysis has been a long one, the results have been worth the wait. Now astronomers know how killer electrons are accelerated.

“Data from the four Cluster satellites allowed the identification of ULF waves able to accelerate electrons,” said Malcolm Dunlop, Rutherford Appleton Laboratory, Didcot (UK) and co-author of this study.

Thanks to this analysis of Cluster data, if the killer electrons happen to be ejected towards Earth, we now know that they can strike the atmosphere within just 15 minutes.

“These new findings help us to improve the models predicting the radiation environment in which satellites and astronauts operate,” said Philippe Escoubet, ESA’s Cluster mission manager

“With solar activity now ramping up, we expect more of these shocks to impact our magnetosphere over the months and years to come,” he said. (ANI)